Research Of Single-phase Grid-connected Photovoltaic Inverter Based On Digital Current Error Control Technology

In recent years, with the increasingly serious energy crisis and environmental pollution, photovoltaic power generation, as a representative of new energy technologies, has been widely attention. Photovoltaic inverter is an important part of the photovoltaic power generation system. Developing low-cost, highly efficient and stable PV inverters, is a hot spot of photovoltaic technology. For the above background, This paper focuses on the research of the single-phase photovoltaic grid-connected system and current control strategy for grid-connected inverter.Firstly, the paper builds a Matlab simulation model of solar cell and analyzes solar cells output characteristic curve in different temperature and light intensity. And a MPPT algorithm, the perturbation and observation method combined with constant voltage tracing method, is used in Boost circuit to achieve maximum power point tracking control of solar cell. And the simulation results demonstrate its effectiveness.Then, Based on two non-isolated inverter topology, the paper focuses on the control strategy of grid current. A simple new current control algorithm called digital current error control(DCEC) is proposed with detailed theoretical analysis and stability analysis. The algorithm is simple and effective and the simulation results demonstrate the excellent properties of the control strategy.Furthermore, by comparing conventional single-phase phase-locked loop methods, the delay method generating a virtual two-phase is determined as the PLL scheme in this paper. As an essential function of distributed grid-connected power generation systems, islanding detection scheme is introduced.Finally, according to the hardware structure and control strategy of PV system, the hardware platform and software flow of the inverter are designed, and the prototype experiment is carried out. The experimental results show that the output current of single-phase grid-connected photovoltaic inverter meets the grid-connected requirements, the inverter can achieve unity power factor and low current distortion.