What is a bidirectional (regenerative) power supply?

A bidirectional power supply is a programmable source that can both deliver power to the DUT and absorb power from it, returning that energy to the DC link or the AC grid (instead of wasting it as heat). In day-to-day language you’ll hear both “bidirectional DC source & sink” and “regenerative DC power supply.” Typical use cases include a battery emulator power supply for pack/BCU testing, EV subsystem validation, power-hardware-in-the-loop (PHIL), and energy-recycling battery aging/formation lines.

Topologies: AC↔DC vs DC↔DC (when to use each)

AC↔DC regenerative power supply (3-phase)

Choose this when your bench connects to facility power and you need energy fed back to the grid. TPS modules support 3-phase 380/400/415/480 VAC input, generate a stable HV DC bus (e.g., 570–900 V), and return energy with PF ≈ 0.99 and THDi < 5%. Typical builds use CAN/RS485 control and cabinet expansion for higher power. See AC-DC Bidirectional Power Modules.

DC↔DC bidirectional converter (isolated buck-boost)

Pick this when the DUT is a battery or LV DC rail and you already have an HV bus (from an AC front-end or DC source). DC-DC is ideal for battery emulator power supply needs: e.g., HV bus 700–800 V ↔ LV 14–16 V at hundreds of amps (both directions). See DC-DC Bidirectional Modules.

Voltage Families & Inputs: 570–900 V & 3-phase 380/400/415/480 VAC

Instead of fragmenting content by SKU, this guide treats voltages as families you can pick by use case. Your AC↔DC stage can form a HV DC bus at 570/610/630/700/750/800/900 V; your DC↔DC stage then maps that to LV lines (e.g., 14–16 V) with high bidirectional currents.

Sizing & Selection Flow (source/sink)

Use this quick flow to size any programmable bidirectional power supply—AC↔DC, DC↔DC, or a stack. The same logic works whether you target 570 V, 750 V or 900 V buses.

Example — EV pack on a 750 V bus

Continuous 60 kW, peaks 90 kW/3 s. Size the AC↔DC stage for the grid (PF≈0.99, THDi<5%), then add a DC↔DC stage for the LV pack rail (e.g., 14–16 V at hundreds of amps). If you use 570 V or 800–900 V, the math is identical—swap the DC-bus value and recompute current.

Safety fundamentals: insulation, leakage, creepage & clearance

• Creepage & clearance: establish tables for your chosen HV bus (570–900 V). Maintain spacing around terminations, shunts, and contactors; watch contamination and altitude multipliers.
• Leakage current: plan touch-safe design and bonding strategy; specify PE conductors and shield policy; document measurements.
• Isolation & discharge: confirm transformer isolation for DC↔DC; provide bleed/discharge paths and E-stop behavior (safe ramps, clamps, contactor logic).
• Wiring & interlocks: use 3Ph+PE for AC inputs; add door interlocks, over-temp and over-current cutoffs, and command limit checks in CAN/RS485.

EMC & Safety Test Checklist (pre-compliance)

Running a quick pre-compliance pass saves time and makes the formal lab visit predictable. Use the list below for both AC↔DC and DC↔DC projects.

Common Pitfalls & Quick Fixes

• Undersizing sink peaks. A DUT that regenerates briefly can exceed your sink spec. Add headroom or parallel a cabinet; verify recovery time and thermal margins.
• Ignoring grid quality. If THDi exceeds limits, you’ll see nuisance trips and failed audits. Use the PF/THDi claims as design targets and check feeders/breakers early.
• Noisy cabling & shields. Separate noisy and sensitive runs; keep loops small; set a consistent shield-bond policy to avoid common-mode issues.
• Controller surprises. Validate CAN/RS485 ramp rates, limits, and fault responses. Add a safe “command clamp” in software.
• Skipping pre-compliance. Do the LISN sweep and core immunity spot checks before you pay for a full day at the lab.

Tools, Downloads & Next Steps

• AC↔DC bidirectional power modules (grid-tied, regenerative)
• DC↔DC bidirectional modules (battery emulator, pack cycling)
• All bidirectional supplies (overview)

Request a Quote / Book Pre-Compliance Explore All Bidirectional Options

FAQ

What is a bidirectional power supply?

An instrument that can both source and sink power. In sink mode it returns energy to the DC link or grid (regenerative), cutting heat and operating costs. It’s ideal for battery emulation, EV subsystem tests, and energy-recycling lines.

Bidirectional vs four-quadrant supply — what’s the difference?

Both can source/sink. “Four-quadrant” is a control term describing voltage and current polarity in all four quadrants; many modern bidirectional supplies are effectively four-quadrant in their operating region. In practice, compare transient control, safe ramps, and power limits rather than labels.

Do I need UL or ETL for US buyers?

Both are nationally recognized marks. What matters is the scope (the standards and installation notes covered) and consistent labeling. Many buyers accept either UL or ETL when documentation is complete; speak with your AHJ/inspector early.

How do I size a bidirectional DC-DC for battery cycling?

Start from the battery voltage and current profile (continuous, peaks, duty cycle). Add headroom for regeneration and recovery. Verify cooling and conductor sizes, then set controller ramps/limits to avoid overshoot.

Can a bidirectional supply feed energy back to the grid?

Yes—use a regenerative AC↔DC stage designed for grid tie (PF≈0.99, THDi<5%). For pure DC benches, return energy to the common DC link instead.

What control interfaces are typical?

Industrial systems commonly use CAN or RS485 with defined commands, plus analog/digital I/O for interlocks. Always validate ramp rates, limits, and fault behavior before connecting the DUT.