新能源電源故障暫態(tài)特性研究

畢天姝 劉素梅 薛安成 楊奇遜

摘 要：以風電、光伏發(fā)電為代表的新能源電力發(fā)展迅猛，其對電力系統(tǒng)保護與安全的影響不容忽視。然而由于風電、光伏發(fā)電等新能源電源與傳統(tǒng)火電電源相比，在發(fā)電機理、并網(wǎng)方式與運行控制技術等方面有較大差異，導致新能源電源的故障暫態(tài)特性難以用已有方法分析研究。為此，針對目前兩大類主流的新能源電源包括全功率變換器型（永磁直驅風力發(fā)電機組和光伏電池組件等）和部分功率變換器型（雙饋風力發(fā)電機組）電源，研究其故障暫態(tài)特性對于開展大規(guī)模新能源電源接入電網(wǎng)后保護適應性評估及繼電保護新原理研究具有重要意義。針對全功率變換型能源電源，分析了故障位置、故障類型、電源本體輸入功率及接入臺數(shù)、故障期間有功和無功功率支撐水平，以及所接電網(wǎng)短路容量等對其對稱與不對稱故障暫態(tài)特性的影響規(guī)律，全面揭示了該類型電源的故障暫態(tài)特性。在故障發(fā)生及切除后的暫態(tài)過程中全功率變換型能源電源提供的故障電流會在短時間內(nèi)迅速上升或下降，且包含較大直流、二倍和三倍基頻諧波量。在故障期間的準穩(wěn)態(tài)過程中，全功率變換型電源將可能運行于并網(wǎng)控制和低電壓穿越控制兩種模式。在出口電壓跌落較嚴重、直流輸入功率較大、所接系統(tǒng)短路容量較小時，低電壓穿越控制將更易起作用。在低電壓穿越控制模式下電源輸出故障相電流的最大值等于變換器最大允許電流（一般為1.5～2 pu，同步發(fā)電機所提供故障電流約為5～10 pu）。而運行于并網(wǎng)控制模式下的電源輸出的故障電流小于2 pu，大小由直流輸入功率、出口處電壓變化程度及功率因數(shù)決定。針對部分功率變換型能源電源，分析了故障發(fā)生時刻、故障位置、故障類型、風速、故障期間無功功率支撐水平等對其對稱與不對稱故障暫態(tài)特性的影響規(guī)律，從而揭示了該類型電源在故障下的電磁暫態(tài)特性。在故障發(fā)生及切除初始階段，由于電網(wǎng)電壓突變，該電源輸出電流中將包含較大的接近直流的衰減分量和負序分量（不對稱故障），這些電流分量主要由雙饋發(fā)電機本身的暫態(tài)響應特性決定。故障發(fā)生或切除一段時間后，隨著定子磁鏈直流分量的衰減，且由于轉子勵磁變換器控制逐漸發(fā)生作用，該電源的故障暫態(tài)特性將不僅受雙饋發(fā)電機本身故障暫態(tài)響應特性影響，還會受到轉子勵磁變換器的控制影響。故障后穩(wěn)態(tài)階段，該新能源電源的故障特性主要與其運行控制模式有關，包括正常并網(wǎng)運行控制模式和低電壓穿越運行兩種模式。在不同運行模式下，部分功率變換型電源輸出的故障電流不同，但故障穩(wěn)態(tài)電流的最大值不超過額定電流值的3倍。

關鍵詞：全功率變換型新能源電源 部分功率變換型新能源電源 電磁暫態(tài)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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