Hefei Sungrow Power Supply

Hefei, China

Hefei Sungrow Power Supply

Hefei, China
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Xie Z.,Hefei University of Technology | Xu Z.,Hefei University of Technology | Zhang X.,Hefei University of Technology | Yang S.,Hefei University of Technology | Wang L.,Hefei Sungrow Power Supply
IEEE Transactions on Industrial Electronics | Year: 2017

This paper analyzes and simulates wind shear and tower shadow effects in doubly-fed induction generators, which are known to induce a low-frequency oscillation. Such oscillation is called a 3p oscillation, which can cause shaft torsion load aggravation and shaft torque oscillation, it inevitably lead to electromagnetic torque and power fluctuation in the generator and further affect the whole wind power system. By analyzing a two-mass model, it can be known that a flexible drive train has a low-damping characteristic and an amplification of the input of low-frequency wind torque disturbances. Based on this point, this paper presents a new control scheme to restrain 3p oscillation is presented, which is a damping torque observation. A novel torque observer is designed to ascertain the required damping torque. A small-signal model is established for the system and used to analyze the system's static and dynamic characteristics. The effectiveness of the proposed strategy is finally verified by simulation and experimental results. © 2017 IEEE.


Zhang X.,Hefei University of Technology | Chen P.,Hefei University of Technology | Yu C.,Hefei University of Technology | Li F.,Hefei University of Technology | And 2 more authors.
IEEE Transactions on Power Electronics | Year: 2017

The high-power grid-connected inverters with LCL filters have been widely used. Current control plays a key role in the grid-connected inverter control system. To cope with the inherent resonance of the LCL filter, active damping (AD) methods are usually employed. However, the AD performance is impaired by control delays which are introduced in the digital control implementation process. Besides, the lag phase due to control delays limits the system bandwidth and stability margin. The effects of control delays are more noteworthy in the high-power grid-connected inverter due to its low switching frequency. This paper investigates the current control strategy based on multisampling for the high-power grid-connected inverter with the LCL filter. First, the multisampled AD scheme is studied, which can reduce control delays effectively and improve AD performance. Besides, the multisampled control without additional damping whether passive or active is researched. Through the inverter-side current feedback, the system can realize single-current-loop control based on multisampling. Thus, the control system is simplified and it can be stable, and achieve better dynamic performance. Finally, experimental results show that the proposed control schemes are effective. © 1986-2012 IEEE.


Liu F.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | Wang Z.,Nanjing University of Aeronautics and Astronautics | Wang Z.,Hefei Sungrow Power Supply | Mao Y.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | And 2 more authors.
IEEE Transactions on Power Electronics | Year: 2014

In the renewable hybrid power system, multiple-input converters (MICs) serve as the interface of several sources with a load, and provide the energy to the load simultaneously or individually, which can optimize the utilization of sources, simplify the system configuration, and reduce the overall cost. In the applications with isolated requirement, available MICs usually have complex configuration and numerous transformer windings. In this paper, a family of asymmetrical half-bridge double-input converters (DICs) adopting pulsating voltage source cells (PVSCs) for low power applications is proposed. Compared with available isolated DICs, the proposed converters have advantages of simple architecture, soft-switching realization, and high conversion efficiency. In this paper, the derivation and feasible control strategy for the proposed converters are illustrated. Specifically, the operation principle of DIC composed of two buck PVSCs is analyzed. Finally, theoretical analysis is validated by the experimental results from a 240 W prototype. © 2013 IEEE.


Zhang X.,Hefei University of Technology | Guo L.,Hefei University of Technology | Yang S.,Hefei University of Technology | Cao R.,Hefei Sungrow Power Supply
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

The speed sensorless control of permanent magnet synchronous generators, which is based on second order sliding mode observers, needs low-pass filters and compensators. Therefore the complexities of these systems are increased and the estimated rotor positions are heavily influenced by the estimated speed errors. Hence, a full order sliding mode observer based on active back electromotive force was proposed. Because of the second order low pass filter characteristic of the observer, the high-frequency sliding noise contained in the active back electromotive force can be filtered without the addition of another low-pass filter. Then a phase locked loop can be used to get the rotor position directly and speed sensorless control can be fulfilled. In addition, through the reasonable design of the sliding mode gain, the robustness of the estimated rotor position for the estimated speed error can be improved. The simulation and experimental results verify the effectiveness of the proposed algorithm. © 2014 Chin. Soc. for Elec. Eng.


Xie D.,Hefei University of Technology | Zhang X.,Hefei University of Technology | Cao R.,Hefei Sungrow Power Supply
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

The function of islanding detection is required for the grid-connected inverter-based distributed generation system due to safety reasons and to maintain the quality of power supply. Passive methods have a large non detection zone and the detecting time is long, while active schemes have negative influence on power quality, so a novel passive islanding detection method was proposed. In this method, wavelet transform was adopted to extract feature vectors from the voltage of point of common coupling (PCC) point and the output current of inverter, and then pattern recognition was exerted by BP neural network to determine whether there was an island phenomenon. The simulation and experiment results show that this method is faster than the traditional passive methods in islanding detection, and the non-detection zone is smaller. At the same time, because no disturbance was added to the control signal in the method, there isn't a negative impact on power quality. The method overcomes the shortcoming of active methods and has high accuracy and reliability. © 2014 Chin. Soc. for Elec. Eng.


Zhang X.,Hefei University of Technology | Qu T.,Hefei University of Technology | Xie Z.,Hefei University of Technology | Cao R.,Hefei Sungrow Power Supply
2011 2nd International Conference on Mechanic Automation and Control Engineering, MACE 2011 - Proceedings | Year: 2011

With the rapid increase of wind farms especially large offshore wind farms, a new problem associated with the response of doubly fed induction generator to temporary overvoltage has arisen. This paper develops a theoretical analysis of the dynamic behavior during symmetrical three phase voltage swell. Overvoltage may lead to reversal of power in the line side converter. Simulation results are in good agreement with those obtained theoretically. © 2011 IEEE.


Xie Z.,Hefei University of Technology | Zhang X.,Hefei University of Technology | Song H.,Hefei University of Technology | Yang S.,Hefei University of Technology | Cao R.,Hefei Sungrow Power Supply
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

The control strategy of doubly fed induction generator (DFIG) under grid voltage dips has long been a focus of research and development, grid voltage swells will also cause a lot of problems to DFIG based wind turbines. In order to study the characteristic and control strategy of high voltage ride through (HVRT) of DFIG, this paper analyzes the dynamic behavior of DFIG during grid voltage swells. Based on the above analysis, it is found that the active resistance can effectively suppress the rotor current and torque oscillation, avoiding the operation of Crowbar circuit. As to the different speed and grid voltage swell ratios, this paper proposes variable damping based control strategy, enhancing DFIG's HVRT capability compared with grid voltage dips. Simulation and experimental results verify the effectiveness of the variable damping based control strategy. © 2012 State Grid Electric Power Research Institute Press.


Yang S.,Hefei University of Technology | Zhan Q.,Hefei University of Technology | Zhang X.,Hefei University of Technology | Guo L.,Hefei University of Technology | Zhou Y.,Hefei Sungrow Power Supply
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2014

The permanent magnet synchronous motor (PMSM) used in wind turbine and electric vehicle situations usually has to directly track the torque command issued by the main control system. As a matter of fact, however, no torque test components such as a torque sensor is available in an actual system. So the exact acquisition of the observed torque is of utmost importance for the torque control system. To enhance the torque observer performance, this paper proposes a real-time stator flux linkage observation method based on a minimum extended flux linkage observer, through which the stator flux linkage and the electrical torque are calculated. The proposed stator flux linkage observer is not only free from the flaws of the traditional pure integral strategy, such as saturation, phase shift, amplitude deviation, and so on, but also, as a pure integral strategy, is robust for parameter deviation, namely, the precision of the observed torque is basically unaffected by the direct- and quadrature- axis inductance and the rotor flux linkage. Simulations and experiments on an 11 kW PMSM have validated the performance of the proposed method. © 2014 State Grid Electric Power Research Institute Press.


Wang L.,Hefei Sungrow Power Supply | Liu C.,Hefei University of Technology
Chinese Control Conference, CCC | Year: 2016

A virtual inductance control strategy was proposed to restrain stator and rotor current, and torque oscillation caused by grid voltage dips. Firstly, this paper analyzes the dynamic behavior of DFIG during symmetrical voltage dips. Then, the mechanism of virtual inductance control strategy to restrain stator and rotor current oscillation was analyzed. The correctness and effectiveness of this paper was verified by simulation and experimental results. © 2016 TCCT.


Shao Z.,Hefei University of Technology | Zhang X.,Hefei University of Technology | Wang F.,Hefei University of Technology | Cao R.,Hefei Sungrow Power Supply
IEEE Transactions on Power Electronics | Year: 2014

Unique pitfalls in parallel three-level T-type inverters (3LT2 Is) are potential zero-sequence circulating currents (ZSCCs) which are more complex than parallel two-level inverters and can cause current discrepancy, current waveform distortion, power losses, etc. In this paper, the ZSCC paths in the parallel 3LT2 Is are first presented, and an equivalent model of the ZSCCs is developed. It is seen from this model that the ZSCCs consist of conduction, switching, and hybrid components. Based on the aforementioned analysis, an original sharing neutral bus structure is proposed to eliminate the conduction ZSCCs. With regard to the switching ZSCCs composed of high-frequency and low-frequency harmonics, modified LCL filters are proposed to eliminate the former, and zero-sequence control loops are put forward to suppress the latter. Furthermore, the proposed schemes are also proven to be effective to elimination of the hybrid ZSCCs. Experimental results validate the developed models and the proposed ZSCC elimination schemes. © 2014 IEEE.

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