基于80C196KC的风力发电系统功率控制器设计

通过对独立运行风力发电系统的能量流动关系的分析与研究,得出了系统运行的工作模式。提出了通过调节电磁转矩-转速特性调节功率的一种控制策略,使风力发电机输出在额定风速以下自动跟踪负载用电量。为了运用此控制策略,采用单片机80C196KC作为控制芯片,设计了用于控制发电机输出功率的电子调节装置。搭建了小型风力发电系统实验平台并进行了实验研究,实验结果验证了本文设计的功率控制器有效地解决了独立运行小型风力发电系统功率平衡问题。     

小型风光互补控制策略研究

文中通过对比风光互补系统各种常用最大功率点跟踪（MPPT）控制策略,提出了改进的MPPT控制策略。光伏电池阵列输出功率通过电压反馈扰动MPPT控制策略进行控制,风力发电机输出的功率采用变步长扰动MPPT控制策略;在蓄电池支路上串联一个MOSFET管,起到截止充电功能,并提出了改进的三段式充电方法。     

直驱风力发电系统机侧控制策略的研究

以直驱风力发电系统为研究对象,选用背靠背双PWM的拓扑结构,针对永磁同步风力发电机机侧的控制策略进行分析。在建立永磁同步风力发电机数学模型的基础上,基于ixt=0的转子磁场定向控制,设计了电流内环转速外环的双闭环控制器,并对控制原理在Matlab／Simulink上进行仿真实验,验证了该控制策略的正确性。     

基于最佳功率给定的永磁直驱同步风力发电系统控制策略研究

直驱型风力发电系统由于不需要增速箱,在风电场中得到广泛的发展和应用.该文研究了发电机和风机的特性分析,提出了基于最佳功率给定的最大风能控制策略,该方法通过对发电机进行闭环控制,使输出功率按照最优功率曲线进行输出,实现最大风能跟踪.并研究了永磁直驱风电系统的双PWM变流器控制策略;搭建了直驱型风电机组整体模型,该系统能够实现并风能最大功率跟踪及并网控制,仿真验证了控制系统的正确性.     

基于VSG的微电网二次调频控制策略

针对多台虚拟同步发电机(VSG)并联运行的微电网系统易受负荷波动影响而产生的频率越限问题,提出一种基于VSG的频率二次控制策略。首先,分析VSG的控制原理,并指出一次调频的不足;其次,通过将频率偏差引入PI控制器中,实现微电网在不需要通讯的条件下的二次频率控制。同时实现了各并联VSG调频功率的均匀分配,并利用小信号模型分析PI参数对系统稳定性的影响。最后,利用MATLAB/Simulink搭建仿真模型,验证了所提二次调频控制的有效性。     

双绕组异步风电机组同步化并网运行仿真研究

针对定子双绕组异步电机(DWIG)在并网运行条件下展开研究,通过对发电机的控制,使其在功率绕组侧输出稳定三相交流。借鉴同步发电机的运行控制策略,将有功-频率、无功-电压下垂控制方法移植到并网逆变器的控制中,使得逆变器有了频率与电压保持特性,从而在外特性上具有同步发电机的特征。提升了包括DWIG在内的整个风电机组并网运行性能,使其具备维持系统功率平衡、维持电网频率和电压稳定性等优点。有效缓解了风电大规模接入电网而对电网造成的不利影响。基于Simulink的仿真结果证明了系统和控制策略的正确性与有效性。     

基于自抗扰技术的DFIG网侧换流器直接功率控制策略探究

针对双馈型风力发电机中网侧变换器,在分析其数学模型的基础上,采用基于自抗扰控制的直接功率控制策略对网侧变换器进行控制。并且利用Matlab/Simulink软件对设计的控制器进行仿真,仿真结果显示,该控制策略能够保证直流母线电压稳定,网侧功率因数为1,当系统发生扰动时,该控制策略较传统PI控制具有更强的鲁棒性,控制效果理想。     

基于频率分割和虚拟直流机的混合储能控制策略研究

针对直流微电网混合储能中能量电池使用寿命的问题,设计频率分割器和功率调节环节,通过对系统净功率进行分割,提升混合储能的平抑效果和能量电池的使用寿命。并考虑到微电网储能变换器低惯量和弱阻尼的特点,采用虚拟直流发电机控制策略,提升系统的暂态稳定性。通过仿真结果表明,相较于传统PI控制,所设计的控制策略可以使母线电压波动小于0.53%;并且能量电池的功率波动和功率电池相比,变化趋势明显平缓。     

基于电网接口虚拟同步发电机的等效功率平抑及频率补偿方法研究

网侧功率变换器是大规模风电系统接入电网的关键接口,随着大规模风电装备渗透率的不断提高,并网逆变装置对大电网中的影响愈发凸显。借鉴传统电力系统中的同步发电机数学模型,提出了一种大规模风电装备虚拟同步发电机（Virtual Synchronous Generator,VSG）等效实现功率平抑及频率补偿方法。首先,设计了具有电力电子装置自身特性的虚拟调速器和虚拟励磁控制器,保证电网电流的低谐波畸变的同时,具有响应电网电压幅度、频率波动事件功能,可在一定程度上提高电网的稳定性。同时模拟同步发电机的转动惯量,提高电网接口的惯性和阻尼特性,降低大规模风力发电系统对传统电网的冲击。最后,基于110kW风力发电机组及锂电池储能单元对所提方法的可行性和有效性进行了验证与分析。     

基于虚拟同步发电机的微网逆变器控制策略

本文中微网是由多种分布式电源与负载组成的小型发配电系统,是实现主动式配电的有效途径。然而传统的微网逆变器接口控制方式存在切换复杂的缺点,不利于维持微网稳定。为此,基于虚拟同步发电机设计一种新的微网逆变器控制策略。根据VSG控制原理,将VSG等效为一个电压源,并引入频率反馈环节,使逆变器电源能够追踪电网频率;同时,采用并压电流双闭环保证并网电压的稳定,无偏差地实现频率和电压稳定,从而实现微网逆变器稳定控制。该控制策略建立了有效的微网控制结构与能量管理体系,可提高微网控制过程的灵活性和可靠性。仿真结果也验证了该控制策略的正确性和可行性。     

A Secondary Voltage Control Strategy for Transmission Level Interconnection of Wind Generation

This paper addresses implementation issues associated with secondary voltage control in a doubly-fed induction generator based wind farm. The effects of different system parameters on the performance of the control are considered, namely the short circuit ratio of the interconnection and the inherent communication delay between the wind park and the remote bus. In addition, a strategy for allocation reactive power requirements to each of the generators within the wind park is proposed. The system is developed and simulated for a wind park consisting of six wind generators connected to a typical transmission system. The paper proposes an optimal tracking secondary voltage control method developed to achieve effective voltage regulation, enhance the network voltage profile and provide optimal reactive power compensation to the interconnected power system. The performance of the controller is compared with secondary voltage control at one selected bus, primary voltage control and the optimal voltage profile obtained from the optimal power flow analysis. The performance of the controllers is tested for steady state operation and in response to system contingencies, taking into account the impact of communication time delays and short circuit ratio (SCRs). Simulation results are presented to demonstrate the capability of the controllers to provide the desired reactive power compensation and voltage support to the electric power grid.     

A Tubular-Generator Drive For Wave Energy Conversion

This paper illustrates the operation of a tubular-machine drive as a linear generator for a heave-buoy wave energy conversion. Linear generators, which are adopted in marine power plants, offer the advantage of generating without introducing any conversion crank gear or hydraulic system. The use of a tubular-machine topology allows the electromagnetic thrust density to be improved. This paper briefly summarizes the principles of marine wave buoy interaction and reports the design analysis and control of a permanent-magnet (PM) synchronous tubular linear machine based on a scaled generator prototype and on a rotating simulation test bench.     

直驱永磁同步风力发电系统MPPT跟踪控制

根据永磁同步风力发电机的运行特性,构建以输出功率为反馈量、转速为控制对象的最大风能捕获控制模型,并在永磁同步发电机d,q轴数学模型和矢量控制理论基础上,通过转子磁场定向控制策略,实现有功、无功功率解耦控制,减小了损耗,并且较好地控制了转速。利用Matlab/Simulink进行仿真,对风速阶跃变化时机组运行情况进行了仿真,并给出了仿真结果。实验结果验证了该控制系统的正确性与可行性。     

兆瓦级三电平永磁直驱风力发电系统仿真研究

基于永磁同步发电机(PMSG)数学模型,采用双三电平PWM结构的全功率变换器;机侧采用转子磁链定向的矢量控制技术并结合PMSG较为常用的零d轴电流控制方案,提高了系统效率;基于电网电压定向,网侧变换器应用电压电流双闭环控制策略;在Matlab/Simulink仿真环境下建立了直驱式永磁同步风力发电系统的仿真模型,包括:SVPWM矢量控制模块,零d轴电流控制模块,abc到dq坐标变换模块,电压补偿模块。对风速阶跃变化时系统运行情况进行了仿真,结果验证了该模型的合理性及控制策略的正确性和可行性。     

Extending the Life of Gear Box in Wind Generators by Smoothing Transient Torque With STATCOM

Gearboxes for wind turbines must ensure high reliability over a period of 20 years, withstanding cumulative and transient loads. One main challenge to this is represented by electromagnetic torque transients caused by grid faults and disturbances, which will result in significant stresses and fatigue of the gearbox. Possibilities for limiting the torque transients in fixed-speed wind generators have not been previously reported. This paper presents a technique by which the transient torques during recovery after a grid fault can be smoothed in a wind farm with induction generators directly connected to the grid. A model-based control technique using the quasi-stationary equivalent circuit of the system is suggested for controlling the torque with a static synchronous compensator (STATCOM). The basis of the approach consists of controlling the induction generator terminal voltage by the injection/absorption of reactive current using the STATCOM. By controlling the terminal voltage as a function of the generator speed during the recovery process, the electromagnetic torque of the generator is indirectly controlled, in order to reduce the drive train mechanical stresses caused by the characteristics of the induction machine when decelerating through the maximum torque region. The control concept is shown by time-domain simulations, where the smoothing effect of the proposed technique on a wind turbine is seen during the recovery after a three-phase-to-ground-fault condition. The influence of the shaft stiffness in a multimass drive train model is discussed, and the performance of the control concept in the case of parallel connection of several turbines is investigated to discuss the applicability in a wind farm.      

Flexible control of small wind turbines with grid failure detection operating in stand-alone and grid-connected mode

This paper presents the development and test of a flexible control strategy for an 11-kW wind turbine with a back-to-back power converter capable of working in both stand-alone and grid-connection mode. The stand-alone control is featured with a complex output voltage controller capable of handling nonlinear load and excess or deficit of generated power. Grid-connection mode with current control is also enabled for the case of isolated local grid involving other dispersed power generators such as other wind turbines or diesel generators. A novel automatic mode switch method based on a phase-locked loop controller is developed in order to detect the grid failure or recovery and switch the operation mode accordingly. A flexible digital signal processor (DSP) system that allows user-friendly code development and online tuning is used to implement and test the different control strategies. The back-to-back power conversion configuration is chosen where the generator converter uses a built-in standard flux vector control to control the speed of the turbine shaft while the grid-side converter uses a standard pulse-width modulation active rectifier control strategy implemented in a DSP controller. The design of the longitudinal conversion loss filter and of the involved PI-controllers are described in detail. Test results show the proposed methods works properly.     

Thyristor-based current-fed drive with direct power control for permanent magnet-assisted synchronous reluctance generator

This paper proposes a robust and simple direct power control (DPC) of a thyristor-based current-fed drive for generator applications. A current-fed drive and permanent magnet-assisted synchronous reluctance generator (PMa-SynRG) are investigated to deliver 3 kW power using a combustion engine. The current-fed drive utilises a thyristor-based three-phase rectifier to convert generator power to DC-link power and a single-phase current-fed inverter to supply a single-phase inductive load. In addition, a new control algorithm is developed based on DPC for the current-fed drive. The DC-link voltage-based DPC is proposed in order to directly control the output power. The goal of the DPC is to maintain the DC-link voltage at the required output power operating point. The DPC has advantages such as a simple algorithm for constant speed operation. Another feature of the developed current-fed drive is its inherent capability to provide generating action by making the PMa-SynRG operates as a generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power into the load. These features make the current-fed drive a good candidate for driving any type of synchronous generators including the proposed PMa-SynRG.     

Control of Three-Level PWM Converter Applied to Variable-Speed-Type Turbines

This paper proposes advanced control of a three-phase three-level neutral-point-clamped pulsewidth-modulated (PWM) converter connecting a permanent-magnet synchronous generator to a grid. The control scheme is mainly based on active and reactive power loops and contains the following additional blocks: virtual flux and filter-capacitor voltage estimators for sensorless operation, active damping (AD) of possible resonances in the LCL filter that connects the converter to the grid, and a PWM modulator with dc-link voltage balancing and minimization of switching losses. It is shown that the proposed control method exhibits several features such as sensorless operation, robust algorithm, minimization of switching losses, and simple tuning procedure of AD. The simulation and experimental results have proven an excellent performance and verified the validity of the proposed system.     

Direct Power Control Applied to Doubly Fed Induction Generator Under Unbalanced Grid Voltage Conditions

This paper analyzes the effects of unbalanced voltage on doubly fed induction generators. It also presents a novel control strategy based on direct power control (DPC+) applied to this type of generators, predominant in wind energy applications, that enables them to work under perturbed conditions and achieve optimum results. Although the technique can be implemented to control both rotor converters and grid converters, we will hereby exemplify the former which regulates stator active and reactive power. The results obtained with DPC+ are then compared through experimental tests to indicate that the technique is suitable and achieves good dynamic responses while controlling current distortion, power or torque oscillations. The validation of results has been performed through experimental tests on a 20-kW generator.