Suk-Ho Ahn

Development and Optimization of High-Voltage Power Supply System for Industrial Magnetron

This paper describes the design and analysis of a 42-kW (14 kV, 3 A) high-voltage power supply for a 30-kW industrial magnetron drive. The design is based on a series resonant converter in discontinuous conduction mode (DCM) to take advantage of both the superior arc protection stemming from the current source characteristics and the high power density owing to the use of parasitic elements such as the leakage inductance in the high-voltage transformer. The detailed design procedure for the resonant tank and high-voltage transformer with respect to the input and output specifications is described on the basis of a simplified analysis of the DCM series resonant converter. Special considerations for designing high-power high-voltage power supplies are provided, such as series stacking of diodes for a voltage doubling rectifier and insulation between each winding of the high-voltage transformer. In addition, a comparative study using theoretical equations, simulation, and experimental results was carried out. This study yielded the output voltage and current characteristics at different switching frequencies and verified the advantages of this topology, such as arc protection without an additional protection circuit and high efficiency due to zero-current or zero-voltage switching. Moreover, the parallel operation of two converters with phase shifted gating signal is proposed to reduce the output current ripple and increase power capability for higher power magnetron drive. Additionally, the design considerations of two auxiliary power supplies (a filament power supply: 15 V, 150 A and a magnet power supply: 50 V, 5 A) are also provided and optimized for effective driving industrial magnetron. Finally, the developed power supply was tested with a 30-kW industrial magnetron, and the results prove the reliability and robustness of the proposed scheme.

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 of a High-Efficiency 40-kV, 150-A, 3-kHz Solid-State Pulsed Power Modulator

This paper deals with the detailed design of a pulsed power modulator using insulated gate bipolar transistor (IGBT) switches for industrial applications. Output specifications of the proposed modulator are as follows: variable output pulse voltage 1~40 kV; pulse width 0.5~5 μs ; maximum pulse repetition rates 3 kHz, and average output power of 13 kW. The proposed pulsed power modulator consists of a high-voltage capacitor charger based on a high-efficiency resonant inverter and pulse generator part including a series of connected 24 pieces power cells. To verify the proposed design, PSpice modeling was performed. Finally, experimental results proved the reliability and robustness of the proposed solid-state pulsed power modulator.

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.

A comparative study of the gate driver circuits for series stacking of semiconductor switches

For the high voltage semiconductor switch based pulsed power application, series operation of semiconductor switches is generally required because of limitation of device ratings. However, there are many considerations to design gate driver circuit for stacking the IGBTs because of the complexity and difficulty of synchronization and protection. Gate driver circuit of series connected IGBTs usually requires high number of high voltage insulated gate power source and complex gate signal schemes depending on the total number of switches. Furthermore, since it is difficult to synchronize switching operations, complex protection circuit should be employed to protect semiconductors switches from arc or short circuit condition which is frequently generated during normal operation of pulsed power application. The purpose of this study is the introducing of the simple and reliable gate driver circuits for series connected semiconductor switches based on the expected problems and considerations. The advantages of each driver circuit are analyzed based on comparative study of proposed gate driver circuits with PSpice simulation. By combining driver circuit with 12 series connected IGBT stack for 10kV pulsed modulator, the various kinds of testing were performed including normal operation and arc or short condition. The experimental results is confirmed that proposed gate driver circuit can be effectively used at semiconductor based pulsed power modulator.

Design and analysis of series resonant converter for 30kW industrial magnetron

This paper deals with the design and analysis of 42kW (14kV, 3A) high voltage power supply for 30kW industrial magnetron. The developed high voltage power supply was designed based on the series resonant converter discontinuous conduction mode (DCM) to takes advantage of the superior arc protection because of their current source characteristic. The detail design procedure for resonant tank and high voltage transformer with respect to the input and output specifications is described based on the basic analysis of DCM series resonant converter. A comparative study with theoretical equations, simulation and experimental results was given. It provides the output voltage and current characteristics with variable switching frequency and verifies the advantage of this topology such as the function of arc protection without any additional protection circuit and high efficiency because of the zero current or zero voltage switching. Also, the developed power supply was tested with 30kW magnetron and the results prove the reliability and robustness of proposed scheme.

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.

Design of LCC resonant converter for renewable energy systems with wide-range input voltage

This paper deals with the design of a 21 kW series-parallel resonant converter, that is, LCC resonant converter that can be effectively used for intermediate power conversion from renewable energy sources to a battery energy storage system. The developed LCC resonant converter was made of a high-frequency transformer and a relatively high parallel capacitance for voltage boosting in order to cover a wide range of input voltage (200 - 400 V) with high-efficiency. Furthermore, the optimized design of resonant tank parameters described in this paper helped reduce or make negligible the turn-off loss of insulated gate bipolar transistors by increasing the lossless snubber capacitance. In this paper, the detailed design of the proposed converter, including the selection of the snubber capacitor and the determination of transformer turns ratio on the basis of the converter specifications, is described along with operational mode analysis and PSpice simulation. In addition, a simple structure of a controller for a battery charging application that requires both constant current and constant voltage control is described. A gate driving method for zero voltage switching was introduced to compensate the difference of snubber capacitor discharging time. Finally, the developed LCC resonant converter was tested with a resistive load, and the results showed a maximum efficiency higher than 90% in the input voltage range of 200-400 V. A long duration operation test was conducted to verify the reliability and robustness of the designed converter.

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.