Optimal Reactive Compensation With FACTS Devices

It's a basic need for modern society to insure safe and economical system operation and maintain good power quality. It's also the aim of the planning, operating and administrating people in power systems. As one of the important means for meeting this aim, Optimal Power Flow became the pop problem for many power science researchers since it came into being. It's a typical large-scale non-linear programming problem. With the gradual development of the electric market and the electric enterprise's commercialized operation, to control power flow, more and more flexible means for power control are required. FACTS (Flexible AC Transmission System) applies the electric electronic technique and modern control technique forms quick flexible control for AC transmission system, so as to improve the transmit capacity of transmission system, the controllability of power flow and voltage, as well as the system stability and security. Meanwhile, new demand and challenge come with the use of FACTS devices. In order to analyze probabilistic load flow with multi-operating conditions and FACTS devices, the following function works are carried out.Without FACTS devices, the probabilistic reactive optimization is carried out. The alternative calculation of expectations and covariance was used. The state variables in optimization problem are all of the expectations of bus voltages, covariances are varied with expectations. In the optimal aspect, the Newton's method was used which possesses a good convergency, fast solution speed and high precision. In the probabilistic aspect, the second order moment, i.e. covariance was used, which took the first order correlation between nodal powers into account. The objective function is the minimum power loss. The IEEE-14 buses system has been tested.In order to take FACTS devices in the probabilistic load flow, from the analysis of UPFC's structure, operation principle and action mode, the power flow calculation model including UPFC is determined. By means of the equivalent power flow injection approach, the function of UPFC is transferred to the two ending nodes of the branch that UPFC exists. In this thesis, the rectangular form is used. State variables are nodal voltages, control variables are nodal reactive power. The UPFC branch power constraint is considered. With elements related to UPFC are added into the Jacobianmatrix, Newton method is used to solve the problem.From above works, the optimal power flow problem including UPFC is carried out. The objective function is the minimum power loss. State variables are nodal voltages, control variables are nodal reactive power. The UPFC branch power constraint is considered. The calculation for Ward & Hale 6-bus system is carried out.