Power System Nonlinear Modal Analysis Using Computationally Reduced Normal Form Method

Nnaemeka Sunday Ugwuanyi,Xavier Kestelyn,Bogdan Marinescu,Olivier Thomas

doi:10.3390/en13051249

Abstract

Increasing nonlinearity in today’s grid challenges the conventional small-signal (modal) analysis (SSA) tools. For instance, the interactions among modes, which are not captured by SSA, may play significant roles in a stressed power system. Consequently, alternative nonlinear modal analysis tools, notably Normal Form (NF) and Modal Series (MS) methods are being explored. However, they are computation-intensive due to numerous polynomial coefficients required. This paper proposes a fast NF technique for power system modal interaction investigation, which uses characteristics of system modes to carefully select relevant terms to be considered in the analysis. The Coefficients related to these terms are selectively computed and the resulting approximate model is computationally reduced compared to the one in which all the coefficients are computed. This leads to a very rapid nonlinear modal analysis of the power systems. The reduced model is used to study interactions of modes in a two-area power system where the tested scenarios give same results as the full model, with about 70% reduction in computation time.

Highlights

The paradigm shift in power generation does not leave the power system without many challenges.The vast majority of renewable energy (RE) generations and proliferation of electrical vehicle (EV)charging stations lead to complex behaviour of the grid [1]
The test system is IEEE 9-bus power system [41] shown in Figure 1 which has been used in the literature to study modal interaction [36,40]
Every other parameters have their usual meanings. It is a small power system containing 20 states, but large enough to demonstrate the Normal Form (NF) problem solved in this paper

Summary

Introduction

The paradigm shift in power generation does not leave the power system without many challenges.The vast majority of renewable energy (RE) generations and proliferation of electrical vehicle (EV)charging stations lead to complex behaviour of the grid [1]. The paradigm shift in power generation does not leave the power system without many challenges. The vast majority of renewable energy (RE) generations and proliferation of electrical vehicle (EV). Charging stations lead to complex behaviour of the grid [1]. As highlighted in [2,3], the penetration of RE introduces new oscillations and stability related issues. Converters interfacing these new technologies to the grid raise some concerns. The PE converters could form a virtual capacitance, which could interact with the AC grid to trigger an unstable subsynchronous oscillation in a relatively weak system [4]. Each type of RE or EV creates challenges ranging from over-voltage, under-voltage, harmonics, stability issues, and many more

Objectives

Results

Conclusion