This page has only limited features, please log in for full access.

Dr. Xuezhi Wu
Beijing Jiaotong University

Basic Info


Research Keywords & Expertise

0 microgrid
0 DCDC converter
0 Multilevel
0 Motor Drive And Its Control
0 Grid-connected converter

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

Xuezhi Wu receviced his B.S. degree in Application of Electronic Technology from Northern Jiaotong University, Beijing, China, in 1996, his M.S. degree in Power Electronics and Power Drives from Northern Jiaotong University, Beijing, China, in 1999, and his Ph.D. degree in Power Electronics and Power Drives from Tsinghua University, Beijing, China, in 2002. His general research interests include new energy grid connection technology, microgrid converter and microgrid systems, and high power motor control technology.

Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Journal article
Published: 24 May 2021 in Energies
Reads 0
Downloads 0

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.

ACS Style

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 Style

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 (11):3031.

Chicago/Turabian Style

Mian 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.

Journal article
Published: 26 April 2021 in IEEE Access
Reads 0
Downloads 0

When the permanent magnet synchronous motor (PMSM) operates at low carrier ratio, the decoupling capability and dynamic performance of the proportional-integral (PI) controller are limited by the digitization delay. In this paper, a deadbeat PI controller is proposed by modified the feedforward. With the modified feedforward, the open-loop transfer function can eliminate imaginary components. Thereby the full decoupling of $d$ and $q$ is realized. At the same time, the controller also has full control over the location of the closed-loop poles, indicating that it can have a deadbeat response for the command tracking. For the disturbance rejection, the controller allows us to select the speed with which the controller can cancel the effect of a disturbance. Further considering that the motor parameters are inaccurate, by designing the controller coefficients with the maximum value of the closed-loop poles, the current-loop can ensure the dynamic performance and harmonic suppression ability. Finally, the effectiveness of the proposed controller is verified by the simulations and experiments.

ACS Style

Zhijian Zhang; Long Jing; Xuezhi Wu; Wenzheng Xu; Jingdou Liu; Gege Lyu; Zilian Fan. A Deadbeat PI Controller With Modified Feedforward for PMSM Under Low Carrier Ratio. IEEE Access 2021, 9, 63463 -63474.

AMA Style

Zhijian Zhang, Long Jing, Xuezhi Wu, Wenzheng Xu, Jingdou Liu, Gege Lyu, Zilian Fan. A Deadbeat PI Controller With Modified Feedforward for PMSM Under Low Carrier Ratio. IEEE Access. 2021; 9 ():63463-63474.

Chicago/Turabian Style

Zhijian Zhang; Long Jing; Xuezhi Wu; Wenzheng Xu; Jingdou Liu; Gege Lyu; Zilian Fan. 2021. "A Deadbeat PI Controller With Modified Feedforward for PMSM Under Low Carrier Ratio." IEEE Access 9, no. : 63463-63474.

Journal article
Published: 12 April 2021 in Sustainability
Reads 0
Downloads 0

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.

ACS Style

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 Style

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 (8):4261.

Chicago/Turabian Style

Jingya 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.

Journal article
Published: 13 November 2020 in Sustainability
Reads 0
Downloads 0

This paper proposes a coordinated voltage regulation method for active distribution networks (ADNs) to mitigate nodal voltage fluctuations caused by photovoltaic (PV) power fluctuations, where a three-stage optimization scheme is developed to coordinate and optimize the tap position of on-load tap changers (OLTCs), the reactive power of capacitor banks (CBs), and the active and reactive power of soft open points (SOPs). The first stage aims to schedule the OLTC and CBs hourly using the rolling optimization algorithm. In the second stage, a multi-objective optimization model of SOPs is established to periodically (15 min) optimize the active and reactive power of each SOP. Meanwhile, this model is also responsible for optimizing the Q-V droop control parameters of each SOP used in the third stage. The aim of the third stage is to suppress real-time (1 min) voltage fluctuations caused by rapid changes in PV power, where the Q-V droop control is developed to regulate the actual reactive power of SOPs automatically, according to the measured voltage at the SOPs’ connection points. Furthermore, numerous simulations and comparisons are carried out on a modified IEEE 33-bus distribution network to verify the effectiveness and correctness of the proposed voltage regulation method.

ACS Style

Ruonan Hu; Wei Wang; Zhe Chen; Xuezhi Wu; Long Jing; Wei Ma; Guohong Zeng. Coordinated Voltage Regulation Methods in Active Distribution Networks with Soft Open Points. Sustainability 2020, 12, 9453 .

AMA Style

Ruonan Hu, Wei Wang, Zhe Chen, Xuezhi Wu, Long Jing, Wei Ma, Guohong Zeng. Coordinated Voltage Regulation Methods in Active Distribution Networks with Soft Open Points. Sustainability. 2020; 12 (22):9453.

Chicago/Turabian Style

Ruonan Hu; Wei Wang; Zhe Chen; Xuezhi Wu; Long Jing; Wei Ma; Guohong Zeng. 2020. "Coordinated Voltage Regulation Methods in Active Distribution Networks with Soft Open Points." Sustainability 12, no. 22: 9453.

Journal article
Published: 03 September 2020 in IEEE Access
Reads 0
Downloads 0

The continuous growth of Renewable Energy (RE) in the grid reduces system inertia and damping, impacting the overall stability of power systems. To alleviate this issue, “virtual” inertia can be provided by power electronics converters. Under this functionality they are controlled to emulate the behavior of rotating machines, operating as Virtual Synchronous Generators (VSGs). However, grid-connected inverters are susceptible to voltage and frequency disturbances which negatively affect their performance. Therefore, this paper introduces a Unified Power Flow Controller (UPFC) with VSG functionality that can compensate for voltage variations at the point of common coupling and provide a constant voltage reference for the connection of remote RE systems. The detailed controlled strategy together with the small-signal analysis are also developed in this work. The UPFC-VSG is compared with an equivalent Static Synchronous Compensator (STATCOM) with centralized energy storage also under VSG control to illustrate the major benefits of the UPFC-VSG. Validation of the analysis and the proposed control method is provided through simulation of a UPFC-VSG and a STATCOM-VSG supporting the grid-connection of a 100-MVA RE system.

ACS Style

Shuai Wang; Long Jing; Yuming Zhao; Harith R. Wickramasinghe; Xuezhi Wu; Georgios Konstantinou. Operation of Unified Power Flow Controller as Virtual Synchronous Generator. IEEE Access 2020, 8, 162569 -162580.

AMA Style

Shuai Wang, Long Jing, Yuming Zhao, Harith R. Wickramasinghe, Xuezhi Wu, Georgios Konstantinou. Operation of Unified Power Flow Controller as Virtual Synchronous Generator. IEEE Access. 2020; 8 (99):162569-162580.

Chicago/Turabian Style

Shuai Wang; Long Jing; Yuming Zhao; Harith R. Wickramasinghe; Xuezhi Wu; Georgios Konstantinou. 2020. "Operation of Unified Power Flow Controller as Virtual Synchronous Generator." IEEE Access 8, no. 99: 162569-162580.

Journal article
Published: 17 August 2020 in IEEE Access
Reads 0
Downloads 0

LLC resonant converters can achieve soft switching and loss reduction. However, the analysis methods of wide frequency range LLC converters generally have problems with incomplete working condition analysis at non-resonant frequencies and there is always a tradeoff between the accuracy and the simplicity. These problems will affect the loss calculation, synchronous rectification and so on. The research objective of this paper focuses on the full-bridge LLC resonant converter. In this paper, three conditions are analyzed in time-domain including switching frequency lower than the resonant frequency at heavy load, switching frequency lower than the resonant frequency at light load, and switching frequency larger than the resonant frequency. Based on proper assumption and simplification, the approximate equivalent of the trigonometric function is used to simplify the complex time-domain equations. The simplified equations are obtained with the resonant capacitor voltage and resonant inductor current as the key variables. In order to make the simplified equations easy to use, an iterative calculation model is proposed with more simplicity than sophisticated software to solve nonlinear equations. The simplified equations and the model proposed in this paper are verified by comparison with the fundamental analysis methods, the simulation, and the experiments. By using the iterative calculation model, the voltage, current, time and other variables of switching points can be obtained with the relative error less than 3% to theoretic values, which can be used in loss calculation, synchronous rectification and so on. And the iterative calculation model can be realized on DSP or other processors in real-time.

ACS Style

Jingkai Niu; Yibing Tong; Qing Ding; Xuezhi Wu; Xiaomin Xin; Xin Wang. Time Domain Simplified Equations and its Iterative Calculation Model for LLC Resonant Converter. IEEE Access 2020, 8, 151195 -151207.

AMA Style

Jingkai Niu, Yibing Tong, Qing Ding, Xuezhi Wu, Xiaomin Xin, Xin Wang. Time Domain Simplified Equations and its Iterative Calculation Model for LLC Resonant Converter. IEEE Access. 2020; 8 (99):151195-151207.

Chicago/Turabian Style

Jingkai Niu; Yibing Tong; Qing Ding; Xuezhi Wu; Xiaomin Xin; Xin Wang. 2020. "Time Domain Simplified Equations and its Iterative Calculation Model for LLC Resonant Converter." IEEE Access 8, no. 99: 151195-151207.

Journal article
Published: 06 January 2020 in IEEE Access
Reads 0
Downloads 0

As a key device to facilitate power flow in the multi-terminal direct current (MTDC) transmission system, DC power flow controller (DCPFC) can effectively expand the power flow regulation area by implementing its multiport output functionality. In order to solve the coupling issue between the transmission line current and the capacitor voltage of the inter-line multiport DCPFC (M-DCPFC), an improved M-DCPFC with a partial power rated auxiliary DC/DC converter unit is proposed in this paper. It provides the advantages of power flow reversal, high adjustment flexibility and low port-expansion cost. Meanwhile, a generic control strategy is developed for the M-DCPFC with random number of the ports. Moreover, from the perspective of the transmission system, the proposed M-DCPFC is modeled as the equivalent series voltage source. Its power flow adjustment capability and its impact on the local voltage source converter (VSC) stations are investigated in detail in this paper. Lastly, to validate the effectiveness of the proposed M-DCPFC, it is first tested in the simulations of the MATLAB/Simulink and then deployed on an experiment platform. Both simulation and experimental results show that the proposed M-DCPFC can achieve stable power flow control in different conditions.

ACS Style

Wen Wu; Xuezhi Wu; Yuming Zhao; Luocheng Wang; Tiefu Zhao; Long Jing. An Improved Multiport DC Power Flow Controller for VSC-MTDC Grids. IEEE Access 2020, 8, 7573 -7586.

AMA Style

Wen Wu, Xuezhi Wu, Yuming Zhao, Luocheng Wang, Tiefu Zhao, Long Jing. An Improved Multiport DC Power Flow Controller for VSC-MTDC Grids. IEEE Access. 2020; 8 (99):7573-7586.

Chicago/Turabian Style

Wen Wu; Xuezhi Wu; Yuming Zhao; Luocheng Wang; Tiefu Zhao; Long Jing. 2020. "An Improved Multiport DC Power Flow Controller for VSC-MTDC Grids." IEEE Access 8, no. 99: 7573-7586.

Journal article
Published: 13 December 2019 in IEEE Access
Reads 0
Downloads 0

To solve the economic dispatch (ED) problem of multiple distributed generations in the microgrid, this paper proposes a fully distributed method by using the exact diffusion strategy which can achieve exact convergence under sparse communication network. Firstly, a multi-agent hierarchical control architecture for the microgrid is designed. The microgrid central controller (MGCC) agent does not act as centralized control but instead participates in the distributed optimization between the bottom layer agents. Furthermore, an economic dispatch optimization model is established which aims at minimizing the operation cost, optimizing the active power of all dispatchable agents including distributed generators and flexible loads on demand side, and realizing the economic utilization of resources. A modified diffusion algorithm supporting full distributed optimization is proposed to solve it, which does not depend on the “leader unit” and is applicable to the actual problem. The modified algorithm has faster convergence speed, higher stability and stronger expansibility than consensus algorithm. Six scenarios are adopted to verify the proposed method. The result shows that the agent framework and the algorithm can cope with changing of communication topology and realize the “plug and play”. The output will converge to the optimal dispatch solution even if communication fails.

ACS Style

Yongjing He; Wei Wang; Xuezhi Wu. Multi-Agent Based Fully Distributed Economic Dispatch in Microgrid Using Exact Diffusion Strategy. IEEE Access 2019, 8, 7020 -7031.

AMA Style

Yongjing He, Wei Wang, Xuezhi Wu. Multi-Agent Based Fully Distributed Economic Dispatch in Microgrid Using Exact Diffusion Strategy. IEEE Access. 2019; 8 (99):7020-7031.

Chicago/Turabian Style

Yongjing He; Wei Wang; Xuezhi Wu. 2019. "Multi-Agent Based Fully Distributed Economic Dispatch in Microgrid Using Exact Diffusion Strategy." IEEE Access 8, no. 99: 7020-7031.

Journal article
Published: 27 June 2019 in Energies
Reads 0
Downloads 0

A DC power flow controller (DCPFC) can help to facilitate power flow routing in the multi-terminal high-voltage direct current (HVDC) transmission system. Realizing its multi-port output can effectively improve the device regulate range and capability. Based on analysis of the traditional multi-port interline DC power flow controller (MI-DCPFC), this paper presents a switches reduced topology of MI-DCPFC. In addition, for solving the problem of coupling of the port-output voltage of the traditional MI-DCPFC, a novel control strategy based on carrier phase shifting pulse width modulation (CPS-PWM) is proposed. It implements the decoupling of the port-output voltage of MI-DCPFC, which can ensure completely independent tracking of the power flow regulating commands for different controlled lines. Moreover, key relationships between the system state variables are also analyzed and detailed in this study. Finally, the performance of the proposed controller and control strategy are confirmed with the simulation and experiment studies under different conditions.

ACS Style

Wen Wu; Xuezhi Wu; Long Jing; Jingyuan Yin. Investigate on a Simplified Multi-Port Interline DC Power Flow Controller and Its Control Strategy. Energies 2019, 12, 2480 .

AMA Style

Wen Wu, Xuezhi Wu, Long Jing, Jingyuan Yin. Investigate on a Simplified Multi-Port Interline DC Power Flow Controller and Its Control Strategy. Energies. 2019; 12 (13):2480.

Chicago/Turabian Style

Wen Wu; Xuezhi Wu; Long Jing; Jingyuan Yin. 2019. "Investigate on a Simplified Multi-Port Interline DC Power Flow Controller and Its Control Strategy." Energies 12, no. 13: 2480.

Journal article
Published: 03 March 2019 in Sustainability
Reads 0
Downloads 0

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.

ACS Style

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 Style

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 (5):1324.

Chicago/Turabian Style

Wei 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.

Journal article
Published: 10 November 2017 in Energies
Reads 0
Downloads 0

A modular multilevel converter (MMC) is considered to be a promising topology for medium- or high-power applications. However, a significantly increased amount of sub-modules (SMs) in each arm also increase the risk of failures. Focusing on the fault-tolerant operation issue for the MMC under SM faults, the operation characteristics of MMC with different numbers of faulty SMs in the arms are analyzed and summarized in this paper. Based on the characteristics, a novel circulating current-suppressing (CCS) fault-tolerant control strategy comprised of a basic control unit (BCU) and virtual resistance compensation control unit (VRCCU) in two parts is proposed, which has three main features: (i) it can suppress the multi-different frequency components of the circulating current under different SM fault types simultaneously; (ii) it can help fast limiting of the transient fault current caused at the faulty SM bypassed moment; and (iii) it does not need extra communication systems to acquire the information of the number of faulty SMs. Moreover, by analyzing the stability performance of the proposed controller using the Root-Locus criterion, the election principle of the value of virtual resistance is revealed. Finally, the efficiency of the control strategy is confirmed with the simulation and experiment studies under different fault conditions.

ACS Style

Wen Wu; Xuezhi Wu; Jingyuan Yin; Long Jing; Shuai Wang; Jinke Li. Characteristic Analysis and Fault-Tolerant Control of Circulating Current for Modular Multilevel Converters under Sub-Module Faults. Energies 2017, 10, 1827 .

AMA Style

Wen Wu, Xuezhi Wu, Jingyuan Yin, Long Jing, Shuai Wang, Jinke Li. Characteristic Analysis and Fault-Tolerant Control of Circulating Current for Modular Multilevel Converters under Sub-Module Faults. Energies. 2017; 10 (11):1827.

Chicago/Turabian Style

Wen Wu; Xuezhi Wu; Jingyuan Yin; Long Jing; Shuai Wang; Jinke Li. 2017. "Characteristic Analysis and Fault-Tolerant Control of Circulating Current for Modular Multilevel Converters under Sub-Module Faults." Energies 10, no. 11: 1827.