Research On Active Voltage Arc-Suppression Control Method For Asymmetrical Distribution Network

With the continuous expansion of distribution network,the capacitive current of the system continues to increase,resulting in the fault arc in single-line-to-ground(SLG)fault difficult to extinguish,threatening the security of the distribution network.Active voltage arc suppression method has the advantage of high reliability without measuring line-to-ground parameters.Accurate identification of faulty phase and precise control of neutral voltage are the keys to realize effective arc suppression by active voltage arc suppression method.The traditional method does not consider the influence of asymmetrical line impedance and leakage inductance of injection transformer,which easily leads to the faulty phase identification error and the control system instability,and the arc suppression effect cannot meet the requirements.In order to solve the problem of reliable arc suppression of the SLG fault in asymmetrical distribution network,the paper proposes a faulty phase identification method of the SLG fault based on the magnitude and phase variations of the phase-to-ground voltage,and studies an active voltage arc suppression control method considering the leakage inductance of the injected transformer.Firstly,the paper analyzes the magnitude and phase variation models of the three phase-to-ground voltages before and after the occurrence of the SLG fault,and discusses magnitude and phase variation rules of each phase-to-ground voltage.According to the variation rules,a reliable and practical faulty phase identification method is proposed,and the implementation flowchart of this method in different neutral grounding methods is also given.Then,considering the leakage reactance of the isolated transformer,the paper establishes the active voltage arc suppression control system model.Aiming at the problem that the resonant peak of open-loop transfer function introduced by leakage reactance can easily lead to the instability of the system,an active voltage arc suppression control method with voltage and current double closed-loop control is proposed.The current inner loop adopts the injection current and the filtered capacitive current feedback structure to effectively suppress the resonant peak of the output filter.The voltage outer loop adopts neutral voltage feedback to realize accurate tracking of arc suppression control target.The core control parameters of the proposed method are designed in detail,and the superiority of the proposed method in control performance is analyzed.Finally,the simulation model of 10 kV distribution network is built in simulation software,and the faulty phase identification method and the active arc suppression control method proposed in the paper are simulated and analyzed in detail.An experimental platform of active voltage arc suppression control system is built in the laboratory,and the principle of the active voltage arc suppression control method proposed in the paper is verified.The simulation results show that the SLG faulty phase identification method proposed in the paper can precisely recognize the faulty phase,which is suitable for distribution networks with various neutral grounding methods and does not need to measure the complex system parameters of distribution network.So,the proposed faulty phase identification method solves the problem that the traditional method cannot accurately identify the ground faulty phase,and is simple and credible.The simulation and experimental results show that the active voltage arc suppression control method proposed in the paper has good suppression effect of fault current and excellent dynamic performance,which does not need to measure the distribution network system parameters such as capacitive current,and can achieve fast and high-precision suppression of fault current.