Vienna rectifier

The Vienna Rectifier is a pulse-width modulation rectifier, invented in 1993 by Johann W. Kolar at TU Wien, a public research university in Vienna, Austria.

It can be seen as a three-phase diode bridge with an integrated boost converter.

[9] The Vienna Rectifier is useful wherever six-switch converters are used for achieving sinusoidal mains current and controlled output voltage, when no energy feedback from the load into the mains is available.

In practice, use of the Vienna Rectifier is advantageous when space is at a sufficient premium to justify the additional hardware cost.

These include: Figure 2 shows the top and bottom views of an air-cooled 10 kW-Vienna Rectifier (400 kHz PWM), with sinusoidal input current s and controlled output voltage.

Dimensions are 250mm x 120mm x 40mm, resulting in a power density of 8.5 kW/dm3.

The total weight of the converter is 2.1 kg [10] Figure 3 shows the system behaviour, calculated using the power-electronics circuit simulator.

[11] Between the output voltage midpoint (0) and the mains midpoint (M) the common mode voltage u0M appears, as is characteristic in three-phase converter systems.

It is possible to separately control the input current shape in each branch of the diode bridge by inserting a bidirectional switch into the node, as shown in Figure 3.

When the bi-directional switch is turned on, the input voltage is applied across the inductor and the current in the inductor rises linearly.

Turning off the switch causes the voltage across the inductor to reverse and the current to flow through the freewheeling diodes Da+ and Da-, decreasing linearly.

By controlling the switch on-time, the topology is able to control the current in phase with the mains voltage, presenting a resistive load behavior (Power-factor correction capability).

To generate a sinusoidal power input which is in phase with the voltage

the average voltage space vector over a pulse-period must satisfy:

For high switching frequencies or low inductivities we require (

) the phase of the input current space vector is

Fig. 1: Schematic of a Vienna Rectifier.
Fig. 2: Top and bottom views of an air-cooled 10kW-Vienna Rectifier (400kHz PWM).
Fig 3:Time variation of voltage-phases ua, ub, uc of the current-phases ia, ib, ic. From top to bottom: 1) mains voltages ua, ub, uc. 2) mains currents ia, ib, ic. 3) rectifier voltage at uDaM (see Fig. 1), which forms the input current. 4. Midpoint current of the output capacitors (i0 in Fig. 1). 5. Voltage between mains midpoint M and the output voltage midpoint 0. Note: Inner mains inductance is not considered, and therefore the voltage across the filter capacitors is equal to the mains voltage.
Fig 5: Conduction states of the Vienna Rectifier, for ia>0, ib,ic<0, valid in a sector of the period T1 sa, sb, and sc characterise the switching state of the system. The arrows represent the physical direction and value of the current midpoint i0.