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This study presents a simple and efficient approach for grid voltage estimation based on the converter equations in the stationary reference frame. The proposed technique is adopted for the sensorless operation of the voltage source converter-based power conditioners. In this study, the effectiveness of the proposed estimation method when it is combined with a proportional-resonant (PR)-based current controller is investigated. When the PR controller is combined with the proposed voltage estimation technique, it offers an additional benefit, such that the grid voltage synchronisation is done without using any phase-locked loop or band-pass filter. The proposed sensorless control method shows an excellent steady-state and transient performance. It is proven through extensive simulations and experiments that the grid voltage estimation with a very low computational burden is achieved even when the grid voltage is distorted.

This study presents a proportional resonant current control scheme for three-phase grid connected voltage source converters without any grid voltage sensors. Towards this goal, the grid voltage sensors are replaced by a voltage estimation scheme based on the Newton-Raphson algorithm. In the proposed method, the grid connected converter behaviour is converted to an optimisation problem which relates the instantaneous grid voltage value to the filter parameters, the generated converter voltage and the exchanged powers in each sampling period. The proposed optimisation problem is then solved in each sampling period by means of the Newton-Raphson optimisation technique. Afterwards, the reference current for the current control loop is generated from the estimated grid voltages. Using an estimator instead of the voltage sensors not only reduces the size and cost of the converter system but also improves its reliability and protects it from grid voltage disturbances and noises. The excellent performance of the proposed grid voltage sensorless scheme is confirmed through experimental and simulation results.

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