As electric vehicles have become more advanced in recent years, the need for accurate test equipment has drastically increased. Legislative and social pressures demand an end to petrol and diesel market dominance, ensuring that an LCV’s electrical components and subsystems can perform over thousands of hours has become crucial.

The increasing complexity of modern LCVs also means that test laboratories need to be able to perform more functions than ever before. Systems must be able to run automated tests under a variety of user behaviour profiles, to identify weaknesses or potential improvements. Test set-ups must also be able to quickly respond to the changing dynamics of electrical components to achieve accurate results.

In response to this, the G5-RSS range of bidirectional DC power systems was launched. Over 40 years of development time have been invested to ensure the G5-RSS meets the foreseeable needs of research organisations, focussed on developing the next generation of LCVs. It builds on the solid bedrock of the widely adopted LAB-GSS modular system, which was first used commercially in 2011.

The G5-RSS utilises silicon carbide for its semiconductor elements. The primary PFC section and internal control loop operate at 48kHz. The DC/DC section operates at 96kHz and incorporates an interleaved buck converter that operates at 192kHz. This ensures an ultra-fast controller which provides highly dynamic and stable operation.

A current step between 90% sourcing to 90% sinking current can be as quick as 50us, enabling high speed drives to be supplied. An API is provided with the hardware allowing the user to program industry standard drive cycles and battery testing cycles via LabVIEW, Python or an alternative superposed control system.

With two current ranges for high accuracy, the G5-RSS is ideal for cycling energy storage devices. The unit’s ultra-fast dynamics with switchable capacitance also allows accurate simulation of batteries and capacitors. Battery simulation software is available to simplify and automate testing. Relevant electrical characteristics are programmable including: number of cells, energy capacity, cut off limits, chemistry type and nominal voltage.

Another emerging area of research where the G5-RSS excels is in emulating a high frequency ripple over a DC battery link. By utilising the unit’s optional embedded function generator, users can set a current ripple at up to 10kHz. The magnitude can be up to 5% of the nominal system current. Depending on the impedance of the device under test the resulting voltage ripple can be calculated.

The programmable ripple simulates a potential side effect of electrical noise, which can occur in circuits which contain both AC and DC components. The ripple causes unwanted fluctuations in battery temperature which results in deterioration of the battery’s performance.

An intuitive operating GUI is provided with each module to simplify set-up for users. An embedded scope function allows users to visualise and record live test data. The software also provides a variety of programming features and second level parameters, ideal for optimising test processes. Advanced users have access to the controller settings enabling the response to be optimised for particular loads.

A host of other control methods are possible including a touchscreen front panel, an analogue interface and various remote control interfaces. CANmp is particularly popular. Based on CAN 2.0, it gives the user the capability to customise the CAN protocol. Up to 100 messages are user configurable. This is ideal for fitting in with 3rd party proprietary CAN systems. Messages can be sent cyclically or upon receipt of a sync or syncID signal.

Each G5-RSS module features inbuilt system comms, allowing users to switch between series, parallel or matrix master/slave configurations. Systems can be reconfigured, expanded or broken up as needs dictate. The modular approach is useful for test houses and research labs who regularly test different sized power devices.

Individual G5-RSS modules are available with nominals from 9kW to 54kW, at 60V to 1500V. Up to 60 modules can be arranged in a variety of configurations. Outputs up to 3000V are possible into the megawatt range. Unusually, units can be connected in master/slave with different nominal power values. For example, a 36kW/500V module will connect in parallel with a 54kW/500V unit to provide 90kW/500V. Multi-module systems based around a mid-point earth are also possible, creating a +/- voltage output.

Research into electric transport is not just strictly limited to the automotive sector. One such landmark installation was a 2MW/3000V G5-RSS system to the Powered Electronics Machine Centre at the University of Nottingham. The new purpose built facility will offer testing services for both custom and mass market components for electric aircrafts.

While most pure electric road vehicle energy storage systems sit around the 1000V mark or below, research into electric aircrafts typically takes place at higher voltages. This is because higher voltages mean that the circuit will produce less current and therefore less losses to heat. This means smaller components and cables. Ideal where space and weight is at a premium.

The propulsion system of electric aircrafts are often made up of similar components to road vehicles. Such as electric drives, batteries and fuel cells. However, the industry has many different design considerations which need investigating, due to the high altitude these components must operate at. One challenge is that air is less dense, meaning that it’s harder to remove any dissipated heat. Flashovers are also more likely, which designs must guard against.

Besides bidirectional systems the ETPS product range includes new and rental DC & AC sources, electronic loads, four quadrant grid simulators and battery chargers/dischargers. Application specific equipment is also available for battery emulation, fuel cell simulation, battery cycling, V2G/V2H testing, electric drive testing, fuel cell loading, plus many more. Power systems ruggedised against shock, vibration and humidity are also available.

ETPS will be on stand C3-529 in Hall 3.

For more information, visit www.etps.co.uk.