Interaction Assessment and Stability Analysis of the MMC-Based VSC-HVDC Link

This paper investigates the dynamic behavior of a modular multi-level converter (MMC)-based HVDC link. An overall state-space model is developed to identify the system critical modes, considering the dynamics of the master MMC and slave MMC, their control systems, and the HVDC cable. Complementary to the state-space model, an impedance-based model is also derived to obtain the minimum phase margin (PM) of the system. In addition, a relative gain array (RGA) analysis is conducted to quantify the level of interactions among the control systems of master and slave MMCs and their impacts on stability. Finally, with the help of the results obtained from the system analysis (eigenvalue, phase margin, sensitivity, and RGA), the system dynamic performance is improved.

RGA Based Decoupler Design for a Coupled Tank MIMO Process

The objective of this paper is to develop the Relative Gain Array (RGA) based Decoupler design with PI Controller for a MIMO Process. The contrsoller thus developed is implemented on Laboratory interacting coupled tank process through simulation. This can be regarded as the relevant process control in petrol and chemical industries. These industries involve controlling the liquid level and the flow rate in the presence of nonlinearity and disturbance which justifies the use of PI Controller with Decoupler scheme. For this purpose, mathematical models are obtained for each of the input-output combinations using white box approach and the respective controllers are developed. A detailed analysis on the performance of the chosen process with these controllers is carried out. Simulation studies reveal the effectiveness of proposed controller for MIMO process that exhibits nonlinear behaviour.

Studies on Closed-loop Interaction in a Multi-loop Single Tank Control System

This paper investigates the interaction between level and flow loop in a single tank system. The data generated is used to generate all transfer functions via step test method. The model generated is then simulated on MATLAB-Simulink and the obtained results are then compared with experimental results for verification. A Relative Gain Array analysis is performed to check the interaction and comment on the pairing.