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Wind Power Generation

Experimental Study on Energy Coupling From Lightning to Wind Turbines Based on Artificial Triggered Lightning

SHI Guangquan;ZHANG Yijun;CHEN Shaodong;ZHANG Yang;ZHENG Dong

High Voltage Engineering,2020,Vol 46,No. 01

【Abstract】 In order to study the energy coupling characteristics from lightning to wind turbines, tests were designed and carried out in Guangzhou Field Experiment Base for Lightning Research and Testing of China Meteorological Administration. The triggered lightning current, induced voltage, and current inside the wind turbine tower were measured during an artificially triggered lightning experiment on July 30, 2011. The triggered lightning current measured in the experiment belongs to precursor pulse current with damped oscillation waves. The analyses show that the pulse amplitude of the precursor pulse current can reach 850–1 162.5 A; the spectrum is a single peak curve; the amplitude monotonically rises rapidly and reaches the peak value at the point of 351.875 kHz; then, the amplitude attenuates monotonically and rapidly; the energy of precursor pulse current mainly concentrates on the low frequency range of 0–800 kHz. The peak value of induced voltage in phase line L 2 of generator inside the wind turbine tower reaches −8.876 kV; the peak value of induced voltage in controlling line reaches 2.39 kV; the peak value of induced current in the generator’s phase L 1–L 3 circuit is 1.118 kA; the peak value of induced current in the twisted pair laying circuit is only −60.55 A. The induced voltage and current in the electronic and electrical circuits inside the wind turbine towers may exceed the insulation level of terminal equipment and cause damage when lightning occurs. High-permeability material can be used to shield the low frequency magnetic field caused by lightning. The energy coupling from lightning to signal lines can be reduced to the lowest level through the twisted pair wiring mode.

Collaborative Control Strategies for Multi-channel Three-level Wind Energy Conversion System

WANG Yibo;WANG Zheng;WEN Congjian;CHENG Ming

Proceedings of the CSEE,2019,Vol 39,No. 02

【Abstract】 The control strategies of multi-channel diode neutral-point-clamped 3L wind power generation system were investigated, including the control strategies on machine side and grid side under normal condition and fault-tolerant operation under faults in machine windings and devices. The multiphase permanent magnet generator was adopted on machine side. The vector control scheme was proposed based on optimum torque control and vector space decoupling (VSD) on machine side. In particular, a decoupled VSD switching strategy was proposed for multi-‌channel 3L converter. Hence, the voltage control method with feedforward compensation was designed on torque-generating plane, and the closed-loop proportional resonant controller was designed on harmonic plane, which can suppress the harmonic current components caused by asymmetry in machine parameters and harmonics in back EMF. The configuration of paralleled 3L converters was used on grid side, where the control schemes of reactive power regulation, DC link voltage control and circulating current suppression using zero-sequence voltage injection were designed. Besides, fault-tolerant control strategies were discussed for faulty conditions of multi-‌channel 3L wind power generation system. Finally, the experiments were presented to verify the validity of the proposed control schemes.

Study on Transient Whole-process and Control Strategy of Stator Flux Linkage in Doubly-fed Induction Generator with Asymmetric Voltage Swell

SUN Liling ;WANG Yanjuan

High Voltage Engineering,2019,Vol 45,No. 07

【Abstract】 Conventional studies on the high voltage ride-through problem of doubly-fed induction generator (DFIG) usually focus on the transient characteristics during voltage swell faults and ignore the dynamic changes of stator flux linkage after fault recovery. We study the electromagnetic transient whole-process at grid voltage asymmetric swell and fault removal. To analyze the complexity of phase sequence separation for traditional de-excitation control, we propose a reverse current tracking control strategy without flux linkage and system parameters. The simulation results verify the correctness of the theoretical analysis. The proposed control strategy accelerates the decay rate of the transient flux and suppresses the pulsation of the electromagnetic torque.

The numerical study of electrothermal de-icing cycle controlled method for wind turbine blades

SHU Lichun;YANG Chen;HU Qin;JIANG Xingliang;LI Hantao;YANG Dachuan;YANG Hang

Proceedings of the CSEE,2018,Vol 38,No. 24

【Abstract】 The traditional electrothermal de-icing methods have some defects with long heating time and low de-icing efficiency because of the conductive slip rings’ power limit. To explore the better de-icing effect, a new method-cycle controlled de-icing method was proposed. Based on 300 kW wind turbine located in the Xuefeng Mountain Icing Test Station of Chongqing University, a 2-D de-icing model of fluid and thermal field was purposed according to the blade element theory, turbulence theory and heat and mass transfer theory. Temperature sensors were installed on the blade surface to monitor the change of ice temperature. Results show that ice temperature increases and then decreases in cycle. When the single heating time is at 8.5 s–9.5 s, the de-icing time reaches the lowest value. The de-icing power density increases follow the rise of blade radius. Compared with the sustained heating de-icing method, the de-icing energy consumption of de-icing cycle controlled method is reduced by 25.9%, which can achieve the purpose of saving energy and high efficiency.

Research on the Performance of the Lightning Protection System With Overlying Conductors on the Tip of the Wind Turbine Blades

HE Tianyu;CHEN Weijiang;HE Hengxin;SHI Weidong;BIAN Kai;LI Xinkai;XIANG Nianwen;HUANG Shengxin;GU Jianwei;FU Zhong

Proceedings of the CSEE,2018,Vol 38,No. 18

【Abstract】 The wind power system has always focused on the problem of lightning protection of wind turbine blades because of the increase of the capacity of wind turbines; the tower’s height and the length of the blades also increase a lot; and the problem of the lightning protection failure of the existing blade lightning-flashing systems has become prominent as well. In order to solve the lightning strike breakdown problem of GFRP blade composites, we propose a design scheme of the LPS covering the strip leading/tailing edge, which can reduce the electric field strength of the down conductor surface inside the blade and reduce the probability of the discharge of the down conductor causing the external discharge of the blade. And a three-dimensional lightning strike leader development model for wind turbines was established, and the protective effects of the LPS of the blade with different outer conductor lengths and under different operating conditions were calculated and analyzed. Combined with the field operation data, the optimal design length of the outer conductor was determined as 12% of the total blade length, which at this time can reduce the lightning accident by 92%. The simulation test of the discharge breakdown of the blade under lightning/operational impact was carried out, and the discharge breakdown probability of the blade when the outer conductor was laid and not covered was compared. The experimental results showed that the overlaying conductors can effectively receive the downward leader to protect the blade from being penetrated in its laying range, but the protection efficiency would decline sharply when the downward leader developed outside the laying range. Simultaneously the protecting effectiveness and the limitations of the LPS with overlaying conductors under different operation conditions were also verified.

A study on regional extreme precipitation events and the exposure of population and economy in China

JING Cheng ;JIANG Tong ;WANG Yanjun ;CHEN Jing ;JIAN Dongnan ;LUO Lanxin ;SU Buda

Acta Meteorologica Sinica,2016,Vol 74,No. 04

【Abstract】 Based on daily precipitation data (1960–2014) collected at 771 meteorological stations over China, the 95 th percentile of effective precipitation is selected to be the extreme precipitation threshold. A regional precipitation event is identified to be an extreme precipitation event if it exceeds the threshold over a continuous area at a given time scale. By taking into account the spatial and temporal continuity characteristics of extreme precipitation events, the Intensity-Area-Duration (IAD) method is applied to study the feature of regional extreme precipitation event at different durations and the population/GDP exposed to extreme precipitation events. The research results show that: (1) regional extreme precipitation events with maximum relative intensity mainly occurred in three periods: 1960–1968, 1991–1999 and 2006–2013; (2) the centers of extreme precipitation events are largely distributed in Northeast China and to the south of the Yangtze River, while single-day extreme precipitation events mainly occurred in the northern region and multi-day extreme precipitation events mostly occurred in the southern region; (3) the areal coverage of extreme precipitation events has increased significantly during 1960–2014, but no obvious change can be detected for the relative intensity of extreme events; (4) the population and GDP exposed to extreme precipitation events have shown a significant increasing trend. The population exposed to extreme precipitation events reached 24.08 million people/d in 1983, and the GDP exposed to extreme events reached 2 billion yuan/d in 1998.

Efficiency Optimization of Optimum Torque Maximum Power Point Tracking Based on Gradient Approximation for Wind Turbine Generator System

LIU Jizhen;MENG Hongmin;HU Yang

Proceedings of the CSEE,2015,Vol 35,No. 10

【Abstract】 The efficiency of the conventional optimum torque maximum power point tracking (MPPT) algorithm is reduced by large rotational inertia, and the transient time of the control system becomes longer. The problem was analyzed by studying the mechanism of wind turbine. A novel optimum torque MPPT optimization algorithm was proposed to reduce the transient process time caused by high rotational inertia. The solution presented here used gradient estimation to compensate electromagnetic torque reference. A small signal model was presented with a doubly-fed induction generator based wind turbine for the performance analysis of closed-loop poles, step response and frequency–domain characteristics. From the analysis and simulation results, the novel algorithm combines stability of conventional method and high response rate of tip–speed ratio method, and has good stability, dynamic behavior and high efficiency.

Research on Improvement of Output Characteristics of the Flux-Concentrating Field-Modulated Permanent-Magnet Wind Power Generator

LI Xianglin;CHENG Ming;CHAU K.T.

Proceedings of the CSEE,2015,Vol 35,No. 16

【Abstract】 Based on the operating principle analysis of the field-modulated permanent-magnet (FMPM) machine, its power-size equation and armature reaction reactance voltage drop expression were theoretically derived for finding methods to improve the output characteristics of this kind of machine. A new outer-rotor flux-concentrating FMPM machine topology was also presented. By using the 2-D finite element analysis (FEA), the proposed flux-concentrating and existing surface-mounted FMPM machines with different pole-slot combinations were modeled and compared, aiming at revealing the effect of magnetic circuit configuration and pole-slot combination on the phase inductance and output characteristics. An 18-slot/8-pole flux-concentrating FMPM prototype was developed, and experiments were given to verify the validity of theoretical analysis and simulation results. The results show that the spoke-magnet arrangement and advisable pole-slot combination make the proposed machine offer improved features of low voltage regulation and robust output characteristics.

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