【作者】 伍文城；

【导师】 王晓茹；

【作者基本信息】 西南交通大学 ， 电气工程， 2022， 博士

【摘要】 中国电力系统在过去十多年中,大容量长距离特高压直流输电技术得到大力发展和广泛应用。直流功率灵活可控,为实施广域控制、解决电网稳定问题提供了有利条件。本论文针对多直流协调阻尼控制中的基础性问题开展研究,包括多直流协调控制器随机时滞和参数不确定性等问题,提出了新的交直流混合系统的潮流计算算法、状态空间模型辨识方法、多直流协调阻尼控制方法,利用多直流协调控制提高了电力系统的功角小扰动稳定性。（1）为给交直流混合系统状态空间建模提供准确的初值,以交替迭代法为基础,提出了一种计及换流变分接头调整、换流站无功控制管理、换流器控制方式及其转换的交直流混合系统潮流计算方法,并给出了一种将各个两端直流输电系统单独处理、利用多核CPU的并行计算能力来提高计算速度的方法,提高了交直流混合系统潮流求解的准确性和计算效率;一个5节点、2回直流的小规模混合系统例子验证了所提算法的正确性,一个9241节点、60回直流的大规模例子验证了所提算法的良好收敛性与计算效率。为实现准确的辨识建模,将确定性和随机混合系统辨识方法DSR应用到交直流混合系统状态空间模型辨识,利用奇异熵和Tanh-Sigmoid饱和函数自动判定系统阶次,实现了DSR辨识方法所需阶次、过去时域、未来时域等输入参数的全自动化确定,并将其应用于高维、多输入多输出、极点密集分布、在噪声干扰的交直流混合系统状态空间模型辨识。通过三个算例对改进的DSR算法与流行的PEM、N4SID、SSREGEST、PBSID辨识算法进行了全面比较,验证了所提算法辨识精度、抗噪能力、闭环辨识适用性、大系统辨识效率均明显优于参与比较方法。（2）提出一种将多直流协调动态输出反馈控制器求解问题转化为静态输出反馈问题、应用正交差分进化算法来进行多目标优化的控制器求解方法。对H₂、H_∞、阻尼比进行多目标优化遇到的双线性矩阵不等式求解难题,使用正交设计方法生成反馈控制器,将双线性矩阵不等式问题转化为线性矩阵不等式（LMI）问题,使得H₂、H_∞、阻尼比等约束可以直接表达而不用求解满足多个LMI约束的多个Lyapunov矩阵;然后利用正交差分进化算法搜索中目标函数最优值。为提高搜索效率,搜索过程中引入局部增强的正交交叉算子。基于上述思路,实现了区域极点配置、H₂/H_∞最小化等多目标SOF控制问题。通过Compleib测试集以及Can Grid系统的多直流协调控制等测试算例验证了所提出算法的效率及性能。（3）为抑制时延对高压直流附加控制的不利影响,提出了一种基于Jensen积分不等式的时滞相关广域阻尼控制策略。首先,推导了交直流混合系统的计及时滞的状态空间模型;其次,基于Jensen积分不等式,给出了闭环系统的时滞稳定判据;针对判据存在非线性矩阵不等式求解的困难,给出了随机生成初始解的求解方法;最后,利用差分进化算法优化控制器的时滞稳定上限。与流行的自由权矩阵等时滞稳定控制器设计方法相比,所提方法基于输出反馈,所需决策变量更少,能用于较大规模的系统,因此在大规模交直流混合系统中更具实用性。三个算例验证了所提方法的有效性。（4）针对系统多运行方式、参数发生变化易导致多直流协调控制器性能劣化问题,应用凸多面体线性不确定系统描述方式,推导出了H₂、H_∞、衰减率以及阻尼比的混合优化的松弛变量线性矩阵不等式,通过随机生成输出反馈矩阵,将双线性矩阵不等式转化为线性矩阵不等式,并应用差分进化方法提供搜索方向,实现了H₂、H_∞、衰减率、阻尼比等多个目标的混合优化。所提方法与基于二次稳定性的方法相比,提高了求解成功率,并降低控制器的保守性。基于多直流协调控制的仿真验证了算法的正确性。（5）针对高水电比重系统的超低频振荡问题,推导出了指定阶次的集中式或分散式结构的多直流协调控制器及对应的闭环系统状态空间方程,提出了应用正交差分进化算法实现多直流协调控制器性能优化的方法,可在统一框架下求解给定阶次、给定结构（集中式、分散式以及基于超前-滞后环节的分散式）的多直流协调控制器。将该方法应用于Cigre Nordic以及中国南方电网算例,所设计的三种结构控制器都较大提高了系统阻尼。更多还原

【Abstract】 In the past decades of China’s power system,large capacity and long-distance UHV DC transmission technology has been vigorously developed and widely used.The HVDC power is flexible and controllable,which provides favorable conditions for implementing wide-area control and solving the problem of power grid stability.In this thesis,the basic problems of multi-DC coordinated damping control are studied,including the random time delay and parameter uncertainty of multi-DC coordinated controller.A new power flow calculation algorithm,state-space model identification method,and multi DC coordinated damping control method for AC/DC hybrid system are proposed.Multi-DC coordinated control is used to improve the small disturbance stability of power angle in power system.（1）In order to provide accurate initial values for the state space modeling of AC/DC hybrid system,using the alternating iteration method,a power flow calculation method for AC/DC hybrid system is proposed,which takes into account the adjustment of converter taps,reactive power control management of converter station,converter control mode and its conversion.The parallel computing ability of multi-core CPU is used to improve the calculation speed,which improves the accuracy and efficiency of power flow calculation of AC/DC hybrid system;A 5-bus,2-circuit DC hybrid system example verifies the correctness of the proposed algorithm,and a 9241 bus,60 circuit DC hybrid system example verifies the good convergence and computational efficiency of the proposed algorithm.In order to achieve accurate identification modeling,the deterministic and stochastic hybrid system identification method DSR is applied to the state space model identification of AC/DC hybrid system.A system order determination method based on singular entropy and tanh-sigmoid saturation function is proposed.A fully automatic determination method of DSR input parameters such as order,past horizon and future horizon is proposed,which realizes the state space model identification of AC/DC hybrid system with high-dimensional,multi-input and multi-output,dense pole distribution and noise disturbance.Through three examples,the improved DSR algorithm is compared with the popular PEM,N4SID,SSREGEST and PBSID identification algorithms.The results show that the identification accuracy,anti-noise ability,closed-loop identification applicability and large-scale system identification efficiency of the proposed algorithm are significantly better than those of the compared methods.（2）A controller synthesis method is proposed to transforms the controller synthesis problem of multi-DC coordinated dynamic output feedback system into the static output feedback problem,and the orthogonal differential evolution algorithm is applied to realize multi-objective optimization.To solve the bilinear matrix inequality（BMI）problem with multi-objective optimization of H₂,H_∞and damping ratio,an orthogonal design method is used to generate a feedback controller,and the BMI problem is converted into the linear matrix inequality（LMI）form.The constraints such as H₂,H_∞and damping ratio can be expressed directly without solving multiple Lyapunov matrices constrained by multiple LMI conditions.Then the orthogonal differential evolution algorithm is used to search the optimal value of the objective function.In order to improve the search efficiency,a locally enhanced orthogonal crossover operator is introduced.Based on the above ideas,multi-objective SOF synthesis problems such as regional pole assignment,H₂ and H_∞minimization are realized.The efficiency and performance of the proposed algorithm are verified by the COMPLEIB test set and multi DC coordinated control example of Can Grid system.（3）In order to suppress the adverse effect of time delay on HVDC supplemental control,a delay dependent wide area damping control strategy based on Jensen integral inequality is proposed.Firstly,the state space model of AC/DC hybrid system considering time delay is derived;Secondly,based on Jensen integral inequality,the delay stability criterion of the closed-loop system is given;Aiming at the difficulty of solving the nonlinear matrix inequality in the criterion,a method of randomly generating initial solution is proposed;Finally,the delay stability upper bound of the controller is optimized by differential evolution algorithm.Compared with the popular time-delay stable controller design methods such as free weight matrix,the merits of the proposed method are based on output feedback and requires less decision variables,so it can be used in large-scale systems,and it is more practical in large-scale AC/DC hybrid systems.Three numerical examples verify the effectiveness of the proposed method.（4）In order to solve the problem that the performance of multi DC coordination controller deteriorated easily due to multi-operation modes and parameter changes of the system,a relaxed variable LMI for mixed optimization of H₂,H_∞,decay rate and damping ratio is derived by using convex polytopic uncertainties description,The BMI is transformed into LMI,and the differential evolution algorithm is used to provide the search direction.The hybrid optimization of H₂,H_∞and multiple objectives,such as decay rate and damping ratio,is realized.Compared with the method based on quadratic stability theory,the proposed method improves the solution success rate and reduces the conservatism of the controller.The simulation based on multi DC coordinated control verifies the correctness of the algorithm.（5）Aiming at the problem of ultra-low frequency oscillation system with high proportion of hydropower,the centralized or decentralized multi DC coordinated controller with specified order and the corresponding closed-loop system state space equation are derived.The performance optimization method of multi-DC coordinated controller based on orthogonal differential evolution algorithm is proposed,which can optimized the controllers’performance of given order and given structure（centralized,decentralized,include lead-lag based decentralized）in a unified framework.The proposed method is applied to CIGRE Nordic and China Southern Power Grid.The results show that the system damping is greatly improved with the three kinds of controllers designed by the purposed method.更多还原