Using Decentralized Control Techniques for Interaction Analysis in Hybrid AC/DC Grids

One of the ancillary services that can be provided by Multi-terminal Direct Current (MTDC) grid to connected ac grids is power oscillation damping (POD). However, using PODs at multiple terminals of an MTDC grid results in multi-loop, multi-variable control system. Such control systems inherently have control loop interactions challenge, which can result in reduced performance of one or more controllers. This entails that PODs installed at multiple converter terminals to damp oscillations in respective ac grids could be affected due to unfavorable interactions among the controllers. Thus, compromising the stability of the connected ac grids. This paper presents analyses of interaction between multiple POD controllers installed on MTDC. For a three-terminal study system, insights on interactions between POD controllers at two different converter terminals of an MTDC are obtained using relative gain array and performance relative gain array measures.Using Decentralized Control Techniques for Interaction Analysis in Hybrid AC/DC GridsacceptedVersio

Stability Assessment of Power Systems Based on a Robust Sum-of-Squares Optimization Approach

Secure operation of the evolving power systems, characterised by more renewable energy sources and increasingly variable consumption, will require enhanced monitoring and more automatic control actions. One example is the need for fast detection and control actions to avoid loss of synchronism or grid islanding caused by transient instability. In this paper, we present a method suitable for on-line transient stability assessment of power systems, based on Lyapunov's second method for stability analysis of dynamical systems. The method uses Sum-of-Squares optimization to algorithmically construct a Polynomial Lyapunov Function and estimate the Region-of-Attraction for a given stable operating state. The main benefit of the method is that it obviates the painstaking process of finding a suitable Lyapunov function. Our approach includes a robust handling of the truncation error in the Taylor series expansion of the system model, and thereby ensures that the estimate of the region of attraction around an operating point is inside the actual region of attraction. Using a single-machine-infinite-bus system, we demonstrate the application of the method in this paper

Using Decentralized Control Techniques for Interaction Analysis in Hybrid AC/DC Grids

One of the ancillary services that can be provided by Multi-terminal Direct Current (MTDC) grid to connected ac grids is power oscillation damping (POD). However, using PODs at multiple terminals of an MTDC grid results in multi-loop, multi-variable control system. Such control systems inherently have control loop interactions challenge, which can result in reduced performance of one or more controllers. This entails that PODs installed at multiple converter terminals to damp oscillations in respective ac grids could be affected due to unfavorable interactions among the controllers. Thus, compromising the stability of the connected ac grids. This paper presents analyses of interaction between multiple POD controllers installed on MTDC. For a three-terminal study system, insights on interactions between POD controllers at two different converter terminals of an MTDC are obtained using relative gain array and performance relative gain array measures.Using Decentralized Control Techniques for Interaction Analysis in Hybrid AC/DC GridsacceptedVersio