Bandwidth Expansion Method for Circulating Current Control in Parallel Three-phase PWM Converter Connection System

Zhang, Xueguang; Chen, Jiaming; Ma, Yuanming; Wang, Yijie; Xu, Dianguo

doi:10.1109/tpel.2014.2311046

Cited by 95 publications

(14 citation statements)

References 25 publications

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“…2(b). Therefore, in order to suppress the ZSCCs, we can adjust the relative duration of Pand N-type small vectors in pairs to make the AZSVs of parallel 3LT 2 Cs identical, just like the proposed method in [24] is to adjust the distribution of zero vectors of SVPWM by zero-sequence PI controller in parallel 2LC system, which has been proved to be easy to realize and accomplish good control effect in [25,26]. However, this method cannot be directly applied in the parallel-connected 3LT 2 Cs due to the complexity of AZSVs generated by three-level SVPWM.…”

Section: Analysis Of the Characteristics Of Svpwm For Zsccsmentioning

confidence: 99%

“…Moreover, if parallel system is equipped with TPSIs, we can extend the proposed method in [24] to suppress the remaining low-frequency ZSCCs by the closed-loop control. Note that, the disadvantage of the proposed method is that at a high modulation index range when the system saturates, the zero-sequence voltage of the follower converter cannot exactly follow the zero-sequence voltages of the master converter due to the lesser duration in the utilization of redundant vectors, which suffers the same limits as the two-level parallel case that suppress the ZSCCs by adjusting the distribution of the zero-vectors with the open-loop controller [22][23] and close-loop controller [24][25][26].…”

Section: Suppression Of the Remaining Low-frequency Zsccsmentioning

confidence: 99%

“…One approach is to remove the AZSV of each converter by modified SVPWM [20], selective harmonic elimination pulse width modulation [21], etc. Another approach is to remove the differences in the AZSVs between parallel-connected converters by open-loop control methods [22,23], closed-loop control methods based on SVPWM [24][25][26], etc. However, these strategies are based on TSPIs without taking magnetic circuit characteristics of 3P3LIs into account.…”

Section: Introductionmentioning

confidence: 99%

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Circulating Current Analysis and Suppression for Configured Three-Limb Inductors in Paralleled Three-Level T-Type Converters With Space-Vector Modulation

Yang

Chen

2017

IEEE Trans. Power Electron.

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In high-power applications, paralleling three-level T-type converters (3LT 2 Cs) with common ac and dc sides represents a modular solution for overcoming limitations of active switches. However, when independent space-vector pulse-width modulation (SVPWM) is employed, zero-sequence circulating currents (ZSCCs) will emerge. Especially, the use of three-phase three-limb inductors (3P3LIs) without additional passive components to reduce cost and improve density of overall parallel system, will worsen ZSCC problem. In this paper, detailed analysis of ZSCCs generated by SVPWM based on a derived average model taking into account magnetic circuit characteristics of 3P3LIs is proposed. Furthermore, four interrelated methods are sequentially proposed: 1) synchronizing sector numbers based on modified vector diagram partition for eliminating periodical ZSCC jumps caused by asynchronous change of starting small vector, 2) feeding forward grid voltages for eliminating starting current jumps due to computation delay, 3) connecting neural points to eliminating constant DC ZSCC caused by neural-point voltage deviation, 4) adjusting relative duration of negative and positive small vectors in pairs to suppress remaining low-frequency ZSCCs. Consequently, 3LT 2 Cs operated in parallel can separately regulate output powers with a good circulating current suppression performance. The validity of theoretical analysis and proposed methods is verified by experiment with three-parallel 175kw 3LT 2 Cs. Index Terms-Three-Level T-Type Converters (3LT 2 Cs), Zero-Sequence Circulating Currents (ZSCCs), Three-PhaseThree-Limb Inductors (3P3LIs), Space-Vector Pulse-Width Modulation (SVPWM), Parallel.

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Section: Analysis Of the Characteristics Of Svpwm For Zsccsmentioning

confidence: 99%

Section: Suppression Of the Remaining Low-frequency Zsccsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Circulating Current Analysis and Suppression for Configured Three-Limb Inductors in Paralleled Three-Level T-Type Converters With Space-Vector Modulation

Yang

Chen

2017

IEEE Trans. Power Electron.

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“…Improved modulation techniques are commonly-used active methods [28]. The voltage zero vector of space-vector-pulse-width modulation (SVPWM) is used in each paralleled module to suppress the circulating current [29,30]. However, the control performance deteriorates when the system parameters are different in each converter module.…”

Section: Introductionmentioning

confidence: 99%

Adaptive Backstepping Control with Online Parameter Estimator for a Plug-and-Play Parallel Converter System in a Power Switcher

Guo

Zhang

et al. 2018

Energies

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This study aims to address the inherent uncertainty in plug loads and load extraction, distributed generation, and the inevitable circulating current in a parallel structure. Therefore, in this paper, an adaptive backstepping control scheme with an online parameter estimator (OPE) for a plug-and-play parallel converter system in a four-port power switcher is proposed. The adaptive backstepping control method was designed in the dq0 coordinate system to suppress the circulating current in the zero-component; the circulating current can be suppressed by using an embedded algorithm and omitting the extra controller. An adaptive update law was designed to weaken the influence of the arbitrary plug and extraction operations in the DC and AC buses to realize the plug-and-play function. The transient tracking performance is governed by the limitation of maximum total errors in the voltage and current. As a result, the settling times of the voltage, current, and power decreased. Additionally, to further improve the system robustness, an online inductance and resistance estimator was established using an optimal algorithm that solves the weighted least squares problem. In the estimator, there are no additional voltage and current sensors needed, and the mean squared error (MSE) of the estimation can be minimized. Simulation studies on a two-converter parallel system with a plug-and-play function were conducted using MATLAB/SIMULINK (R2018b, MathWorks, Natick, MA, USA) to verify the effectiveness of the proposed adaptive backstepping control strategy. The results show that this strategy improves system performance over that of a system with unbalanced parameters among a parallel structure with AC and DC system disturbances caused by arbitrary plug and extraction operations.

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“…Moreover, the circulating fundamental and harmonic current, which are caused by the power back-feeding and line impedance mismatching, are harmful to the stable operation of the UPS system, as these circulating currents lead to the increased power losses and even overloading one of the UPS units. The circulating current issue has been investigated by some previous works [24][25][26][27][28]; [24,28] proposed the circulating suppression methods to deal with zero sequence current in the common DC-bus inverter system. The PWM switching strategies were investigated by [25][26][27] to solve the circulating current caused by the common mode voltage.…”

mentioning

confidence: 99%

DC-Link Protection and Control in Modular Uninterruptible Power Supply

Savaghebi

Guan

et al. 2018

IEEE Trans. Ind. Electron.

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In this paper, a DC-link voltage protection (DCVP) control method is proposed to address the DC-link overvoltage issue due to power back-feeding in parallel Uninterruptible Power Supply (UPS) system. The proposed control method is able to protect the inverter against the excessive DC-link voltage, which increases the system reliability and robustness. Moreover, a current sharing control strategy is proposed by online regulating the virtual resistance of each UPS module. The proposed current sharing control strategy is able to address the circulating fundamental and harmonic current caused by the line impedance mismatching or power back-feeding issue in the UPS system. In addition, an improved consensus-based distributed controller is proposed to alleviate the overshoot issue during the transient process in voltage amplitude and frequency restoration. Finally, the feasibility of the proposed methods are verified by experimental results from the parallel UPS prototypes. Index Terms-Uninterruptible Power Supply(UPS), DC link voltage protection, current sharing, consensus control, Anti-windup. I. INTRODUCTION RIVEN by the increasing importance of the Uninterruptible Power Supply (UPS) in the industry including enterprise IT, commercial telecom, data center and cloud computing area [1], the global market for the UPS system is projected to soar dramatically in the next few years. Meanwhile, the strong need for the UPS system to provide more reliable, efficient and secure electrical power supply for the modern digital equipment propels the UPS technology advancement by engineers and academic researchers [2]. According to the European Standard EN 62040-3 [3], the UPS systems are divided into on-line, off-line and lineinteractive UPSs. In an on-line UPS system, the load is always powered by the inverter regardless of the grid condition; the only exception is that when the overloading occurs and the bypass switch closes to connect the load with the grid. In offline and line-interactive UPS systems, however, the load power is supplied from the grid or a combination of the inverter and the grid, respectively [4]. The on-line UPS system is the most

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Bandwidth Expansion Method for Circulating Current Control in Parallel Three-phase PWM Converter Connection System

Cited by 95 publications

References 25 publications

Circulating Current Analysis and Suppression for Configured Three-Limb Inductors in Paralleled Three-Level T-Type Converters With Space-Vector Modulation

Circulating Current Analysis and Suppression for Configured Three-Limb Inductors in Paralleled Three-Level T-Type Converters With Space-Vector Modulation

Adaptive Backstepping Control with Online Parameter Estimator for a Plug-and-Play Parallel Converter System in a Power Switcher

DC-Link Protection and Control in Modular Uninterruptible Power Supply

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