Real-Time Estimation of AC-Grid Short Circuit Capacity for HVDC Control Application

Babazadeh, Davood and Muthukrishnan, Arvind and Mitra, Pinaki and Larsson, Tomas and Nordström, Lars
IET Generation, Transmission and Distribution
Being able to estimate the AC grid strength using Short Circuit Capacity (SCC) fromthe perspective of a connected HVDC station allows adjustment of converter control parameters orto select the converter’s operational control mode. The short circuit capacity can be calculated byestimation of the grid’s impedance and its equivalent voltage. This paper presents the operationaland practical challenges in real-time implementation of the grid estimation algorithms especiallyfor HVDC applications. This paper shows that the Recursive Least Square (RLS) algorithm can bevery efficiently used for the real-time estimation of SCC. This technique forms a regression prob-lem using algebraic complex equations with an objective to minimize the error between estimatedand measured parameters. The algorithm has been reformulated and simplified to make it non-complex without the use of matrices, in order to facilitate further implementation on an industrialreal-time controller. The performance of the real-time implementation has been evaluated usinga HIL platform. A sensitivity analysis has been also carriedout to study the impact of differentparameters and operational conditions on the performance of the estimation algorithm. Finally, theactual application of real-time SCC estimation for the HVDCsystems has been demonstrated.