Applications of eigenvalues in installation ofmulti-infeed HVDCsystem for voltage stability

This research work provides a practical approach to install High Voltage Direct Current (HVDC) link in close vicinity of an existing HVDC system. The work establishes eigenvalue-based approach using modal analysis to give voltage stability conditions for multi-infeed scenario. A detailed analysis of steady state and transient behavior of multi-infeed HVDC system is provided to understand the influence of network impedances. Minimum eigenvalue of AC-DC Jacobian matrix is taken as index to determine stability using a realistic multi-infeed HVDC model. Newton Raphson technique is applied to calculate bus angle and voltage for accurate stability analysis. The inter-converter interaction of multi-infeed HVDC severely affects the performance of AC/DC network. So, it is of great importance to study multi-infeed phenomena with a systematic way to minimize the risk of adverse results. Practical applications of proposed scheme are provided. It has been examined that the behavior of positive eigenvalue largely depends on coupling impedance while impedance between AC busbar and inverters show less control on region of stability. With increase in coupling impedance, multi-infeed interaction factor reduces which reflects less transient over voltage, commutation failure, and stability like problems. Various case studies are provided regarding network impedances to make system voltage stable. The results show that eigenvalues are greatly influenced by associated network impedances. The simulations are performed in MATLAB and PSCAD/EMTDC to verify the analytical results.