Analysis Of SVPWM In The Context Of Nonorthogonal Coordinates And Study On The Hybrid Active Power Filter

The PWM technology is a global technique applied to the control of voltage source inverters(VSI), and its basic theory can be classified into the pulse area equal principle based on time and equivalent vectors principle based on space. SPWM is a typical PWM mode based on the former theory and can be easily realized, whereas results in lower output capability of inverters because of dissevering intrinsic relations among bridges as well as independently analyzing the output status of each bridge. Comparatively, SVPWM is another typical PWM mode based on the latter one. Although it uniformly deposits total bridges in the same space to gain favorable output capability, it is difficult to be carried out that complicated computation and real-time control when levels of inverters increase.Complicated computation of SVPWM conceals its essence, thus internal relations between pulse area equal principle and equivalent vectors principle are difficult to be established . As a result, a uniform directive idea on realization of PWM mode does not exist. Therefore, the following researches are carried out in the paper. At first, typical PWM modes based on pulse area equal principle are summarized, PWM modes based on phase voltage and line voltage are definitely proposed, and then an optimized PWM mode based on line voltage is concluded. Not only can this mode improve dc voltage utilization ratio of inverter side, but also efficiently reduced switch frequency. As for two-level SVPWM mode, that conventional solutions are not exhaustive is firstly pointed out in the papers. After trigonometric function used in simplifying solutions, a simple algorithm is deduced. The algorithm avoids non-linearity operations relevant to the conventional algorithm during the solutions, and in theory error of computation is zero. By mathematical deduction, the author proves that the optimal common mode PWM mode is an especial form of SVPWM. As for multi-level SVPWM mode, that an unsuitable coordinate to be chosen is the essential reason that results in complicated computation is firstly pointed out in the papers, and in addition a novel nonorthogonal coordinate-- KL coordinate is established. Uniform and simplified algorithm of multi-level SVPWM mode is found out on the coordinate, which enables only a small quantity of multiplication and addition operations to be performed during the whole solutions. This algorithm is a general solution of multi-level SVPWM mode, and can be constantly applied into any level inverter fields. This part of productions are the basis of real-time control realization of multi-level SVPWM mode. the author successively extends the simplified algorithm from linear modulation fields to over-modulation fields. In KL coordinate, physics meaning of multi-level SVPWM mode is analyzed. The pulse area equal principle based on time and the equivalent vectors principle based on space to be considered, the relations between them are established by accurate mathematical deduction and a conclusion that SVPWM is a subclass of line voltage PWM is presented. As non-linear pontes circuits between the supply and the facilities, power electronic devices inevitably inject harmonics into power network. On contrary, the development of electric technology provides abundant measures that can be applied into suppressing harmonics. Among these measures, active power filter is one of the most valuable researches. The research on harmonics and reactive power compensation technology are carried out in the papers in order to provide theoretic guidance for promoting APF into practice. As for shunt hybrid APF, that operation characteristics of lower dc voltage in its inverter side are explained in details in the papers, and current tracking control course based on deadbeat control theory is implemented . In order to prevent dc offset appeared on capacitor voltage of series passive power filters, the author presents dc component modulation of output currents based on PI control. For application into high voltage network, technology advantage of shunt...