An Optimal Frequency Control Method of Asynchronous Power Grid Considering Multi-HVDC Emergency Power Support

Abstract

Emergency DC power support has become an effective frequency stability control approach. For the asynchronous power grid with multi-HVDC links, this paper proposes an optimal control based on wide-area measurements (WAMS). The prominent advantage of this control is to improve the frequency stability of the disturbed grid while taking into account the influence on power flow, node voltage and other grid frequency fluctuations. In order to evaluate the post-disturbance frequency stability, a steady-state frequency prediction model based on WAMS data is first proposed, which can reflect the correspondence between post-disturbance steady-state frequency and the DC power support amount. In order to obtain the optimal control strategy, an optimization model is established to formulate the proposed control problem. The optimization objective of the model is to minimize the frequency deviation of interconnected power grids, and the constraints are to restore steady-state frequency to target value and ensure the security of line power flow and node voltage. The final control strategy is obtained by solving the optimization model. Simulations of the modified IEEE 50-generator system are performed to validate the accuracy of the proposed frequency prediction model and the effectiveness of the proposed frequency stability control.INDEX TERMS Asynchronous power grid with multi-HVDC links, WAMS, frequency prediction, emergency DC power support, optimal frequency control.

Performance analysis of voltage source converter based high voltage direct current line under small control perturbations

“…Consequently, disturbances may be applied to the following variables: the reference active power of the first station Pref.1, the reactive power at the first converter station Qref.1, and the reference dc voltage is applied at the second converter station Ud-ref. 2. In order to determine the model's starting time, it is first run initially without any disturbances; then, a disturbance consisting of a-0.1 pu step input is applied individually to each of Pref.1, Qref.1 and Ud-ref.2 at t =1.5 seconds.…”

Fast Evaluation Method for Steady State Frequency of Multi-DC Interconnected Asynchronous Power Grid after DC Blocking

“…Adjusting DC line power includes emergency power support and DC system frequency modulation. The response time of DC emergency power support is fast, and the long-term overload capacity can reach 20% [3][4][5]. For the model of Equation (1), only one DC support quantity ∆P sup needs to be added to the power setting P dset , and the adjusted power setting value can be expressed as:…”

Suppression of Power Angle Oscillation Among Synchronous Generators by Optimizing Steady–State Power of High-Voltage DC

“…For the HVDC line, the converters, the DC line, and the controller are described in (2) to (4), noted as d1, d2, and d3 in (5), where  is the power factor, X is the reactance,  is the extinction angle, and x is the DC variable. In Fig.…”

“…With the merit of large-capacity, long-distance transmission, the high-voltage DC (HVDC) is popular in recent years [1], [2], [3], which changes the power flow and the output of the synchronous generator (SG), and may be applied to suppress angular oscillation of the SGs in AC/UHVDC systems [4], [5], [6]. The existing research focuses on the optimal power distribution of the AC/HVDC [7], [8], [9] and the emergency support from the HVDC power [10], [11], [12],…”