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Cascaded H-bridge (CHB) based active power filters (APF) can compensate high-order harmonics in medium and high-voltage systems with relatively low switching frequency. This paper reveals that a severe dc capacitor energy unbalance can be induced by harmonic energy exchange if the frequency of APF output current coincides with the switching harmonic frequency of CHB cells. The mechanism of harmonic...
In single-phase inverters, the proportional control is paralleled with the repetitive control to improve the dynamic performances. Meanwhile, in order to guarantee the stability of system, the static error cannot be eliminated in this control. This paper proposed an advanced scheme for the repetitive control to achieve zero error tracking. Taking the advantage of comb filtering by using Fourier transform...
Cascaded H-bridge multilevel converter based active power filter can compensate high-order harmonics (17th–50th) in middle-high voltage system with relatively lower switching frequency, but at the same time, a special DC capacitor energy unbalance problem is caused. When the compensation current frequency is close to the witching frequency of the H-bridge cell, harmonic power coupling will lead to...
Detecting the load currents is a basic control method of paralleled active power filter (PAPF). The stability and compensation effect of the system would be influenced by the interactions of the load, weak grid and the paralleled active power filter (PAPF), when the load can't be equivalent to an ideal harmonic current source. The impedance models are established to analyze the stability of the system,...
In a hybrid cascaded multilevel converter subject to different DC-link voltage levels among cascaded cells, should conventional carrier phase-shifting pulse-width modulation be applied, it will fail to multiply the equivalent switching frequency of the overall output voltage. As a consequence, this makes it more difficult to design the output filter and limits the overall output bandwidth. Based on...
Characterized by grid impedance variation and background grid voltage harmonics, weak grid may give rise to injected grid current distortion and cause stability issues in a grid-connected AC/DC converter. To lessen the effect, a composite compensation method is proposed in this paper based on output impedance model, which can increase control bandwidth and improve system's robustness against grid...
Multiwinding transformer + H-bridge converters is a typical topology in high-voltage and high-capacity power electronic applications. Based on the analysis about the high frequency characteristics of a PWM controlled H-bridge and the high frequency equivalent model of the topology, the theoretical foundation of how carrier phase-shift control suppresses high frequency harmonics is derived, and a broader...
This paper applies Boost Converter Control to the parallel operation of APF with multiple inverters. Master-slave control mode is adopted because of its prominent advantages on independent operation, redundancy control and cost-effectiveness. The malfunctioning of one APF will not influence the normal working of other APFs. In Boost Converter Control, the canceling of system harmonic current is equivalent...
This paper chooses the proportional resonant controller for the controlling of Active Power Filter, and proposed a new control topology for dual parallel APF application. The APF_I near the load side employs the proportional resonant controller to compensate the 5th, 11th, 17th and 23rd harmonics; The APF_II near the system side also employs the proportional resonant controller to compensate the 7...
The repetitive control, which is based on a delay of fundamental period, is widely used in grid-connected voltage-source converters, such as uninterruptible power supply (UPS), photovoltaic (PV) inverter and active power filter (APF). This paper presents four repetitive controllers in rotating frame for APF system, whose repetitive period is T, T/2, T/3, and T/6 respectively. Compared with traditional...
The repetitive control and resonant control are widely used in grid-connected voltage-source converters recently, such as uninterruptible power supplies (UPS), photovoltaic inverter (PV) and active power filter (APF). This paper introduces a new repetitive control strategy in APF system, whose repetitive period is only one half of the traditional and could eliminate all odd harmonics as a bank of...
Since LCL filter has smaller inductance value comparing to L type filter with the same performance in harmonic suppression. It is gradually used in high-power and low-frequency current-source-controlled grid-connected converters. However design of LCL filter's parameter not only relates switch frequency ripple attenuation, but also impacts on performance of grid-connected current controller. This...
As one of the most effective methods to inhibit electric power grid harmonics, the technology of Active Power Filter (APF) has been a key subject in the field of power quality control. Currently, research on APF mainly focuses on topology structure and control strategy. A novel topological structure of APF in alpha-beta coordinate is presented based on transformation of three phase static A-B-C coordinate...
A novel topological structure of Active Power Filter (APF) in alpha-beta coordinate is presented based on transformation of three phase static A-B-C coordinate to two phase static alpha-beta coordinate. The topological structure adopts two groups of single-phase inverter as main devices of APF, and can realize transformation of current source from two phases to three phases by using a special transformer...
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