Research On Parallel Coordination Control Of Energy Storage System

For remote mountain areas and islands,power supply is often used for island power supply.As the system power supply,the output power of renewable energy is intermittent and fluctuation,which seriously affects the quality of island power supply,seriously affect the quality of island power supply,and the access of the energy storage system can improve the reliability of power supply and the power quality of the system.At present,there is little research on AC grid composite energy storage system,so this thesis focuses on the parallel coherence of energy storage system.The main contents include:(1)Based on the mathematical model of three-phase full converter,the traditional droop control principle,the output power distribution of parallel system converter and the analysis of circulation,In order to solve the problem of the traditional droop control,such as the serious output voltage,the serious frequency drop and the slow dynamic response,an improved droop control strategy is adopted,by changing the fixed droop coefficient into an adaptive droop coefficient and adding a differential term,the output voltage,frequency deviation and dynamic performance of the converter are effectively improved.The stability and dynamic performance of the improved droop control are theoretically analyzed by using small signal modeling,and the improved droop control strategy is simulated and verified experimentally.(2)In view of the characteristics of energy storage devices and power type energy storage devices in the energy storage devices,for the composite energy storage system,the two devices are distinguished by employing a low-pass filter in the droop control P-f link,in order to realize the equipartition of the output active power of the same type of energy storage converter in the same type of energy storage system,the power storage converter in the composite energy storage system responds to the high frequency power,and the energy storage converter in the composite energy storage system responds to the low-frequency power.Simulation and experimental verification is also given.(3)In the middle and low voltage distribution network,the impedance of the line is resistive,and the circulation in the parallel system is caused by the different impedance of the line,a virtual impedance is added to the control loop to compensate the line impedance difference by this two adjustment mode to suppress the circulation.The principle of the system is analyzed,and the stability of the system is analyzed by the zero pole diagram,and the simulation and experimental verification are carried out.(4)For multiple energy storage devices,such as batteries in parallel and multiple power storage devices,such as ultracapacitor in parallel,considering SOC(State,of,Charge)of the different battery and the DC side voltage of the different ultracapacitor is different,SOC equalization control strategy in the two regulation mode is adopted to realize the consistency of SOC,output active power and instruction frequency of different batteries and the DC side voltage,SOC,output active power and instruction frequency of different super capacitors.The simulation and experimental verification are carried out respectively.(5)An experimental platform is built,and the proposed control strategies are verified by experiments.