Research On A Dual Channel Interleaved Flyback-Type Micro Photovoltaic Grid-Connected Inverter

With the progress of the society, the rapid development of science and technology, the increased demand for energy and the increasing shortage of fossil energy, more and more attention has been paid on the use of renewable energy. The solar energy, with its unique advantages, plays an increasingly important role. And photovoltaic(PV) power generation, as a form of solar energy utilization, has become the focus of research and application. The core device of energy conversion in grid-connected photovoltaic power generation system is the inverter. With the rapid increase of home users and the fast development of building integrated photovoltaic (BIPV) technology, the development of grid-connected photovoltaic micro-inverter with low-cost and high-efficiency is the goal of researchers all over the world.In this paper, the operating principle and control method of the dual-channel grid-connected photovoltaic micro-inverter are studied. The system consists of a two-stage circuit like the traditional single-channel fly-back micro-inverter. Where, the first stage DC/DC circuit selects the interleaved fly-back converter and the second stage DC/AC circuit selects 2MOSFET+2SCR full-bridge inverter topology. This paper analyzes the operating principle and control method of the dual-channel grid-connected photovoltaicmicro-inverter system in detail.Compared with the traditional way of each PV array assembling a inverter, this paper proposes a scheme of two PV arrays sharing the same inverter, which makes a compromise between efficiency and cost, so that the cost performance can be improved. It also proposes a interleaved control strategy on the 4-way fly-back circuit in the dual-channel fly-back micro-inverter. The 4-way primary-side switches need 4-way driving pulse control signals.whose phase shift 90 degrees. Thus, it can not only inhibit the current ripple on the DC side, but also restrain the output current ripple.The equivalent circuit of grid-connected micro-inverter system is analyzed and the small signal modeling of micro-inverter is established in this paper, providing theoretical design basis for setting control parameters. The control strategy via communication technology is also analyzed and studied based on the MI200E chip. According to the requirement specification of the dual-channel micro-inverter, this paper gives the design of main hardware circuit and software flow chart. The hardware design includes the design of main circuit parameter, the selection of power device, the design of sampling and conditioning circuit and the design of driving circuit. Software design shows the flow chart of main program. The theoretical analysis is verified by PSIM software. On this basis, a experimental prototype of 490W dual-channel micro-inverter is developed. This paper selects TI company’s digital signal processor (DSP) TMS320F28035 as the main control chip, thus realizing full digital control of the micro-inverter system. Finally, this paper uses the 490W prototype for experiments and simulations. The tests on efficiency, power factor and harmonic are carried out, using the proposed control strategy in the four-way fly-back interleaved operation. The test data show that the experimental prototype has achieved the desired requirement specification.