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

Abstract

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 multiinfeed 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.

Interaction Mechanism and Coordinated Control of Commutation Failure Prevention in Multi-Infeed Ultra-HVDC System

“…According to (16), Q d increases as the reduction of α and the rise of c, which is exactly consistent with the mechanism of CFPREV control. So, the application of CFPREV control will enlarge the commutation margin of inverters, augmenting the reactive power consumption of the DC system, and further cause the voltage drop of the AC bus in the fault transient process.…”

“…e article [15] comes up with AC/DC voltage interaction factor (ADVIF) to assess voltage interaction between AC buses through impedance parameters of AC network. References [16,17] consider the distribution of real and reactive power in interaction quantization, using the minimum eigenvalue of AC-DC Jacobian matrix and interactive effective short-circuit ratio, respectively, to determine the stability condition of the multi-infeed system. References [18,19] point out that the harmonic component generated in the transient process is also involved in the interaction between inverter stations and accordingly put forward critical indexes to evaluate the risk of CCFs caused by interaction.…”

Small-Signal Stability Analysis of the Asymmetrical Dc Operation in Hvdc Networks

“…where the linear expressions that describe the DC currents Δi m+ dc and Δi m− dc are presented in (17) and the linear expression for Δi b+ dc and Δi b− dc is obtained in (18).…”

“…Most research papers in literature assess stability from a symmetrical DC operation perspective. For example, the control interactions and their design were analyzed in [15,16]; the effect of a new connection of an HVDC station on DC voltage stability was studied in [17]; [18,19] examined the influence of the DC power flow direction on stability; power and DC voltage oscillations were investigated in [20,21]. Even the stability of systems with line-commutated converters (LCCs) and VSCs has been evaluated [21,22].…”