Available from Westek Electronics , the new California Instruments brand MX series AC DC power supply is now available with an electronic load option (SNK) permitting the reduction of the energy consumed in the production testing of grid-tied inverters designed for distributed resources such as solar energy systems.
By using the MX Series AC DC power supply to simulate the interconnection with the utility grid, the output power generated by the inverter is returned to the grid saving more than 50% of the energy consumption. The MX Series programmable source may be programmed to replicate utility power variability (voltage, frequency, harmonic distortion) necessary to test the inverter’s ability to source energy to the grid. Additionally, the test equipment can dynamically test the inverter’s ability to comply with the anti-islanding tests required of grid-tied distributed resources. Islanding is the term used to describe the unsafe operation of a distributed resource in the event of a loss of utility power.
The California Instruments MX Series electrical test equipment is available in power levels from 15 kVA to 270 kVA. The MX Series electrical testers use a digital signal processor-based arbitrary waveform generator and power analyser. Advanced measurement and analysis capabilities can be accessed directly from the front panel without the need for remote control. IEEE-488, RS-232C, USB and Ethernet interfaces are included and Windows Graphical User Interface application software comes with each MX unit.
MX operation with the Regenerate State ON supports the “balanced mode” anti-islanding test required by IEEE 1547 and other standards such as UL 1741and CA Rule 21. To balance the inverter output and load demand, the load is set to exactly absorb the output power of the inverter so that zero current flows. In Regenerative Mode, the MX with SNK option’s output relay can be opened while the voltage is at the programmed level, instead of requiring output voltage to be programmed “zero” before opening the output relay, which is the case with¬out the SNK option. This difference allows the testing of the inverter’s ability to detect that the “public supply” has been dis¬connected, a situation that can occur when the circuit breaker in the house trips or during a power outage. IEEE 1547 also requires the power source to disconnect itself from the inverter and load while the load is perfectly balanced.