Harmonic Suppression And Reactive Power Compensation Theory And Application Research In High Voltage Distribution Networks

It is low cost and convenient to eliminate harmonic currents and compensate reactive power in high voltage distribution networks. However, due to the voltage and capacity limit of power electronic switching device, it is difficult to realize harmonic currents dynamical suppression and reactive power dynamical compensation at same time. Based on the financial support of The National Natural Science Foundation of China (Project No.60774043) and The National High Technology Research and Development of China (863 Program) (Project No.2008AA05Z211), this paper proposes three types injection type hybrid active power filter(IHAPF) to realize harmonic currents dynamical suppression in high voltage distribution networks. High voltage hybrid compensator (HVHC), consists of static var compensator (SVC) and IHAPF, is proposed to realize harmonic currents dynamical suppression and reactive power dynamical compensation at the same time in high voltage distribution networks. This dissertation expands the structure, principle, detection and control method, as well as the optimum design means of main parameters and some important realizing technologies. The emphasis and achievement of the paper mainly manifests in the following aspects:1. Three novel topologies of IHAPF are proposed and their universal electric model is established. Based on the establishment of the electric model, the thesis analyzes the effect of IHAPF to avoid the harmonic amplification, and resonance between passive devices and the grid. Finally, improved genetic algorithm is proposed to design the parameters of injection branches of IHAPF.Based on the topology of single-resonance IHAPF(S-IHAPF), this paper proposes three improved topology of IHAPF such as Double-resonance IHAPF (D-IHAPF), Multi-branches IHAPF (M-IHAPF) and Improved IHAPF (I-IHAPF). Their respective strong points are analyzed. The universal electric model is established in succession, it helps to the uniform research of different sort IHAPF. And then, the effect of IHAPF to avoid the harmonic amplification and the resonance between passive devices and the grid is analyzed compared with capacitor. Finally, take S-IHAPF as an example, improved genetic algorithm is proposed to design the parameters of injection branches considering three aspects such as filtering performance, cost, security and stability.2. Two key algorithms such as harmonic currents detection algorithm and tracking control algorithm are researched. Furthermore, three methods were proposed to solve the problem based on the steady and dynamic analyze on the sharp rise of DC-side voltage.Harmonic predicted detection method based on self-adaptive noise countervailing principle was proposed in this paper. The method reduced the delay and improved the filtering performance. Harmonic current tracking control method based on recursive integral and fuzzy-PI control is proposed to improve the control precision when the controlled variable is periodic. Furthermore, based on the steady and dynamic analyze on the sharp rise of DC-side voltage, three methods were proposed to solve the problem such as hysteresis control energy release method, DC-side voltage control based on energy balance, and DC-side voltage PI control based on the fundamental energy exchange. Their respective strong points are analyzed.3. High voltage hybrid compensator (HVHC) is proposed to realize harmonic currents dynamical suppression and reactive power dynamical compensation at the same time in high voltage distribution networks. Furthermore, suppressing coupling crosstalk hybrid control strategy is proposed to eliminate the infection between SVC and IHAPF consists of compensator susceptance calculation method base on synchronous reference frame and harmonic currents dividing frequency control.In allusion to the status that IHAPF can not compensate reactive power dynamically, this paper proposed HVHC consists of SVC and IHAPF. In the proposed system, harmonic currents generated by SVC can also be eliminated by IHAPF. HVHC realize high quality energy saving in high voltage distribution networks. Based on the analysis of its topology, model inference has been done in fundamental frequency and harmonic frequencies, the inference results show the validity of HVHC. Furthermore, control method suitable to HVHC is researched to prove that HVHC can compensate reactive power, eliminate harmonic currents and three-phase unbalance. Suppressing coupling crosstalk hybrid control strategy is proposed to eliminate the infection between SVC and IHAPF consists of compensator susceptance calculation method base on synchronous reference frame and harmonic currents dividing frequency control. Simulation and experiment results show that, after the proposed control method has been adapted, HVHC can compensate reactive power and stabilize the grid voltage, suppress harmonic currents steadily, speedily and exactly.4. Based on the industrial need on harmonic suppression and var compensation, application scheme when HVHC applied in 35kV grid is researched.Based on the project of harmonic suppression and var compensation in an 110kV substation in Guangxi province, this paper analyzes the reason why harmonic parameters exceed the limit, and then system equivalent model of the substation is founded according to the data measured in the substation. Simulation results in three different conditions show the rationality and veracity of the model. Based on the above-mentioned theory and design method, HVHC which is suitable to 35kV grid is designed. Parameters design method of SVC is given. Simulation results show that HVHC can satisfy the industrial need, the harmonic current injection ability can be guaranteed even in 35kV grid, and it is low cost to eliminate harmonic currents and compensate reactive power in each conditions.Under guidance of theory and technique in eliminating harmonic currents and compensating reactive power in high voltage distribution networks, HVHC consists of SVC and S-IHAPF has been developed. The design process of hardware and software has been given in detail. Experiment results show the validity of the principle, signal detection, control method and parameter designing means in eliminating harmonic currents and compensating reactive power in high voltage distribution networks.