【作者】 孙鹏；

【导师】 姚骏；

【作者基本信息】 重庆大学 ， 电气工程， 2022， 博士

【摘要】 新能源发电设备同步方式和控制特性与同步发电机组具有显著差异,不同于同步发电机组,新能源发电设备的特性由多个物理储能元件动态及其相应的控制器共同决定。因此,在小扰动下新能源并网系统的激励响应关系复杂,呈现出多时间尺度以及强耦合的特征。同时新能源并网设备采用的同步并网方式与其控制策略也密切相关,其不同同步方式新能源设备并网系统面临着小干扰失稳形态迥异,多样化电源协调控制错综复杂等问题。这种新型的振荡问题严重威胁了新能源发电系统的安稳运行,也制约了新能源的消纳。然而,目前虽然对于不同同步方式新能源并网系统振荡机理及影响因素有所研究,但是缺乏考虑新能源发电系统实际运行条件的详细分析,例如考虑场站中多机组单元以及交流电网短路故障期间的小干扰稳定性分析。此外,对于含不同同步方式混联的新能源并网系统小干扰稳定性分析与控制缺乏相关研究,亟需对混联系统小干扰稳定性进行全面分析并提出相关稳定控制措施。因此,本文首先以跟网型控制双馈发电并网系统为例,分析电网短路故障期间系统小干扰稳定性,探究影响跟网型并网系统小干扰稳定性影响规律,并提出针对性控制策略;其次,以多虚拟同步控制构网型变流器并联并网系统为研究对象,对其振荡失稳机理、振荡影响因素及其多机优化控制策略进行了研究;最后对含虚拟同步控制变流器和跟网型双馈感应发电机的混联并网系统,分析混联系统各控制环节间的相互作用,提出弱化控制环交互的控制策略,以提高混联系统振荡抑制性能。论文的主要研究内容如下:(1)跟网型新能源并网系统由于锁相环控制环节的存在,其控制系统参考坐标系强依赖于电网信息。当电网呈现出弱电网特性或者电网运行状态发生突变时,跟网型新能源并网系统可能会因设备与电网之间的强耦合使得控制系统适应性变差,最终导致系统发生振荡失稳。为了研究跟网型设备与电网的交互作用,以跟网型双馈感应风电系统为例,利用阻抗建模方法,将跟网型双馈并网闭环系统分成电网侧和双馈机组两个开环频域子系统,并对其分别建立阻抗模型。通过比较子系统的频域特性,分析了电网阻抗以及控制系统参数对小干扰稳定性的影响规律。进而,提出一种虚拟电容控制策略,以解决系统在弱电网情况下小干扰失稳问题。通过仿真和实验研究,验证了理论分析的正确性和所提控制策略的有效性。(2)为了探究构网型并网系统小干扰稳定机理及影响因素,首先建立多虚拟同步控制变流器并联并网系统线性化模型,对系统的特征矩阵进行模态分析,进而分析系统连接阻抗、有功控制参数以及系统出力对主导特征根的影响规律。结合稳定性分析结果,为提高多构网型变流器并网系统的小干扰稳定性,分别基于留数指标以及基于混沌和差分进化的混合粒子群优化算法两个方面提出多构网型变流器并网系统的附加阻尼控制策略。并通过仿真和实验验证了理论分析正确性和所提附加阻尼控制方法的有效性。(3)对于含虚拟同步控制变流器与跟网型双馈感应发电机的混联并网系统,利用开环模式谐振理论,将混联系统分解为两个互联开环子系统,建立开、闭环模态分析与子系统间动态交互的联系。从模式相互作用的角度,揭示影响混联系统发生小干扰失稳的机理,探究混联系统中各设备控制环节交互作用。最后利用正规矩阵特性,提出了一种混联系统附加阻尼控制策略,保证混联系统特征根对参数摄动的灵敏度最小,进而避免子系统开环模式谐振,提高混联系统小干扰稳定性。本文针对不同同步方式发电设备并网系统的振荡失稳机理、振荡影响因素、相互作用等一系列关键问题进行深入研究,并分别提出相应的优化控制策略,为解决含多样化设备新能源并网系统小干扰稳定性问题奠定基础。本文研究工作为进一步提高新能源并网消纳及其稳定运行能力提供了理论依据,具有工程应用前景。更多还原

【Abstract】 Synchronous modes and control characteristics of renewable energy equipment are significantly different from those of synchronous generator.The dynamic characteristics of renewable energy grid-connected system(REGS)are determined by the dynamics of multiple physical energy storage components and corresponding controllers.As a result,the dynamic behavior of REGS during small disturbance is complex,which presents the characteristics of multiple time scale and strong coupling in the system.Moreover,the forms of small signal instability are significantly different in different synchronous modes system,which makes the coordinated control of diversified control loops more complicated.Therefore,the small signal instability problem in different synchronous modes control system will seriously threaten the stable operation of REGS.Although the oscillation mechanism and influencing factors of REGS with different synchronous modes have been studied,the detailed analysis considering the actual operating conditions of REGS is lacking.Such as the stability analysis in the case of multiple converters system and short circuit faults in the power grid is rarely studied.In addition,there is a lack of relevant research on the small signal stability analysis and damping controllers of hybrid REGS.Therefore,it is urgent to comprehensively analyze the small signal stability of hybrid system and propose stabilization controller to improve the safety and reliability of hybrid REGS.In order to improve the small signal stable performance of REGS with different synchronous modes.Firstly,doubly fed induction generator(DFIG)is a typical mainstream power generation equipment of REGS.Therefore,this thesis takes the gridfollowing DFIG grid-connected system as an example,which aimed to analyze small signal stability of grid-following system during low voltage ride-through.Secondly,the virtual synchronous generator(VSG)grid-connected system with multiple converters is considered as the research object in this thesis.Furthermore,the oscillation instability mechanism,oscillation influencing factors and multi-converters optimal control strategy is studied.Finally,the interaction between the control loops is analyzed in the hybrid system with VSG and grid-following DFIG,and a damping control strategy is proposed to improve the oscillation suppression performance of the hybrid system.The contents of this dissertation are as follows:(1)When power grid presents the characteristic of weak power grid,the adaptability of grid-following control system may deteriorate due to the strong coupling between the generation equipment and the power grid.Therefore,this thesis takes the grid-following DFIG grid-connected system as an example to analyze small signal stability of grid-following system during low voltage ride-through.Furthermore,the output impedance of grid-side and generator-side are established respectively.The influence law of different parameters on the dynamic stability of the system is explored through comparing the frequency domain characteristics of subsystems.Finally,a virtual capacitor control strategy is proposed from aspect of reducing the electrical connection distance,which can enhance the system small signal stability in the weak power grid.(2)The linearization model of multiple VSG grid-connected system is established.The influence of grid impedance,active power control parameters and output power on the dominant characteristic root is analyzed.Furthermore,combined with residue index,the additional damping control strategy based on hybrid particle swarm optimization algorithm of chaos and differential evolution algorithm is proposed to improve the small signal stability of multiple VSG grid-connected system.The time domain simulation and experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed control schemes.(3)The hybrid grid-connected system with VSG and grid-following DFIG is decomposed into two open-loop subsystems by using open-loop mode resonance theory.Furthermore,the relationship between the open-loop mode analysis and the dynamic interaction is established.From the view of mode interaction,the small signal instability mechanism of hybrid system caused by controller interaction is revealed.Finally,a damping controller is proposed to make the state matrix of the closed-loop system behave as a normal matrix.The closed-loop system has the minimum eigenvalue sensitivity and closed-loop eigenvalue is not sensitive to parameter changes.Therefore,the controller interaction and small signal instability in hybrid grid-connected system can be solved.In this thesis,oscillation instability mechanism,oscillation influencing factors and dynamic interaction of REGS with different synchronization modes are studied in depth.Meanwhile,the optimized control strategies are proposed.The research work in this thesis provides a theoretical basis for further improving the consumption and stable operation ability of REGS,which also has the prospect of engineering application.更多还原