Research On Control Technologies Of Photovoltaic Grid Micro-inverter

With the increasing scarcity of coal resources, natural gas and other primary energy,photovoltaic power generation technology has been widely studied and applied. In order to overcome the series and parallel connection solar panels making internal mismatch losses and hot spot phenomenon, achieving energy conversion system from a single piece of solar panels through a micro-power inverter(referred Micro-inverter), such power generation system will be the future development of photovoltaic power generation trends. It has many advantages, such as each solar panel can achieve maximum power point tracking(MPPT), to improve the photoelectric energy conversion rate and control is relatively simple.Firstly, in this paper, based on the studying existing topology of micro-inverter, high-frequency current-chain micro-inverter topology is applied, and its working principle is analyzed in detail. The mathematical model of the micro-inverter system is analyzed. Using small-signal linearization method for modeling, the transfer function of the system is obtained. By Bode diagram of the system, the dynamic characteristic of the system is analyzed. In order to make PV module operating at maximum output power point, the control method of a variable step disturbance observation is used to improve the energy conversion efficiency. In use of the Matlab SimElectronics component library, the device-level simulation model of the micro-inverter is established. On the basis of the simulation model, through researching the control strategies for the micro-inverter, the strategy of the introduction of the grid voltage as feedforward and the crossing zero point compensation of the current, and using fuzzy self-tuning Fuzzy-PI controller is proposed. The simulation results show that the control strategy is effective. Ensure the control precision of the net current and effectively reduce the harmonic content.Secondly, the current high frequency link micro-inverter of 155 W is designed. The design process of the circuit parameters and component selection are analyzed in detail. A soft-switching active clamp circuit is applied. The design of the active clamp circuit and the working principle are analyzed in detail. The control strategy of the simulation studying is applied in the micro-inverter system, in result of getting a good control effect.