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The flexible excitation system (FES) is a kind of novel excitation system with two channels for damping control. Besides the basic functions of traditional excitation systems, flexible excitation systems can provide reactive power support for the terminal voltage, and the large-capacity FES can improve the voltage stability and power-angle stability of synchronous generator units. However, with the increase in system capacity and the complication of control objectives, the difficulty of controller design will be increased. The randomness and fluctuation of new energy resources such as photovoltaic and wind turbines may cause disturbance and fault to the power system, which requires the coordinated control strategy for the FES to achieve stability in voltage and power angle. In this paper, the basic characteristics of FES are analyzed, and the mathematic model of the single machine infinite bus (SMIB) system based on FES is derived. The coordinated control strategy based on decoupling control of stator and rotor is proposed according to the optimal objectives of voltage stability and power-angle stability, and the linear optimal excitation control (LOEC) is adopted with the adaptive amplitude limiter (AAL) determined by fuzzy rules. The MATLAB/Simulink platform is established and the results verify the superiority of the proposed LOEC + AAL control strategy in large disturbance working conditions, which showed better robustness. The proposed coordinated control strategy provides an effective solution for industrial application and performance improvement of FES.
Yuwei Peng; Jiancheng Zhang; Chengxiong Mao; Hongtao Xiong; Tiantian Zhang; Dan Wang. A Coordinated Optimal Strategy for Voltage and Reactive Power Control with Adaptive Amplitude Limiter Based on Flexible Excitation System. Energies 2021, 14, 5212 .
AMA StyleYuwei Peng, Jiancheng Zhang, Chengxiong Mao, Hongtao Xiong, Tiantian Zhang, Dan Wang. A Coordinated Optimal Strategy for Voltage and Reactive Power Control with Adaptive Amplitude Limiter Based on Flexible Excitation System. Energies. 2021; 14 (16):5212.
Chicago/Turabian StyleYuwei Peng; Jiancheng Zhang; Chengxiong Mao; Hongtao Xiong; Tiantian Zhang; Dan Wang. 2021. "A Coordinated Optimal Strategy for Voltage and Reactive Power Control with Adaptive Amplitude Limiter Based on Flexible Excitation System." Energies 14, no. 16: 5212.
The multi-winding medium frequency transformer (MMFT) has attracted widespread attention, since its application in power electronic transformers can simplify the system structure and reduce the volume and weight. However, the special working conditions of MMFT due to high voltage and high power density increase the difficulty of insulation design for MMFT. For this issue, this paper presents a comprehensive analysis of electric filed characteristics for MMFT. First, the electric field model of MMFT is established using the 2-D finite element method. Based on it, the influences of connection mode, core structure, and hollow winding on the electric field characteristics of MMFT are studied, including the overall electric field distribution, maximum electric field intensity, and the electric field intensity along a fixed path. The results show that there are differences in the maximum electric field intensity for different connection modes and different core structures, which provides references for MMFT insulation design. The proposed modeling method and analysis results in this paper are important for insulation improvement of MMFT.
Pei Huang; Renjun Dian; Peng Wang; Dan Wang; Zhenxing Liu; Qi Wang. Comprehensive Analysis of Electric Field Characteristics for Multi-Winding Medium Frequency Transformer. Energies 2021, 14, 3285 .
AMA StylePei Huang, Renjun Dian, Peng Wang, Dan Wang, Zhenxing Liu, Qi Wang. Comprehensive Analysis of Electric Field Characteristics for Multi-Winding Medium Frequency Transformer. Energies. 2021; 14 (11):3285.
Chicago/Turabian StylePei Huang; Renjun Dian; Peng Wang; Dan Wang; Zhenxing Liu; Qi Wang. 2021. "Comprehensive Analysis of Electric Field Characteristics for Multi-Winding Medium Frequency Transformer." Energies 14, no. 11: 3285.
Providing sufficient damping over the full frequency range of low frequency oscillation (LFO) is a challenge in modern power systems. The flexible excitation system with two damping channels, controlled by the power system stabilizer (PSS) and the reactive power damping controller (RPDC) respectively, provides a new way to solve this issue. The controller structures of the flexible excitation system are studied, in which a novel structure is adopted in RPDC to enhance the damping over the lower-frequency range of LFO. The controller parameters design method of the flexible excitation system is also proposed: the phase compensation method is employed to design the time constants of PSS and RPDC; and the gains of them are adjusted based on their critical values. A single machine-infinite bus (SMIB) system in RTDS (real time digital system) and a system considering the doubly-fed wind generator are simulated to verify the effectiveness of the flexible excitation system on improving the power system stability.
Tiantian Zhang; Liping Cheng; Silin He; Minghao Yu; Chengxiong Mao; Dan Wang; Jiancheng Zhang; Bing Han; Zheng Tao. Optimal Design Method of Flexible Excitation System for Improving Power System Stability. IEEE Transactions on Industry Applications 2021, 57, 2120 -2128.
AMA StyleTiantian Zhang, Liping Cheng, Silin He, Minghao Yu, Chengxiong Mao, Dan Wang, Jiancheng Zhang, Bing Han, Zheng Tao. Optimal Design Method of Flexible Excitation System for Improving Power System Stability. IEEE Transactions on Industry Applications. 2021; 57 (3):2120-2128.
Chicago/Turabian StyleTiantian Zhang; Liping Cheng; Silin He; Minghao Yu; Chengxiong Mao; Dan Wang; Jiancheng Zhang; Bing Han; Zheng Tao. 2021. "Optimal Design Method of Flexible Excitation System for Improving Power System Stability." IEEE Transactions on Industry Applications 57, no. 3: 2120-2128.
This paper presents a hybrid AC/DC system constructed by multi-port energy routers (MERs), which have potential application prospects in future energy Internet. Two typical types of MER in the system are studied, and the selected main circuits is easy to realize multiple forms of power supply with high reliability, plug-and-play access of distributed generations, and high expansibility of power ports. The corresponding control and protection systems are developed to ensure the regular operation of MERs, and a smart energy management scheme is presented for the power flow management of MERs to meet the expectations of power consumers. Two MER prototypes are implemented, of which the experimental results validate the correctness of parameter design and the effectiveness of the control and energy management strategies, showing the satisfactory performance of MERs.
Bin Liu; Yuwei Peng; Jiachao Xu; Chengxiong Mao; Dan Wang; Qing Duan. Design and Implementation of Multiport Energy Routers Toward Future Energy Internet. IEEE Transactions on Industry Applications 2021, 57, 1945 -1957.
AMA StyleBin Liu, Yuwei Peng, Jiachao Xu, Chengxiong Mao, Dan Wang, Qing Duan. Design and Implementation of Multiport Energy Routers Toward Future Energy Internet. IEEE Transactions on Industry Applications. 2021; 57 (3):1945-1957.
Chicago/Turabian StyleBin Liu; Yuwei Peng; Jiachao Xu; Chengxiong Mao; Dan Wang; Qing Duan. 2021. "Design and Implementation of Multiport Energy Routers Toward Future Energy Internet." IEEE Transactions on Industry Applications 57, no. 3: 1945-1957.
Earth current generated by the operation of urban rail transit can enter into the neutral point of grounding transformer, which will result in the deterioration of transformer operation performance, and cause electrical safety problems. The neutral current for 220 kV transformers has been measured in real power system, the characteristics of DC and harmonic current are analyzed, and a novel suppression method for the DC and harmonic current simultaneously combining an active converter with a DC blocking capacitor is proposed in this paper, which solves not only the traditional DC bias problem, but also the intrusion of the harmonic current from urban rail transit. The active converter is designed to compensate harmonic voltage to suppress harmonic current, and the capacitor provides blocking for the DC current. The protection scheme in case of high fault current of neutral point is presented. The improved control method is designed to control neutral current and adjust the fundamental impedance for the requirements of relay protection. The effectiveness of the proposed method is verified by the digital simulations and the laboratory experiments based on the field working conditions, and the results demonstrate the satisfying performances.
Jinli Zhu; Chengxiong Mao; Zhaoyuan Wang; Jinfan Chen; Dan Wang; Le Luan; Yajun Qiao; Haijing Wang. A Novel Suppression Method for Grounding Transformer against Earth Current from Urban Rail Transit. IEEE Transactions on Industrial Electronics 2020, PP, 1 -1.
AMA StyleJinli Zhu, Chengxiong Mao, Zhaoyuan Wang, Jinfan Chen, Dan Wang, Le Luan, Yajun Qiao, Haijing Wang. A Novel Suppression Method for Grounding Transformer against Earth Current from Urban Rail Transit. IEEE Transactions on Industrial Electronics. 2020; PP (99):1-1.
Chicago/Turabian StyleJinli Zhu; Chengxiong Mao; Zhaoyuan Wang; Jinfan Chen; Dan Wang; Le Luan; Yajun Qiao; Haijing Wang. 2020. "A Novel Suppression Method for Grounding Transformer against Earth Current from Urban Rail Transit." IEEE Transactions on Industrial Electronics PP, no. 99: 1-1.
The ground current of rail transit contains direct and harmonic components, which will lead to many undesirable effects on substation transformer neutral points. The traditional suppression strategy can only suppress the direct current in the ground current. At the same time, the traditional switching strategy does not consider the dynamic changes of the direct ground current and may cause the direct ground current at the surrounding neutral point to passively exceed the limit. Firstly, in this paper, the change of the direct and harmonic ground current and the influence of the rail transit passenger load on ground current were analyzed based on the measurement data. Then, considering the harmonic ground current of rail transit, a suppression strategy of harmonic ground current was designed. Besides, a calculation model for neutral point direct ground current distribution was established. Finally, an optimal switching strategy of the blocking device was presented to minimize the global direct ground current and maximize the economy of overall devices. Using the test case of 220kV substations surrounding an actual metro line, the ability of suppressing the harmonic ground current was verified. Compared with conventional switching strategy, the effectiveness and correctness of the optimal strategy for the direct ground current based on blocking devices were verified.
Zhaoyuan Wang; Jinli Zhu; Chengxiong Mao; Dan Wang; Haijing Wang; Yajun Qiao. Suppression strategy for rail transit ground current in transformer neutral points. Energy Reports 2020, 6, 1079 -1089.
AMA StyleZhaoyuan Wang, Jinli Zhu, Chengxiong Mao, Dan Wang, Haijing Wang, Yajun Qiao. Suppression strategy for rail transit ground current in transformer neutral points. Energy Reports. 2020; 6 ():1079-1089.
Chicago/Turabian StyleZhaoyuan Wang; Jinli Zhu; Chengxiong Mao; Dan Wang; Haijing Wang; Yajun Qiao. 2020. "Suppression strategy for rail transit ground current in transformer neutral points." Energy Reports 6, no. : 1079-1089.
Energy router is an intelligent power electronic device that can realize the active management of power flow and provide convenient access to distributed energy resource. This paper presents the structure of an AC-DC hybrid multi-port energy router, which acts as the interface between the power consumer and the distribution network. The corresponding coordinated control strategy is developed to guarantee the regular operation of the energy router and a mode switch strategy with advanced compensation is proposed to achieve seamless transition between grid-connected mode and islanded mode. A novel and practical fuzzy logic controller considering unit-time electricity charge is proposed for the energy router to prolong battery life, to improve economic benefits of power consumers, and to smooth fluctuations of renewable energy generation or load consumption. The simulation and experimental results have validated the coordinated control and energy management strategies and demonstrated that the energy router has satisfactory performance.
Bin Liu; Weihan Wu; Chunxiao Zhou; Chengxiong Mao; Dan Wang; Qing Duan; Guanglin Sha. An AC–DC Hybrid Multi-Port Energy Router With Coordinated Control and Energy Management Strategies. IEEE Access 2019, 7, 109069 -109082.
AMA StyleBin Liu, Weihan Wu, Chunxiao Zhou, Chengxiong Mao, Dan Wang, Qing Duan, Guanglin Sha. An AC–DC Hybrid Multi-Port Energy Router With Coordinated Control and Energy Management Strategies. IEEE Access. 2019; 7 ():109069-109082.
Chicago/Turabian StyleBin Liu; Weihan Wu; Chunxiao Zhou; Chengxiong Mao; Dan Wang; Qing Duan; Guanglin Sha. 2019. "An AC–DC Hybrid Multi-Port Energy Router With Coordinated Control and Energy Management Strategies." IEEE Access 7, no. : 109069-109082.
Jie Tian; Dewang Hu; Chunxiao Zhou; Yun Yang; Weihan Wu; Chengxiong Mao; Dan Wang. Individual DC Voltage Balance Control for Cascaded H-Bridge Electronic Power Transformer With Separated DC-Link Topology. IEEE Access 2019, 7, 38558 -38567.
AMA StyleJie Tian, Dewang Hu, Chunxiao Zhou, Yun Yang, Weihan Wu, Chengxiong Mao, Dan Wang. Individual DC Voltage Balance Control for Cascaded H-Bridge Electronic Power Transformer With Separated DC-Link Topology. IEEE Access. 2019; 7 ():38558-38567.
Chicago/Turabian StyleJie Tian; Dewang Hu; Chunxiao Zhou; Yun Yang; Weihan Wu; Chengxiong Mao; Dan Wang. 2019. "Individual DC Voltage Balance Control for Cascaded H-Bridge Electronic Power Transformer With Separated DC-Link Topology." IEEE Access 7, no. : 38558-38567.
Digital-physical hybrid real-time simulation (hybrid simulation) platform integrates the advantages of both digital simulation and physical simulation by combining the physical simulation laboratory and the real-time digital simulator. Based on a 400 V/50 kVA hybrid simulation platform with 500 kVA short-circuit capacity, the hybrid simulation methodology and a Hausdorff distance based accuracy evaluation method are proposed. The case validation of power system fault recurrence is performed through this platform, and the stability and accuracy are further validated by comparing the hybrid simulation waveform and field-recorded waveform and by evaluating the accuracy with the proposed error index. Two typical application scenarios in power systems are studied subsequently. The static var generator testing shows the hybrid simulation platform can provide system-level testing conditions for power electronics equipment conveniently. The low-voltage ride through standard testing of a photovoltaic inverter indicates that the hybrid simulation platform can be also used for voltage standard testing for various power system apparatus with low cost. With this hybrid simulation platform, the power system simulation and equipment testing can be implemented with many advantages, such as short period of modelling, flexible modification of parameter and network, low cost, and low risk. Based on this powerful tool platform, there will be more application scenarios in future power systems.
Feng Leng; Chengxiong Mao; Dan Wang; Ranran An; Yuan Zhang; Yanjun Zhao; Linglong Cai; Jie Tian. Applications of Digital-Physical Hybrid Real-Time Simulation Platform in Power Systems. Energies 2018, 11, 2682 .
AMA StyleFeng Leng, Chengxiong Mao, Dan Wang, Ranran An, Yuan Zhang, Yanjun Zhao, Linglong Cai, Jie Tian. Applications of Digital-Physical Hybrid Real-Time Simulation Platform in Power Systems. Energies. 2018; 11 (10):2682.
Chicago/Turabian StyleFeng Leng; Chengxiong Mao; Dan Wang; Ranran An; Yuan Zhang; Yanjun Zhao; Linglong Cai; Jie Tian. 2018. "Applications of Digital-Physical Hybrid Real-Time Simulation Platform in Power Systems." Energies 11, no. 10: 2682.
Reliability is one of the major concerns when the electronic power transformer is employed in the field, and redundancy is a common approach to improve the reliability. For hot and cold redundancy schemes, the performance will be degraded due to the small number of power modules when the electronic power transformer is employed in the medium-voltage power grid. For the three-phase electronic power transformer, at least three redundant power modules are needed (one redundant power module per phase), which leads to a high redundancy cost. In this paper, a novel redundancy scheme is proposed. The proposed scheme can accomplish the faulty power module replacement process within tens of microseconds with nearly no transition. And only one power module and several switches are needed for three-phase redundancy, which can effectively save the redundancy cost. The proposed scheme is analyzed and supported by simulations and experimental results.
Jie Tian; Chengxiong Mao; Dan Wang; Shaoxiong Nie; Yun Yang. A Short-Time Transition and Cost Saving Redundancy Scheme for Medium-Voltage Three-Phase Cascaded H-Bridge Electronic Power Transformer. IEEE Transactions on Power Electronics 2018, 33, 9242 -9252.
AMA StyleJie Tian, Chengxiong Mao, Dan Wang, Shaoxiong Nie, Yun Yang. A Short-Time Transition and Cost Saving Redundancy Scheme for Medium-Voltage Three-Phase Cascaded H-Bridge Electronic Power Transformer. IEEE Transactions on Power Electronics. 2018; 33 (11):9242-9252.
Chicago/Turabian StyleJie Tian; Chengxiong Mao; Dan Wang; Shaoxiong Nie; Yun Yang. 2018. "A Short-Time Transition and Cost Saving Redundancy Scheme for Medium-Voltage Three-Phase Cascaded H-Bridge Electronic Power Transformer." IEEE Transactions on Power Electronics 33, no. 11: 9242-9252.
When plug-in electric vehicles (PEVs) participate in grid operation, the inter-temporal feature of PEVs charging transforms the traditional optimal power flow (OPF) problem into multiperiod OPF (MOPF) problem. In the case that the population of PEVs is huge, the large number of variables and constraints render the centralized solution technique unsuitable to solve the MOPF problem. Therefore, a distributed algorithm based on alternating direction method of multipliers (ADMM) is developed to decompose the MOPF into two update steps that are solved in an alternating and iterative style. To improve the solution efficiency, the second update step is transformed into a Euclidean projection problem by approximating the original objective with a surrogate function. Then a projection algorithm is utilized to solve the approximate problem. Numerical results show that this reformulated model obtains suboptimal solutions with small relative error, but gains considerable speedup. Furthermore, its scalability and effectiveness are tested in the 119-bus and 906-bus distribution networks.
Hua Fan; Chao Duan; Chuan-Ke Zhang; Lin Jiang; Chengxiong Mao; Dan Wang. ADMM-Based Multiperiod Optimal Power Flow Considering Plug-In Electric Vehicles Charging. IEEE Transactions on Power Systems 2017, 33, 3886 -3897.
AMA StyleHua Fan, Chao Duan, Chuan-Ke Zhang, Lin Jiang, Chengxiong Mao, Dan Wang. ADMM-Based Multiperiod Optimal Power Flow Considering Plug-In Electric Vehicles Charging. IEEE Transactions on Power Systems. 2017; 33 (4):3886-3897.
Chicago/Turabian StyleHua Fan; Chao Duan; Chuan-Ke Zhang; Lin Jiang; Chengxiong Mao; Dan Wang. 2017. "ADMM-Based Multiperiod Optimal Power Flow Considering Plug-In Electric Vehicles Charging." IEEE Transactions on Power Systems 33, no. 4: 3886-3897.
Power system simulation is an important means to study the dynamic behavior, to ensure the safety and stability, and to optimize the operation of a power grid. Pure physical simulation and digital simulation have their own advantages and disadvantages. A three-phase four-wire hybrid simulation platform integrating the advantages of both the digital simulation and physical simulation is developed by combining the physical simulation system and real-time digital simulator. The platform is rated at 400 V and 50 kVA with the short-circuit capacity of 500 kVA and can supply ten times the rated current to support the simulation of various short-circuit faults. An improved interface algorithm based on an ideal transformer model is proposed to extend the stability region of a hybrid simulation. Hybrid simulation experiments are conducted under two cases, and the comparison with the digital simulation demonstrates the performance of this platform and the potential applied to a modern power system. This platform has been equipped in a key laboratory of smart power grid technology.
Chengxiong Mao; Feng Leng; Junlin Li; Shuoting Zhang; Lidong Zhang; Ran Mo; Dan Wang; Jie Zeng; Xun Chen; Ranran An; Yanjun Zhao. A 400-V/50-kVA Digital–Physical Hybrid Real-Time Simulation Platform for Power Systems. IEEE Transactions on Industrial Electronics 2017, 65, 3666 -3676.
AMA StyleChengxiong Mao, Feng Leng, Junlin Li, Shuoting Zhang, Lidong Zhang, Ran Mo, Dan Wang, Jie Zeng, Xun Chen, Ranran An, Yanjun Zhao. A 400-V/50-kVA Digital–Physical Hybrid Real-Time Simulation Platform for Power Systems. IEEE Transactions on Industrial Electronics. 2017; 65 (5):3666-3676.
Chicago/Turabian StyleChengxiong Mao; Feng Leng; Junlin Li; Shuoting Zhang; Lidong Zhang; Ran Mo; Dan Wang; Jie Zeng; Xun Chen; Ranran An; Yanjun Zhao. 2017. "A 400-V/50-kVA Digital–Physical Hybrid Real-Time Simulation Platform for Power Systems." IEEE Transactions on Industrial Electronics 65, no. 5: 3666-3676.
Electronic power transformers (EPTs) have been identified as emerging intelligent electronic devices in the future smart grid, e.g., the Energy Internet, especially in the application of renewable energy conversion and management. Considering that the EPT is directly connected to the medium-voltage grid, e.g., a10 kV distribution system, and its cascaded H-bridges structure, the common mode voltage (CMV) issue will be more complex and severe. The CMV will threaten the insulation of the entire EPT device and even produce common mode current. This paper investigates the generated mechanism and characteristics of the CMV in a cascaded H-bridge EPT (CHB-EPT) under both balanced and fault grid conditions. First, the CHB-EPT system is introduced. Then, a three-phase simplified circuit model of the high-voltage side of the EPT system is presented. Combined with a unipolar modulation strategy and carrier phase shifting technology by rigorous mathematical analysis and derivation, the EPT internal CMV and its characteristics are obtained. Moreover, the influence of the sinusoidal pulse width modulation dead time is considered and discussed based on analytical calculation. Finally, the simulation results are provided to verify the validity of the aforementioned model and the analysis results. The proposed theoretical analysis method is also suitable for other similar cascaded converters and can provide a useful theoretical guide for structural design and power density optimization.
Yun Yang; Chengxiong Mao; Dan Wang; Jie Tian; Ming Yang. Modeling and Analysis of the Common Mode Voltage in a Cascaded H-Bridge Electronic Power Transformer. Energies 2017, 10, 1357 .
AMA StyleYun Yang, Chengxiong Mao, Dan Wang, Jie Tian, Ming Yang. Modeling and Analysis of the Common Mode Voltage in a Cascaded H-Bridge Electronic Power Transformer. Energies. 2017; 10 (9):1357.
Chicago/Turabian StyleYun Yang; Chengxiong Mao; Dan Wang; Jie Tian; Ming Yang. 2017. "Modeling and Analysis of the Common Mode Voltage in a Cascaded H-Bridge Electronic Power Transformer." Energies 10, no. 9: 1357.
High penetration of power electronic devices and nonlinear loads can negatively affect the power quality of the distribution system. The conventional method of improving the power quality is to employ an extra distribution static synchronous compensator (D-STATCOM) or an active power filter (APF) for compensating reactive power and mitigating current harmonics. This paper proposes an electronic power transformer (EPT) without the aforementioned additional equipment, which can realize multi-function coordinated operation, including active power transmission, voltage conversion, reactive power compensation, and current harmonics suppression, based on the distribution system need. The multifunctional EPT consists of three stages, namely cascaded multilevel AC/DC rectifiers, dual-active bridge (DAB) converters with medium-frequency transformers, and DC/AC inverters. The mathematical model of each stage is established and analyzed. Meanwhile, the control strategies of three stages are presented. Finally, a simulation model is built by MATLAB/Simulink to demonstrate the effectiveness of the strategy and operating principle of the proposed EPT. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Yun Yang; Chengxiong Mao; Tianliu Wei; Dan Wang; Jie Tian. Multi-function combined operation and control strategy of electronic power transformer for power quality improvement. IEEJ Transactions on Electrical and Electronic Engineering 2017, 12, 841 -849.
AMA StyleYun Yang, Chengxiong Mao, Tianliu Wei, Dan Wang, Jie Tian. Multi-function combined operation and control strategy of electronic power transformer for power quality improvement. IEEJ Transactions on Electrical and Electronic Engineering. 2017; 12 (6):841-849.
Chicago/Turabian StyleYun Yang; Chengxiong Mao; Tianliu Wei; Dan Wang; Jie Tian. 2017. "Multi-function combined operation and control strategy of electronic power transformer for power quality improvement." IEEJ Transactions on Electrical and Electronic Engineering 12, no. 6: 841-849.
Medium frequency transformers (MFTs) have achieved extensive attention since they are widely used in medium frequency energy conversion systems. Different from traditional power transformer, MFTs require special consideration of short-circuit design due to their complex fault conditions. In this study, the electromagnetic forces exerted on the windings of a 1.5 kV, 35 kW, 1 kHz MFT are investigated. A working circuit model of this MFT is set up to simulate the inrush current and short-circuit current under different fault conditions. Three-dimensional (3D) transient coupled field-circuit finite element model of this MFT is developed to study the axial and radial forces exerted on the windings. The high voltage (HV) and low voltage (LV) windings are modelled into 20 and 16 sections, respectively. Then the developed axial and radial forces exerted on the HV and LV windings under inrush current and short-circuit current are compared. Furthermore, the electromagnetic forces of two kinds of interleaved windings are evaluated. The results show that suitable interleaved winding design can reduce the electromagnetic force under short circuit. The proposed approach and analysis results in this study are essential and important for MFT short-circuit design improvement, especially interleaved windings are adopted.
Pei Huang; Chengxiong Mao; Dan Wang. Analysis of electromagnetic force for medium frequency transformer with interleaved windings. IET Generation, Transmission & Distribution 2017, 11, 2023 -2030.
AMA StylePei Huang, Chengxiong Mao, Dan Wang. Analysis of electromagnetic force for medium frequency transformer with interleaved windings. IET Generation, Transmission & Distribution. 2017; 11 (8):2023-2030.
Chicago/Turabian StylePei Huang; Chengxiong Mao; Dan Wang. 2017. "Analysis of electromagnetic force for medium frequency transformer with interleaved windings." IET Generation, Transmission & Distribution 11, no. 8: 2023-2030.
The electronic power transformer (EPT) raises concerns for its notable size and volume reduction compared with traditional line frequency transformers. Medium frequency transformers (MFTs) are important components in high voltage and high power energy conversion systems such as EPTs. High voltage and high power make the reliable insulation design of MFT more difficult. In this paper, the influence of wire type and interleaved winding structure on the electric field distribution of MFT is discussed in detail. The electric field distributions for six kinds of typical non-interleaved windings with different wire types are researched using a 2-D finite element method (FEM). The electric field distributions for one non-interleaved winding and two interleaved windings are also studied using 2-D FEM. Furthermore, the maximum electric field intensities are obtained and compared. The results show that, in this case study, compared with foil conductor, smaller maximum electric field intensity can be achieved using litz wire in secondary winding. Besides, interleaving can increase the maximum electric field intensity when insulation distance is constant. The proposed method of studying the electric field distribution and analysis results are expected to make a contribution to the improvement of electric field distribution in transformers.
Pei Huang; Chengxiong Mao; Dan Wang. Electric Field Simulations and Analysis for High Voltage High Power Medium Frequency Transformer. Energies 2017, 10, 371 .
AMA StylePei Huang, Chengxiong Mao, Dan Wang. Electric Field Simulations and Analysis for High Voltage High Power Medium Frequency Transformer. Energies. 2017; 10 (3):371.
Chicago/Turabian StylePei Huang; Chengxiong Mao; Dan Wang. 2017. "Electric Field Simulations and Analysis for High Voltage High Power Medium Frequency Transformer." Energies 10, no. 3: 371.
In this paper, to improve the dynamic performance of DFIG-based WT, a NADRC technology is proposed. The proposed NADRC can actively estimate and compensate the plant internal dynamics and external disturbances in real time. Therefore, it improves the tracking performance of the rotor current without any overshoot and steady-state error, and enhances the fault ride-through capability of DFIG-based wind turbine. Compared with the proportional PI control, the proposed NADRC during grid fault can significantly suppress the peak values of stator and rotor currents and DC-link voltage, and decrease the oscillation time of electromagnetic torque. Moreover, the proposed NADRC has a characteristic of one-parameter tuning by using the parameterization technique of controller, and parameter tuning of NADRC is only determined by the rise time of the system step response. A series of simulations for various cases on a 1.5-MW DFIG-based wind turbine are implemented, and the results validate the stability of the proposed NADRC and the strong robustness against the plant internal dynamics and external disturbances.
Shihong Gao; Chengxiong Mao; Dan Wang; Jiming Lu. Dynamic performance improvement of DFIG-based WT using NADRC current regulators. International Journal of Electrical Power & Energy Systems 2016, 82, 363 -372.
AMA StyleShihong Gao, Chengxiong Mao, Dan Wang, Jiming Lu. Dynamic performance improvement of DFIG-based WT using NADRC current regulators. International Journal of Electrical Power & Energy Systems. 2016; 82 ():363-372.
Chicago/Turabian StyleShihong Gao; Chengxiong Mao; Dan Wang; Jiming Lu. 2016. "Dynamic performance improvement of DFIG-based WT using NADRC current regulators." International Journal of Electrical Power & Energy Systems 82, no. : 363-372.
This paper presents the design and development of a three-phase 10-kV/400-V 500-kVA electronic power transformer (EPT). The power circuit is designed in a modular fashion, i.e., the main circuit consists of many identical ac-dc-dc-ac modules (abbreviated as power modules). Each power module consists of a high-voltage power cell, a low-voltage power cell (LVPC), a medium-frequency isolation transformer, and a filter. The corresponding control and protection system is developed. A special three-stage startup strategy is designed to shorten the startup time and reduce the startup inrush current. The negative-sequence current compensation is introduced in the input stage to handle the unbalanced loads. To keep the dc-link voltages balanced, an individual dc voltage balancing controller based on regulating the output power of each parallel LVPC is proposed. The detailed control hardware design and software implementation are discussed. The functions of this 10-kV EPT prototype are verified through the laboratory and field tests. The results are shown in this paper. Currently, the prototype is operating in the industrial power grid.
Dan Wang; Jie Tian; Chengxiong Mao; Jiming Lu; Yuping Duan; Jun Qiu; Huihong Cai. A 10-kV/400-V 500-kVA Electronic Power Transformer. IEEE Transactions on Industrial Electronics 2016, 63, 6653 -6663.
AMA StyleDan Wang, Jie Tian, Chengxiong Mao, Jiming Lu, Yuping Duan, Jun Qiu, Huihong Cai. A 10-kV/400-V 500-kVA Electronic Power Transformer. IEEE Transactions on Industrial Electronics. 2016; 63 (11):6653-6663.
Chicago/Turabian StyleDan Wang; Jie Tian; Chengxiong Mao; Jiming Lu; Yuping Duan; Jun Qiu; Huihong Cai. 2016. "A 10-kV/400-V 500-kVA Electronic Power Transformer." IEEE Transactions on Industrial Electronics 63, no. 11: 6653-6663.
This study presents a hybrid compensator based on distribution static synchronous compensator (DSTATCOM) and thyristor switched capacitor (TSC), which is intended to continuously compensate reactive power with higher quality and lower cost. The proposed coordination control strategies, in essence, are to continuously assign the reactive power between the DSTATCOM and the TSC. Usually, the fast response characteristic of the DSTATCOM will be lost for that the output of the DSTATCOM is limited by the conventional coordination control strategy. In order to improve the transient performance of hybrid compensator, the fast voltage control strategy is proposed to fast respond to the demand, and reactive power reserve control strategy is proposed to restore the capacity. The operation principle, control algorithm, and design procedure of a prototype are described. Laboratory tests and field tests have validated that the performance of the compensator is satisfactory, and the cost reduction of hybrid compensator is significant.
Tianliu Wei; Chengxiong Mao; Jiming Lu; Dan Wang; Qiuyuan Wang; Weiwei Wu. Low cost hybrid reactive power compensator using coordination control strategies. IET Generation, Transmission & Distribution 2016, 10, 1805 -1814.
AMA StyleTianliu Wei, Chengxiong Mao, Jiming Lu, Dan Wang, Qiuyuan Wang, Weiwei Wu. Low cost hybrid reactive power compensator using coordination control strategies. IET Generation, Transmission & Distribution. 2016; 10 (8):1805-1814.
Chicago/Turabian StyleTianliu Wei; Chengxiong Mao; Jiming Lu; Dan Wang; Qiuyuan Wang; Weiwei Wu. 2016. "Low cost hybrid reactive power compensator using coordination control strategies." IET Generation, Transmission & Distribution 10, no. 8: 1805-1814.
A multiphase motor has several major advantages, such as high reliability, fault tolerance, and high power density. It is a critical issue to develop a reliable and efficient multiphase motor drive system. In this paper, a transformerless voltage source converter-based drive system for a medium-voltage (MV) multiphase motor is proposed. This drive converter employs cascaded H-bridge rectifiers loaded by H-bridge inverters as the interface between the grid and multiphase motor. The cascaded H-bridge rectifier technique makes the drive system able to be directly connected to the MV grid without the phase-shifting transformer because it can offset the voltage level gap between the MV grid and the semiconductor devices, provide near-sinusoidal AC terminal voltages without filters, and draw sinusoidal line current from the grid. Based on a digital signal processor (DSP), a complete improved Phase Disposition Pulse Width Modulation (PD-PWM) method is developed to ensure the individual DC-link capacitor voltage balancing for enhancing the controllability and limiting the voltage and power stress on the H-bridge cells. A downscaled prototype is designed and developed based on a nine-phase motor. The experimental results verify the excellent performances of the proposed drive system and control strategy in steady-state and variant-frequency startup operations.
Dan Wang; Jiawei Yang; Zhu Chen; Chengxiong Mao; Jiming Lu. A Transformerless Medium Voltage Multiphase Motor Drive System. Energies 2016, 9, 323 .
AMA StyleDan Wang, Jiawei Yang, Zhu Chen, Chengxiong Mao, Jiming Lu. A Transformerless Medium Voltage Multiphase Motor Drive System. Energies. 2016; 9 (5):323.
Chicago/Turabian StyleDan Wang; Jiawei Yang; Zhu Chen; Chengxiong Mao; Jiming Lu. 2016. "A Transformerless Medium Voltage Multiphase Motor Drive System." Energies 9, no. 5: 323.