Research On Power Quality Integrated Control In Distribution Network With Distributed Generation

New emerging composite system of large grid and distributed generation is considered as an effective mode of saving investment, reducing energy consumption and increasing the reliability. For the distribution network, the distributed generation could utilize the local superior resource, providing clean and reliable energy to users, but also brought many negative effects. Distribution network is mainly connected near the user at the terminal of the power system and the power quality is not good. Various kinds of power quality problems, such as voltage sag, voltage flicker, supply disruptions, short term three phase unbalanced and harmonics etc, in some degree make the occurrence of the power supply blocking and secondary fault more easier happen. In the distribution network with high penetration of DGs and micro-grids, the problem of how to take advantage of the strongpoint of DGs, to avoid its shortcoming and to construct effective, energy-saving as well as high level power energy distribution network, on the premise of not increasing hardware cost of the power quality correction devices in distribution network, is worthwhile to research.Due to the same circuit configuration of gird-connected inverter of PV and active power filter, the micro-grid PV power system with filtering function which can work as the grid-connected inverter and active power filter simultaneously and its corresponding unified control method are presented. A feasibility study for unified control and the system design parameters are put forward. Theoretic analysis and experiments proved the feasibility of this scheme which increases the advantage of distributed generation by supplying enough active power to the load and improves the power quality by suppressing the harmonics caused by the nonlinear load. In order to let micro-grid be more easily accepted by distribution network and undertook much responsibility, in this paper, reactive voltage collaborative control system consisted of DSTATCOM and micro-grid is proposed. It use small-capacity DSTATCOM as continuous subsystem for rapid continuous reactive power regulation and micro-grid as discrete subsystem to provide large-capacity graded reactive power. Their collaborative working could realize rapid adjustment of reactive power.Configuration of static var compensator (SVC)in the distributed power supply system is a widely adopted and effective measure to improve the quality of power supply. As SVC itself is harmonic source, the paper proposed to add harmonic compensation order in the current regulation loop of grid-connected inverter on the premise of not increasing hardware cost, in order to suppress the harmonic generated by local load and SVC. For the existing SVC control method is difficult to adapt the distributed generation's characteristics of intermittent and fluctuation, the SVC voltage control strategy based on optimal recursive integral PI is put forward in the paper. The paper analyses the control stability of the adding filtering system and proposes improved measurement. The intelligent and high quality power supply system of inverter-based distributed generation with SVC could not only provide power, but also compensate for voltage fluctuation quickly along with eliminating harmonic produced by local load and SVC.Aiming at the negative impact and the advantage of improving the power quality brought by DGs, the paper puts forward a kind of power quality multi-agent control system. According to the united analysis of example under various kind of conditions, the correction and effectiveness of power quality multi-agent control method in distribution system which contains distributed power supply is verified in the paper.