Voltage Balancing Method Research Articles

A Passive Voltage-Balancing Method for Series-Connected SiC MOSFETs in Pulse Generator Based on Snubber Circuit

A Passive Voltage-Balancing Method for Series-Connected SiC MOSFETs in Pulse Generator Based on Snubber Circuit

Correction: Kim et al. Zero-Sequence Voltage Injection Method for DC Capacitor Voltage Balancing of Wye-Connected CHB Converter under Unbalanced Grid and Load Conditions. Energies 2021, 14, 1019

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Coordinated Capacitor Voltage Balancing Method for Cascaded H-Bridge Inverter with Supercapacitor and DC-DC Stage

Coordinated Capacitor Voltage Balancing Method for Cascaded H-Bridge Inverter with Supercapacitor and DC-DC Stage

Notice of Violation of IEEE Publication Principles: Washout Filter-Based Distributed Resilient Current Control for Cyber-Physical Microgrids

Notice of Violation of IEEE Publication Principles: <br><br>“Washout Filter-Based Distributed Resilient Current Control for Cyber-Physical Microgrids," <br>by X. Lu and J. Lai, <br> in IEEE Systems Journal, Early Access <br><br>After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. <br><br>This paper contains significant portions of original text from the paper cited below. The original text was copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission. <br><br>"A Combined Distributed Cooperative Method and Washout Filter-Based Method for Power Sharing and Voltage Balancing in Bipolar DC Microgrids" <br> by Ramin Babazadeh-Dizaji, Mohsen Hamzeh, Nima Mahdian Dehkordi, <br>submitted to IEEE Transactions on Energy Conversion, August 2020. <br><br> <br/> This article proposes a washout filter-based distributed resilient current control scheme that can achieve current sharing of distributed generations (DG) and voltage restoration of dc bus almost surely under communication channel noise interferences. Since the cyber channels are exposed to inherent noise interferences, the stability and reliability of cyber-physical dc microgrids may terribly be reduced. To dispel the adverse influences of noise interferences, a novel discrete time washout filter is developed. Accordingly, a discrete-time-distributed noise-resiliency control algorithm is developed for dc microgrids based on washout filters, in which only the current state variable is allowed to exchange among DGs with the local decentralized voltage controller. This makes the proposed control mode different from the conventional parallel mode usually requiring a leader–follower consensus-based voltage control by exchanging two state variables (i.e., terminal voltage and current output). Thus, the proposed control mode decreases the complexity to the formulation and enhances the robustness to the leader communication failure. By introducing stochastic theory and Lyapunov stability function, the sufficient conditions considering noise interferences is derived to ensure the stability operation of the whole closed-loop dc network. The obtained results show the effectiveness of the proposed strategy by a tested dc microgrid in OPAL-RT real-time simulator.

A Novel Sensorless Capacitor Voltage Balancing Method for the Modular Multilevel DC Transformer with Diode-Clamped Circuits

A Novel Sensorless Capacitor Voltage Balancing Method for the Modular Multilevel DC Transformer with Diode-Clamped Circuits

Modulation Methods for Balancing the Capacitor Voltages of N-Level Diode-Clamped Converters

Diode-clamped converters (DCCs) suffer from the inherent capacitor voltage imbalance problem. Most software-based voltage-balancing methods fall into the space-vector-modulation (SVM) category and the carrier-based pulse-width-modulation (CB-PWM) category. Despite their effectiveness for the three-level DCCs, it is not easy to extend them to a general <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level topology. In this paper, a new modulation method of a category called good-switching (GS) PWM is proposed for balancing the capacitor voltages. The proposed method requires no parameter-tuning effort and is extremely simple to design even for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level topology regardless of the number of phases. It is also potentially applicable to other multilevel converters. The principle, the implementation, and the stability analysis of GS-PWM are elaborated for a generic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level DCC. A modified GS-PWM scheme and an on-off control scheme are proposed to reduce the switching transitions for further realizing the advantages of the GS-PWM. Particularly, the on-off control can be extended to many other voltage-balancing methods. Simulation and experiments with a five-level DCC validate the proposed methods.

A Look-up Table Based Method for Voltage Balancing of Neutral-Point in Five-level ANPC Converter

A Look-up Table Based Method for Voltage Balancing of Neutral-Point in Five-level ANPC Converter

Active RCD adaptive voltage balancing control strategy for high-voltage uncontrolled rectifier valve

The voltage balance of the series diodes is the premise to ensure the stable and reliable operation of the high voltage uncontrolled rectifier valve. When traditional RC and RCD voltage balancing methods are applied to high voltage uncontrolled rectifier valves in far-reaching offshore wind farms, the complex and changeable operating environment poses a challenge to the anti-interference of the balance effect of the snubber circuit. In this paper, an active RCD adaptive voltage balancing control strategy with strong anti-interference ability is proposed based on the establishment of the active RCD voltage balancing model of the high voltage uncontrolled rectifier valve. The parameter tuning method of the active RCD snubber circuit is given, and the auto-PID control strategy of the active RCD snubber circuit is proposed according to its nonlinear time-varying characteristics. The simulation example verifies that the active RCD adaptive voltage balancing strategy of the high voltage uncontrolled rectifier valve has strong anti-interference performance, which provides a reference for the design of the high voltage uncontrolled rectifier valve voltage sharing system in the far-reaching offshore wind farm.

DC-port voltage balance strategy for three-phase cascaded H-bridge rectifier based on logic combination modulation

PurposeThe purpose of this paper is to propose a DC-port voltage balance strategy realizing it by logic combination modulation (LCM). This voltage balance strategy is brief and high efficient, which can be used in many power electronic devices adopting the cascaded H-bridge rectifier (CHBR) such as power electronic transformer (PET).Design/methodology/approachThe CHBR is typically as a core component in the power electronic devices to implement the voltage or current conversion. The modulation method presented here is aiming to solve the voltage imbalance problem occurred in the CHBR with more stable work station and higher reliability in ordinary operating conditions. In particular, by changing the switch states smoothly and quickly, the DC-port voltage can be controlled as the ideal value even one of the modules in CHBR is facing the load-removed problem.FindingsBy using the voltage balance strategy of LCM, the problem of voltage imbalance occurring in three-phase cascaded rectifiers has been solved properly. With the lower modulation depth, the efficiency of the strategy is shown to be better and stronger. The strategy can work reliably and quickly no matter facing the problem as load-removed change or the ordinary operating conditions.Research limitations/implicationsThe limitation of the proposed DC-port voltage balance strategy is calculated and proved, in a three-module CHBR, the LCM could balance the DC-port voltage while one module facing the load-removed situation under 0.83 modulation depth.Originality/valueThis paper provides a useful and particular voltage balance strategy which can be used in the topology of three-phase cascaded rectifier. The value of the strategy is that a brief and reliable voltage balance method in the power electronic devices can be achieved. What is more, facing the problem, such as load-removed, in outport, the strategy can response quickly with no switch jump and switch frequency rising.

Review Article: Voltage Balancing Method for Battery and Supercapacitor as Energy Storage

This paper examines several existing voltage equalizers techniques for energy storage system, with a focusing on batteries and supercapacitors. Due satisfy the demands, energy storage cells are often coupled in series/parallel. However, divergence of voltage distributed among cells produces the problems of voltage imbalance that affecting the ageing of energy storage system and solved through equalizers. Several assessments from features of topologies in voltage balancing circuit supplied primarily based total on a few attentions’ just like the effectiveness in balance and components. Voltage balancing is essentially separated into two categories: passive and active equalizers. Therefore, this paper studied and reviewed several topologies from both equalizer types with the sample result to verify the topology performance.

A Three-Phase Dual-Output T-Type Three-Level Converter

A novel three-phase dual-output T-type three-level converter (DO-T-TLC) topology is proposed in this article. The proposed topology has the dc-link and two sets of three-phase ac voltage output terminals. The topology of DO-T-TLC is introduced. Then, the operating principle of multiplexing switches and the available switching states of converter are analyzed, including current path, output phase voltage level, and blocking voltage of different switching states. The phase disposition pulsewidth modulation scheme with dc offsets is discussed in detail, and the key problems of the modulation scheme under both the common frequency and different frequency operation modes, such as voltage level selection, displacement angle constraint, and modulation index range, are studied. For the imbalance of two series capacitors in the dc-link, the mechanism is first revealed, and then a dc-link capacitor voltage balance method to control the average neutral point current is proposed. When DO-T-TLC is used in different operation modes, the ability and effect of this method to balance capacitor voltages are summarized. A low-power three-phase prototype is built, and the experimental results are given to verify the feasibility of the proposed topology and the effectiveness of the modulation scheme to control the voltage balance.

A Model-Free Capacitor Voltage Balancing Method for Multilevel DAB Converters

Capacitor voltage balancing is of importance in the neutral-point-clamped based dual-active-bridge converters. Most of traditional voltage balancing methods adopt the transformer current models in the balancing process, as the direction of the neutral-point current is affected by the transformer current polarity. However, this approach requires heavy and repetitive offline precalculation for the transformer current polarity under various operating modes, and thus, leading to complicated implementation. To overcome this, a model-free voltage balancing scheme based on a fixed-switching-state method is proposed in this letter. Two switching states are employed during the voltage balancing process in the proposed method, where the direction of the neutral-point current is independent on the transformer current polarity. Hence, the implementation can be simplified without the precalculation of transformer current polarity. Furthermore, the model-free feature of the proposed method is more robust against parameter variations or operating mode changes. Experimental tests are performed, which verify that the proposed method can achieve voltage balancing in terms of easy implementation and fast dynamics.

Capacitor Voltage Balancing Control for a Novel 5-Level Dual Active Bridge Converter

Multilevel technology is an attractive solution to increase the cost effectiveness and power density of dc solid state transformers. In this article, a novel five-level (5L) dual active bridge (DAB) converter topology is proposed. By stacking two neutral-point-clamped (NPC) converters at the primary side, the proposed topology could quadruple the input dc-bus voltage of a conventional two-level (2L) DAB converter. Besides, by analyzing the working principle of the 5L-DAB converter, a voltage balancing control method is carried out. With the aid of the voltage balancing method, voltages of the four series-connected dc-bus capacitors in the 5L-DAB converter can be actively balanced, guaranteeing safe operation voltage for all the semiconductor switches. After that, the operation range of the proposed voltage balancing method is derived by theoretical analysis. Finally, the performance of the proposed converter topology and voltage balancing method have been verified by experimental results.

Active Gate Driver With Turn-off Delay Control for Voltage Balancing of Series–Connected SiC MOSFETs

Connecting semiconductor switches in series is a way to increase the voltage rating of a power electronic converter. However, if two switches are directly connected without any special effort, an uneven voltage between the switches can occur due to nonidentical characteristics of them. A significant voltage imbalance may destroy the switches, and both thermal and loss imbalance also lead to the unstable system. Since a silicon carbide (SiC) metal–oxide–semiconductor field–effect transistor ( <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> ) has a faster switching speed and higher voltage blocking capability than silicon (Si) devices, existing voltage balancing methods for Si devices may not be suitable. This article proposes a voltage balancing method that controls turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> delay time of the switch by adding one bipolar junction transistor (BJT) on a gate turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> path. Depending on the base voltage of the BJT, turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> resistance and delay time are actively changed which mitigates the imbalance problem. The theoretical analysis of the proposed method has been discussed in detail based on the classical <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> model. Both the simulations and experiments have been performed to verify the theory and the validity of the proposed method where the voltage imbalance is reduced from 22.4% to 3.2% as well as reducing the switching loss at the entire voltage and load conditions.

Capacitor voltages balancing method for buck modular DC/DC converter

The most critical problem of the modular DC-DC converter (MDCC) is the voltage balancing of the submodule (SM) capacitors, the MDCC with stepped 2-level modulation has been developed and presents a good solution, however, this type of modulation has many restrictions when there is a wide range of capacitance tolerance of the SM capacitors that results inaccurate capacitor voltages balancing. To solve this problem, this paper discusses a proposed method of capacitor voltage balancing. Compared with stepped 2-level modulation, the voltage balancing method using modified duty cycle modulation offers the merits: i) reduction in output voltage and SM capacitor voltages overshoot during dynamic operation and improvement in the time response of the system and; ii) accurate voltage balancing over wide range of capacitance tolerance of each SM capacitor; and iii) the sorting algorithm replaced with modified duty cycle modulation method for the SM capacitor voltages balancing which reduces the computation burden. The proposed method ensures a stable voltage balancing, improves the time response of the system, and decreases the voltage and current overshoot during the dynamic response compared with prior art of MDCCs, where the stepped 2-level modulation is adopted. An analytical simulation of the MDCC is presented using MATLAB/Simulink to explain the operation.

A Robust Capacitor Voltage Balancing Method for CPS-PWM-Based Modular Multilevel Converters Accommodating Wide Power Range

Capacitor voltage balancing is one of the most important issues for the safe, reliable, and economical operation of the modular multilevel converter (MMC). This article proposes a modified individual capacitor voltage balancing method for MMCs with phase-shifted carrier pulsewidth modulation (PWM) (CPS-PWM) to solve the problem of the poor dynamic performance that the conventional individual voltage balancing methods suffer at low output power. In the proposed method, the information of arm current is incorporated into the balancing algorithm to cancel out the coupling effect of the output power on balancing control. Compared with conventional balancing methods, the proposed method shows better robustness against varying output power and maintains a good dynamic performance in a wider power range. The complete modeling process and parameter design are presented and considered for system stability. The effectiveness of the proposed method is verified with both MATLAB/Simulink simulation and experimental results.

Dynamic Voltage Regulation and Unbalance Compensation in a Low-Voltage Distribution Network Using Energy Storage System

Modern distribution grids may suffer problems of voltage distortion, especially along radial low-voltage feeders with a high penetration of intermittent, unbalanced and distorted loads and generation sources. It is a challenge to develop an effective voltage-regulation method using a straightforward implementation. This paper proposes a novel method for local voltage control and balancing using a shunt-connected energy storage system. The compensation principles are explained, and a complete controller design is proposed. The algorithm is designed to be implemented in power electronic converters that provide the interface between the storage and the grid. The original contribution is the development of a low-level control method, which includes voltage balancing and a method to minimize the compensator current and is to be implemented in power electronic converters that provide the interface between the storage and the grid. The calculation of active and reactive compensator currents is explained with relation to the estimated grid impedance. The efficacy of the designed controller is verified by laboratory experiments. It is shown that voltage regulation using the proposed method is achieved with less apparent power compared to a system where only reactive power is used. The controller presents a very good dynamic response to rapid voltage variations, such as unbalanced voltage dips. The applicability and constraints of the method are discussed with respect to the present state of the art in low-voltage-grid voltage regulation.

A Voltage Balancing Method for Series-Connected Power Devices Based on Active Clamping in Voltage Source Converters

This article proposes a voltage balancing technique for series-connected power devices in voltage source converters (VSCs). Each main power device has an active clamping module (ACM), consisting of a capacitor and an auxiliary switch. The ACM can clamp the main power device voltage, and voltage sharing among series-connected power devices can be realized by balancing the ACM capacitor voltages. The balancing circuit does not affect the normal operation of the devices and the introduced power losses can be ignored. The possible charging and discharging principles of the ACM capacitors are summarized. Then, the control strategy to balance the ACM capacitor voltages is introduced. The operating principles of a VSC with series-connected devices and the proposed balancing circuits are presented, including charging stage, discharging stage, and steady voltage stage. A switching sequence of auxiliary switch and main power switch is proposed to ensure ZVS- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> of the auxiliary switch. Besides, design considerations of key parameters are presented. Finally, experimental results are provided to verify the effectiveness and feasibility of the proposed method. The voltage imbalance degree of the six series-connected devices is less than 3% under different operating conditions. The proposed method shows good balancing performance, good scalability, and low power losses.

An Algebraic Modulation Strategy for 3L-NPC Converters With Inherent Neutral-Point Voltage Balance Capability

This letter proposes an algebraic modulation strategy for the three-level neutral-point-clamped converters. The duty-cycle-assignment problem is first transformed into the algebraic-solution problem. Then, according to the algebraic theory, the general solution of the modulation matrix is obtained. By properly designing the free parameters in the general modulation matrix, various neutral-point voltage (NPV) balancing methods can be constructed conveniently. In addition, the NPV balance is easily realized without additional control effort. Compared to the existing modulation strategies, the proposed strategy is simple and easy-to-implement. The feasibility of the proposed strategy is validated by laboratory experiments.

Analysis and Mitigation of DC Voltage Imbalance for Medium-Voltage Cascaded Three-Level Neutral-Point-Clamped Converters

The cascaded three-level neutral-point-clamped (3L-NPC) converter and the modular multi-level converter (MMC) are attractive solutions for medium-voltage direct-current (MVDC) applications. Due to their low cost compared to MMCs, cascaded 3L-NPC converters have been adopted in ANGLE-DCa 30 MVA MVDC link demonstration project in North Wales, UK. DC voltage imbalance across submodules (SMs) is a common challenge for both types of MVDC converters. Such imbalance is topology dependent and remains under-researched for cascaded 3L-NPC converters. In this paper, small-signal model-based analysis has been done to reveal that the dc voltage imbalance in cascaded 3L-NPC converters is caused by an unstable system pole. Two voltage balancing methods are presented. The first method is based on PI controllers to precisely regulate SMs voltages without influencing output power. However, it relies on communication between a central controller and local controllers within SMs. The second method uses inverse-droop based control to take over the dc voltage regulation upon loss of communication. Both balancing methods are experimentally validated using a 30 kVA testbed based on the ANGLE-DC project. It has been demonstrated that the dc voltages of SMs can be effectively balanced with both methods during changes of load conditions and dc bus voltages.