Control strategies of gridconnected inverter in 

seriesconnected optimizer solar system

 

 

 

CHEN Wang, CHEN Min, ZHANG Zhe

 

(College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)

 

 

Abstract: Solar system based on seriesconnected optimizer structure is effective to solve the hot spot effect and increase output power when partial shading or mismatch between photovoltaic panels. Aiming at the influence on the output current that is exerted by 100Hz voltage ripple on the DC bus, the topologies, control strategy and loop design of the central inverter were investigated. A double loop control strategy was designed for the central inverter which includes an outer voltage loop to maintain the DC bus voltage and an inner current loop to regulate the grid current. The relation of 100Hz voltage ripple to control loop was analyzed, in addition a novel control method of compensating the voltage ripple in the voltage loop was proposed, that was to calculate the ripple value and phase by the grid phase, bus capacitance, output and input power, thereby compensating the ripple interference in the voltage loop. The results indicate that the method can decrease DC bus capacitance effectively, meanwhile depress the output current THD.

 

Key words: solar system; gridconnected inverter; control strategy