Special Issue

Special Issue on Switched-Capacitor Circuits and Partial Processing Techniques



Guest Editors: Don Tan, IEEE Fellow(Northrop Grumman Aerospace Systems, USA)

                       Yan-Fei Liu, IEEE Fellow(Queen's University, Canada)

                       Xinbo Ruan, IEEE Fellow(Nanjing University of Aeronautics and Astronautics, China)

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Editorial for the Special Issue on Switched-Capacitor Circuits and Partial Processing Techniques Chinese Journal of Electrical Engineering    2020, 6 (4): 1-2.   DOI: 10.23919/CJEE.2020.000025 Abstract （295）      PDF       Knowledge map    Related Articles | Metrics

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A Novel Intermediate Bus Converter Topology for Cutting Edge Data Center Applications Samuel Webb, Yan-Fei Liu Chinese Journal of Electrical Engineering    2020, 6 (4): 3-14.   DOI: 10.23919/CJEE.2020.000026 Abstract （399）      PDF       Knowledge map    As new technologies emerge data centers and servers have established themselves as one of the largest and fastest growing consumers of power. While switched capacitor converter topologies have some very attractive features, namely low reliance on magnetic components and high efficiency, several critical factors have prevented their adoption in high current data center applications. The family of converters proposed are novel intermediate bus converter that demonstrates the highest performance yet achieved for 48 V to 12 V conversion with up to 2.5 kW/in3 power density, higher than 99% peak efficiency, and 97.2% full load efficiency for 12 V/70 A output. The reduction of voltage stress across the MOSFETs as well as extremely low reliance on magnetics are the key driving factors behind this high efficiency and power density, and are achieved without a sensitive resonant design or the usage of complex control technique. Reference | Related Articles | Metrics

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A Double Input-parallel-output-series Hybrid Switched-capacitor Boost Converter Jianfei Chen, Kewei Ding, Yulin Zhong, Fujin Deng, Sayed Abulanwar Chinese Journal of Electrical Engineering    2020, 6 (4): 15-27.   DOI: 10.23919/CJEE.2020.000027 Abstract （325）      PDF       Knowledge map    A double input-parallel-output-series hybrid switched-capacitor boost (DIPOS-HSCB) converter is proposed which consists of two different kinds of input-parallel-output-series (IPOS) circuits, i.e., inner IPOS circuit and outer IPOS circuit. Two boost modules and one switched-capacitor network build an inner IPOS circuit based IPOS-HSCB converter and two IPOS-HSCB converters develop the outer IPOS circuit based DIPOS-HSCB converter. With the proposed DIPOS-HSCB converter, a high voltage-gain with low component stress and small input current ripple are achieved. Furthermore, an automatic current balancing function for all input inductor currents can be also achieved using a special carrier phase-shifted modulation scheme. A prototype rated at 200 V/120 W has been developed and the maximum efficiency of the proposed DIPOS-HSCB converter is 95% at 120 W. Both steady and dynamic results are presented to validate the effectiveness of the proposed DIPOS-HSCB converter. Reference | Related Articles | Metrics

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Flying Capacitor Design Considerations for a 48-to-12 V, 35 A Split-phase Dickson SC Converter RichardSun, Samuel Webb, Yan-Fei Liu Chinese Journal of Electrical Engineering    2020, 6 (4): 28-41.   DOI: 10.23919/CJEE.2020.000028 Abstract （290）      PDF       Knowledge map    Switched-capacitor converters can deliver better performance, power density, and switch utilization compared to inductor-based power converters, but they suffer from current spikes during switching due to capacitor charge redistribution. This can be solved by methods such as split-phase control, which was developed to address charge redistribution in Dickson SC converters by controlling the charging and discharging of the circuit's flying capacitors, such that the equivalent branch voltages line up when the circuit switches states. However, split-phase control is most effective at compensating for charge redistribution when all the circuit's flying capacitors are matched in capacitance value. Differences between the capacitance values of the circuit flying capacitors may result in split-phase control not being able to fully compensate for charge redistribution, due to the different charge/discharge rates of the flying capacitors. The work presented in this paper provides an in-depth analysis of the sensitivity of the split-phase Dickson converter to mismatches in flying capacitor values, as well as discussions regarding the design considerations and prototype test results of a split-phase Dickson converter for high-current loads. Reference | Related Articles | Metrics

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Switched-capacitor Multi-level Inverter with Equal Distribution of the Capacitors Discharging Phases* Zhiyuan Xu, Xiaofeng Zheng, Tong Lin, Jia Yao, Adrian Ioinovici Chinese Journal of Electrical Engineering    2020, 6 (4): 42-52.   DOI: 10.23919/CJEE.2020.000029 Abstract （302）      PDF       Knowledge map    A new switched-capacitor (2n+1) levels inverter with a single input source and equal charge of the capacitors at the input voltage Vin is presented. Compared with its peers from the same class of inverters, the proposed one features an equal or lower components count referred to the boost factor. And, it presents an additional advantage: each voltage level can be obtained by using different capacitors in the discharging phase, such that the decreasing part of the staircase output waveform can be synthesized with different switching topologies than those used in the increasing part. As a consequence, all the capacitors are discharged at the same voltage value at the end of each half-cycle, allowing for the use of smaller capacitors of equal values. When the capacitors are connected in parallel in the charging phase, there is no need to equalize their voltages, so no additional current spikes appear. This also implies less electromagnetic emission (EMI). Two types of modulation strategies are proposed. A half-height fundamental switching frequency modulation strategy allows for reaching the desired peak of the output voltage during the highest voltage level operation. It is advantageous in application of the inverter as a front end of a grid supplied by green sources of energy. A high frequency (fs=200 kHz) modulation strategy accompanied by a duty-cycle control is advantageous for applications which require miniaturization. A 9-level switched-capacitor multi-level inverter (SCMLI) is analyzed and designed. The power losses are calculated. The experimental results for a 9-level inverter with Vin=40 V, Vout=110 Vrms 50 Hz, 200 W confirm the theoretical expectations. Reference | Related Articles | Metrics

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Fast Online Diagnosis of Open-circuit Switching Faults in Flying Capacitor Multilevel Inverters Majid T. Fard, Waqar A. Khan, Jiangbiao He, Nathan Weise, Mostafa Abarzadeh Chinese Journal of Electrical Engineering    2020, 6 (4): 53-62.   DOI: 10.23919/CJEE.2020.000030 Abstract （406）      PDF       Knowledge map    Flying capacitor multilevel (FCML) inverter is an attractive power converter topology which provides high-quality staircase output voltage waveforms by cascading flying capacitor cells. However, the large number of semiconductor devices utilized in the FCML inverters degrades the hardware reliability, which may constrain such converters from being applied in safety-critical applications. Targeting at open-circuit switching faults, a fast online fault diagnostic method for FCML inverters is presented. Conventional phase-shifted PWM (PSPWM), which can naturally balance the voltage across flying capacitors, is used as the modulation method in this work. Hence, to retain the simplicity feature of the PSPWM, the proposed diagnostic method is developed so that it does not require any voltage measurements of flying capacitors. Only the output AC voltage and current data along with the switching PWM signals from the microcontroller are needed to detect an open-circuit switching fault, and all such sensory data is typically available in the inverter, requiring no additional sensors or hardware for the implementation of this diagnostic method. The detection process takes 5% of the fundamental period of the inverter output signals to diagnose the faulty switch. Simulation and experimental results are presented to verify the effectiveness of the proposed diagnostic method. Reference | Related Articles | Metrics

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Si/SiC Hybrid 5-level Active NPC Inverter for Electric Aircraft Propulsion Drive Applications Majid T. Fard, Mostafa Abarzadeh, Kiavash A. Noghani, Jiangbiao He, Kamal Al-Haddad Chinese Journal of Electrical Engineering    2020, 6 (4): 63-76.   DOI: 10.23919/CJEE.2020.000031 Abstract （502）      PDF       Knowledge map    Medium voltage DC(MVDC) system is considered as a promising technology to improve the efficiency and power density of electric aircraft propulsion(EAP) drives. To adapt to the MVDC voltage level and achieve high drive performance, a five-level active neutral point clamped(5L-ANPC) inverter consisting of three-level ANPC and flying capacitor circuits is investigated, which possesses higher voltage capability, lower output harmonics, as well as mitigated dv/dt and common-mode voltage. To fulfill the requirements of high-speed operation and pursue further enhanced efficiency and power density of the inverter for the next-generation EAP drives, Silicon Carbide(SiC) semiconductor devices are considered for implementing the 5L-ANPC inverter. However, the large commutation loops associated with certain switching states of the inverter lessen the benefits of configuring all the switches as SiC devices. As a result, a hybrid Si/SiC 5L-ANPC inverter is developed with a synchronous optimal pulse(SOP) width modulation strategy for controlling the switches in cell 2 and finite-control-set model predictive controller(FCS-MPC) for those in cell 3 of the inverter. Consequently, in the proposed topology, the SiC devices are merely used for the high-frequency switches in cell 3 and the rest of the low-frequency switches are configured with Si IGBTs. This Si/SiC hybrid ANPC inverter concurrently provides high efficiency and low implementation cost at high-speed operation mode. Simulation and experimental results are provided to verify the effectiveness of the proposed hybrid inverter. Reference | Related Articles | Metrics

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Partial Charging of Capacitors for Improving Voltage Profiles of CSI Fed Motor Drives* Zheng Wang, Yang Xu Chinese Journal of Electrical Engineering    2020, 6 (4): 77-85.   DOI: 10.23919/CJEE.2020.000032 Abstract （309）      PDF       Knowledge map    The fast switching behaviors of wide bandgap devices bring some challenges such as high du/dt and limited short-circuit current withstand capability to the reliable operation of the motor drives. The current-source-inverter (CSI) provides a promising solution in mitigating those challenges by owning the DC-link choke, the reverse-voltage blocking switches and AC commutation capacitors. To further reduce du/dt on switches of CSI fed motor drives, the technique of partial charging of capacitors have been investigated in this paper. By designing the series-connected and the parallel-connected partial-charging circuit for capacitors in DC-link, the voltage profile of CSI could be improved. Specifically, the zero-voltage-switching (ZVS) is achieved for main power switches, the du/dt is reduced and the overvoltage protection is presented. The working mechanism of the technique of partial charging of capacitor is described and one example is discussed on the dual three-phase motor drive. The experimental verification is presented to show the performance of partial charging technique for improving voltage profile of CSI fed motor drives. Reference | Related Articles | Metrics