基于变流器的风电机组（wind turbine generator, WTG）的次同步振荡问题（subsynchronous oscillation, SSO）是近年来电力系统中新出现的严重稳定性问题之一。SSO是由风电变流器控制环节与串联补偿线路或弱交流电网间的次同步控制交互作用（subsynchronous control interaction, SSCI）引起的。在过去十年中，世界各地发生了多起SSCI事件，其中ERCOT风电场、Xcel Energy风电场、Hornsea风电场，以及中国河北沽源和新疆哈密的风电基地等。在各类SSO事件中，次同步振荡的频率由多种因素决定，包括风速、在线机组数量、风电机组控制结构和控制参数、串联补偿水平和电网强度等。若不及时处理，SSO将会引发设备损坏、发电量减少、电能质量降低等不良后果。为保证大型风电系统的安全稳定运行，亟需研发高效可靠且具有良好适应能力的SSO抑制策略。论文提出了三种抑制SSO的控制策略，即：1）一种针对III型风电机组—串补输电系统的网侧频率自适应阻尼控制；2）一种针对接入弱电网的IV型风电机组的网侧频率自适应次/超同步阻尼控制；3）一种针对III型风电机组的转子侧次同步阻尼控制。最后，本文还首次将所提出的机侧和网侧次同步阻尼抑制器安装在了中国北部的沽源风电场，并提供了实际控制器在现场的抑制效果的验证情况。最后，本文首次提供了将所提出的电网侧和发电机侧的振荡抑制器安装在实际风电场中进行振荡抑制的现场实测效果，其中察北变电站的风力发电机上安装了网侧次同步阻尼控制器，而莲花滩风电场的其中四台III型风电机组中安装了转子侧次同步阻尼控制器。这些现场成功的振荡抑制案例证明了所提振荡抑制策略的有效性，并且增强了所提设计方案的可信度。

Subsynchronous oscillation (SSO) associated with converter-based wind turbine generators (WTGs) is an emerging and serious stability issue. The SSO is caused by the subsynchronous control interaction (SSCI) between wind turbine converter controls and the ‘series compensated’ or ‘weak AC grid’. Several such SSCI incidents have been reported around the world, including those in the ERCOT, Xcel Energy, Hornsea, Guyuan, and Hami wind power systems. The SSO frequency is determined by several factors, including the wind speed, the number of in-service WTGs, wind turbine converter control structure and parameters, series compensation level, and grid-strength. If not dealt with accordingly, the SSO can damage the system equipment, lead to significant loss of power generation and degrade the power quality. To ensure the reliable and stable operation of large-scale wind farms, there is an urgent need to developing a practical countermeasure that is effective under a wide range of operating conditions and oscillation frequencies.This dissertation proposes 1) a grid-side frequency adaptive mitigation strategy for damping SSO in Type-3 WTGs connected to series compensated transmission network, 2) a grid-side frequency adaptive mitigation strategy for damping subsynchronous as well as the super-synchronous oscillation in Type-4 WTGs connected to weak AC grid, and 3) a generator-side damping control scheme for damping SSO in Type-3 WTGs connected to series compensated transmission line. Finally, for the first time, this research presents field application cases of the grid-side and generator-side subsynchronous damping controllers commissioned in the actual Guyuan wind power system in Northern China.The proposed adaptive control strategy for the Type-3 WTGs consists of a subsynchronous frequency estimator (SSFE) and an adaptive subsynchronous damping controller (ASDC). The SSFE uses line current to detect the oscillation mode and estimates its frequency online. The ASDC utilizes the detected subsynchronous frequency to extract the SSO components from the bus voltages. The estimated subsynchronous frequency is further used to tune the center frequencies of the extraction filters and compute the time constants of the phase-shifters such that the phase-shifters always maintain the desired phase-shift at the estimated subsynchronous frequency. Finally, the shunt voltage sourced converter (SVSC) injects the subsynchronous currents into the grid. The ASDC behaves like a variable impedance, which essentially reshapes the overall system’s impedance response by adding a positive resistance at the subsynchronous frequency. The proposed damping control strategy is autonomous and does not require prior system studies as it can detect the SSO, estimate its frequency, and tune phase-shifters online. The ASDC’s frequency adaptiveness and damping performance under different operating scenarios are verified through extensive electromagnetic transient simulations on a realistic Type-3 WTG-based wind power system facing SSO.The SSCI in Type-4 WTGs connected to weak AC grid triggers both sub- and super-synchronous oscillation (S2SO) with strong frequency coupling. Generally, it is not known whether the subsynchronous or the supersynchronous component is dominant and has the leading role, and which component is due to the frequency coupling effect. A reliable damping control strategy should be able to handle the sub- and super-synchronous components individually. This dissertation addresses this problem by proposing a sub- and super-synchronous frequency estimator (S2SFE) to estimate S2SO frequencies simultaneously, and a dual-channel adaptive sub- and super-synchronous damping controller (AS2DC) to damp the S2SO independently. The tuning of the dual-channel AS2DC’s extraction filters and phase-shifters is fully online. The SVSC injects superimposed sub- and super-synchronous currents into the grid to reshape the system impedance at the concerned frequencies. The damping ability is verified through electromagnetic transient simulations of Type-4 WTGs connected to a weak AC grid.On the generator-side, a practical rotor-side subsynchronous damping controller (RSDC) is proposed, which consists of a washout filter and a proportional derivative controller. The RSDC is added in the rotor side converter’s dq-axes inner control loops. When the SSO occurs, the RSDC adds a positive resistance at the subsynchronous frequency, thereby reshaping the impedance response of the WTG at that frequency. The damping performance of the RSDC is validated through controller-hardware-in-the-loop (CHIL) simulations as well as impedance analysis.Finally, for this time, the grid-side and generator-side damping controllers are implemented in an actual wind power system. The grid-side subsynchronous damping controller is installed at the Chabei substation, and four actual Type-3 WTGs are modified to implement the RSDC. The practical application cases not only validated the damping performance but also enhanced the practical confidence of these mitigation schemes.