افزایش microgrid پایداری ولتاژ پویا با استفاده از تثبیت کننده ولتاژ microgrid
Abstract: The ever increasing energy demands are stressing the generation and transmission capabilities of the power system. Distributed generation, mostly placed in distribution systems, has the ability to meet some of the growing energy demands. But, unplanned application of individual distributed generators, while solving some problems, can cause additional problems. This is because; the present distribution system cannot support bi-directional power flow. The microgrid concept has the potential to solve major problems arising from large penetration of distributed generation in distribution systems. A microgrid is not a robust system when compared to a power system. Therefore, proper control strategies should be implemented for a successful operation of a microgrid. Most of the DGs (such as fuel cells, PV arrays, microturbines, etc.) cannot produce reactive power. Thus, they cannot support voltage stability during dynamic state. Proper voltage controllers should be designed to maintain the voltage stability of the microgrid. This thesis proposes the use of a coordinated control of reactive sources for the improvement of the dynamic voltage stability in a microgrid in case of dynamic voltage deficiency. The associated controller is termed as a Micro Grid Voltage Stabilizer (MGVS). The MGVS is a secondary level voltage controller which takes the weighted average of the voltage deficiencies at the load buses and generates a control signal as its output. The control signal represents the incremental changes of the reactive power that need to be provided for the microgrid. This control signal is divided among the reactive power sources in the microgrid in proportion to their capacities; thus each source will be required to generate certain amount of reactive power. To show the effectiveness of the proposed MGVS, this controller is implemented in a micro grid test system in MATLAB environment. The test system has three DGs and six loads. A dynamic simulation of the test system is carried out for the cases of with and without the MGVS for various disturbances. Both grid-connected and islanded modes of operation are considered. Results show that, with the addition of MGVS, the dynamic voltage profile of the microgrid system especially at the load buses improve drastically.
Keywords: Applied sciences, Microgrids, Synchronous machines, Voltage stability