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A unified dynamic phasor modeling and operating characteristic analysis of electrical system of MMC

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2016年第20期36卷 5479-5491页

作者： Lu, Xiaojun Lin, Weixing An, Ting Li, Yunfeng Wen, Jinyu Yao, Wei State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuhanHubei Province430074 China Global Energy Interconnection Research Institute Changping District Beijing122000 China

A unified dynamic phasor model (DPM) for electrical system of modular multilevel converter (MMC) under the rotating frame was proposed. The model considers the AC voltage components in the rotating frame and the DC voltage as electrical inputs, takes the fundamental frequency and second harmonic components of modulation indices as the control inputs. By individually modeling the controller, the internal dynamics of MMC and the dynamics of external electrical system, the proposed dynamic phasor model is capable of conveniently interconnecting models of MMC electrical dynamics, controllers and external electrical system. The dynamic phasor model of MMC was therefore normalized. By setting the derivative terms in the DPM to zero, static phasor model for the electrical system of MMC was achieved. By linearizing the DPM around the steady-state operating point, small signal model for the electrical system of MMC was obtained. As a result, the proposed DPM unified the dynamic phasor model, static phasor model and small signal model of MMC. Based on the obtained static phasor model of the MMC, an open loop circulating current suppressing control (CCSC) strategy and a method of analytically analyzing the operating characteristic of MMC considering various constraints were proposed. Simulations on PSCAD/EMTDC verified the accuracy of the dynamic phasor model, the efficacy of the open loop CCSC strategy and the different constraints on the PQ operation zone of a MMC. © 2016 Chin. Soc. for Elec. Eng.

关键词： Controllers

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Economic Dispatch Considering Correlations of Solar and Load

Economic Dispatch Considering Correlations of Solar and Load

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The 2015 2nd International Conference on engineering technology and Application

作者： Xiaohong Ran Shihong Miao Hao Xu State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

An economic dispatch considering correlation between solar and load is *** probabilistic density functions of solar and load are introduced,and then solar-load bivariate normal distribution is established based on multivariate statistical analysis *** loss load risk model of typical scenario is constructed and the economic dispatch model is established,a-superquantile is used to describe the risk constraint,Monte Carlo simulation and analytic method were combined to solve the optimization *** show that proposed method can describe the impact of correlation of solar and load on economic dispatch at different confidence levels.

关键词： correlation risk model economic dispatch unit commitment

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Mode-Coupling Analysis of Parametric Decay Instability in Magnetized Plasmas

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Plasma Science and technology 2014年第9期16卷 809-814页

作者：袁媛江中和郭伟欣孙新锋胡希伟 State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability （PDI） in magnetized plasmas, and in view of mode-coupling, we can obtain all the possible PDI channels. By solving the nonlinear equations with a mode-coupling method, we obtain the growth rate of the PDI, of which all of the three waves are ordinary mode （O-mode） or extraordinary mode （X-mode） wave. Under the dipole approximation, an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained. According to the existence conditions of three X-mode waves, this kind of instability might exist in ECRH with the second harmonic X-mode wave.

关键词： magnetized plasma parametric decay instability mode-coupling theory,growth rate

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Design Procedure of Dual-Stator Spoke-Array Vernier Permanent-Magnet Machines

Design Procedure of Dual-Stator Spoke-Array Vernier Permanen...

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IEEE Transactions on Industry Applications

作者： Li, Dawei Qu, Ronghai Xu, Wei Li, Jian Lipo, Thomas A. State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan China Department of Electrical and Computer Engineering University of Wisconsin-Madison MadisonWI United States

The dual-stator spoke-array vernier permanent-magnet (DSSA VPM) machines proposed in the previous papers have been proven to be with high torque density and high power factor. However, the design procedure on the DSSA VPM machines has not been well established, and there is little design experience to be followed, which makes the DSSA VPM machine design quite difficult. This paper presents the detailed DSSA VPM machine design procedure including decision of design parameter initial values, analytical sizing equation, geometric size relationship, and so on. In order to get reasonable design parameter initial values which can reduce the number of design iteration loop, the influence of the key parameters, such as rotor/stator pole combination, slot opening, magnet thickness, etc., on the performances is analyzed based on the finite-element algorithm (FEA) in this paper, and the analysis results can be regarded as design experience during the selection process of the initial values. After that, the analytical sizing equation and geometric relationship formulas are derived and can be used to obtain and optimize the size data of the DSSA VPM machines with little time consumption. The combination of the analytical and FEA methods makes the design procedure time-effective and reliable. Finally, the design procedure is validated by experiments on a DSSA VPM prototype with 2000 N · m. © 2015 IEEE.

关键词： Design Electric machinery Electric power factor Finite element method Iterative methods Machine design Magnets Permanent magnets Stators Analytical sizings Design procedure Dual stator Finite element algorithms (FEA) Geometric relationships High torque density Permanent magnet machine Sizing equations

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DFIG-based Wind Turbines with Virtual Synchronous Control: Inertia Support in Weak Grid

DFIG-based Wind Turbines with Virtual Synchronous Control: I...

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IEEE Power and Energy Society General Meeting

作者： Shuo Wang Jiabing Hu Xiaoming Yuan State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

ISBN: (纸本)9781467380416

This paper presents virtual synchronous control (VSynC) for DFIG-based wind turbines (WTs) in particular when integrated into weak AC grid with low SCR. Different from the typical vector control (VC) based on the widely-used phase-locked loop (PLL) technique, VSynC synchronizes DFIG with the grid directly through active power control, which effectively avoids the difficulties associated with PLL in weak AC grid. Eigenvalue analysis shows that the VSynC-based DFIG displays pronounced superiority in stability when accessing low-SCR AC grid. In such case, the DFIG's power transfer capability is not limited, which means the maximum theoretical power transmittable, viz., 1.0 pu, can be achieved even when SCR is decreased to 1.0. More importantly, the VSynC also makes DFIG provide the desired inertial response naturally for dynamic frequency support. Comparisons between the VSynC and the typical VC-based inertia control are also performed, and simulation results demonstrate the superior performance of VSynC-based DFIG attached to weak AC grid.

关键词： DFIG Inertial response PLL Stability Synchronization SCR Virtual synchronous control Wind turbine Weak grid

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Application of Field-Circuit Coupled FEM in the Design of A HTS Controllable-Reactor

Application of Field-Circuit Coupled FEM in the Design of A ...

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IEEE International Conference on Applied Superconductivity and electromagnetic Devices

作者： Shi Feng Shen Yue Jin Tang Li Ren Hong Da Dong Xiang Zhao Zuo Shuai Wang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

ISBN: (纸本)9781467381086

An electromagnetic design method of HTS-CR is proposed in which the field-circuit coupled finite element method (FCC-FEM) is introduced. Tests of both the steady volt-ampere characteristic and the DC critical current of HTS windings of a HTS-CR prototype that is made with the FCC-FEM are done. The results agree well with calculations, which verifies the reliability of the electromagnetic design method. With the above mentioned design method, design parameters and calculation results of the 35 kV HTS-CR are presented.

关键词： Field-circuit coupled Critical current Controllable reactor High temperature superconductivity

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Feedforward Current Reference Control for DFIG During Grid Faults

Feedforward Current Reference Control for DFIG During Grid F...

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Annual Conference of the IEEE Industrial Electronics Society

作者： Donghai Zhu Xudong Zou Qingjun Huang Shiying Zhou Xiaolu Gao Yong Kang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

ISBN: (纸本)9781479917631

For doubly fed induction generation (DFIG) based wind turbine, large electromotive force will be induced in the rotor circuit under severe grid faults, and it usually far exceeds the DC-bus voltage. In that case, it is necessary to inject transient and negative-sequence components into rotor current reference to fulfill controllable low-voltage ride through (LVRT). On the synchronous reference frame of vector control system, such current references are 50 Hz and 100 Hz AC items, respectively. Thus, the classical proportional-integral (PI) controller cannot accurately track this AC reference. To solve this problem, a feedforward current reference (FFCR) control scheme is proposed to improve the tracking capability of AC reference. Hence, it unearths the characteristics of such reference. The proposed FFCR control scheme will not alter the stability of original current loop. Furthermore, it has strong robustness for frequency fluctuations of grid voltage and DFIG parameters drift. Finally, simulation and experimental results are presented to demonstrate the effectiveness of the proposed control scheme.

关键词： AC reference Doubly fed induction generator (DFIG) Feedforward current reference (FFCR) Low-voltage ride through (LVRT) Reference tracking

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A study on the mechanism of ring-shape structure in the atmospheric pressure plasma jets

A study on the mechanism of ring-shape structure in the atmo...

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IEEE International Conference on Plasma Science (ICOPS)

作者： Yuan Fu YuBin Yue Xian X. Lu State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan Hubei CN State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan Hubei China

Summary form only given. Ring-shape is one of the feature characteristics of plasma bullet. However regarding the mechanism of the ring-shape structure of the plasma bullet, it is still not clear. In this paper, a series of special designed experiments are carried out to investigate the mechanism of the ring-shape structure of the plasma bullet. The typical ring-shape structure can be seen in Fig. l. In these experiments, the effect of the surface discharge and the effect of the surrounding gas diffusion are studied, thus the effect of Penning ionization can be separated. lt is found that both the diffusion of the surrounding air and the surface discharge play important roles in the forming of the ring-shape structure.

关键词： Plasmas Shape Surface discharges Discharges (electric) electromagnetics Ionization Plastics

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Research of stator displacement technique in multistage axial-flux permanent magnet machines

Research of stator displacement technique in multistage axia...

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International Conference on Magnetics (INTERMAG)

作者： X. Wei K. Yang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuHan

Axial flux permanent-magnet machines have gained popularity in the last few decades because of their higher torque at low speed and better power density compared with radial flux machine, moreover, due to its inherently short axial length, they find applications where the used conventional PM machines are not appropriate, such as hybrid traction motors. However, the major undesired effects are the cogging torque due to high frequency flux pulsation caused by air gap reluctance variation and the lack of field weakening capability due to a fixed magnetic excitation which limits the drive's maximum speed and becomes a significant limitation for both radial and axial flux PM machines. In this paper, a new multistage axial flux permanent magnet will be proposed, and based on the multistage axial flux permanent magnet synchronous machine (M-AFPM), the stator displacement technique will result in a multi-phase machine with little mutual inductance between two stators and improve the torque density and quality, moreover, it can reduce the cogging torque by half at best, and a new switch-phase connection technique combine the stator displacement is proposed for extending the flux-weakening capability. The performance of the multi-phase M-AF-PM will be studied in this paper by the 3D-FEA. Based on a 2kW-1000rpm 10-pole 12-open-slot prototype with stator displacement, the experimental study will is developed. And the comparison between the experiments and 3D-FEA results will be proposed in this paper.

关键词： Stator windings Torque Forging Switches Synchronous motors Switching circuits

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Operating and control of cascaded photovoltaic systems suffering module-mismatch 7

Operating and control of cascaded photovoltaic systems suffe...

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7th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2015

作者： Wang, Cheng Zhang, Kai Liu, Liming Liu, Wenxin State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan Hubei Province430074 China ABB Inc. Raleigh United States Electrical and Computer Engineering Lehigh University BethlehemPA18015 United States

ISBN: (纸本)9781467371506

Modular cascaded multilevel converter is a promising option for high power solar photovoltaic (PV) system due to its modularity, scalability, and distributed maximum power point tracking (MPPT) capability, etc. Nevertheless, inherent mismatch and varied operating conditions (both called module-mismatch) are still the issues to be disclosed. Asymmetrical active power harvesting among individual PV converter modules resulting from module-mismatch will fluctuate dc voltages and polarize the distribution of the alternating terminal voltage and may derivatively cause over-modulation or even destroy the system stability. In this paper, a novel modulation method for cascaded modular multilevel converter with two modes which are low-loss mode for normal operation and extended mode for module-mismatch operation is firstly proposed. With the former mode, the switching times are reduced greatly and then low the switching loss. When it is encountered by module-mismatch, extended mode is able to re-distribute power and then to balance dc-link voltages. Then a reactive power compensation algorithm (RPCA) is analyzed and applied to get a larger operating range based on the proposed modulation method. Finally, a 3MW/12kV system with the proposed modulation and control strategy is developed in Matlab/Simulink platform. Simulation results are presented to demonstrate the effectiveness of the proposed technologies. © 2015 IEEE.

关键词： Modulation

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