Voltage Balancing Research Articles

A cooperative control strategy for balancing SoC and power sharing in multiple energy storage unit within DC microgrids

AbstractThis paper proposes a distributed cooperative control scheme for multiple energy storage unit (ESU) in DC microgrids to achieve the control objectives of SoC balancing, power sharing, and bus voltage recovery. In the primary control part, the proposed scheme constructs a control function between the SoC values of each ESU and the droop coefficients to dynamically adjust the droop coefficients. Through a communication network, information is exchanged with neighbouring ESUs to achieve SoC convergence. In the secondary control part, by exchanging power information with neighbouring ESUs, precise power distribution is achieved. Additionally, the proposed scheme maintains bus voltage stability. Finally, a DC microgrid simulation model and experimental platform were developed, demonstrating the feasibility and plug‐and‐play capability of the proposed control strategy through both simulation and experimental case tests.

A Modulation Method With Current Zero-Crossing Distortion Elimination and Voltage Balance Control for the RSHMC Converter

A Modulation Method With Current Zero-Crossing Distortion Elimination and Voltage Balance Control for the RSHMC Converter

Design and analysis of two-stage bidirectional power converter for vehicle-to-grid technology with fuel cell-battery electric vehicle

This paper presents the design and analysis of an isolated bidirectional two-stage power converter for vehicle-to-grid (V2G) technology with a fuel cell (FC) battery electric vehicle (FCBEV). In the first stage, the primary side employs a quadratic boost converter to achieve higher voltage levels, while the secondary side uses a voltage balancer circuit to equalize the DC subgrid terminal voltages. In the second stage, a T-type inverter is used for grid connection, effectively minimizing total harmonic distortion (THD). An Artificial Neural Network (ANN)-based maximum power point tracking technique combined with a Genetic Algorithm (GA) has been used to extract the maximum energy from the FC under changing temperature and pressure conditions in the system. The performance of the proposed converter has been evaluated and validated through simulation studies using MATLAB/Simulink software. The results demonstrate that the performance of the proposed converter is satisfactory under varying operating conditions. The grid current THD is maintained below 2.35 % in accordance with IEEE 519 standards. The proposed converter and control strategy facilitate the integration of EVs with renewable energy sources and bipolar hybrid AC/DC microgrids.

Model Predictive Control for Three-Phase, Four-Leg Dynamic Voltage Restorer

Dynamic voltage restores (DVRs) are usually used to mitigate the effect of voltage sag and guarantee sufficient power supply for sensitive loads. However, three-phase voltage cannot be compensated to the desired balance voltage under unbalanced three-phase loads by traditional DVRs with a three-phase, three-leg inverter. To address this problem, a three-phase, four-leg inverter-based DVR is first introduced in this paper, and then the state space model in its continuous form and discrete form are established, respectively. A two-step predictive method is proposed for the prediction of the output voltage in each switching state by the established voltage prediction model. Finite-control-set model predictive control (MPC) is developed to be used in the three-phase, four-leg inverter-based DVR. Its dynamic response is effectively improved by the proposed MPC method under various voltage sag conditions. The proposed DVR control strategy is validated via MATLAB/Simulink-R2022b simulations, which demonstrate its effectiveness in voltage compensation under various sag conditions.

A fuzzy-predictive current control with real-time hardware for PEM fuel cell systems

This research study presents the application of the FC-PCC (Fuzzy Logic Predictive Current Control) algorithm in the context of maximum power point tracking (MPPT) for a proton exchange membrane fuel cell system employing a three-level boost converter (TLBC). The proposed approach involves the integration of an intelligent fuzzy controller with a predictive current control strategy in order to improve the performance of MPP tracking. Initially, the utilization of fuzzy logic involves the utilization of data values obtained from the PEMFC. The maximum point (P-I) of the PEMFC polarization curve is determined, followed by the selection of the reference current. A predictive current control technique employs the reference current to ensure the voltage balance of the output capacitor in the three-level converter. The hardware-in-the-loop system utilizes a real-time and high-speed simulator, specifically the PLECS RT Box 1, to obtain the findings. The computational cost of the overall system is rather low, making it feasible to construct using PLECS RT Box 1. The new MPPT algorithm quickly finds the maximum power point (MPP) and balances the voltage of capacitors in a number of different proton exchange membrane fuel cells. The suggested MPPT technique has been verified to demonstrate rapid tracking of the maximum power point (MPP) location, as well as precise balancing of capacitor voltage and robustness to environmental variations. This approach was tested and found to outperform conventional MPPT methods like Perturb and Observe (P&O) and Incremental Conductance (IC) in terms of tracking duration, precision, and voltage balancing, achieving a 15% reduction in tracking duration, a 5% deviation from the MPP value for voltage, and superior stability under changing temperature and pressure.

Performance evaluation of a low-voltage SVC utilizing IoT streamed data for distribution systems

This paper presents the design, implementation, and performance evaluation of a novel 50 kvar Static Var Compensator (SVC) integrated with an Internet of Things (IoT) controller for a low-voltage power distribution system in Moscow. This integration enhances real-time monitoring and control capabilities over traditional SVC systems. The study focuses on advanced control systems for reactive power compensation, voltage stabilization, and overall system efficiency. Data collected over two months demonstrate the SVC’s effectiveness in maintaining a stable power factor close to unity and reducing reactive power demand. The device successfully kept voltage levels within acceptable limits across all phases, reducing fluctuations and ensuring balanced voltage levels. Key findings include enhanced reactive power compensation, voltage stabilization (minimum voltage not less than 218 V), improved system efficiency (reactive power demand from the source near zero most of the time), and significant improvements in power quality and grid stability. The case study at Kosinskaya Street, Moscow, confirms the device’s role in improving power quality and grid stability. These results support the broader deployment of IoT-integrated SVC technology in low-voltage power distribution systems.

Model predictive power control for grid-tied T-type three-level quasi-Z-source inverter with low complexity

Abstract The appealing design known as T-type three-level quasi-Z-source inverters (T2LQZSI) can function in both step-down and step-up modes. Model predictive control for converters has also received a lot of interest. This article suggests a low-complexity model predictive power control for T-type quasi-Z-source inverters with neutral-point voltage (NP-V) balance to address the shortcomings of conventional model predictive control and achieve improved performance. The resulting voltage is produced by using a variety of vectors. For NP-V balance, the tiny vector is employed. In addition, a strong optimum sector selection approach is suggested, which significantly lowers the processing complexity. Results from experiments show how effective and better the suggested technique is.

Analysis of Parameter Tolerance and Voltage Balance of Medium-Voltage Transformerless Multilevel Inductive Power Transfer System with Excitation Coils

Analysis of Parameter Tolerance and Voltage Balance of Medium-Voltage Transformerless Multilevel Inductive Power Transfer System with Excitation Coils

A Hybrid Multiobjective Control Strategy Based on Combination of Modulated Model Predictive Control and Phase‐Shifted Modulation for a Unidirectional Five‐Level Rectifier

ABSTRACTThe unidirectional multilevel rectifier has immense potential in high‐power medium‐voltage industrial applications. This paper proposes a multiobjective control method based on the combination of optimal‐vector‐pair modulated model predictive control (OVP‐M2PC) and a phase‐shifted modulation strategy for a unidirectional five‐level rectifier. This strategy takes both of the inductor current tracking and capacitor voltage balancing as the control objectives. First, an optimal vector pair is determined based on the AC‐side current variation rate, and then, through combining the calculated action duration of OVP with carrier phase‐shifted modulation, inductor current tracking is achieved. Second, capacitor voltage balancing control is carried out by compensating for the duty cycles which also decouples the input current tracking and output capacitor voltage balance control. Compared with traditional FCS‐MPC, under the proposed control strategy, complex cost function calculation and weighting factor tuning are not required, which much reduced computational burden. Multiobjective control is achieved with better performance in both steady‐state and dynamic conditions. The superiority of the proposed strategy over traditional FCS‐MPC are validated through simulations and hardware experiments.

A voltage-balancing algorithm based on the gating signal rotation and Separated Circulating Current Controller applied on a Modular Multilevel Converter

The Modular Multilevel Converter (MMC) is being used for many medium/high-power energy conversion applications due to its superior advantages such as modularity, scalability, and low harmonic generation. However, the MMC control can be challenging. If the submodule (SM) capacitors are not properly balanced, a circulating current is induced due to the voltage mismatch between the capacitor submodules. This circulating current adds to the arm current, which increases its RMS and peak value, and thus increases system losses. Therefore, controlling the submodule capacitor voltage and the circulating current is an important step in any MMC control. In this paper, a Gating Pattern Rotation algorithm is used for SM capacitor voltage balancing, and an independent circulating current controller in the double reference frame is used to eliminate the circulating current. Furthermore, a voltage-oriented control is employed to eliminate harmonics and regulate the grid power factor. MATLAB Simulink simulates the control technique, and various simulation results are presented. With results showing their effectiveness in managing and improving MMC behavior.

Experimental investigation on the design of a three-phase power factor corrector utilizing a SEPIC converter

A new configuration for a three-phase electric vehicle (EV) charger based on the Single-Ended Primary Inductor Converter (SEPIC) topology. The proposed charger operates as a power factor correction (PFC) converter, offering both step-up (boost) and step-down (buck) functions, enabling efficient adaptation to different input voltage levels while ensuring a stable DC output. By incorporating closed-loop current control and fast-switching regulation, the system attains unity power factor, which helps to reduce power losses and improve overall power quality. A unique control technique is proposed to regulate input current under unbalanced voltage conditions, ensuring reliable operation and high efficiency even during grid fluctuations. Simulations using MATLAB/Simulink demonstrate that, in unbalanced voltage scenarios, the control method maintain stable input current shaping, highlighting the system’s resilience. The results validate the SEPIC-based EV charger’s ability to consistently deliver efficient charging performance in both balanced and unbalanced voltage conditions, while achieving unity power factor and stable voltage regulation.

Distributed Secondary Control of DC Microgrid with Power Management Based on Time-of-Use Pricing and Internal Price Rate

This paper presents a novel approach to manage distributed DC microgrids (DCMG) by integrating a time-of-use (ToU) electricity pricing scheme and an internal price rate calculation mechanism. The proposed power-management system is designed to effectively handle uncertainties such as utility grid (UG) availability, fluctuating electricity prices, battery state of charge (SOC) levels, and frequent plug-ins and plug-outs of electric vehicles (EVs). Uncertainties in DCMG systems often lead to inefficiencies, power imbalances, and inexact voltage regulation issues within DCMGs. In addition, to maintain the power balance and constant voltage regulation under various operational states, the proposed scheme also incorporates secondary control into the DCMG power-management system. Unlike the existing approaches that often fail to adapt dynamically to changing conditions, the proposed method is the first approach to consider the concept of internal price rate in designing the DCMG power management. To address this challenge, this approach proposes a more resilient power-management strategy to enhance the efficiency and adaptability of DCMG systems. Extensive simulations and experimental validations demonstrate the practicality and adaptability of the proposed control strategy under diverse test conditions, including operation transitions between grid-connected mode (GCM) and islanded mode (IM), low battery SOC condition, operation transition from the current control mode (CCM) to distributed secondary control mode (DSCM), and EV plug-in scenarios. The test results confirm that the proposed method enhances the reliability, efficiency, and economic viability of DCMG systems, making it a promising solution for future smart grid and renewable energy integrations.

A Novel Family of Single‐Phase Direct Buck AC‐AC Converters With Continuous Input Current, Reduced Components, and Balanced Power Losses

ABSTRACTThis paper introduces a single‐phase step‐down AC‐AC converter designed for voltage sag/swell compensation applications. The converter features a minimal component count, continuous input current, and high efficiency, although only one power switch operates at a high frequency per input voltage half‐cycle. It offers a linear and broad voltage conversion ratio (D) without right‐half‐plane zeros in its small‐signal transfer function, simplifying the controller design. The proposed converter does not need dead time. It ensures balanced voltage and current stresses and power losses among power switches, easing the selection of semiconductors. Compared with existing topologies, it excels in total capacitor voltage, switching device power, and volume metrics of capacitors and inductors, thereby reducing cost and size. Experimental results from a 250‐W prototype demonstrate a peak efficiency of 94.8% and effective voltage sag/swell mitigation as a DVR.

A Modified Carrier-Based PWM Strategy for Common Mode Voltage Elimination and Neutral Point Voltage Balance in a Unidirectional Three-Level Converter for AC Motor Drives

A Modified Carrier-Based PWM Strategy for Common Mode Voltage Elimination and Neutral Point Voltage Balance in a Unidirectional Three-Level Converter for AC Motor Drives

Coupled-Inductor-Based Buck-Type Converter With Autonomous Voltage Balancing for Bipolar DC Microgrid

Coupled-Inductor-Based Buck-Type Converter With Autonomous Voltage Balancing for Bipolar DC Microgrid

A novel and easy‐to‐implement modulation scheme for reducing modulation complexity in modular multilevel converter

AbstractModulation strategy plays a key role in the operation of modular multilevel converters (MMC). Although many studies have been carried out on its optimization in MMC, the limitations of hardware implementation are seldom considered. This paper presents a novel and easy‐to‐implement modulation strategy that simplifies both hardware design and application. From the analysis in this paper, the widely‐used modulation methods have the problems of pulse width modulation (PWM) signal feedback and complex carrier configuration in hardware implementation. By setting up a flexible insertion and removal submodule and proposing a capacitor voltage balance algorithm based on duty ratio allocation, the proposed modulation method can allow for the separate design of the Algorithm Unit and the PWM Unit in the hardware, which solves the problem of PWM feedback and reduces the hardware requirement of the trigger system. Moreover, the proposed method can broaden the selection range of processor chips. Finally, a downscaled MMC prototype is built; the proposed method is verified by both simulation and experiment.

Parallel connected triple-active-bridge converters with current and voltage balancing coupled inductor for bipolar DC distribution

Parallel connected triple-active-bridge converters with current and voltage balancing coupled inductor for bipolar DC distribution

Power and efficiency enhancement of solar photovoltaic power plants through grouped string voltage balancing approach

Solar photovoltaic (PV) power plants’ performance is severely impacted by multi-level irradiances or partial shading, leading to power losses and voltage instability. Also, partial shading adds further complexity to the maximum power point tracking algorithms by introducing numerous peaks in the power curves, resulting in additional losses. Numerous solutions are presented to deal with shading losses, and dynamic reconfiguration is the most effective; however, higher switch count and complex architecture make it impractical in real-world implementation. Hence, this study proposes a low-complexity architecture based on the grouped string voltage balancing approach. This approach utilizes a voltage balancing converter connected to groups of strings to enhance the power output of the array of PV plants, maintain overall system voltage stability, and eliminate the possibility of multiple peaks formation in the power curves. The effectiveness of the proposed approach is tested under numerous static and dynamic partial shadings and analyzed using power curves, power output, losses, efficiencies, and voltage stability. The validation is done by comparing the proposed approach with conventional and advanced architectures for a 32.5 kW system. The results show that the proposed method requires a 50 % reduced switch count than existing techniques, achieves 99.54 % efficiency, and maintains an average voltage stability of 0.01.

A Novel Modular Multilevel Converter Topology with High- and Low-Frequency Modules and Its Modulation Strategy

To resolve the issue of the difficultly in effectively balancing the output performance improvement, cost reduction, and efficiency improvement of a medium-voltage modular multilevel converter (MMC), a novel MMC (NMMC) topology based on high- and low-frequency hybrid modulation is proposed in this study. Each arm of the NMMC contains a high-frequency sub-module composed of a heterogeneous cross-connect module (HCCM) and N − 1 low-frequency sub-modules composed of half-bridge converters. The high-frequency bridge arm of the HCCM in this study adopts SiC MOSFET devices, while the commutation bridge arm and low-frequency sub-module of the HCCM adopt Si IGBT devices. For the NMMC topology, this study adopts a high/low-frequency hybrid modulation strategy, which gives full play to the advantages of low switching loss in SiC MOSFET devices and low on-state loss in Si IGBT devices. In addition, a specific capacitor voltage balance strategy is proposed for the HCCM, and the working state of the HCCM is analyzed in detail. Furthermore, the feasibility and effectiveness of the proposed topology, modulation strategy, and voltage balancing strategy are verified by experiments. Finally, the proposed topology is compared with the existing MMC topology in terms of device cost and operating loss, which proves that the proposed topology can better balance the cost and efficiency indicators of the device.

Hybrid feedback control of PMSG-based WECS with multilevel flying-capacitor inverter enhanced by fractional order extremum seeking

This paper proposes an original hybrid control strategy for a three-phase multilevel flying capacitor inverter (FCI) used in wind energy conversion system (WECS). A state feedback law, computed using a Lyapunov function and an invariance principle, is designed to manage grid current control and capacitor voltage balancing, guaranteeing the asymptotic stability of the closed-loop system. Additionally, a fractional-order extremum seeking control (FOESC) algorithm for Maximum Power Point Tracking (MPPT) is introduced, which optimizes power capture by adjusting turbine speed from the DC side without requiring a detailed system model (model-free approach). The use of fractional-order calculus leads to improved convergence and more seamless performance while preserving the robust characteristics of the system. The proposed control strategies are validated through simulation, demonstrating improved transient response and stability under varying wind conditions and parameter uncertainties. These results highlight the potential of advanced control algorithms to enhance the efficiency and reliability of wind energy systems, contributing to global efforts to achieve sustainable energy goals.