AC-DC · Three-Phase PFC · Virtual Lab

Vienna Rectifier Simulator

An advanced, physics-accurate simulator of the Vienna rectifier — a three-phase, three-level, unity-power-factor boost rectifier. It draws sinusoidal input currents in phase with the voltages and regulates a split DC bus with almost no low-frequency ripple. Watch every waveform on a real-time oscilloscope: the three input voltages, the three sinusoidal line currents, the three-level converter phase voltage (+Vo/2, 0, −Vo/2), the constant instantaneous input power and the flat DC bus — with live power factor, %THD and the boost ratio, and a proof that balanced three-phase power carries no 100/120 Hz ripple.

Vienna rectifier circuit diagram: three-phase input with boost inductors, three bidirectional switch legs to the neutral point of a split DC bus (two series capacitors) and rectifier diodes, giving sinusoidal input currents at unity power factor and three-level phase voltages
Vienna rectifier — a three-phase, three-level unity-power-factor boost rectifier. Boost inductors and three bidirectional switches to the split-bus mid-point give sinusoidal input currents and low THD.

Parameters

V
Per-phase RMS. Peak Vm = √2·Vs; line-to-line peak = √3·Vm.
Must exceed the line-to-line peak √3·Vm (boost rectifier).

Power stage

Higher fsw ⇒ smaller current ripple & filter.

Display

Presets

Waveforms to display

Waveforms Vo = 700 V · 5 kW

LIVE

Power factor & three-phase advantage (topic-specific)

The Vienna rectifier is a three-level converter: each phase terminal can sit at the positive rail, the neutral mid-point or the negative rail, so the converter phase voltage has three levels (+Vo/2, 0, −Vo/2). The small steps give low current ripple and very low THD from just three controlled switches. And because balanced three-phase power is constant in time, there is no 100/120 Hz output ripple — a big advantage over single-phase PFCs.

Line-current harmonic spectrum

Line-current THD—
Multiples of the line frequency. A three-level boost rectifier keeps every harmonic small (bar 1 = fundamental).

Measurements

Live accuracy check — simulation vs closed-form theory

What is a Vienna rectifier?

The Vienna rectifier is a three-phase, three-level, unity-power-factor boost rectifier. Each phase has a boost inductor and a bidirectional switch tied to the mid-point (neutral) of a split DC bus (two series capacitors), together with rectifier diodes. With only three controlled switches it shapes sinusoidal input currents in phase with the voltages and produces a regulated DC output with very low harmonic distortion — the classic front end for high-power three-phase supplies.

Three-level operation

Because each phase terminal can be connected to the positive rail, the neutral mid-point, or the negative rail, the converter phase voltage takes three levels: +Vo/2, 0, −Vo/2. The smaller voltage steps (half those of a two-level converter) produce much smaller inductor-current ripple and lower THD, so the input filter can be smaller and the switches see only half the DC-bus voltage.

Unity power factor and boost operation

ik(t) = Im·sin(ωt − k·120°) in phase with vk , Vo > √3·Vm (line-to-line peak)

The current controller forces each line current to be a sinusoid in phase with its phase voltage, so the power factor is close to 1 and the THD is very low. As a boost rectifier the DC bus must sit above the line-to-line peak √3·Vm (about 560 V for a 400 V line, so a 700–800 V bus is typical).

No low-frequency ripple — the three-phase advantage

For a balanced three-phase set the instantaneous input power is constant:

p(t) = va·ia + vb·ib + vc·ic = (3/2)·Vm·Im = Po = constant

So, unlike the single-phase boost PFC, there is no 100/120 Hz output ripple — only high-frequency switching ripple. The simulator verifies that p(t) is flat in real time.

Applications

Telecom and data-centre rectifiers, EV fast chargers, wind-turbine and aircraft converters — anywhere high power, unity power factor and low THD are needed. Compare the two-level PWM / active-front-end rectifier and the single-phase boost PFC.

Frequently asked questions

What is a Vienna rectifier?

A three-phase, three-level, unity-power-factor boost rectifier that draws sinusoidal input currents with only three controlled switches and produces a regulated DC output with low THD.

Why is it called three-level?

Each phase terminal can connect to the positive rail, the neutral mid-point or the negative rail, so the converter phase voltage takes three levels (+Vo/2, 0, −Vo/2), giving small steps and low harmonics.

Does it have twice-line-frequency output ripple?

No. Balanced three-phase input power is constant, so there is no 100/120 Hz output ripple — only high-frequency switching ripple.

How high must the DC bus be?

Above the line-to-line peak √3·Vm. For a 400 V line that is about 560 V, so a 700–800 V bus is typical.

Power4All · Vienna Rectifier interactive simulator. All waveforms are produced by numerical synthesis of the actual converter and validated against closed-form theory.