Research On Digital Power Amplifier Based On Self-adaptive Prediction Control

In digital physical hybrid substation simulation system，primary system usingdigital simulation，while real device is used to secondary system. Digital signal fromdigital simulation model can not drive real device，it is need to convert digital signalto analog signal and meet the requirement of power，then the analog signal can drivethe secondary equipment，such as relay protection and automatic control device. Asthe conversion link of digital simulation model and real device，digital poweramplifier convert digital signal to pulse-width modulation signal so that drive theinverter，inverter can output analog signal after filtering，the connection between thedigital simulation and the physical model in hybrid simulation is achieved. In thispaper，an efficient and inexpensive digital power amplifier is developed.According to the characteristic of hybrid substation simulation system，overallplan of digital power amplifier is designed on the basis of comparative analysis ofseveral conventional power amplifiers. In order to improve system security，faultdetecting and protection circuit apart from the inverter and driving circuit is added inthe main circuit. Instruction current and actual current is collected into the controlsystem to compute algorithm. The FPGA output control signal to drive the maincircuit to get waveform required.For the control strategy of digital power amplifier，least square method is used toonline estimate filter inductor and load parameter of digital power amplifier.According to the instruction current，together with the relationship between the outputcurrent in switching cycle and the average voltage provided by switch，on-off time ofswitch is determined.For the large calculations of self-adaptive predictive control，control system is setup with field-programmable gate array EP3C25Q240C8and a less pipeline stagesmultiply-accumulator is developed，greatly improve the speed of algorithm execution.According to the design flow of FPGA，the control algorithm of digital poweramplifier in FPGA is divided into three modules: AD sampling，parameter estimation，and model predictive control.Finally，the joint debugging of hardware and software systems is finished. Theresults show that the developed digital power amplifier has the fast response and high control accuracy.