Voltage Balancing Technique Research Articles

Comprehensive Investigation of Promising Techniques to Enhance the Voltage Sharing among SiC MOSFET Strings, Supported by Experimental and Simulation Validations

This paper comprehensively reviews several techniques that address the static and dynamic voltage balancing of series-connected MOSFETs. The effectiveness of these techniques was validated through simulations and experiments. Dynamic voltage-balancing techniques include gate signal delay adjustment methods, passive snubbers, passive clamping circuits, and hybrid solutions. Based on the experimental results, the advantages and disadvantages of each technique are investigated. Combining the gate-balancing core method with an RC snubber, which has proven both technically and commercially attractive, provides a robust solution. If the components are sorted and binned, voltage-balancing techniques may not be necessary, further enhancing the commercial viability of series-connected MOSFETs. An investigation of gate driver topologies yields one crucial conclusion: magnetically isolated gate drivers offer a simple and cost-effective solution for high-frequency (HF) applications (2.5–50 kHz) above 8 kV with an increased number of series devices. Below 8 kV, it is advantageous to move the isolation barrier from the gate drive IC to an optocoupler and isolated supply, allowing for a simple design with commercially available components.

Design of a linearized 4-H-bridge STATCOM for load balancing purposes

<span lang="EN-US">In this paper, a 4-H-bridge STATCOM (4-HB STATCOM) is introduced. Four H-bridges are cascaded to build the proposed STATCOM. Cascading the H-bridges makes it possible to operate the devised STATCOM on high voltage levels with less voltage harmonic association. The proposed STATCOM is equipped with an adaptive current controller and a voltage balancing technique for its DC capacitor voltages. The adopted controlling strategy makes the STATCOM respond continuously and linearly to current demand in both inductive and capacitive operational modes without noticeable association of harmonics. The DC capacitor of each H-bridge is shunted by a second harmonic filter to stabilize its voltage. The proposed STATCOM does not require initial charging of its DC capacitors because it is provided with a utilized technique for charging them rapidly by disabling the STATCOM carrier for a certain period sufficient to build up the required level of DC voltages. In this work, the proposed STATCOM is designed to operate on 11 kV AC voltage as a continuously and linearly controlled compensating susceptance. It can deservingly be employed in load balancing systems for achieving big amount of energy savings in power generation and big reduction in transmission losses.</span>

New Modular Multilevel DC–DC Converter Derived from Modified Buck–Boost DC–DC Converter

Raising the electrification ratio to 100% is still a formidable challenge in Indonesia, especially in the remote areas of the eastern part of the archipelago. A DC microgrid system is one of the most viable solutions to increase the electricity supply in remote areas, taking advantage of various renewable energy sources that are located near the rural load centers. A DC–DC power converter for a rural DC microgrid system needs to have a high voltage gain to facilitate the power conversion from low-voltage PV output to a high-voltage DC microgrid bus, a very low input ripple current to help maintain the PV or battery lifetime, and be highly modular for ease of transport and assembly. Many topologies have been proposed to obtain high voltage gain, very low ripple current, and modularity. However, they usually use either bulky and lossy magnetic components, are sensitive to component parameter variance and need special voltage-balancing techniques, or have different component ratings for their multilevel configuration which weakens the modularity aspect. This paper proposes a new modular multilevel DC–DC converter that is very suitable for rural DC microgrid applications based on a modified buck–boost topology. The proposed converter is easily stackable to achieve high voltage gain and does not require any voltage balancing techniques, thus enhancing the modularity characteristics and simplifying its control method. Moreover, the ripple current can be reduced by employing a multiphase configuration. This converter can also facilitate bidirectional power flow to serve as a battery charger/discharger. A comprehensive analysis of voltage gain and ripple current are presented to explain the inner workings of this converter. Finally, the performance of this converter is verified through simulation and experiment, showing the converter’s modularity, bidirectional power capability, and potential to achieve voltage gain and ripple-current requirements of the DC microgrid system.

Development and testing midpoint voltage balance algorithms of three-level inverters

Nowadays, the use of inverters is increasing in more and more applications. Environmental awareness is becoming a trend, so more and more people install solar energy systems on their houses, which also require the use of inverters. Higher power levels have led to the emergence of three-level inverters which has opened up new challenges, such as the issue of midpoint voltage balancing. This paper discusses voltage balancing and voltage ripple reduction techniques for three-level inverters with Neutral-Point Clamped (NPC) topology. The balancing is based on injecting zero-sequence voltage component in carrierbased modulation. The viability of the modulation techniques are verified by computer simulation and then tested on hardware.

An enhanced DC-DC boost converter based stand-alone PV-Battery OFF-Grid system with voltage balancing capability for fluctuating environmental and load conditions

ABSTRACT There is a requirement for a suitable DC-DC converter which can exhibit satisfactory performance in the case of OFF-Grid PV systems. This paper proposes a PV-Battery stand-alone system with an enhanced DC-DC boost converter and an efficient voltage balancing technique. The converter is designed to achieve the desired voltage gain at a lower duty-ratio as compared to the existing converter topology used in conventional stand-alone systems, thereby reducing the voltage stress across the switching devices. For extracting maximum power from the solar panel at every given point of operation, the Incremental Conductance Technique is used. A non-complex voltage balancing technique maintains the DC bus voltage constant with fast dynamic response. The system is highly reliable in case of converter fault and exhibits less initial transient time each time it is put to test. The performance of the proposed system is tested under varying input and varying load conditions with maximum overall system efficiency of around 93%. The stability of the system is investigated using a small signal model of the converter. The proposed stand-alone PV/Battery system is designed to handle a 1 KW load at 180 V DC voltage fed by 1.5 KW solar panel and 100Ah/24 V Li-ion Battery. The dynamic performance of the proposed system is verified through OPAL-RT 4510 platform.

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.

Performance analysis of capacitor voltage balancing in modular multilevel converter by sorting algorithm

&lt;span lang="EN-US"&gt;Due to the modularity of modular multilevel converter (MMC), therefore it has been considered as a substitute for the diode-clamp multilevel inverter in applications of high-voltage high-power. Where it can obtain any level of voltage without imposing complexity on the control system. This study analyses in detail the operation principle and balances the capacitor voltage of sub-module (SM) in modular multilevel converter by sorting algorithm. The output voltage control and capacitor voltage balancing technique are confirmed by MATLAB/Simulink and the obtained result has been discussed, where the capacitor voltage of the sub-module has controlled within the acceptable deviation limit, which is 5-10%. In addition, the circulating current has been controlled and reduced.&lt;/span&gt;

A Five-Level Nested Diode-Clamped Converter for Medium-Voltage Applications

This article presents a new three-phase five-level converter topology with a single dc source. The proposed topology combines the features of the conventional flying capacitor multicell and diode-clamped multilevel topologies. An important advantage of the proposed topology is the reduced volt-ampere, and hence, the volume, of the flying capacitors in its structure while keeping the same voltage blocking capability for semiconductor switches. The appropriate modulation strategy along with the flying capacitor voltage balancing technique is presented. To show the advantages of the proposed converter, different performance criteria such as switch count and rating, volt-ampere of flying capacitors, component cost, losses, and switching frequency are compared with some existing five-level topologies with a single dc source and the same voltage rating of switches. The results indicate that the proposed structure is superior to other five-level converters from different standpoints of the performance criteria. Simulation results are shown to verify the converter operation and its performance. The validity of the theoretical analysis is verified by experimentation on a scaled-down prototype system.

Integrated Multiport DC-DC and Multilevel Converters for Energy Sources

This paper presents a novel converter system for integrating multiple renewable energy sources for both dc and ac grids. The proposed converter system is formed by integrating a novel multiport dc converter topology with a multilevel inverter topology, aiming to achieve multiple source integration with low component count and higher efficiency on the multiport converter section and efficient dc to ac conversion on the multilevel inverter section. As compared to counterparts in literature, where each energy source requires its own dc converter and the dc to ac conversion is achieved using a two-level converter, the converter system proposed in this paper has more attractive features of buck-boost operation, better power quality characteristics and low part counts. Within the framework, an auxiliary circuit-based dc link voltage balancing technique is proposed to balance the voltage on the dc link as compared to the more complex control-based balancing scheme. Open and closed loop operations of the converter system are numerically verified using simulations and validated by a high-fidelity hardware-in-the-loop implementation platform.

A Novel Single DC Source Three-Phase Wye Packed U-Cell (Y-PUC) Converter

A new configuration of three-phase Wye Packed U-cells (Y-PUC) with a single DC source is proposed in this paper. In fact, this configuration represents a single DC source modular three-phase PUC converter. The DC source on PUC topology is replaced by a flying capacitor to obtain a suitable submodule. Moreover, the modularity of the Y-PUC configuration makes it an appropriate alternative for MMC applications. Furthermore, the proposed structure is an advantageous configuration for high voltage applications such as high voltage direct current (HVDC) transmission lines with the capability of DC fault handling. All PUC topologies such as PUC5, PUC7, PUC9, PUC15 can be replaced in the modules of this proposed single-phase and three-phase configuration to multiply the load voltage levels for improving the output waveform. Active voltage balancing technique through carrier-based modulation is applied. System modeling and operating sequences are developed. Simulation and experimental results are presented and discussed to validate the performance of the proposed structure.

Active Voltage Balancing Control of a Seven-Level Hybrid Multilevel Converter Topology

The series connection of a standard three-level active neutral-point-clamped (ANPC) inverter and two cascaded H-bridge (CHB) modules comprising the flying capacitors (FCs) instead of the isolated dc voltage sources forms a seven-level hybrid topology that is referred to as improved ANPC (I-ANPC) converter. This article proposes an active voltage balancing technique for control of this hybrid multilevel inverter. The suggested method is based on a set of effortless logic equations that aim to stabilize the FC voltages within the CHB modules at their requisite reference values as well as to control the output voltage of the overall hybrid converter based on the phase-shifted-carrier pulsewidth modulation strategy. The experimental results obtained from a single-phase I-ANPC inverter's prototype are presented to validate the proposed control technique and its simple logic equations.

Single-Phase Three-Wire Power Converters Based on Two-Level and Three-Level Legs Using a Space-Vector PWM-Based Voltage Balancing

This article proposes four converters for interfacing a single dc power source and loads of a single-phase three-wire system. The topologies of the proposed converters are based on two-level (2L) and three-level neutral point clamped (NPC) legs. For regulating the dc-link capacitors of the NPC-based converters, a dc-link voltage-balancing technique is proposed to balance the neutral-point voltage using the space-vector pulsewidth modulation, considering the harmonic distortion of the output voltages and the semiconductor losses from an algorithm that defines the vector sequences to be applied. These characteristics make the proposed converters suitable for applications in microgrid employing dc distributed energy resources or ac power supply by adding ac-dc stage. The proposed converters are compared to a conventional 2 L converter from simulated results for evaluating the semiconductor losses in balanced and unbalanced load scenarios. Experimental results are presented to verify the effectiveness of the proposed voltage-balancing technique and to validate the converters.

Active Voltage Balancing and Thermal Performance Analysis of Dual Flying-Capacitor Active Neutral-Point-Clamped (DFC-ANPC) Inverters

Multilevel inverters provide appealing advantages such as improved efficiency, superior thermal performance, better distribution of the switching and conduction power losses, smaller size of passive components including output ac filters and EMI filters, as compared to their two-level counterparts. The flying-capacitor (FC)-based topologies are attaining more attentions, and are finding lots of medium-voltage and low-voltage industrial and residential applications. The FC-based active neutral-point-clamped (ANPC) inverter, as a hybrid topology based on the three-level ANPC and the FC-based configurations, offers outstanding advantages including the reduced number of FCs as well as switching power cells, improved efficiency, and enhanced power quality. However, the utilization of high-voltage line-frequency switches, as a major drawback, hinders the ANPC converter from expansion and penetration into the high-voltage ranges. The dual flying-capacitor (DFC)-ANPC topology resolves this issue through introducing the zero-voltage-switching (ZVS) feature into the line-frequency devices. This soft-switching makes it possible to use the series connection of several low-voltage devices for the realization of the high-voltage switches without having the transient voltage imbalance issues. This article studies the thermal benefits that are achieved in the DFC-ANPC topology alongside the ZVS operation of its line-frequency high-voltage switches. Furthermore, an active voltage balancing technique, based on logic-equations, is proposed in this article for control of the FCs' voltages. The experimental results are provided to validate the improved thermal performance of the DFC-ANPC topology as well as the active balancing technique for the regulation of the FC voltages.

Three phase PUC5 inverter fed induction motor for renewable energy applications

&lt;p&gt;This paper gives the overview three phase 5 level packed U cell (PUC5) inverter fed Induction Motor feed from renewable energy sources for electric vehicles and water pump set in agriculture applications. PUC5 inverter requires a minimum number of semiconductor devices, one PV panel and only one capacitor in each phase. Maximum all possible switching sequences are analyzed and sensor less voltage balancing technique depending on simple switching modes was integrated as level shifted PWM controller for control the PUC5 inverter switches. Sensor less voltage balancing fixes the capacitor voltage (V&lt;sub&gt;c&lt;/sub&gt;) at half of the PV source (V&lt;sub&gt;dc&lt;/sub&gt;) magnitude in each phase, which results the symmetric five level wave in phase voltage output and seven level waveform in line voltage with less harmonics. This topology minimizes the complication in the control system which creates the PUC5 inverter most suitable for industrial applications and market requirements.&lt;strong&gt; &lt;/strong&gt;It is compared with other popular multilevel inverters In terms of component count, voltage rating, voltage balancing and complexity etc. In order to test the performance proposed PUC inverter it is tested with rated load with Matlab/Simulink. The results obtained have shown good dynamic performance under different conditions.&lt;/p&gt;

A Seven-Level VSI With a Front-End Cascaded Three-Level Inverter and Flying-Capacitor-Fed H-Bridge

Multilevel inverters (MLIs) are playing a pivotal role in the power sector with potential applications, such as interfacing renewable energy sources with the grid and several industrial drive applications. MLIs with a smaller number of switching devices are more promising due to their compact size, reduced cost, and higher efficiency compared with their traditional counterparts. This paper, therefore, presents a new three-phase seven-level inverter. This topology is a combination of two cascade-connected two-level voltage-source inverters (VSIs) and H-bridge cells with flying capacitors (FCs). This paper presents the operating principle and the balancing technique for the dc-link capacitors and FCs. The generation of various output voltage levels and the limitation of the sinusoidal pulsewidth modulation control for FC voltage balancing is also presented. The number of components in the proposed circuit configuration and their voltage ratings are considerably lower compared with the recently proposed topologies. The behavior of the proposed circuit configuration is first assessed with simulation studies and is then tested with a laboratory prototype. The simulation and experimental results validate the effectiveness of the proposed topology and the voltage balancing technique.

A Modified Neutral Point Balancing Space Vector Modulation for Three-Level Neutral Point Clamped Converters in High-Speed Drives

This paper describes a high-performance neutral point voltage balancing technique for a neutral point clamped (NPC) converter. Conventional neutral point voltage balancing methods do not function well under low power factor, low pulse ratio, and near-unity modulation index operation conditions. These conditions are essentially dominant operation conditions for aircraft starter/generator systems. This paper introduces an alternative space vector modulation technique for three-level NPC converters in an aircraft starter generator system. The selection of voltage space vectors is optimized for high modulation index and low power factor operation. Disturbances caused by a low pulse ratio are also compensated. The proposed method maintains neutral point voltage balance and ripple minimization over the full range of operating conditions. This paper also provides a detailed analysis of the sources of neutral point voltage imbalances and ripples in high-speed drives with deep flux weakening. Simulation results obtained from a Simulink/PLECS model and experimental results obtained from a 45 kVA, 32 krpm aircraft starter generator test rig prove that the proposed method eliminates the neutral point voltage imbalance and significantly reduces the neutral point voltage ripple.

Control of AC/DC Modular Multilevel Converter

In recent years, a special attention is paid to grid connected multilevel converters. These converters have specific use in industry in a high power, medium-voltage and high-voltage applications. This paper presents new control algorithm for single-phase AC/DC modular multilevel converter with target application as a traction converter connected directly to trolley wire. The proposed control strategy presents resonant controllers for converter current control with fundamental frequency adaptation. The fundamental frequency estimation and voltage synchronization is based on Second Order General Integrator Phase Locked Loop (SOGI-PLL). Furthermore, this paper presents robust voltage balancing technique for multilevel converter based on energy calculation of DC-link capacitances. It provides voltage balancing of multilevel converter cells with unbalanced load. The resulting control algorithm has low total harmonic distortion of converter trolley current even under unbalanced load condition. The algorithm was experimentally verified on the low voltage laboratory prototype with 3 H-bridge cells.DOI: http://dx.doi.org/10.5755/j01.eie.24.6.22282

A DC Link Sensor-Less Voltage Balancing Technique for Cascaded H-Bridge Multilevel Converters With Asymmetric Selective Harmonic Current Mitigation-PWM

A grid-tied cascaded H-bridge (CHB) converter with low frequency modulation techniques needs to meet power quality standards. At the same time, the effects of grid voltage harmonics on CHB converter's current harmonics must be considered in the modulation techniques. Furthermore, the dc link voltages of grid-tied converters need to be regulated. In this paper, an asymmetric selective harmonic current mitigation-pulse width modulation (PWM) (ASHCM-PWM) technique is used to meet the current harmonic limits of a power quality standard with the effects of grid voltage harmonics considered in the equation set of its optimization process. A voltage balancing technique based on the average power of each cell is derived to regulate the dc link voltages of the CHB converters without using dc voltage sensors. By using the proposed voltage balancing technique, the CHB converters do not need complicated dc link voltage controllers. As a result, the cost and complexity of the grid-tied converters can be significantly reduced. Simulations and experiments were conducted on a 7-level grid-tied CHB converter to validate the proposed voltage balancing technique with ASHCM-PWM modulation technique.

Control of a Single-Phase Cascaded H-Bridge Active Rectifier Under Unbalanced Load

Cascaded H-bridge (CHB) converter technology is actually the most popular solution for grid-connected converters in both medium- and high-voltage applications. This paper introduces a new control of a single-phase CHB active rectifier. The control uses a direct grid current control based on adaptive resonant controllers. The resonant controllers are adapting to slow fluctuation of ac grid frequency. The challenging problem of CHB converters is dc-link capacitor voltage balancing especially under unbalanced load conditions. This paper presents a reliable voltage-balancing technique utilizing energy estimation of particular dc-link capacitor banks and simple prediction of the changes of their energies. A nonlinear behavior of the converter caused by power semiconductors voltage drops and dead-time effects is minimized by auxiliary adaptive resonant controllers. The resulting control has very good performance, including the operation under unbalanced load conditions, and achieves low total harmonic distortion of converter grid current. The theoretical results were verified by experiments made on the developed CHB active rectifier prototype with three power cells in cascade.

A Series Regeneration Converter Technique for Voltage Balancing of Energy Storage Devices

&lt;p&gt;&lt;em&gt;A single series resonant converter has been designed to balance the voltage level of a storage battery for electric vehicles. The proposed design has been simulated and verified by using two 100F supercapacitors instate of the conventional rechargeable battery. A voltage monitoring circuit detects the voltage condition of the individual capacitor and sends the voltage status to the control circuit for action. A technique has been developed to control a set of switches to transfer the current between the capacitor to balance the voltage level. The MATLAB simulated result shows the balancing circuit decreases the voltage difference between the two supercapacitors from 200 mV to 0V in 140 seconds, which is less than the existing methods. This fast voltage balancing technique can be used in the battery management system or electric vehicles for long lasting the battery life.&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt; &lt;/em&gt;&lt;/p&gt;&lt;strong&gt;&lt;em&gt;Keywords&lt;/em&gt;&lt;/strong&gt;&lt;em&gt;: Voltage balancing; electric vehicles; supercapacitor; battery; series resonant converter&lt;/em&gt;