Ji-Woong Gong

Design of high voltage capacitor charger with improved efficiency, power density and reliability

This paper describes the design of a 48 kJ/s high-voltage capacitor charging power supply (CCPS), focusing on its efficiency, power density, and reliability. On the basis of a series-parallel resonant converter (SPRC) that provides high efficiency and high power density owing to its soft-switching, the design of the CCPS is explained in detail, including its input filter, resonant tank parameters, high-voltage transformer and rectifier, as well as its protection circuit. By using two resonances per switching cycle, which provides a trapezoidal instead of a sinusoidal waveform of the resonant current, the proposed CCPS can take advantage of the lower conduction loss and reduced switching loss by improving the crest factor and allowing a higher value of the snubber capacitor, respectively. In addition, the compact design of an input filter without bulky components such as a DC reactor and an electrolytic capacitor allows for high power density, a high power factor, and low cost. In addition, the control loops for the voltage and current were optimized with a fast response time in order to compensate for the low frequency ripple of the input voltage, which results from the reduced filter component. Experiments on the developed charger were carried out with both resistor and capacitor loads in order to measure not only its efficiency and power factor with respect to the output power but also its charging time, in order to estimate the average charging current. The experimental results obtained with a resistor load showed a maximum efficiency of 96% and a power factor of 0.96 for a full-load condition. For the measured charging time of a 4 mF capacitor, with 9.68 s for 10 kV charging, the average charging current was estimated as 4.13 A. Moreover, to verify the reliability of the developed CCPS, a variety of tests, including opening and shorting of the output terminal as well as misfiring of the discharge switch during the charging operation, were performed with a 200 kJ pulsed power system. Finally, it was experimentally confirmed that the developed CCPS shows high performance in terms of efficiency (96 %), power factor (0.96), and reliability with a high power density (820 W/L).

Design and Implementation of Enhanced Resonant Converter for EV Fast Charger

This paper presents a novel application of LCC resonant converter for 60kW EV fast charger and describes development of the high efficiency 60kW EV fast charger. The proposed converter has the advantage of improving the system efficiency especially at the rated load condition because it can reduce the conduction loss by improving the resonance current shape as well as the switching loss by increasing lossless snubber capacitance. Additionally, the simple gate driver circuit suitable for proposed topology is designed. Distinctive features of the proposed converter were analyzed depending on the operation modes and detail design procedure of the 10kW EV fast charger converter module using proposed converter topology were described. The proposed converter and the gate driver were identified through PSpice simulation. The 60kW EV fast charger which generates output voltage ranges from 50V to 500V and maximum 150A of output currents using six parallel operated 10kW converter modules were designed and implemented. Using 60kW fast charger, the charging experiments for three types of high-capacity batteries were performed which have a different charging voltage and current. From the simulation and experimental results, it is verified that the proposed converter topology can be effectively used as main converter topology for EV fast charger.

Low-Ripple and High-Precision High-Voltage DC Power Supply for Pulsed Power Applications

This paper describes the design and implementation of a three-phase resonant converter with low ripple and high control accuracy. Based on a three-phase LCC-type resonant converter-which has advantages of low ripple, highefficiency, and high-power density compared with a single-phase converter-a high-voltage power supply with low ripple (<;0.1%) was designed. In addition to the general merits of an LCC-type resonant converter operating at continuous conduction mode- including soft switching, low conduction loss, and current source characteristics-the proposed scheme uses only one phase under a light-load condition by having different leg designs of the gate drive circuit and snubber parameters. This allows the design to overcome the operational constraints of the general LCC-type resonant converter. The distinctive design of the three-phase converter structure provides high efficiency and low ripple not only during rated operation, but also under light-load conditions. In order to analyze the high performance of the proposed scheme from no load to rated load, a PSPICE simulation was carried out. Comparison results with a conventional LCC-type resonant converter based on a single-phase structure are analyzed from the viewpoints of output ripple, losses, and operable load range. Using the proposed converter, a 20-kV, 20-kW high-voltage dc power supply design and implementation was presented with a superior gate drive circuit. Finally, the superiority of the proposed converter was verified through a simulation and experimental results. It was experimentally confirmed that the developed power supply achieves high performance in terms of efficiency (98%), operable load range (0.5-20 kV), and low ripple (0.05%), with a high power density.

Design and Comparison of Capacitor Chargers for Solid-State Pulsed Power Modulator

This paper describes the design, implementation, and comparison of high-voltage capacitor chargers for a solid-state pulsed power modulator (SSPPM). The three different converter topologies are a series resonant converter operating at a discontinuous conduction mode with switching frequency control (SRC_DCM_SFC), a series resonant converter operating at a continuous conduction mode with phase shifted pulse width modulation control (SRC_CCM_PSPWMC), and a series-parallel resonant converter operating at the CCM with SFC (SPRC_CCM_SFC). On the basis of these converter topologies, 10-kWaverage high-voltage capacitor chargers are designed for the three types of SSPPMs, which have the following maximum output specifications: 1) SRC_DCM_SFC: 60 kV, 300 A, 3 kpps, and 50 μs; 2) SRC_CCM_PSPWMC: 10 kV, 50 A, 50 kpps, and 10 μs; and 3) SPRC_CCM_SFC: 40 kV, 150 A, 7 kpps, and 10 μs. Although the pulse output specifications are different, it is worth comparing the resonant inverter topologies and the control methods from the viewpoint of the losses, control characteristics, and merits and demerits of the high-voltage capacitor chargers. From the analysis and investigation of the three resonant inverters, the design procedure, including the determination of the resonant tank parameters, is provided, which considers the design of the high-voltage capacitor charger. PSPICE simulation is used to elucidate the effects of the resonant tank structure and its parameters, and the resonant current waveform and losses of the Insulated Gate Bipolar Transistor are compared. Finally, experiments for each charger are performed under various load conditions, and the comparison results of the three capacitor chargers, including the conduction and switching losses, control characteristics, and overall efficiency, are discussed in this paper.

Robust Design of a Solid-State Pulsed Power Modulator Based on Modular Stacking Structure

This paper describes the design of a robust high-voltage solid-state pulsed power modulator (SSPPM), which requires reliable series stacking and driving of a number of semiconductor switches. For voltage balancing against overvoltage during both at transient and at steady-state, the power-cell-based modular stacking structure consists of an energy storage capacitor, bypass diode, and switching device (such as an insulated-gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor (mosfet)). In addition to the reliable voltage balancing of each switching device, the modular power cell stacking structure provides a fault-tolerant design by allowing individual protection circuit for each switching device. In this paper, the inclusion of a compensating third winding is proposed. This compensating third winding solves the voltage unbalance issue, which results from difference of leakage inductance of separate located transformer core, using magnetic flux compensation. A protection method using this compensating winding is also suggested to detect abnormal occurrences in each power cell under operating conditions. Additionally, an arc current protection circuit to ensure continuous operation of the SSPPM is designed. Through simulation and experimental results of tests on the SSPPM with the structure outlined earlier, it is verified that the proposed design can be used effectively, as it exhibits both robustness and reliability.

Design and Test of a 35-kJ/s High-Voltage Capacitor Charger Based on a Delta-Connected Three-Phase Resonant Converter

This paper describes the design, implementation, and analysis of a 35 kJ/s high-voltage capacitor charger based on a delta-connected three-phase series resonant converter that provides a constant charging current with high efficiency and high-power density. In order to obtain the maximum output power for various charging voltages, each high-voltage transformer supplied by a delta-connected resonant inverter is designed with two secondary windings and voltage-doubled rectifiers. This configuration allows not only a flexible output current and voltage with fixed output power but also a high power factor on the input side. On the basis of the analysis of the series-loaded resonant converter operating at a discontinuous conduction mode, the details of the design procedure for the resonant inverter are provided. Furthermore, the implementation of the high-voltage transformers and rectifiers is also explained while considering insulation and compactness. Experiments were carried out on the developed charger with different types of capacitors, depending on their applications, and the results are discussed. In addition, malfunctioning tests were conducted for the open, short, and misfiring during charging conditions. Finally, the developed high-voltage capacitor charger was shown to be very reliable, even under faulty operating conditions in the system.

Design and Implementation of a 40-kV, 20-kJ/s Capacitor Charger for Pulsed-Power Application

This paper presents the design and implementation of a 40-kV, 20-kJ/s high-voltage capacitor charger based on a series/parallel resonant converter. The inclusion of the parallel resonant capacitor component in this circuit results in the production of a trapezoidal resonant current, which reduces conduction loss. This capacitor is practically realized as a part of the balancing network of the high-voltage rectifiers in the secondary side of the circuit. Particular attention in this paper is paid to the high-voltage transformer, which must be carefully designed to provide the required functionality without negative impact on the resonant circuit. A PSpice simulation has been used to prove that the proposed control method for the circuit is valid. This is supported with the experimental results, which verify that the operation of the circuit is as expected and that the converter is able to meet all the design criteria with an efficiency of up to 96%.

Implementation of 60-kW fast charging system for electric vehicle

This paper instructs implementation of electric vehicle (EV) fast charging system which complies with the international standard related with EV conductive charging system. Concretely, design issues and the consideration of EV fast charging system components are presented. In view of this, this paper proposes the 60-kW fast charging system which is consists of a master controller communicating with battery managements system (BMS) and EV for safe charging, a smart meter for billing and metering, a charging connector and the output stage formed by six modules of high-efficiency 10kW DC-DC converter for stable output with the input module for passive power factor correction and reducing the ripple of D.C. voltage, The charging system generates output voltage ranges from 50-V to 500-V and maximum output current of 150-A. And, it is tested with a variety of batteries aimed from NEV (Neighborhood Electric Vehicle) to full-speed EV and EV simulator consisted of 20kWh LiFePO2 battery to verify excellent performance as a fast charging system. The developed EV fast charging system is installed at Korean EV test infrastructure and practical charging test with various kinds of EVs has been now performing.

Comparison of DCM and CCM operated resonant converters for high-voltage capacitor charger

This paper describes the comparison of two a resonant converters for high-voltage capacitor charger which were designed based on a series resonant converter operating at a discontinuous conduction mode, and a continuous conduction mode, respectively. In addition to the investigation of general advantages and disadvantages of each topology as a high-voltage capacitor charger, a detailed implementation procedure and consideration depending on the analysis of losses, as well as the control characteristic of two resonant converters are discussed in practical manner. Based on the theoretical calculation and the PSpice simulation, two high-voltage capacitor chargers were developed with design criteria which aim to achieve the efficiency greater than 90% at the rated load operation. Finally, various kinds of experiments were performed and the results were provided in order to verify the design as well as to compare the charging efficiency and characteristics of two resonant converter topologies.

Design of 10kV, 2A high-voltage DC power supply using two stage control

This paper describes the design of a 20 kW (10kV, 2A) DC power supply using two stage control which consists of the silicon controlled rectifier (SCR) for input voltage control and the series-parallel resonant converter (SPRC) for output voltage control. In order to overcome the general constraint of SPRC, the restricted controllable load range with softswitching, the additional stage for adjusting input voltage by controlling the triggering angle of SCR is proposed and it facilitates the wide load range operation of SPRC with maintaining high-efficiency not only light-load but also rated operation. From the analysis of the controllable load range of SPRC with soft-switching, the control methodology of both switching-frequency of resonant inverter and triggering angle of SCR is explained. Based on the proposed control concept, a detailed design of a 20 kW power supply is provided including the PSpice simulation, the high-voltage transformer and the high-voltage rectifier. Finally, the experimental results which were carried out with various kinds of load condition verify the high-performance of proposed two stage control method from the view point of high-efficiency, wide controllable load range, and reliability.