Search

Under the background of high permeability, voltage feedforward control may further weaken the stability of grid-connected inverter (GCI) systems and may cause sub-synchronous oscillation in extreme cases. To solve this problem, this paper firstly considers the influence of the frequency coupling effect and voltage feedforward control, and adopts the harmonic linearization method to construct the L-type GCI sequence admittance model with PI (proportional integral) control and PR (proportional resonant) control, respectively. By comparing the sequence admittance characteristics of the GCI under two control strategies, combined with the sequence admittance model and Nyquist criterion, this paper analyzes the influence of voltage feedforward and control parameters on the stability of the GCI under two control strategies. The results show that the stability of GCI under PR control is slightly better than that under PI control. At the same time, the voltage feedforward control does reduce the stability of the GCI system under the two control strategies. Finally, the accuracy of the theoretical analysis is verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

As the proportion of renewable energy generation continues to rise, the study of voltage source converter (VSC) control has become a focal point of research. The concepts of emulating the characteristics of synchronous machines have led to the proposals of droop control and virtual synchronous control (VSG). However, a deeper comparison of the control characteristics of these two methods is still needed, particularly in terms of their ability to support the system when partial power sources experience fault conditions. This paper analyzes and compares the two in terms of control principles and small-signal modeling, and finally, based on a nine-bus system with 100% renewable energy generation, two scenarios are designed: a sudden load increase and a partial power source disconnection. The differences in control characteristics between the two are compared and analyzed. The results indicate that the VSG exhibits greater damping compared to droop control and is capable of providing inertial support to the system, making its frequency and voltage less susceptible to change.

Aiming at large system operation fluctuations caused by the technical control of virtual synchronous generators, this article studies the introduction of interface converter control power, builds a virtual synchronous generator (VSG)‐based hybrid microgrid model and adaptive control strategy. Finally it optimizes it with fuzzy logic to obtain an fuzzy logic controller (FLC) based adaptive VSG control strategy. The experimental results show that under the FLC‐based adaptive VSG control strategy, in the reverse current mode, the system regression time is 0.37 s, and the DC bus voltage is 6.5 V; In the rectification mode, the system regression time is 0.49 s, and the DC bus voltage is 2.1 V. The results obtained are faster than the traditional VSG control strategy, and the DC bus voltage is 42.48%–68.66% lower. In summary, the suggested control approach is effective and reliable under the two operation modes, which can make the system operate safely and stably. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhengzhou University: Engineering Science is the property of Editorial Office of Journal of Zhengzhou University: Engineering Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Under the background of high permeability, voltage feedforward control may further weaken the stability of grid-connected inverter (GCI) systems and may cause sub-synchronous oscillation in extreme cases. To solve this problem, this paper firstly considers the influence of the frequency coupling effect and voltage feedforward control, and adopts the harmonic linearization method to construct the L-type GCI sequence admittance model with PI (proportional integral) control and PR (proportional resonant) control, respectively. By comparing the sequence admittance characteristics of the GCI under two control strategies, combined with the sequence admittance model and Nyquist criterion, this paper analyzes the influence of voltage feedforward and control parameters on the stability of the GCI under two control strategies. The results show that the stability of GCI under PR control is slightly better than that under PI control. At the same time, the voltage feedforward control does reduce the stability of the GCI system under the two control strategies. Finally, the accuracy of the theoretical analysis is verified by simulation and experiment.

Introduction: Virtual Synchronous Generators (VSGs) are used in Voltage Source Converter-based Multi-Terminal High-Voltage Direct Current (VSC-MTDC) systems to enhance power system stability. However, the MTDC framework can lead to instability due to reduced inertia in certain grid areas, especially during load switching at VSC stations. This instability is exacerbated by untimely adjustments of the VSG's power setpoint, leading to voltage and frequency oscillations. Methods: This study introduces a cooperative control approach for the DC voltage of the VSG, employing a consensus algorithm and Model Predictive Control (MPC). This method aims to achieve incremental power for the VSG and provide interactive power commands for both the grid side and the wind farm side. The consensus algorithm ensures coherent system adjustments, while the MPC algorithm tracks DC-side voltage changes in real time. Results: The application of this cooperative control approach significantly enhances DC voltage regulation performance. It effectively reduces the extent of frequency drops and mitigates secondary frequency drop (SFD) issues, particularly those arising from the use of wind farms for frequency regulation and the associated speed recovery in wind turbine units. Discussion: The increase in supplemental power effectively utilizes the energy stored in DC-side capacitors for power balance regulation and introduces additional inertial power into the system. Electromagnetic transient simulations have confirmed the effectiveness of the Consensus MPC-VSG method, demonstrating its ability to optimize the dynamic performance of VSC-MTDC systems and promote stability in DC voltage and frequency. Conclusion: The findings suggest that employing the Consensus MPC-VSG method offers a promising solution for enhancing the stability and operational efficiency of VSC-MTDC systems, addressing the challenges posed by the inherent segmentation of the grid and the integration of renewable energy sources like wind farms. [ABSTRACT FROM AUTHOR]

Transient stability and frequency stability of virtual synchronous generator (VSG)-controlled converters during grid faults are critical for the stable operation of high-share renewable energy power systems. However, the existing transient stability methods often overlook the consideration of frequency stability. This paper presents a method to improve both frequency stability and transient stability of VSGs during grid faults. The influence mechanism of inertia and damping on transient stability and frequency stability is comprehensively analyzed under two types of faults, with or without stable equilibrium points. To address the conflict between frequency stability and transient stability of VSGs with large inertia under the first type of fault, an improved VSG control with angular frequency deviation feedback is proposed. The transient response of this control method is analyzed using small-signal and large-signal models. Furthermore, to achieve optimal dynamic performance, this improved VSG control introduces the optimal damping ratio and presents a parameter design method. Finally, the correctness of the proposed method and its theoretical analysis is verified through experimental results. [ABSTRACT FROM AUTHOR]

In the modular multilevel converter based multi-terminal DC (MMC-MTDC) system, the virtual synchronous generator (VSG) control cannot take into account the problem of DC voltage fluctuation regulation when maintaining the frequency stability of the AC grid. The U 2 -P DC voltage droop control was introduced into the VSG controller for the receiving-end converter in the MMC-MTDC system, and the VSG control with additional DC voltage was obtained. This control can not only realize the frequency adjustment in the AC region, but also control the DC voltage. By analyzing the influence of moment of inertia in VSG on the frequency response of AC grid, an adaptive virtual moment of inertia adjustment method based on fuzzy control was designed on the basis of additional DC voltage VSG control. By flexibly adjusting the virtual inertia, the converter shows smoother and faster dynamic response performance in the process of supporting frequency fluctuation. The effectiveness of the proposed strategy is verified on the MATLAB/ Simulink simulation platform, which shows that the proposed strategy can adjust the frequency and DC voltage at the same time and can show better frequency dynamic response performance. [ABSTRACT FROM AUTHOR]

A virtual synchronous generator (VSG) strategy can introduce the rotational inertia and damping characteristics of the synchronous generator to the static inverter, e.g., PV, wind generation, and ESS, which are used to enhance the system frequency support characteristics of the micro-grid. However, under various operations of the VSG, the inertia and damping support capabilities are different, and the conventional VSG strategy with a fixed control coefficient sacrifices a certain degree of dynamic regulation performance with less robustness. This research proposes an improved VSG strategy with adaptive inertia and damping coefficients to increase the flexibility of VSG. To this end, a mathematical model is first established to analyze the impact of various parameters on the characteristics of VSG, and then the root trajectory is used to explore the impacts of various rotational inertia and damping coefficients on the stability ofthe VSG system. Second, an improved control strategy with adaptive inertia and damping coefficients is proposed based on the characteristics of the second- order system and the system frequency deviations. Finally, a simulation system with the VSG is constructed based on MATLAB/Simulink. The effectiveness of the proposed control strategy is verified by comparing the simulation results to the conventional control strategy with the fixed control coefficients under over- frequency and under-frequency disturbances. [ABSTRACT FROM AUTHOR]

In response to the inability of the flexible DC transmission system connected to the AC grid under conventional control strategies to provide inertia to the system as well as to participate in frequency regulation, a virtual synchronous generator (VSG) control strategy is proposed for a voltage source converter (VSC)-based multi-terminal high-voltage direct current (VSC-MTDC) interconnection system. First, the virtual controller module is designed by coupling AC frequency and active power through virtual inertia control, so that the VSC-MTDC system can provide inertia response for AC grid frequency. Second, by introducing the power margin of the converter station into the droop coefficient, the unbalanced power on the DC side is reasonably allocated to reduce the overshoot of the DC voltage in the regulation process. Finally, the power regulation capability of the normal AC system is used to provide power support to the fault end system, reducing frequency deviations and enabling inter-regional resource complementation. The simulation model of the three-terminal flexible DC grid is built in PSCAD/EMTDC, and the effectiveness of the proposed control strategy is verified by comparing the conventional control strategy and the additional frequency control strategy.

The “3060” plan fully demonstrates the determination of China’s economic and social green and clean development. As an important secondary energy source, hydrogen has the advantages of high energy density, green and pollution-free, etc. As an ideal energy source in the future, green hydrogen is the final state of hydrogen energy prepared by electrical energy through electrolysis of water. The development of renewable energy hydrogen production will certainly help to achieve the goal of carbon peaking and carbon neutral. Therefore, the grid-connected control strategy of hydrogen production unit for weak grid is worthy of in-depth study. The research work in this paper is as follows: firstly, based on the analysis of the converter, a grid-connected control method of electric hydrogen production unit using virtual synchronization generator(VSG) control strategy is proposed. Secondly, a control method without phase-locked loop is adopted for the grid-connected phase synchronization part. Then, the stability of the proposed control strategy is demonstrated by using root locus plot. Finally, experimental verification is carried out. The experimental results show that the proposed control strategy makes the hydrogen production unit friendly to the weak grid with good adaptability, and at the same time, as a load, it can perform adaptive power regulation very well.

Virtual Synchronous Generator (VSG)-based grid-forming converters (GFC) increasingly serve as interfaces between renewable energy resources and the power grids with high penetration. Although the emulation of the characteristics of Synchronous Generator (SG) enables GFC to provide virtual inertia and oscillation damping under the VSG control, it remains challenging to replicate the short-circuit behaviors of SGs under the grid voltage sag/recovery conditions. The existing technologies are limited and lack full functionalities in terms of power synchronization, overcurrent suppression and capability of dealing with asymmetric grid-faults. This paper presents a Virtual Impedance Voltage Control (VIVC) strategy to enhance the fault-ride-through capability of the converter under a variety of fault conditions. In the case of asymmetric faults, a negative-sequence current control is performed to mitigate the negative-sequence voltages and achieve the grid current balance. The fault current is restrained and the power synchronization is improved by the virtual reactance without oversizing the GFC. The simulation and experimental results validate the effectiveness of the proposed control strategies.

With the high ratio of distributed generation (DG) linked to power system via converters, power system stability is degraded in terms of inertia and damping. In recent years, the virtual synchronous generator (VSG) has become a potential solving method to deal with these issues. However, the power coupling problem exists in the traditional VSG control method, which severely impacts the VSG power control performance. The impedance characteristics of the transmission line are closely related to the effect of the power decoupling control of VSGs. To solve the voltage sag and poor robustness issues resulting from traditional virtual impedance control, a virtual complex impedance power decoupling and sharing control strategy for VSGs based on coordinate transformation is proposed. Combining the characteristics of traditional virtual impedance control and virtual power control, the power coupling mechanism in parallel VSGs caused by line impedance is analyzed. The virtual complex impedance control loop is introduced in VSG control to realize the matching of the equivalent line impedance and the precise decoupling of VSG power output. Then the load can be accurately allocated in the light of the proportion of VSG capacity.

Introduction: Virtual Synchronous Generators (VSGs) are used in Voltage Source Converter-based Multi-Terminal High-Voltage Direct Current (VSC-MTDC) systems to enhance power system stability. However, the MTDC framework can lead to instability due to reduced inertia in certain grid areas, especially during load switching at VSC stations. This instability is exacerbated by untimely adjustments of the VSG's power setpoint, leading to voltage and frequency oscillations.Methods: This study introduces a cooperative control approach for the DC voltage of the VSG, employing a consensus algorithm and Model Predictive Control (MPC). This method aims to achieve incremental power for the VSG and provide interactive power commands for both the grid side and the wind farm side. The consensus algorithm ensures coherent system adjustments, while the MPC algorithm tracks DC-side voltage changes in real time.Results: The application of this cooperative control approach significantly enhances DC voltage regulation performance. It effectively reduces the extent of frequency drops and mitigates secondary frequency drop (SFD) issues, particularly those arising from the use of wind farms for frequency regulation and the associated speed recovery in wind turbine units.Discussion: The increase in supplemental power effectively utilizes the energy stored in DC-side capacitors for power balance regulation and introduces additional inertial power into the system. Electromagnetic transient simulations have confirmed the effectiveness of the Consensus MPC-VSG method, demonstrating its ability to optimize the dynamic performance of VSC-MTDC systems and promote stability in DC voltage and frequency.Conclusion: The findings suggest that employing the Consensus MPC-VSG method offers a promising solution for enhancing the stability and operational efficiency of VSC-MTDC systems, addressing the challenges posed by the inherent segmentation of the grid and the integration of renewable energy sources like wind farms.

The traditional microgrid electric energy system exhibits low damping and low inertia, making it susceptible to load fluctuations that can significantly impact the system. A new study suggests a way to control a microgrid virtual synchronous generator (VSG) using adaptive regulation of rotational inertia. This lowers the frequency steady-state offset of the VSG control system’s output by using a non-differential frequency regulation method. The virtual excitation regulator regulates the output voltage deviation. Meanwhile, we establish a small-signal model of the grid-connected inverter based on VSG control and explore the effects of rotational inertia and damping coefficient on the stability of the VSG. The MATLAB/Simulink simulation tool is used to simulate the microgrid differential power load mutation, and the effects of the VSG control and the traditional control strategy on several aspects of the system, such as frequency regulation, power regulation, and power quality, are analyzed by comparison. The findings show that the suggested adaptive control method lowers the voltage amplitude from ±25V to ±10V when the system is isolated, stops power fluctuations, and makes the output response curve as good as it can be. Under grid-connected conditions, the VSG adaptive control method still ensures better control performance, but it does not show a significant advantage in this experimental condition.

A virtual synchronous generator (VSG) strategy can introduce the rotational inertia and damping characteristics of the synchronous generator to the static inverter, e.g., PV, wind generation, and ESS, which are used to enhance the system frequency support characteristics of the micro-grid. However, under various operations of the VSG, the inertia and damping support capabilities are different, and the conventional VSG strategy with a fixed control coefficient sacrifices a certain degree of dynamic regulation performance with less robustness. This research proposes an improved VSG strategy with adaptive inertia and damping coefficients to increase the flexibility of VSG. To this end, a mathematical model is first established to analyze the impact of various parameters on the characteristics of VSG, and then the root trajectory is used to explore the impacts of various rotational inertia and damping coefficients on the stability of the VSG system. Second, an improved control strategy with adaptive inertia and damping coefficients is proposed based on the characteristics of the second-order system and the system frequency deviations. Finally, a simulation system with the VSG is constructed based on MATLAB/Simulink. The effectiveness of the proposed control strategy is verified by comparing the simulation results to the conventional control strategy with the fixed control coefficients under over-frequency and under-frequency disturbances.

Unlike Synchronous Generators (SGs), Virtual Synchronous Generators (VSGs) inertia is not fixed once it is manufactured and only has an upper limit defined by its energy storage components. In this paper, a novel Enhanced Virtual Inertia Controller (EVIC) is proposed. The proposed controller alters the VSG inertia coefficient between two limiting levels in response to a grid transient. The key difference between the proposed controller and the variable inertia controller is that the proposed EVIC causes a smooth transition in the inertia coefficient while the variable inertia controller causes a discontinuous jump in it. The proposed EVIC guarantees an adaptive response to grid dynamics, such that a negligible change occurs at small disturbances and a linear and smooth increase occurs at moderate disturbances. For large disturbances, the proposed controller smoothly oscillates the inertia between two saturation levels, which then quickly returns the converter to its steady-state operating point with minimum oscillations. A qualitative study of the performance and stability margin of the proposed controller was conducted using a large signal model (nonlinear model) of VSG connected to a microgrid. The large signal model provided a complete description of the converter's behaviour under large disturbances, which is the area of interest of the proposed controller. It also contained the small-signal dynamics (linear dynamic) within the vicinity of the equilibrium (steady-state) point. Thus, a complete description of the proposed controller dynamics is conveyed to prove its validity and adaptability. [ABSTRACT FROM AUTHOR]

At present, the direct drive permanent magnet synchronous generator (DD-PMSG) grid connected system based on virtual synchronous generator (VSG) control will experience power oscillation at sub synchronous frequencies. The mechanism and characteristics of this new type of sub-synchronous interaction (SSI) are not yet clear, and the system cannot recover to steady state solely based on the characteristics of VSG itself. Especially when connected to a weak current network, oscillations are more pronounced, affecting the stability of the system. In severe cases, the system may trigger shutdown protection and be disconnected from the network. Existing research has only analyzed the oscillation mechanism under this phenomenon and has not proposed corresponding control strategies. This article proposes a VSM control strategy based on the VSG control algorithm, which balances the dq axis component of voltage and current, and improves the voltage and current loop of VSG control to reduce the impact of sub-synchronous oscillation (SSO) on the power grid. In MATLAB/Simulink, a simulation model of the proposed control strategy was built to verify its correctness and effectiveness. [ABSTRACT FROM AUTHOR]

Objective: To describe alcohol use, alcohol-related harm, and alcohol-related problems preoperatively and up to 8 years following metabolic and bariatric surgery (MBS) in adolescents. Background: Risk for alcohol use and alcohol use disorders (AUD) increases post-Roux-en-Y gastric bypass and vertical sleeve gastrectomy in adults. However, data are lacking in adolescents who undergo MBS. Methods: This study includes 217 adolescents (aged 13–19 y) enrolled in a 5-center prospective cohort study who underwent Roux-en-Y gastric bypass or vertical sleeve gastrectomy (2007–2011) and reported alcohol use preoperatively and annually postoperatively for up to 8 years. Time to elevated Alcohol Use Disorder Identification Test-Consumption (AUDIT-C) score, alcohol-related harm, and alcohol-related problems were analyzed with Kaplan-Meier estimates of cumulative incidence. Results: Preoperatively, the median age was 17 years; the median body mass index was 51 kg/m2. Alcohol use frequency and average quantity of drinks per drinking day increased postoperatively (2% consumed alcohol 2–4 times/month 6 months versus 24% 8 years postoperatively, P <0.001; 2% consumed≥3 drinks per drinking day 6 months versus 35% 8 years postoperatively, P <0.001). Cumulative incidence of postoperative onset elevated AUDIT-C score, alcohol-related harm, and alcohol-related problems at year 8 were 45% (95% CI:37–53), 43% (95% CI:36–51), and 47% (95% CI:40–55), respectively. Conclusions: Nearly half of those who underwent MBS as adolescents screened positively for AUD, symptoms of alcohol-related harm, or alcohol-related problems 8 years post-MBS, highlighting the risk for alcohol use and AUD after MBS in adolescents. AUD evaluation and treatment should be integrated into routine long-term care for adolescents undergoing MBS. [ABSTRACT FROM AUTHOR]

The proportion of distributed generation systems in power grids is increasing, leading to the gradual emergence of weak grid characteristics. Moreover, using voltage-sourced grid-connected inverters can enhance the stability of a weak grid. However, due to the presence of background harmonics in weak grids, the grid voltage can cause significant distortions in the grid-connected current, which adversely affects the quality of the grid-connected current. This paper begins by briefly introducing the principle of the virtual synchronous generator (VSG). Then, the output current of the voltage source inverter is analyzed to elucidate the mechanism of harmonic current generation. Considering the distortion in the grid-connected current of the voltage source grid-connected inverter caused by background harmonics in the grid voltage, a harmonic current suppression strategy based on an adaptive virtual harmonic resistor is proposed. The proposed strategy employs a signal separation module based on multiple second-order generalized integrators connected through a cross-feedback network. This module effectively separates the fundamental and harmonic currents from the grid-connected current, extracts the amplitudes of the fundamental and harmonic currents through coordinate transformation, and adaptively adjusts the virtual harmonic resistance magnitude through the negative feedback control of the harmonic content (the ratio of the harmonic current amplitude to the fundamental current amplitude). These measures are used to enhance the quality of the grid-connected current. Additionally, the stability of the system is analyzed using the root locus of the open-loop transfer function. Finally, the effectiveness of the proposed method is validated through a combination of MATLAB/Simulink simulations and experimental results. [ABSTRACT FROM AUTHOR]

The constant increase of energy demand and the widespread adoption of renewable energy sources have led to the significant interest in micro-grids, which are small-scale power systems that utilize distributed energy resources. However, micro-grids face synchronization challenges in terms of stability and reliability, and virtual synchronous generator technology has become the key to addressing this issue. This study focuses on the pre synchronization control strategy of virtual synchronous generators in micro-grids, aiming to solve the potential surge current problem that virtual synchronous generators may generate when switching from off grid mode to grid connected mode through innovative methods. This strategy employs a phase difference acquisition method that eliminates the need for a phase-locked loop. It calculates virtual power by utilizing the output voltage of the virtual synchronous generator and the grid side voltage, and obtains the phase difference through calculation. The resulting phase difference is then used as input for the frequency phase synchronization unit in pre-synchronization. By adjusting the diagonal frequency, the phase difference $\Delta \theta $ can be modified to achieve pre-synchronization before connecting the virtual synchronous generator to the power grid. This method notably reduces the dependence on the phase-locked loop and enhances the stability and reliability of the system. The paper has effectively solved the synchronization problem of virtual synchronous generators in micro-grids through innovative pre synchronization control strategies and improved secondary frequency regulation strategies. It is hoped that these research results will provide new ideas and methods for the further development and application of micro-grid technology.

The virtual synchronous generator (VSG), as a grid-connected technology, has gain more and more attention because of its unique merits including its ability to reshape inertia and damping. These merits enable renewable energy to be smoothly integrated into the grid. Unbalance between three-phase voltage in the steady state is a common phenomenon in the grid, which distorts the output current of the VSG. However, on many occasions, inserting symmetrical current into the grid is necessary. To solve this problem, a dual-module VSG control strategy is proposed in this paper. Through this strategy, the positive and negative sequence output powers of the VSG can be correctly identified and separately controlled. Then the output current can be kept symmetrical by controlling the negative sequence output power of the VSG to be zero. Finally, the proposed strategy is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

For the pre-synchronization method of the virtual synchronous generator (VSG), only the case of a single VSG pre-synchronization and grid connection has been studied and analyzed. If the phase synchronization of multiparallel VSGs in a decentralized microgrid is realized by controlling a VSG, power circulation exists in the pre-synchronization process. Firstly, the structure and control mode of the microgrid are introduced. For the decentralized structure, a control mode switching mechanism under distributed communication is designed, and a pre-synchronization method of parallel VSGs based on control mode switching is proposed. Secondly, a theoretical analysis of the active power circulation problem is performed by an equivalent frequency model for parallel VSGs in the pre-synchronization process. Finally, the simulation results show that the proposed pre-synchronization method can reduce the dynamic power circulation of parallel VSGs by 83%, and improve the pre-synchronization speed by 75%. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ObjectiveTo determine whether vertical sleeve gastrectomy (VSG) attenuates fibrosis in mice on a high-fat high-cholesterol (HFHC) diet.BackgroundBariatric surgery mitigates non-alcoholic steatohepatitis in 85-90% of obese patients. While animal models demonstrate similar results on a high-fat diet, none have observed the effects of bariatric surgery on a combined HFHC diet.MethodsMice on a HFHC diet were used to confirm the development of hepatic fibrosis at 8 (n = 15) and 24 (n = 15) weeks. A separate cohort of mice on a HFHC diet for 12 weeks was subjected to either VSG (n = 18) or sham (n = 12) operations and remained on a HFHC diet for an additional 20 weeks. Changes in weight, dyslipidemia, and the development of steatosis and fibrosis were documented. Serum was obtained for bile acid analysis by liquid chromatography and mass spectrometry, while hepatic gene expression by RT-PCR was performed to evaluate intrahepatic lipid metabolism.ResultsHepatic steatosis and fibrosis developed after 8 weeks on the HFHC diet. After VSG, mice demonstrated a sustained decrease in weight with a significant decrease in fibrosis compared to sham mice. Serum total cholesterol, HDL, and LDL were significantly reduced following surgery, while serum bile acids were significantly elevated. Intra-hepatic cholesterol excretion was not upregulated based on hepatic gene expression of CYP7A1 and ABCG5/8.ConclusionsVSG attenuates the development of hepatic fibrosis in diet-induced obese mice, presumably through enhancement of cholesterol elimination at the intestinal level.

BACKGROUND AND AIMS: Bariatric surgery, such as vertical sleeve gastrectomy (VSG), is the most effective long-term treatment for obesity. However, there are conflicting reports on the effect of bariatric surgery on inflammatory bowel disease (IBD). Bariatric surgery increases bile acid concentrations, which can decrease inflammation by signaling through the bile acid receptor, TGR5. TGR5 signaling protects against chemically induced colitis in mice. VSG increases circulating bile acid concentrations to increase TGR5 signaling, which contributes to improved metabolic regulation after VSG. Therefore, we investigated the effect of VSG on chemically induced colitis development and the role of TGR5 in this context. METHODS: VSG or sham surgery was performed in high fat diet-fed male Tgr5+/+ and Tgr5-/- littermates. Sham-operated mice were food restricted to match their body weight to VSG-operated mice. Colitis was induced with 2.5% dextran sodium sulfate (DSS) in water post-operatively. Body weight, energy intake, fecal scoring, colon histopathology, colonic markers of inflammation, goblet cell counts, and colonic microRNA-21 levels were assessed. RESULTS: VSG decreased body weight independently of genotype. Consistent with previous work, genetic ablation of TGR5 increased the severity of DSS-induced colitis. Notably, despite the effect of VSG to decrease body weight and increase TGR5 signaling, VSG increased the severity of DSS-induced colitis. VSG-induced increases in colitis were associated with increased colonic expression of TNF-α, IL-6, MCP-1, and microRNA-21. CONCLUSIONS: While our data demonstrate that TGR5 protects against colitis, they also demonstrate that VSG potentiates chemically induced colitis in mice. These data suggest that individuals undergoing VSG may be at increased risk for developing colitis; however, further study is needed.

With the high penetration of renewable energy, new challenges, such as power fluctuation suppression and inertial support capability, have arisen in the power sector. Battery energy storage systems play an essential role in renewable energy integration. In this paper, a distributed virtual synchronous generator (VSG) control method for a battery energy storage system (BESS) with a cascaded H-bridge converter in a grid-connected mode is proposed. The VSG is developed without communication dependence, and state-of-charge (SOC) balancing control is achieved using the distributed average algorithm. Owing to the low varying speed of SOC, the bandwidth of the distributed communication networks is extremely slow, which decreases the cost. Therefore, the proposed method can simultaneously provide inertial support and accurate SOC balancing. The stability is also proved using root locus analysis. Finally, simulations under different conditions are carried out to verify the effectiveness of the proposed method.

• Prediction of water quality based on Gaussian process regression with limited samples is studied. • Three virtual sample generation (VSG) methods, MD-MTD, GAN, and t-SNE, were compared. • manifold feature extraction and Gaussian process regression based virtual sample generation is proposed. • Interpolation and random forest are combined to generate virtual samples. • Successful improvement of Sr2+ Prediction Accuracy in a Shallow Aquifer System in Songyuan City, Jilin Province, China. The increasing pollution of aquifers by human activities over recent decades poses a threat to drinking water safety. While Gaussian Process Regression (GPR) is a robust tool for predicting and monitoring water quality, its effectiveness is hindered limitations of available data on model training and validation, known as the "small sample problem". Various attempts to resolve this problem include virtual sample generation (VSG). This study aimed to increase the accuracy of GPR for predicting water quality in situations of limited datasets. Three VSG methods, namely Multi Distribution Mega-Trend Diffusion (MD-MTD), Generative Adversarial Network (GAN), and t-distributed stochastic nearest neighbor embedding (t-SNE) were compared for enhancing the accuracy of GPR model prediction of Strontium (Sr2+). The models were used to predict Sr2+ in the shallow aquifer system in Songyuan, Jilin Province. The results showed that t-SNE provided the most significant improvement to the accuracy of the GPR, with R2 increasing from 0.86 to 0.99 (12.98 %), followed by MD-MTD (R2 of 0.95, 9.39 %), with the least improvement obtained by GAN (R2 of 0.92, 5.98 %). Boxplots show that MD-MTD-GPR predictions do not fully capture observed data distributions. GANs accurately replicate the data distribution, while t-SNE-GPR achieves the highest prediction accuracy and handles data fluctuations. GPR accuracy improves with an increasing number of virtual samples but tends to decrease when the number exceeds 258 in this study. This study can guide the improvement of the accuracy of GPR for situations of limited datasets. The results of this study can help improve water quality management and drinking water safety in regions with sparse monitoring data. [ABSTRACT FROM AUTHOR]

Unlike Synchronous Generators (SGs), Virtual Synchronous Generators (VSGs) inertia is not fixed once it is manufactured and only has an upper limit defined by its energy storage components. In this paper, a novel Enhanced Virtual Inertia Controller (EVIC) is proposed. The proposed controller alters the VSG inertia coefficient between two limiting levels in response to a grid transient. The key difference between the proposed controller and the variable inertia controller is that the proposed EVIC causes a smooth transition in the inertia coefficient while the variable inertia controller causes a discontinuous jump in it. The proposed EVIC guarantees an adaptive response to grid dynamics, such that a negligible change occurs at small disturbances and a linear and smooth increase occurs at moderate disturbances. For large disturbances, the proposed controller smoothly oscillates the inertia between two saturation levels, which then quickly returns the converter to its steady-state operating point with minimum oscillations. A qualitative study of the performance and stability margin of the proposed controller was conducted using a large signal model (nonlinear model) of VSG connected to a microgrid. The large signal model provided a complete description of the converter’s behaviour under large disturbances, which is the area of interest of the proposed controller. It also contained the small-signal dynamics (linear dynamic) within the vicinity of the equilibrium (steady-state) point. Thus, a complete description of the proposed controller dynamics is conveyed to prove its validity and adaptability.

With the increase of photovoltaic penetration, the power-electronic converter (PEC)-interfaced generators with traditional control strategy may cause severe power oscillations after being disturbed due to lack of inertia and damping. The photovoltaic power plant controlled by virtual synchronous generator (VSG) technology, while introducing virtual inertia and virtual damping to improve the stability of the system, will also inherit its oscillation characteristics and cause a new oscillation mode. Aiming at this problem, this paper analyzes the difference between the system low-frequency oscillation (LFO) modes before and after the VSG is connected to the two-area system by the modal analysis. It is pointed out that the PEC-interfaced renewable energy generators based on VSG control technology could change the oscillation mode of the original system. The influence of VSG's main parameters and capacity on system dynamics is analyzed. Finally, a synchrophasor-based inter-area oscillation suppressed comprehensive control strategy is proposed to suppress the LFO of active power on the tie line, and the superiority of the strategy is verified by DIgSILENT /PowerFactory. [ABSTRACT FROM AUTHOR]

The proportion of distributed generation systems in power grids is increasing, leading to the gradual emergence of weak grid characteristics. Moreover, using voltage-sourced grid-connected inverters can enhance the stability of a weak grid. However, due to the presence of background harmonics in weak grids, the grid voltage can cause significant distortions in the grid-connected current, which adversely affects the quality of the grid-connected current. This paper begins by briefly introducing the principle of the virtual synchronous generator (VSG). Then, the output current of the voltage source inverter is analyzed to elucidate the mechanism of harmonic current generation. Considering the distortion in the grid-connected current of the voltage source grid-connected inverter caused by background harmonics in the grid voltage, a harmonic current suppression strategy based on an adaptive virtual harmonic resistor is proposed. The proposed strategy employs a signal separation module based on multiple second-order generalized integrators connected through a cross-feedback network. This module effectively separates the fundamental and harmonic currents from the grid-connected current, extracts the amplitudes of the fundamental and harmonic currents through coordinate transformation, and adaptively adjusts the virtual harmonic resistance magnitude through the negative feedback control of the harmonic content (the ratio of the harmonic current amplitude to the fundamental current amplitude). These measures are used to enhance the quality of the grid-connected current. Additionally, the stability of the system is analyzed using the root locus of the open-loop transfer function. Finally, the effectiveness of the proposed method is validated through a combination of MATLAB/Simulink simulations and experimental results.

Virtual synchronous generator (VSG)-based control approaches for AC machine drivers have attracted much attention in recent years. The contradiction between the strong motor loading capacity and the small DC voltage fluctuation is disregarded in previous studies. A larger virtual inertia is required to raise the torque gain and drive the motor with heavier loads, thus resulting in greater DC voltage variations. A systematic method is proposed for the optimal design of the virtual inertia for VSG-based motor starting systems to achieve the maximal motor loading capacity and the low DC voltage fluctuation in this paper. Firstly, the relationship between the virtual inertia and the loading capacity is revealed on the basis of the closed-loop analysis. Considering the DC voltage variation, the constraint on the maximal value of the virtual inertia is proposed from the energy-balance perspective despite the unknown contribution of the DC capacitors to the virtual inertia. To fully exploit the energy storage capacity of the DC capacitors and raise the upper limit of the virtual inertia under the same permitted DC voltage variation, a modified DC voltage reference is introduced. Extensive simulation and experimental results are presented to validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

To improve the connection efficiency to grid of distributed power sources, and solve the problems of insufficient damping and inertia in inverter grid connection, an inverter control method was investigated to realize traditional synchronous generator's function, which was named as virtual synchronous generator (VSG) technology. Based on the role of phase locked loop (PLL) in virtual synchronous generator, the pre-synchronization control method was proposed based on virtual power. The secondary frequency modulation and the secondary voltage regulation functions were simulated in the power loop. The output value compensated the loss of active power and reactive power through inertia link, and the control parameters were flexibly adjusted according to power levels. Regarding the voltage and current on the VSG generator side, the PR control method was used to increase the constraint on the electrical value for preventing grid connection failure. The topology structure and the mathematical model of VSG were analyzed, and the improved control method of VSG was given. A corresponding simulation model was established to verify VSG control effect from two aspects of pre-synchronous grid-connection and grid connection stability under mutation load. The results show that the improved VSG control can reduce the complexity of grid-connected inverter and the oscillation frequency of output power and suppress the current impact on the grid side, which makes the inverter follow the dynamic change process of power grid at all time. [ABSTRACT FROM AUTHOR]

• Wideband harmonic mitigation. • No need to extract harmonic components. • Simple controller implementation. • Can be applied to other microgrid control, such as Droop control. In virtual synchronous generator (VSG)-based islanded microgrid, voltage harmonics induced by nonlinear loads seriously degrade system power quality. Existing harmonic mitigation controllers mainly rely on the extracted harmonic components to control, and generally have the weakness that can only mitigate harmonics with known frequencies. To better improve the power quality of the islanded microgrid, a wideband harmonic self-mitigation controller (WHSMC) is proposed in this paper, which can effectively mitigate wideband voltage harmonics above the fundamental frequency without extracting harmonics. Firstly, based on the impedance method, the reason why nonlinear loads will cause voltage harmonics in the islanded microgrid is analyzed in detail. Secondly, by establishing the impedance model of VSG with the proposed WHSMC, the mechanism how the proposed WHSMC mitigates voltage harmonics without knowing the harmonic frequency in advance is theoretically revealed. Finally, the effectiveness of the proposed WHSMC is verified through simulation and experimental results. The experiments indicate that the voltage total harmonic distortion (THD) can decrease from 7.02 % to 3.41 % under nonlinear load disturbance and from 8.27 % to 3.99 % under pulse load disturbance. [Display omitted] [ABSTRACT FROM AUTHOR]

Grid-Tied Converters (GTCs) serve a vital role in integrating renewable energy generation into power networks with high penetration rates. During a grid voltage sag or recovery, the existing LVRT technologies still suffer from overcurrent caused by fault detection delay under the control of the Virtual Synchronous Generator (VSG). This vulnerability may result in trip-off occurrences or damage to the power electronic components. At present, VSG-related research mainly focuses on control and stability analysis, etc. There is a relative lack of work on the fault current-voltage (I-V) characteristics of VSG during grid voltage dips, which is urgently needed. Due to this indistinct nonlinear characteristics, the grid-forming GTC either loses the voltage source characteristics of the VSG or deteriorates the transient stability against deep asymmetrical grid dips. As a result, the conventional solutions provide limited assurance of transient stability and inadequate management of asymmetric grid disturbances. The analysis in this paper begins with a dimensional examination of the I-V characteristics of the VSG (IV-VSG) during grid contingencies. Subsequently, this research presents an improved control strategy for increasing the LVRT capability of GTCs under different grid-fault circumstances. Additionally, a rigorous analysis of transient stability is performed to uphold the synchronization between the VSG and the grid during severe grid disturbances. Both the simulation and experimental verification demonstrate that fault currents are restricted at a rapid rate, power synchronization is maintained and the need for an enlarged GTC and current limiting strategies are eliminated. In addition, the transient stability of the VSG is validated under a variety of fault conditions. • A novel low-voltage ride-through (LVRT) control scheme is proposed to fully comply with the grid codes. • The LVRT strategy effectively restricts the fault currents while simultaneously maintaining the characteristics of the VSG. • The transient stability is rigorously analysed to ensure the synchronism under a severe grid voltage dip. • Sophisticated gain tuning, specific fault-current limiter or additional control is not required for the implementation. [ABSTRACT FROM AUTHOR]

For the pre-synchronization method of the virtual synchronous generator (VSG), only the case of a single VSG pre-synchronization and grid connection has been studied and analyzed. If the phase synchronization of multiparallel VSGs in a decentralized microgrid is realized by controlling a VSG, power circulation exists in the pre-synchronization process. Firstly, the structure and control mode of the microgrid are introduced. For the decentralized structure, a control mode switching mechanism under distributed communication is designed, and a pre-synchronization method of parallel VSGs based on control mode switching is proposed. Secondly, a theoretical analysis of the active power circulation problem is performed by an equivalent frequency model for parallel VSGs in the pre-synchronization process. Finally, the simulation results show that the proposed pre-synchronization method can reduce the dynamic power circulation of parallel VSGs by 83%, and improve the pre-synchronization speed by 75%.

In recent years, virtual synchronous generator (VSG) control algorithm has been widely studied in distributed grid-connected power inverters to deal with active and reactive power adjustment by simulating the operation principle of the actual synchronous generator. Nevertheless, once the current sensor fails, the grid-connected power inverter will lose its stability. To enhance the fault-tolerant operation ability of the grid-connected power inverter, a new inverter side current sensor-less model predictive control method based on sliding mode observer (SMO) is proposed. The stability of the SMO is analyzed by using the Lyapunov stability criterion. The gains of the SMO are then designed by analyzing their influences on the current and voltage observation based on the closed-loop transfer functions. Besides, to show the influences of the capacitance changes on the current observation, a detailed parameter sensitivity analysis is also carried out. Then, by using the estimated inductance current from the SMO, a current sensor-less model predictive control method is finally proposed. The main novelty of the proposed method is that both the output voltage of the inverter and the inverter side inductance are not required in the proposed SMO. So, the accuracy of current sensor-less control is improved. To verify the effectiveness of the proposed method, detailed experimental studies are carried out based on a Typhoon and PE-Expert 4 based experimental platform.

ABSTRACT In the mammalian host, Trypanosoma brucei is coated in a single-variant surface glycoprotein (VSG) species. Stochastic switching of the expressed VSG allows the parasite to escape detection by the host immune system. DNA double-strand breaks (DSB) trigger VSG switching, and repair via gene conversion results in an antigenically distinct VSG being expressed from the single active bloodstream-form expression site (BES). The single active BES is marked by VSG exclusion 2 (VEX2) protein. Here, we have disrupted monoallelic VSG expression by stably expressing a second telomeric VSG from a ribosomal locus. We found that cells expressing two VSGs contained one VEX2 focus that was significantly larger in size than the wild-type cells; this therefore suggests the ectopic VSG is expressed from the same nuclear position as the active BES. Unexpectedly, we report that in the double VSG-expressing cells, the DNA sequence of the ectopic copy is lost following a DSB in the active BES, despite it being spatially separated in the genome. The loss of the ectopic VSG is dependent on active transcription and does not disrupt the number or variety of templates used to repair a BES DSB and elicit a VSG switch. We propose that there are stringent mechanisms within the cell to reinforce monoallelic expression during antigenic variation. IMPORTANCE The single-cell parasite Trypanosoma brucei causes the fatal disease human African trypanosomiasis and is able to colonize the blood, fat, skin, and central nervous system. Trypanosomes survive in the mammalian host owing to a dense protective protein coat that consists of a single-variant surface glycoprotein species. Stochastic switching of one VSG for an immunologically distinct one enables the parasite to escape recognition by the host immune system. We have disrupted monoallelic antigen expression by expressing a second VSG and report that following DSB-triggered VSG switching, the DNA sequence of the ectopic VSG is lost in a transcription-dependent manner. We propose that there are strict requirements to ensure that only one variant antigen is expressed following a VSG switch, which has important implications for understanding how the parasite survives in the mammalian host.

The Trypanosoma (T) brucei life cycle alternates between the tsetse fly vector and the mammalian host. In the insect, T. brucei undergoes several developmental stages until it reaches the salivary gland and differentiates into the metacyclic form, which is capable of infecting the next mammalian host. Mammalian infectivity is dependent on expression of the metacyclic variant surface glycoprotein genes as the cells develop into mature metacyclics. The VEX complex is essential for monoallelic variant surface glycoprotein expression in T. brucei bloodstream form, however, initiation of expression of the surface proteins genes during metacyclic differentiation is poorly understood. To better understand the transition to mature metacyclics and the control of metacyclic variant surface glycoprotein expression we examined the role of VEX1 in this process. We show that modulating VEX1 expression leads to a dysregulation of variant surface glycoprotein expression during metacyclogenesis, and that following both in vivo and in vitro metacyclic differentiation VEX1 relocalises from multiple nuclear foci in procyclic cells to one to two distinct nuclear foci in metacyclic cells - a pattern like the one seen in mammalian infective bloodstream forms. Our data suggest a role for VEX1 in the metacyclic differentiation process and their capacity to become infectious to the mammalian host.

In the optical storage DC microgrid in island mode, in view of the large inrush current problem of the inverter controlled by the optical storage VSG when switching from offgrid to grid-connected operation mode, a pre-synchronization control strategy based on secondary frequency regulation and voltage regulation was proposed. This strategy can adjust the large frequency and voltage fluctuations caused by active and reactive load changes under the independent DC microgrid of the optical storage. At the same time, it can complete the effective tracking of the grid phase before connecting to the grid, and reduce the impulse current when the optical storage microgrid is isolated and connected to the grid. The real-time digital simulation platform (RTDS) is used to simulate and analyze the proposed control scheme, and the simulation results verify the feasibility of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper researched on the pre-synchronization grid connection method of a virtual synchronous generator (VSG), and proposed a fast pre-synchronization method based on the virtual power loop. According to the self-synchronization characteristics of the VSG power loop, the double power loop design was adopted in this paper. The two power loops had the same structure, which the power loop 1 was used to implement the basic VSG function, and the power loop 2 was used to achieve rapid pre-synchronous control. Therefore, the mathematical model of the VSG was similar to the synchronous generator in the pre-synchronization control. This method did not require a phase-locked loop and VSG has a good inertia and Damping performance. Moreover, this method was suitable for the networking of multiple VSGs.

Abstract Background Gold standard microscopic examination of Plasmodium falciparum intraerythrocytic stage remains an important process for staging and enumerating parasitized erythrocytes in culture; however, microscopy is laborious and its accuracy is dependent upon the skill of the examiner. Methods In this study, ViSafe Green (VSG), which is a nucleic acid-binding fluorescent dye, was used for assessing in vitro development of P. falciparum using flow cytometry. Results Fluorescence intensity of VSG was found to depend on the developmental stage of parasites. Specifically, multiple-nuclei-containing schizonts were observed in the VSGhigh population, and growing trophozoites and ring-shaped forms were observed in the VSGintermediate and VSGlow populations. The efficacy of VSG-based assay was found to be comparable to the microscopic examination method, and it demonstrated an ability to detect as low as 0.001% of the parasitaemia estimated by Giemsa staining. Moreover, when applying VSG for anti-malarial drug test, it was able to observe the growth inhibitory effect of dihydroartemisinin, the front-line drug for malaria therapy. Conclusions Taken together, the results of this study suggest the VSG-based flow cytometric assay to be a simple and reliable assay for assessing P. falciparum malaria development in vitro.

Similar to synchronous generators (SGs), the phenomenon of low-frequency oscillation (LFO) may occur when virtual synchronous generator (VSG) is involved in power grid, thereby negatively affecting the stability of the power system. In this paper, the oscillation mechanism of the power system composed of a VSG and infinite grid (single-VSG infinite-bus system) is analyzed, the conditions for the occurrence of LFO are unveiled, and a simplified damping selection method to suppress the LFO is provided, considering the adjustable damping of VSG. First, a small-signal model of the single-VSG infinite-bus system is established. The order of this system model is reduced using the damping torque analysis. Then, the mechanism of LFO under various dampings is analyzed. On this basis, a reasonable selection method of damping is drawn. The range of damping, where LFO converges, can be determined and the appropriate damping coefficient can be selected using this method. Finally, the effectiveness of the proposed method is verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study is to assess whether vertical sleeve gastrectomy (VSG) increases the incidence of gastroesophageal reflux disease (GERD), esophagitis and Barrett esophagus (BE) relative to patients undergoing Roux-en-Y gastric bypass (RYGB) in patients with and without preoperative GERD. Summary of Background Data: Concerns for potentiation of GERD, supported by multiple high-quality retrospective studies, have hindered greater adoption of the VSG. Methods: From the OptumLabs Data Warehouse, VSG and RYGB patients with ≥2 years enrollment were identified and matched by follow-up time. GERD [reflux esophagitis, prescription for acid reducing medication (Rx) and/or diagnosis of BE], upper endoscopy (UE), and re-admissions were evaluated beyond 90 days. Results: A total of 8362 patients undergoing VSG were matched 1:1 to patients undergoing RYGB, on the basis of post-operative follow-up interval. Age, sex, and follow-up time were similar between the 2 groups (P > 0.05). Among all patients, postoperative GERD was more frequently observed in VSG patients relative to RYGB patients (60.2% vs 55.6%, respectively; P < 0.001), whereas BE was more prevalent in RYGB patients (0.7% vs 1.1%; P = 0.007). Postoperatively, de novo esophageal reflux symptomatology was more common in VSG patients (39.3% vs 35.3%; P<0.001), although there was no difference in development of the histologic diagnoses reflux esophagitis and BE. Furthermore, postoperative re-admission was higher in the RYGB cohort (38.9% vs 28.9%; P < 0.001). Conclusions: Compared to RYGB, VSG may not have inferior long-term GERD outcomes, while also leading to fewer re-hospitalizations. These data challenge the prevailing opinion that patients with GERD should undergo RYGB instead of VSG. [ABSTRACT FROM AUTHOR]

This paper proposes an inductor current sensorless control strategy based on modified virtual synchronous generator (VSG) method for single-phase inverter-interfaced microgrid application. Firstly, the outer power loop with Q-U integral term is presented for output reactive power enhancement, and an inner voltage regulation loop based on luenberger state observer is proposed to reduce the inductor current sensor. Meanwhile, in order to improve the response speed of the observer, the luenberger observer is designed based on the optimal pole assignment method. Secondly, a seamless switching strategy based on the modified VSG method is proposed, which can realize the seamless transition between the island mode and grid-connected mode. Finally, a single-phase 3kW VSG prototype is built, and the effectiveness and correctness of the proposed control strategy is verified by the simulation and experimental results.

Electrical energy storage (EES) with a virtual synchronous generator (VSG) method is used widely for power fluctuation compensation in renewable energy microgrid systems. In the traditional VSG method, the inertia moment and damping coefficients usually remain constant. When dealing with large load variations, this method may cause obvious system frequency deviations and exceed the standard limit (e.g., IEEE Std 1547-2018). This paper proposes a novel control method combining fuzzy control with a model predictive controller (MPC) to solve this problem. The new method was applied to VSG. The virtual inertia and damping coefficient of VSG are on-line adjusted by a fuzzy controller, so that the regulation capability of the swing equation can be substantially utilized. The optimal rated power of VSG was modified using the MPC method, which further strengthens the EES support for power needs. The system frequency performance can be enhanced effectively under joint control. The simulation and experimental results further demonstrated the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]