Capacitor Voltage Stress Research Articles

Switched‐coupled‐inductor Z‐source inverter with a high boost inversion capability

A novel converter with a three-winding coupled inductor, called switched-coupled-inductor Z-source inverter (SCI-ZSI), is developed based on the switched-and-coupled inductor technology in this study. Compared with the conventional switched-inductor Z-source inverter and trans-Z-source inverter, the novel inverter had a higher voltage-boosting capability. In addition, the improved topology shared a common ground point between the DC source and the inverter bridge. Under the same modulation index and load conditions, the input diode and capacitor voltage stress of the proposed inverter were lower than those of the other topologies. The operating principles, impedance-network design, voltage and current stress are presented. The theoretical findings were verified by simulation and experimental results.

LC Impedance Source Bi-Directional Converter with Reduced Capacitor Voltages

This paper proposes an LC (Inductor and Capacitor) impedance source bi-directional DC–DC converter by redesigning after rearranging the reduced number of components of a switched boost bi-directional DC–DC converter. This new converter with a conventional modulation scheme offers several unique features, such as a) a lower number of components and b) reduced voltage stress on the capacitor compared to existing topologies. The reduction of capacitor voltage stress has the potential of improving the reliability and enhancing converter lifespan. An analysis of the proposed converter was completed with the help of a mathematical model and state-space averaging models. The converter performance under different test conditions is compared with the conventional bi-directional DC–DC converter, Z-source converter, discontinuous current quasi Z-source converter, continuous current quasi Z-source converter, improved Z-source converter, switched boost converter, current-fed switched boost converter, and quasi switched boost converter in the Matlab Simulink environment. MATLAB/Simulink results demonstrate that the proposed converter has lesser components count and reduced capacitors’ voltage stresses when compared to the topologies mentioned above. A 24 V to 18 V LC-impedance source bi-directional converter and a conventional bidirectional converter are built to investigate the feasibility and benefits of the proposed topology. Experimental results reveal that capacitor voltage stresses, in the case of proposed topology are reduced by 75.00% and 35.80% in both boost and buck modes, respectively, compared to the conventional converter circuit.

Analysis and design of an isolated high step‐up converter based on the secondary side quasi‐resonant loops

In a high step-up converter, the primary side input current contributes a significant share of total power loss. Meanwhile, high-voltage stresses of secondary side components are also big issues. This study proposes an isolated converter with secondary side quasi-resonant loops. The push–pull structure is adopted to reduce active switch numbers so the primary side power loss can be controlled in a very minor range. The newly added resonant loops on the secondary side significantly decrease the current stresses of the resonant capacitors, so the power loss caused by capacitor equivalent-series-resistance is reduced. The voltage stresses of diodes and capacitors on the secondary side are also decreased by an improved symmetrical-voltage-quadrupler-rectifier structure. The proposed converter is with the maximum voltage gain equal to 4 without consideration of the transformer. Therefore, it is helpful to decrease the transformer turns ratio. The operation process is analysed in detail and the design considerations are also summarised. Theoretical analysis is verified by the experimental results of a 400 W prototype with 34–40 V input and 380 V output.

An extendable single‐switch n‐cell boost converter with high voltage gain and low components stress for renewable energy

SummaryBoost converters have been widely employed in industrial applications, and cascading boost converters is a mature technique to realize ultrahigh voltage gains. However, the cascade structure inevitably increases the voltage stress of buffer capacitors, resulting in high costs and low energy efficiency. Targeting this issue, in this study, we propose a novel extendable single‐switch n‐cell boost converter (ESSnB), which utilizes the same number of components as the conventional positive output boost converter, but has lower buffer voltage stresses. Simulation and experimentation are conducted in this study, which verify the effectiveness and superiority of the proposed ESSnB over conventional boost converters.

Switched-LC Based High Gain Converter With Lower Component Count

A compact high step up dc–dc converter with continuous input current and lower device voltage stress is a prime requirement for renewable application. In this article, a high gain dc–dc converter is proposed, which combines the concept of switched inductor and switched capacitor along with a unique interconnection of input–output. This arrangement reduces capacitor voltage stress. The proposed converter has reduced conduction losses, reduced components count, and low voltage stress across the devices. Besides, the proposed converter has lower inductor current ripple, which is suitable for renewable integration. The operation and steady-state analysis of the converter are done in continuous current mode. For the proposed converter, voltage and current stress and the losses are calculated analytically. A comparative analysis is presented to prove the potential of the proposed converter. The dynamic analysis of the proposed converter is performed to regulate the output voltage. Finally, an experimental set up is designed to test the converter under both distinct power ratings and closed loop.

Series-type switched-inductor Z-source inverter

To solve the disadvantages of the traditional Z-source inverter (ZSI), this paper investigates a series-type switched-inductor Z-source inverter (SSI-ZSI) topology. It not only preserves the advantages of the traditional ZSI, but also improves the voltage gain. On the condition of the same voltage gain, the capacitor voltage stress is reduced, the soft start characteristic can be achieved and the inverter can be immune to the damage of the inrush current. The circuit structure and operating principle are analyzed in detail; the simulation model and the experimental platform are built. The simulation and experimental results verify the rationality and superiority of the circuit topology.

A Nonisolated Bidirectional DC–DC Converter With High Voltage Conversion Ratio Based on Coupled Inductor and Switched Capacitor

In this article, a nonisolated bidirectional dc-dc converter is proposed based on coupled inductor (CL) and switched capacitor (SC). The converter can achieve a high voltage conversion ratio (VCR) by using CL and SC. The CL is operated not only as a filter inductor to regulate voltage but also as a transformer to improve the VCR. Furthermore, the voltage stresses of capacitors and switches are reduced by introducing SC structure. The pulsewidth modulation plus phase-shift control is employed, where the duty cycle is used to ensure that the voltages of two sides are matched and the phase-shift angle is used to control the direction and amount of power flow. In addition, all the switches can achieve zero voltage switching in both forward and backward modes under a wide operating range, which can improve the efficiency of power conversion. The operating principle and steady-state analysis are examined, and a 400-W prototype is designed to verify the validity of the proposed converter.

An effective control topology for multilevel inverter with a Z-source network

This document is used to explain about an efficient controlling method of multi level inverter with a Z-source network. The proposed method is an efficient control design for the optimisation difficulty which contains maximising or minimising of a real operation by methodically deciding input values from within a permissible group and calculating the value of the operation. The reduction of error between the real load voltage and its reference value is optimising the gain parameters in the projected control methodology. It contains better capability to reply quick alterations in different operating situations. The projected method is used to decrease the inrush current, harmonics, increase effectiveness and it develops the exchange effectiveness for broad range of loading situation. It also improves the guideline of the output voltage and capacitor voltage stress. The projected technique is executed in MATLAB/Simulink platform and the efficiency is compared with the predictable methods.

A Bidirectional LLCL Resonant DC-DC Converter With Reduced Resonant Tank Currents and Reduced Voltage Stress of the Resonant Capacitor

In this paper, a bidirectional inductor-inductor-capacitor-inductor (LLCL) resonant dc-dc converter is presented. Compared with the conventional LLC, a parallel-connected inductors structure is employed into the resonant tank. By virtue of this unique resonant tank, LLCL exhibits the following desirable features: 1) good voltage gain regulation capability in bidirectional power flow applications; 2) zero-voltage-switching turn-on of the power switches in a wide load range; 3) compared with the other bidirectional LLC-type resonant converters, lower resonant tank currents and lower resonant capacitor voltage stress are achieved under the same working conditions. The topology derivation and operating principles of LLCL are shown, and the vital characteristics of LLCL are especially discussed. Moreover, based on battery applications in energy storage systems, in order to make the voltage gain range of LLCL meet the requirements while minimizing the resonant tank currents, a parameter design method is conducted. Finally, a 500-W prototype is established to verify the operating principles and design effects of the proposed converter.

A Step Up/Down Power-Factor-Correction Converter with Modified Dual Loop Control

A step up/down AC/DC converter with modified dual loop control is proposed. The step up/down AC/DC converter features the bridgeless characteristic which can reduce bridge-diode conduction losses. Based on the step up/down AC/DC converter, a modified dual loop control scheme is proposed to achieve input current shaping and output voltage regulation. Fewer components are needed compared with the traditional bridge and bridgeless step up/down AC/DC converters. In addition, the intermediate capacitor voltage stress can be reduced. Furthermore, the top and bottom switches still have zero-voltage turn-on function during the negative and positive half-line cycle, respectively. Hence, the thermal stresses can also be reduced and balanced. Simulation and experimental results are provided to verify the validity of the proposed step up/down AC/DC converter and its control scheme.

Neutral point clamped quasi Z source inverter for photovoltaic systems

<p>Multilevel inverters are becoming popular for power conversion in renewable energy systems, AC-DC hybrid micro grids etc. The voltage stress and inrush current through these inverter leg switches are quite higher as compared to the load ratings which increase the chances of inverter leg switch failure. A three level neutral point clamped quasi Z source inverter topology is discussed in this paper which has the features of lower component count, reduced capacitor voltage stress, and it can be operated at different control strategies to achieve wide range of voltage boosting ability, suited for photovoltaic (PV) systems. It also ensures continuous input current irrespective of the DC supply voltage variations and injects stable and smooth power to the load/grid. The effectiveness of the proposed inverter is verified by simulation results in MATLAB Simulink model as well as performing experiment with the help of a laboratory prototype.</p>

An Improved Design Methodology of the Double-Sided LC-Compensated CPT System Considering the Inductance Detuning

This paper proposes an improved design methodology of the double-sided LC -compensated capacitive power transfer (CPT) system considering the inductance detuning. Compared to the perfect-resonant scenario, this paper shows that the inductance detuning has the benefit to achieve the soft-switching condition for the CPT system, and the output current and internal voltage stresses can also be maintained within the desired range. The contributions of this paper are summarized in three parts. First, it analyzes the impacts of the inductance variations on the system frequency property, including the input current, output current, and internal capacitor voltage stresses. Second, it proposes three principles to detune the inductances as the methodology to design a CPT system. Third, a prototype is implemented, which achieves 368.5 W power transfer across a 400 mm × 400 mm × 4 mm glass layer with 91.8% dc–dc efficiency. Experimental results validate that the proposed design principles are satisfied, showing that the output current is within the desired range, the input soft-switching condition is achieved, and the internal voltage stresses are within the safety limit. Moreover, the efficiency and frequency properties are also validated by the experimental results, showing a wide power range of the high-efficiency operation (higher than 90%) and a wide frequency bandwidth of the soft-switching operation (from 0.96 to 1.12 MHz).

LLC Resonant Voltage Multiplier-Based Differential Power Processing Converter Using Voltage Divider with Reduced Voltage Stress for Series-Connected Photovoltaic Panels under Partial Shading

Partial shading on photovoltaic (PV) strings consisting of multiple panels connected in series is known to trigger severe issues, such as reduced energy yield and the occurrence of multiple power point maxima. Various kinds of differential power processing (DPP) converters have been proposed and developed to prevent partial shading issues. Voltage stresses of switches and capacitors in conventional DPP converters, however, are prone to soar with the number of panels connected in series, likely resulting in impaired converter performance and increased circuit volume. This paper proposes a DPP converter using an LLC resonant voltage multiplier (VM) with a voltage divider (VD) to reduce voltage stresses of switches and capacitors. The VD can be arbitrarily extended by adding switches and capacitors, and the voltage stresses can be further reduced by extending the VD. Experimental verification tests for four PV panels connected in series were performed emulating partial shading conditions in a laboratory and outdoor. The results demonstrated the proposed DPP converter successfully precluded the negative impacts of partial shading with mitigating the voltage stress issues.

A Negative Embedded Differential Mode Γ-Source Inverter With Reduced Switching Spikes

Magnetically coupled impedance source networks (MCIS) are capable of producing higher voltage gains at the expense of high switching voltage spikes due to the presence of leakage inductance. These voltage spikes decorate the converter efficiency and life expectancy of switches. Therefore, to reduce the voltage spikes, a negative embedded differential mode gamma source inverter (NEDM ${{\Gamma }}$ ZSI) is presented in this brief. The proposed inverter can achieve higher voltage gains with reduced switching voltage spikes and low capacitor voltage stresses compared to other MCIS networks. Also, the proposed inverter draws continuous input current from the dc mains, having a common ground, and uses the minimum number of component in a circuit. The operating principle of the proposed NEDM ${{\Gamma }}$ ZSI is analyzed in electrical and magnetic domains. The ability of the proposed impedance network, in terms of voltage spike suppression has been verified experimentally using DC-DC converter configuration. Finally, the performance of a NEDM ${{\Gamma }}$ ZSI is validated with simulation and experimental verification using a single-phase inverter configuration.

A New Nonisolated Quasi-Z-Source Inverter With High Voltage Gain

This paper proposes a new high-boost quasi-Z-source inverter (qZSI) with combined two quasi-Z-source networks, which has a common ground between the input source and the inverter bridge. Compared with other noncoupled inductor-based (q)ZSIs, by using the same total number of passive and active components, the proposed inverter provides higher boost capability, requires smaller inductance and capacitance values at the impedance network, achieves lower voltage stress across the active switching devices, and has higher modulation index for the inverter bridge to improve the output waveform quality. Although the proposed inverter has the same voltage boost factor with the enhanced boost (q)ZSIs (EB-ZSI) and EB-qZSIs, the proposed scheme has lower capacitor voltage stress than EB-ZSI and has higher efficiency than EB-qZSI. The topological configuration, operating principles, power loss analysis, and performance comparison with other high-boost (q)ZSIs are presented. Finally, both simulations and experimental results are given to validate the aforementioned characteristics of the proposed topology.

A Hybrid Cockcroft–Walton/Dickson Multiplier for High Voltage Generation

This paper presents a voltage multiplier topology that is a hybrid between a Cockcroft–Walton multiplier and a Dickson charge pump. The Cockcroft–Walton structure exhibits significant output voltage drop under load as the number of multiplier stage increases. This is because all coupling capacitors are connected in series. Dickson charge pump mitigates this issue by connecting all capacitors in parallel. But this solution comes at the expense of large capacitor voltage stress at the last multiplier stage. The proposed hybrid structure arranges some capacitors in parallel and others in series, thereby achieving low output voltage drop and low capacitor voltage stress at the same time. We develop a model that predicts hybrid multiplier's performance and validates it experimentally. We also demonstrate a 60–2.25 kV dc–dc converter based on a 16-stage hybrid voltage multiplier which achieves a voltage gain of 12.8 while keeping the highest capacitor voltage stress to 660 V.

Modularized Differential Power Processing Architecture Based on Switched Capacitor Converter to Virtually Unify Mismatched Photovoltaic Panel Characteristics

Photovoltaic (PV) strings consisting of multiple panels suffer from partial shading or characteristic mismatch issues, such as a significant reduction in power yield. Various kinds of differential power processing (DPP) converters have been developed to prevent the negative impacts of substring-level partial shading. For panel-level applications, however, conventional DPP converters face a variety of challenges, such as impaired extendibility and increased voltage stress of circuit elements. This paper proposes a switched capacitor converter (SCC)-based modular DPP architecture. Modules, each containing series-connected panels with a panel-level DPP converter, are connected through a switchless module-level DPP converter, and PV panel characteristics are unified at module- and panel-levels. The number of panels in each module is fixed, while the number of modules can be arbitrarily extended without redesigning DPP converters, hence offering good modularity. In addition, since voltage stresses of capacitors in the proposed architecture can be reduced lower than half the module voltages, the proposed DPP system realizes all-ceramic-capacitor SCC circuit by properly determining the module voltages. A prototype for eight panels, which were grouped into two modules, was built, and laboratory and field tests were performed. The experimental results demonstrated the enhanced power yield from the partially shaded PV string.

Design of a Double-Sided LC Compensated Capacitive Power Transfer System With Capacitor Voltage Stress Optimization

Capacitive power transfer (CPT) systems usually have high voltage stresses among coupler plates and compensation capacitors due to small coupling capacitances. High voltages across the coupler plates will incur the strong electric field emission, and it is thus difficult to select compensation capacitors with high voltage stresses. To solve this problem, this brief analyzes a double-sided LC compensated CPT system systematically and finds an operating frequency to realize the load-independent constant current (CC) output and input zero-phase angle (ZPA) simultaneously. Without reactive power in the circuit, a design method is proposed to determine the compensation parameters and operating frequency using the given voltage ratings of coupler plates and compensation capacitors. Thus, voltage stresses among these capacitors could be optimized under their predesigned voltage ratings. The sensitivities of input impedance, output current to variations of compensation parameters are also discussed to realize soft switching. Finally, a prototype of the CPT converter with two types of proposed parameters and symmetric parameters is built to verify the analysis.

SiC Stacked-Capacitor Converters for Pulse Applications

Pulse power converters demands single high voltage and current pulse shape waveform in high temperature, heavy neutrons, and ions radiation environment, where ${\text{50}}\% \sim {\text{75}}\%$ voltage derating margin is typically required for the power devices. silicon carbide (SiC) mosfet s are promising to improve radiation reliability owing to wide band-gap. However, the conventional converters with off-the-shelf commercial SiC mosfet s cannot provide enough voltage margin accordingly. A stack-capacitor pulse converter topology is proposed to reduce the voltage stress of switching devices and capacitors and improve the voltage derating capability significantly. The main idea is to build high voltage with multiple low voltage stacks instead of single high voltage capacitors, so that SiC mosfet s can be applied with improved voltage margin. The method is to charge the stack-capacitors in parallel with fast charging speed, and discharge in series for high pulse voltage. The converter operates at higher switching frequency, which reduces the weight and size of the magnetic components. A 300-kHz prototype with 18–28 V input and 1 kV/ 100 A output was built using 650 V SiC devices, demonstrating 75% reduction of the voltage stress of the capacitors and power devices compared with the conventional converters.

Embedded dual switched‐capacitor based continuous input current switched‐inverter for renewable energy application

This study presents a high voltage gain embedded dual switched-capacitor-based continuous input current impedance source inverter for renewable energy applications. Renewable energy resources have low-output voltage generation capability, and the converter needs to operate on the extreme duty cycle for high voltage requirements. To achieve high voltage gain, a conventional impedance source inverter needs to operate on a high duty cycle, which leads to the reduction in modulation index. Operating at a reduced value of modulation index leads to poor inversion operation with poor output power quality. In order to take care of this issue, an embedded dual switched-capacitor-based inverter is presented for high voltage gain in low shoot-through duty cycle. The proposed inverter is suitable for DC–AC power conversions such as solar photovoltaic where a low-input voltage is available, and it needs to be converted into high DC–AC output voltages. Anatomisation of operating principle, steady-state analysis, passive design criteria, and comparison are discussed. The proposed inverter also has less capacitor voltage stress, less diode current stress, and higher efficiency than other impedance-source inverters. The operation of the proposed inverter is verified through simulations and experimental results with a 600 W prototype.