随着电力系统中新能源及电力电子装备占比不断提升，暂态电压跌落、暂态过电压等百毫秒级电压安全问题易引发直流系统换相失败、新能源连锁脱网等事故，对我国电网的安全稳定运行造成重大威胁。为解决上述问题，针对电力电子装备占比由低到高的几种典型场景中的同步机、逆变器电源等动态无功资源，研究多类型动态无功资源的主动电压支撑与协同优化方法，保障系统暂态电压安全。首先，在设备层面，研究同步机与逆变器电源动态电压支撑能力的分类、建模与提升方法，作为后续章节的模型基础。为解决百毫秒级暂态电压安全问题，根据机理的差异，将动态电压支撑能力划分为“自发”及“基于控制”的响应能力，并针对前者提出提升方法，有效抵抗暂态电压跌落、过电压。同时，针对暂态电压安全多机协同优化模型内嵌微分-代数方程组难以直接求解的问题，提出表征动态电压关键特征的代数化建模方法，从而消除微分方程约束。其次，针对多直流馈入受端电网，研究多同步机暂态电压安全协同优化方法。为解决直流换相失败问题，在无功-电压二维空间中定义同步机“自发”无功响应能力评估指标，相比于动态无功备用评估更精确；在此基础上构建考虑直流安全约束的“自发”无功响应优化模型，并提出基于近似二次割的加速求解方法。通过所提方法能够提前预留同步机“自发”无功响应能力，降低直流换相失败风险。然后，针对风火打捆外送系统，研究同步机与逆变器电源暂态电压安全协同优化方法。为解决电网强度不足及暂态过电压制约风电消纳的问题，以短路比为电网强度指标并提出精确建模方法，避免线性模型精度不足问题；在此基础上构建考虑短路比与暂态电压安全约束的同步机开机与风机控制协同优化模型，并采用广义Benders分解算法求解，从而提升问题求解效率。该方法提升了电网强度，并通过协调同步机与风机两种动态电压支撑能力，消除暂态电压越限。最后，针对含高渗透率光伏微电网，研究多逆变器电源暂态电压安全协同优化方法。为解决暂态电压越限导致新能源脱网的问题，提出内外环协调的多阶段故障穿越控制策略，通过内外环快慢动态响应之间的配合来保障暂态全过程的安全性；在此基础上构建多逆变器电源控制参数协同优化模型，并提出基于模型等价转换与松弛技术的迭代求解方法，提升问题求解效率。通过所提方法能够协调不同逆变器电源的两种动态电压支撑能力，提升微电网暂态电压安全性。
With the increasing proportion of new energy and power electronic equipment in the power system, transient voltage sags, transient overvoltages, and other hundreds of millisecond voltage security issues are prone to cause accidents such as commutation failures in HVDC systems and cascading tripping of new energy, which pose a major threat to the secure and stable operation of China‘s power grids. To solve the above issues, the active voltage support and coordinated optimization methods for multiple dynamic var resources are investigated to guarantee the short-term voltage security of the system. These dynamic var resources consist of synchronous machines, and inverter-based generators in several typical scenarios with low to high power electronic equipment share.First, from the perspective of equipment, the classification, modeling, and enhancement methods of dynamic voltage support capability of synchronous machines and inverter-based generators are studied as a basis for the subsequent chapters. To solve the issue of transient voltage sags and overvoltages, the dynamic voltage support capability is categorized into "spontaneous" and "control-based" response capabilities according to the differences in the mechanisms, and the enhancement method is proposed for the former, which is effective in resisting the transient voltage sags and overvoltages. Meanwhile, to address the difficulty of solving the multi-machine coordinated optimization model with differential-algebraic equations, an algebraic modeling method is proposed to characterize the key features of the dynamic voltage. Therefore, the constraints of the differential equations can be eliminated.Secondly, for multi-infeed HVDC receiving-end grids, the short-term voltage security-constrained coordinated optimization method of multi-synchronous machines is investigated. To solve the issue of HVDC commutation failure, the index for the "spontaneous" var response capability of synchronous machines is defined in the two-dimensional volt-var space, which is more accurate than the dynamic reactive power reserve. Based on this, a "spontaneous" var response optimization model is constructed, and it takes into account the HVDC security constraints. An accelerated solution method based on approximate quadratic cuts is proposed. The proposed method can reserve the "spontaneous" var response capability of synchronous machines in advance and reduce the risk of HVDC commutation failure.Then, for the wind-thermal-bundled power transmission systems, the short-term voltage security-constrained coordinated optimization method of the synchronous machine and inverter-based generator is investigated. To eliminate the limitation on wind power consumption due to weak grid strength and transient overvoltage violations, the short circuit ratio is taken as the grid strength index and an accurate modeling method is proposed to avoid the inaccuracy of the linear model. Based on this, a coordinated optimization model of synchronous machines and permanent magnet synchronous generators is constructed by considering the short circuit ratio and the short-term voltage security constraints. Then, the model is solved by the generalized Benders decomposition algorithm, which improves the solution efficiency of the model. The proposed method improves the grid strength and eliminates transient voltage violations by coordinating the two dynamic voltage support capabilities of synchronous machines and wind turbines.Finally, for microgrids containing a high penetration rate of the photovoltaic system, the short-term voltage security-constrained coordinated method of multi-inverter-based generators is investigated. To solve the issues of new energy cascading tripping due to transient voltage violation, a new fault ride-through control strategy considering the coordination of inner and outer loops is proposed, which ensures the voltage security of the whole transient process through the coordination between the fast and slow dynamic responses of the inner and outer loops. A coordinated optimization model for the control parameters of different inverter-based generators is constructed based on the proposed control strategy, and an iterative solution method based on the model equivalence transformation and the relaxation technique is proposed to improve the solution efficiency. The proposed method can coordinate the two dynamic voltage support capabilities of different inverter-based generators, and improve the short-term voltage security of microgrids.
