面向风电场并网的双端与多端柔性直流输电系统控制策略研究

发布时间：2018-02-24 21:18

本文关键词： 风力发电多端柔性直流输电交直流混合输电频率辅助控制模拟电源控制双模式控制　出处：《华南理工大学》2014年博士论文　论文类型：学位论文

【摘要】：石油、天然气、煤炭等常规能源资源紧缺且污染环境。作为技术相对成熟的可再生能源，风能的开发利用已成为许多国家实现新能源发展目标的主要政策。在新能源政策的推动下，风电已经快速发展且在电网中的容量不断地增长。与此同时，风电场由小规模向大型化发展，单一风电场装机容量由几十兆瓦增长到几百，甚至上千兆瓦。大型风电场大多远离负荷中心，需要通过远距离输电集中接入电网。而风电出力具有很强的波动性与间歇性，大型风电场经交流线路接入电网的稳定性和可靠性受到电网扰动和电压支撑能力的影响，风电的远距离输送能力已经成为制约风力发电发展的瓶颈之一。基于电压源换流器(voltage source converter, VSC)的柔性直流输电可以实现有功功率和无功功率的独立控制，具有很强的输电灵活性，是实现大型风电场与电网稳定连接的最有潜力的电力传输方式。但是常规柔性直流输电系统采用定功率(或定电流)控制方式，难以适应风电场功率波动和频率随动的特性。为实现高效率和高可靠性的大型风电场的电网接入，需要对双端和多端柔性直流输电的控制策略开展创新性的研究。论文首先建立了两种典型风电机组，包括鼠笼式感应发电机(SCIG)和双馈感应发电机(DFIG)的详细电磁暂态模型，并在PSCAD/EMTDC下仿真验证了模型的有效性，得到了机组的运行特性。根据风电场柔性直流输电并网研究的需要，给出了风电场的单机等值建模方法。论文第三章建立了柔性直流输电系统在abc坐标系下的详细数学模型，然后导出了其在dq0旋转坐标系下的数学模型。并在此基础上，对基于二极管箝位型多电平电压源换流器和模块化多电平(MMC)型电压源换流器的柔性直流输电系统进行建模和仿真研究。针对柔性直流输电系统的非线性特性，论文提出了两种柔性直流输电的非线性解耦控制方法：一种是基于EL (Euler-Lagrange)模型的柔性直流输电的非线性解耦控制。基于换流器的能量耗散性，采用状态误差构造能量存储函数并以误差存储函数为Lyapunov函数，通过注入阻尼使系统快速收敛到期望稳定平衡点。根据误差存储函数的收敛条件设计了换流器的无源控制器，实现了各变量的解耦控制；另一种是基于PCHD模型的柔性直流输电鲁棒控制。基于端口受控耗散哈密尔顿(PCHD)方程建立了换流器的PCHD模型，，证明了换流器的严格无源性。通过配置连接矩阵与阻尼矩阵构造期望能量函数并确立为Lyapunov函数。通过注入阻尼矩阵消除了换流器直流侧等效电阻对系统的影响。由期望平衡点、状态变量及互联和阻尼分配无源性(IDA-PB)控制原理设计了换流器的IDA-PB控制器。两种控制策略均在不同的运行条件下用PSCAD/EMTDC软件进行了仿真验证，结果表明所提出的控制策略具有良好的动、静态性能和鲁棒性。对于换流器级控制，基于电压矢量定向直接电流控制方法提出了一种定有功功率与频率辅助控制策略，适合于风电经交直流并联接入电网场合。针对风电经纯柔性直流并网场合，设计了一种新的柔性直流控制方法。该方法将风电场电压源换流器系统侧交流母线控制为定交流电压幅值、频率和相角的拟无穷大电源点，实现了有功功率的随动控制。两种策略均适用于多端柔性直流并网控制。针对多个孤岛风电场经多端柔性直流输电并网方式应用了一种星形拓扑结构，拓扑结构中将其中一端风电场电压源换流器直流母线作为汇流点，共用一条直流通道输电。不同运行条件下的仿真结果验证了上述控制方案的有效性与正确性以及拓扑结构的可行性。为提高风电场交直流混合输电并网的系统性能，论文第六章提出了一种更加灵活的新型VSC-HVDC双模式控制策略。针对风电场侧电压源换流器设计的新型交流电压－功角控制策略能适应风电交直流并联并网和纯直流并网两种输电模式，在交流故障引起的模式变化中无需切换控制策略。在交直流混合输电模式下，该控制策略通过调节风电场交流母线电压与电压源换流器输出电压间的功角调节有功功率。在纯柔性直流输电模式，可自动转换为整流站交流母线拟无穷大电源模式，实现了对波动风电的同步输送。另外，通过附加电流高通滤波器增强了对系统谐振的阻尼作用。对电网侧电压源换流器采用了一种新的直接电流矢量控制，使直流电压稳定在参考值上。运用PSCAD/EMTDC仿真软件对分别接入笼型感应发电机风电场和双馈感应发电机风电场的交直流混合输电系统建模仿真。在一系列运行条件下的仿真验证了所提控制策略的有效性与可行性。最后，以南澳岛风电场多端交直流混合输电工程为应用对象，对论文提出的双模式控制策略进行了仿真，验证了策略的有效性。论文成果对用于风电并网的双端和多端柔性直流输电控制策略设计和优化具有良好的指导意义和参考价值。
[Abstract]:As a relatively mature renewable energy source , the utilization and utilization of wind energy has become the main policy for many countries to achieve the goal of new energy development . Flexible DC power transmission based on voltage source converter ( VSC ) can realize the independent control of active power and reactive power , and has strong transmission flexibility . It is the most potential power transmission way to realize stable connection between large wind farm and power grid . However , the conventional flexible direct current transmission system adopts constant power ( or constant current ) control mode , it is difficult to adapt to the characteristics of power fluctuation and frequency follow - up of wind farm . In this paper , two typical wind turbine units , including squirrel - cage induction generator ( SCIG ) and double - fed induction generator ( DFIG ) , are established , and the effectiveness of the model is verified by simulation under PSCAD / EMTDC . In chapter 3 , a detailed mathematical model of the flexible DC power transmission system in the abc coordinate system is established , then the mathematical model of the flexible DC power transmission system in the rotating coordinate system of dq0 is derived . On this basis , the flexible DC power transmission system based on the diode clamped multilevel voltage source converter and the modular multilevel ( MMC ) type voltage source converter is modeled and simulated . In this paper , the nonlinear decoupling control method for flexible DC power transmission system is presented in this paper . Based on the energy dissipation of the inverter , the energy storage function is constructed based on the state error and the error storage function is used as the Lyapunov function . The inverter ' s IDA - PB controller is designed based on the convergence condition of the error storage function . The simulation results are simulated by using the PSCAD / EMTDC software under different operating conditions . The results show that the proposed control strategy has good dynamic , static performance and robustness . A new flexible direct current control method is proposed based on direct current control based on direct current control based on voltage vector control . A new flexible direct current control method is proposed in this paper . In this way , a new flexible DC control method is designed for the direct current grid with AC voltage amplitude , frequency and phase angle . The method applies one end wind farm voltage source converter DC bus as bus point and common one DC channel . The simulation results under different operating conditions verify the validity and correctness of the control scheme and the feasibility of topology . In order to improve the system performance of AC / DC hybrid transmission grid , a novel VSC - HVDC dual - mode control strategy is proposed in chapter 6 . A new type of AC voltage - work angle control strategy for wind farm side voltage source converter is proposed , which can adjust the active power by adjusting the power angle between the AC bus voltage of the wind farm and the output voltage of the voltage source converter . Finally , based on the multi - terminal AC / DC hybrid transmission project of Nan ' ao Island , the double - mode control strategy is simulated and the effectiveness of the strategy is verified . The results of this paper have good guiding significance and reference value to the design and optimization of double - end and multi - terminal flexible direct current transmission control strategy for wind power grid .

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM721.1;TM614

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