Research Of Mine Transformerless Shunt Hybrid Active Power Filter

With the more and more extensive application of non-linear equipment such as frequency converter and soft starter in the mine power grid,a large number of harmonic and reactive currents are introduced into the mine power grid,resulting in the current waveform distortion of the power supply grid and seriously threatening the safe and stable operation of underground devices.Therefore,it is very important to improve the power supply quality of coal mine power system.Hybrid active power filter(HAPF)is a new device in the field of medium and high voltage power distribution system.This article selects without transformer type shunt hybrid active power filter(transformerless shunt hybrid active power filter,TLS-HAPF)structure,the traditional repetitive control strategy(RC),a fast repetitive control method as well as the sliding mode variable structure control(SMC)method is studied.Its mathematical model is established.Also its effectiveness is verified by simulations and experiments.The specific research contents mainly include five parts:The main harmonic loads in the coal mine power supply system are elaborated,and the harm of harmonic to the mine power grid is analyzed.Then according to the current situation of harmonic suppression in the mine power supply system,from topology classification,harmonic detection method and current tracking control technology,research status and development trend of APF are analyzed,and the design goals of this subject are made.The structure of TLS-HAPF system and the principle of harmonic compensation are introduced,the filtering characteristics are analyzed in detail,the main circuit parameters are designed,the system control variables are selected and the circuit equations are derived,the excellent harmonic suppression ability of TLS-HAPF is proved by theory.The system control variables are selected,and the state mathematical models of TLS-HAPF are established for controller design.In this paper,the TLS-HAPF current control strategies are studied.In view of the insufficient steady-state precision compensation of traditional PI control,the theory of repetitive control(RC)strategy and the functions of each structure are detailly elaborated,and it is pointed out that its inherent periodic delay will increase the dynamic response time.Aiming at the problems of poor steady-state accuracy of PI control and slow dynamic response of traditional repetitive control,compound control strategy is adopted,which includes PI and RC.The parameters of the composite controller are designed and the stability of the system is analyzed.Simulation and experimental results show that the composite controller can preliminarily improve the dynamic response speed of the system.In order to realize rapid compensation,and to solve the problem that the dynamic response speed of composite control strategy needs to be further improved,a fast improved repetitive control strategy are proposed in this paper,according to the harmonic characteristics of TLS-HAPF that needs to be compensated.Through theoretical analysis,simulation and experimental verification,it can be seen that the improved compound control method can improve the sinusoidal degree of grid current,and has good steady-state accuracy and excellent dynamic performance.The basic principle of SMC is described,and the conditions for its establishment are given.Also the factors influencing the dynamic quality of the system in the two stages of arriving and sliding are also overturned.Under the equivalent control method,the error of the capacitor voltage,compensate current and DC voltage are selected as the system state variables,and the sliding mode control are designed,the controller parameters are designed under the exponentially reaching rate,and the stability of the system are analyzed,the simulation results show that the sliding mode control method has good speediness and robustness.According to the wiring diagram of the TLS-HAPF experimental system platform,the construction of the experimental platform is completed,and the design process of the software system is elaborated successively.For TLS-HAPF system,the start experiment,steady state experiment and dynamic experiment are carried out.