【作者】 李浩；

【导师】 金建勋；

【作者基本信息】 天津大学 ， 电气工程， 2023， 硕士

【摘要】 规模日益扩大的电动汽车对于电力系统而言是把“双刃剑”:一方面,随机的充电行为给电网带来巨大的负荷冲击,充电设备造成的谐波污染不断恶化电能质量;另一方面,V2G(Vehicle to Grid)技术又使电动汽车作为调节者的身份服务于电力系统,并促进可再生能源消纳。因此,如何充分利用电动汽车资源进行V2G服务并且减少充电带来的危害已成为国内外研究的热点。本文以基于统一电能质量调节器(Unified Power Quality Conditioner,UPQC)-超导磁储能(Superconducting Magnetic Energy Storage,SMES)系统的电动汽车充电站(Electric Vehicle Charging Station,EVCS)为研究对象,实现V2G调节功能的一体化,并对不同场景下的V2G功能提出改进方案,具体内容如下:(1)研究了基于UPQC-SMES的EVCS系统V2G功能一体化的实现方式。首先,介绍了系统整体构成和运行原理,对系统常规运行模式下的综合模型和功率流进行分析。其次,阐述了电压电流补偿量检测原理、功率控制电流信号合成原理和UPQC滞环控制原理,研究了充电桩与SMES系统的控制策略,由此EVCS在充放电运行的同时可通过UPQC全面改善交流侧的电能质量。最后,通过仿真对常规V2G功能以及SMES的瞬态补偿能力进行了验证。(2)针对三相电压暂降/暂升的补偿,提出了一种基于V2G的UPQC-VAmin改进电压补偿方法。首先,介绍了改进方法的原理,该方法在保证负载正常运行的同时,利用电动汽车对发生电压暂降/暂升的电网进行主动功率补偿,从而改善电网功率缺额/盈余的情况,增强电网不正常运行状态的恢复能力并降低UPQC系统VA负荷(Volt-Ampere loading)。其次,将V2G补偿功率作为补偿变量改进UPQC系统的常规VA负荷模型。根据改进模型研究了系统的补偿特性,分析不同补偿参数对UPQC系统VA负荷的影响,推导出系统最优运行状态的补偿条件。再次,总结出两种补偿模式,并制定了补偿参数的选取方法和电动汽车功率的分配原则。在此基础上,分析了改进方法下的系统功率流,进一步阐述不同模式的补偿原理。最后,通过仿真验证了所提改进电压补偿方法的有效性。(3)针对三相电压不平衡电网下网侧功率振荡的问题,提出了基于正负序独立双重控制的网侧二倍频功率振荡抑制策略,保证负载平衡运行的同时提高系统稳定性。首先,介绍了不平衡电压电流中正负序分量的提取方法。其次,研究了应用于UPQC并联侧变换器的正负序独立双重控制策略的原理,并提炼出三种控制目标,通过正负序电流内环的前馈解耦方程确定系统整体控制策略。在此基础上,分析了振荡抑制策略下的系统功率流,进一步阐述了功率振荡的抑制原理,并分析了V2G补偿功率和SMES系统对功率振荡抑制效果的影响。最后,通过仿真验证了所提功率振荡抑制策略的有效性。本文研究成果减少了电动汽车给电力系统带来的消极影响,利用电动汽车与SMES系统的储能特性实现了优势互补、改善了电网的电能质量、提高了可再生能源的消纳,为V2G技术在电能质量调节方面的应用提供了新的思路,同时所提改进补偿方法具有较高的普适性,可扩展应用于其他带有储能装置的UPQC系统。更多还原

【Abstract】 The increasing scale of electric vehicles is a"double-edged sword"for the power system:on the one hand,the random charging behavior brings huge load impact to the grid,and the harmonic pollution caused by charging equipment continuously deterio-rates the power quality;on the other hand,V2G(Vehicle to Grid)technology enables electric vehicles to serve the power system as regulators and promotes renewable en-ergy consumption.In this thesis,an Electric Vehicle Charging Station(EVCS)based on Unified Power Quality Conditioner(UPQC)-Superconducting Magnetic Energy Storage(SMES)system are studied.It achieves the integration of the V2G regulation functions.This thesis also proposes improvement schemes for V2G functions in differ-ent scenarios,as follows:(1)The integration of the V2G function of the EVCS based on UPQC-SMES is studied.Firstly,the overall system composition and operation principle are introduced,and the model and power flow in the conventional operation are analyzed.Secondly,the compensation voltage and current detection principle,power control current signal principle,UPQC hysteresis loop control strategy and the control strategies of the charg-ing piles and SMES are studied.It achieves the charging and discharging operation of EVCS while improving the grid power quality.Finally,the normal V2G function and the SMES compensation capability are verified by simulation.(2)For the compensation of three-phase voltage sag/swell,an improved V2G-based UPQC-VAmin voltage compensation method is proposed.First,the principle of the improved voltage compensation method is introduced.Under the premise of normal load operation,the EVs in improved method actively compensate power to the grid where voltage sag/swell occurs,thus simultaneously improving the power deficit or surplus of the grid and enhancing the recovery capability.Second,the V2G compensa-tion power is used as the variable to improve the VA(Volt-Ampere)loading model of the UPQC system.The compensation characteristics of the system are studied,and the effects of different compensation parameters on the VA loading of the UPQC system are analyzed to obtain the optimal operation state compensation conditions.Then,two compensation modes are summarized,and the compensation parameters selection and the EV power allocation principles are made.The power flow under the improved method is analyzed,and the compensation principles are further elaborated.Finally,the effectiveness of the improved method is verified by simulation.(3)For the grid power oscillation under three-phase voltage unbalanced,a grid-side power oscillation suppression strategy based on independent dual control of posi-tive and negative sequences is proposed to ensure balanced operation of the load while improving system stability.Firstly,the extraction method of positive and negative se-quence components in unbalanced voltage and current is introduced.Secondly,the prin-ciple of the dual control strategy applied to the UPQC parallel-side converter is studied and three control objectives are proposed.The overall system control strategy is deter-mined by the feed-forward decoupling equation of the positive and negative sequence current inner loop.The system power flow under power oscillation suppression is ana-lyzed,the power oscillation suppression principle is further elaborated,and the effects of V2G compensation power and SMES system on the power oscillation suppression effect are analyzed.Finally,the effectiveness of the oscillation suppression strategy based on dual control is verified by simulation.The research results reduce the negative impact brought by electric vehicles on the power system,utilize the energy storage characteristics of electric vehicles and SMES systems to realize complementary advantages,improve the power quality of the grid,improve the consumption of renewable energy,and provide a new idea for the applica-tion of V2G technology in power quality regulation.Meanwhile,the improved com-pensation method proposed has high universality.It can be extended to other UPQC systems with energy storage devices.更多还原