Showing items 1 - 20 of 36

A compact design for a switchable wireless charger

- Wang, H., Cheng, K., Hu, Jiefeng

  • Authors: Wang, H. , Cheng, K. , Hu, Jiefeng
  • Date: 2020
  • Type: Text , Conference paper
  • Relation: 8th International Conference on Power Electronics Systems and Applications, PESA 2020, Hong Kong 7 to 10 December 2020, 2020 8th International Conference on Power Electronics Systems and Applications: Future Mobility and Future Power Transfer, PESA 2020
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  • Description: With the continuous miniaturization of electronic products, the compact structure of wireless power transfer (WPT) is extraordinarily necessary for consumer electronics. In addition, to meet the need in charging, load independent output current (CC) and constant output voltage (CV) are supposed to be taken into consideration since it is regarded as one of the most popular methods for charging batteries. This paper studies a switchable and compact design for a wireless charger. The compensation network can be changed between double LCL topology and LCL-S topology. Configurable CC and CV outputs can be achieved by adopting two switches without utilizing sophisticated control loops or any communication between the transmitter and the receiver. Compared with LCC compensation networks, the proposed special structure can save components under both double LCL and LCL-S conditions. The ferrite cores naturally take the responsibility as magnetic shielding for unwanted couplings in a such compact structure. This special design not only greatly alleviates the cross-coupling phenomenon but surely makes the compensation networks design straightforward as well. Ultimately, the fundamental analysis, the related mathematical derivation, detailed circuit topologies, switchable compensation designs and the experimental platform are all discussed and investigated. The proposed design is also analyzed and validated by experimental tests under different charging conditions. © 2020 IEEE.

A fault-tolerant cascaded switched-capacitor multilevel inverter for domestic applications in smart grids

- Akbari, Ehsan, Teimouri, Ali, Saki, Mojtaba, Rezaei, Mohammad, Hu, Jiefeng, Band, Shahab, Pai, Hao-Ting, Mosavi, Amir

  • Authors: Akbari, Ehsan , Teimouri, Ali , Saki, Mojtaba , Rezaei, Mohammad , Hu, Jiefeng , Band, Shahab , Pai, Hao-Ting , Mosavi, Amir
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Access Vol. 10, no. (2022), p. 110590-110602
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  • Description: Cascaded multilevel inverters (MLIs) generate an output voltage using series-connected power modules that employ standard configurations of low-voltage components. Each module may employ one or more switched capacitors to double or quadruple its input voltage. The higher number of switched capacitors and semiconductor switches in MLIs compared to conventional two-level inverters has led to concerns about overall system reliability. A fault-tolerant design can mitigate this reliability issue. If one part of the system fails, the MLI can continue its planned operation at a reduced level rather than the entire system failing, which makes the fault tolerance of the MLI particularly important. In this paper, a novel fault location technique is presented that leads to a significant reduction in fault location detection time based on the reliability priority of the components of the proposed fault-tolerant switched capacitor cascaded MLI (CSCMLI). The main contribution of this paper is to reduce the number of MLI switches under fault conditions while operating at lower levels. The fault-tolerant inverter requires fewer switches at higher reliability, and the comparison with similar MLIs shows a faster dynamic response of fault detection and reduced fault location detection time. The experimental results confirm the effectiveness of the presented methods applied in the CSCMLI. Also, all experimental data including processor code, schematic, PCB, and video of CSCMLI operation are attached. © 2013 IEEE.

A holistic power management strategy of microgrids based on model predictive control and particle swarm optimization

- Shan, Yinghao, Hu, Jiefeng, Liu, Huashan

  • Authors: Shan, Yinghao , Hu, Jiefeng , Liu, Huashan
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industrial Informatics Vol. 18, no. 8 (2022), p. 5115-5126
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  • Description: Power control and optimization are both crucial for the proper operation of a microgrid. However, in existing research, they are usually studied separately. Active and reactive powers are either maintained to constant values at device level or optimized at system level without considering frequency and voltage control of distributed converters. In this article, a holistic power control and optimization strategy is proposed for microgrids. Specifically, a model predictive control incorporated with the droop method is developed at device level to achieve load sharing and flexible power dispatching among distributed energy resources, which is feasible for both islanded and grid-connected modes. In addition, an evolutionary particle swarm optimization algorithm is designed at system level to generate the optimal active and reactive power setpoints, which are then sent to the device level for controlling inverters. The proposed power optimization scheme is able to mitigate voltage deviations and minimize the operational cost of the microgrid. Comprehensive case studies and real-time simulator test are provided to demonstrate the feasibility and efficacy of the proposed power control and optimization strategy. © 2005-2012 IEEE.

A hybrid modulation control for wireless power transfer systems to improve efficiency under light-load conditions

- Li, Yong, Sun, Wenjun, Zhu, Xiao, Hu, Jiefeng

  • Authors: Li, Yong , Sun, Wenjun , Zhu, Xiao , Hu, Jiefeng
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industrial Electronics Vol. 69, no. 7 (2022), p. 6870-6880
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  • Description: Traditional wireless power transfer (WPT) systems usually adopt the triple-phase-shift control method to maintain a constant output voltage, track the maximum system efficiency point (MEPT), and achieve zero-voltage-switching (ZVS) operation for various applications. However, these three targets are achieved at the cost of high reactive power on both primary and secondary sides, especially under light-load conditions, leading to low efficiency. This has become one of the challenges that hinder a further deployment of WPT technologies in practice. To address this vital problem, in this article, how the reactive power lowers the system efficiency is revealed based on a mathematical model established. Then, a hybrid modulation control strategy based on a proper selection between the full-bridge and half-bridge modes of the inverter and active rectifier is developed. An experimental prototype is constructed to verify the effectiveness of the proposed control method. Experimental results show that the proposed method can reduce the reactive power, maintain a constant output voltage, and realize the MEPT and ZVS operation, with high efficiencies up to 94.29% in a wide load range. © 1982-2012 IEEE.

A new coupling structure and position detection method for segmented control dynamic wireless power transfer systems

- Li, Xiaofei, Hu, Jiefeng, Wang, Heshou, Dai, Xin, Sun, Yue

  • Authors: Li, Xiaofei , Hu, Jiefeng , Wang, Heshou , Dai, Xin , Sun, Yue
  • Date: 2020
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Power Electronics Vol. 35, no. 7 (2020), p. 6741-6745
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  • Description: In this letter, a new coupling structure for dynamic wireless power transfer (DWPT) systems is proposed. Bipolar coils are symmetrically placed on the transmitter unipolar coils, resulting in natural decoupling between the bipolar coils and the unipolar coils. This special structure can mitigate the self-couplings between the adjacent unipolar transmitter coils and hence facilitate the design of the compensation circuit. Another remarkable advantage of this design is that it can lead to a stable mutual coupling between the transmitter array and the receiver when the receiver moves along the transmitter, making it a natural fit for DWPT applications. Furthermore, to reduce the electromagnetic interference and power loss, an automatic segmented control scheme is implemented, and a position detection method by monitoring the primary current is developed. The feasibility of the proposed coupling structure and the position detection method are verified on a laboratory prototype with 72-V output voltage. The experimental results show that the power fluctuation is within ±2.5%, and system efficiency is around 90%. (This letter is accompanied by a video demonstrating the experimental test). © 2020 IEEE.

A new current limiting and overload protection scheme for distributed inverters in microgrids under grid faults

- Li, Zilin, Hu, Jiefeng, Chan, Ka Wing

  • Authors: Li, Zilin , Hu, Jiefeng , Chan, Ka Wing
  • Date: 2021
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industry Applications Vol. 57, no. 6 (2021), p. 6362-6374
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  • Description: Unlike a synchronous generator that could withstand a large overcurrent, an inverter-based distributed generation (DG) has low thermal inertia, and the inverter is likely damaged by overcurrents during grid faults. In this article, a new strategy, namely positive-And negative-sequence limiting with stability enhanced P-f droop control (PNSL-SEPFC), is proposed to limit the output currents and active power of droop-controlled inverters in islanded microgrids. This strategy is easy to implement in the inverter controller and does not require any fault detection. Inverter stability is analyzed mathematically, which gives guidelines to design the parameters of the PNSL-SEPFC strategy. PSCAD/EMTDC simulation based on a four-DG microgrid shows that the proposed PNSL-SEPFC can limit inverter output currents and powers with better performance under both symmetrical and asymmetrical faults. Furthermore, hardware experiments demonstrate that the proposed PNSL-SEPFC can ensure the inverters riding through grid faults safely and stably. (A video of experimental waveforms is attached.). © 1972-2012 IEEE.

A new current limiting and overload protection strategy for droop-controlled voltage-source converters in islanded AC microgrids under grid faulted conditions

- Li, Zi-Lin, Hu, Jiefeng, Chan, Ka Wing

  • Authors: Li, Zi-Lin , Hu, Jiefeng , Chan, Ka Wing
  • Date: 2020
  • Type: Text , Conference paper
  • Relation: 12th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2020,Detroit, MI, USA, USA, 11-15 Oct. 2020 p. 3888-3893
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  • Description: Grid-forming voltage source converter (VSC) plays a vital role in the future renewable energy-based utility grid. Limited by the thermal capability of semiconductor switches, grid-forming VSC-based distributed generation units (DGs) cannot stand excess overcurrent like synchronous generators (SG) during large transient disturbances. In order to protect the VSC from overcurrent and ride through the transient disturbances, a new current limiting and overload protection strategy is proposed in this paper. By properly selecting the maximum current thresholds in the synchronous rotating frame, overcurrent and overload protection are achieved simultaneously. The synchronization among DGs is enhanced by feeding back the output voltage in the q-axis to the active power droop control. A comparison study between the proposed strategy and two existing methods are conducted using a networked microgrid in PSCAD/EMTDC, examining the effectiveness of the proposed strategy. © 2020 IEEE.

A new hybrid cascaded switched-capacitor reduced switch multilevel inverter for renewable sources and domestic loads

- Rezaei, Mohammad, Nayeripour, Majid, Hu, Jiefeng, Band, Shahab, Mosavi, Amir, Khooban, Mohammad-Hassan

  • Authors: Rezaei, Mohammad , Nayeripour, Majid , Hu, Jiefeng , Band, Shahab , Mosavi, Amir , Khooban, Mohammad-Hassan
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Access Vol. 10, no. (2022), p. 14157-14183
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  • Description: This multilevel inverter type summarizes an output voltage of medium voltage based on a series connection of power cells employing standard configurations of low-voltage components. The main problems of cascaded switched-capacitor multilevel inverters (CSCMLIs) are the harmful reverse flowing current of inductive loads, the large number of switches, and the surge current of the capacitors. As the number of switches increases, the reliability of the inverter decreases. To address these issues, a new CSCMLI is proposed using two modules containing asymmetric DC sources to generate 13 levels. The main novelty of the proposed configuration is the reduction of the number of switches while increasing the maximum output voltage. Despite the many similarities, the presented topology differs from similar topologies. Compared to similar structures, the direction of some switches is reversed, leading to a change in the direction of current flow. By incorporating the lowest number of semiconductors, it was demonstrated that the proposed inverter has the lowest cost function among similar inverters. The role of switched-capacitor inrush current in the selection of switch, diode, and DC source for inverter operation in medium and high voltage applications is presented. The inverter performance to supply the inductive loads is clarified. Comparison of the simulation and experimental results validates the effectiveness of the proposed inverter topology, showing promising potentials in photovoltaic, buildings, and domestic applications. A video demonstrating the experimental test, and all manufacturing data are attached. © 2013 IEEE.

A new magnetic coupler with high rotational misalignment tolerance for unmanned aerial vehicles wireless charging

- Li, Yong, Sun, Wenjun, Liu, Junjiang, Liu, Yuhang, Yang, Xiao, Li, Yanling, Hu, Jiefeng, He, Zhengyou

  • Authors: Li, Yong , Sun, Wenjun , Liu, Junjiang , Liu, Yuhang , Yang, Xiao , Li, Yanling , Hu, Jiefeng , He, Zhengyou
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Power Electronics Vol. 37, no. 11 (2022), p. 12986-12991
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  • Description: In this letter, a novel magnetic coupler with high rotational misalignment tolerance is proposed for unmanned aerial vehicles (UAVs) wireless charging. The transmitting coil consists of an inner coil and an outer circular coil connected in series, which generates a horizontal magnetic field from the center to all periphery directions within the charging range. Then, to receive the flux effectively and to adapt to UAV's structure, a vertical square air-core coil is designed and attached to the landing gear. The proposed magnetic coupler can reduce significantly the magnetic fluxes penetrating through the body of the UAV, therefore mitigating electromagnetic interference with onboard devices. Simulation based on ANSYS Maxwell and experiments based on a laboratory prototype are carried out to validate the proposal. The results show that, the proposed magnetic coupler can transmit power in all 360° of rotational misalignments, and the output voltage of the wireless charging system fluctuates only 2% around the 48 V reference. © 1986-2012 IEEE.

A Novel Common Grounded Type 1-\varphi Five-Level Boost PV Inverter with Reduced Device Count

- Ardashir, Jaber, Ghadim, Hadi, Heydari, Dorsa, Hu, Jiefeng

  • Authors: Ardashir, Jaber , Ghadim, Hadi , Heydari, Dorsa , Hu, Jiefeng
  • Date: 2023
  • Type: Text , Conference paper
  • Relation: 8th International Conference on Technology and Energy Management, ICTEM 2023, Babol, Iran, 8-9 February 2023, 8th International Conference on Technology and Energy Management, ICTEM 2023
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  • Description: Common-grounded multi-level inverters with the input voltage boost ability are more common for grid-tied PV system applications. In this paper, a new five-level inverter topology is introduced that can generate a five-level voltage at the output stage, statically increase the input voltage, fully transfer the reactive power, eliminate the leakage current due to common-grounded capability, reduce the number of the power electronic components, self-balancing capability of switched capacitors voltage based on operation modes, and equality of switched capacitors voltage. The operation of the proposed inverter along with its comparison with other similar inverter topologies and the simulation results of the proposed inverter under different loads are demonstrates in this paper. The results indicate that the performance of the proposed inverter in the grid-connected PV system is best than other compared topologies. Also, experimental results with a prototype have been presented, which validates the simulation results and proves the applicability of the proposed inverter in grid-tied PV systems. © 2023 IEEE.

A novel continuous control set model predictive control for lc-filtered three-phase four-wire three-level voltage-source inverter

- Yang, Yong, Xiao, Yang, Fan, Mingdi, Wang, Kaixin, Zhang, Xinan, Hu, Jiefeng, Fang, Gang, Zeng, Weibo, Vazquez, Sergio, Rodriguez, Jose

  • Authors: Yang, Yong , Xiao, Yang , Fan, Mingdi , Wang, Kaixin , Zhang, Xinan , Hu, Jiefeng , Fang, Gang , Zeng, Weibo , Vazquez, Sergio , Rodriguez, Jose
  • Date: 2023
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Power Electronics Vol. 38, no. 4 (2023), p. 4572-4584
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  • Description: In this article, a novel continuous control set model predictive control (CCS-MPC) is proposed for an LC-filtered three-phase three-level four-wire voltage-source inverter (3P-4W-3L-VSI). The proposed MPC algorithm provides independent control of each phase of the 3P-4W-3L-VSI under various unbalanced load conditions, which shows superior performance under unbalanced loads. Furthermore, different from conventional MPC methods, the CCS-MPC achieves fixed switching frequency, hence simplifying the design of LC filters. In addition, dc offsets are introduced to the proposed modulation to effectively balance the neutral-point voltage of the 3P-4W-3L-VSI. Experimental results are presented to verify the effectiveness of the proposed MPC algorithm. © 1986-2012 IEEE.

A reconfigurable rectifier-based power improving method of free-standing two-coil magnetic field energy harvesters over a wide load range

- Li, Yong, Yan, Yihua, Yang, Huanyu, Hu, Jiefeng, He, Zhengyou

  • Authors: Li, Yong , Yan, Yihua , Yang, Huanyu , Hu, Jiefeng , He, Zhengyou
  • Date: 2023
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Power Electronics Vol. 38, no. 5 (2023), p. 5638-5643
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  • Description: Free-standing magnetic field energy harvesters (FSMFEHs) have promising potential in charging sensors used in electrical power grids. The output power of the FSMFEH is highly dependent on the load resistance. However, the load resistance of the sensors varies over a wide range during the operation process. Therefore, a crucial challenge for an FSMFEH system is to maintain high output power over a wide load range. In this letter, an innovative reconfigurable rectifier-based FSMFEH system with two coils connected in parallel is proposed. First, a new structure of two identical coils in parallel is proposed in magnetic energy harvesting applications. Then, a reconfigurable rectifier with two operation modes is developed to incorporate the new coil structure. By switching between the full-bridge mode and the half-bridge mode according to the actual load demand, the proposed FSMFEH can maintain high output power over a wide load range. In addition, the mode transition can be easily achieved by shorting one of the diodes, leading to a simple and low-loss control. The effectiveness of the proposed FSMFEH system is verified based on a laboratory prototype. It is provided that the experimental result is consistent with the theoretical analysis. The output power can be maintained above 8.19 mW within the 50-1500

A simultaneous power and data transmission technology based on coil multiplexing in domino-resonator WPT systems

- Li, Yong, Yang, Xiao, Sun, Wenjun, Hu, Jiefeng, He, Zhengyou

  • Authors: Li, Yong , Yang, Xiao , Sun, Wenjun , Hu, Jiefeng , He, Zhengyou
  • Date: 2023
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Power Electronics Vol. 38, no. 3 (2023), p. 2878-2883
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  • Description: To achieve parallel power and data transmission in domino-resonator wireless power transfer (WPT) systems, a novel simultaneous power, and data transfer (SPDT) technology based on coil multiplexing is proposed in this letter. Benefiting from the magnetic field characteristics of the bipolar coil structure, the power and data can be injected into multiplexed coils with different flow directions, leading to opposite induced voltage polarities in each coupling coil. Subsequently, a corresponding resonator circuit is developed to form independent power and data resonance loops. In addition, an injected data transmission scheme is developed for domino-resonator WPT systems. Compared with traditional SPDT methods, additional wave trappers and coupling structures are avoided by this proposed technology, and the interference between power and data transfer is significantly eliminated. A 23.6 W laboratory prototype with five domino resonators is built to validate the feasibility of this proposed technology. The experimental results show that the power transfer efficiency reaches 70% at 50 kb/s data transfer rate. © 1986-2012 IEEE.

A special magnetic coupler structure for three-coil wireless power transfer : analysis, design, and experimental verification

- Wang, Heshou, Cheng, Ka, Li, Xiaofei, Hu, Jiefeng

  • Authors: Wang, Heshou , Cheng, Ka , Li, Xiaofei , Hu, Jiefeng
  • Date: 2021
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Magnetics Vol. 57, no. 11 (2021), p.
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  • Description: In this article, a special magnetic coupler for three-coil wireless power transfer (WPT) is proposed to eliminate the mutual inductance between the source coil and the receiver coil, which can significantly improve the design freedom. Specifically, unipolar Q coil, mixed QDD coil, and bipolar DD coil are designed for the source coil, the transmitter coil ( $\text{T}_{\mathrm {X}}$ ), and the receiver coil ( $\text{R}_{\mathrm {X}}$ ), respectively. By making use of unipolar coils and bipolar coils, this structure magnetically decouples the receiver coil from the source coil. Meanwhile, under different lateral misalignment conditions, this new coupler facilitates maintaining high efficiency. A laboratory prototype has been constructed to validate the proposed structure, demonstrating that the proposed structure can realize inherent characteristics, enhance misalignment tolerance, and energy transfer. The potential applications are EV systems, but this design can be generalizable to other three-coil systems. © 1965-2012 IEEE.

A unified model predictive voltage and current control for microgrids with distributed fuzzy cooperative secondary control

- Shan, Yinghao, Hu, Jiefeng, Chan, Ka, Islam, Syed

  • Authors: Shan, Yinghao , Hu, Jiefeng , Chan, Ka , Islam, Syed
  • Date: 2021
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industrial Informatics Vol. 17, no. 12 (DEC 2021), p. 8024-8034
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  • Description: A microgrid formed by a cluster of parallel distributed generation (DG) units is capable of operating in either islanded mode or grid-connected mode. Traditionally, by using model predictive control algorithms, these two operation modes can be achieved with two separate and different cost functions, which brings in control complexity and hence, compromises system reliability. In this article, a unified model predictive voltage and current control strategy is proposed for both islanded and grid-connected operations and their smooth transition. The cost function is kept unified with voltage and current taken into account without altering the control architecture. It can be used for high-quality voltage supply at the primary control level and for bidirectional power flow at the tertiary control level. In addition, by only using DGs' own and neighboring information, a distributed fuzzy cooperative algorithm is developed at the secondary layer to mitigate the voltage and frequency deviations inherent from the power droop. The fuzzy controller can optimize the secondary control coefficients for further voltage quality improvement. Comprehensive tests under various scenarios demonstrate the merits of the proposed control strategy over traditional methods.

Adaptation of a real-time deep learning approach with an analog fault detection technique for reliability forecasting of capacitor banks used in mobile vehicles

- Rezaei, Mohammad, Fathollahi, Arman, Rezaei, Sajad, Hu, Jiefeng, Gheisarnejad, Meysam, Teimouri, Ali, Rituraj, Rituraj, Mosavi, Amir, Khooban, Mohammad-Hassan

  • Authors: Rezaei, Mohammad , Fathollahi, Arman , Rezaei, Sajad , Hu, Jiefeng , Gheisarnejad, Meysam , Teimouri, Ali , Rituraj, Rituraj , Mosavi, Amir , Khooban, Mohammad-Hassan
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Access Vol. 10, no. (2022), p. 132271-132287
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  • Description: The DC-Link capacitor is defined as the essential electronics element which sources or sinks the respective currents. The reliability of DC-link capacitor-banks (CBs) encounters many challenges due to their usage in electric vehicles. Heavy shocks may damage the internal capacitors without shutting down the CB. The fundamental development obstacles of CBs are: lack of considering capacitor degradation in reliability assessment, the impact of unforeseen sudden internal capacitor faults in forecasting CB lifetime, and the faults consequence on CB degradation. The sudden faults change the CB capacitance, which leads to reliability change. To more accurately estimate the reliability, the type of the fault needs to be detected for predicting the correct post-fault capacitance. To address these practical problems, a new CB model and reliability assessment formula covering all fault types are first presented, then, a new analog fault-detection method is presented, and a combination of online-learning long short-term memory (LSTM) and fault-detection method is subsequently performed, which adapt the sudden internal CB faults with the LSTM to correctly predict the CB degradation. To confirm the correct LSTM operation, four capacitors degradation is practically recorded for 2000-hours, and the off-line faultless degradation values predicted by the LSTM are compared with the actual data. The experimental findings validate the applicability of the proposed method. The codes and data are provided. © 2013 IEEE.

Adaptive droop control using adaptive virtual impedance for microgrids with variable PV outputs and load demands

- Li, Zilin, Chan, Ka, Hu, Jiefeng, Guerrero, Josep

  • Authors: Li, Zilin , Chan, Ka , Hu, Jiefeng , Guerrero, Josep
  • Date: 2021
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industrial Electronics Vol. 68, no. 10 (2021), p. 9630-9640
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  • Description: In microgrids, intermittency of renewable energy sources (RES) and uncertain state-of-charge (SoC) of energy storage systems (ESS) can cause power deficiency to some distributed generation units (DGs). In this case, DGs with power deficiency may not meet the power demand, resulting in voltage collapse or frequency divergence. Unfortunately, this is seldom considered in inverter control design in existing literature. Thus, in-depth investigation into the microgrid performance under renewable energy resource fluctuations and appropriate control methods are urgently needed. In this article, an adaptive droop and adaptive virtual impedance control strategy is proposed. Unlike conventional droop control where the droop coefficients are fixed by assuming the DGs can always meet the load demand, the droop coefficients here are adjusted according to actual solar PV power output. In this way, proper power sharing among DGs can be achieved under renewable energy variation. Furthermore, the impact of varying DG capacities on system stability is mathematically investigated. An adaptive virtual impedance is then incorporated into the adaptive droop method to deal with the system instability caused by renewable energy variations. The proposed strategy is analyzed theoretically and validated in MATLAB/Simulink simulation and laboratory experiments. The results demonstrate the advantages of the proposed method over conventional approaches under various scenarios. © 1982-2012 IEEE.

An adaptive fault ride-through scheme for grid-forming inverters under asymmetrical grid faults

- Li, Zilin, Chan, Ka, Hu, Jiefeng, Or, Siu

  • Authors: Li, Zilin , Chan, Ka , Hu, Jiefeng , Or, Siu
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industrial Electronics Vol. 69, no. 12 (2022), p. 12912-12923
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  • Description: Three-phase four-wire grid-forming (GFM) inverters are promising to interface distributed energy resources into low-voltage networks. However, these inverters are prone to overcurrent under grid faults. Physically increasing the inverter current capacity is not cost-effective to cope with complicated fault conditions. In this article, an adaptive fault ride-through (FRT) scheme based on instantaneous saturators and virtual negative- and zero-sequence resistances is proposed. It features not only overcurrent limitation by modifying voltage references, but also seamless transition between normal and grid fault conditions. The proposed FRT scheme is first analyzed from different aspects, including the virtual sequence resistances, grid short-circuit ratio, fault types, and fault levels. The virtual sequence resistances are then designed to be adaptive to ensure high voltage quality at the healthy phase. The proposed FRT scheme is verified by MATLAB/Simulink simulations under asymmetrical faults. A laboratory platform with a grid-connected 3kW GFM inverter is further constructed to demonstrate its effectiveness (a video of the experimental results under three asymmetrical faults is attached). © 1982-2012 IEEE.

An investigation of compensation networks for three-coil wireless power transfer

- Wang, H. S., Cheng, K. W. E., Hu, Jiefeng

Analysis and design of a cost-effective single-input and regulatable multioutput WPT system

- Li, Xiaofei, Zheng, Fan, Wang, Heshou, Dai, Xin, Sun, Yue, Hu, Jiefeng

  • Authors: Li, Xiaofei , Zheng, Fan , Wang, Heshou , Dai, Xin , Sun, Yue , Hu, Jiefeng
  • Date: 2023
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Power Electronics Vol. 38, no. 6 (2023), p. 6939-6944
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  • Description: In this letter, a single-input and regulatable multioutput wireless power transfer system is presented. In particular, the system uses positive and negative half-wave rectifiers and a synchronous rectifier to realize multiple output channels. Each output channel is controllable, providing a flexible wireless charger to meet various charging requirements. Moreover, this system utilizes the inherent half-wave-rectifier channels (#B and #C) to detect synchronous signals for the rectifiers rather than using additional synchronous detection circuits, thereby leading to a cost-effective system. Finally, a 300 W laboratory prototype is contrasted with three voltage levels, i.e., 48, 30, and 24 V. With the help of the control logic, this system shows excellent robustness against different occasions, such as load variations, input disturbance, and misalignment. The overall efficiency ranges from 86.7% to 90.6%. © 1986-2012 IEEE.