Instantaneous Current-Sharing Control Strategy for Parallel Operation of UPS Modules Using Virtual Impedance

Zhang, Yu; Yu, Mi; Liu, Fangrui; Kang, Yong

doi:10.1109/tpel.2012.2200108

Cited by 120 publications

(66 citation statements)

References 20 publications

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“…A bypass switch has been added in the system to increase the reliability of the system. In case of internal faults in the system or overloading and overheating of the circuit, the bypass switch turns ON and provides a direct path for the power from the utility grid to the connected load [15].…”

Section: Battery Modementioning

confidence: 99%

A High-Frequency Isolated Online Uninterruptible Power Supply (UPS) System with Small Battery Bank for Low Power Applications

et al. 2017

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Uninterruptible power supplies (UPSs) are widely used to deliver reliable and high quality power to critical loads under all grid conditions. This paper proposes a high-frequency isolated online UPS system for low power applications. The proposed UPS consists of a single-stage AC-DC converter, boost DC-DC converter, and an inverter. The single-stage AC-DC converter provides galvanic isolation, input power factor correction, and continuous conduction of both input and output current. The low battery bank voltage is stepped up to high dc-link voltage by employing a high voltage gain boost converter, thus allows the reduction of battery bank to only 24 V parallel connected batteries. Operating batteries in parallel improves the battery performance and resolves the issues related to conventional battery banks that arrange the batteries in series combination. The inverter provides regulated output voltage to the load. A new cascaded slide mode (SM) and proportional-resonant (PR) control for the inverter has been proposed, which regulates the output voltage for both linear and non-linear loads. The controller shows excellent performance during load transients and step changes. Besides, the controller for boost converter and AC-DC converter is presented. Operating principle and experimental results of 1 kVA laboratory setup have been presented for the validation of proposed system.

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Section: Battery Modementioning

confidence: 99%

A High-Frequency Isolated Online Uninterruptible Power Supply (UPS) System with Small Battery Bank for Low Power Applications

et al. 2017

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“…For inverters in UPSs, it is necessary to introduce various instantaneous control strategies, such as PID and multiple feedback controls, to adapt for diverse nonlinear loads [4,5]. Among various instantaneous control strategies, the PID control strategy has a simple form and high robustness and is thus analyzed in this paper.…”

Section: Transient Characteristics Of Three-phase Inverters Considerimentioning

confidence: 99%

“…Treating the transistors (see Figure 1), typically IGBTs, as ideal switches, when the DC bus voltage is constant and the switching frequency is high enough, the inverter bridges will amply low frequency modulation signals linearly and can be modeled as an amplifier with gain b K [4,5], given by…”

Section: Transient Characteristics Of Three-phase Inverters Considerimentioning

confidence: 99%

“…In addition, a pulse width modulation (PWM) inverter in a UPS must introduce various instantaneous feedback control strategies, such as PID, multiple feedback controls, etc. to adapt for diverse, unpredictable nonlinear loads [4,5]. However, in the design of instantaneous control strategies, the appropriate dynamic models become complex when magnetic coupling is considered.…”

Section: Introductionmentioning

confidence: 99%

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PID Controller Design for UPS Three-Phase Inverters Considering Magnetic Coupling

Zhang

Li²,

Kang

2014

Energies

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Abstract:In three-phase inverters used in uninterruptible power supplies (UPSs), three-limb inductors and three-limb transformers are commonly used in consideration of cost and size. However, magnetic coupling exists between the three phases of the inverter, which can result in complex models. When instantaneous feedback control strategies are introduced to achieve high quality output waveforms, the transient analysis of the closed-loop inverters becomes difficult. In this paper, the phenomenon of magnetic coupling in three-phase inverters due to three-limb inductors and three-limb transformers is analyzed. A decoupled dynamic model is derived based on the instantaneous symmetrical components transformation, which comprises three decoupled equivalent circuits of instantaneous symmetrical components. Analyses based on this model indicate that magnetic coupling may have a significant impact on the performance of three-phase inverters under unbalanced load conditions and transient responses. For three-phase inverters in UPSs with Proportional-Integral-Differential (PID) closed-loop control strategies, the interactive influence between instantaneous closed-loop regulation and magnetic coupling is researched. Finally, a method of reliability analysis and PID controller design for inverters with magnetic coupling is derived. Simulation and experiment results validate the model and conclusions. OPEN ACCESSEnergies 2014, 7 8037

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“…Therefore, improved droop control methods have been proposed in many works. In [10][11][12][13][14][15], "virtual impedances" are introduced to the current feedback loop of the control system. By configuring virtual impedances presenting resistive [11], inductive [12], and complex impedance [13,14] characteristics, the * Correspondence: hy 8615381@163.com inverter equivalent output impedance can be conveniently regulated to enhance the control accuracy and to improve power sharing among parallel inverters.…”

Section: Introductionmentioning

confidence: 99%

A current feedback control strategy for parallel-connected single-phase inverters using a third-order general-integrator crossover cancellation method

Huang¹,

Luo²

2016

Turk J Elec Eng & Comp Sci

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Virtual impedance is usually introduced to the control system of parallel inverters in order to change the inverter equivalent output impedance and to enhance control accuracy and power sharing. In this paper, a current feedback control strategy using a third-order general-integrator crossover-cancellation method that can be implemented in a virtual impedance loop is proposed. This method consists of 2 parts: a crossover-cancellation feedback network, which achieves the band-pass effect, and a multilevel TOGI-OSG link, which acts as a filter. Compared with the conventional virtual impedance method, the proposed method can avoid derivation of output current, reduce system calculating burden, and enhance dynamic response. Additionally, this method can reduce the THD of output voltage in the case of nonlinear load and can also drastically restrain the impact of DC component on output voltage. A prototype consisting of 2 sets of 2-kW photovoltaic inverters operating in parallel was built in the laboratory. Simulated and experimental results are examined to verify the effectiveness and feasibility of this method.

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Instantaneous Current-Sharing Control Strategy for Parallel Operation of UPS Modules Using Virtual Impedance

Cited by 120 publications

References 20 publications

A High-Frequency Isolated Online Uninterruptible Power Supply (UPS) System with Small Battery Bank for Low Power Applications

A High-Frequency Isolated Online Uninterruptible Power Supply (UPS) System with Small Battery Bank for Low Power Applications

PID Controller Design for UPS Three-Phase Inverters Considering Magnetic Coupling

A current feedback control strategy for parallel-connected single-phase inverters using a third-order general-integrator crossover cancellation method

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