The Application Of DSP In Power System Harmonic Detection

With the extensive application of the electric and electronic devices in recent years, the harmonic pollution is more and more serious.The quality of electric energy is badly influenced by the harmonics, which is also harmful to the power equipment operation. The harmonic pollution control is inevitable, and the most important problem to solve is harmonic detection and analysis.There are difficulties in performing synch-ronized sampling and integral period truncation in the harmonic analysis of power system with the fast Fourier transform (FFT) technique. However, not to satisfy these conditions, the results will be disturbed by the frequency-leakage. Some efforts have been made including the utilization of window functions and interpolation algorithms to correct the measured frequency, phase and amplitude by FFT. The polynomial approximation method is also employed to obtain simple formulas for frequency and amplitude correction.By these methods, the disturbance of the frequency leakage and the noise can be reduced and the accuracy of the harmonic analysis can be improved.With the development of technology with the digital signal in recent years, people gradually incline to adopt DSP (a high-speed microprocessor) to carry out the detection and control of the harmonic wave more and more. Compared with traditional analogue technology, digital control do not need the multiplier which is independent of the system, which can either simplify the design, or dispel the inherent temperature drift and environment interfere that the artificial circuit has. And it also can improve the precision of controlling, it is apt to realize advanced control, and can reduce the circuit cost. It is easy to maintain and upgrading, and to realize commercial production.DSP is brought into the APF for harmonic detection. TMS320F240 of TI Corp.has been adopted, which is integrated AD converter, general timer, comparative units, PWM circuit, capture unit and so on.Through the simulation in MATLAB, it is verified that the improved FFT is effective and feasible, and higher harmonic and transient harmonic detection is realized by introducing the DSP.