A New STATCOM Model for Power Flows Using the Newton–Raphson Method

Abstract

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An advanced STATCOM model for optimal power flows using Newton's method

“…The reactive power property of the converter is modeled using a variable shunt branch susceptance to account for the calculated reactive power (either generation or absorption) in the converter depending on its control requirements, which may be set to either direct nodal voltage regulation or reactive power control [1].…”

“…Optimal solutions of the new STATCOM model yield considerable reductions in power system losses and in the converter's internal power losses, when compared to the solutions furnished by the STATCOM model solved using conventional power flows [1]. Furthermore, optimal solutions with the new STATCOM model will also yield improved solutions compared to the optimal solutions provided by the voltage source representation of the STATCOM, and with less computational complexity.…”

“…This is not dissimilar to the way in which synchronous condensers are represented in power flow studies. Such a simple concept represents well the fact that at the fundamental frequency, the STATCOM converter's output voltage may be adjusted against the AC system's voltage in the converter to achieve very tight control targets, a capability afforded by the switched-mode converter technology [1]- [9]. Nevertheless, for all its attractiveness this concept fails to explain the operation of the STATCOM from its DC side.…”

“…Some of the most obvious shortcomings of the STATCOM model based on the equivalent voltage source concept are: (i) there is no easy way to ascertain whether or not the converter's operation is within the linear region of operation [10]; (ii) switching losses tend to be neglected; (iii) the internal ohmic losses of the converter along with the effects of the converter's magnetics are normally lumped together with those of the interfacing transformer which, more often than not, is a tap changer. This has provided the motivation to develop a more realistic STATCOM model for fundamental frequency operation [1]; one which overcomes the limitations of the equivalent voltage source representation and is suitable for assessing the impact of both conventional multi-level and modular multi-level converters (MMC) [11]- [12], on large power networks and in an optimal manner. This paper may be considered a companion paper of [1] where the conventional power flow solution of the STATCOM model has been put forward.…”

“…This has provided the motivation to develop a more realistic STATCOM model for fundamental frequency operation [1]; one which overcomes the limitations of the equivalent voltage source representation and is suitable for assessing the impact of both conventional multi-level and modular multi-level converters (MMC) [11]- [12], on large power networks and in an optimal manner. This paper may be considered a companion paper of [1] where the conventional power flow solution of the STATCOM model has been put forward. In the OPF problem -which is the subject matter of this paper -a chosen system objective function (or a group of functions) is solved towards its optimum operating point subject to system's realistic operating boundaries.…”