Static Synchronous Compensator Reactive Current Detection And Control Strategies

With the development of industrial automation, the much higher quality of the power is required by customers. The power quality is seriously influenced by the capacity of reactive compensation. Therefore the reactive compensation is payed more and more attention in the field of power electronic.The static synchronous compensator (STATCOM), because of its faster response, wider adjustable range and better wave quality of compensator current, has become the development trends. The structure of STATCOM, detecting algorithm of reactive current and control strategy is studied in this thesis.At first, the development, researching trends and working principle is introduced. The different structures of the STATCOM are compared in this thesis. In order to overcome the disadvantage that large numbers of independent power supplies are needed in cascade multi-level main circuit. The hybrid cascade inverter is adopted in this thesis. The triangle carrier phase-shifted-switch frequency optimal PWM (PS-SFO-PWM) modulation strategy is adopted to simulate the main circuit for verifying its feasibility.Secondly, the detection algorithm based on the instantaneous reactive power theory is introduced. The three-phase reactive current detection algorithm without PLL (phase locked loop) is adopted to make the dq detection algorithm better. It is verified by the simulation results, that the active current and reactive current of three-phase fundamental wave can be accurately detected by using the improved dq detection algorithm, when the voltage of power grid is distorted.Considering the noise and parameter variety of STATCOM, the Fuzzy-PI control strategy is designed. Good dynamic performance of Fuzzy control and fast response speed of PI control is combined in the strategy, which makes control system have fast response speed and high control precision.These advantages are verified by the simulation result.In addition, the simulation model of STATCOM is build. The results are compaired by using the PI model and Fuzzy-PI model. A conclusion is obetained that the reactive current can be fast detected and precisily traced by using the Fuzzy-PI control strategy when the power grid current is distorted.Finally, the improved dq detection algorithm is examined by using the TMS320F2407 experimental platform, and a good result is obtained. The correctness of the analysis and the feasibility of the control algorithm are validated by the result.