Power Conversion System And Its Engineering Application In Microgrid

As traditional energy reserves becoming less and less, along with expending need for energy and serious environment pollution issue, countries are now engaging in developing and utilizing new clean energy and focus on renewable energy source such as Photovoltaic and Wind energy. Microgrid system which bases on intermittent energy is developing. This system can fully meet the need of power load nearby and the supplement the large power grid. It reduces the power load dependence and line losses of the large power grid, and improves power quality, and enhances the stability, reliability and safety of the system as well. Converter as the key element of the energy storage system bears the responsibility of the energy conversion between AC from the grid and DC from the energy storage battery. It reduces the shock between the grid and the microgrid by controlling the power of PCC in grid-connected operation, and supplies the power for the loads in microgrid system reliably on coordinating the modes of the parts of the microgrid in island operation. Therefore, the development and utilization of energy storage converter has great theoretical and practical significance.The converter discussed in this paper is used for lead-acid batteries. The design and implementation of this converter are introduced by hardware and software. The converter is based on the principle of the three-phase voltage PWM rectifier circuit and control mode of the double closed loop. DSP, which is chosen to drive the IGBT, can control the Charge and discharge mode of the batteries by changing the output DC of the converter. CPLD is used to perform the additional functions such as protection and signal amplification. The converter shares information, such as the control command and actual value, with host computer in real time by RS 232 interface. The microgrid experiment platform contains PV system, energy storage system, Power Conversion System (PCS), monitoring system and the related load. The converter shows the great performance by analyzing the date collected from different running statuses.The experiment shows that this 100kW bi-directional energy storage converter is stable and reliable. And the large power factor, high conversion efficiency, low electromagnetic interference and quick response of this converter is also proved by experiment data.