不同控制策略下直驱风电机组的机网耦合特性及稳定性分析

Analysis of Generator-Grid Coupling Characteristics and Stability for Direct-drive Wind Turbines with Different Control Strategies

直驱风电机组与弱交流电网或柔性直流输电系统间相互作用易导致宽频振荡问题。现有研究普遍认为,直驱风电机组与交/直流电网间的交互特性主要取决于其网侧变流器,故通常忽略直驱风电机组的机侧系统动态。已有文献讨论传统矢量控制下机侧系统对直驱风电机组并网特性的影响,但针对不同控制策略下直驱风电机组的机网耦合特性尚缺少相关研究。文中针对4种典型控制策略下直驱风电机组的机网耦合特性进行比较研究。首先,推导并验证了直驱风电机组在不同控制策略下的详细阻抗模型;然后,基于机网耦合度指标对直驱风电机组的机网耦合特性进行对比分析,得出不同控制策略下机侧系统动态对直驱风电机组交流侧阻抗特性及并网稳定性的影响;最后,通过直驱风电机组并弱交流电网分析案例验证了理论分析的正确性。

The interaction between the direct-drive wind turbines and the weak AC grid or flexible DC transmission system will easily lead to wideband oscillation events.It is generally believed that the interaction characteristics between direct-drive wind turbines and AC/DC power grids mainly depend on the grid-side converters,so the dynamics of the generator-side system of direct-drive wind turbines are usually ignored.There have been some literatures discussing the influence of the generator-side system under traditional vector control on the grid-connected characteristics of direct-drive wind turbines,but there is a lack of relevant research on the generator-grid coupling characteristics for direct-drive wind turbines with different control strategies.In this paper,the generator-grid coupling characteristics of direct-drive wind turbines with four typical control strategies are compared.First,the detailed impedance models of direct-drive wind turbines with different control strategies are derived and verified.Then,based on the generator-grid coupling degree index,the generator-grid coupling characteristics of direct-drive wind turbines are compared and analyzed,and the influence of generator-side system dynamics on AC impedance characteristics and grid-connected stability of direct-drive wind turbines with different control strategies is obtained.Finally,the correctness of the theoretical analysis is verified by the case analysis of direct-drive wind turbines connecting to weak AC power grid.