Research On Damping Characteristics And Inertia Simulation Of Distributed Power Supply Under Virtual Synchronous Generator Control

The traditional thermal power units in power systems are extremely unfriendly to the environment.At present,countries around the world are vigorously developing clean and environmentally-friendly distributed power sources to replace traditional units in the power systems.Most distributed power sources need to be connected to the power grid through power electronic converters.Because the power electronic converter does not have a mechanical energy storage structure,it cannot provide inertia support and damping for the power grid like a traditional synchronous generator.In the early stage of the development of distributed power,its small power generation capacity was not enough to affect the power system.However,as the penetration of distributed power continues to increase,the instability problems caused by the lack of inertia in power systems will become more prominent.The virtual synchronous generator control technology can make distributed power sources simulate the external characteristics of synchronous generators,thus becoming a new method to solve the problem of lack of inertia in power systems.This paper takes a photovoltaic virtual synchronous generator with the energy storage installed on AC side as an example.The virtual synchronous control technology is used to control the energy storage grid-connected inverter to form an energy storage virtual synchronous generator,which making conventional photovoltaic power plants to have the functions of inertia support and primary frequency regulation.This paper first briefly analyzes the energy storage battery model of the energy storage virtual synchronous generator,the structure and parameter design of the bidirectional DC converter.Then it focuses on the control principle of the virtual synchronous generator control technology and explains its physical correspondence with the synchronous generator.Starting from the analysis of the active,reactive and inner loop control structures of the virtual synchronous generator control.The small-signal model of the virtual synchronous generator was derived,and the design rules for the damping coefficient and rotational inertia of the virtual synchronous generator were determined.With reference to the actual operating conditions of the energy storage device,different control parameters in the two operating conditions are designed and a ping-pong control strategy of virtual synchronous generator parameters is formed.Subsequently,a grid-connected photovoltaic virtual synchronous generator simulation model was built in MATLAB/Simulink to verify the support of photovoltaic virtual synchronous generators on the grid frequency and the effect of different control parameters on the performance of virtual synchronous generators,and the effectiveness of the virtual synchronous generator parameters ping-pong control strategy is proved.Finally,this paper establishes a hardware-in-the-loop experimental platform for grid-connected photovoltaic virtual synchronous generators with the core of RT-LAB simulator.The photovoltaic power generation and its control part,energy storage and grid model are converted into code and it is imported in the RT-LAB simulator.The virtual synchronous generator control program is imported in the DSP control board.The RT-LAB emulator and the DSP control board exchange data through I/O port with custom communication protocol.The effectiveness and implementability of the proposed control strategy in this paper are verified.At the same time,it also verifies the intuitive of the hardware-in-the-loop experimental platform established in this paper and the universality of other experiments.