Research And Design Of Power Quality Standard Source Based On FPGA

With the development of national economy,the quality requirements of power consumption are increasingly higher.For power quality monitoring,analysis and management equipment,performance verification is an important part to ensure its operation reliability and accuracy.Power quality standard source is the core tool in performance verification and its accuracy and stability play a key role in the outcome of performance verification.At present,the power quality standard source is mainly developed based on power electronics inverter technology and direct digital frequency synthesis(DDS)technology.The former can output high power,but the type of output waveform is fixed.DDS can output any waveform,but there are some problems,such as low output accuracy and high spurious and background noise in the output signal spectrum.Based on the existing problems in the design of power quality standard source,this paper studied and designed a new power quality standard source based on DDS,the hardware and algorithm design are optimized and improved to meet the requirements of high accuracy and stability.The main contents of this paper are as follows:(1)The working principle of DDS is analyzed and studied,the frequency spectrum of DDS output signal is analyzed,the effects of phase truncation error and amplitude quantization error on the output signal are analyzed quantitatively,so as to select appropriate phase truncation digit and amplitude quantization digit.In view of the shortcomings of traditional DDS technology that can not output any frequency accurately,a compound frequency control word method is introduced to improve DDS which was allowed to output any frequency signal accurately.(2)Field programmable gate array(FPGA)is used to replace the special DDS chip to realize the DDS function,so as to improve the flexibility of DDS output signal.Based on the high-power integrated operational amplifier,the voltage and current amplification circuits with excellent performance are designed to ensure that the system can output any waveform and simplify the circuit design.(3)Based on the modular design idea,the standard source system is divided into signal generation module,voltage amplification module,current amplification module,feedback control module,human-computer interaction module,protection module and power module,and the power quality standard source test system is built.The function of the developed standard source system was verified,the test results show that the standard source designed in this paper can generate many kinds of power quality signals without distortion.In sinusoidal steady state,the deviation of voltage effective value is better than 0.05%,the deviation of current effective value is better than 0.1%,and the deviation of frequency is lower than 0.0002 Hz,the stability and accuracy of the output signals can reach a high level.It is suitable for performance verification of power quality monitoring,analysis and treatment equipment.