Solar array simulator enhances inverter testing

The Elgar brand TerraSAS Solar Array Simulator from Ametek Programmable Power offers a fully integrated solution for the design, development and production testing of inverters and micro-inverters for domestic and industrial solar energy systems. The TerraSAS simulates photovoltaic (PV) dynamic solar irradiance and temperature characteristics over a range of weather conditions from clear to cloudy and over a specified time interval to produce the current/voltage (IV) characteristics for the specified PV array for those conditions. For ease of use, the system’s simulation engine is able to download data from the National Renewable Energy Laboratory (NREL) Solar Advisor Model database defining key parameters – open circuit voltage (Voc), short circuit current (Isc) and maximum power point voltage (Vmpp) at 25 degrees C and 1000 W/m² irradiance – so that the IV curve can be calculated according to a standard solar cell model for virtually any fill factor or solar material. Other PV panel IV curves can be entered manually. Systems with multiple panels with different characteristics resulting in “multiple hump” IV curves also can be simulated. In addition, the simulator is capable of simultaneously simulating up to 24 parallel channels for use with micro-inverters. “An essential part of this testing is to provide the inverter under test with accurate simulation of the PV array response to its maximum power point tracking (MPP) function. To perform this task, the power source must accurately process the PV array’s IV curve without filtering the low frequency ripple voltage produced by the inverter to track MPP,” comments Eric Turner, product manager for TerraSAS. “The TerraSAS delivers an order of magnitude improvement in this critical response over conventional switch mode DC power sources. The application of high-speed switching power supplies and advanced DSP signal processing allows us to attain superior MPP tracking response without the need for bulky and expensive linear power supplies,“ notes Turner. The modular, rack-mounted system offers one or more programmable DC power supplies with optimized, high-speed output response available in 1 to 15 kW increments, a controller module and simulation engine for implementing the sequencing of the PV panel(s) IV curves, power supplies that can be configured master/auxiliary to provide high power systems, user friendly key board and Graphical User Interface (GUI) display and relays for output isolation and polarity reversing.