A three-phase three-switch buck-type pulsewidth modulation rectifier is designed for telecom applications in this paper. The rectifier features a constant 400-V output voltage and 5-kW output power at the three-phase 400-V mains. The principle of operation and the calculation of the relative on-times of the power transistors are described. Based on analytical relationships the stresses of the active and passive components are determined and the accuracy of the given calculations is verified by digital simulations. Exemplarily, a 5-kW power converter is then designed based on the analytical expressions and on switching loss measurements from a hardware prototype constructed with insulated gate bipolar transistor/diode power modules. The loss distribution of the components, the total efficiency, and the junction temperatures of the semiconductors are then evaluated in dependency on the operating point. Finally, the trade-off between the selected switching frequency and the admissible power range for the realized design is shown and a total efficiency of 95.0% is measured on the hardware prototype, where an excellent agreement with the theoretically evaluated efficiency is shown

Comprehensive Design of a Three-Phase Three-Switch Buck-Type PWM Rectifier

A robust 12 kW rectifier with low THD in the line currents, based on an 18-pulse transformer arrangement with reduced kVA capacities followed by a high-frequency isolation stage is presented in this work. Three full-bridge (buck-based) converters are used to allow galvanic isolation and to balance the dc-link currents, without current sensing or current controller. The topology provides a regulated dc output with a very simple and well-known control strategy and natural three-phase power factor correction. The phase-shift PWM technique, with zero-voltage switching is used for the high-frequency dc-dc stage. Analytical results from Fourier analysis of winding currents and the vector diagram of winding voltages are presented. Experimental results from a 12 kW prototype are shown in the paper to verify the efficiency, robustness and simplicity of the command circuitry to the proposed concept.

A 12 kW three-phase low THD rectifier with high-frequency isolation and regulated DC output

This paper proposes an H7 current source inverter (CSI) consisting of a single shunt-connected silicon carbide (SiC) switch and a traditional silicon H6 CSI circuitry, which could employ the superior characteristics of SiC switch to significantly increase the whole switching frequency with expected low losses simultaneously. In order to reduce the switching counts and also realize the zero-current switching (ZCS) ability for rear-end CSI circuitry, two kinds of H7 CSI modulation schemes have been proposed with either superior output performance or minimal switching counts. Consequently, the proposed H7 CSI can perform as an all-SiC-switch circuitry, and guarantee high performance and high efficiency with a reduced dc inductance. It could be a cost-effective solution to address the efficiency issue of CSIs. MATLAB simulations and experimental verifications have been presented in order to show the performance of the proposed inverter.

Operation and Modulation of H7 Current-Source Inverter With Hybrid SiC and Si Semiconductor Switches

To make downstream dc-dc converters compatible with both single and three phases PFC stages for system integration, a novel three-level full bridge resonant dc-dc converter was proposed. This converter combines the LLC topology, which maintains merits as ZVS for all primary side main switches and ZCS for secondary side diodes under wide range inputs, and the three-level technique, which is suitable for high voltage input applications, together. In addition, full bridge configuration endows the high power capability to the proposed converter. The detail operation principles, as well as the design considerations and loss calculation, were presented. The validity and applicability were also verified by a 1kW prototype, while the maximum efficiency reaches 96.2%. Therefore, the proposed converter is very attractive for the system integration applications which have requirement to be compatible with 400V and 800V PFC systems, while high power capability must be taken into account. Consequently, it is of practical significance for industry to simplify power supply's variety and lower cost.

A Novel Three Level Full Bridge Resonant Dc-Dc Converter Suitable for High Power Wide Range Input Applications

This paper presents a matrix-based nonisolated three-phase ac–dc converter with a current-doubler rectifier (CDR) circuit. Buck-type rectifiers are normally used for step-down ac-to-dc conversion. However, for three-phase buck rectifiers, the lower bound of rectified dc voltage is limited as the converter is severely underutilized by operating at lower modulation index. Moreover, at lower modulation index, the rms values of current increases contributing to higher conduction losses. However, by using a matrix (3 × 1) topology followed by a CDR, the desired dc output voltage can be reduced by half. The matrix topology directly converts three-phase line frequency ac voltages into intermediate high-frequency ac voltage which is subsequently, rectified using a CDR to obtain the required output dc voltage. A modified space vector modulation based modulation scheme especially suited for the proposed converter is presented for superior input power quality with reduced power loss. Comprehensive analysis and design of the proposed converter is carried out followed by simulation and laboratory-based experimental tests. Subsequently, the loss analysis of the proposed converter is carried out and a comparative evaluation of the proposed converter with the traditional six-switch buck rectifier is provided to demonstrate the suitability of the proposed converter for large step-down voltage gain. Digital implementation of the proposed modulation scheme is carried out at 40-kHz switching frequency. A hardware prototype of 500 W is developed to validate the theoretical and simulation results.

A Matrix-Based Nonisolated Three-Phase AC–DC Rectifier With Large Step-Down Voltage Gain

A new 3-phase-bridge PWM current-source-type (CST) (or buck-mode) PFC rectifier for telecommunications energy systems is introduced. The necessity, the advantages and disadvantages of this type PWM rectifier in the application are discussed. Then, a new power circuit topology and modulation scheme to eliminate or mitigate the disadvantages and obtain further new advantages of the PWM-current-source-type PFC rectifier are introduced. The features of the new rectifier obtained by the new PWM scheme have been confirmed through experimental results obtained from a 12 kW real product. Furthermore, variation of the efficiency and total-harmonic-distortion of the input line current for several DC-inductor arrangements are evaluated.

T. Kondoh

Papers

Three-phase PWM-current-source type PFC rectifier (theory and practical evaluation of 12kW real product)