The Study On Key Technology For Active Power Filters With Neutral-point Clamped Three-level Inverter

The Electricity is one of the most important energy in modern construction. Itis the main driving force of economic development in China. With the wide use ofall kinds of electrical equipment, it promoted industrial production and the qualityof life and brought a lot of power quality problems at the same time. the harmonicpollution and power factor correction is one of the main performance. The activepower filter is a kind of effective dynamic suppress harmonic and compensatingreactive power electronic device, therefore, the APF has a good application prospectin power quality control. In the middle and high voltage power distribution system,the high voltage large capacity of APF is urgent demand. this paper studies the threewire shunt APF system key technology based-on the diode clamp type three levelconverter and its specific implementation methods, mainly include the followingseveral aspects:First of all, the causes of harmonic current and its harm is presented, andexpounds the development status of high voltage active power filter, and then putsforward adopting multilevel inverter technology to expand the capacity of activepower filter. Research status of multilevel converter is presented. Finally choosediode clamping type three-level converter as the main circuit topology of highvoltage APF.Second diode clamping three-level inverter working principle and commonseveral kinds of PWM control technology are analyzed, and discussed why dc neutralvoltage balance problems are the inherent problems. This paper analyzes thethree-level SVPWM modulation technology basic principle, implementation methodand simulation techniques, and puts forward a new dc neutral voltage balance controlmethod which based on three-level SVPWM control technology.Then base principle of the three-level APF is analyzed. And establish the dqcoordinate system mathematical model, and then puts forward a new no differencefrequency control technology to achieve the real-time tracking compensation of theharmonic current. This paper analyzes the basic principle of p-q and iq-iq harmoniccurrent detection method which based on instantaneous reactive power theory, anddesign the dc filter capacitor. Finally according to the function requirements of the APF, planning the controlsystem hardware structure, and design the sampling and control circuit board, andwrite software program. Build the APF prototype for harmonic suppression andreactive power compensation experiment. The experimental results show thecorrectness and validity of the key technology of APF which described in this article.