PMSG机组的低电压穿越技术研究

发布时间：2018-05-08 23:11

本文选题：永磁同步发电机 + 低电压穿越　；参考：《东北电力大学》2017年硕士论文

【摘要】：近年来,风力发电以技术成熟、成本低和大规模开发利用的优势成为新能源发展最快、最具竞争力的技术。风电场接入电网后与电网之间的相互影响已不能忽略。如果风电机组不具备低电压穿越能力(Low voltage ride through,LVRT),当电网电压降落后,风力发电机组会大面积脱网,对电网稳定性造成影响。永磁同步发电机组(permanent magnet synchronous generator,PMSG)已成为新建风电场主要机型。如何在并网点电压跌落期间避免机侧和网侧有功失配,快速稳定直流链电压,是PMSG实现LVRT的关键问题。本文主要针对提高永磁风力发电机组的低电压运行能力展开相关研究工作。分析永磁同步发电机组的运行机理,搭建各主要部分在dq旋转坐标系的数学模型。研究了全功率变流器常规控制策略,机侧变流器采用基于转子磁场定向的零d轴控制方法,网侧变流器应用基于传统电网电压定向控制策略。为提升网侧变流器的稳压与能量转移能力,缓和电网故障期间的系统能量失衡,实现对直流母线电压的快速控制,采用一种基于模式切换的PMSG机组低电压穿越控制策略,该策略在电网电压正常和故障时进行控制模式切换,选择网侧变流器或机侧变流器来控制直流电容电压。另外,为加快直流母线控制速度,提出了一种改进前馈方法,加快了控制速度,降低了直流母线电压的峰值。当电压深度跌落时,受网侧变流器自身功率限制和动态无功支撑要求,网侧变流器有功输出能力会降低,仅依靠网侧变流器无法抑制直流母线电压骤升。为此,提出基于机侧-网侧有功协同的直流母线电压控制策略,此方法能快速抑制直流链电压波动且能改善PMSG低电压穿越能力。介绍了不对称跌落下的两种常用控制方法,而正负序分离是实现不对称电压跌落下并网逆变器控制的关键,即对正负序分离方法做了归类及综述,并选取了四种方法:直接滤波器法、延迟消去法、全微分法、正交滤波器法。对比了理想电压跌落,含谐波电压跌落和频率偏移电压跌落三种情景下的分离性能。仿真分析了各种方法的优劣。在基于有功协同控制的基础上,采取了负序电压前馈方法,应用二阶广义积分器法(SOGI)作为正负序分离方法,抑制不平衡分量,优化不对称跌落下的控制效果,实现了网侧电流正弦化的控制目标。MATLAB/Simulink仿真结果验证了本文提出方法的有效性和优越性。
[Abstract]:In recent years, wind power has become the fastest developing and most competitive technology of new energy with the advantages of mature technology, low cost and large-scale exploitation and utilization. The interaction between wind farm and power grid can not be ignored. If the wind turbine does not have the low voltage ride through LVRTT, when the voltage drops behind, the wind turbine will get rid of the grid in a large area, which will affect the stability of the power network. Permanent magnet synchronous generator has become the main type of new wind farm. How to avoid the active power mismatch between the machine side and the grid side and to stabilize the DC link voltage quickly is the key problem of PMSG to realize LVRT. This paper focuses on improving the low-voltage operation capacity of permanent magnet wind turbines. The operation mechanism of PMSG is analyzed, and the mathematical models of the main parts in dq rotating coordinate system are built. The conventional control strategy of full power converter is studied. The zero-d axis control method based on rotor flux orientation is adopted for the machine side converter and the traditional voltage oriented control strategy for the grid side converter is applied. In order to improve the steady voltage and energy transfer ability of the grid-side converter, ease the system energy imbalance during the fault period of power grid, and realize the fast control of DC bus voltage, a low-voltage traversing control strategy of PMSG unit based on mode switching is adopted. The strategy switches the control mode when the voltage of the power network is normal and fault, and selects the grid-side converter or the machine-side converter to control the DC capacitor voltage. In addition, in order to accelerate the speed of DC bus control, an improved feedforward method is proposed, which speeds up the control speed and reduces the peak value of DC bus voltage. When the voltage depth falls, the active power output capacity of the grid-side converter will be reduced due to the power limitation and dynamic reactive power support of the grid-side converter, and the DC bus voltage sudden rise can not be restrained by the grid-side converter alone. For this reason, a DC bus voltage control strategy based on the active power cooperation between the machine side and the grid side is proposed. This method can quickly suppress the voltage fluctuation of the DC chain and improve the low voltage traversing ability of PMSG. This paper introduces two common control methods under asymmetric drop, and the positive and negative sequence separation is the key to realize the control of grid-connected inverter under asymmetric voltage drop, that is, the positive and negative sequence separation methods are classified and summarized. Four methods are selected: direct filter method, delay elimination method, total differential method and orthogonal filter method. The separation performance of ideal voltage drop, harmonic voltage drop and frequency offset voltage drop is compared. The advantages and disadvantages of various methods are analyzed by simulation. Based on the active power cooperative control, the negative sequence voltage feedforward method is adopted, and the second order generalized integrator method (SOGI) is used as the positive and negative sequence separation method to suppress the unbalanced component and optimize the control effect under the asymmetric drop. The effectiveness and superiority of the proposed method are verified by the simulation results of realizing the sinusoidal control target of network-side current. MATLAB / Simulink simulation results show that the proposed method is effective and efficient.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614

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