RAPID PROTOTYPING OF PHOTOVOLTAIC EMULATOR USING BUCK CONVERTER BASED ON FAST CONVERGENCE RESISTANCE FEEDBACK METHOD

Abstract

Using a PV emulator (PVE) simplifies testing of the Photovoltaic (PV) generation system. However, conventional controller used for the PVE suffers from oscillating output voltage, requiring a high number of iterations, or it is too complex to be implemented. This project proposes a controller based on a resistance feedback control strategy, which produces stable and fast converging operating point for the PVE. The resistance feedback control strategy requires a new type of PV model, which is the Current-Resistance (I-R) PV model. This model is computed using a Binary Search Method at a fast convergence rate. It is combined with a closed-loop buck converter using a PI controller to form the resistance feedback control strategy. The acquired experimental results show that the proposed PVE is able to follow Current-Voltage characteristic of PV module accurately. In addition, the PVE’s efficiency is more than 90% under maximum power point operation. The transient response of the proposed PVE is similar to the PV panel during irradiance changes.

Existing System

In the existing system, Direct Referencing Method is used.

Proposed System

The resistance feedback used in Resistance Comparison Method has the advantage of finding the load condition instantaneously. Nonetheless, this feedback cannot be used directly to obtain the operating point since the PV model used in the Resistance Comparison Method has either voltage or current as input. The Resistance Comparison Method needs to test various voltage or current inputs into the PV model before an operating point is obtained, resulting in a high number of iterations of the PV model. Introducing a PV model with resistance input would reduce the number of iterations for the PV model to only one, thus reducing the processing burden significantly. Despite all that, the PV model with resistance input is still unavailable. This project proposes a new control strategy for the PVE using the Current-Resistance PV model, in which the PV model has input resistance. This control strategy is called Resistance Feedback Method. The PV model being used is a single-diode model and it is based on an 80 W PV module. While the power converter used for the PVE is the buck converter with an output voltage and current rating of 45 V and 2.4 A, respectively. The closed-loop buck converter system is controlled using the controlled current-mode and PI controller. The simulation is conducted using MATLAB/Simulink.

Architecture

Circuit diagram for Control strategy of PVE based on the proposed Resistance Feedback Method