Power Hardware In The Loop Simulation Technology Of Microgrid

This dissertation focuses on microgrid with only renewable resources and battery inverters, points out mentality of designing and implementation method of the microgrid power hardware-in-the-loop simulation (PHILS) platform, and researches on microsources control strategies and microgrid grid-connected and islanding switching method. The dissertation mainly researches the following three aspects.Firstly, to build the PHILS platform of microgrid, and understand working principles of the platform elements, for examples the modeling method of RTDS and dSPACE, working principle of digital power amplifier, the designing mentality of distributed generation equipment. The working principle of the platform is like this:the RTDS builds the power system model, the signals from RTDS are amplified by the power amplifier without distortion; the RTDS and power amplifier compose the grid simulator that can connect with the converters, the RTDS collects current of converters; for the power model in RTDS, the current source instead of distributed generation equipment pours the power into grid.Secondly, principles and control methods of microsource inverter are investigated. Because many kinds of microsources are in the microgrid, their control methods are varied, as photovoltaic and wind power generation this kind of intermittent microsource should adopt constant DC voltage control; as gas turbines etc. distributed power supply and battery etc. energy storage equipment that adjust generating capacity should adopt constant PQ control or droop control, so need to search control strategy of two kinds of microsources. i) Study on control strategy for intermittent microsources. Firstly, analysis I-V and P-V characteristics of100YGE245P type photovoltaic cells. Secondly, design two-level PV grid-connected generation system. Finally, simulate and prove the double close loop control strategy of Boost circuit, MPPT strategy and constant DC voltage control. ii) Study on droop control strategy of wireless-paralleled distributed storage converter. Firstly, from the power P and Q relationship with voltage V and angle δ of view, the dissertation discuses R/X influence on the converters and points out designing method of P-f and Q-V single-loop droop controller with considering R/X influence. Secondly, the dissertation designs "power-voltage-current" three-loop droop controller based on single-loop droop controller. Finally, the dissertation points out when the converters connect with grid, they can adjust output power through changing droop slope; when the converters disconnect with grid, they can share load power based on their droop characteristics.Finally, grid-connected and islanding switching method of microgrid is investigated. Microgrid has grid-on and grid-off two operation modes, and seamless switching function between two operation modes. After microgrid from grid-on turns into grid-off, the microgrid needs to adjust secondly to reach reasonable power quality; before microgrid from grid-off turn into grid-on, it finishes synchronization of microgrid and main grid through main adjusting converter moves droop curve. By analyzing dynamic switching process of microgrid, the dissertation presents a pre-synchronous control strategy. The difference between other control methods is that using phase angle difference of microgrid and main gird completes synchronous adjustment of microgrid frequency and phase angle. When microgrid is working at different modes, control strategies of microgrid converters are different, so the dissertation points out a control strategy switching method of converters.