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.

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This paper provides a comprehensive analysis of local and concurrent commutation failure (CF) of multi-infeed high-voltage direct current (HVDC) system considering multi-infeed interaction factor (MIIF). The literature indicates that the local CF is not influenced by MIIF, whereas this paper concludes that both the local CF and concurrent CF are influenced by MIIF. The ability of remote converter to work under reduced reactive power enables its feature to support local converter via inter-connection link. The MIIF measures the strength of electrical connectivity between converters. Higher MIIF gives a clearer path to remote converter to support local converter, but at the same time, it provides an easy path to local converter to disturb remote converter under local fault. The presence of nearby converter increases the local commutation failure immunity index (CFII) while reducing concurrent CFII. Higher MIIF causes reactive power support to flow from remote converter to local converter, which reduces the chances of CF. A mathematical approximation to calculate the increase in local CFII for multi-infeed HVDC configurations is also proposed. A power flow approach is used to model the relation between MIIF and reactive power support from remote end. The local and concurrent CFIIs are found to be inverse to each other over MIIF; therefore, it is recommended that there is an optimal value of MIIF for all converters in close electric proximity to maintain CFII at a certain level. The numerical results of established model are compared with PSCAD/EMTDC simulations. The simulation results show the details of the influence of MIIF on local CF and concurrent CF of multi-infeed HVDC, which validates the analysis presented.

Validation of power system simulation models is essentially a similarity analysis problem based on multivariate time series. With the development of the internet of things (IoT) technology in the power system, the interoperability and integration of devices in the practical project are improved, and the cross interaction in the simulation process becomes more complex correspondingly. It is critical to explore the inherent correlation from the high dimensional data to evaluate the credibility and to locate the error of the simulation model. Thus, a model validation method based on factor analysis and the Prony method is proposed in this paper. Firstly, the multivariate time series of the simulation model and the practical/acknowledged system are replaced by a low number of common factors with physical meanings by factor analysis. Secondly, the modified adaptive Prony method is applied to extract the features of each common factor to ensure the best fitting of the non-stationary signal. Then the complete similarity evaluation model of the simulation system is established based on energy proportion, information entropy, and variance of the contribution rate. Finally, the error location is identified in the evaluation process based on the physical meaning of extracted features. The feasibility and effectiveness of the proposed method are verified by an application in the simulation model of a power electronics system developed in PSASP. INDEX TERMS Validation of simulation model, power system, Internet of Things, similarity evaluation, high dimensional time series.

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.