Research On The Control Strategy Of Single-phase Pv Grid-connected Inverter

As a kind of distributed generation systems, photovoltaic generation, owning the characteristics of none-contamination and enormous potential, has attracted widely attention in the world. The grid-connected inverter plays an important role in the PV system, which is used to realize the energy transmission from solar energy board to the grid and determines the quality of the output power and the efficiency of the system, so research on the control strategy to achieve high efficiency and high quality energy of the inverter system is of great practical significance.This paper firstly introduces the topology of different kinds of inverters, and mathematical model is built based on the single-phase H-bridge topology. Then the filter is analyzed and the parameters calculation method is provided. Afterwards the PWM modulation modes are described and unipolar-multiple-frequency SPWM is applied.This paper systematically researches on grid synchronization technology, of which single-phase PLL model is built. Among these methods, the SOGI based method is analyzed emphatically and its characteristics are studied in both time domain and frequency domain, according to which parameters design experiments are conducted. Afterwards, this paper focuses on research of control strategy and mitigation of lower harmonics of the inverter. The characteristics of feed-forward compensation are complained from the aspect of automatic control principle and the parameters of the PI controller are designed. Then, the lower harmonics caused by dead time of the inverter are analyzed mathematically, and the LMS adaptive filter is introduced to achieve the harmonics compensation. Also the dynamics of the system due to the introduction of the adaptive filter is analyzed.Afterwards, paper describes the design of the low-power experiment platform based on the DSP TMSF28335and the IPM, and the platform consists of the control system, the power system, the main circuit board and the HMI system. The software algorithm flow diagram is also provided. Finally, the theory and the overall design are validated with experimental results. And the THD of current injected to the grid from the PV inverter is less than5%.