Abstract —— Due to network events and power system emergencies, doubly-fed induction generator (DFIG) based wind turbines can suffer from low voltage ride through which may result to the disconnection of the DFIG. Before connecting to the electricity grid again, DFIG has to be synchronized to minimize the transient effects and ensure smooth connection to the power grid. In this paper, a direct voltage control based synchronization technique is proposed for DFIG based wind turbines. Additional control features are added to original direct voltage control method for implementation of the proposed synchronization strategy. A grid connection logic is designed and presented for soft connection of DFIG to the grid. The proposed technique is implemented in a DFIG based wind turbine model and tested through simulations with various practical scenarios. Voltage transients, frequency analysis, voltage phase and system stability are analyzed in details and simulation results presented. From the results, it can be revealed that the proposed synchronization technique functions effectively and efficiently. It is also shown that by using the proposed technique, the process of synchronization and grid connection do not introduce any changes into the system, which may cause protection devices to trip or mal-operation.
2021-08-26 14:08:26
1.03MB
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Abstract —— Grid connected wind turbines may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a doubly fed induction generator developed in the simulation tool of PSCAD/EMTDC. Flicker emission of variable speed wind turbines with doubly fed induction generators is investigated during continuous operation, and the dependence of flicker emission on mean wind speed, wind turbulence intensity, short circuit capacity of grid and grid impedance angle are analyzed. A comparison is done with the fixed speed wind turbine, which leads to a conclusion that the factors mentioned above have different influences on flicker emission compared with that in the case of the fixed speed wind turbine. Flicker mitigation is realized by output reactive power control of the variable speed wind turbine with doubly fed induction generator. Simulation results show the wind turbine output reactive power control provides an effective means for flicker mitigation regardless of mean wind speed, turbulence intensity and short circuit capacity ratio.
2021-08-26 14:08:22
598KB
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ABSTRACT —— Unbalanced grid voltage sags are the severe challenge for wind power generation system which connected to the grid successfully. The dc bus voltage and output power will fluctuate under unbalanced grid voltage. Moreover, the voltage sags will lead to the increase of peak current, which will bring potential safety hazards to the operation of wind power system. This paper proposes a simple current limiting control scheme without auxiliary equipment, which based on the detailed analysis of the excessive peak current. In this scheme, the machine side converter (MSC) controller adjusts the electromagnetic power according to the power transmitted to the grid by the grid side converter (GSC). Meanwhile, it converts the unbalanced power on the dc-link into the rotor kinetic energy, avoiding the dc-link overvoltage. The GSC controller can not only ensure that the three-phase inverter currents are in the maximum safe range that the converters can bear, but also provide reactive power support for the grid. Furthermore, the fluctuations on dc bus voltage and output power can be eliminated effectively by using the GSC controller. The feasibility of the proposed scheme and the superiority over the traditional control schemes have been verified by simulations under different types of unbalanced voltage.
2021-08-26 14:08:20
2.76MB
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为改进变速恒频发电系统的性能,采用励磁控制优化的相关理论与仿真研究的方法,对双馈风力发电机的系统进行建模,通过最大功率点追踪(MPPT)算法的相关理论以及最优算法,提出一种不依赖于风速测量实现双馈风力发电系统最大功率点追踪(MPPT)控制的策略,运用Matlab软件建立变速恒频双馈风力发电仿真模型进行数值模拟分析.研究结果表明:仿真模拟验证了该研究方法的正确性.对于推广绿色能源技术、节能减排具有重要理论及实际意义.
2021-08-25 16:58:31
397KB
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本文在研究双馈感应发电机变速恒频风力发电系统的基础上,致力于研究其励磁电源。以双 PWM 变换器作为主要研究对象，对其进行了分析、建模与控制，主要包括以下几方面：
1、对国内外风力发电现状从装机容量、发展状况以及技术特点等几个方面作了较为全面的综述。对几种典型的变速恒频风力发电系统作了详细的对比分析，解释了将双馈感应发电机应用于变速恒频风力发电的可行性和优越性。通过对目前可用于变速恒频风电系统的励磁电源进行比较得出，采用双 PWM 变换器作为变速恒频风电系统的励磁电源是一种现实的选择。
2、介绍了网侧 PWM 变换器的基本结构及运行原理，建立了其数学模型，探讨了控制策略。为了实现网侧变换器的控制目标，分析了其基本结构，建立了其在两相同步旋转坐标系下的数学模型，得出电网电压定向控制策略，构建了双闭环串级 PI控制方案。 给出了主电路参数及 PI 参数的计算方法， 并对空间矢量脉宽调制（SVPWM）算法进行了分析。仿真结果证明了该控制策略的有效性。
3、 在分析双馈感应发电机数学模型的基础上， 探讨了转子侧变换器的控制策略。本文在分析定子磁链定向矢量控制的基础上，构建了有功和无功功率解耦控制的双闭环 PI 控制方案。 仿真结果证明该控制策略能实现最大风能追踪和定子有功和无功功率的独立控制。
4、建立了双 PWM 变换器控制系统的仿真模型，进行系统仿真。仿真结果表明，网侧在整流和逆变状态都能实现单位功率因数运行；双馈电机转速能快速跟踪风速变化；电机在亚同步、同步、超同步三种状态运行时，转子电流频率满足变速恒频运行条件；同时实现了定子无功功率的独立调节。
5、结合实验室具体条件，搭建了网侧 PWM 变换器实验电路，编制了基于TMS320F2812 的网侧 PWM 变换器的控制程序，并对实验结果进行了分析。
2021-08-25 13:04:58
780KB
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行业资料-电子功用-太阳能光热发电与风力发电互补提高产气率的沼气池.zip
2021-08-25 09:06:09
315KB