Power System Monitoring and Control by Yasunori Mitani & Masayuki Watanabe & Hassan Bevrani

Author:Yasunori Mitani & Masayuki Watanabe & Hassan Bevrani [Yasunori Mitani]
Language: eng
Format: epub
Tags: Engineering
Publisher: Wiley-IEEE Press
Published: 2014-06-08T16:00:00+00:00

8.3 Simultaneous Voltage and Frequency-Based LS

8.3.1 Proposed LS Scheme

As mentioned, the UFLS and UVLS schemes work in the power system without any coordination. The interaction between voltage and frequency responses is neglected in these schemes. Therefore, the risk of LS schemes malfunction can appear in real-world power systems. From previous descriptions and the performed simulation results, it is realized that considering just frequency or voltage indices cannot lead to an effective/optimal LS plan, especially when the reactive power is incorporated in the studies.

Since the coordination between conventional UFLS and UVLS as separate algorithms is difficult and even impossible, both voltage and frequency should be used in the same LS program simultaneously. With this target in mind, one can define a new graphical analysis tool to monitor both voltage and frequency in one LS algorithm. As shown in Chapter 4 (Section 4.4), the frequency–voltage Δv–Δf graph can be used as a useful graphical tool to see the state of the system following a contingency.

Here, for calculation of the LSCSi (4.21), the and parameters are considered as given in Table 8.1. It can be seen that in order to present a reasonable comparison between the UFLS scheme and the proposed underfrequency/voltage LS (UFVLS) scheme, the LS parameters are selected as close as possible to the LS strategy introduced by the FRCC [21]. The maximum number of LS steps and the amount of needed loads for shedding per step are also considered similar to the FRCC control plan. Furthermore, the parameters are selected the same as the frequency thresholds used in the FRCC scheme. Therefore, by fixing variable in (4.21) at zero, the proposed algorithm acts similar to the FRCC's UFLS program.

Table 8.1 The LS Parameters

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