Search

Copyright of Electric Power Engineering Technology is the property of Editorial Department of Electric Power Engineering Technology 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.)

The accuracy of the steady-state analysis of a power system network at constant conductor temperature with modern software such as Mathcad, RastrWin3, and MatLab (MatPower and Optimization Toolboxes) is analyzed. The topology of the network and the parameters (impedances and admittances) of its lines, consumption and generation at nodes (buses) of the power system are considered known. The exact solutions for the complex node voltages in an IEEE 5-bus test network are found at which the active power is balanced with an accuracy of 10–307, either in the absence or in the presence of a PV-type node. The errors in the magnitudes (moduli) and phase angles (arguments) of the node voltage vectors calculated with the highest possible accuracy using modern software systems for different operating modes of the power system are analyzed. The results obtained are useful for further development of methods and algorithms for steady-state analysis of a power system and selection of a tool for simulation of its unsteady states. System operators need to perform such analyzes to solve many applied problems. [ABSTRACT FROM AUTHOR]

In order to improve the orderly control and flexible adjustment capabilities of large-scale distributed power sources connected to the distribution network, it is currently an effective method to reasonably divide the distributed power sources into clusters and use the cluster as the basic unit for regulation. To this end, a distributed power cluster partitioning method that considers the adjustable capacity and response speed of flexible resources is proposed. Firstly, the modularity index and the active power balance index are proposed to characterize the structural and power balance capability of clusters. Secondly, based on the analysis of the cluster's flexible response capability, and in view of the problem that it is difficult to quantify the impact of the flexible resource response capacity and response speed on the adjustment capability, it is proposed to take the cumulative area of deviation between the response curve of cluster output and the net load curve as the indicator of the flexible response capability of clusters, and the influence of the allocation of energy storage capacity on the delineation of clusters is also taken into account. Then, a cluster division objective function that comprehensively considers the modularity index, active power balance index, cluster flexible response capability index and energy storage unit allocation index is proposed, and this function is solved using an improved adaptive genetic algorithm. Finally, the proposed method is verified in the improved IEEE 33-node system and IEEE 69-node system. The results show that the cluster partitioning method based on the proposed comprehensive performance index can improve the cluster flexible response capability by more than 20% on the basis of ensuring the structural strength of the cluster, which verifies the effectiveness and superiority of the cluster partitioning method proposed in this paper.

For the VSC-HVDC system transmitting new energy， poor parameter matching between the new energy controller and the VSC-HVDC controller can lead to sub-synchronous and super-synchronous oscillation. To address this， an open-loop strategy based on virtual synchronous generator （VSG） control has been adopted. This strategy eliminates the inner and outer loops and the phase lock of traditional closed-loop control methods， optimizing the impedance characteristics of the VSC-HVDC system and reducing the risk of sub-synchronous and super-synchronous oscillations of new energy. It is also compatible with both islanded and grid-connected operating modes. To address bipolar power imbalance and excessive short-circuit current after faults in open-loop control， bipolar power balancing and fault ride-through （FRT） strategies have been proposed. The effectiveness of the proposed VSG control and FRT strategies has been validated through RTDS simulations.

A direct current power flow controller is a key device for regulating steady-state power flow in multi-terminal DC （direct current） grids. In response to the limitations of existing DC power flow controllers， a novel multi-port DC power flow controller is designed by incorporating a cascaded submodules with adjustable DC output voltage in a circular branch. Firstly， the topology and operation principles of the proposed controller are explained. Then， its control strategies and parameter selection methods are introduced. Finally， the performance of the DC power flow controller is validated through electromagnetic transient simulations on a five-terminal DC grid with eight DC lines. The results indicate that the proposed controller can simultaneously regulate power flow on multiple DC lines connected to the same DC bus， demonstrating advantages of modularity and easy scalability.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny 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.)

Copyright of Zhejiang Electric Power is the property of Zhejiang Electric Power Editorial Office 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.)

Copyright of Zhejiang Electric Power is the property of Zhejiang Electric Power Editorial Office 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.)

The cascaded H-bridge (CHB) inverter has become pivotal in grid-connected photovoltaic (PV) systems owing to its numerous benefits. Typically, DC–DC converters are employed to boost the input voltage in grid-connected systems to meet the grid's higher voltage requirements, but this approach increases equipment size and cost. To enhance inverter efficiency, this paper proposes a boost-type, three-phase CHB PV grid-connected inverter. This design can raise the input voltage and satisfy grid requirements with only a few additional components. Additionally, PV environmental fluctuations can cause variations in PV power generation, leading to a power imbalance in the inverter and potentially affecting the stability of the PV system. Based on this, we consider grid voltage fluctuations induced by unbalanced power output from the inverter and propose an improved control method based on the superposition of zero-sequence components. Finally, we construct a simulation model and conduct experimental verification using the MATLAB/Simulink platform. The validation results demonstrate that this topology reduces equipment volume and effectively enhances the efficiency of PV power generation systems. Furthermore, the designed control method ensures system stability while effectively mitigating power imbalances caused by PV module and grid voltage fluctuations. [ABSTRACT FROM AUTHOR]

Copyright of Integrated Intelligent Energy is the property of Editorial Department of Integrated Intelligent Energy 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.)

Global power balance calculations in steady state H mode plasmas varying the distance between separatrices (drsep) and the divertor configuration have been performed in MAST Upgrade. As drsep becomes more negative, more of the power crossing the separatrix goes to the lower divertor. The inner divertor receives a higher fraction of the power exhaust in a Super-X divertor plasma compared to a conventional divertor plasma at similar negative drsep, which is a concern for high power devices employing alternative divertor configurations for power exhaust handling. Global power accounting suggests >30% of the input power is unaccounted for with the power loss channels quantified in this work. Charge exchange and orbit losses from the NBI could account for a large fraction of unaccounted power but it is not possible to precisely determine this without further diagnostic calibration.

Modular multilevel converter (MMC)-based high-voltage DC (HVDC) systems have found rapid growth in power grids. To reduce the inrush current, it is necessary to precharge the submodule (SM) capacitors to the rated voltage before normal operation. In this paper, an optimized pre-charging strategy for MMC is proposed based on power balancing . First, the charging power is obtained by a designed closed-loop control of the SM capacitors. Then the total power released by the AC or DC side could be calculated by power conservation and feedback by controlling the charging current. At the same time, the power difference between the upper and lower bridge arm of each phase and the internal voltage balancing of bridge arms are also considered by the proposed bridge arm and SM voltage algorithms. By comparing with conventional closed-loop pre-charging strategies, the pre-charging speed is greatly enhanced as the achievement of synchronous charging of upper and lower bridge arm SMs. Moreover, as the same voltage and current double closed-loop control applied in both MMC pre-charging and normal state, the state transition time could be reduced. Finally, a series of simulations and prototype experiments are conducted to verify the feasibility of the proposed pre-charging strategy.

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & 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.)

Copyright of Electric Drive is the property of Electric Drive Editorial Office 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.)

Currently, the study of energy balancing in cascaded multilevel inverter cells is desirable due to the growing interest in implementing systems that minimize losses, ensure delivery of the maximum amount of power to the load, contribute to system reliability, and at the same time minimize the use of resources for its implementation. One of the ways to carry out energy balancing without resorting to additional topology is by modifying conventional modulation techniques. In this letter, the FPGA implementation of modulation strategies for energy balancing purposes is carried out. First, three conventional techniques are addressed: 1) phase-shifted carrier disposition; 2) level shift per carrier cycle; and 3) level shift per modulator cycle. Subsequently, the implementation of an alternative modulation strategy that performs energy balancing in the cascaded multilevel inverter, minimizing the use of digital resources, is presented. [ABSTRACT FROM AUTHOR]

The electrolytic capacitor-less variable frequency drive scheme using film capacitors to replace electrolytic capacitors has been partially applied in the field of washing machines and air conditioners driven by permanent magnet synchronous motors, due to its advantages of good reliability and low cost. However, recently, with the development and application of synchronous reluctance motors to replace permanent magnet synchronous motors, the existing methods have problems such as id = 0 control unsuitable for synchronous reluctance motors, low power factor on the input side, and poor motor running performance and other problems. Therefore, firstly, this paper takes the variable frequency drive system for the synchronous reluctance motors as the research object, analyses the influence of the value of the bus capacitance on the performance of the variable frequency drive system, and provides a theoretical basis for the selection of bus capacitance. Secondly, a current control strategy based on power balance and compensation is proposed, which includes current feeding based on power balance, input voltage phase detection based on a phase-locked loop, and output voltage vector regulation based on power compensation. To verify the correctness of the proposed method, a platform was built and tested, and the experimental results show that the electrolytic capacitor-less variable frequency drive system for synchronous reluctance motors using the method proposed in this paper not only improves the power factor at the input side of the drive system but also reduces the fluctuation of the motor speed and torque, which in turn improves the operating performance of the motor.

Due to their minimal environmental impact, green energy sources like wind turbines and solar panels are increasingly utilized in power systems. However, the power they generate is highly variable, leading to unpredictable fluctuations in power supply. Additionally, advanced smart functions in consumer devices and their unpredictable usage patterns contribute to similar fluctuations in power consumption. These fluctuations present a significant challenge to the stability and quality of the power grid, creating a complex issue of power imbalance that becomes harder to manage. Innovative management and control approaches are necessary to address these challenges and thus support the shift to sustainable energy sources. Artificial intelligence (AI) techniques are increasingly proposed as promising solutions, albeit mostly implemented as isolated solutions within centralized power control systems. To effectively manage the complex and often large scale power systems, this paper advocates the use of a Distributed AI (DAI) framework as imperative in enhancing their agility and stability. An illustrative Nano-Grid example (including the potential use of battery sources in extreme scenarios) is adopted to demonstrate the framework’s utility, and a number of power control strategies to safeguard the power system against the variability of both power generators and loads are theoretically formulated and then realized within the proposed framework. Linear Programming, Ant Colony Optimization, Genetic Algorithms, and Particle Swarm Optimization techniques are experimented with, and through simulations, the utility of the DAI framework is demonstrated. The findings underscore the effectiveness and potential benefits of the proposed framework in ensuring the safe and effective operation of power systems with the use of particle swarm optimization amid fluctuating energy scenarios with a small to large number of devices in the nano-grid.

Since the end of the Cold War, Russia and the West have engaged in fierce geopolitical competition over the post-Soviet space. Separatism in the post-Soviet space has become a hallmark of their relationship, even an accelerator of contradictions. This paper analyzes Russia’s policy evolution towards separatism in the post-Soviet space from the perspective of the interaction between power and norms to grasp the changes in power dynamics and territorial integrity norms in this region.

Copyright of Electric Drive is the property of Electric Drive Editorial Office 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.)

With the development of new urban power systems, the centralized-distributed hierarchical partition management architecture has gradually become a consensus. Existing hierarchical partition methods are mostly static. And if the partition results are determined, it will remain unchanged for a relatively long time. However, the new type power system experiences more frequent and larger fluctuations in power generation and load, requiring dynamic responses to the system's real-time operation. In this case, traditional partition methods are no longer applicable, and new hierarchical partition methods for system operation need to be adopted. Therefore, this paper proposes a power balance mechanism of urban power system based on dynamic hierarchical partition method, including dynamic hierarchical partition method and corresponding decoupling power balance models. The former can continuously change the results of hierarchical partition according to the real-time state of the power system, so as to reduce the inter-regional liaison cost and improve the economy. The latter improves the independence of the region and the security of the power system through decoupling power balance. Eventually, the proposed method is validated with an modified Hawaii 37-node system. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & 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.)

Copyright of Electric Power is the property of Electric Power Editorial Office 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.)

In order to obtain more ideal energy storage capacity planning results, a new stochastic planning method for energy storage capacity of interconnected microgrid was proposed on the basis of considering the optimal power balance and demand response. Under the condition of demand response, based on the operation mode and stochastic theory of networked microgrid, the optimal power balance was taken as the planning goal, and the stochastic planning model of energy storage capacity was established. The particle swarm optimization algorithm was used to solve the stochastic programming model of energy storage capacity, and the optimal stochastic programming scheme of energy storage capacity of interconnected microgrid was obtained. The experimental results show that with the continuous increase of capacitance, the overall balance ability of microgrid becomes stronger. The energy balance index of the proposed method is higher, the rated capacity of energy storage is more stable, and the load of energy storage system is smaller, planning efficiency is higher. The proposed method can better realize the energy storage capacity planning of networked microgrid. [ABSTRACT FROM AUTHOR]

With the integration of large-scale photovoltaic power stations into power grids, the traditional strategy of the backup automatic switch is affected. When a grid fault occurs, due to the existence of photovoltaic power sources, the busbar voltage at the fault point cannot meet the 'no voltage' criterion, and the traditional strategy cannot operate correctly. In order to improve new energy utilization and ensure normal input of the backup power supply without disconnecting photovoltaic power sources, a new backup automatic switch scheme based on distributed buffer resistors is proposed. Firstly, the influence of the mismatch between photovoltaic output and load power on the grid-connected point voltage is analyzed. Secondly, distributed buffer resistor branches are connected in parallel at both ends of the DC capacitor in each photovoltaic power generation unit, using buffer resistors to suppress the power imbalance formed in the islanded state after the main power supply is disconnected (before the backup automatic switch operates), realizing safe and fast operation of the backup automatic switch. Finally, MATLAB/Simulink is used to simulate and verify the scenario of extreme mismatch between photovoltaic and load power, and the inrush current can be limited to 1.5 times rated current, which meets the relevant specifications and verifies the feasibility and effectiveness of the proposed new backup automatic switch scheme.

Installed capacity of wind farms is growing rapidly in the electric power systems. The Russian Federation has adopted a set of legislative measures to increase wind farms (WF) installed capacity. The research focuses on assessing the impact of wind farms in electric power system (EPS). In particular, the wind farms distribution impact over electric power system nodes is considered in comparison with single high-capacity wind farm (Eysk). Based on the calculations of the daily unevenness factor, installed capacity utilization rate and grid heterogeneity, following conclusions are obtained: the high-capacity wind farm has a higher daily power fluctuation amplitude, up to a nominal capacity of 3.4 GW; installed capacity utilization rate of wind farms system will always be lower when compared to a high-capacity wind farm located in the same location with the best wind energy potential; wind farms distribution across EPS nodes increase their rigidity (the ability to maintain the node voltage as the load changes) and, as a result, their reliability. The graphical illustration of the sensitivity of a 64 node 110-500 kV power grid demonstrates the increase in the number of rigid nodes.

The feasibility of positive energy yield in systems with the p–11B reaction is considered here by considering refined (optimistic) data on the reaction rate. The analysis was carried out within the traditional framework for magnetic confinement systems, but without taking into account a particular type of plasma configuration. The energy balance was considered both for the ions and electrons. The balance of particles includes all species as well as the products of fusion (alpha particles). Calculations have shown that accounting for the content of thermalized reaction products (alpha particles) leads to an increase in radiation losses and a decrease in gain to Q < 1. In the steady-state scenario, the energy gain Q~5–10 can be obtained in p–11B plasma, if only the fast (high-energy) population of fusion alpha particles is considered. For pulsed modes, the gain value is proportional to the content of alpha particles, and it is limited by the complete burn of one of the fuel components (boron), so it does not exceed unity. In the analysis we did not rely on any assumptions about the theoretically predicted mechanisms for increasing the cross section and the reaction rate, and only radiation losses (primarily bremsstrahlung) dramatically affect the gain Q. Thus, the regimes found can be considered as limiting in the framework of the classical concepts of processes in hot fusion plasma.

With the development of new urban power systems, the centralized-distributed hierarchical partition management architecture has gradually become a consensus. Existing hierarchical partition methods are mostly static. And if the partition results are determined, it will remain unchanged for a relatively long time. However, the new type power system experiences more frequent and larger fluctuations in power generation and load, requiring dynamic responses to the system’s real-time operation. In this case, traditional partition methods are no longer applicable, and new hierarchical partition methods for system operation need to be adopted. Therefore, this paper proposes a power balance mechanism of urban power system based on dynamic hierarchical partition method, including dynamic hierarchical partition method and corresponding decoupling power balance models. The former can continuously change the results of hierarchical partition according to the real-time state of the power system, so as to reduce the inter-regional liaison cost and improve the economy. The latter improves the independence of the region and the security of the power system through decoupling power balance. Eventually, the proposed method is validated with an modified Hawaii 37-node system.

In this paper, a terminal sliding mode backstepping controller (TSMBC) has been proposed for various components of a hybrid AC/DC microgrid (HADMG) to enhance its dynamic stability. The proposed control technique is employed to generate switching control signals for converters, which serve as the primary interface between the DC bus and the AC bus in a hybrid microgrid. Additionally, this technique facilitates the interface of PMSG-based wind generators, solar photovoltaic generators, and battery energy storage systems with the DC bus. Through the implementation of the composite control technique, the global stability of the microgrid is ensured by driving all the states of the HADMG associated with various components to converge towards their intended values. Afterward, the Lyapunov control theory has been used to analyze the converter and inverter's large-signal stability while ensuring the robustness of the proposed robust composite controller. Finally, an extensive simulation study was conducted on a hybrid microgrid to verify the efficacy of the designed controller in maintaining power balance amidst variations in the system's operational regimes. Moreover, the effectiveness of the controller's practical implementation is confirmed by real-time processor-in-the-loop analysis. Simulation results clearly show that the proposed TSMBC improves the overall dynamic performance of the hybrid microgrid with less overshoot (0%) and settling time (110 ms) in DC bus voltage when compared to the existing sliding mode controller. • Enhance the dynamic and transient stability of an AC/DC hybrid microgrid (ADHMG). • A composite terminal sliding mode backstepping controller (TSMBC) is used to obtain the switching control signals for the converters and inverters. • Maintain the power balance with changes in the system's operating point. • It provides superior performance as compared to the existing control approach in terms of overshoot and settling time. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Engineering Technology is the property of Editorial Department of Electric Power Engineering Technology 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.)

Copyright of Bulletin of Ablai Khan KazUIRandWL: Series 'International Relations & Regional Studies' is the property of Kazakh Ablai Khan University of International Relations & World Languages 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.)

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & 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.)

Currently, an increasing number of designers have begun to pay attention to a new paradigm for evaluating the performance with full engine 3-dimensional computational fluid dynamics (3D CFD) simulations. Compared with the traditional component-based performance simulation method component-based performance simulation method ('component-matched' method), this novel 'component-coupled' method can evaluate the overall performance of the engine more physically and obtain more detailed flow field parameters simultaneously. Importantly, the power balance iteration should be introduced to the novel method to satisfy the constraints of the coaxial components for the gas turbine engine at steady state. By carrying out the 'component-matched' simulation and the 'component-coupled' simulation for a micro turbojet engine, the necessity of introducing the power balance iteration was discussed in this paper. The influence of steady-state co-working constraints on the engine performance was analysed and strategies for power balance iteration were proposed. To verify the capability and feasibility of this method, not only the co-working state but also the windmill state of the gas turbine engine were simulated by using the 3D CFD method considering power balance iteration. The results show that the power balance strategy proposed in this paper can converge the aerodynamic parameters as well as the power residual in a robust way. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & 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.)

Oscillatory processes in nonlinear multiphase electro ferromagnetic circuits (EFMC) have an exceptional variety and complexity, and therefore their research is also associated with solving complex physical problems. Theoretical analysis, in order to identify the main patterns of excitation of subharmonic oscillations of various orders, and the development of engineering calculation methods are of particular importance in designing and creating various switching-type converter devices. On the other hand, two-phase self-oscillating circuits are physical models of power transmission lines (power lines). Consequently, the study of the excitation of the existence of subharmonic oscillations in two-phase systems allows us to establish some patterns of overvoltage with power lines with capacitive compensation caused by harmonic oscillations, and, if possible, take measures to prevent these abnormal modes or mitigate their negative consequences. This article discusses the process of excitation of subharmonic oscillations ω/2 in two-phase EFMC. Using the method of energy relations, the areas of existence and critical values of the circuit parameters are determined.

This paper presents new directions in the modeling of electric arc furnaces. This work is devoted to an overview of new approaches based on random differential equations, artificial neural networks, chaos theory, and fractional calculus. The foundation of proposed solutions consists of an instantaneous power balance equation related to the electric arc phenomenon. The emphasis is mostly placed on the conclusions that come from a novel interpretation of the equation coefficients.

The article considers the implementation of batteries for a typical single-family house with a photovoltaic system. The calculations of the impact of accumulator capacity on the self-sufficiency coefficient and the annual energy balance were analysed. The results of simulation of electricity flow in a hybrid system for a typical single-family house are given. [ABSTRACT FROM AUTHOR]

MMC is widely used in high-voltage DC transmission applications due to its highly symmetrical sub-module cascade structure and good output waveform quality. The presence of MMC circulating current will aggravate the bridge arm loss, distort the bridge arm current and generate high harmonic components, which will seriously damage the power quality. In view of this problem, this study adopts the method of extracting the AC component of the circulating current by a multi-harmonic filter based on the interplay of SOGI and DC integrator and suppressing the circulating current by a new circulating current suppressor composed of three quasi-PR controllers connected in parallel. An 11-level MMC inverter simulation model is established on MATLAB/Simulink platform, and the simulation results show that the proposed control strategy can effectively complete the control of the system. Compared with the traditional circulating current suppression method, the circulating current suppression effect of the proposed method is more obvious, and the capacitor voltage fluctuation range is reduced by about 60%, which verifies the correctness and effectiveness of the proposed control circulating current control strategy. [ABSTRACT FROM AUTHOR]

Copyright of Medunarodni Problemi is the property of Institute of International Politics & Economics 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.)

The aerodynamic design of a new aircraft concept was investigated through subsonic wind-tunnel testing using 1:28-scale powered models. The aircraft configuration integrates a box-wing layout with engines located at the rear part of the fuselage. Measurements involved a back-to-back comparison between two aircraft models: a podded version whose engines were assembled on pylons and a boundary-layer ingestion (BLI) version that provided several system-level benefits. The flowfield was investigated through the power balance method and a variety of pressure flowfield and inlet flow distortion metrics. The results proved that the BLI configuration enhances the propulsive efficiency by reducing both the electrical power coefficient and the kinetic energy waste due to lower jet velocities. Furthermore, there was a reduction of the total pressure recovery due to pressure gradients inside the duct, thereby causing high distortion. Overall, this research highlights the importance of wind-tunnel testing to bring any aerodynamic technology to a sufficient level of maturity and to enable future new aircraft concepts. [ABSTRACT FROM AUTHOR]

The traditional two-unit cascaded H-bridge inverter had a small number of output levels, and the output power of each unit was unbalanced under the traditional carrier amplitude shift modulation strategy. To solve these problems, this paper proposed an asymmetric cascaded eight switch inverter topology, and proposed an improved POD-PWM power equalization modulation strategy for the proposed topology. The inverter was cascaded by two identical asymmetric eight switch seven level inverters, which could output 13 level voltage, and achieved the output power balance between units in an output cycle while reducing the number of switches. Finally, the correctness and feasibility of the proposed topology and its power equalization method was verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

Analysis of the influence of transmission-line parameters and its unbalanced load on the voltage quality and energy losses in the line is performed. This research has been carried out on a standard IEEE four-node test model of an electrical network. Mathematical and algorithmic tools for studying of asymmetric operating modes of power-transmission lines are proposed and justified, combining the use of a specialized program for calculating the operating modes of power systems with UDSLF asymmetric loads with the Newton–Raphson method, this being one of the most effective tools for determining the roots of a system of nonlinear equations. The peculiarities of the influence of power-line load asymmetry on energy losses and voltage quality when changing power line and load parameters are illustrated. Ways to improve the efficiency of power-transmission lines with asymmetric loads are proposed. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a Backstepping Global Integral Terminal Sliding Mode Controller (BGITSMC) with the view to enhancing the dynamic stability of a hybrid AC/DC microgrid has been presented. The proposed approach controls the switching signals of the inverter, interlinking the DC-bus with the AC-bus in an AC/DC microgrid for a seamless interface and regulation of the output power of renewable energy sources (Solar Photovoltaic unit, PMSG-based wind farm), and Battery Energy Storage System. The proposed control approach guarantees the dynamic stability of a hybrid AC/DC microgrid by regulating the associated states of the microgrid system to their intended values. The dynamic stability of the microgrid system with the proposed control law has been proved using the Control Lyapunov Function. A simulation analysis was performed on a test hybrid AC/DC microgrid system to demonstrate the performance of the proposed control strategy in terms of maintaining power balance while the system’s operating point changed. Furthermore, the superiority of the proposed approach has been demonstrated by comparing its performance with the existing Sliding Mode Control (SMC) approach for a hybrid AC/DC microgrid.

In hybrid AC/DC microgrid, interlinking converter (ILC) can balance power flow between AC and DC microgrid, thus stabilizing AC frequency and DC voltage in islanding mode. As a topology of ILC, modular multilevel interlinking converter (MMILC) has advantages of good harmonic characteristics, high quality waveforms and low switching loss. A two-stage droop control strategy for MMILC is proposed. Firstly, based on the energy fluctuation characteristics of the sub-module capacitance, a new unified droop characteristic of AC and DC side for MMILC is established. Then, a mathematical relation between DC voltage and equivalent sub-module capacitor voltage is given to adjust power reference according to deviation of dc voltage. Also the dead zone and an allowable minimum operation range of the droop characteristic are set. Finally, the control performance of MMILC in different load profiles and overload conditions are simulated. The simulation results show that the proposed two-stage droop control strategy of MMILC can automatically compensate the power to both AC/DC sides in different load profiles. Under overload conditions, MMILC can instantaneous block the active power transmission, which validates the correctness and availability of the control strategy.