Reseach And Design Of Bidirectional Power Metering And Harmonic Detection System Based On DSP

With the distributed power supply for home users' access to the grid,and the working mode of spontaneous self-used or surplus feedback,making the power flow becoming bidirectional in distribution network.Besides,a tremendous number of power electronic equipment has become the main body of residential electricity,such as microwave oven and computer and energy storage tank of rectifying device etc.Therefore,the power metering device under non-sinusoidal condition needs a more fair and reasonable measurement scheme and method,and monitor the power quality of users to make different charging strategies simultaneously.The bidirectional power measuring of distributed power supply is focused on active metering.In this paper,the traditional metering port is used as the measuring point,and the direction of bidirectional power is determined by combining the 1th power direction with the four quadrant power definition.The traditional power theory and measurement method are based on sine wave,non-sinusoidal harmonics will cause the meter measurement inaccurate and unfair.In this paper,the effects of three kinds of power theory in frequency domain,time domain and frequency domain are analyzed and compared,and the MATLAB simulation analysis is carried out.Combining with the definition of background harmonic and reflected harmonics in current physical component power(CPC)theory,we propose a comprehensive measurement scheme.That is,when the microgrid flow is positive,the 1th active power,the background harmonic active power,the reflected harmonic active power,the reactive power are measured.When the microgrid flow reversed,the 1th active power and harmonic active power are measured.In this paper,the FFT method is used for harmonic detection and power calculation.The causes of spectrum leakage and fence effect are analyzed,and the window function and the detection accuracy are also discussed.Aiming at the problem of asynchronous sampling,we use the method of time domain multiplication Hanning window to construct three cosine combination window,and analysis the time and frequency characteristics of each passenger window,and compare it with Hannning window and 4 Rife-Vincent window by the simulation.An improved FFT algorithm of double-spectrum-line interpolation based on multiplicative Hanning window is simulated,the result show that the method can effectively overcome the influence of frequency fluctuations,and can obtain a high metering accuracy when measuring harmonic parameters and power.Based on improved FFT algorithm of double-spectrum-line interpolation and multiplication Hanning window,this paper use TMS320F28335 DSP and AD7606 hardware architecture to make a research and development of a power metering and harmonic detection integration device,and complished the design of hardware and software system,maked and debugged the peripheral circuit.Explicated the hardware chip resource allocation,core circuit,high frequency signal acquisition circuit and communication circuit.According to the modular design process,this paper design and debug main program,electrical parameter calculation program and serial communication program,at the same time,the data is uploaded to DSP by DMA to ensure the real-time performance.The man-machine interface is designed by cMT-SVR host computer,which is convenient for users to view the information of electric quantity in real time.Finally,combined with the existing laboratory equipment,the experiment results show that the system can realize the function of acquisition and detection,harmonic analysis and power calculation.