Proposed Power Conditioner Research Articles

Driving Asynchronous Induction Launchers: Design and Simulation of a Novel Power Conditioner with a Brief Review

The design and implementation of an asynchronous coilgun’s structure is relatively simple compared with other types of linear induction launchers. In order to drive rotating electrical machines, multilevel converter structures have attracted much attention in recent decades as a result of their unique advantages. A linear induction launcher has an identical theoretical background to rotating electrical machines; therefore, multilevel converter structures can be applied to them as well. The stator of a launcher can be excited by generators or capacitor groups whose voltage and frequency might be fixed or changeable by a power conditioner. The aim of this study is to design and simulate a novel power conditioner as a multilevel converter topology for the power source of an asynchronous coilgun. Cascaded H-Bridge multilevel converter topology constitutes the proposed power conditioner in which a level-shifted pulse-width modulation method is used to generate appropriate pulses for the power switches of the converter. Additionally, variable-voltage variable-frequency control is involved in the converter’s modulation.

Single-phase transformerless power conditioner based on a two-leg of a nine-switch converter

An interesting solution for problems associated with system voltage, such as sags and swells, as well as those associated with current such as low power factor and harmonic distortion is the unified power quality conditioner. However, one of its drawbacks is the high number of semiconductor devices since its conventional topology presents two full-bridge converters in a back-to-back configuration. Although the six-switch two-leg converter has a feature of presenting two sets of single-phase output terminals, the same as two full-bridge converters, but with a reduced number of switches (six, instead of eight), it has never been used in single-phase power conditioning systems. Therefore, the aim of this paper is to propose a single-phase transformerless power conditioner based on the six-switch two-leg converter. In this solution, there are two sets of single-phase outputs, each set behaving as an independent converter. The top unit of the converter is connected in parallel to the load by means of a series LC filter tuned to a specific frequency, working as a hybrid power filter and being responsible for the dc-link voltage regulation and the compensation of current harmonics generated by the non-linear load. The bottom unit works as a dynamic voltage restorer and it is responsible for compensating harmonics, sags or swells in the grid voltage, in such way that the load receives a sinusoidal voltage waveform. The challenges of the single-phase transformerless power conditioner that is proposed in this paper are different of the three-phase systems based on nine-switch converter previously proposed in literature. Dealing with the circulating current makes mathematical model and the modulation strategy completely different and, therefore, all equations have been developed for this specific single-phase power conditioner application. The proposed power conditioner presents four main advantages when compared with other configurations available in literature: (a) it is a transformerless solution; (b) it has a reduced number of switches; (c) it has a reduced dc-link voltage and rated power because of its hybrid power filter characteristics; (d) it does not have to handle with dc-link voltage unbalance. Experimental results demonstrate the validity and the effectiveness of the proposed topology.

Single-Phase Two-Stage Seven-Level Power Conditioner for Photovoltaic Power Generation System

This paper presents a new power conditioner with the inherent benefits of boosting, generation of seven-level output voltage with minimum leakage current in a grid-connected photovoltaic (PV) power generation system. The proposed power conditioner is an upgrade of a front-end multioutput dc–dc boost converter and an asymmetrical seven-level inverter. A high-frequency transformer (HFT) employed in front-end converter produces balanced dc-link voltages to generate the seven-level output voltage. The leakage current caused by the parasitic capacitance of the PV panel is minimized by providing a common-mode conducting path to the inverter. This results in a reduction of the leakage current well below the VDE0126-1-1 grid standards. Furthermore, the proposed configuration utilizes a minimum number of devices for every level generation, which reduces the control complexity and also improves the system efficiency. The dynamic performance of the system is tested for intermittent changes in the PV characteristics for grid-connected operation. The proposed power conditioner is simulated using MATLAB software, and a laboratory prototype of 750 W is developed to validate its feasibility. Finally, a comparison is made with other recently proposed seven-level inverters to highlight the benefits of this power conditioner over others.

Eight-Switch Power Conditioner for Current Harmonic Compensation and Voltage Sag Mitigation

The nine-switch converter has been proposed recently, and since then, a large number of applications have been investigated, particularly as a substitute to the dual-bridge (back-to-back) converter. The main advantage of the nine-switch converter is its lesser number of switches (9 instead of 12 of the back-to-back converter), which has, as a tradeoff, some restrictions in the total attainable amplitude at its outputs, dependent on the phase shift between its two terminal sets. However, with an appropriately designed control scheme, the nine-switch converter is shown to favorably raise the overall power quality, justifying its role as a power conditioner at a reduced semiconductor cost. The proposed power conditioner has only eight switches, being composed by a unit for voltage sag mitigation and another unit for current harmonic compensation. Simulation and experimental results confirm the validity of the proposed method.

Modified Grid-Connected CSI for Hybrid PV/Wind Power Generation System

The principle of a power conditioning unit for hybrid PV/wind power generation system is proposed. The proposed power conditioner is based on the current source inverter (CSI) topology. All energy sources are connected in parallel with a DC-bus through the modified wave-shaping circuits. To achieve the unity power factor at the utility grid, the DC-link current can be controlled via the wave-shaping circuits with the sinusoidal PWM scheme. In this work, the carrier-based PWM scheme is also proposed to minimize the utility current THD. The power rating of the proposed system can be increased by connecting more PV/wind modules through their wave-shaping circuits in parallel with the other modules. The details of the operating principles, the system configurations, and the design considerations are described. The effectiveness of the proposed CSI is demonstrated by simulation results.

Power Conditioner for Variable-Frequency Drives in Offshore Oil Fields

The proliferation of variable-frequency ac motor drives (VFDs) as submersible pumps in oil exploration has aggravated many power-quality problems on the distribution network, for which VFDs are themselves susceptible to maloperation. The distortion in the input voltage waveform is a major issue, since the offshore power system cannot be regarded as a stiff source, and thus, distortions in the voltage waveform become more severe, which disturbs other loads connected at the point of common coupling (PCC). The oil fields require the operation of many parallel-connected VFDs on the same bus. Such a system significantly increases the power-quality problems on the distribution network. In this paper, an active power conditioner which is connected in series between the source and the PCC, and its dc bus shared with one of the VFDs connected to the bus, is proposed to mitigate a majority of power-quality problems for the whole bus. The proposed single power conditioner is sufficient to block the harmonic currents flowing toward the source, balance the currents from the source side, protect the VFDs on the bus against sag/swell at PCC, protect preinstalled passive filters connected with VFDs against series and parallel resonances, and maintain regulated balanced voltages at PCC. Investigations are carried out to validate the use of the proposed topology of a power conditioner to safeguard the distribution system and a set of VFDs against major power-quality problems. The proposed power conditioner employs a new control scheme based on an indirect current control for its effective operation under varying load conditions on different VFDs connected to the same bus.

High-Frequency Flyback Transformer Linked PWM Power Conditioner with An Active Switched Capacitor Snubber

A single active capacitor snubber-assisted soft-switching sinewave pulse modulation utility-interactive power conditioner with a three-winding flyback high frequency transformer link and a bidirectional active power switch in its secondary side has been proposed With the aid of the switched-capacitor quasi-resonant snubber cell, the high frequency switching devices in the primary side of the proposed DC-to-AC sinewave power inverter can be turned-off with ZVS commutation. In addition to this, the proposed power conditioner in the DCM can effectively take the advantages of ZCS turn-on commutation. Its output port is connected directly to the utility AC power source grid At the end, the prototype of the proposed HF-UPC is built and tested in experiment. Its power conversion conditioning and processing circuit with a high frequency flyback transformer link is verified and the output sinewave current is qualified in accordance with the power quality guidelines of the utility AC interactive power systems.

A multi‐functional power conditioner with real‐time voltage regulation for energy saving

AbstractThis paper presents the design details of a multi‐functional three‐phase four‐wire power conditioner. The proposed power conditioner can compensate the reactive power, harmonic current, unbalanced power, and zero‐sequence current of the load with a capacity‐limitation manner. It can also simultaneously regulate multiple load voltages based on the prescribed Power–Voltage characteristic of distinct loads for real‐time energy saving. The theoretical analysis and detailed design procedure of the controllers performing various functions are presented. A 6‐kVA experimental system with two induction motors and various nonlinear loads is implemented for the related studies and the results are presented in this paper. The feasibility and effectiveness of the proposed control scheme are confirmed through measured results obtained from practical hardware experiments. Copyright © 2006 John Wiley & Sons, Ltd.

Dual-Mode Time-Sharing Sinewave-Modulation Soft Switching Boost Full-Bridge One-Stage Power Conditioner Without Electrolytic Capacitor DC Link

This paper is aimed at presenting a novel system topology and control scheme of a selective dual-mode pulse-modulated high-efficiency single-phase sinewave power-conversion circuit for the new energy generation and storage applications. This power-conversion system is composed of a time-sharing-operated sinewave-absolute-modulation boost chopper with a bypass diode in the first power conditioning and processing stage and time-sharing sinewave partially pulse-modulated full-bridge inverter in the second stage. The proposed power conditioner is operated by a selective time-sharing dual-mode pulse pattern signal processing control scheme without electrolytic capacitor dc link. The unique operating principle of the two-power conditioning and processing stages with sectional time-sharing dual-mode partial sinewave-modulation scheme is described and discussed with a design example. In addition, this paper proposes also a sinewave tracking voltage controlled soft switching pulsewidth-modulation boost chopper with a bypass-diode loop, which includes a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the control implementation of this novel power conditioner are presented and evaluated through experimental and simulation results

Utility AC interfaced soft-switching sinewave PWM power conditioner with two-switch flyback high-frequency transformer

High-frequency switching pulse modulation utility-interfaced power conditioners (HF-UPC) with a high-frequency transformer link have attracted special interest for renewable and sustainable energy utilisation. These conditioners are small and cost-effective for meeting the requirements of small-scale residential power applications. However, switching power losses due to high-frequency switching operations are unavoidable. Efforts to reduce the power losses by implementing additional snubber components can complicate the controlling methods of the system. To solve these problems, a flyback transformer linked HF-UPC is proposed. The high-frequency flyback transformer is introduced into the power conditioner system instead of the typical forward transformer to simplify the circuit configuration and related controlling methods. With the aid of the resonant snubber circuits, the high-frequency switching devices in the primary side of the proposed DC-to-AC power conditioner can be turned off with zero-voltage soft-switching (ZVS). In addition, the proposed power conditioner system takes advantage of operating the currents by the discontinuous conduction mode (DCM) to realise turn-on commutation of zero-current soft-switching schemes. The output ports of the HF-UPC treated here are directly connected to the utility grid single-phase AC power source. A prototype of the proposed soft-commutation HF-UPC has been built and tested in experiments. Its power conversion processing is verified and its output current is qualified in accordance with the guidelines of the power utility companies.

系統連系高周波2石フライバックトランス絶縁方式ソフトスイッチングPWM正弦波インバータ

This paper presents two novel prototypes of the utility AC power source connected sinewave inverter using the high-frequency two-switch flyback transformer which is more suitable and acceptable for the small-scale solar photovoltaic and fuel cell generator interfaced power conditioners. The proposed sinewave soft-switching PWM power conditioner with a high-frequency AC link has a function of electrical isolation including sinewave hard-switching PWM power conditioner with a high frequency link, which is considered for solar photovoltaic power conditioner and fuel cell generator related power conditioner from the viewpoints of safety and reliability in total system. The discontinuous conduction mode (DCM) operation of the flyback transformer in this circuit system is also introduced to feature a simple, low-cost and high-efficiency topology of the sinewave inverter circuit and digital control implementation. The operating principle of the proposed sinewave soft-switching PWM inverter circuit as compared with sinewave hard-switching PWM inverter are described for the designing of circuit parameters. Moreover, the digitally controlled sinewave PWM control processing scheme is presented herein. Finally, the sinewave soft-switching PWM inverter prototype is actually built and tested to verify the validity of the proposed power conditioner for new energy generation systems.

Utility-Interactive Flyback Transformer Linked Soft-Switching Inverter for Renewal Energy System

This paper presents a novel prototype of utility-interactive soft-switching inverter using high-frequency flyback transformer. The proposed power conditioner circuit has an isolation function, which is cost effective and reliable for small-scale distributed renewal energy system. The discontinuous current mode (DCM) is applied to configure simple circuit and control. The operation principle is described on the basis of simulation evaluations. It is proved that the inverter outputs sinusoidal and unity power factor current synchronized with mains voltage.