Research On PV Grid-connected Inverter Control Strategy With LCL Filter

The grid-connected generation with high capacity is the future of photovoltaic technology. For grid-connected inverter with higher power levels, the traditional inductor filter can not meet the standard requirements of the network’s harmonic current. It provides a new thinking for the grid-connected inverter output filter as the LCL filter structure appears. This paper researchs the grid-related inverter’s control technology, which is based on the LCL filter structure.This paper startes with the single-phase LCL filter’s transfer function of the input voltage to the output current, at the same time enhance the performance of the inverter output filter, it will inevitably leads to the resonance of the control system, and it affects the system’s stability and waveform quality of the grid current. In order to suppress the system’s resonance, the passive damping scheme of increasing the damping resistor in the filter circuit; for the passive damping program will brings additional power loss, the idea of using a control algorithm equivalent instead of the actual damping resistor, which is the active damping program; in order to obtain precise directional precision, it uses the virtual flux oriented instead of the traditional voltage oriented for the control of inverter grid, and it uses the direct power and closed-loop control in the inverter’s output, and it omits complicated coordinate transformation and decoupling in the control process, so it achieves the fast track response of the network.On the basis of theoretical analysis, it builds the simulation platform and makes the simulation research. According to the foregoings,it designs a5kW grid-connected inverter prototype based on the LCL filter, and the main circuit parameters, component selection, control system hardware circuits and the main program flow chart are given in details, further demonstrated the design’s rationality and progressiveness by experiments.