Research Of Active Power Filter Based On DSP

A high-speed signal processor DSP used as main controller, high power switching device IGBT used as action element, utilizing synthetically PWM wave control technology﹑optical fiber transmission technique and instantaneous reactive power theory, a new generation of active power filter was researched in this article.The system detects firstly some current & voltage parameters of electric net by current & voltage sensor, collects these parameters to main controller by high precision A/D, calculates instruction current of compensation by instruction current arithmetic unit, sends out PWM control signal, then amplifiers signal and passes it to IGBT driving circuit using optical fiber of strong anti-interference, obtains compensation current. Compensation current and harmonic current offset, also accomplish function of compensating harmonic current.The hardware of parallel active power filter described in this paper is made up of signal collection isolation circuit,instruction current calculation and tracking control system,IGBT variable current bridge main electro circuit. In order to lower system cost, signal collection isolation circuit uses high-speed,low non linearity optocoupler HCNR200/1 instead of isolation amplifier ISO124; because of the contradiction between much data operation and whole system real-time requirement, instruction current calculation and tracking control system use DSP TMS320VC33 which has high-speed floating point processing ability; To improve the reliability of main circuit driving part and simplify hardware circuit layout ,it use high integration driving chip 2SD315A and optical fiber transmission to inhibit high-frequency current electromagnetic interference.The design of software detects real-time harmonic current by ip-iq arithmetic mode based on Instantaneous Reactive Power Theory, including digital filter,hysteresis control arithmetic and so on; in order to ensure reliability and security of system, software method realizes some functions, for example DC Link Capacitance Voltage control and protection,power network voltage overtension and current overload protection,external-interrupting protection and so on.Active power filter model machine based on Three Phase Three Wire power system has been tested successfully in the laboratory, it can improve effectively waveform of electric-network and decrease total harmonic wave distortion rate THD, so it has strong inhibition effect to power network voltage and current distortion caused by rectifiers,frequency conversion equipment,electrical arc furnace and so on.