Power Distribution Method Of Inverter Parallel System Based On Generalized Droop Control

With energy and environmental problems becoming more and more serious,the development of new energy and clean energy has become the general trend of future energy development.Because the solar energy is clean and plentiful,photovoltaic power generation is a better choice for power generation systems.Inverter is a key link in the process of power generation,and its control strategy determines the quality of power supply.The output power of distributed power is low,and multiple parallel units are needed to effectively improve the system capacity.The generalized droop control is improved on the traditional droop control to adapt to the power and frequency disturbance of the inverter system.Therefore,this paper studies the circulation suppression and power allocation of the parallel three-phase inverter system based on the generalized droop control.In order to solve the problem of stable operation of parallel system,this paper adopts the generalized droop control method to build the model structure of two three-phase inverters in parallel.The basic principles of traditional droop control and generalized droop control are described.Based on the control principle and model structure of the generalized droop control,the mathematical model of the inner loop controller based on the two-phase static coordinate system is established.The influence of different controllers on the system performance is analyzed,and the control strategy for the stable operation of the parallel inverter system is given.The influence of inverter transmission impedance,i.e.external characteristics,on the system power and circulation is analyzed.The output impedance of inverter is modeled and its influence on power coupling is analyzed.Analyze the cause of circulation and derive the definition of power characteristic and current circulation.The influence of line impedance on power and circulation in low-voltage resistive circuits is studied.The bus voltage compensation method is used to eliminate the circulation and restore the power distribution accuracy.In order to ensure the power transmission performance and power decoupling performance of the system,the strategy of measuring line impedance based on pulse perturbation method is studied,and the virtual negative impedance is used to adjust the transmission impedance of the inverter to the expected value.The generalized droop control small signal model was established,the system power distribution scheme was deduced,and the parameter Settings of each inverter under different capacity were given.A simulation model is built in PLECS to verify the correctness of the above theory.On the basis of the above research,a parallel experimental system based on three-phase inverter is established,and the control principle proposed in this paper is verified experimentally.The experimental results show that the improved generalized droop control can eliminate the influence of different line impedance on the power distribution of the system,and can compensate for the problem of voltage amplitude drop of common connection line caused by transmission impedance.