Power Distribution Strategy Of Parallel Inverter System Based On Virtual Synchronous Generator

Based on the energy shortage situation,environmental pollution and other problems are increasingly prominent,distributed power generation has been widely focused.As the core of distributed generation system,inverter control technology has always been the focus of research.The capacity of distributed generation system is usually small,and the capacity can be effectively inc reased by parallel connection of inverters.Virtual synchronous generator(VSG)control technology can realize the normal operation of parallel inverter by simulating the stator and rotor characteristics.Therefore,this paper study the parallel inverter system power distribution based on VSG control.Aiming at the problem of stable operation of parallel inverter,the VSG control method is adopted in this paper,virtual speed model and virtual excitation model are designed,and the robust virtual excitation design is used to enhance the reactive power distribution on steady state.The power transmission characteristics of parallel system are derived,a small signal model is established,and the relation between VSG parameter and stability of parallel system is studied,pre-synchronization control strategy is used to realize the integration of system module,and the parameters are adjusted according to the system stability and dynamic performance.Considering the influence of resistive line impedance on power distribution in low-voltage situation,the power coupling mechanism is studied,and the improved power decoupling method of virtual negative impedance is proposed.The reason of current circulation is analyzed,current and power circulation is derived.Based on the inner loop control block diagram,the equivalent output impedance of double-loop control in parallel system is derived,and the influence of inner loop control on the power coupling is studied.Aiming at the problem of voltage drop and unequal distribution of reactive power caused by line impedance,a compensation strategy of terminal voltage is improved,which can improve the output power quality and ensure the equal distribution of reactive power.The impedance measurement method based on pulse disturbance is studied.The power distribution strategy of parallel system with different capacities is derived so that the inverter can be distributed according to the specified capacity in parallel.The number of modules in parallel system is increased to three to study the influence of total power variation and inverter removal on power distribution.In PLECS simulation module,a model is built to verify the validity of the control scheme.The results show that the circulation can be suppressed effectively,the active and reactive power can be shared accurately,and the terminal voltage is compensated.When the inverter has different capacity,it can be distributed according to the set.It is verified that the system stability can be maintained under the condition of three parallel inverters and working condition variation.