Research On Detection Technology Of Voltage Phase And Reactive Current In STATCOM Reactive Power Compensation

Reactive power compensation of the power supply system can reduce the active power loss of transmission and distribution lines, and stable the voltage level. Reasonable selection of reactive power compensation device, can effectively compensate reactive power of the system, improve power transmission environment. The static synchronous compensator(STATCOM)with many advantages is the main direction of the research and development of reactive power compensation devices, and Its key technologies include synchronization technology, modulation strategy, dynamic reactive power control, control and protection under unbalanced conditions.This paper mainly focuses on the research of voltage phase detection and reactive current detection in three-phase balance system and unbalanced system,including the following aspects:(1) Discussed and analyzed the voltage phase detection with phase locked loop and direct phase calculation method in three phase equilibrium system. In this paper, a new phase calculation method is presented, which is based on the orthogonal relations of phase voltage and line voltage. The simulation is carried out by using MATLAB software, and the accuracy and dynamic response capability of the method are verified by comparing with the phase locked loop method.(2) The reactive current detection method based on instantaneous reactive power theory is analyzed in detail. Aiming at the problem that the DQ method with phase locked loop is not accurate when the voltage is harmonic distortion,an improved method for constructing the transformation matrix by using the phase voltage line voltage is presented. The correctness and practicability of the method are verified by simulation.(3) The effect of the negative voltage sequence component on the STATCOM operation is analyzed. The theoretical method for extracting positive and negative components based on the decoupling of the double synchronous rotating coordinate system and instantaneous symmetrical component methodare analyzed in detail. The simulations model are established, and the positive and negative sequence component extraction performance and response characteristics of the two methods were compared and analyzed.(4) The effect of negative sequence component on voltage phase detection and reactive current detection are analyzed. The dual synchronous coordinate decoupling method of voltage phase and non reactive current detection method has carried on the structure analysis. According to the advantages and disadvantages of instantaneous symmetrical component method, use which extract the positive sequence componen, combine with the phase voltage, line voltage orthogonal relationship method to calculate the voltage phase, and then combine with the DQ method was used to detect the reactive current.