Based On The Cic Decimation Filter Power System Harmonic Analysis Algorithm And Dsp Implementation

With the development of science and technology and economies, the harmonic pollution of power system is getting more and more serious, while more and more qualified electrical power is required. In order to minitor and contol the harmonic pollution, precise harmonic analysis and measurement are seriously needed.In the paper, firstly, while producing the FFT(Fast Fourier Transform) algorithm, the problems spectrum leakage and fence effect caused by it when applied to harmonic analysis are deeply analysed. Secondly, by research in asynchronous sampling and existing harmonic analysis algorithms, a CIC(Cascaded Integrator Comb) decimation filter based harmonic algorithm is propsed. In the case of ADC over-sampling, the signal is truncated to a single cycle, then CIC decimation filtered. Therefore, the sampling frequency is reduced without aliasing. After FFT unit, the amplitude, frequency, and phase of harmonics are obtained. In the process of studying the proposed algorithm, two good methods are presented. One is integral cycles truncation method using segment matching. The other is the method that decimating factor is calculated dynamically when it is not an integer.In the hardware design of the proposed algorithm, a dual-CPU structure DSP+MCU is applied, with MCU as host and DSP as slave. STC89C54RD+, selected for MCU as the host CPU in the system, is mainly used for three functions: 1) Control and communicate with DSP slave. 2) Human-Computer Interface, including LCD display and keyboard input. 3) Communicate with the PC, so that commands and data can flow between MCU and PC. TI's DSP chip TMS320VC5402 is applied, the functions of which mainly inlude collecting voltage and current data of power system signals, processing the data with the proposed algorithm and related calculations. In the analog circuit for data collection, detection and ajusting circuits and high speed A/D circuits for multiple channels voltage and current signals are designed. The software of the system, well following the modulation principle, in which software flows and fuctions of the main modules are designed, and among which, modules related with the core algorithm, such as the integral cycles trunction method and the method of the calculation of decimation factor, are specially studied, and software flow chart and part of the code are listed.Through software verification and data analysis of circuits and the proposed algorithm, the CIC decimation filter based harmonic analysis algorithm is proved to be effective and of good analysis precision.