【作者】 杨涛；

【导师】 廖勇；

【作者基本信息】 重庆大学 ， 电气工程， 2021， 博士

【摘要】 随着以风电等可再生能源为代表的非同步机电源渗透率不断增加,电力系统中同步机电源的主导地位将被打破,电力系统运行特性会发生根本变化。惯量控制技术是针对风电并网带来的等效惯量降低问题所提出的解决方案,通过模拟同步发电机组的惯性响应和功频下垂特性,提升电力系统的频率稳定性;但同时也会造成系统中的非同步机电源与同步机电源之间的机电尺度耦合,再叠加风电出力本身的不确定性,导致电力系统稳定性分析与控制系统设计的难度加大。因此,揭示风电机组惯量控制对电力系统稳定性影响机理具有重要的理论意义及应用价值;同时,面对复杂多变的运行工况,如何利用风电惯量灵活可控的优势,合理配置惯量控制参数以满足不同的控制目标,优化调频控制器性能,提升系统频率响应特性,也是当前风电惯量控制技术研究中亟需解决的问题。本文以目前风电场主流应用的双馈风电机组作为研究对象,选取综合惯量控制技术作为风电参与调频的实现路线,开展了以下研究工作:(1)构建了附加综合惯量控制双馈风电机组子系统与单机无穷大子系统间的动态交互作用模型,绘制Phillips-Heffron模型框图,运用阻尼转矩法分析了风电机组综合惯量控制对电力系统稳定性的影响路径和影响机理。同时,基于风电接入点频率与电力系统频率之间的关系建立线性化小信号模型,进一步分析了风电机组综合惯量控制对系统阻尼比和振荡频率的影响趋势。指出不同的综合惯量控制参数以及风电渗透率都会影响风电机组向系统机电振荡环提供的阻尼转矩以及系统振荡模式,不合理的参数设置甚至会导致负阻尼转矩的出现;并且,附加惯量控制使风电机组动力学特性与系统动力学特性产生耦合,其控制参数对系统振荡模式的作用效果会受到系统惯量和阻尼水平的影响。(2)在电力系统虚拟惯量的基础上提出虚拟阻尼的概念,指出了虚拟阻尼对于改善系统稳定性的意义,推导了风电机组综合惯量控制参数与虚拟惯量、虚拟阻尼之间的数学关系。同时,针对附加综合惯量控制参数之间存在的协调性问题,提出一种结合系统主导振荡模式在线辨识和粒子群优化(Particle Swarm Optimization,PSO)的协调控制策略,充分利用虚拟惯量和虚拟阻尼的作用,进一步提升了高风电渗透率下电力系统的稳定性,实现了电力系统多运行场景下频率稳定性和功角稳定性的多目标综合优化。(3)并网风电机组附加综合惯量控制为电力系统引入了新的惯量特性和阻尼特性,这种新特性受风电机组惯量控制参数的影响,并与系统原有惯量与阻尼特性相耦合,增加了系统稳定性控制的复杂度。针对这个问题,基于功率平衡原理建立了考虑双馈风电机组综合惯量控制影响的同步发电机组等效转子运动模型,将这种控制影响及故障因素统一表达为等效惯量参数摄动及有界的不确定扰动,再运用滑模变结构方法,结合等效惯量和等效阻尼的可变性及可控性,提出一种自适应滑模控制(Adaptive Robust-Sliding Mode Control,AR-SMC)策略以改善稳定性。通过理论推导和仿真分析表明,与传统的惯量控制方法相比,AR-SMC控制策略能够更好地降低频率变化率,抑制频率偏移幅度,提升电力系统稳定性。(4)风电机组采用综合惯量变参数控制方法能够更好地兼顾不同风速下的系统频率响应特性以及转子运行安全性,但控制参数的动态变化也会让系统状态在运行过程中发生改变,从而影响基于特定系统运行点设计的AGC控制器性能。针对这个问题,本文提出了一种计及风电场附加综合惯量变参数控制影响的AGC源间协调控制策略。在机组层面,实现了基于减载备用状态的风电场综合惯量变参数控制,同时,将这种控制策略在参数切换时引起的系统状态变化计入AGC控制器参数设计之中,实现了对系统状态变化的跟随,提高了频率响应特性;在源间协调层面,将风电场纳入电网调频调度体系,并依据风速以及风电调频备用容量动态调整功率分配系数,使风电场在可用功率范围内参与电力系统二次调频,保障风电场持续并网运行。更多还原

【Abstract】 With the increasing penetration of non-synchronous generator power sources represented by renewable energy such as wind power,the dominant position of synchronous generator power sources in the power system will be broken,and the operation characteristics of the power system will change fundamentally.Inertia control technology is a solution to the problem of equivalent inertia reduction caused by wind power integration.By simulating the inertia response and power frequency droop characteristics of synchronous generators,the frequency stability of power system is improved.Nevertheless,it will also cause the electromechanical scale coupling between the non-synchronous generator power sources and the synchronous generator power sources in the system,superimposed on the uncertainty of wind power output,which leads to the difficulty in power system stability analysis and control system design.Therefore,revealing the influence mechanism of wind turbine inertia control on the stability of power system has important theoretical value and engineering significance.Meanwhile,in the face of complex and changeable operating conditions,how to make use of the advantages of flexible and controllable inertia of wind power,rationally configure the inertia control parameters to meet different control objectives,optimize the performance of frequency regulation controller,improve the frequency response characteristics of the system are also the problems that need to be solved urgently in the current wind power inertia control technology research.In this dissertation,doubly-fed induction generators(DFIGs),which is the mainstream application of wind farm,is taken as the research object,and the synthetic inertia(SI)control technology is selected as the realization route of wind power participating in frequency regulation,and the following research work is carried out:(1)The dynamic interaction model between the DFIG subsystem with additional SI control and the single machine infinite bus subsystem is established.The block diagram of Phillips-Heffron model is drawn.The influence path and mechanism of SI control of wind turbine on power system stability are analyzed by using damping torque analysis method.Meanwhile,based on the relationship between wind turbine access point frequency and power system frequency,a linear small signal model is established to further analysis the influence trend of SI control parameters of wind turbine on damping ratio and oscillation frequency of the system.It is pointed out that different SI control parameters and wind power penetration rate will affect the system oscillation mode and the damping torque provided by the wind turbine to the system electromechanical oscillation loop,and unreasonable parameter configuration will even lead to negative damping torque.Moreover,the dynamic characteristics of wind turbine are coupled with system dynamics,and the effect of the control parameters on the system oscillation mode is affected by the inertia and damping level of the system.(2)Based on the virtual inertia of power system,the concept of virtual damping is proposed,and the significance of virtual damping to improve system stability is pointed out.The mathematical relationship between the SI differential control parameter and virtual inertia,as well as the SI droop control parameter and virtual damping is derived.Meanwhile,in view of the coordination problem between the additional SI control parameters,a novel control strategy combining the online identification of the dominant oscillation mode of the system and the particle swarm optimization(PSO)is proposed.By making full use of the virtual inertia and virtual damping,the stability of the power system under high wind power penetration is further improved,and the multi-objective comprehensive optimization of frequency stability and power angle stability under multi-operation scenarios of the power system is achieved.(3)The grid-connected wind turbines with controllable inertia introduce new inertia and damping characteristics to the power system.This new characteristic is affected by the inertia control parameters of wind turbine and coupled with the original inertia and damping characteristics of the system,which increases the complexity of system stability control.To solve this problem,based on the power balance principle,the equivalent rotor motion model of the synchronous generator considering the influence of the SI control is established,and the control influence and fault factors are uniformly expressed as the parameter perturbation of the equivalent inertia and bounded uncertain disturbance.Then,by using the sliding mode variable structure method,combined with the variability and controllability of the equivalent inertia and equivalent damping,an adaptive robust-sliding mode control(AR-SMC)strategy is proposed to improve the power system stability.The theoretical derivation and simulation analysis show that compared with the traditional inertia control method,AR-SMC control strategy can better reduce the frequency change rate,suppress the relative power angle oscillation amplitude and improve the system stability.(4)The SI variable parameter method for wind turbines can better take into account the system frequency response characteristics and rotor operation safety under different wind velocities.However,the dynamic change of control parameters will also change the system state during operation,thus affecting the performance of AGC controller designed based on specific system operating points.To solve this problem,this dissertation proposes an AGC inter-source coordinated control strategy considering the influence of wind farm additional SI variable parameter control.At the wind turbine level,the SI variable parameter control based on load shedding reserve state is realized.Meanwhile,the system state change caused by parameter switching of this control strategy is included in the parameter design of AGC controller,which realizes the following of system state change and improves the frequency response characteristics.At the level of inter source coordination,the wind farm is included in the frequency regulation dispatching system of the power system,and the power distribution coefficient is dynamically adjusted according to the wind velocity and the reserve capacity of wind power frequency regulation,so that the wind farm can participate in the secondary frequency regulation of the power system within the available power range to ensure the continuous grid-connected operation of the wind farm.更多还原