As the number of electrical devices in everyday use around the world continues to grow, the importance of grid simulators for electrical product testing also grows. Because they can emulate the characteristics of electrical power grids at the touch of a button, grid simulators can provide electrical power in the many forms found on a grid and can subject an electrical device under test (DUT) to the variety of operating conditions that it must handle under real-world use. Choosing a grid simulator for an application is a matter of understanding available functions and key operating parameters, such as voltage, current, power, and output frequency.
Grid simulators supply AC and DC electrical power under the many conditions exhibited on an electrical power grid and can accurately measure bidirectional power from DUTs or loads capable of generating power. Regenerative grid simulators can return the generated power to the grid, or a facility using the grid simulator and are often characterized in terms of operating efficiency as a way of showing how much power they can return to the grid during testing. Many DUTs work with applied active electricity and produce reactive power in a bidirectional flow which is typically represented by a four-quadrant diagram to show the different states of electricity within the DUT. A regenerative grid simulator can manage fully four-quadrant electrical power while returning a high percentage of power to the grid for testing under “green” energy operating conditions.
Specifying a grid simulator involves reviewing electrical and mechanical parameters. Essential electrical parameters for power generation include AC voltage range, DC voltage range, AC and DC current ranges, frequency range, and maximum power. Operating configurations include single-phase, split-phase, and three-phase modes. Grid simulators may incorporate a waveform generator to produce harmonics and distortion which can be useful in emulating grid power conditions. Grid simulators also provide extensive measurement capabilities, such as for characterizing voltage, current, power, and frequency. In terms of mechanical specifications, the size and weight of a grid simulator is synonymous with its maximum power capabilities, with the highest-power grid simulators usually requiring a rack-mounted, floor-standing measurement system in which high efficiency relates to the system’s operating costs.
Gauging the Grid
Whether for lower-power testing or emulating DUT operating conditions at higher power levels, grid simulators typically integrate a host of safety features, such as thermal detection to guard against overheating and over-voltage protection to prevent equipment damage, to protect the equipment and its operators. A growing number of grid simulators are regenerative units with high efficiency and advanced electrical power control for sophisticated grid simulation. For example, the NH Research 9410-12 is a four-quadrant, regenerative grid simulator designed for grid-connected testing. It fits an enclosure measuring 15 × 19 × 24 in. (400 × 483 × 610 mm) and weighs 155 lbs. (70 kg). It offers three output ports for any combination of DC and single-, two, or three-phase AC power. The desktop unit provides as much as 12 kW true power or 31.5 kVA apparent power from a wide voltage range of 10 to 175 V with as much as 90 A RMS single-phase current. With a built-in 125 kSamples/s waveform digitizer, model 9410-12 can generate precisely controlled AC distortion and harmonics. The grid simulator includes measurement capabilities for voltage, current, power, and timing, and flexible control methods, such as via an integrated touch panel and a soft panel on a personal computer (PC) with the appropriate software.
In a similar-sized package—measuring 5.23 × 16.85 × 27.55 in. (132.8 × 428 × 700 mm) and weighing 99.21 lbs. (50 kg)--the Chroma 61815 regenerative grid simulator is capable of 15 kVA power in single-phase operation and 5 kVA per phase in three-phase mode. It can provide as much as 350 VLN line-neutral (LN) voltage and 606 VLL line-line (LL) voltage in a single-phase, three-wire output configuration. It is rated for as much as 105 A RMS current in single-phase use and 35 A/phase in three-phase use. Frequency can be set from 30 to 100 Hz with 0.01% accuracy. Based on fundamental frequencies of 50 or 60 Hz, harmonics as high as the fiftieth order can be generated. The grid simulator provides AC, DC, and AC + DC output modes for flexibility. For remote operation, it incorporates local area network (LAN) and Universal Serial Bus (USB) interfaces, with an option for a GPIB interface. For more power, as many as three units can be run in parallel.
In a larger enclosure, the Chroma 61860 regenerative grid simulator is rated for 60 kVA with an AC voltage range of 0 to 300 VAC at frequencies from 30 to 100 Hz. The four-quadrant, floor-standing programmable system is ideal for smart grid testing as such applications as vehicle-to-vehicle (V2V), vehicle-to-grid (V2G), and energy-storage-system (ESS) testing. It provides AC, DC, and AC + DC operation and features the programmability and speed needed for design as well as production grid simulation. Fast switching of output voltages is possible with several operating modes, such as step, pulse, and list modes, and a synthesis function enables generation of as high as fortieth-order harmonics. It includes GPIB, RS-232, USB, and Ethernet interfaces for remote control.
When much higher power is needed, the Chroma 61800-100 regenerative grid simulator is a four-quadrant, floor-standing, rack-mounted test system well suited for electrical compliance and safety testing on the production line. The high-power AC source is rated for 105 kVA single-phase power or 35 kVA per phase for each of three phases. It provides as much as 140 A/phase in three-phase mode and features voltage ranges of 0 to 300 VLN and 0 to 520 VLL.
For extremely high power levels, the NH Research 9510-100 regenerative grid simulator employs a modular system approach capable of 100 kW power per module and as much as 1.2 MW for a floor-standing system fully loaded with modules. The AC and DC grid simulator also functions as a four-quadrant AC load, with single-phase, split-phase, and three-phase operational capabilities. It achieves high efficiency, returning more than 85% of input power to the grid or operating facility.
Drawing upon advanced silicon-carbide (SiC) semiconductor switching technology, the California Instruments SQ0045 programmable regenerative grid simulator also is designed to recover more than 85% of applied power. Rated for 45 kVA or 45 kW output power in single-phase or three-phase modes, it provides single- or multiple-phase AC power and multiple-channel DC power. It offers a low AC voltage range of 0 to 166 VLN RMS and a high AC voltage range of 0 to 333 VLN RMS, with 5-in. color touchscreen display and standard RS-232C, USB, and LAN remote-control interfaces, with option for a GPIB interface. SQ0045 provides measurement capabilities for testing according to international standards like IEC 61727 and IEC 62116. It employs the SCPI command protocol for programming and features a grid simulator mode to emulate a variety of electric grid conditions, such as interconnecting with weak grids or strong grids.
These grid simulators offer a range of sizes, weights, and power ratings for a variety of applications. They feature the precision and accuracy needed for design through manufacturing testing of electric-grid-interactive DUTs. For more information on these, please visit our website or contact a Transcat | Axiom Rental Account Manager for guidance at (760) 806-6600.