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In this paper, the holomorphic embedding power flow method (HELM) is designed to solve the AC/DC hybrid power flow equations. According to the power flow model of the high voltage direct current systems (HVDC), an appropriate embedding technique with three recursive algorithms is developed for three different control modes, which is compatible with existing achievements of HELM for AC systems. In this method, the advantages of HELM, such as non-iterative, deterministic and non-ambiguous, are fully retained. In addition, a new calculation strategy based on Bauer's Eta algorithm is designed for the implementation of Pade approximations and the recursive process to avoid redundant calculations without reducing accuracy. In order to verify the reliability and effectiveness of the proposed extended HELM, several power flow cases with different scale are studied by HELM and traditional iterative method.
Yudi Zhao; Chongtao Li; Tao Ding; Zhiguo Hao; Fangxing Li. Holomorphic Embedding Power Flow for AC/DC Hybrid Power Systems Using Bauer's Eta Algorithm. IEEE Transactions on Power Systems 2020, 36, 3595 -3606.
AMA StyleYudi Zhao, Chongtao Li, Tao Ding, Zhiguo Hao, Fangxing Li. Holomorphic Embedding Power Flow for AC/DC Hybrid Power Systems Using Bauer's Eta Algorithm. IEEE Transactions on Power Systems. 2020; 36 (4):3595-3606.
Chicago/Turabian StyleYudi Zhao; Chongtao Li; Tao Ding; Zhiguo Hao; Fangxing Li. 2020. "Holomorphic Embedding Power Flow for AC/DC Hybrid Power Systems Using Bauer's Eta Algorithm." IEEE Transactions on Power Systems 36, no. 4: 3595-3606.
Subsynchronous oscillation (SSO) is a critical issue for the direct-drive permanent magnet synchronous generator (D-PMSG) based wind farm integrated to a weak onshore AC grid. To analyze the mechanism of the SSO phenomenon of D-PMSG based wind farm, widely used impedance-based stability analysis method is utilized in this paper. First, the impedance model based on the harmonic linearization theory of grid-connected D-PMSG is proposed, and the mechanism of sub/supsynchronous currents coupling is analyzed quantitatively for the first time. Then, based on the impedance model and relative stability criterion, the influence of wind farm operating parameters and grid impedance on stability is discussed. Simulations are carried out to verify the correctness of theoretical analysis.
Saijun Yuan; Zhiguo Hao; Tao Zhang; Xiaotian Yuan; Jin Shu. Impedance Modeling Based Method for Sub/Supsynchronous Oscillation Analysis of D-PMSG Wind Farm. Applied Sciences 2019, 9, 2831 .
AMA StyleSaijun Yuan, Zhiguo Hao, Tao Zhang, Xiaotian Yuan, Jin Shu. Impedance Modeling Based Method for Sub/Supsynchronous Oscillation Analysis of D-PMSG Wind Farm. Applied Sciences. 2019; 9 (14):2831.
Chicago/Turabian StyleSaijun Yuan; Zhiguo Hao; Tao Zhang; Xiaotian Yuan; Jin Shu. 2019. "Impedance Modeling Based Method for Sub/Supsynchronous Oscillation Analysis of D-PMSG Wind Farm." Applied Sciences 9, no. 14: 2831.
With the development of PMUs in power systems, the response-based real-time emergency control becomes a promising way to prevent power outages when power systems are subjected to large disturbances. The first step in the emergency control is to start up accurately and fast when needed. To this end, this paper proposes a well-qualified start-up scheme for the power system real-time emergency control. Three key technologies are proposed to ensure the effectiveness of the scheme. They are an instability index, a Critical Machines (CMs) identification algorithm and a two-layer Single Machine Infinite Bus (SMIB) equivalence framework. The concave-convex area based instability index shows good accuracy and high reliability, which is used to identify the transient instability of the system. The CMs identification algorithm can track the changes of CMs and form the proper SMIB system at each moment. The new two-layer SMIB equivalence framework, compared with conventional ones, can significantly reduce the communication burden and improve the computation efficiency. The simulations in two test power systems show that the scheme can identify the transient instability accurately and fast to restore the system to stability after the emergency control. Besides, the proposed method is robust to measurement errors, which enhances its practicality.
Songhao Yang; Zhiguo Hao; Baohui Zhang; Masahide Hojo. An Accurate and Fast Start-Up Scheme for Power System Real-Time Emergency Control. IEEE Transactions on Power Systems 2019, 34, 3562 -3572.
AMA StyleSonghao Yang, Zhiguo Hao, Baohui Zhang, Masahide Hojo. An Accurate and Fast Start-Up Scheme for Power System Real-Time Emergency Control. IEEE Transactions on Power Systems. 2019; 34 (5):3562-3572.
Chicago/Turabian StyleSonghao Yang; Zhiguo Hao; Baohui Zhang; Masahide Hojo. 2019. "An Accurate and Fast Start-Up Scheme for Power System Real-Time Emergency Control." IEEE Transactions on Power Systems 34, no. 5: 3562-3572.
The voltage-source converter (VSC) based high-voltage direct-current (HVDC) grid is an effective means for large-scale integration of renewable energies. This paper proposes a pilot protection scheme as the backup protection for transmission lines in VSC-HVDC grid. The traveling wave (TW) propagating processes and waveform characteristics at both ends of the transmission line are analyzed under different fault conditions. Based on the different characteristics between internal and external fault conditions, the protection is formulated utilizing similarity measure of TW waveforms. A four-terminal VSC-HVDC grid is modelled on PSCAD/EMTDC platform to test the performance of the proposed protection. Various simulation results demonstrate that the proposed protection is able to accurately discriminate internal faults from external faults and identify the faulty pole. The protection performance analysis shows that the protection is insensitive to fault resistance, protection sampling rate and the inductance value of the reactors at the end of lines. The protection algorithm is simple with small calculation amount, and does not require data synchronism. Furthermore, the proposed protection has superiority in fault resistance withstand ability compared with other backup protections.
Yanting Wang; Zhiguo Hao; Baohui Zhang; Fei Kong. A Pilot Protection Scheme for Transmission Lines in VSC-HVDC Grid Based on Similarity Measure of Traveling Waves. IEEE Access 2018, 7, 7147 -7158.
AMA StyleYanting Wang, Zhiguo Hao, Baohui Zhang, Fei Kong. A Pilot Protection Scheme for Transmission Lines in VSC-HVDC Grid Based on Similarity Measure of Traveling Waves. IEEE Access. 2018; 7 (99):7147-7158.
Chicago/Turabian StyleYanting Wang; Zhiguo Hao; Baohui Zhang; Fei Kong. 2018. "A Pilot Protection Scheme for Transmission Lines in VSC-HVDC Grid Based on Similarity Measure of Traveling Waves." IEEE Access 7, no. 99: 7147-7158.
The UHVDC transmission system has been increasingly used because of the advantages in long distance and large capacity transmission. However, the existing traveling-wave-based protection for UHVDC transmission lines is not sensitive enough to properly detect the internal fault with high fault resistance. A novel traveling-wave-based protection scheme for bipolar UHVDC lines is proposed in this paper. The discriminative characteristic between the internal and external fault, embodied in the backward traveling wave, is extracted to formulate the main protection criterion. The faulty line is identified by the polarity of the voltage fault component. In addition, only the single-pole voltage and current of rectifier side are required for the proposed protection scheme. The simulation and field data tests show that the proposed protection scheme can make a correct identification of the fault section and selection of the faulty line in the ± 800 kV UHVDC system and ±500 kV HVDC system. Besides, the proposed protection can correctly detect the grounding fault with fault resistance up to 500 Ω.
Fei Kong; Zhiguo Hao; Baohui Zhang. A Novel Traveling-Wave-Based Main Protection Scheme for $\pm $800 kV UHVDC Bipolar Transmission Lines. IEEE Transactions on Power Delivery 2016, 31, 2159 -2168.
AMA StyleFei Kong, Zhiguo Hao, Baohui Zhang. A Novel Traveling-Wave-Based Main Protection Scheme for $\pm $800 kV UHVDC Bipolar Transmission Lines. IEEE Transactions on Power Delivery. 2016; 31 (5):2159-2168.
Chicago/Turabian StyleFei Kong; Zhiguo Hao; Baohui Zhang. 2016. "A Novel Traveling-Wave-Based Main Protection Scheme for $\pm $800 kV UHVDC Bipolar Transmission Lines." IEEE Transactions on Power Delivery 31, no. 5: 2159-2168.
A transient stability control system for the electric power system composed of a prediction method and a control method is proposed based on trajectory information. This system, which is independent of system parameters and models, can detect the transient stability of the electric power system quickly and provide the control law when the system is unstable. Firstly, system instability is detected by the characteristic concave or convex shape of the trajectory. Secondly, the control method is proposed based on the analysis of the slope of the state plane trajectory when the power system is unstable. Two control objectives are provided according to the methods of acquiring the far end point: one is the minimal cost to restore the system to a stable state; the other one is the minimal cost to limit the maximum swing angle. The simulation indicates that the mentioned transient stability control system is efficient.
Huaiyuan Wang; Baohui Zhang; Zhiguo Hao. Response Based Emergency Control System for Power System Transient Stability. Energies 2015, 8, 13508 -13520.
AMA StyleHuaiyuan Wang, Baohui Zhang, Zhiguo Hao. Response Based Emergency Control System for Power System Transient Stability. Energies. 2015; 8 (12):13508-13520.
Chicago/Turabian StyleHuaiyuan Wang; Baohui Zhang; Zhiguo Hao. 2015. "Response Based Emergency Control System for Power System Transient Stability." Energies 8, no. 12: 13508-13520.