Research On The Hybrid Active Power Filter Based On The Instantaneous Reactive Power Theory

With the rapid development of electrified railway,electric traction loads increase quickly. As the large power single-phase rectified load,electric traction load is typical harmonic source. And its current has many disadvantages such as heavy distortion,acute fluctuation and severe asymmetry. It causes the harmonic pollution of the power,and the safe and economic operation of power systems and other users in points of common coupling is badly influenced. Therefore,the research on harmonic elimination scheme for electric traction load is becoming a hot subject in recent years.The basic principles and topology of the active power filter (APF) are introduced in this paper. And also the filter theory is analyzed. The electrical model of hybrid power filter system is established. The filter theory of hybrid APF and its characteristics are discussed in different control strategies.The harmonic current detection of APF decides its compensation performance. The detection method based on the instantaneous reactive power theory is widely applied in APF device. In this paper,several detection methods are discussed for APF, and the detection method based on instantaneous reactive power theory is analyzed specially. By MATLAB simulation, it can be concluded that the method based on instantaneous reactive power theory is on fit for the electrified railway supply system because of its quick response velocity and little delay.Compensating current control is the core link to accomplish the various functions of active power filter. Triangle-wave modulation control, Hysteresis control, Deadbeat control and Space vector PWM control (SVPWM) are elaborated in the text. SVPWM is applied in hybrid active power filter control by analyzing the control process.To verify the feasibility of the harmonic current detection method and compensating current control method, this paper simulates single phase hybrid active power filter used in the electrified railway supply system in MATLAB7.0. The simulative result shows that the instantaneous reactive power filter combined SVPWM can filter a majority of the electric locomotive harmonic current and lower THD of the source current. Furthermore, the hybrid active power filter possesses good dynamic capability and synthetical compensation.