Accurate, Fast and Power Efficient PV Emulator Based on Hybrid Passive and Active Circuits

Abstract

A photovoltaic emulator (PVE) has been proposed based on a physical equivalent photovoltaic cell model. It has fast dynamic performance that is compatible with a real PV system. The PV emulator can analyze and assess PV systems, including maximum power point tracking (MPPT). It is power efficient at the maximum power point. However, it has higher power loss at an open-circuit voltage (OCV). This paper, therefore, presents a hybrid solution using a switching circuit (SC) paralleled with the diode string (DS) to minimize the power loss. The SC consists of a two-switch non-inverting buck-boost dc/dc converter. The DS operates with a low power loss region, i.e., the current source region (CSR) of the I-V curve, in which the SC switches in to replace the DS in the voltage source region (VSR) to minimize power loss of the DS while maintaining the emulator's circuit operation. The SC handles only a fraction of the rated emulator power and has a much narrower control bandwidth than a pure switching converter-based solution. Experimental results show that in the worst-case scenario, i.e., OCV condition, the efficiency and temperature of the PVE based on DS alone configuration reach 2.8% and 94.2 °C, respectively, as compared to 85.98% and 26.5 °C for the proposed hybrid solution. Under the 30% to 60% insolation change test, the suggested PV emulator lags the actual PV panel by only 3.2 ms, compared to 120 ms lagging for a commercial emulator. Furthermore, the control strategy is implemented to handle the trade-off between thermal and dynamic performances of the proposed solution.