Novel bidirectional universal 1-phase/3-phase-input unity power factor differential AC/DC converter

A common 400 V dc bus for industrial motor drives advantageously allows the use of high-performance 600 V power semiconductor technology in the inverter drive converter stages and to lower the rated power of the supplying rectifier system. Ideally, this supplying rectifier system features unity power factor operation, bidirectional power flow and nominal power operation in the three-phase and the single-phase grid. This paper introduces a novel bidirectional universal single-/three-phase-input unity power factor differential ac-dc converter suitable for the above mentioned requirements. The basic operating principle and conduction states of the proposed topology are derived and discussed in detail. Then, the main power component voltage and current stresses are determined and simulation results in PLECS are provided. The concept is verified by means of experimental measurements conducted in both three-phase and single-phase operation with a 6 kW prototype system employing a switching frequency of 100 kHz and 1200 V SiC power semiconductor

A Simplified Hard-Switching Loss Model for Fast-Switching Three-Level T-Type SiC Bridge-Legs

Hard-switching losses in three-level T-type (3LTT) bridge-legs cannot be directly estimated from datasheet energy loss curves, which are given for symmetric two-level half-bridge configurations only. The commutations in a 3LTT bridge-leg occur between semiconductors with different blocking voltages and/or current ratings, and involve a third semiconductor device in the switching transition, which contributes additional capacitive losses. This paper, therefore, describes a simplifed approach to estimate a lower bound for the hard-switching losses of 3LTT bridge-legs (note that the approach is applicable to other three-level topolgies as well). In view of the very fast switching speeds of wide-bandgap semiconductors, the model neglects voltage/current overlap losses and considers only the dominating charge-related loss contributions (semiconductor output capacitances, body diode reverse-recovery charge), thus requiring minimal information from datasheets. A direct experimental verification with an 800 V DC-link 3LTT bridge-leg (1200 V and 650 V SiC MOSFETs) operating with output currents up to 25 A confirms the good accuracy of the simplified switching-loss model

Bidirectional AC DC Converter for Regenerative Braking

In this paper, a bidirectional AC DC converter is analyzed. The converter applies a half bridge thyristor rectifier and a recuperating thyristor bridge instead of a braking resistor. Recuperating mode of the converter is focused in the analysis, and it is shown that the converter exposes two operating modes within the recuperating mode, one characterized by negligible, and the other one characterized by significant distortion of the input voltages. Theoretical results are experimentally verified on a 10 kW converter

A Novel Multicell DC-AC Converter for Applications in Renewable Energy Systems

Abstract-This paper presents a novel dc-ac converter for applications in the area of distributed energy generation systems, e.g., solar power systems, fuel-cell power systems in combination with supercapacitor or battery energy storage. The proposed converter is realized using an isolated multicell topology where the total ac output of the system is formed by series connection of several full-bridge converter stages. The dc links of the full bridges are supplied by individual dc-dc isolation stages which are arranged in parallel concerning the dc input of the total system. Therefore, all switching cells of the proposed converter can be equipped with modern low-voltage high-current power MOSFETs, which results in an improved efficiency as compared to conventional isolated dc-ac converters. Furthermore, the cells are operated in an interleaved pulsewidth-modulation mode which, in connection with the low voltage level of each cell, significantly reduces the filtering effort on the ac output of the overall system. The paper describes the operating principle, analyzes the fundamental relationships which are relevant for component selection, and presents a specific circuit design. Finally, measurements taken from a 2-kW laboratory model are presented

Single-Phase Full-Wave Rectifier as an Effective Example to Teach Normalization, Conduction Modes, and Circuit Analysis Methods

Application of a single phase rectifier as an examplein teaching circuit modeling, normalization, operating modesof nonlinear circuits, and circuit analysis methods is proposed.The rectifier supplied from a voltage source by an inductiveimpedance is analyzed in the discontinuous as well as in thecontinuous conduction mode. Completely analytical solution forthe continuous conduction mode is derived. Appropriate numericalmethods are proposed to obtain the circuit waveforms inboth of the operating modes, and to compute the performanceparameters. Source code of the program that performs suchcomputation is provided

Three-Port Series-Resonant DC/DC Converter for Automotive Charging Applications

In the energy distribution grid of electric vehicles (EVs), multiple different voltage potentials need to be interconnected, to allow arbitrary power flow between the various energy sources and the different electrical loads. However, between the different potentials, galvanic isolation is absolutely necessary, either due to safety reasons and/or due to different grounding schemes. This paper presents an isolated three-port DC/DC converter topology, which, in combination with an upstream PFC rectifier, can be used as combined EV charger for interconnecting the single-phase AC mains, the high-voltage (HV) battery and the low-voltage (LV) bus in EVs. The proposed topology comprises two synergetically controlled and magnetically coupled converter parts, namely, a series-resonant converter between the PFC-sided DC-link capacitor and the HV battery, as well as a phase-shifted full-bridge circuit equivalent in the LV port, and is mainly characterized by simplicity in terms of control and circuit complexity. For this converter, a simple soft switching modulation scheme is proposed and comprehensively analyzed, in consideration of all parasitic components of a real converter implementation. Based on this analysis, the design of a 3.6 kW, 500 V/500 V/15 V prototype is discussed, striving for the highest possible power density and as low as possible manufacturing costs, by using PCB-integrated windings for all magnetic components. The hardware demonstrator achieves a measured full-load efficiency in charge mode of 96.5% for nominal operating conditions and a power density of 16.4 kWL−1.ISSN:2079-929