What is the difference between an AC Source and an AC Grid Emulator?
2021-11-22 | 7 min read
Over 20 years ago, I was hired at Keysight (Agilent at the time) directly out of college to work on our AC Source line of products, so this is a topic near and dear to me. Through the years, we have expanded what we offer in this area to some new and exciting places. We have been working closely with customers in the automotive and PV inverter application areas in recent years and one of the biggest needs where we saw where we could add value was with a high power, bidirectional AC Grid Emulator. Using the AC Grid Emulator along with our DC Power Supplies allows our customers to use Keysight products on both sides of their devices for a more complete testing solution.
The first thing I want to discuss is the difference between an AC Source and an AC Grid Emulator since both are used to power devices that run on AC power. An AC Source such as the Keysight 6812C does exactly what is implied in the name, it sources power. In other words, it supplies power out of its terminals into the DUT (see Figure 1). You cannot under any circumstances source power out of the DUT into the AC Source. I have seen this happen and it will most likely result in a damaged output stage in the AC Source.
Basically, an AC Source can operate in quadrants I and III of the traditional IV graph (see Figure 2). It cannot sink power, so the voltage and the current must be of the same sign.
The biggest difference between a Grid Emulator and an AC Source is that a Grid Emulator works in all four quadrants so it can both source and sink power (when sinking, the voltage and current will have opposite signs). This is how the actual AC power grid works, a device such as a solar inverter can put power back onto the grid. To test these sorts of devices, you need to a way to simulate the grid so that you can test abnormal situation under a controlled environment. The new Keysight Grid Emulator allows you to simulate these abnormal conditions as well as provides integrated safety features to keep DUTs and most importantly, users as safe as possible.
If you are interested in AC sources, Keysight offers a few different product families.
- Single Phase (0 to 310 Vrms)
- Basic AC Source
- DC Output
- Single Phase (0 to 300 Vrms)
- High Performance AC Source
- DC Output
- Digitized Measurements
- Transient Waveforms
- Three phase (0 to 320 Vrms)
- Harmonic analysis
- Waveform generation
- DC Output
For grid simulators Keysight offers:
There are 5 models in the SL1200 family.
Key features of the SL1200A:
- Can be used as either single phase, split phase or three phase
- Can be paralleled for up to 810 kVA of power
- Full 4 quadrant operation in AC and DC modes
- Integrated safety mechanisms with emergency stop
- Transient generation
- Integrated measurement system with power analysis
- Optional DC output
- Regenerates unused power and is more energy efficient
There are also three software packages available:
As you can see from the photos above, the SL200A is a fully-integrated racked system. There is not a physical front panel for control. This soft front panel software replaces the traditional front panel and allows full control of the system. This software allows for output control (voltage, current, frequency, phase angle, etc.), output measurement, and measurement logging. Also included in the SFP is a configuration and a firmware update utility for the system
The Keysight SL1220A software is a package for the Keysight Pathwave Test Automation software. This package contains a set of test steps and an instrument driver for the AC Emulator in the Test Automation software. There are various configurable pre-programmed test steps that: control the output, measure the output, and create AC and DC transients. I will be doing a few forthcoming blog posts that explore this software package in the coming weeks. This software require a license for both the KS8400 and the SL1220A.
This software package is designed to use the AC Emulator with the Keysight SL1040A Series Scienlab Charging Discovery System for testing AC and DC charging interfaces of electric vehicles.
As you can see there is a lot going on here at Keysight in the world of AC Power! There will be some blog posts coming up showing off the various software packages and some tips on how to use them better. Thanks!
Please visit Keysight’s Energy Ecosystem solutions to explore other related solutions.