By:
Michael V. Binoj 23BEE0036
Tejsva Pandey 23BEE0011
Bharti Sharma 23BEE0079
LITERATURE REVIEW
The Vienna rectifier has garnered significant interest due to its advantageous
features in power conversion applications, particularly in the domains of electric
vehicle (EV) charging and renewable energy systems. This essay reviews the
existing literature on the design and control strategies for Vienna rectifiers,
emphasizing their operational principles, designs for specific applications, and
various control methodologies. The escalating demand for energy and the
proliferation of power electronic devices have brought power quality issues, such
as poor power factor and increased total harmonic distortion (THD), to the
forefront of electrical engineering concerns (Direct Power Control of Vienna
Rectifier Based on Fractional Order ..., 2024). Power factor correction (PFC) and
THD reduction are critical for enhancing energy efficiency and ensuring grid
stability, making them vital areas of research and development (Design PID
Controllers for Three-Phase Rectifier Using Closed ..., n.d.). This essay explores
the application of Proportional-Integral (PI) controllers in Vienna rectifiers for
achieving PFC and THD reduction, drawing upon recent literature to provide a
comprehensive overview of the field.
When designing power conversion systems, particularly in applications such
as electric vehicle chargers, renewable energy systems, and industrial
drives, selecting the right rectifier topology is critical. Compared to diode
rectifiers, thyristor-based rectifiers, and standard P W M rectifiers, the
Vienna rectifier offers superior stability, power factor correction ( PFC) , and
lower Total Harmonic Distortion (THD).
Stability Considerations:
Stability in Vienna Rectifier
Three-Level Control:
• Unlike traditional two-level rectifiers, the Vienna rectifier generates three voltage levels,
reducing the voltage stress on components.
• The neutral-point balancing in the DC-link capacitors enhances system stability by
preventing voltage drift.
Better Dynamic Response:
• The current control loop in a Vienna rectifier ensures that input currents remain
sinusoidal and adapt quickly to changes in load and input conditions.
• The voltage control loop stabilizes the D C - link voltage, preventing overvoltage or
undervoltage conditions.
Reduced Output Ripple:
• Since it is a multi-level converter, it generates a smoother DC output voltage with fewer
ripples compared to conventional two-level rectifiers.
• This results in less stress on downstream loads such as inverters or DC motors.
Stability in Other Three-Phase Rectifiers
Diode Bridge Rectifiers
• No active control over voltage or current, leading to poor dynamic
response and higher voltage fluctuations.
Thyristor-Based Rectifiers
• Susceptible to commutation failures, leading to potential
instability in high-power applications.
Two-Level P W M Rectifiers
• More voltage stress on switches due to the absence of a three-level
modulation, leading to greater switching losses and heating issues.
Why Vienna Rectifier?
Stable D C output due to three-level
operation
Superior dynamic response under
varying load conditions
Minimized voltage fluctuations due to
capacitor balancing
Power Factor Correction (PFC)
Power Factor in Vienna Rectifier
Near Unity Power Factor (~0.99)
• The Vienna rectifier actively controls input current, making it sinusoidal and in
phase with the input voltage.
• This ensures a high power factor, significantly improving the power transfer
efficiency from the grid.
PWM-Based Control for P F C
• Unlike passive rectifiers, the Pulse Width Modulation (PWM) control in Vienna
rectifiers dynamically adjusts current waveform, ensuring continuous power
factor correction under varying loads.
Reduced Reactive Power Consumption
• Since the input current is actively shaped, reactive power drawn from the grid is
minimized, reducing unnecessary burden on the power supply.
Power Factor in Other Rectifiers
Diode Bridge Rectifier:
• The input current waveform is highly distorted, leading to a power factor as
low as 0.6 - 0.7.
• Significant reactive power is drawn, leading to energy losses in the grid.
Thyristor-Based Rectifier:
• Power factor depends on the firing angle of thyristors, typically ranging from
0.5 to 0.9, but always lagging.
• Large inductors are required for PFC, making the system bulky.
Standard Two-Level P W M Rectifiers:
• Can achieve high power factor (~0.95), but not as efficiently as Vienna
rectifiers due to higher switching losses and voltage stress.
Why Vienna Rectifier?
Maintains near unity power factor without additional components
No need for bulky passive filters
Highly efficient P F C even under dynamic load conditions
Total Harmonic Distortion ( T H D )
T H D in Vienna Rectifier
Lo w T H D (~5%)
• The three-level switching significantly reduces voltage steps, leading to lower current
distortion.
• Since input current is actively controlled, harmonic content is minimized.
Less Need for External Filters
• Conventional rectifiers require large passive filters (inductors and capacitors) to suppress
harmonics.
• The Vienna rectifier achieves low THD through modulation techniques, eliminating the
need for bulky external filters.
Compliance with I E C 61000-3-2 & I E E E 519 Standards
• Vienna rectifiers meet stringent grid harmonic regulations, making them ideal for grid-
connected applications like E V chargers and renewable energy interfaces.
T H D in Other Rectifiers
Diode Bridge Rectifier:
• High T H D (~30% or more) due to sharp current spikes.
• Generates significant low-order harmonics, which can distort the grid voltage.
Thyristor-Based Rectifiers:
• Produces harmonics in the range of 20-50%, requiring complex filtering.
• Causes voltage notches that can disrupt sensitive equipment.
Two-Level P W M Rectifiers:
• THD is higher (~10-15%) due to higher voltage steps and switching frequency
limitations.
Why Vienna Rectifier?
Achieves very low T H D (~5%) without large passive filters
Reduces harmonic pollution in the grid
Ensures compliance with power quality standards
Circuit Configuration of Vienna Rectifier
The Vienna rectifier consists of the following key components:
(a) Diode Bridge (DB)
• Function: Converts the three-phase AC supply into a rectified DC voltage.
• Working: The diodes conduct based on the polarity of the input phase voltages,
allowing only positive voltage to pass through.
(b) Bidirectional Switches (IGBTs/MOSFETs)
• Function: These act as controlled switches that regulate the power flow, achieving
a three-level output voltage.
• Working: The IGBTs are switched at high frequencies using Pulse Width
Modulation (PWM) to generate a near-sinusoidal input current.
(c) D C - Link Capacitors (C1 & C2)
• Function: These capacitors split the DC bus into two equal voltage levels, forming
a neutral point that helps achieve a three-level output.
• Working: They stabilize the output voltage and help maintain a balanced DC-link.
(d) Inductors (L)
• Function: Reduce the ripple in input current and help in power factor correction.
• Working: The inductors store energy during switching transitions and release it
smoothly to maintain current continuity.
(e) Neutral-Point Balancing Circuit
• Function: Ensures the midpoint of the DC bus remains stable by balancing the
voltages across capacitors.
• Working: This circuit prevents voltage drift that could damage the power
electronics.
The main components in the Three-level Vienna rectifier
topology are three Boost inductors, three power bridge
arms, aFnd two DC side capacitors in series. Each power
bridge arm consists of two reverse series switches and a
power switch that allows two-way current flow.
We will take phase A as an example to analyze the current flow path under
different
current polarity.
(1) When ac A phase voltage and current are both positive:
When switch S1 and S2 are switched on, the current flow path is as follows:
Ea→L1→S1→S2 anti-parallel diode →O. The current is in the positive direction, the
inductance is in the positive energy storage, UAO is pinched to the midpoint O of the
DC bus, and the input potential of the rectifier is 0.When switch S1 and S2 are
disconnected, the current flow path is as follows: Ea→L1→D1→C1→O. The current
is in the positive direction, the inductor releases the stored energy, UAO is pinched to
the positive end of the point capacitance C1 in the DC bus, and the rectifier input
potential is Udc/2.
(2) When ac A phase voltage and current are both negative:
When the switch S1 and S2 are switched on, the current flow path is as follows:
O→S2→S1 anti-parallel diode → L1→Ea. At this point, the current is in the
negative direction, the inductance is in reverse energy storage, UAO is pinched to
the midpoint O of the DC bus, and the input potential of the rectifier is 0.When
switch S1 and S2 are disconnected, the current flow
path is as follows: O→C2→D2→L1→Ea. In this case, the current is in the
opposite direction, the stored energy of the inductor is released, UAO is gripped
to the negative end of the point capacitance C2 in the DC bus, and the input
potential of the rectifier is -UDC /2.
The potential at the input end of the rectifier under 8 different switch combinations is
shown
The operation of the Vienna rectifier is based on three switching states that
regulate power conversion efficiently.
Mode 1: Positive Half-Cycle Conduction
• When the input phase voltage is positive, the upper diode of the corresponding
phase conducts.
• The I G B T switch turns ON, allowing current flow from the AC source to the
positive D C - link capacitor (C1).
• The inductor (L) helps shape the input current to be sinusoidal.
Mode 2: Negative Half-Cycle Conduction
• When the input phase voltage is negative, the lower diode conducts.
• The switch turns ON, directing the current to the negative D C - link capacitor
(C2).
• The inductor continues to ensure a smooth sinusoidal current.
Mode 3: Freewheeling Mode
• During certain intervals, both the upper and lower switches are turned O F F .
• The current freewheels through the inductor, and the stored energy in the
inductor helps maintain a continuous current flow.
This three-level operation results in a balanced voltage distribution, reduced
stress on components, and improved power quality.
Explanation of PI Control in Vienna
Rectifier
PI (Proportional-Integral) control is widely used in Vienna rectifiers to regulate
D C - link voltage and input current to achieve high power factor correction (PFC)
and low Total Harmonic Distortion (THD). The control strategy involves two
cascaded control loops:
1. Outer Voltage Control Loop – Maintains a stable D C - link voltage.
2. Inner Current Control Loop – Shapes the input current to be sinusoidal and in
phase with the input voltage.
1. Outer Voltage Control Loop ( D C - Link Voltage Control)
Objective:
The voltage loop ensures that the D C - link voltage (Vdc) remains stable despite load
variations. This prevents excessive voltage fluctuations that could affect system stability.
How It Works:
• The measured D C voltage is compared with a reference voltage (Vdcref).
• The voltage error (difference between actual and reference voltage) is fed to a PI
controller.
• The PI controller adjusts the reference current (Iref) that the inner current control
loop should track.
Role of the P I Controller in the Voltage Loop:
• The Proportional term (KpV) reacts quickly to sudden changes in voltage.
• The Integral term (KiV) removes steady-state errors and ensures that the voltage
stabilizes at the desired reference.
• The output of this controller is the reference current (Iref), which the inner current
loop must track.
2. Inner Current Control Loop (Input Current Control)
Objective:
The current loop ensures that the input current follows the reference sinusoidal
waveform provided by the voltage controller, thereby achieving power factor
correction ( P F C) and reducing harmonics.
How It Works:
• The input current (I_in_actual) is measured and compared with the reference
current (I_ref) from the voltage loop.
• The current error is sent to another P I controller to determine the necessary duty
cycle for switching the Vienna rectifier’s PWM signals.
Role of the P I Controller in the Current Loop:
• The Proportional term (KpI) ensures fast response to current errors.
• The Integral term (KiI) eliminates steady-state error and prevents
drift.
• The output voltage signal controls the switching of IGBTs to
maintain sinusoidal current flow.
Combined Operation of Voltage and Current Control Loops
Step-by-Step Operation of P I Control in Vienna Rectifier:
1. The outer voltage loop monitors the D C - link voltage and generates the reference
current (Iref).
2. The inner current loop tracks this reference current, ensuring that the input current
sinusoidal and in phase with the AC voltage.
3. The P I current controller adjusts the P W M duty cycle, dynamically controlling the
switching of the IGBTs to regulate the power flow.
4. The system continuously adapts to load variations, ensuring stable voltage and powe
factor correction.
Advantages of P I Control in Vienna Rectifiers
Simple and easy to implement compared to advanced control methods.
Ensures stable D C - link voltage regulation.
Achieves near-unity power factor with proper tuning.
Reduces total harmonic distortion ( T H D ) significantly.
Provides robust performance under varying loads.
Limitations of P I Control
Slow dynamic response compared to predictive or sliding mode control.
May struggle with parameter variations, requiring periodic tuning.
Not inherently robust to non-linearities, unlike sliding mode or
adaptive control methods.
As we can see due to the reactive nature of the load the input current is not sinusoidal and is not in
phase with the voltage so this will lead to low power factor and high THD which in turn is
hazardous to the grid. To resolve this we will use different controllers to control the switches which
in turn control the inductors to inject current to make the input side current follow the voltage
attaining power factor near 1. Also the controller is used to balance the neutral point by controlling
the DC link capacitors.
The above graph of the input side current is recorded when controller is included. We
can see that with the help of controllers the inductor is discharged in specific intervals
of time so that the input side current is sinusoidal and follows the voltage with little
phase difference. But a little noise or distortion can be seen in the input side. This will
leads to THD but will be less than previous (5%-7%).
With the help of PI controller we will get power factor around 0.98 to 0.99.
And the stability of the circuit will also increase.
By choosing appropriate values for the input side inductors and DC link capacitors we
can reduce the noise/distortion.
(Here L = 0.6mH and C = 4000 micro F)
The desired output voltage level can be defined in the controller so that we can
step up or step down accordingly.
Here We have given 380V Line voltage with 50Hz as input and 600V as output.
Comparison of Control Methods for Vienna Rectifier
CONCLUSION
The literature on PI controllers in Vienna rectifiers highlights their effectiveness
in achieving power factor correction and THD reduction Their straightforward
design and ease of implementation have made them a popular choice for various
applications, including EV charging stations and renewable energy systems
However, it is essential to recognize their limitations, such as potential phase lag
and reduced effectiveness under substantial disturbances The ongoing research
and development of advanced control techniques, including sliding mode control
and model predictive control, represent promising avenues for further enhancing
the performance of Vienna rectifiers and addressing the evolving demands of
modern power systems As power electronics technology continues to advance,
integrating these sophisticated control algorithms will be paramount for achieving
higher efficiency, improved stability, and greater power quality in Vienna rectifier
applications. The insights from these studies will ultimately support the
deployment of more efficient and reliable energy systems, aligning with global
energy sustainability goals.
REFERENCES
1. A compound control strategy of three‐phase Vienna rectifier under ... (2021).
https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/pel2.12202
2. Voltage Oriented Controller Based Vienna Rectifier for ... (2021).
https://www.researchgate.net/publication/350368276_Voltage_Oriented_Co
ntroller_Based_Vienna_Rectifier_for_Electric_Vehicle_Charging_Stations
3. Design of a modified Vienna rectifier for power factor correction ... (2025).
https://ieeexplore.ieee.org/document/7760104/
4. Vienna Rectifier-Based, Three-Phase Power Factor Correction (PFC ... (n.d.).
https://www.ti.com/lit/ug/tiducj0b/tiducj0b.pdf
5. Voltage Oriented Controller Based Vienna Rectifier for Electric ... (2021).
https://ieeexplore.ieee.org/document/9386107/
6. PID Control of a Vienna Rectifier-Based Power Factor Corrector. (2021).
https://www.mathworks.com/videos/pid-control-of-a-vienna-rectifier-based-
power-factor-corrector-1614934525915.html
7. implementation of voltage oriented controller using vienna rectifier ... (n.d.).
https://www.jetir.org/papers/JETIR2304630.pdf
8. Vienna Rectifier-Based, Three-Phase Power Factor Correction (PFC ... (n.d.).
https://www.ti.com/lit/ug/tiducj0b/tiducj0b.pdf
