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Brushless doubly‐fed air‐core pulse alternator (BDAPA) is a new type of pulse alternator. It does not need a brush and slip ring, improving the reliability of the system. Moreover, the field winding and rotor winding have good compensation effect, which can significantly improve the discharge performance of the pulse alternator. As a high‐power pulse power supply, BDAPA must have a set of corresponding excitation power supplies to control its excitation. Pulse alternator and excitation power supply constitute the pulse alternator power supply system. The excitation power supply of pulse alternator usually adopts a pulse capacitor, the field winding of pulse alternator is excited by the pre‐charged capacitor before the pulse alternator discharges the load. After discharging, the excitation capacitor must be charged again before the next work of pulse alternator. This requires an additional set of DC power supply to charge the excitation capacitor. It not only increases the volume of the whole system and reduces the energy storage density of the system, but also makes the control of the system more complex. Taking the BDAPA as the research object, this paper proposes a control method with energy feedback, which is combining self‐excitation and separate excitation. Using the inertial energy storage of the pulse alternator and the inductive energy storage of the field winding and rotor winding, the excitation capacitor can be recharged through proper control methods, which can save the DC excitation power supply and improve the energy storage density of the system. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

To determine economic‐efficient and secure generation schedules, unit commitment (UC) with network and stability constraints will play an important role in the electricity market. We define a voltage‐stability‐constrained unit commitment problem taking reactive power limit into account (VSCUC‐QLIM) since the decreasing of synchronous generators may threat the voltage stability of electricity systems. This VSCUC‐QLIM problem is modeled as a mixed‐integer nonlinear programming with equilibrium constraints, which is too complex to be solved directly. Therefore, we apply Benders decomposition to solve this complex problem: the master problem consists of the UC problem to determine the commitment states for generators, and the subproblem consists of the voltage‐stability‐constrained optimal power flow with complementarity constraints problem. However, the subproblem calculation may not converge depending on the commitment states due to the following reasons: (i) any power‐flow solution cannot be obtained or (ii) the voltage stability requirement cannot be satisfied on the commitment state given by the master problem. To deal with these difficulties, two partial problems of the subproblem are added as a pre‐subproblem and post‐subproblem in the proposed method. The combination of these subproblems generate different types of Benders cut depending on the condition. The proposed method was implemented on MATPOWER, and evaluated for daily scheduling on an IEEE six‐bus test system and IEEJ standard WEST10 system. The evaluation results validated the effectiveness of the proposed method from the perspective of economic efficiency and voltage stability. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

For the power system integrated with the doubly‐fed induction generators (DFIGs), the frequency regulation may be provided by the DFIGs in addition to the synchronous generators (SGs). With the model predictive control (MPC), the active power output of the DFIG is adjusted by predicting the system frequency with the dynamic power flow (DPF) algorithm. In this paper, the governor delay of the SGs is included to improve the accuracy of the DPF‐based prediction model. The DPF predicts the frequency response with the desired active power response of the DFIG. To reach the reference with the high accuracy and efficiency, the MPC‐based direct rotor current control is applied to adjust the active power output in coordination with the frequency regulation, forming the proposed hierarchical frequency control strategy. The mechanical transient of the DFIGs involving the shaft and pitch angle system is included in the DPF model to introduce the mechanical constraints of the DFIGs to the MPC. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Compared with traditional power plants, current main stream wind turbines vary in grid connection interfaces, resulting in deficiencies like weak grid voltage and frequency support capability. In order to solve the problem, a synchronous type variable speed wind turbine is proposed in this paper. The wind turbine has the advantages such as the intrinsic properties of maintaining grid voltage and frequency, no harmonic pollution on grid, black start capability. In the wind turbine drive train, an electrically excited synchronous generator is directly coupled to the grid. A power self‐balance type electromagnetic coupling device is used to connect the synchronous generator rotor shaft and a gearbox high speed shaft. The device is composed of a permanent magnet synchronous generator (PMSG), a back‐to‐back converter and an electromagnetic coupler. The converter with small capacity, supplied by the PMSG which is coaxial with the gearbox high speed shaft, is used to apply the electromagnetic torque of the electromagnetic coupler. The matching relationship between the electromagnetic torque and the turbine mechanical torque, and the power flow in the drive train in different wind speeds are analyzed. Control strategies are proposed for the wind turbine normal operation including start, stop, maximum wind power capture, and low voltage ride through (LVRT). Compared with the main stream wind turbines, blade and tower loads can be improved greatly during LVRT. A 2 MW wind turbine model is built in Matlab/Simulink to verify the control strategies proposed and the wind turbine excellent LVRT performance. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The problem of shafting torsional vibrations has been increasingly emerging due to the increasing capacity of turbo‐generator and the complexity of power grid. Therefore, how to reduce the torsional vibration of the turbo‐generator shaft and improve the stability of the power system has become the focus of our research. First, in order to solve the problem and alleviate the torsional vibrations of turbo‐generator shafts, this paper proposed a new shafting structure model of Double‐ended Driving and Dual‐Excited Turbo‐Generator set (DDDETG). A static excitation mode is used for the excitation of the DDDETG and the mechanical power is supplied symmetrically and synchronously from both ends of the generator rotor. Then, in order to improve the output characteristic of the generator and further suppress the torsional vibrations of the turbo‐generator shafts, combined with the nonlinear control design method of partial feedback linearization, a Multi‐Index Nonlinear Coordinated Control (MINCC) strategy for the double‐ended driving and dual‐excited turbo‐generator is proposed to ensure good dynamic and static state performances of each state in the system. Finally, the simulation results on a single‐machine infinite bus system demonstrate the effectiveness of the proposed control strategy. In addition, this paper compares the performance of DDDETG and the traditional Single‐ended Drive and Single‐Excited Turbo Generator (SDSETG), the simulation results show that the restraint effect of the DDDETG structure on shafting torsional vibrations is more obvious under the proposed control strategy. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In order to improve the efficiency and quality of a permanent magnet synchronous generator (PMSG) for vehicles, the parametric model and finite‐element model of the generator are established. The influence of seven structure parameters on three performance parameters is obtained by simulation analysis, and the sensitivity values of the parameters are given. According to the simulation results, it can be seen that the structure design parameters have higher degrees of freedom, and the relationship among parameters is complex. Using three multidimensional functions as test functions, the precision of the fitting method proposed in this paper is compared with that of the traditional methods. The test results show that, compared with the other methods, maximum projection (MaxPro) sampling and the Kriging method can select as fewer samples as possible while guaranteeing the higher fitting precision. Then, the Kriging surrogate model, which reflects the nonlinear relationship between the structure and performance parameters, is established, and the prediction precision of the model is verified. Based on the surrogate model, the performance of the generator with three performance parameters as optimized objects is optimized by use of elitist nondominated sorting genetic algorithm (NSGA‐II), and a Pareto optimal solution set of the objective function is obtained. Three of the optimal solutions are selected for finite‐element verification. The results show that the Kriging surrogate model can provide better global and local prediction between input and output variables. It is further proved that the samples obtained by MaxPro sampling can fully reflect the characteristics of the design space. The optimized objects can be weighed according to the optimal decision based on the results of multiobjective optimization through the Kriging surrogate model. The effectiveness of the optimization method is verified. It is of great engineering significance to improve the performance of generators, and the optimal model obtained by this method has an important reference value for prototype trial production. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper proposes a novel model for the analysis and design of a virtual synchronous generator (VSGs). To enhance the stability in power systems with distributed generators, the concept of VSG has been proposed. The VSG is designed based on the swing equation of a synchronous generator ignoring the dynamics of current flowing through an interconnection reactor. However, responses obtained with actual system are different from those calculated from the model. It implies that the VSG cannot be correctly analyzed and designed by using the conventional model. This paper constructs an accurate VSG model considering the dynamics of current. Moreover, we address the stability analysis of the VSG and reveal a relation between the parameters of VSG controller and the rated power/energy capacity of energy storage systems equipped with the VSG based on the proposed model. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The stability of a power system has always been of concern. Now, wide‐area measurement systems are used widely. In this paper, we focus on supplementary turbine/governor control to enhance the stability of a power system with wide‐area measurement information. An H∞ supplementary turbine/governor controller based on the multi‐agent method is introduced to enhance power system stability. First, the synchronous generator is modeled as a second‐order agent. The information of communication topology and power network topology are used to build the system model and the controller design. Then, a linear output feedback controller is adopted. With a suitable Lyapunov function and by solving the linear matrix inequality, the parameters of the controller are tuned by the H∞ synthesis method. Finally, numerical simulations are presented on a Western Systems Coordinating Council three‐generator nine‐bus power system, validating the proposed design. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The basic design and characteristic analysis of the coreless axial flux permanent magnet synchronous generator (AFPMSG) for small wind power generation are carried out. The prototype is manufactured and tested to verify the designed generator. In addition, to reduce the voltage regulation rate and harmonic content of the generator, the optimal design is carried out on the basis of the original generator. The voltage regulation rate and THD of a coreless AFPMSG using the Halbach permanent magnet array are studied. The effects of different generator parameters such as pole arc coefficient, air gap length, permanent magnet thickness, and number of turns in series per phase on the voltage regulation rate and THD are analyzed when the generator is loaded with pure resistance. Because the various parameters of the generator are affected each other, the Taguchi algorithm was adopted for multi‐objective optimization. The influence proportion of different generator parameters on the voltage regulation rate and THD was analyzed. According to the results, the parameters are reasonably selected to design the generator and improve the performance of the generator. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Because of the significant changes in environmental policies and electric power deregulation in the last decade, a lot of photovoltaic generations (PV) have been and will be installed into the power system in Japan and the ratio of PVs to other synchronous generators will be increased. As a countermeasure against the decrease in the rotational inertia in the whole power system, a virtual synchronous generator (VSG) model control of the PV has so far been proposed. However, the system stabilization effect of the VSG in large‐scale power systems has been unclear. In this paper, a virtual step‐out blocking method of VSG for improving the transient stability is proposed. In addition, the necessity of governor control of VSG in a large‐scale power system is discussed. Finally, the rated kw and kwh capacities of the battery required for realizing the VSG‐model control are evaluated. [ABSTRACT FROM AUTHOR]

Low‐frequency oscillations of a power system can be greatly affected by the fast growth of wind power due to the converter controls. It will result in a hidden danger to the small signal stability of the overall system if the mechanisms behind are not well understood. Therefore, this article aims to reveal the influence of the nonlinear control effects (e.g. phase‐locked loop, PLL) of the wind turbine on the electromechanical oscillations of a nearby synchronous generator (SG). To better perform the mechanistic analysis, a three‐machine study system that can properly reflect the interactions among the wind turbine, the SG, and the infinite bus is established. Then, the frequency domain model of such a system is developed, where the dominant dynamics of the wind turbine controls within the electromechanical time scale are modeled in detail. As a result, an equivalent power‐angle‐like frequency domain model is derived, from which the control effects of the wind turbine on the damping characteristic of the nearby SG can be intuitively revealed. It is shown that the wind turbine with the PV control mode can contribute more damping to the nearby SG than that with the PQ control mode. Moreover, the damping contribution is reduced with increasing bandwidth of controllers and the impact of PLL bandwidth on the SG damping can be negligible. All the mechanistic analyses are verified using time domain simulations in power systems computer aided design/electro magnetic transient in DC system (PSCAD/EMTDC), where a detailed system model is built. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this paper, the transient stability enhancement and voltage regulation of a multimachine power system are investigated taking into account the generator parameter uncertainties. An interval type‐2 Takagi–Sugeno (IT2 T‐S) fuzzy model is proposed to represent the nonlinear plant subject to parameter uncertainties. New basic concepts of the IT2 T‐S fuzzy model are proposed to reduce considerably the number of models adopted. A Lyapunov‐based approach is employed to analyze the stability and the pole placement of the IT2 fuzzy closed‐loop system formed by the IT‐2 T‐S fuzzy model and the IT‐2 fuzzy controller. This approach presents a simple closed mathematical form that provides the possibility to regulate the system under uncertain model parameters with closed‐loop design specifications as linear matrix inequality (LMI)‐based optimization problems without any assumptions about the membership functions. A simulation example is given to illustrate the effectiveness of the proposed IT‐2 fuzzy model‐based control approach. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Virtual synchronous generators composed of an inverter are affected by an over‐current caused by voltage dip and recovery. This letter addresses the current analysis under a symmetrical voltage dip and recovery. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]