AMETEK's TerraSAS Solar Array Simulator enhances PV inverter and micro-inverter testing

The Elgar brand of TerraSAS Solar Ar-ray 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?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.

"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, Ametek product manager for TerraSAS.

"The TerraSAS delivers an order of magnitude improvement in this critical response over conventional switch mode DC power sources," notes Turner.

The modular, rack-mounted Elgar TerraSAS system offers the following:
??One or more programmable DC power supplies with optimised, 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.
??A laptop with in-built simulation software, user-friendly keyboard and Graphical User Interface (GUI) display.

Testing for Grid-tied Solar System Inverters

Inverters designed for grid-tied solar systems must be tested for conformance with a range of conditions. Residential and commercial solar energy systems are rapidly emerging as a "green" alternative to utility supplied power. Grid-tied solar systems provide the user with the means to actually sell power back to the utility.

The inverters in this application must be designed to accommodate a wide variation in the availability and quality of power from the solar panels; a wide variation in the size and characteristics of the load being supplied; and variations in the inter-connected "public power" source.

Ametek MX Series

A programmable bidirectional AC power source/sink can be used to simulate the interconnection of the inverter with the grid. This equipment can simulate utility power variability (voltage, frequency, harmonic distortion) necessary to test the inverter's ability to source energy to the grid. In addition, the unit with the SNK Option can dynamically test the inverter's ability to comply with the anti-islanding tests required of grid-tied distributed resources.

This requires the power source to disconnect itself from the inverter and load while the load is perfectly balanced, as evidenced by no current flow to the source.

In short, Ametek provides complete solution for PV Inverter testing by:
??Simulating the solar arrays to confirm the inverter's capabilities to determine and operate at the maximum power point (MPP),
??Simulating the variability of the load to confirm the inverter's ability to handle load changes, transients, power factors and other characteristics, and
??Simulating the interface to the grid to confirm the inverter's ability to work harmoniously and safely with the power grid under normal conditions as well as when presented with anomalous situations such as power interrupts and brownouts.

(Electronic Enterprises (I) Pvt Ltd is the authorised distributor in India for Ametek Programmable Power, USA. Contact: Tel: 040-23243352, 23237214. Email: eehyd@eeipl.in, sales@eeipl.in)