Optimal Compensation of Delta-connected Dynamic Capacitor for Unbalanced Load

Wang, Qianqian; Dai, Ke; Chen, Xinwen; Tian, Tan; Dai, Ziwei

doi:10.1109/peac.2018.8590466

Cited by 3 publications

(4 citation statements)

References 13 publications

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“…Substitute (13) into (4) and compensation current i C (t) can be deduced as (14): (see (14)) where the (k + 1)th harmonic current i C_k+1 (t) can be decomposed into i C_k + 1 ′ t leading v n+1 by phase π/2 and i C_k + 1 ′′ t in phase with v n+1 , as expressed by (15):…”

Section: Power Balance Of D-cap With Series and Parallel Resonance Acmentioning

confidence: 99%

“…In the meanwhile, the other (k − 1)th, (2k − 1)th and (2k + 1)th harmonic currents i C_k−1 (t), i C_2k−1 (t) and i C_2k+1 (t), respectively, will not cause active power. According to (13) and (15), the active power absorbed by the (k + 1)th harmonic damping is expressed as (16):…”

Section: Power Balance Of D-cap With Series and Parallel Resonance Acmentioning

confidence: 99%

“…Furthermore, the interaction and coordination between the reactive compensation and harmonic suppression for buck‐type D‐CAP is discussed in [14]. For imbalance suppression, the optimal control is given, respectively, in [15, 16] for delta or star‐connected buck‐type D‐CAP to compensate for the maximum unbalanced load.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Series and parallel resonance active damping of three‐phase buck‐type dynamic capacitor for reactive compensation and harmonic suppression

Chao

Chen

Dai

et al. 2020

IET Power Electronics

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Series and parallel resonance tend to occur and cause harmonic distortion when the distribution system contains a shunt power capacitor to compensate inductive load and dynamic capacitor (D-CAP) to suppress harmonics. This study focuses on the series and parallel resonance active damping of three-phase buck-type D-CAP, so as to achieve better power quality control. Two virtual resistor damping methods for series resonance, D-CAP power capacitor voltage or D-CAP front-end buffer inductor current feedback, are introduced and compared. Then, parallel resonance is damped by generating certain harmonic currents in the phase with the selective harmonic voltage at the point of common coupling (PCC), equivalent to controlling the D-CAP as a virtual harmonic resistor. In addition, the power balance of D-CAP is interpreted to ensure no additional energy control loop is needed for the active damping. To further improve the parallel resonance damping, the self-adjusted damping gain is proposed by the closed-loop regulation of harmonics in PCC voltage. Finally, coordinated control between reactive and multiple harmonic currents is introduced for the whole combined control to avoid over-modulation. A wide variety of experimental results from a 33 kVar/220 V laboratory prototype are provided to demonstrate the validity of the combined control.

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Section: Power Balance Of D-cap With Series and Parallel Resonance Acmentioning

confidence: 99%

Section: Power Balance Of D-cap With Series and Parallel Resonance Acmentioning

confidence: 99%

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Series and parallel resonance active damping of three‐phase buck‐type dynamic capacitor for reactive compensation and harmonic suppression

Chao

Chen

Dai

et al. 2020

IET Power Electronics

Self Cite

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show abstract

“…Furthermore, interaction between reactive compensation and harmonic suppression for three-phase Bucktype D-CAP is discussed and a coordination control is designed in [16]. For imbalance suppression, optimal control strategies are given respectively in [17], [18] for delta and star-connected Buck-type D-CAP to compensate the maximum unbalanced load based on capacitive compensation.…”

Section: Introductionmentioning

confidence: 99%

Reactive Current Reshaping With Series Resonance Damping for Three-Phase Buck-Type Dynamic Capacitor

Dai

Chen

et al. 2019

IEEE Access

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By adding Buck-type AC/AC converter to conventional power capacitor, dynamic capacitor (D-CAP) can be formed to compensate variable rather than fixed reactive power. However, some nonlinear distortion factors, namely grid harmonic voltage, voltage drop of switches and dead-time, would cause harmonics in its compensation current, meanwhile, its capacitance may interact with the grid inductance to cause series resonance. Both nonlinear distortion factors and series resonance would distort the waveform of its compensation current and make the grid current failed to meet the power quality standard IEEE Std.519. This paper focuses on the output current distortion of Buck-type D-CAP in reactive power compensation. For harmonic distortion, through establishing the equivalent circuit of Buck-type D-CAP, the generation of low-order harmonic current is investigated under three nonlinear factors. A current reshaping method to simultaneously diminish the harmonics caused by the three nonlinear distortion factors is thus adopted, which is a feedback control of output current harmonics. Then for series resonance, based on the block diagram of Buck-type D-CAP within the grid, transfer function from grid voltage to the output current is deduced and the corresponding Bode diagram is depicted. An active damping method is therefore suggested to shrink the low-order series resonance peak, by detecting power capacitor's voltage for feedback control. Finally, a combined control, reactive current reshaping with series resonance damping is proposed in this paper for three-phase Buck-type D-CAP. A wide variety of experimental results from a 33kVar/220V laboratory prototype are provided to demonstrate the validity of the combined control.INDEX TERMS Buck-type dynamic capacitor, reactive power compensation, waveform distortion, current reshaping, series resonance damping.

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Reactive Power Compensation and Imbalance Suppression by Star-Connected Buck-Type D-CAP

et al. 2019

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Reactive power and negative-sequence current generated by inductive unbalanced load will not only increase line loss, but also cause the malfunction of relay protection devices triggered by a negative-sequence component in the power grid, which threatens the safe operation of the power system, so it is particularly important to compensate reactive power and suppress load imbalance. In this paper, reactive power compensation and imbalance suppression by a three-phase star-connected Buck-type dynamic capacitor (D-CAP) under an inductive unbalanced load are studied. Firstly, the relationship between power factor correction and imbalance suppression in a three-phase three-wire system is discussed, and the principle of D-CAP suppressing load imbalance is analyzed. Next, its compensation ability for negative-sequence currents is determined, which contains theoretical and actual compensation ability. Then an improved control strategy to compensate reactive power and suppress imbalance is proposed. If the load is slightly unbalanced, the D-CAP can completely compensate the reactive power and negative-sequence currents. If the load is heavily unbalanced, the D-CAP can only compensate the positive-sequence reactive power and a part of the negative-sequence currents due to the limit of compensation ability. Finally, a 33 kVar/220 V D-CAP prototype is built and experimental results verify the theoretical analysis and control strategy.

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Optimal Compensation of Delta-connected Dynamic Capacitor for Unbalanced Load

Cited by 3 publications

References 13 publications

Series and parallel resonance active damping of three‐phase buck‐type dynamic capacitor for reactive compensation and harmonic suppression

Series and parallel resonance active damping of three‐phase buck‐type dynamic capacitor for reactive compensation and harmonic suppression

Reactive Current Reshaping With Series Resonance Damping for Three-Phase Buck-Type Dynamic Capacitor

Reactive Power Compensation and Imbalance Suppression by Star-Connected Buck-Type D-CAP

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