Discrete-time interconnected observer for dc voltage estimations in multilevel STATCOM

This paper addresses the discrete-time interconnected observers that jointly estimate the DC voltage drops across each capacitor at the DC side of every H-bridge inverter connected together into a leg of multilevel STATCOM. The Heun's method is adopted in order to discretize their counterparts concerning continuous-time into such a discrete-time form. Beneath this manner the discrete-time observers are all introduced into one prediction and one correction stages for each iteration. Once their sampling period becomes very small, their stability condition is analogous to that of the continuous-time observers. Some simulations are carried out for the purpose of verification on performance in their estimations. In comparison with the actual voltages, the results of test confirm effectiveness of the discrete-time observers offered.