Research On Operation Control Strategy Of Islanded Microgrid Based On Virtual Synchronous Generator

Microgrid is an effective way to exert the efficiency of distributed generation(DG),and an important means to solve the problem of large-scale renewable energy access in the smart grid system in the future.It has huge social and economic benefits.Among the many control methods of microgrid,virtual synchronous generator(VSG)technology has been widely used.However,the essence of the virtual synchronous generator control algorithm is still based on the traditional droop characteristics.Therefore,there are still a series of common problems such as low power distribution accuracy and power circulation when multiple VSGs are connected in parallel during operation.At the same time,the power and frequency oscillation caused by related parameters such as virtual inertia and damping coefficient in the VSG algorithm need to be further studied.In view of the above problems,the author has done the following four aspects of the research on the operation control strategy of islanded microgrid based on virtual synchronous generator:Firstly,the research background and significance of microgrid and virtual synchronous generator control technology are analyzed by reading relevant domestic and foreign references and research results in this field,and the current research status in this field at home and abroad is summarized,and the deficiencies of virtual synchronous generator technology research are summarized,and the main research work of the article is summarized.Secondly,the control principle and structure of the virtual synchronous generator are analyzed and designed.Based on the analysis of the working principle and topological structure of the traditional synchronous generator(SG),a simplified ideal and mathematical model is established,and the VSG control algorithm is designed,including the principle analysis and design of excitation controller and frequency modulation controller.And a parallel operation architecture of multiple VSGs based on low bandwidth communication is established.Thirdly,in view of the system frequency and power oscillation caused by load fluctuations in the process of virtual synchronous generator control,a power-frequency oscillation suppression strategy based on fuzzy inference system(FIS)is proposed.By setting the fuzzy logic rules reasonably and applying the fuzzy logic algorithm to the VSG control unit,the dynamic adjustment of the moment of inertia and the damping coefficient in the VSG algorithm is realized,and the coordinated control of the two is realized.The simulation verifies that the improved VSG algorithm has a significant effect on power frequency oscillation suppression,reduces the overshoot of active power and frequency,shortens the adjustment time,which is conducive to the stability of frequency and power.Finally,in view of the difference in line impedance that may cause local voltage deviations,which may cause lower power distribution accuracy and bus voltage drops under traditional VSG control,an active-reactive power allocation strategy in multi-source islanded microgrid based on particle swarm optimization(PSO)is proposed.On the basis of the basic PSO,the adaptive weighting factor is adopted to improve the optimization efficiency of the algorithm,and by designing a reasonable fitness function,the improved PSO algorithm is applied to the VSG control unit to realize the adaptive adjustment of the frequency and voltage modulation coefficient in the VSG control.Simulations and experiments verify that the improved VSG control algorithm can improve the distribution accuracy of active and reactive power effectively while ensuring the bus voltage and system frequency.