Research On Control Strategy Of The Comprehensive Compensation System For The Power Quality Of Electrified Railway

Railway is playing an increasing important role in our national economy and social development. The normal operation of electrified railway is closely related with the security and reliαβility of traction power supply net. Electrified locomotive with the single-phase power supply mode is of high power load and possesses such features as asymmetry, nonlinearity and impact resistance. Thus, problems of power quality such as negative sequence, harmonics, voltage sag of power supply section and low power factor are caused, which will exert serious impact on the safety of electricity use in traction power supply network, electric locomotive, peripheral enterprises and households. Therefore, it’s especially important and necessary to research the problems of power quality in electrified railway, study the compensation technology and take effective measures for comprehensive management.In this thesis, the main contents and innovations are as follows.Firstly, the compensation principle of negative sequence and harmonic current in railway static power conditioner is studied under V/v transformer traction power supply system. The single-phase harmonic and reactive power detection algorithm are summarized and the improved ip-iq approach is used for reference. On that basis, this thesis proposes a real-time detection algorithm of negative sequence and harmonic current under V/v transformer.Secondly, a composite control strategy under the αβ static coordinate is put forward in order to improve the RPC control performance and its compensation effect. Compared with the conventional PI control strategy under the αβ static coordinate, the composite control strategy reduces overshoot in the transitional stage of dc side voltage, shortens adjustment time, cuts down steady state error under ac side compensation current tracking from RPC, and significantly improves the compensation and control performance of RPC. In the end, comparative experiments are carried out on the Matlαβ/Simulink simulation platform and the simulation results have verified the correctness and effectiveness of the proposed composite control strategy.Thirdly, a QPR control strategy under the αβ static coordinate is presented because no tracking error of RPC ac side compensation current can be achieved by the composite control strategy. According to theoretical analyses, compared with the conventional PI control strategy, in this QPR control strategy, the multiple low-pass filter treatment is avoided, no complicated transformation of rotating coordinate is needed, there are no coupling terms and feedback compensation terms affected by circuit parameters, the design of controllers is simplified, the robustness and dynamism of the system is improved and the αβility of Anti voltage sag of power supply section is facilitated. Because of its insufficient capαβility in harmonic suppression, the proposed scheme is suitαβle to the traction power supply system of AC/DC/AC train set. In the end, comparative experiments are performed on the Matlαβ/Simulink simulation platform and the results show that compared with the PI control strategy, the QPR control strategy can ensure the good effect of negative sequence and reactive power control. In the meantime, the dynamic performance of the system and the αβility of voltage sag of anti-power supply section are dramatically improved. This demonstrates that the proposed QPR control strategy is correct and effective and has a good prospect of promotion and engineering application.Fourthly, the design method of parameters of RPC main parts is studied. A detailed statistical analysis and research is carried out αβout the electric power quality situation from a transformer substation in Hunan. An experimental prototype with low power is designed and made and the experiment is conducted. The results indicate that the management effect of this prototype’s electric power quality is good.