新能源电源故障暂态特性研究

毕天姝 刘素梅 薛安成 杨奇逊

摘 要：以风电、光伏发电为代表的新能源电力发展迅猛，其对电力系统保护与安全的影响不容忽视。然而由于风电、光伏发电等新能源电源与传统火电电源相比，在发电机理、并网方式与运行控制技术等方面有较大差异，导致新能源电源的故障暂态特性难以用已有方法分析研究。为此，针对目前两大类主流的新能源电源包括全功率变换器型（永磁直驱风力发电机组和光伏电池组件等）和部分功率变换器型（双馈风力发电机组）电源，研究其故障暂态特性对于开展大规模新能源电源接入电网后保护适应性评估及继电保护新原理研究具有重要意义。针对全功率变换型能源电源，分析了故障位置、故障类型、电源本体输入功率及接入台数、故障期间有功和无功功率支撑水平，以及所接电网短路容量等对其对称与不对称故障暂态特性的影响规律，全面揭示了该类型电源的故障暂态特性。在故障发生及切除后的暂态过程中全功率变换型能源电源提供的故障电流会在短时间内迅速上升或下降，且包含较大直流、二倍和三倍基频谐波量。在故障期间的准稳态过程中，全功率变换型电源将可能运行于并网控制和低电压穿越控制两种模式。在出口电压跌落较严重、直流输入功率较大、所接系统短路容量较小时，低电压穿越控制将更易起作用。在低电压穿越控制模式下电源输出故障相电流的最大值等于变换器最大允许电流（一般为1.5～2 pu，同步发电机所提供故障电流约为5～10 pu）。而运行于并网控制模式下的电源输出的故障电流小于2 pu，大小由直流输入功率、出口处电压变化程度及功率因数决定。针对部分功率变换型能源电源，分析了故障发生时刻、故障位置、故障类型、风速、故障期间无功功率支撑水平等对其对称与不对称故障暂态特性的影响规律，从而揭示了该类型电源在故障下的电磁暂态特性。在故障发生及切除初始阶段，由于电网电压突变，该电源输出电流中将包含较大的接近直流的衰减分量和负序分量（不对称故障），这些电流分量主要由双馈发电机本身的暂态响应特性决定。故障发生或切除一段时间后，随着定子磁链直流分量的衰减，且由于转子励磁变换器控制逐渐发生作用，该电源的故障暂态特性将不仅受双馈发电机本身故障暂态响应特性影响，还会受到转子励磁变换器的控制影响。故障后稳态阶段，该新能源电源的故障特性主要与其运行控制模式有关，包括正常并网运行控制模式和低电压穿越运行两种模式。在不同运行模式下，部分功率变换型电源输出的故障电流不同，但故障稳态电流的最大值不超过额定电流值的3倍。

关键词：全功率变换型新能源电源 部分功率变换型新能源电源 电磁暂态模型 故障特性

Abstract：The penetration of renewable energy sources， especially for wind power and photovoltaic， is increasing rapidly in recent years. As a result， these renewable generators （RGs） have greatly affected the existing protection. As compared with the traditional synchronous generators， the RGs are different on the electricity generation principles， integration topology and control mode， which make their fault behaviors change accordingly. Therefore， the conventional fault analysis method can not be used for estimating the fault contribution of RGs. Hence， the fault characteristics are studied systematically for two main types of RGs， i.e. full- and partial-rated converter interfaced RGs. For full-rated converter interfaced RGs， the impact factors on their symmetrical and asymmetrical fault characteristics are thoroughly studied， such as fault locations and types， dc input power and rated capacity of the RGs， real and reactive power level delivered to grid， and so on. After fault occurrence and its clearance， the fault current from RGs quickly increases （decreases）， and include abundant harmonious like dc component， 100 Hz and 150 Hz frequency components. During the faulty steady period， the fault characteristics of RGs are decided by the normal integration control or fault ride through （FRT） control. With the action of FRT control， the maximum faulty current from RGs is limited within the inverters ampere constraint （generally 1.5～2 pu）. If the normal integration control is employed， the fault current is always less than the constraint， and calculated by dc input power， the dip depth of grid voltage and power factors at the inverter pole. For partial-rated converter interfaced RGs， the main impact factors on their balanced and unbalanced fault behaviors are also systematically analyzed， including fault occurrence times， fault locations an types， wind speed and so on. During the transient process of fault occurrence and its clearance， due to the voltage dip， the fault current of RGs includes larger near-dc and negative-sequence component. These components are mainly influenced by the transient behaviors of doubly fed induction generators （DFIGs）. After the transient periods， as the dc component of stator flux is exponentially damping， the fault characteristics of RGs are related to the transient responses of DFIG and its control mode. During the plateau periods of faults， the fault characteristics are determined by the converters control mode.

Key Words：Full-rated converter interfaced renewable generator；Partial-rated converter interfaced renewable generators；Electromagnetic model；Fault characteristic

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