G5-RSS modules can be arranged in series, parallel or matrix array configurations up to 6MW. Each module is able to operate independently, so that systems can be reconfigured, expanded or broken up as needs dictate. Inbuilt system comms allow users to switch between various set-ups. It is possible to connect models with different nominal powers in an asymmetric parallel or series configuration, as long as each module has the same nominal voltage. For example, an 18kW/500V/±108A and 54kW/500V/±324A module can be connected together to in parallel to create a 72kW/500V/±432A system.

The modular approach is useful for test houses and research labs who regularly test different sized power devices. Individual modules can be used for the day to day testing of multiple small devices, then grouped together for larger projects. The diagram below shows all the possible combinations with eight 54kW/1500V modules.

Fast Dynamics and High Stability

A current step between 90% sourcing to 90% sinking current can be as quick as 50µs, enabling high speed drives to be supplied. Advanced users have access to the controller settings enabling the response to be optimised for particular loads. The example shows a current step through quadrants.

The upper trace shows the current transition is achieved in 50µs with a small overshoot before settling. The lower plot shows a more regulated response within 200µs. Voltage typically takes 100µs to recover within 0.5% of the set value.

Switchable Output Capacitance

Switchable capacitance is provided within each G5-RSS module as standard and is used to optimise the DC filter depending on the application in which the systems are used. A low capacitance level provides fast dynamics in constant current when charging/ discharging/ cycling energy storage devices. Switching to the higher cap value provides for smoother operation during hard load steps when operating in constant voltage. Typical applications include energy storage simulation for electric drive developments.

Second Current Range

Each module features a second current range that can be built into systems to give better accuracy and resolution for low current applications. This is particularly useful when testing high voltage equipment, such as electric vehicle battery packs, which typically produce low currents.

Programmable Ripple

By utilising the optional embedded function generator the user 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 DUT the resulting voltage ripple can be calculated. The below example shows a 10kHz ripple generated using the function generator of the G5-RSS. A peak to peak current of 8A has been superimposed on a current of 100A. Alternatively, a ripple can be implemented from an external waveform generator via the analogue interface using a proportional 0-10V signal.

Sense Compensation

Sense plus terminals are built into the G5-RSS for the connection of sense wire which compensates for voltage drops in the load lines. This has a number of advantages over traditional sense. It is permitted to interrupt the load line during operation (voltage on). The maximum voltage drop compensation is adjustable. The voltage difference between G5-RSS output and sensing point is monitored. If a set limit is exceeded, the G5-RSS unit shuts off. This is particularly useful for applications with long cables often prone to unwanted voltage drops. 

Power Recycling

When sinking energy from the unit under test the G5-RSS automatically inverts the DC to AC and synchronises this output to the grid. This differs from conventional electronic loads which traditionally waste 100% of electrical energy that could be reused, by simply dissipating it as heat. By using this approach users can save significant electricity costs. Energy waste and thermal issues associated with traditional heat dissipative loads are also eliminated.

Autoranging Capability

Every G5-RSS features an autoranging output. This allows many more voltage/current combinations at nominal power than a traditional bidirectional DC power system. An example of the difference is shown below using a G5-RSS 54-500-324.

Using one autoranging bidirectional PSU instead of several traditional power systems saves both cost and bench space. Despite the units offering such a large output range, they are still incredibly power dense. 54kW of output power is provided from 10U of rackmounting height.

Every module features constant current, constant voltage, constant power as standard. Adjustable internal resistance is also provided.

Internal Resistance Range

Each module is built with a user programmable internal resistance range as standard. This makes the power supplies ideal for simulating the output of energy storage devices such as battery packs, fuel cell stacks and super capacitors. The exact range varies by module and can be viewed in the selection table.

Active Power Factor Correction

G5-RSS modules have Active Power Factor Correction (PFC) circuit integrated into the input stage as standard. This enhances the overall efficiency of the modules across the output power range when compared to a unit that does not have active PFC. In practice, this means a significant lower peak current value, a decrease of RMS value of the phase current and less perturbations of other equipment running on the same grid.

The inbuilt active PFC is also ideal for operating the power supply from a generator. Generators tend to be sensitive against high current peaks, and their voltage controllers may have some stability problems with non-sinusoidal load currents. The active PFC feature forms a lowpass filter and therefore, both the repetitive current peaks and also the harmonic content is enhanced. This will help the generator system maintain a stable and reliable output.

A variety of control methods are provided. As standard each module is built with isolated analogue, Ethernet and USB interfaces. A touchscreen HMI is optionally available for front panel control and display, as well as a CANmp high speed digital interface.

Standard Analogue Interface

An analogue interface is provided as standard which operates at 48kHz. The control port is configured as a Sub-D 25 female connector and is located on the rear panel. It allows output values to be set and read proportionally using a 0-10VDC analogue signal. Digital inputs and outputs enable various functions such as the interlock and output ON/OFF. A 10VDC reference is provided for analogue control. Digital functions are switched via a high/low signal. A 24VDC supply voltage is provided for these functions. 

Front Panel Indication

As standard the front panel has backlit indicators which illuminate to show which control mode the power system is operating in (CV, CC, CP, CR). When the G5-RSS has been successfully energised, the corresponding power light illuminates green to indicate this. An illumination is also provided to visually warn users of any status (yellow) or error (red) message.

Touchscreen HMI (Option /HMI)

The optional HMI provides a simple and intuitive way of control and measurement via a touchscreen panel. Users can directly access features such as the system's protections, warnings/errors and optional function generator without the use of a computer. A user defined passcode can be set to lock the touch screen, which prevents unauthorised access. When selected, the HMI replaces the front panel indicator.

CAN Multi-Purpose Interface (Option /CANMP)

CANmp is a high speed digital interface operating at 1kHz. The interface gives users the capability to customise the CAN protocol. Up to 50 messages are user configurable. Along with the CAN ID the data length code, byte order, start bit, data type and signal factor can be adjusted by the user. A DBC file is provided and messages can be easily configured within the standard windows software. Messages can be sent cyclically or upon receipt of a sync or syncID signal.

Standard G5.CONTROL GUI

All G5-RSS units come with a simple and intuitive G5.Control operating GUI as standard. Live values of the power system are displayed graphically along with any warning and error messages. The software provides a variety of second level parameters, ideal for users who like to optimise their test processes. In standard user mode the operator can remotely program set values, enable voltage output as well as the ability to analyse different variables including set and actual values via the integrated scope.

The scope function can simultaneously record up to 8 system variables. Recording can be started manually or by a defined trigger event from any variable of the system. All actual and set values (currents/voltages/power/internal resistance) can be recorded. Other recordable items include system temperatures, intermediate DC circuit, low voltage auxiliary power supplies, error related values and variables from the controller section. 

A password protected section is available to the advanced user and service technician. In addition to the standard functions the authorised user is able to:

• Program linear ramp functions at start up and set value steps during operation
• Configure multi-unit operation
• Program the PID controller parameters
• Program the unit's limit values
• Calibrate and adjust values as necessary
• Update the firmware

Function Generator (Options /TFE & /AAP)

Complex DC waveforms can be implemented through an optional embedded function generator. The highly programmable nature of the function generator allows users to plot out exact waveforms. This is often advantageous when emulating a power device with a very specific behaviour profile. For example, when quality testing fuel cell powered equipment, the specific behaviour of a discharging fuel cell can be programmed and replicated.

As well as custom shapes, standard square, sawtooth and sine waveforms can be plotted against time. Voltage/current and voltage/power relationships can also be programmed where necessary. Parametric programming is possible when 
selecting option /AAP, where instead of the time axis, an input variable (VIN, IIN or PIN) can be selected.

Soft Tools

An API for dotNET/C# programming is provided to simplify the integration into 3rd party control and measurements software platforms such as LabVIEW and Matlab. The API can be used to integrate into Python or remote systems based on the REST architecture.

Battery Simulation (Option /BatSim)

BatSim is a battery emulation GUI for use with G5-RSS power systems. The GUI allows the power supplies to simulate real world behaviour of a battery pack.

Emulating a battery pack allows specific sections of a circuit to be isolated and researched. Nearly all relevant electrical characteristics are programmable including number of cells, energy capacity, cut off limits, chemistry type and nominal voltage. The modularity of the power systems provides a convenient method to emulate different size battery stacks. Hard to replicate conditions, such as a cranking curve from a cold start can be programmed and repeated when used in conjunction with the function generator.

The multi-channel data logger provides live reporting and output to file (CSV) with timestamps. Previously recorded data can be imported, reviewed and compared in the analyser mode. Other features include:

• Adjustable internal resistance and discharge current
• Variation of exponential capacity and voltage levels
• Emulation of common battery chemistries
• Novel chemistries available on request
• Series/parallel configuration of cells

Electric Drive and Battery Cycling (Option /BATCONTROL)

Drive cycle tests can be implemented using BatControl. The GUI’s main screen provides an overview of the main test values for all BatControl operations. Live data from the connected power system is displayed, and setting/adjustment of primary values is possible. 

Previous data obtained from a test track can be imported and recreated, allowing the G5-RSS to simulate a real world driving test inside a lab environment. Battery and capacitor charge/discharge profiles can also be implemented through the GUI. An internal charge counter allows users to view live data for Wh and Ah. Energy storage orientated tests which users can program include: 

• Battery charge/discharge cycles
• Automated drive cycle loading and simulation
• Fuel cell loading
• Comparative studies
• Shot and burst overload tests
• System degradation tests
• Battery lifetime tests

Solar Array Simulation (Option /SASCONTROL)

SASControl software has all EN 50530 tests pre-installed, with minor adaptations possible for particular inverter models. The GUI allows users to edit irradiance, temperature, amplitude values or input scaling with special commands. 

Previous tests have been conducted using over 400,000 individual data points, with more possible. This allows users to simulate changing conditions over the course of day.

Integrated Safety Relay (Option /ISR)

For additional safety, a mechanical interlock is available for the mains input of the G5-RSS. The integrated safety relay provides shutdown safety according to EN 13849-1 category 2/3. The ISR is connected to the external safety switch loop. If the external loop is opened, the DC-output of the power system is powered down immediately.

Protection Against Contact (Option /PACOB)

A specially produced cover is optionally available which provides protection against accidental contact of AC terminal block (rated to IP20). A cover for the DC output bars in provided as standard.

Automatic Voltage Matching with RPP (Option /RPP)

When researching energy storage devices, Reverse Polarity Protection (RPP) is recommended for devices without an automatic voltage matching circuit. With the G5-RSS energised but output off, the RPP senses the voltage of the connected energy storage device. A contactor is closed after matching the voltage, to prevent large inrush currents and arcing on start up. The sense lines of the G5-RSS are used to measure the battery voltage. A switched sense is also provided ensuring there is quiescent current draw at voltage off state.

Input Air Filter (Option /FILTER)

The G5-RSS modules are designed to be operated within a clean laboratory environment. If there is the possibly that the environment will be less clean, then the optional front panel frame and air filter arrangement offer some additional protection. The standard filter material is rated in class G3. This class is effective at trapping a high proportion (90%) of particles ≥10um according to EN 779. 

Air filters have proven beneficial in environments where there is the risk of some metal working potentially leading to swarf contamination. Please note that the units with or without air filters must not be operated in environments where fine conductive dust is present. 

Each G5-RSS is built into a 19" rackmounting case as standard. Units can be treated to a laboratory rack or flight case integration. Common options include mains cables, passive indication of any residual DC voltage, isolation monitoring of DC cables and a panel mounted emergency stop. Switch panels with removable DC links can be fitted for modular systems. This simplifies the reconfiguration between series, parallel or independent use. Simple wheeled cabinets are also available. 

Having a programmable power system mounted into a flight case on castors is often advantageous, especially when several departments or test cells share the same equipment. Multiple power systems can be fitted into the same flight case. Door hangers are fitted for convenience. Existing ETPS systems can also be retrospectively integrated into new flight cases where requested.

If your test requirement is short term, we have multiple G5-RSS modules in our rental range up to 216kW/2000V. High current models up to 2704A are also available.

The versatile programming capability of the G5-RSS ensures that it is popular across many research and development sectors. Common applications include battery/capacitor emulation, implementing drive cycles, fuel cell loading, testing flywheels, battery cycling, component lifetime testing, as well as the testing of inverters and DC-DC converters.

A 3000V/2MW G5-RSS was supplied to the University of Nottingham’s Electrification of Aerospace Propulsion Facility. The system caters for a wide range of electric aircraft developments. Testing electrical machines, motors, controllers and power sources - both individually and as a complete system

AC Ripple on Battery Link

A potential side effect of charger circuits that contain both AC and DC components is electrical noise. The ripple causes unwanted fluctuations in battery temperature, which results in deterioration of the battery’s performance. By utilising the G5-RSS's optional embedded function generator the user can set a current ripple at up to 10kHz to simulate this phenomenon. 

Cranking Curve Testing

Electrical components within a vehicle's subsystem must be able to withstand a wide range of input voltage surges and drops during a start-up. The G5-RSS can accurately recreate these conditions within a lab environment. This increases reproducibility and accuracy of results when compared to using real batteries. Hard to replicate conditions such as voltage cranking during a cold start can be achieved. Voltage/current and voltage/power relationships can be programmed against time where necessary. 

Pulsed Battery Charging

Pulse charging interrupts the traditional DC charging curve with short relaxation periods. The technique is thought to improve battery discharge capacity and help facilitate longer cycle life. Some studies have shown that pulse charging is also helpful in eliminating concentration polarisation. The G5-RSS's embedded function generator allows the PSU to deliver short burst of highly concentrated energy at user defined time intervals. The technique can also be used for powering lasers, electromagnets and plasma generation.

Voltage Drops & Interrupts

In electronic systems sudden voltage interruptions may cause unexpected behaviour. Supply line disturbances may have several causes, including an additional switch on of large capacitive loads parallel to the supply line or a short circuit caused by loads sharing the supply. The G5-RSS can generate many complex DC waveforms to test devices under realistic conditions to identify any potential issues. 

Inverter/Converter Testing

The DC input of virtually any power conversion device can be replicated. The influence that variables, such as line voltage variation, have on performance can be isolated and tested. This allows optimum operating conditions to be characterised to improve efficiency and performance.

Fuel Cell Emulation

The discharge behaviour of an FCEV's fuel cell is often irregular. By using the function generator, both conservative and aggressive driver profiles can be replicated. This allows the G5-RSS to perform effective quality testing of fuel cell powered components under all likely operating conditions.