科研之友
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摘要
Due to the limitation of voltage capability and current capability of power devices, it is very difficult to handle nonlinear loads for the traditional active power filter (APF) with two-level inverter in high voltage high power grid. Three-level NPC inverter has been put into practical use for years especially in high voltage high power grid. This paper researches the APF with three-level inverter and presents a close-loop digital control algorithm of DC voltage for the APF. In dq two-phase rotating coordinate, this paper divides the control system of DC voltage into the outer-loop voltage controller and the inner-loop current controller. In the outer-loop controller, the mean value of DC voltage is detected by the adaptive filter and regulated by the PI controller using active command current. In the current-loop controller, this paper researches the issues of neutral-point voltage control from the space vector PWM (SVPWM) point of view in detail. Then this paper proposes a simple neutral-point voltage control method that requires the knowledge of the current direction in each phase and the neutral-point voltage ripple';s direction. Based on that information, the small vectors that will move the neutral-point voltage in the direction opposite from the direction of unbalance can be selected. The experiment results illustrate that the performance of the proposed approach is satisfactory.
- 出版日期2008
- 单位华中科技大学
