Key Technology Of The Adjustabel Speed Pumped Storage Control System With AC Excitation

Adjustable speed pumped storage units using AC excitation motor as a generator-motor,has characteristics such as faster response and large energy storage.These are effective means to guarantee the power quality and eliminate the volatility of new energy power.Japan and Europe have pioneered the development of the adjustable speed pumped storage technology.However,research in this technology has just begun and there are no practical applications in our country.In this paper,the key control technologies of adjustable speed pumped storage units are studied.The main contents are as follows:(1)For the particularity of the flux control parameters and harmonic problems to the AC excitation system of the large-capacity adjustable speed pumped storage,voltage model flux observer based on the proportional and resonant controller is proposed.Resonant controller is used to eliminate the influence of harmonics problems,and amplitude and phase angle compensation is used to correct the flux.The simulation and experimental results show that the method can effectively solve the windup problem of the conventional voltage model.What’s more,it has high precision in steady state and better performance in dynamic state.And even at low frequencies,it can accurately obtain the position angle of the flux.(2)Hardware,that is to say,digital control system of cycloconverter is the basic of the research.Therefore,this paper developed a new digital control system of cycloconverter which is used to provide the AC excitation to the adjustable speed pumped storage units.This control system is based on multi-layer control,VME bus,DSP and FPGA.The system has been proved to be stable and reliable in the industrial field and it has established a technical basis to the development of large adjustable speed pumped storage units.(3)Key technology of the control of the excited rotor current for the adjustable speed pumped storage units is studied.To solve the non-linear and digital delay problems,method combining the fuzzy proportional and deadbeat control is proposed.Experimental results show that the conventional control method does not have a satisfactory effect and it gets worse because of the presence of the control delay.The proposed method uses big gain when the current is discontinuous,so the control effect becomes better without oscillation.In addition,with the deadbeat algorithm,current distortion significantly reduced.(4)Start problem in the motor mode of the adjustable speed pumped storage units is studied,and the key problem is initial position angle detection.In order to obtain accurate initial position angle of the units,a method using phase-locked loop(PLL)and filters based on resonant controller is proposed.The initial rotor position angle is obtained by comparing the injection rotor voltage and the induced stator voltage.Resonant controller is used to eliminate the influence of harmonics problems in stator and rotor voltages,and PLL is used to calculate the voltage vector angles.Experimental results show that the method can accurately obtain the initial position of the rotor and the angle of error does not exceed 1.6%.(5)Due to the operating characteristics of the adjustable speed pumped storage unit with AC excitation,active and reactive power control using active disturbances rejection controller(ADRC)is study.Experimental results show that the speed,active and reactive power can be adjusted independently.And automatic frequency control function of the units is also achieved.In order to improve the fault tolerance ability of the system,a simple and low cost method of redundancy control is studied.