Control Strategies Of Power Quality Composite Conditioner And Studies Of The Technology Connected With Power System

Power quality problem pays more and more attention in recent years. Reactive power, harmonic and asymmetry are always the focus points which people concerns. This paper works to research the control strategies of power quality composite conditioner (PQCC) and the technology connected with power system, including following contents:This paper analyzes a power quality composite conditioner (PQCC) based on cascaded multilevel inverter and its control strategy. The cascaded multilevel inverter adopted with separated DC sources is constructed with a number of identical H-bridges inverters, not only simplifies hardware manufacturability, but also makes the whole device flexible in terms of power capability. The control method of the outer voltage loop and inner current loop is used by voltage quality conditioner (VQC) and current quality conditioner (CQC). In the VQC, the instantaneous value of load voltage acts as outer loop control to ensure load voltage fast tracking reference voltage. An inner filter capacitor current loop is used to improve the independence of the device and ensure the device running stably in various working condition. In the CQC, the outer voltage loop is controlled to steady the DC voltage and reach its given value, and the inner current loop is controlled by compensation current instruction in order to ensure compensation current quickly tracking command signal and a good compensation effect of the device. MATLAB simulation verifies the effectiveness of the structure and control strategy.This paper researches the technology for the PQCC connected with power system, including the device normal operation, power system faults and device self-faults. The response characteristics of the PQCC based on cascaded multilevel inverter is analyzed firstly with 10kV voltage grade in this paper. The simulation researches the VQC whether or not current-limited reactor and proves the fuction of limited fault currents when load side has faults. It is presented that the fuction of limited fault currents of VQC and its self-protection should match relay protection of relevant line, and the device operation dispatch should bring into distribution automation system. In addition, this paper analyzes response characteristics of VQC self-faults, and indicates that the device should have different response characteristics when it has different faults. The CQC ought have jugement fuction of load side faults, and communicate with relay protection of relevant line and distribution system. For the multilevel inverter faults occurring in the CQC, the device should exit operation immediately according to the program before enchtment and lock the trigger pulse of the inverter.