Real-Time LCC-HVDC Maximum Emergency Power Capacity Estimation Based on Local PMUs

Abstract

The adjustable capacity of a line-commutatedconverter High Voltage Direct Current (LCC-HVDC) connected to a power system, called the LCC-HVDC maximum emergency power capability or HVDC-MC for short, plays an important role in determining the response of that system to a large disturbance. However, it is a challenging task to obtain an accurate HVDC-MC due to system model uncertainties as well as to contingencies.To address this problem, this paper proposes to estimate the HVDC-MC using a Thevenin equivalent (TE) of the system seen at the HVDC terminal bus of connection with the power system, whose parameters are estimated by processing positive-sequences voltages and currents of local synchrophasor measurements. The impacts of TE potential changes on the impedance estimation under large disturbance have been extensively investigated and an adaptive screening process of current measurements is developed to reduce the error of TE impedance estimation. The uncertainties of phasor measurements have been further taken into account by resorting to the total least square estimation method. The limitations of the HVDC control characteristics, the voltage dependent current order limit, the converter capacity and the AC voltage on HVDC-MC estimation are also considered. The simulations show that the proposed method can accurately track the dynamics of the TE parameters and the real-time HVDC-MC after the large disturbances.

DC Current Order Optimization Based Strategy for Recovery Performance Improvement of LCC-HVDC Transmission Systems

“…Secondly, the TEP estimation method has been extended to the control method or online calculation method of HVDC system in recent years. For example, [10] estimated the maximum real-time power capacity of LCC-HVDC transmission systems, which used total least squares to estimate the TEPs. Reference [1] calculated the TEPs by the impedance circle at different time instants, and then selected a FA deduction based on the comparison between preand post-fault values of TEPs to reduce the risk of first CF, which requires a quite fast reaction of TEP estimation.…”

“…Reference [9] proposes an improved current-order limiter control, but the interpretation of physical meaning about CF mechanism is still unclear. Reference [10] estimates the maximum power capacity of LCC-HVDC transmission systems after the fault while considering various constraints based on Thevenin equivalent parameters (TEPs); however, the method is not used in the real-time control of LCC-HVDC transmission systems and the SCFs are not considered.…”

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

“…The submatrices of ( 5) are given in ( 16) to (18), and the increment K is obtained in (19). The HVDC power PDC has the influence on the DC current and then changes the power flow solution.…”

“…In [17], DC power support from the dominant generators is derived. In [18], the maximum emergent HVDC power is derived by tracking the Thevenin equivalent.…”

An Observer-Based Composite Identifier for Online Estimation of the Thevenin Equivalent Parameters of a Power System

“…The theoretical basis standing behind this concept is provided by the TE theorem, stating in its original version that any linear circuit constituted by current and/or voltage sources and resistances can be described via an equivalent circuit characterized by a voltage source combined in series with a resistance-a formulation that has been later extended to single-phase and three-phase AC circuits, with the notion of resistance being replaced by the notion of impedance [8]. This representation is suited for the analysis of a variety of key issues for a correct and safe operation of the power converter, ranging from fault studies [13], voltage stability analysis [10], loadability limit computation [11] to tuning of the related controllers [12]. In these studies it is emphasized that, to make the problem tractable in practice, the identification of the TE parameters shall be accomplished using only local measurements of voltage and currents.…”