Micro-grid Grid Inverter Design And Control Strategy Research

In order to take advantage of the distributed new energy, the development of distributed new energy, energy storage system and micro-grid structure composed by local load energy is becoming increasingly mature. As an interface of micro grid ac and dc sides, the inverter determines whether the distributed energy can friendly grid. In the micro-grid, the inverter plays an important role, and the grid inverter control is the key of this study.Starting from the grid inverter current control, this article establishes a mathematical model of the three-phase grid inverter. The first detailed describes the PI vector control, hysteresis control and quasi-PR control of the current monocyclic control principle, analyzes the relationship between PI vector control and quasi-PR control, and compares the characteristics of different control strategies.Then, starting from the characteristics of the inverter output filter, analyzes the stability of the system. LCL filter has a good ability to restrain high harmonic, but exists resonance problems. Based on the principle of the filter capacitor branch series damping resistors absorb harmonics, on the basis of current control, this paper introduces the double loop control structure based on capacitive current inertia compensation to suppress resonance and improves performance of the grid inverter output current.Again, this paper describes the main hardware design method of three-phase grid inverter device. Using high-performance microcontroller and CPLD as control core, designs the good linearity voltage and current signal conditioning circuit. And through IPM module builds grid inverter main circuit, designs the fly-back power inverter to meet the needs of each control unit. Finally, independently develops grid inverter experimental prototype.By building micro-grid and grid inverter model in MATLAB/Simulink, this paper simulates the control strategy of grid inverters and islanding mode, verify and improves the validity of double loop control structure. At the same time, through self-designed grid inverter device to verify the part of the control strategy.