Stand-alone Photovoltaic Inverter And Technology Of Power Proportionally Distributed For Paralleled Inverters

Because most of the distributed generation are interfaced to the microgrid through inverters, so stable running of the parallel inverters will greatly improve the overall capacity and reliability of the microgrid system[1].Inverters with different capacity should achieve proportional power sharing according to their capacity.But current research mainly aims at inverters with same capacity instead of different capacity. So this article designs two stand-alone photovoltaic(PV) inverters with different capacity in parallel, and has achieved proportional load power sharing according to their capacity.This paper focuses on algorithm and software design. The main content is as follows:The first is the overall design of the stand-alone PV inverter system,the overview of topology of the system.The second is the design of the main circuit topology and parameters of component in the system.Boost converter is used for the solar battery booster circuit, and corresponding design of the inductance and capacitance and model selection of the switch tube is introduced.Single phase full bridge topology and the single polarity modulation is chosen for inverter circuit, and the design of LC filter is introduced.The energy storage unit design mainly includes the calculation of battery capacity, the selection of topology for battery charging and discharging, the deign of the inductance and capacitance and model selection of the switch tube.Next part is the design of control strategy.Inverter voltage controller adopts a double loop with voltage and current.Based on the combination of root locus method and time-domain analysis,the influence of control delay is considered. Energy management strategy mainly introduces design of various working mode of the system.At last simulation and experiment have been carried out.The last is the parallel control strategy,where the main innovation of this article is concentrated.The condition of proportional power sharing is fully deduced with a novel way, the adaptive band-pass filter is used to reduce the virtual impedance in the harmonic frequency so as to reduce the distortion of the output voltage.At last corresponding simulation and experiment have been carried out.