Structure and basic principle of shunt active power filter
Principle of shunt active power filter system, load to produce harmonic harmonic sources, converter and connected with the inductor, DC storage can components (capacitors) composed of the main circuit of active power filter. Small capacity first order high pass filter (or two order high pass filter) in parallel with the active power filter, which is used to filter out the harmonics near the switching frequency in the compensation current generated by the active power filter.
1 current tracking control circuit current tracking control
Circuit is a current compensation circuit in the first part, its role is according to the relationship between the actual compensation current and the compensation current instruction signal, it is concluded that the control current compensation occur circuit in the various devices of the main circuit through fault of the PWM signal, control results should ensure that the compensation current track changes in the command signal.
Real-time follow the instruction current signal changes due to shunt active power filter to generate a compensation current stress, compensating current generator has good real-time performance, so the current control by tracking PWM control mode. At present, there are two main methods of tracking PWM control, namely instantaneous value comparison method and triangular wave comparison method.
Triangle wave comparison method is not directly command signal Ci and triangular wave comparison, but the deviation of the CI and the actual compensation current signal C I C delta I after a amp again and triangular wave comparison. Although the switching frequency is fixed, and the frequency of the triangular carrier is equal to the frequency of the triangular carrier, the following error is large, but the output voltage contains less harmonic characteristics, so this paper adopts the triangular wave comparison method.
2 APF main circuit structure
DC side voltage type PWM converter is connected with a large capacitor. In normal operation, the voltage remained basically unchanged, as voltage source; current type PWM rectifier DC side is connected with a large inductance, in normal operation, the current remained basically unchanged, as a current source; for voltage type PWM converter for DC side voltage unchanged, need to control the DC side voltage; the same for the current type PWM rectifier also need to on the DC side of the current control. Compared with the current mode PWM converter, the current mode PWM will not be short circuit fault because of the direct current of the main circuit switch device. But large inductance current type PWM rectifier DC side there is always current flows through, the current will be in the internal resistance of the inductor produced greater loss, so currently used less.
Active power filter in practical applications often require large capacity, if the use of a single PWM converter can not meet the capacity requirements, usually using multiple main circuit. The main circuit of the active power filter using a single PWM converter can be divided into two types of voltage and current, according to the different energy storage elements.
For the main circuit, the voltage type PWM converter is used in this paper. For the DC side capacitor, this paper uses 2000V DC voltage source instead of.
The role of 3 command current calculating circuit command current calculating circuit is obtained according to the purpose of active power filter compensation command signal of compensation current, spot at produced by active power filter compensation current signal. The core of the instruction current operation circuit is the real-time detection method of harmonics and reactive currents. Based on the theory of instantaneous reactive power of three-phase circuit, the two methods of P, Q, Qi and PI are calculated to detect the harmonic and reactive current of three-phase circuit. The following describes the PI, Qi algorithm.
1 current tracking control circuit current tracking control
Circuit is a current compensation circuit in the first part, its role is according to the relationship between the actual compensation current and the compensation current instruction signal, it is concluded that the control current compensation occur circuit in the various devices of the main circuit through fault of the PWM signal, control results should ensure that the compensation current track changes in the command signal.
Real-time follow the instruction current signal changes due to shunt active power filter to generate a compensation current stress, compensating current generator has good real-time performance, so the current control by tracking PWM control mode. At present, there are two main methods of tracking PWM control, namely instantaneous value comparison method and triangular wave comparison method.
Triangle wave comparison method is not directly command signal Ci and triangular wave comparison, but the deviation of the CI and the actual compensation current signal C I C delta I after a amp again and triangular wave comparison. Although the switching frequency is fixed, and the frequency of the triangular carrier is equal to the frequency of the triangular carrier, the following error is large, but the output voltage contains less harmonic characteristics, so this paper adopts the triangular wave comparison method.
2 APF main circuit structure
DC side voltage type PWM converter is connected with a large capacitor. In normal operation, the voltage remained basically unchanged, as voltage source; current type PWM rectifier DC side is connected with a large inductance, in normal operation, the current remained basically unchanged, as a current source; for voltage type PWM converter for DC side voltage unchanged, need to control the DC side voltage; the same for the current type PWM rectifier also need to on the DC side of the current control. Compared with the current mode PWM converter, the current mode PWM will not be short circuit fault because of the direct current of the main circuit switch device. But large inductance current type PWM rectifier DC side there is always current flows through, the current will be in the internal resistance of the inductor produced greater loss, so currently used less.
Active power filter in practical applications often require large capacity, if the use of a single PWM converter can not meet the capacity requirements, usually using multiple main circuit. The main circuit of the active power filter using a single PWM converter can be divided into two types of voltage and current, according to the different energy storage elements.
For the main circuit, the voltage type PWM converter is used in this paper. For the DC side capacitor, this paper uses 2000V DC voltage source instead of.
The role of 3 command current calculating circuit command current calculating circuit is obtained according to the purpose of active power filter compensation command signal of compensation current, spot at produced by active power filter compensation current signal. The core of the instruction current operation circuit is the real-time detection method of harmonics and reactive currents. Based on the theory of instantaneous reactive power of three-phase circuit, the two methods of P, Q, Qi and PI are calculated to detect the harmonic and reactive current of three-phase circuit. The following describes the PI, Qi algorithm.
| Datetime：2016.03.29 From： Views：