Research On The Control Strategy Of Microgrid Based On Master-slave Structure

Microgrid combines micro source, energy storage, power load and control devices together toform a single controllable unit. It can run at both grid-connected mode and island mode. Microgridprovides a mechanism which makes full use of the distributed generation unit. It’s an important wayfor achieving high efficiency and high-quality power supply of the future grid. In microgrid, thecontrol strategy of the master inverter, as one of the key technologies of microgrid, provides thenecessary energy balance and voltage support for microgrid operation.This paper mainly studies the integrated control strategy based on the master-slave configurationof microgrid system. Firstly, it introduces the design method of the outer ring PQ controller, V/fcontroller and inner loop current controller of the master inverter. On the basis of analyzing thecontroller structure, it establishes a mathematical model of the master inverter. Then it introduces theprinciple and implementation steps of SVPWM. Second, the paper gives two software phase-lockedloops suitable for the microgrid system. Each phase-locked loop structure can track utility grid phasewhen operating at grid-connected mode, establish frequency support for microgrid system whenoperating at island mode, realize smooth transition of phase-locked angle when turning fromgrid-connected mode into island mode. So it can guarantee the smooth and seamless transition of themicrogrid system operation mode.This paper sets up a simulation model of microgrid and control system in MATLAB/Simulink.At the same time, it designed a microgrid master inverter experimental platform based onTMS320F28335, giving the hardware and software design. I did testing, evaluation and experimentalverification about previous theoretical studies based on this hardware platform. The simulation andexperimental results show that, the microgrid master inverter can operate stably at bothgrid-connected and island modes, which also realized a smooth and seamless switching between thetwo modes. Thus, it improves the reliability of power supply. As a result, the paper verifies thecorrectness and feasibility of the microgrid comprehensive control strategy which is based on themaster-slave structure.