Research On The Control Technology Of Diode Clamp Three-phase Three-level Shunt Active Power Filter

The power electronics industry and swift growth and the advent of high-end electronic products have caused a surge in the number of non-linear loads connected to the power grid.The load and harmonic and reactive current has had a drastic effect on the power system and normal functioning,leading to a drastic decrease in power quality.To address this issue of harmonic pollution,it is essential to investigate the dynamic compensation harmonic current of active power filters.To validate the feasibility of the research experiment,which was conducted with the Matlab Simulink simulation platform,an active power filter experiment platform was constructed.The primary focus of this thesis is the diode clamped three-level shunt active power filter,and several essential technologies,such as main circuit topology,harmonic detection technique,current tracking control strategy,DC voltage regulation control,and midpoint potential balance control,are examined.A thorough examination of the various active power filters is conducted in this thesis,with a diode-clamped three-phase three-level inverter as the primary circuit topology.A comparison of them is then made.Furthermore,a mathematical model of the switching state of these three-level active power filters in both abc and dq coordinate systems is established.The first step to suppressing harmonic current in active power filters is the accurate extraction of harmonic current from the power grid.The p-q harmonic detection method,which is simpler to implement and more precise in its extraction of harmonics,is the basis for the i_p-i_q harmonic detection method.This thesis contrasts and examines the two approaches based on the research and development of instantaneous reactive power theory.The control of an active power filter is divided into two sections in this thesis.DC side voltage regulator control is achieved by employing the PI control strategy,which superimposes the current signal after PI control on the active current component of load measurement.This is the first of two control strategies:voltage outer loop control(also known as DC side voltage regulator and neutral point potential balance control)and compensation current control(or current inner loop control).After analyzing and comparing the hysteresis control strategy,PI control strategy and multi-resonant quasi-PR control strategy,the multi-resonant quasi-PR control strategy with high control precision and fast dynamic response is selected.After constructing a system framework and constructing an experimental platform,the harmonic compensation control experiment of a diode-clamped three-level APF was conducted.Matlab Simulink was used to simulate hysteresis,PI,and multi-resonant quasi-PR control strategies,and the difference between them was compared.THD data was used to assess the suppression effect of harmonic in the power grid of the active power filter under the three control strategies,verifying their feasibility.The dynamic response performance of the active power filter under multi-resonant quasi-PR control strategy was then evaluated using the experimental waveform.It was concluded that multi-resonant quasi-PR compensating current control strategy had a superior effect than hysteresis control and PI controlling current control strategy.