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The grid-forming virtual synchronous generator (GFVSG) not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power (GCAP) dynamic oscillation issues, akin to those observed in traditional synchronous generators. In response to this, an improved strategy for lead-lag filter based GFVSG (LLF-GFVSG) is presented in this article. Firstly, the grid-connected circuit structure and control principle of typical GFVSG are described, and a closed-loop small-signal model for GCAP in GFVSG is established. The causes of GCAP dynamic oscillation of GFVSG under the disturbances of active power command as well as grid frequency are analyzed. On this basis, the LLF-GFVSG improvement strategy and its parameter design method are given. Finally, the efficiency of the proposed control strategy in damping GCAP dynamic oscillations under various disturbances is verified using MATLAB simulations and experimental comparison results. [ABSTRACT FROM AUTHOR]

Even for short space flights, such as manned flights to the Moon back in the 60s, it became extremely obvious that electric batteries are completely unsuitable because of their huge mass needed to store the required supply of onboard energy. Therefore, already in the 60s of the last century, the USA and the USSR took the path of using a hydrogen storage system using hydrogen fuel cells. Solar-hydrogen energy systems for spacecraft reliably provide energy for carrying out various kinds of unscheduled work on board and for eliminating emergency situations. Surplus energy is constantly accumulated on board in the form of the chemical energy of cryogenic hydrogen. The article presents too the result of the development of a solar-hydrogen power supply system for spacecraft, the onboard network of which provides slow and fast processes. This paper delves into designing digital control systems for power conditioning devices on the example of charging-discharging device based on a boost DC-DC converter. The device was implemented to condition a storage battery by properly charging and discharging it. A technique for constructing a small signal model of the converter has been developed. This involves constructing a block diagram using the discontinuous switching functions and analog models of electrical circuit components. The transfer functions of the analog controllers for the two-loop subordinate control system were derived. Then the procedure of a bilinear z-transform to the given transfer functions was applied. As a result, the discrete transfer functions of the digital controllers were obtained. Realization both analog and digital controllers in Matlab Simulink confirmed their identical behavior and stability within the power converter. Experimental studies of the static and dynamic waveforms of the digital control system showed controllability and stability of the charging-discharging device for the storage battery in typical operating modes. Thus, the method of synthesizing digital control systems for energy converters is proved valid and applicable for designing new power conditioning devices within modern power supplies. [ABSTRACT FROM AUTHOR]

The given power and grid frequency disturbances can cause transient oscillations and steady-state deviations in the output power of a virtual synchronous generator (VSG), which can be effectively addressed by adding transient damping. However, this approach may result in significant power overshoot. This article proposes an improved VSG control strategy based on transient electromagnetic power feedback compensation and a small-signal model reduction scheme. Firstly, the grid-connected active closed-loop small-signal models of typical VSG control and transient damping VSG control are established, respectively. The transient oscillation suppression mechanism of active power is revealed through root locus and frequency response analyses, and the power overshoot characteristics of the two control strategies are analysed by combining them with the system of zero points. Secondly, the active transient feedback compensation method and the small-signal model reduction design method are introduced in detail. Finally, comparative analysis experiments are conducted using the Matlab/Simulink and hardware-in-the-loop experimental platform. It is verified that the proposed control strategy can suppress transient oscillations in active power, prevent steady-state deviations, and effectively mitigate the power overshoot problem of the system. [ABSTRACT FROM AUTHOR]

This paper presents ready-to-use nonlinear and linear averaged models of an improved cascade buck converter (ICBC) for the first time. A detailed steady-state analysis is also given, providing its operating modes, equilibrium values, and design guidelines. The modelling process consists of two stages. First, the nonlinear model is obtained using the state-space averaging technique. Subsequently, the averaged model is linearised by applying the small-ripple approximation and the small-signal model is achieved. Furthermore, the developed small-signal model is employed to derive three significant transfer functions of the converter. The proposed converter model is valid for the continuous conduction mode (CCM) when the duty cycle is lower than $0.5$ 0.5. To be used in validation studies, an exemplary converter with $144{\rm{ W}}$ 144 W rated power that steps down $320{\rm{ V}}$ 320 V input voltage to $24{\rm{ V}}$ 24 V is designed. The accuracy of theoretical analyses is confirmed by the simulation results of the designed converter. Similarly, all proposed models are validated with the simulations done in both frequency-domain and time-domain. The results show that the proposed parametric model response closely matches that of the switching (non-parametric) model and hence it can be safely used for controller design in feedback systems. [ABSTRACT FROM AUTHOR]

Hybrid DC transmission systems are prone to DC current oscillations as the parameters of constant DC current controller increase， an oscillation suppression strategy based on virtual resistance is proposed. This strategy generates an additional voltage that is in phase opposition to the disturbance component by leveraging the current oscillation component and an introduced virtual resistance， thereby achieving suppression of the DC current oscillations. Initially， a small-signal model of the hybrid DC transmission system is established to analyze the impact of parameters of the constant DC current controller on the stability of small signals. Subsequently， an oscillation suppression strategy based on virtual resistance is put forward to study the influence of virtual resistance on the stability of small signals in the system. The effectiveness of the proposed strategy is verified through PSCAD/EMTDC simulations. Lastly， the stability range of the virtual resistance under different constant current controller parameters is analyzed. The research findings indicate that the proposed control strategy can effectively eradicate DC current oscillations and improve system stability.

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 virtual synchronous generator (VSG) has been widely used to improve the system inertia and damping in the renewable energy generation system. However, the in-depth understanding of VSG's stability under disturbances on different control parameters is lacked. In order to solve the problem, the small-signal model of single-VSG is established at first. The influences of key control parameters on the stability of system are analyzed by using the eigenvalue analysis method in detail. On this basis, a novel optimization strategy for control parameters is proposed based on the Particle Swarm Optimization (PSO) algorithm. The control parameters are optimized to realize excellent damping and stability of VSG system. Finally, the simulation and experimental results verify the effectiveness of stability analysis and parameter optimization strategy. [ABSTRACT FROM AUTHOR]

The extraction of small‐signal parameters is of great importance for the modeling of InP heterojunction bipolar transistors (HBTs). This letter proposes an improved small‐signal parameter extraction method that considers both the emitter–collector capacitance effect and the current crowding effect. The corresponding parameter extraction procedure based on closed‐form equations is outlined. Furthermore, the model parameter extraction method is validated using two different‐sized InP HBT devices with multibias S‐parameters. The results demonstrate that the established small‐signal model exhibits greater than 90% accuracy across the frequency range of 1–110 GHz. In particular, in the high‐frequency band (above 50 GHz), the proposed model exhibits an improvement in accuracy of 7.4% after considering the emitter–collector capacitance and current crowding effects. This method can contribute to accurate modeling of the noise and large‐signal performance of InP HBT. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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.)

This paper presents an in-depth analysis of an excitable membrane of a biological system by proposing a novel approach that the cells of the excitable membrane can be modeled as the networks of memristors. We provide compelling evidence from the Chay neuron model that the state-independent mixed ion channel is a nonlinear resistor, while the state-dependent voltage-sensitive potassium ion channel and calcium-sensitive potassium ion channel function as generic memristors from the perspective of electrical circuit theory. The mechanisms that give rise to periodic oscillation, aperiodic (chaotic) oscillation, spikes, and bursting in an excitable cell are also analyzed via a small-signal model, a pole-zero diagram of admittance functions, local activity, the edge of chaos, and the Hopf bifurcation theorem. It is also proved that the zeros of the admittance functions are equivalent to the eigen values of the Jacobian matrix, and the presence of the positive real parts of the eigen values between the two bifurcation points lead to the generation of complicated electrical signals in an excitable membrane. The innovative concepts outlined in this paper pave the way for a deeper understanding of the dynamic behavior of excitable cells, offering potent tools for simulating and exploring the fundamental characteristics of biological neurons. [ABSTRACT FROM AUTHOR]

This article proposes a parameter extraction method suitable for Si substrate based GaN HEMT small signal equivalent circuit models. The proposed method is based on a swarm intelligence optimization algorithm, which improves efficiency and accuracy by introducing a slope penalty factor (SPF) method for the objective function, rather than simply minimizing the error between simulation and measurement. By using PSO, WOA, and PNC-WOA for validation, we have demonstrated the advantages of the SPF method in extracting small signal parameters using swarm intelligence optimization algorithms. It is suitable for complex small-signal models that can describe the GaN HEMT-on-Si substrates, even if working up to 40 GHz. [ABSTRACT FROM AUTHOR]

An improved small‐signal model applied to GaN‐based devices is presented in this article. The extrinsic elements of the equivalent circuit topology are extracted using the test structures and the cut‐off method. In order to obtain a good agreement between model simulations and measurements, distributed capacitive effects are taken into account. In addition, an inductance Lds is introduced based on the conventional intrinsic equivalent circuit topology. Good agreement between the modeled and measured S‐parameters is obtained for GaN HEMTs with a gate width of 2 × 100 μm (number of gate fingers × unit gate width) in the frequency range of 0.5–40 GHz. [ABSTRACT FROM AUTHOR]

Several existing research studies on the modeling of photovoltaic (PV) systems feeding a resistive load through a DC-DC converter have proven that the use of the small-signal approach using analytical or graphical methods for the design of a linear model is failing. This is due to the fact that the simplified linear model, usually presented by a transfer function, is unable to reveal all the existing information about the actual solar system behavior when subjected to the Standard Test Conditions (STC). Since it does not take into account: (i) the nonlinearity of the current–voltage (I-V) characteristic of the solar panel, (ii) the presence of elementary components in both the solar panel and the DC-DC converter, which are often unmodeled and cannot be easily considered in the modeling, (iii) the existence of extra components in the DC-DC converter and more dynamics that must be neglected at high frequencies, for example those describing the thermal energies dissipated in the IGBT part of the DC-DC boost converter, the presence of cross-coupling between some electrical quantities occurring either in the DC-DC boost converter or in the solar panel, etc. For these reasons, this paper proposes a new design of a small-signal linear model to accurately describe the actual solar system behavior operating at STC. This is achieved by considering its internal functioning as a black box where only its input–output measurements are available in the form of frequency response data (FRD), generated by running a free stand-alone Plecs® software package. As this software has the ability to perfectly model the behavior of boost DC-DC converters, previously connected by variable resistive loads, it is possible thanks to the existence of equivalent electrical circuits, available in its own library. Unfortunately, this library lacks an equivalent circuit for the KC200GT photovoltaic panel where its design is needed through evaluating its current–voltage characteristics. The resulting global model is then simulated in the modified Plecs® software, providing the desired FRDs. These are used to estimate the parameters of the proposed linear model, which then used for tuning the PID controller. Here, this controller is combined with the standard Maximum Power Point Tracking (MPPT) strategy based on the direct implementation of the Incremental Conductance (INC) algorithm, highlighting therefore the proposed improved INC-MPPT strategy. It perfectly overcomes the ripple problems encountered in some electrical components of the solar system when controlled by the standard INC-MPPT strategy. As the proposed improvements depend on the model accuracy, the main contribution of this paper lies therefore on the necessary steps to design this proposed small-signal model. [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.)

In the static stability analysis of the grid-connected photovoltaic (PV) generation and energy storage (ES) system, the grid-side is often simplified using an infinite busbar equivalent, which streamlines the analysis but neglects the dynamic characteristics of the grid, leading to certain inaccuracies in the results. Furthermore, the control parameter design does not consider the coupling relationships among parameters, resulting in arbitrary values and the inability to achieve overall optimality. To address these issues, this paper presents a comprehensive parameter optimization method for the oscillation characteristics of grid-connected PV generation and ES systems in various frequency ranges. Firstly, a detailed modeling of the grid-connected PV generation and ES system is conducted, resulting in the derivation of the system's small-signal model. This study investigates the impact of parameters related to PV arrays, ES units, and the virtual synchronous generator (VSG) on the system's characteristic roots using participation factors, sensitivity analysis, and eigenvalue root trajectories. Subsequently, based on the analysis of system root trajectories and the Particle Swarm Optimization (PSO) algorithm, a holistic parameter optimization design method for the system's oscillation modes is proposed, and the parameter optimization results are obtained. Finally, the accuracy of the theoretical analysis is validated through perturbation testing using both Matlab/Simulink models and the small-signal model. [ABSTRACT FROM AUTHOR]

Non-quasi-static small-signal models are essential for exploring the high-frequency (HF) behavior of the FinFET. In this paper, we propose a modified small-signal model for a multi-fin (MF) FinFET to extract the intrinsic and extrinsic parameters using Y-parameters extracted from TCAD. The gate resistance plays a significant role in optimizing the HF behavior with the varying numbers of fins in the MF configuration. We also test the model's accuracy with increasing temperature up to 425 K. Using well-calibrated TCAD models, we further analyze the analog and linearity figures of merit, including cutoff frequency (f T ), the maximum frequency of oscillation (f max ), transconductance (g m ) and higher-order derivatives such as g m 2 , g m 3 , VIP 2 , and VIP 3 . Thus, the behavior of intrinsic and extrinsic parasitic resistance and capacitance is worth exploring to determine the device operation in the frequency range of >100 GHz. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering 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.)

AC-DC hybrid spot networks contain strong redundancy. It further enhances the power supply reliability of spot network systems and is helpful for the integration of distributed energy resources (DERs). However, there are few stability analysis studies of AC-DC hybrid spot networks. Focusing on the AC-DC hybrid spot network, which adopts a unified control strategy, its stability problem is studied in this article. A mathematical model of each unit is constructed for this system. Via linearization of spatial state equations, a small-signal model of the AC-DC hybrid spot network is established under different operation modes. Moreover, corresponding eigenvalue criteria are obtained, and the stability problem is analyzed by using the eigenvalue analysis method when the AC-DC hybrid spot network is subjected to a slight interference under the unified control strategy. The dominant factors of each eigenvalue are studied. Based on this approach, the influence of different control parameters on the system stability is demonstrated. Then, the control parameters are selected for control optimization. A simulation model is constructed in MATLAB/Simulink software. The eigenvalue criteria and simulation results validate the applicability of the small-signal model constructed in this article and the effectiveness of the optimization conclusions.

VSG is a pivotal control strategy for GFM, designed to enhance the damping and inertia of power systems, thereby bolstering their stability. Despite its benefits, VSG can induce a QEO due to dynamic interactions between the GFM and the power system. This QEO, is different from control issues, contrasts with the EO associated with conventional SG, which is rooted in electromechanical factors. To address this phenomenon, the influence mechanism of VSG on QEO of the system is studied. First, a comprehensive control model for the VSG is established and its efficacy in providing damping and inertia is assessed. Subsequently, a small-signal model for the VSG when connected to the grid is developed. Utilizing this model, the system’s characteristic roots and the trajectories of principal state variables, elucidating the impact of VSG control parameters on QEO are analyzed. The validity of the models and the underlying mechanisms are confirmed through extensive simulations. Furthermore, for the key problems that need to be solved urgently in the application of VSG in power system with renewable energy, further thinkings are prospected.

In this article, a small-signal model of grid-forming (GFM) converters that takes into account the presence of ac shunt capacitors in the power grid is presented. It is revealed that the inclusion of shunt ac capacitors in GFM converters leads to the emergence of two new resonant peaks in the loop gain of the active power control (APC) loop, in addition to the fundamental-frequency resonant peak that was previously identified in literature. Further analysis based on the equivalent APC considering P/Q coupling has confirmed the same destabilization effect of ac shunt capacitors by introducing two extra resonant peaks. Based on the insight, it is suggested that the active damping control needs to be adapted to effectively dampen all three resonant peaks to ensure the stable operation of GFM converters. Finally, simulations and real-time simulations are carried out to corroborate the theoretical findings.

In electric vehicles (EVs), the small size of the dc link capacitor results in significant voltage deviations when there are changes in load or uncertain fluctuations from the power resources. This causes a decline in voltage quality. To address the issue of low inertia, this study suggests the use of a fast-responding energy storage system, such as a supercapacitor (SC), which can replicate inertial responses through a specified control algorithm. A virtual capacitor and a virtual conductance are presented in this paper, which are implemented in the inner loop control, specifically the current loop control of SC, to effectively emulate inertia and damping and improves the battery lifetime by reducing the rate of charge and discharge. To assess the stability of the EV, a comprehensive small-signal model is developed, and the acceptable range of inertia response parameters is determined through eigenvalues analysis of the system. Numerical simulations are conducted to demonstrate the performance of the proposed control structure.

The given power and grid frequency disturbances can cause transient oscillations and steady-state deviations in the output power of a virtual synchronous generator (VSG), which can be effectively addressed by adding transient damping. However, this approach may result in significant power overshoot. This article proposes an improved VSG control strategy based on transient electromagnetic power feedback compensation and a small-signal model reduction scheme. Firstly, the grid-connected active closed-loop small-signal models of typical VSG control and transient damping VSG control are established, respectively. The transient oscillation suppression mechanism of active power is revealed through root locus and frequency response analyses, and the power overshoot characteristics of the two control strategies are analysed by combining them with the system of zero points. Secondly, the active transient feedback compensation method and the small-signal model reduction design method are introduced in detail. Finally, comparative analysis experiments are conducted using the Matlab/Simulink and hardware-in-the-loop experimental platform. It is verified that the proposed control strategy can suppress transient oscillations in active power, prevent steady-state deviations, and effectively mitigate the power overshoot problem of the system.

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of 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 Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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 Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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.)

This paper presents a fifth-order generalized integrator (FOGI) as an orthogonal signal generator (OSG) to obtain a grid synchronization signal for a double-stage single-phase grid-interfaced photovoltaic supply system (GIPVSS). The proposed GIPVSS consists of a single-ended primary inductor converter (SEPIC) and a H-bridge voltage source converter (HBVSC) to transfer solar power to the grid system. The SEPIC controls maximum power delivery (MPD) from the Photovoltaic (PV) array and feeds that power to the grid via an HBVSC. In this study, all energy storage elements (inductors and capacitors) of SEPIC are considered with their effective series resistance (ESR). The dynamic modeling of SEPIC is obtained using a small signal analysis. The control of VSC allows harmonics' mitigation and power factor improvements. A FOGI and a second-order adaptive filtering approach are used in controling VSC. The FOGI is used to obtain a grid synchronization signal from sensed grid voltage under disturbances. The second-order adaptive filtering approach is used to obtain an active load current component. The comparative analysis of FOGI with other reported algorithms is carried out under harmonics in sensed grid voltage. The effectiveness of the proposed system and its control is validated in a laboratory prototype using a Launch Pad TMS320F28379D digital signal processor (DSP). [ABSTRACT FROM AUTHOR]

In electric vehicles (EVs), the small size of the dc link capacitor results in significant voltage deviations when there are changes in load or uncertain fluctuations from the power resources. This causes a decline in voltage quality. To address the issue of low inertia, this study suggests the use of a fast-responding energy storage system, such as a supercapacitor (SC), which can replicate inertial responses through a specified control algorithm. A virtual capacitor and a virtual conductance are presented in this paper, which are implemented in the inner loop control, specifically the current loop control of SC, to effectively emulate inertia and damping and improves the battery lifetime by reducing the rate of charge and discharge. To assess the stability of the EV, a comprehensive smallsignal model is developed, and the acceptable range of inertia response parameters is determined through eigenvalues analysis of the system. Numerical simulations are conducted to demonstrate the performance of the proposed control structure. [ABSTRACT FROM AUTHOR]

In this paper, a new Buck-Boost converter with coupled inductor that can eliminate right-half-plane (RHP) zeros is proposed. The steady-state model and small-signal model of the proposed Buck-Boost converter in continuous conduction mode (CCM) are established and analysed, and its control-to-output voltage transfer function is obtained. The condition for this proposed converter to eliminate RHP zeros is derived based on the Mason formula. The comparisons among the other extant four Buck-Boost converters and the proposed Buck-Boost converter are carried out, and it shows that the proposed Buck-Boost converter has the advantage of eliminating RHP zeros. Finally, some simulations and circuit experiments are presented for confirmation. [ABSTRACT FROM AUTHOR]

This article proposes a new extraction technique to determine the GaN HEMT extrinsic capacitances over a wide frequency band on two different substrates, namely, the silicon and the silicon carbide. The proposed technique, which uses a small‐signal model equivalent circuit under cold pinch‐off operating conditions, is based on the proposal of a new small‐signal equivalent circuit which allows extracting first the extrinsic resistances and inductances. Then comes the extraction of extrinsic capacitances at high frequency. The proposed approach achieved successful results through close agreement with measured data up to 60 GHz. [ABSTRACT FROM AUTHOR]

The closed-loop control of coupled inductor-based high-step-up-gain boost converter in continuous conduction mode has non-minimum phase behavior due to right-half-plane (RHP) zero. The crossover frequency of the closed loop should be designed to be less than RHP zero for stable converter operation. Hence, the converter has lower bandwidth (BW) and a poor dynamic response. Combining the interleaving technique with coupled inductor boost converter (CIBC) can improve the dynamic response. As the number of interleaved phases at the input side of CIBC increases, RHP zero moves toward higher frequency. Thus, it improves the closed-loop BW. In addition, it is simple and easy to design closed loop of interleaved coupled inductor boost converter (ICIBC). Moreover, an interleaved operation reduces the size of inductance required for the same ripple in input current and reduces voltage dip during a step change in load. This paper presents a small-signal model of a multi-phase ICIBC to verify the claim. The laboratory prototype of CIBC and three-phase ICIBC is implemented to boost 24 V to 100 V at power level of 300 W. The experimental results of CIBC and three-phase ICIBC are obtained for a change in load from 150 to 300 W to validate results of small-signal model. A single-loop voltage mode control with Type II controller is implemented to regulate output voltage and to achieve desired dynamic performance of three-phase ICIBC for a load disturbance. [ABSTRACT FROM AUTHOR]

This paper focuses on fractional-order modeling and the design of a robust speed controller for a nonlinear system. An induction motor (IM), widely used in Electrical Vehicles (EVs), is preferred in this study as a well-known nonlinear system. The major challenge in designing a robust speed controller for IM is the insufficiency of the machine model due to inherent machine dynamics. Fractional calculus is employed to model the IM using the small-signal method, accounting for model uncertainties. In this context, experimental data is approximated using a fractional-order small-signal transfer function. Consequently, a mixed sensitivity problem is formulated with fractional-order weighting functions. The primary advantage of these weighting functions is their greater flexibility in solving the mixed sensitivity problem by involving more coefficients. Hereby, three robust speed controllers are designed using the PID toolkit of the Matlab program and solving the H∞ mixed sensitivity problem, respectively. The novelty and contribution of the proposed method lie in maintaining the closed-loop response within a secure margin determined by fractional weighting functions while addressing the controller design. After evaluating the robust speed controllers with Bode diagrams, it is proven that all the designed controllers meet the desired nominal performance and robustness criteria. Subsequently, real-time implementations of the designed controllers are performed using the dsPIC microcontroller unit. Experimental results confirm that the designed H∞-based fractional-order proportional-integral-derivative (FOPID) controller performs well in terms of tracking dynamics, exhibits robustness against load disturbances, and effectively suppresses sensor noise compared to the robust PID and fixed-structured H∞ controller. [ABSTRACT FROM AUTHOR]

LLC resonant converters have been widely used in DC/DC conversion because of their high efficiency. However, the converters are highly nonlinear, making it hard to use typical linear control methods. This paper proposes a disturbance-observer-based control approach, which achieves better performance compared with the conventional PI controller. First, according to the extended describing function (EDF) method, the small-signal model of the phase-shift LLC resonant converter is established, which is further simplified to a third-order system. Then, the disturbance-observer-based control is presented, which incorporates a disturbance observer (Dob) to estimate the uncertain effects resulting from external disturbances, circuit parameters variation and model mismatch, and compensate for them in a feedforward way. The main advantage of this control structure is that it can improve the stability and dynamic response simultaneously, where the Dob optimizes the dynamic responses and the PI controller is designed to satisfy the stability requirement. Finally, a 600 W simulation model is built in MATLAB/Simulink to verify the proposed control method, whose superiority over the classic PI controller is proved by the simulation results.

The advanced modeling and estimation of overall system dynamics play a vital role in electric vehicles (EVs), as the selection of components in the powertrain and prediction of performance are the key market qualifiers. The state-space averaged model and small-signal transfer function model are useful for assessing long-term behavior in system-level analysis and for designing the controller parameters, respectively. Both models take less computation time but ignore the high-frequency switching dynamics. Therefore, these two models could be impractical for the development and testing of EV prototypes. On the other hand, the multi-domain model in available simulation tools gives in-depth information about the short-term behavior and loss analysis of power electronic devices in each subsystem, considering the switching dynamics in a long computation time. In this paper, a general mathematical framework for the dynamical analysis of complete EVs is presented using a unified, switched nonlinear model. This equation-based model runs faster than the available module-based simulation tools. Two other models, namely the time domain state-space averaged model and frequency domain small-signal transfer function model, are also developed from the switched nonlinear model for the analysis with less computation time. The design and performance of an EV with two different motors and its controllers are evaluated using the general mathematical framework. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to the efficient extraction of parasitic resistances in high electron mobility transistors (HEMTs). The study reveals that the gate resistance value can be accurately determined under specific forward gate bias conditions (Vg = 1.0 V), although the gate resistance value becomes unreliable beyond this threshold (Vg > 1.0 V) due to potential damage to the Schottky contact. Furthermore, by examining the characteristics of the device under a cold-FET bias condition (Vds = 0 V), a linear correlation between the gate and drain current is identified, enabling an estimation of the interdependence between the drain and source resistance using the proposed method. The estimation of parasitic pad capacitance (Cpg and Cpd) from Dambrine's model is refined by incorporating the depletion layer capacitance on the gate side during the pinch-off condition. To validate the accuracy of the extracted parasitic capacitance and resistance values obtained from the new method, small-signal modeling is performed on a diverse range of measured devices. [ABSTRACT FROM AUTHOR]

This paper presents a detailed derivation of the small-signal model and components design considerations for the Quasi-Y-Source inverter. The design methodology is based on the converter steady-state operation, considering the impedance network inductor and capacitor voltage and charge balances, respectively. Moreover, the additional design criteria for component selection, considering control constraints and performance compromise, are given by parametric variation analysis based on converter dynamic response. The small-signal model and transfer functions are obtained using a state-space averaged model, including converter non-ideal characteristics given by equivalent-series resistances (ESR), which makes possible the proposition of different control strategies, using both single or multi-loop schemes. To demonstrate the usefulness of the proposed small-signal model, a DSP-based single-loop type-II PI control strategy is used in which the peak DC-link voltage is indirectly controlled through the measurement of the impedance network capacitor voltage. The controller and converter performances are verified with simulation and experimental results and successfully confirm the validity of the proposed dynamic model. Finally, the obtained results are validated with a built small-scale three-phase/three-wire inverter prototype. [ABSTRACT FROM AUTHOR]

Renewable Energy Sources (RES) are widely used worldwide due to their positive effect on the environment, being sustainable, low cost, and controllable. The power generated from RESs must be configured to interface and perfectly synchronize with the grid by using Power Electronics Converters (PEC). A Phase-Locked Loop (PLL) is one of the most popular synchronization techniques used due to its speed and robustness. A growing issue that results in oscillations in the estimated fundamental grid phase, frequency, and voltage amplitude is the DC-offset in the input of the PLL. This study was developed to eliminate the DC-offset in the single-phase grid synchronization using Delay Signal Cancellation (DSC) and a fixed-length Transfer Delay (TD)-based PLL. Then, the small-signal model, stability analysis, and selection of controller gains were discussed. The proposed PLL was simulated using MATLAB/Simulink. Moreover, to evaluate the proposed method, several scenarios were developed in order to compare it with other powerful PLLs in terms of performance indicators such as settling time, frequency, and phase error. As a result, the proposed PLL has the fastest dynamic response, completely rejects the DC-offset effect, and fully synchronizes with the electrical grid. [ABSTRACT FROM AUTHOR]

A high gain two-phase interleaved coupled inductor-based DC-DC converter step-up low input voltage sources like PV array and fuel cell in distribution generation system (DGS). The converter operates for a wide range of load changes when it is part of DGS. At light load, the converter operates in discontinuous conduction mode (DCM). A small-signal model (SSM) is required in both continuous conduction mode (CCM) and DCM to know the complete dynamic behavior of the converter. Steady-state and small-signal analysis of the two-phase interleaved coupled inductor boost converter (ICIBC) is quite complex when the converter operates in DCM. This paper presents the complete derivation of SSM of a two-phase ICIBC-based high step-up gain converter in DCM. The conditions of the converter operating in DCM are discussed. The small-signal model of two-phase ICIBC is derived using the state-space averaging method. The control-to-output voltage transfer function and steady-state voltage gain of the two-phase ICIBC are derived. When the converter operates in DCM, it eliminates the right half plane zero from the control-to-output voltage transfer function. Thus, it improves bandwidth and stability margin. Thus, single loop voltage control is sufficient to achieve regulated output voltage with faster response for all operating ranges of DCM. The laboratory prototype of two-phase ICIBC is implemented to step-up 24 V to 100 V at a power level of 300 W. The experimental results of two-phase ICIBC are obtained in DCM and CCM with step-change in load to validate the derived small-signal model. [ABSTRACT FROM AUTHOR]

To achieve optimal system performance, it’s recommended to operate an LLC resonant converter at its resonant frequency. However, in mass production, the resonant parameters of different products can deviate significantly. This means that we need to actively track the resonant frequency during practical usage. To address this issue, this paper presents a novel automatic control scheme for LLC converter that tracks the resonant frequency. The proposed control scheme is based on an accurate small-signal model, and an extended state observer which provides small-signal characteristics at the operating frequency. The controller checks the voltage gain of the converter and combines large-signal with small-signal models to control the LLC converter effectively. Compared to conventional automatic resonant frequency tracking (ARFT) control schemes, the proposed control scheme is easier to implement and requires fewer sensors. Experimental results demonstrate its effectiveness in tracking the resonant frequency. In summary, this manuscript proposes an effective ARFT control scheme for LLC converter that can track the resonant frequency with reduced sensors and is easier to implement.

Voltage source converter based high-voltage direct current (VSC-HVDC) transmission technology has been extensively employed in power systems with a high penetration of renewable energy resources. However, connecting a voltage source converter (VSC) to an AC weak grid may cause the converter system to become unstable. In this paper, a phase-shift phase-locked loop (PS-PLL) is proposed wherein a back electromotive force (BEMF) observer is added to the conventional phase-locked loop (PLL). The BEMF observer is used to observe the voltage of the infinite grid in the stationary $\alpha\beta$ frame, which avoids the problem of inaccurate observations of the grid voltage in the $dq$ frame that are caused by the output phase angle errors of the PLL. The VSC using the PS-PLL can operate as if it is facing a strong grid, thus enhancing the stability of the VSC-HVDC system. The proposed PS-PLL only needs to be properly modified on the basis of a traditional PLL, which makes it easy to implement. In addition, because it is difficult to obtain the exact impedance of the grid, the influence of short-circuit ratio (SCR) estimation errors on the performance of the PS-PLL is also studied. The effectiveness of the proposed PS-PLL is verified by the small-signal stability analysis and time-domain simulation.

The low-frequency oscillation (LFO) problem of photovoltaic (PV) grid-connected systems has been a critical concern for safe operation, whereas the impact of dc-side components of PV plants are always ignored and single-stage PV plant is used. This paper performs a comprehensive analysis of the LFOs in the two-stage PV grid-connected system. The complete small-signal model of the two-stage PV system is built. On this basis, the LFO modes and high-frequency oscillation (HFO) modes are calculated and related participating components are determined. Then, the impact of key parameters on the LFO characteristics is investigated with the root locus analysis. The theoretical analysis is verified through PSCAD/EMTDC simulations.

The current small-signal stability analysis and parameter selection of converters that mimic synchronous generators usually ignore some dynamic characteristics and the changes of steady-state operating points for simplicity. It could only judge the trend of small-signal stability and the analysis result was not accurate enough. Firstly, this paper established a small-signal model that mimics synchronous generators by connecting two isolated converters in parallel, the eigenvalues of the system were calculated and some of their physical meanings were obtained. Following that, in order to demonstrate the relationship of eigenvalues and state variables, the participation factor was calculated. Considering that, there will be some variability of the operating points with the parameters variation. As a function of the system settings, numerous root locus plots were created. For individual eigenvalue close to the real axis, in order to reveal the contribution of different parameters to the oscillation patterns, a separate eigenvalue sensitivity analysis was performed. The rules of the influence are essential to guide the design of parameters and their optimization of isolated converters connected in parallel that mimic synchronous generators.

Interleaved DC–DC converters have significant advantages in improving the capability of power converters, and coupling the filtering inductor of the converter could further increase the power density. However, existing modeling and controller designs are complex and require multiple sensors to be involved in the control, which is not conducive to engineering implementation and reducing production costs. In view of this problem, taking a two-phase interleaved boost converter with a coupled inductor as an example, the small-signal models of the converter are derived for the resistive load and constant voltage source load using the state averaging method. The total inductor current is engaged in the control as a feedback signal, avoiding the coupling effect of the inductor on increasing the complexity of the controller. Based on this, a double closed-loop controller is designed, and a prototype of the two-phase interleaved boost converter with coupled inductor is built. Only one current sensor and one voltage sensor are required to participate in the control. The effectiveness of the analysis and design in this paper are verified by experiments. [ABSTRACT FROM AUTHOR]

This paper presents a new linear model design including the KC200GT photovoltaic generator GPV panel, DC-DC boost converter, and resistive load. The small-signal principle is indeed applied to the configuration connecting these three devices that are previously developed graphically using the M a t l a b ® / S i m u l i n k software package. This new model design is established through a set of proposed steps, providing the first contribution of this paper. A new voltage proportional-integral-derivative (PID) controller is synthesized based on the previous linear small-signal model. The controller parameters are computed by proposing a reference open-loop system and using the frequency identification approach, providing the second contribution of this paper. The resulting PID controller is combined with the classical perturb and observe (P &O) algorithm where its fill factor (FF) and its reference tracking dynamic are significantly improved. Improving these two performances for a sudden change of both climatic conditions, i.e., absolute temperature and solar irradiance, constitutes another contribution of this paper. Given improving the previous two performances, the maximum power point tracking (MPPT) scheme with oscillation free tracking of the desired MPP is established for conventional and improved P &O algorithms using S i m p o w e r ® system libraries of the M a t l a b ® / S i m u l i n k environment. The given simulation tests confirm the effectiveness of the proposed P &O-MPPT control strategy in terms of reference tracking accuracy, rise and settling times, and solving the ripple issue that occurred in the DC-DC boost converter output current. [ABSTRACT FROM AUTHOR]

Distributed Generators (DG) systems based on Renewable Energy Sources (RES) such as hydro, wind, and solar power plants have been spread widely due to their lower cost and the advanced capability of connecting them with the grid. The power generated from the DG must be shaped to be interfaced with the grid employing power electronics converters. The grid-connected power electronics converters must be synchronized with the grid (i.e., the same fundamental component of the grid frequency, phase, amplitude, and sequence). Synchronization techniques are employed to achieve accurate and fast grid synchronization between the converter and the grid. The existence of (DC-offset) in the input of Phase Locked Loop (PLL) caused synchronization problems as it causes oscillations in the estimated fundamental grid phase, frequency, and amplitude. In addition, the closed-loop system stability can be affected. This work proposes a simple technique for grid synchronization based on PLL with a phase angle correction. The proposed method was developed using Transfer Delay (TD) and Delay Signal Cancelation (DSC) operators; then, the small single model and stability analysis was employed. Several scenarios were developed to compare the proposed method with previous methods using MATLAB/Simulink tool. The scenarios involve introducing phase jumps, DC offsets, and amplitude changes to the grid voltage. Additionally, the grid frequency was also changed. The results show that the proposed PLL can solved the DC-offset problem using any delay time and fully synchronized with the grid. Moreover, the proposed PLL has the fastest dynamic response and shortest synchronization time over the other methods from literature.