This page has only limited features, please log in for full access.
Fen Tang received her B.S. degree in Electrical Engineering and her Ph.D. degree in Power Electronics and Electric Drives from Beijing Jiaotong University, Beijing, China, in 2006 and 2013, respectively. She was a Guest Post-Doctoral Researcher with the Department of Energy Technology, Aalborg University, Aalborg, Denmark, from 2013 to 2014. She is currently an Associate Professor in the Department of Electrical Engineering, Beijing Jiaotong University, Beijing, China. Her current research interests include microgrids, wind power generation systems, power converters for renewable generation systems, power quality, and motor control.
The three level converters have an inherent problem of the neutral point (NP) voltage unbalance due to the split dc-link capacitors. This NP voltage unbalance degrades the output voltage/current waveform quality. A carrier based discontinuous pulse width modulation (CB-DPWM) with NP voltage balancing strategy- that involves the injection of calculated zero-sequence voltages to the original modulation signal - is implemented for the three level T-type converter in this paper. The zero-sequence voltages are determined from the space vector synthesis of the converter output voltages. This method allows the determination of the zero-sequence voltages with few judgment conditions. Unlike the space vector based discontinuous pulse width modulation (SVB-DPWM), the CB-DPWM is easier to realize in practical applications. Moreover, the proposed CB-DPWM can also be directly used in parallel systems, which can suppress NP voltage ripples and circulating currents simultaneously by a coordinated strategy. The efficacy of the proposed method in balancing the neutral point voltage in single and parallel systems is demonstrated by simulations and experiments.
Jiayu Zhou; Joseph Olorunfemi Ojo; Fen Tang; Josiah Okpanachi Haruna; Poh Chiang Loh. A Carrier-Based Discontinuous PWM for Single and Parallel Three-Level T-Type Converters With Neutral-Point Potential Balancing. IEEE Transactions on Industry Applications 2021, 57, 5117 -5127.
AMA StyleJiayu Zhou, Joseph Olorunfemi Ojo, Fen Tang, Josiah Okpanachi Haruna, Poh Chiang Loh. A Carrier-Based Discontinuous PWM for Single and Parallel Three-Level T-Type Converters With Neutral-Point Potential Balancing. IEEE Transactions on Industry Applications. 2021; 57 (5):5117-5127.
Chicago/Turabian StyleJiayu Zhou; Joseph Olorunfemi Ojo; Fen Tang; Josiah Okpanachi Haruna; Poh Chiang Loh. 2021. "A Carrier-Based Discontinuous PWM for Single and Parallel Three-Level T-Type Converters With Neutral-Point Potential Balancing." IEEE Transactions on Industry Applications 57, no. 5: 5117-5127.
DC-DC converters with constant power loads are mostly used in DC microgrids. Negative impedance and large disturbances of constant power loads may lead to the instability of DC-DC converters. To address this issue, a nonlinear control strategy consisting of an improved passivity-based controller and nonlinear power observer is proposed in this paper. First, an improved passivity-based controller is designed based on the port-controlled Hamiltonian with dissipation model. By proper damping and interconnection injecting, the fast dynamic response of output voltage and stability of the DC-DC converter is achieved. Second, the constant power load is observed by a nonlinear power observer, which is adopted to estimate the power variation of the constant power load within a small settling time and improve the adaptability of the DC-DC converter under power disturbance. Finally, the simulation and experimental results are presented, which illustrate the proposed control strategy not only ensures the stability of the DC-DC converter under large disturbances, but also can track the desired operating point with low voltage overshoot in no more than 10 milliseconds.
Mian Wang; Fen Tang; Xuezhi Wu; Jingkai Niu; Yajing Zhang; Jiuhe Wang. A Nonlinear Control Strategy for DC-DC Converter with Unknown Constant Power Load Using Damping and Interconnection Injecting. Energies 2021, 14, 3031 .
AMA StyleMian Wang, Fen Tang, Xuezhi Wu, Jingkai Niu, Yajing Zhang, Jiuhe Wang. A Nonlinear Control Strategy for DC-DC Converter with Unknown Constant Power Load Using Damping and Interconnection Injecting. Energies. 2021; 14 (11):3031.
Chicago/Turabian StyleMian Wang; Fen Tang; Xuezhi Wu; Jingkai Niu; Yajing Zhang; Jiuhe Wang. 2021. "A Nonlinear Control Strategy for DC-DC Converter with Unknown Constant Power Load Using Damping and Interconnection Injecting." Energies 14, no. 11: 3031.
The virtual synchronous generator (VSG), which emulates the essential behavior of the conventional synchronous generator, has attracted great attention. This paper proposes to analyze the harmonic resonance characteristics in VSG using the state-space model. The analysis is based on a full-order state-space small-signal model that fully considers the dynamic of the inner loops and the VSG-based outer power control loop. Participation analysis is used to point out the contributions of different states to the eigenvalues. Moreover, eigenvalue locus and singular value decomposition (SVD) are applied together to evaluate the impact of the inner loop parameters on the harmonic resonance characteristics around the LCL filter resonance frequency. The analysis indicates that the harmonic resonance instability is mainly caused by decreasing the proportional gains of the current loop and the voltage loop. Finally, extensive numerical simulation and experimental results are given to verify the validity of the theoretical analysis. Both the simulation and experimental results indicate that the voltage of the common coupling point is unstable after decreasing the proportional gains of the current and voltage controllers. As K pc decreases from 5 to 0.4 or K pv decreases from 0.6 to 0.2, the harmonic distortion factor (HDF) around the LCL filter resonance frequency increases. Furthermore, the consistency of simulation results, experimental results, and the theoretical analysis results is validated.
Jingya Jiang; Wei Wang; Xuezhi Wu; Fen Tang; Zhengwen Yang; Xiangjun Li. Analysis of Harmonic Resonance Characteristics in Grid-Connected LCL Virtual Synchronous Generator. Sustainability 2021, 13, 4261 .
AMA StyleJingya Jiang, Wei Wang, Xuezhi Wu, Fen Tang, Zhengwen Yang, Xiangjun Li. Analysis of Harmonic Resonance Characteristics in Grid-Connected LCL Virtual Synchronous Generator. Sustainability. 2021; 13 (8):4261.
Chicago/Turabian StyleJingya Jiang; Wei Wang; Xuezhi Wu; Fen Tang; Zhengwen Yang; Xiangjun Li. 2021. "Analysis of Harmonic Resonance Characteristics in Grid-Connected LCL Virtual Synchronous Generator." Sustainability 13, no. 8: 4261.
The power fluctuations of grid-connected photovoltaic (PV) systems have negative impacts on the power quality and stability of the utility grid. In this study, the combinations of a battery/supercapacitor hybrid energy storage system (HESS) and the PV power curtailment are used to smooth PV power fluctuations. A PV power curtailment algorithm is developed to limit PV power when power fluctuation exceeds the power capacity of the HESS. A multi-objective optimization model is established to dispatch the HESS power, considering energy losses and the state of charge (SOC) of the supercapacitor. To prevent the SOCs of the HESS from approaching their lower limits, a SOC correction strategy is proposed to correct the SOCs of the HESS. Moreover, this paper also investigates the performances (such as the smoothing effects, losses and lifetime of energy storage, and system net profits) of two different smoothing strategies, including the method of using the HESS and the proposed strategy. Finally, numerous simulations are carried out based on data obtained from a 750 kWp PV plant. Simulation results indicate that the proposed method is more economical and can effectively smooth power fluctuations compared with the method of using the HESS.
Wei Ma; Wei Wang; Xuezhi Wu; Ruonan Hu; Fen Tang; Weige Zhang. Control Strategy of a Hybrid Energy Storage System to Smooth Photovoltaic Power Fluctuations Considering Photovoltaic Output Power Curtailment. Sustainability 2019, 11, 1324 .
AMA StyleWei Ma, Wei Wang, Xuezhi Wu, Ruonan Hu, Fen Tang, Weige Zhang. Control Strategy of a Hybrid Energy Storage System to Smooth Photovoltaic Power Fluctuations Considering Photovoltaic Output Power Curtailment. Sustainability. 2019; 11 (5):1324.
Chicago/Turabian StyleWei Ma; Wei Wang; Xuezhi Wu; Ruonan Hu; Fen Tang; Weige Zhang. 2019. "Control Strategy of a Hybrid Energy Storage System to Smooth Photovoltaic Power Fluctuations Considering Photovoltaic Output Power Curtailment." Sustainability 11, no. 5: 1324.
This study presents an enhanced method for simultaneously achieving optimised disturbance damping and axis-decoupling in high-power converters operating in the synchronous rotating frame. High-power converters are considered here because they are normally constrained to a low-switching-to-fundamental pulse ratio, and hence experience a large control delay as a trade-off. This trade-off lowers bandwidth and phase margin, which in the synchronous frame, are further worsened by cross-coupling between the d- and q-axes. The proposed method, therefore, targets to remove axis-cross-coupling, so that the dynamics and stability of the high-power converter can be significantly improved, even with a large control delay. A procedure for optimising its performances has then been proposed, after evaluating pole-zero trajectories of three critical coefficients associated with filter decoupling, delay decoupling, and phase correction. Such coordinated evaluation using complex-vector models in the synchronous frame has previously not been performed and is hence a major contribution of the study. Simulation and experimental results presented have verified this contribution, the proposed method and its improvement over other recent methods found in the literature.
Qi Xiao; Fen Tang; Zhen Xin; Jiayu Zhou; Pengfei Chen; Poh Chiang Loh. Large time‐delay decoupling and correction in synchronous complex‐vector frame. IET Power Electronics 2019, 12, 254 -266.
AMA StyleQi Xiao, Fen Tang, Zhen Xin, Jiayu Zhou, Pengfei Chen, Poh Chiang Loh. Large time‐delay decoupling and correction in synchronous complex‐vector frame. IET Power Electronics. 2019; 12 (2):254-266.
Chicago/Turabian StyleQi Xiao; Fen Tang; Zhen Xin; Jiayu Zhou; Pengfei Chen; Poh Chiang Loh. 2019. "Large time‐delay decoupling and correction in synchronous complex‐vector frame." IET Power Electronics 12, no. 2: 254-266.
Second-order oscillating power is always generated by a single-phase converter. To decouple this oscillating power from its dc-link then requires a power decoupling circuit to operate continuously. In contrast, ac grid voltages supplying a three-phase converter are usually balanced. There will hence be no oscillating power, if grid currents are balanced too. However, grid voltages may become unbalanced during fault or other disturbances, which when multiplied with balanced currents, will result in oscillating power. Power decoupling for a three-phase converter is thus only necessary during fault, rather than continuously. Its target should also be to improve power quality even during fault, rather than to prolong lifetimes of capacitors claimed with single-phase decoupling. Those differences cause criteria applicable to selecting a power decoupling circuit for single- and three-phase converters to be different, especially when there are seven different types of faulted voltage conditions to consider. These considerations are now studied, before presenting experimental results for verifying effectiveness of all studied three-phase power-decoupled converters.
Jiayu Zhou; Fen Tang; Zhen Xin; Songwei Huang; Poh Chiang Loh; Jiuchun Jiang. Differences Between Continuous Single-Phase and Online Three-Phase Power-Decoupled Converters. IEEE Transactions on Power Electronics 2018, 34, 3487 -3503.
AMA StyleJiayu Zhou, Fen Tang, Zhen Xin, Songwei Huang, Poh Chiang Loh, Jiuchun Jiang. Differences Between Continuous Single-Phase and Online Three-Phase Power-Decoupled Converters. IEEE Transactions on Power Electronics. 2018; 34 (4):3487-3503.
Chicago/Turabian StyleJiayu Zhou; Fen Tang; Zhen Xin; Songwei Huang; Poh Chiang Loh; Jiuchun Jiang. 2018. "Differences Between Continuous Single-Phase and Online Three-Phase Power-Decoupled Converters." IEEE Transactions on Power Electronics 34, no. 4: 3487-3503.
Single-phase differential boost inverter, built from two identical DC-DC boost converters, has been suggested as an alternative to the usual connection of a DC-DC boost converter to a standard full-bridge inverter. Some control schemes for controlling it have also been proposed, but mostly for voltage regulation, supplying a standalone load, rather than grid-current control. Moreover, it has never been identified that two LCL filters are hidden in the differential boost topology. Problems related to their associated resonances have hence not been discussed, especially their variations with duty ratios. It is thus necessary here to unmask the hidden LCL filters, which upon clarified, permits vast knowledge from grid-current control of a standard LCL-filtered inverter to be extended for differential inverter control. However, the extension involves many challenges introduced by the varying resonance frequencies, nonlinearity and many control options permitted by the differential boost inverter. These challenges are addressed now with simulation and experimental results provided for verifying direct grid-current regulation of a differential boost inverter.
Songwei Huang; Fen Tang; Zhen Xin; Qi Xiao; Poh Chiang Loh. Grid-Current Control of a Differential Boost Inverter With Hidden LCL Filters. IEEE Transactions on Power Electronics 2018, 34, 889 -903.
AMA StyleSongwei Huang, Fen Tang, Zhen Xin, Qi Xiao, Poh Chiang Loh. Grid-Current Control of a Differential Boost Inverter With Hidden LCL Filters. IEEE Transactions on Power Electronics. 2018; 34 (1):889-903.
Chicago/Turabian StyleSongwei Huang; Fen Tang; Zhen Xin; Qi Xiao; Poh Chiang Loh. 2018. "Grid-Current Control of a Differential Boost Inverter With Hidden LCL Filters." IEEE Transactions on Power Electronics 34, no. 1: 889-903.
The unbalance of the three-phase grid-voltages/loads can cause double-frequency power ripples in the Voltage Source Converter (VSC) system. Such power ripples can further lead to current and/or voltage ripples on the DC link, which may create instability of the system, lower its efficiency and shorten the lifetime of DC sources (e.g. batteries). Existing control solutions cannot well solve this issue and even bring collateral damage. Several hardware solutions have recently been proposed to tackle these issues, but these methods suffer from large size, high cost and reduced system reliability. Instead, this paper proposed an improved topology to handle the problems faced by the VSC under unbalanced conditions. Although hardware modification is also needed, it will not increase the size and cost of the system since only one connecting line is added, which can be easily made on the power-stage PCB board. Moreover, the improved topology can also be used to reduce the leakage current in transformerless PV system and to eliminate the high frequency circulating current in multiple parallel converters. Theoretical analysis, simulation and experimental results are provided to explain the principle and to validate the effectiveness of the improved topology.
Fen Tang; Jiayu Zhou; Zhen Xin; Songwei Huang; Poh Chiang Loh. An Improved Three-Phase Voltage Source Converter With High-Performance Operation Under Unbalanced Conditions. IEEE Access 2018, 6, 15908 -15918.
AMA StyleFen Tang, Jiayu Zhou, Zhen Xin, Songwei Huang, Poh Chiang Loh. An Improved Three-Phase Voltage Source Converter With High-Performance Operation Under Unbalanced Conditions. IEEE Access. 2018; 6 (99):15908-15918.
Chicago/Turabian StyleFen Tang; Jiayu Zhou; Zhen Xin; Songwei Huang; Poh Chiang Loh. 2018. "An Improved Three-Phase Voltage Source Converter With High-Performance Operation Under Unbalanced Conditions." IEEE Access 6, no. 99: 15908-15918.
The boost inverter can be an alternative grid interfacing power converter for renewable energy sources since it can generate an AC voltage whose peak value could be greater than the DC voltage. When it connects to the grid, high quality output current is required, therefore, grid current is hoped to be controlled directly. A novel control strategy to control grid current with only one closed control loop is proposed in this paper, where identical control structure is employed for its two DC/DC boost converters. In this way, the harmonic components of two capacitor voltages can be controlled into almost the same, therefore, they can be cancelled out in the output voltage, which will lead to very low distortion of grid current. To find out the resonance that may be generated in the grid-connected condition, an equivalent model in the AC side of boost inverter is presented. Furthermore, an inductor-current feedback is designed to damp the resonance based on the LCLCL equivalent model, which helps to improve the stability of control system. Moreover, DC input current ripple is suppressed by introducing the common harmonic compensation components. Compared with the existing control strategies, the proposed method can be easily implemented and achieve both high quality of grid current and DC current. Comprehensive experimental results are presented to validate the effectiveness of the proposed control strategy.
Songwei Huang; Fen Tang; Zhen Xin; Qi Xiao; Poh Chiang Loh. High performance current control strategy for grid-connected boost DC-AC inverter. 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL) 2017, 1 -8.
AMA StyleSongwei Huang, Fen Tang, Zhen Xin, Qi Xiao, Poh Chiang Loh. High performance current control strategy for grid-connected boost DC-AC inverter. 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL). 2017; ():1-8.
Chicago/Turabian StyleSongwei Huang; Fen Tang; Zhen Xin; Qi Xiao; Poh Chiang Loh. 2017. "High performance current control strategy for grid-connected boost DC-AC inverter." 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL) , no. : 1-8.
The grid-voltage unbalance can result in a double-frequency component in the output power of a three-phase grid-connected converter, which significantly degrades the system performance. To address this issue, the power decoupling concept, which was previously developed for the single-phase system to handle the double-frequency power oscillation, is applied to the three-phase system in this paper. To begin with, three topologies are proposed to implement the power decoupling function in the three-phase converter system, which can maintain dc-link voltage constant while ac grid current balanced under unbalanced grid voltage through absorbing the double-frequency power component. Then, the control system realization of each power decoupling topology is presented and their working principles are described in detail. Furthermore, three prototypes are developed under different types of unbalanced grid voltage condition to evaluate the performance of the proposed methods. Experimental results are eventually provided to validate the effectiveness of the three proposed schemes.
Jiayu Zhou; Fen Tang; Zhen Xin; Songwei Huang; Poh Chiang Loh. Active power decoupling methods for three-phase grid-connected converters under unbalanced grid conditions. 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL) 2017, 1 -7.
AMA StyleJiayu Zhou, Fen Tang, Zhen Xin, Songwei Huang, Poh Chiang Loh. Active power decoupling methods for three-phase grid-connected converters under unbalanced grid conditions. 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL). 2017; ():1-7.
Chicago/Turabian StyleJiayu Zhou; Fen Tang; Zhen Xin; Songwei Huang; Poh Chiang Loh. 2017. "Active power decoupling methods for three-phase grid-connected converters under unbalanced grid conditions." 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL) , no. : 1-7.
Evaluation of modulation techniques for neutral-point-clamped inverters has been an extensively investigated theme. The conclusion at present is centered space vector modulation with phase-disposed carrier arrangement gives the best harmonic performance. This conclusion is however drawn at the inverter output terminals or with only a simple L-filter considered. It may therefore not be relevant for applications, where high-order filters are used for better attenuating the switching harmonics. The intention of this paper is thus to investigate the characteristics of different high-order filters, and then re-evaluate different modulation techniques when the inverters are conditioned by these filters. In total, five types of filters are considered with some of them eventually found to output better current quality when the alternative-phase-opposition-disposition carrier arrangement is used. The finding is thus different from common belief, especially in low switching frequencies. The same atypical finding has been found among standard sinusoidal, centered space-vector, and discontinuous modulation techniques when analyzed with the same high-order filters, as proven through simulation.
Jiazhi Liang; Jiuchun Jiang; Fen Tang; Poh Chiang Loh. Re-evaluation of modulation techniques for neutral-point-clamped inverters with high-order output filters. 2016 IEEE 7th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) 2016, 1 -6.
AMA StyleJiazhi Liang, Jiuchun Jiang, Fen Tang, Poh Chiang Loh. Re-evaluation of modulation techniques for neutral-point-clamped inverters with high-order output filters. 2016 IEEE 7th International Symposium on Power Electronics for Distributed Generation Systems (PEDG). 2016; ():1-6.
Chicago/Turabian StyleJiazhi Liang; Jiuchun Jiang; Fen Tang; Poh Chiang Loh. 2016. "Re-evaluation of modulation techniques for neutral-point-clamped inverters with high-order output filters." 2016 IEEE 7th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) , no. : 1-6.
Four-leg dc-ac power converters are widely used for the power grids to manage grid voltage unbalance caused by the interconnection of single-phase or three-phase unbalanced loads. These converters can further be connected in parallel to increase the overall power rating. The control of these converters poses a particular challenge if they are placed far apart with no links between them (e.g., in islanded microgrids). This challenge is studied in this paper with each four-leg converter designed to have improved common current sharing and selective voltage-quality enhancement. The common current sharing, including zero sequence component, is necessary since loads are spread over the microgrid and they are hence the common responsibility of all converters. The voltage-quality enhancement consideration should however be more selective since different loads have different sensitivity levels towards voltage disturbances. Converters connected to the more sensitive load buses should therefore be selectively triggered for compensation when voltage unbalances at their protected buses exceed the predefined thresholds. The proposed scheme is therefore different from conventional centralized schemes protecting only a common bus. Simulation and experimental results obtained have verified the effectiveness of the proposed scheme when applied to a four-wire islanded microgrid.
Xiao Zhou; Fen Tang; Poh Chiang Loh; Xinmin Jin; Wenping Cao. Four-Leg Converters With Improved Common Current Sharing and Selective Voltage-Quality Enhancement for Islanded Microgrids. IEEE Transactions on Power Delivery 2015, 31, 522 -531.
AMA StyleXiao Zhou, Fen Tang, Poh Chiang Loh, Xinmin Jin, Wenping Cao. Four-Leg Converters With Improved Common Current Sharing and Selective Voltage-Quality Enhancement for Islanded Microgrids. IEEE Transactions on Power Delivery. 2015; 31 (2):522-531.
Chicago/Turabian StyleXiao Zhou; Fen Tang; Poh Chiang Loh; Xinmin Jin; Wenping Cao. 2015. "Four-Leg Converters With Improved Common Current Sharing and Selective Voltage-Quality Enhancement for Islanded Microgrids." IEEE Transactions on Power Delivery 31, no. 2: 522-531.