The Research On Load Shedding System Based On Power Balance

According to the expending scale of the power system, with the obvious raise of the economical efficiency, results in slacking down the capability of resisting perturbation. First, this dissertation discourse on the development of power system and it's characteristic, elaborate the concept of the frequency and voltage in the power system, with the important of controlling frequency and controlling voltage. Then, analysis power balance factor with the load characteristic, The important relation between frequency, voltage and active power, reactive power in power systems was analyzed in this dissertation. We also research on the module of the Micro-grid system and it's power balance control, then establish the Micro-grid system module. And research on the simulation of the system by the software EMTDC/PSCAD. This dissertation mainly research on the Micro-grid system run in the network and independent situation with power balance control. Especially, analysis the system from power control, frequency control, voltage control respects when in the island mode. Firstly, we simulate in the network, the wind power start to join in the Micro-grid result in the power flow change and real-power, reactive-power variation in the power unit. Then we simulate the pre-planned islanding to investigate transient behavior of the multiple DG micro-grid as the basis for the fault-solve. The more, we simulate the main power during the three-phase line-to-ground fault, the micro-grid by tripping operation isolate in the islanding transient with power variation in each power unit. Through the simulation results, the important of the power balance control in micro-grid is obvious. Due to the incompletion decoupling relation and the mutual influence, so in the precise and perfect system design, especially to raise the optimize controlling system performance, must well considering the change of the voltage influence to the system load, frequency and controlling performance. So we propose the under-voltage load shedding control arithmetic and frequency predict arithmetic in the Micro-grid system. Then propose a PID control arithmetic to confirm time constant in low-frequency load shedding. The new proposal suits to the worst power deficiency situation, also is useful to the local power lacking. Through the simulation research, compare to the traditional load shedding plan, we can see that the more fast the new load shedding proposal work and quickly shedding the load in the large perturbation, release the burden of the interconnection line, the short time to recover.In the end, the paper summarizes the research content pointing out the research deficiency, And the Problems that need to be further researched and resolved are proposed.