In this paper, the idea of operating an inverter to mimic a synchronous generator (SG) is motivated and developed. We call the inverters that are operated in this way synchronverters. Using synchronverters, the well-established theory/algorithms used to control SGs can still be used in power systems where a significant proportion of the generating capacity is inverter-based. We describe the dynamics, implementation, and operation of synchronverters. The real and reactive power delivered by synchronverters connected in parallel and operated as generators can be automatically shared using the well-known frequency- and voltage-drooping mechanisms. Synchronverters can be easily operated also in island mode, and hence, they provide an ideal solution for microgrids or smart grids. Both simulation and experimental results are given to verify the idea.

针对分布式电源并网逆变器的虚拟同步发电机控制策略及其在微电网中的应用进行研究。建立并网逆变器用虚拟同步发电机控制方案的数学模型，研究基于虚拟转矩和虚拟励磁的并网有功、无功调节方案，定量分析系统模型参数摄动对并网功率跟踪的影响，详细分析惯性和阻尼参数的整定方法，提出一种基于锁相环的虚拟同步发电机离/并网无缝切换控制策略，可模拟同步发电机的准同期并列装置。最后，针对一个典型微电网系统，利用PSCAD/EMTDC的仿真结果和一台50 kVA样机的实验结果验证所提控制策略的正确性和有效性。结果表明，所提的并网功率调节控制策略具有较好的有功、无功跟踪性能；同时，还能很好地为系统提供惯性和阻尼，提高系统稳定性，此外，还能满足微电网不同运行模式之间的无缝切换。

针对分布式电源并网逆变器的虚拟同步发电机控制策略及其在微电网中的应用进行研究。建立并网逆变器用虚拟同步发电机控制方案的数学模型，研究基于虚拟转矩和虚拟励磁的并网有功、无功调节方案，定量分析系统模型参数摄动对并网功率跟踪的影响，详细分析惯性和阻尼参数的整定方法，提出一种基于锁相环的虚拟同步发电机离/并网无缝切换控制策略，可模拟同步发电机的准同期并列装置。最后，针对一个典型微电网系统，利用PSCAD/EMTDC的仿真结果和一台50 kVA样机的实验结果验证所提控制策略的正确性和有效性。结果表明，所提的并网功率调节控制策略具有较好的有功、无功跟踪性能；同时，还能很好地为系统提供惯性和阻尼，提高系统稳定性，此外，还能满足微电网不同运行模式之间的无缝切换。

To improve the contribution of distributed inverter based on power electronic interface to the required inertia of power system for stability,a novel overall control strategy based on virtual synchronous generator (VSG) is designed. The outside control of distributed inverter is constructed by using synchronous generator’s rotor motion equation,primary frequency regulation feature and the delay characteristic of reactive power regulation. The proportional resonant controller which has better tracking performance is adopted in the bottom control. Then the small-signal models of inverter with grid-connected and autonomous working mode are established. The impact of main control parameters on system stability and dynamic response is analyzed according to the state matrix eigenvalue and sensitivity calculation. Correctness of the proposed methods is verified by Digital simulation and practical experiment. The results show that the distributed inverter can work in two modes of grid-connected and autonomous. And the change of reactive power has little influence on active power. The established small-signal model can be used for system stability analysis and related control parameters optimal design.

To improve the contribution of distributed inverter based on power electronic interface to the required inertia of power system for stability,a novel overall control strategy based on virtual synchronous generator (VSG) is designed. The outside control of distributed inverter is constructed by using synchronous generator’s rotor motion equation,primary frequency regulation feature and the delay characteristic of reactive power regulation. The proportional resonant controller which has better tracking performance is adopted in the bottom control. Then the small-signal models of inverter with grid-connected and autonomous working mode are established. The impact of main control parameters on system stability and dynamic response is analyzed according to the state matrix eigenvalue and sensitivity calculation. Correctness of the proposed methods is verified by Digital simulation and practical experiment. The results show that the distributed inverter can work in two modes of grid-connected and autonomous. And the change of reactive power has little influence on active power. The established small-signal model can be used for system stability analysis and related control parameters optimal design.

Microgrid is widely accepted as an effective mean of integrating various distributed energy resources (DERs) through their interface converters to provide electric power of high quality and reliability. These distributed resources interface converters can operate in an autonomous fashion without any communication for enhanced system reliability and reduced complexity. Conventionally, the real power-frequency droop control and the reactive power-voltage magnitude droop are adopted as the decentralized control strategies in these DERs interface converters for the autonomous power sharing operations. However, the reactive power sharing of Q-V droop control often deteriorates due to its dependence on the line impedances. In this paper, a Q-(V) over dot droop control method with (V) over dot restoration mechanism is proposed to improve reactive power sharing. Its operation principle and control method are explained and analyzed. Simulation and experimental results are presented to validate the effectiveness of the proposed method.

To improve the reliability of commutation in two stage matrix converter (TSMC),a novel carrier-based modulation scheme was proposed. In rectifier,the double modulation waves were used to extent zero current commutation time,so the problems of interruption of commutation and distortion in input current caused by narrow pulses were solved. In inverter,the 60#x000b0;clamped modulation functions were taken as modulation waves to reduce the counts of commutation by one third. In cooperating modulation,the isosceles triangular waves during two adjacent carrier periods and the trapezoidal waves in one carrier period were respectively taken as carrier waves of rectifier and inverter to keep switching states same,so that the commutation processes in a period of transition from one carrier period to another were avoided and the reliability was enhanced more. The relationship between minimum commutation time of rectifier and modulation index of inverter was also analyzed. At last,an experimental prototype was designed. Experimental results compare with two existing carrier-based modulation strategies to verify the correctness and superiority of proposed modulation strategy.

To improve the reliability of commutation in two stage matrix converter (TSMC),a novel carrier-based modulation scheme was proposed. In rectifier,the double modulation waves were used to extent zero current commutation time,so the problems of interruption of commutation and distortion in input current caused by narrow pulses were solved. In inverter,the 60#x000b0;clamped modulation functions were taken as modulation waves to reduce the counts of commutation by one third. In cooperating modulation,the isosceles triangular waves during two adjacent carrier periods and the trapezoidal waves in one carrier period were respectively taken as carrier waves of rectifier and inverter to keep switching states same,so that the commutation processes in a period of transition from one carrier period to another were avoided and the reliability was enhanced more. The relationship between minimum commutation time of rectifier and modulation index of inverter was also analyzed. At last,an experimental prototype was designed. Experimental results compare with two existing carrier-based modulation strategies to verify the correctness and superiority of proposed modulation strategy.