Control Strategy And Electromagnetic Analysis Of STATCOM Based On 3-Ph Unbalanced Load

In the modern power system, the widely use of inductive load like motors or transformers causes much of reactive power. It increases apparent power and the losses of the power system, reduces equipment capacity utilization. And the 3-Ph unbalanced load will not only increases the reactive power, but also generates negative-sequence current which will seriously affect grid power quality and disupt the operation of motors and transformers. The research of STATCOM is very significant because of its fast compensation abilities on reactive power and imbalance.The article analyzes the control strategy and electromagnetic properties of STATCOM in the condition of 3-Ph unbalanced inductive load. This paper studies STATCOM in several aspects as follows.The article first analyzes the working of STATCOM and the detection of reactive power. The detection algorithm and control strategy in 2 different load conditions are studied by theoretical analysis and formula deduction. Characteristic of different control strategy are compared, mathematical model is built, and according to the limitation of the parameter coL in feed-forward decoupling control method when the inductor is nonlinear, the optimization measure is provided. In software Psim 9.0, the model of STATCOM circuit, detection algorithm and control strategy are established. For different load condition, the simulation analysis presents the STATCOM’s compensation effectiveness on inductive load and unbalanced load, which verifies the feasibility of theoretical deduction.In order to validate the correctness of the design of the control strategy and hardware’s parameters, the hardware of STATCOM is established and experimented, the result shows that the STATCOM hardware can compensate not only reactive current but also negative-sequence current, which coincides with the simulation and verifies the correctness and feasibility of the theory.The frequency-domain model of reactor in STATCOM is established. It is used to analyze the influence of reactor’s stray capacitance on filter performance of reactor. The finite element analysis software Ansoft is used to establish and compute the model of 4 kinds of reactors, acquiring the characteristic curve of reactor with different cores and the magnetic fields in the core, which can be used to assess the saturation character of different reactor.At the end of the paper, the summary and analysis of the whole work has been made, and the futher investigations about the STATCOM are pointed out.