This paper presents a detailed analysis of commutation failure, AC/DC power flow, and voltage stability of multi-infeed high-voltage direct current (HVDC). The use of HVDC power transmission technology has become common in modern power systems. During the past two decades, HVDC technology has been extensively used for long-distance bulk power transmission to remote areas. Throughout the world, the demand for power has drastically increased in recent years due to industrialization; such situations make HVDC an economic candidate because the distance between power generation plants and load areas is significantly very long. The line-commutated converter (LCC) technology-based HVDC system is well more mature than other available conversion schemes (i.e., voltage source converters), and it is widely used in high-power projects. China had approximately 50 HVDC–LCC links in 2020, and a single LCC-based link with the highest capacity is 12 GW. The installation of several HVDC links in an existing power network has led to a situation where two or more HVDC links terminate in the electric vicinity of each other’s AC network or even in same AC busbar. Such scenarios are termed multi-infeed HVDC system. Multi-infeed HVDC systems bring various challenges related to voltage stability, local and concurrent commutation failure, and AC/DC power flow. Here, the literature available on these phenomena of LCC-based HVDC is discussed for future research. The assumptions and drawbacks of various techniques used for investigating the mentioned phenomena are also highlighted.

Here, a novel approach is proposed to compute discrete value of converter tap position in AC/DC hybrid multi‐infeed HVDC power flow solution. The approach is based on Newton–Raphson (NR) technique and sequential power flow method. An algorithm for the estimation of discrete tap position is devised by re‐converging DC system to eliminate the error between discrete tap position and actual value of tap. The proposed technique computes new value of gamma for discrete value of tap which solves convergence problem of DC system caused by AC‐voltage fluctuations. Theoretical bases and numerical results are presented to support new proposed approach. The technique is successfully applied to dual‐infeed LCC HVDC feeding into the same AC system which is more practical scenario. The results validate the approach and show advantages in term of accuracy and convergence.

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.