High Power Electronic Converters Research Articles

Power flow and reliability analysis of a non-isolated PV/grid connected quasi resonant converter for off-board EV charging station

ABSTRACT Growing awareness of greenhouse gas emissions and exhaustion of fossil fuels leads to the adoption of electric vehicles (EVs). However, the major limitations with respect to EV technology are the driving range and charging time. Also, the proliferation of EVs overloads the power grid and paves the way of incorporating renewable energy sources and energy storage devices. The use of multiple sources necessitates the deployment of compact, low-cost, and high-power electronic converters. This paper proposes a novel configuration of a Multi-Source Non-Isolated Quasi-Resonant Converter (MSNQRC) to overcome the limitations in the charging infrastructure. Due to the presence of a quasi-resonant network, the proposed MSNQRC with a single switch can achieve high voltage gain even at low-duty cycles, provide continuous current and low voltage stress. In addition, this paper elaborates on the parametric design of the converter along with PV modeling based on load ratings and the reliability research of MSNQRC by analysing component failures. A prototype model of 300W is built to verify the efficacy of the designed converter model. The results thus obtained validate the designed model and prove that the proposed system can be used for off-board battery charging systems.

Design Issues of Redundant Protection and Supervision System for the Special Purpose Power Converters

This paper addresses problems related to the design and implementation of a fault detection and protection system for high-voltage (HV) NPT IGBT-based converters. An isolated half-bridge power converter topology is investigated, which seems to be very attractive for the high-power electronic converters due to its overall simplicity, small component count and low realization costs. This converter is to be applied in rolling stock with its demanding reliability and safety requirements. Clearly, the robust control and protection system is essential.

Message from editors

Power electronics is a key technology that enables the revolution of electric power generation, transmission, and distribution in modern power systems for improved energy security, efficiency, and sustainability. In distribution systems, power electronic converters not only serve as the critical interfaces between the utility grid and distributed energy resources such as solar, wind, and energy storage, but also play a pivotal role in power quality control and management. In transmission systems, high voltage high power electronic converters are the ideal candidate for achieving flexible and efficient power flow in bulk interconnected power systems. On one hand, it is no doubt that more electronic apparatus will be integrated into future power systems to further reduce carbon emissions. On the other hand, power electronic converters exhibit significantly different characteristics with traditional power system components and may bring a number of challenging stability issues from both converter-level and system-level perspectives. The knowledge and theories for understanding and analysis of more electronics power systems are still lacking and deserve in-depth studies.

Water cold plates for high power converters: A software tool for easy optimized design

This work proposes a SPICE-CFD/FEM based methodology for an optimized design of water heatsinks for high power electronic converters. Cold plates are a key issue for power electronics systems, in order to obtain reliable applications. Often the design of custom heatsinks is done by manual procedures, which require the fabrication of several prototypes. On the other hand, CFD + FEM analysis is a powerful tool to design optimized cold plates, but it requires skilled technicians and long simulation studies.In this paper a SPICE based methodology, with negligible simulation cost and limited use of CFD + FEM simulations and prototypes, is demonstrated to be adequate to design cold plates with the lowest thermal resistance and the lowest surface temperature gradient.A prototype made with the proposed methodology was used to validate the approach. Results show a good agreement between cold plate thermal-fluid dynamic 3D numerical simulations and the SPICE based methodology.A software tool was developed to easily exploit the proposed methodology in customized design of cold plates for any specific application, and to extract necessary data for the datasheet: pressure drop, and thermal resistance.

Selective harmonic mitigation‐pulse‐width modulation technique with variable DC‐link voltages in single and three‐phase cascaded H‐bridge inverters

There are different modulation techniques that can be used in medium-voltage and high-power electronic converters, but a few of them provide high efficiency and satisfy power quality requirements. This study presents a modified selective harmonic mitigation pulse-width modulation (SHM-PWM) technique which employs variable DC-link voltages as a degree of freedom in cascaded H-bridge (CHB) inverters. This degree of freedom increases the range of acceptable modulation indices, reduces the number of switching transitions and increases the number of harmonics that can be removed in selective harmonic elimination (SHE) (or SHM) techniques. Hence, in addition to efficiency improvement, a huge number of harmonics can be mitigated in AC side of the converter. Using this approach, triplen harmonics can be restricted to standard limits, in single-phase inverters. In addition, the proposed SHM-PWM approach employs the least number of switching transitions in a fundamental period to limit the specific number of harmonics compared to the alternative SHE or SHM techniques. In this study, the requirements of two well-known grid codes EN 50160 and CIGRE WG 36-05 are well satisfied and the validity of proposed method is verified by several simulations and experiments on a seven-level CHB inverter in single-phase and three-phase operating modes.

Measurement of the Loop Gain Frequency Response of Digitally Controlled Power Converters

The study of the loop gain frequency response in a power converter is a powerful tool commonly used for the design of the controllers used in the control stage. As the control of medium- and high-power electronic converters is usually performed digitally, it is useful to find a method to measure the digital loop gains. The purpose of this paper is to present a method for properly measuring the loop gain frequency response of digitally controlled power converters by means of an analog frequency response analyzer (FRA). An analog sinusoidal reference signal generated by the FRA is injected through an analog-to-digital converter into the digital controller, and added to the discrete feedback signal. To obtain the frequency response of the open-loop gain, both feedback and disturbed feedback signals are sent back to the FRA by using the pulsewidth modulation peripherals of the controller.

Effects of High Power Electronics Converters on PLC Signals

The harmonics are generated by the switching operation of large power converters, such as Static Compensator (STATCOM), Static Reactive Power Controller (SVC) and UPFC. These harmonics may cover a wide range of frequencies and it can cause problems of interference with communication systems. Power Line Carrier (PLC) system is one of the systems used in transmission of signals for Tele-potations, Tele-tripping, Tele-control and speech communications. The Signal to Noise Ratio (SNR) of the PLC is based on the noise level at the input of the carrier receiver. These effects of harmonics result in overheating, extra losses in electric machines and capacitors; and over voltage due to excited resonance in the power system. The main source of disturbances resulting from harmonics has been proved to be from a high power converter. This problem becomes more complicated when harmonics are originating in many single source. These harmonics can be propagated throughout the entire interconnected power network. The interference due to large power converter will be superimposed on the background noise at lower levels causing it to reduce the SNR to an unacceptable value. This study deals with the analysis of the waveform of the converters and the methods used to reduce the noise imposed on PLC communication signal. © 2006 Asian Network for Scientific Information.

Use of opposition method in the test of high-power electronic converters

The test and the characterization of medium or high-power electronic converters, under nominal operating conditions, are made difficult by the requirement of high-power electrical source and load. In addition, the energy lost during the test may be very significant. The opposition method, which consists of an association of two identical converters supplied by the same source, one operating as a generator, the other as a receptor, can be a better way to do these test. Another advantage is the possibility to realize accurate measurements of the different losses in the converters under test. In the first part of this paper, the characteristics of the method concerning loss measurements are compared to those of the electrical or calorimetric methods, then it is shown how it can be applied to different types of power electronic converters, choppers, switched mode power supplies, and pulsewidth modulation inverters. In the second part, different examples of studies conducted by the authors, and using this method, are presented. They have varying goals, from the test of soft-switching inverters to the characterization of integrated gate-commutated thyristor (IGCT) devices mounted into 2-MW choppers.