Three Phase PWM Rectifier using SVPWM

Guided By: Prof. Dhiren Rathod

Presented By: Viraj Selarka 13BEE100 Prem Shah 13BEE105

MINI PROJECT 2Mini Project II

Objectives:

• Mitigate the problem of non-sinusoidal input current found in rectifier and reduce T.H.D in permissible range.

• To analyse the steady state and dynamic response of the converter using SVPWM.

Project Planning• Introduction• What is rectifier?

• Controlled• Uncontrolled

• Controlled PWM Rectifier• Concept of SVPWM• Simulation of 3 phase rectifier using SVPWM(Open

Loop Control)• Simulation of SVPWM Control Algorithm(Closed

Loop control)

Rectifier Rectifier is used for rectification, which is the process of

conversion of alternating input voltage to direct output voltage.

Types of rectifier :-

• Uncontrolled• Single Phase• Half Wave• Full Wave

• Three Phase

• Controlled• Single Phase• Half Wave• Full Wave

• Three Phase

Analysis of Uncontrolled Rectifier

• We have observed from the simulation of uncontrolled rectifier that %THD in Input Current is not in permissible limit.

• And the main disadvantage is output voltage cannot be controlled.

• We can also use Phase controlled Method but the problem of THD won’t be mitigated by this method.

• Due to the above reasons we have to move to Controlled PWM Rectifiers.

PWMPulse Width ModulationIt is a method used to control the output voltage (amplitude and frequency) of a converter by modulating the width of the pulses of the output waveform

Main advantages of PWM control:• Filter requirement is reduced• Amplitude and frequency can be control independently• Significant reduction in THD of load current

Disadvantages of PWM control:• More complex control circuit• Higher switching losses

PWM Techniques

• Single pulse width modulation

• Multi pulse width modulation

• Sinusoidal pulse width modulation

• Space Vector pulse width modulation

Advantages of SVPWM over other Techniques

• Compared to SPWM and THIPWM with the same modulation index, the THD of SVPWM is slightly lower.

• SVPWM can achieve 15% more basic component than SPWM.

• Decrease of input current THD and increase of power factor are desired.

Space Vector Modulation• SVPWM is accomplished by rotating a reference vector around

the state diagram, which is composed of six basic non-zero vectors forming a hexagon.

• A typical converter(DC –AC , AC –DC ), comprises of three poles and two switches per pole so total of six switches.

• A converter can be driven to eight switching states where the converter has six active states (1-6) and two zero states (0 and 7).

General Block Scheme

Block Diagram

Generation of Va, Vb and Vc:

Basically there are two ways by which we can generate Va, Vb and Vc:1) Va, Vb and Vc all three can be generated using DSP or any

other controller by defining values of each samples by coding.

2) They can be sensed from the Source voltage itself.

3-Phase to 2-Phase conversion:

• 3-Phase to 2-Phase conversion is required to reduce the complexity of algorithm.

• The 3-phase to 2-Phase conversion can be done by Clark’s Transformation.

Source: High power converters and A.C Drives by Bin Wu

Park’s Transformation

• Park’s Transformation is alpha-beta to d-q.• d-q is rotating reference axis.

PI Regulation

• Output of the PI block will be in d-q axis.

• It is then converted into alpha-beta.

• Alpha-beta is then converted in sin and cos.

• And then gate pulse is generated through Dwell time calculation.

• Sector is determined by the angle of the reference vector.

Defining Real And Imaginary terms:

• By Converting Valpha and Vbeta into Cosinusoidal and Sinusoidal terms We can define real and imaginary terms of equivalent space vector.

Sin=u(2)/(sqrt(u(1)*u(1)+u(2)*u(2)))Cos=u(1)/(sqrt(u(1)*u(1)+u(2)*u(2)))

Where, u(1) = Valpha

u(2)= Vbeta

Conversion of Rectangular co-ordinates to Polar form:

• The obtained rectangular co-ordinates of space vector can easily be converted to its polar form

• The reason behind this conversion is to obtain the amplitude of the space vector and with the help of theta; the sector determination is done.

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Sector Determination

Source: Phuong Hue Tran,” Matlab/ Simulink Implementation and analysisof three PWM Techniques.”

Dwell time Calculation:

• Now values of Ts Ta and Tb can also be calculated:

Source: High power converters and A.C Drives by Bin Wu

Dwell time calculation:

• After calculation of Dwell time is done; This time is then compared with the ramp timer signal. Depending upon the location of the time signal, the switch state is defined. This switch state is then passed on to the inverter block. And Corresponding Vector is selected depending upon its dwell time.

• But in order to obtain above result; We first have to define the vectors corresponding to the sectors which they form.

Source: Phuong Hue Tran,” Matlab/ Simulink Implementation and analysis of three PWM Techniques.”

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Switching states for SVPWM

Source: Phuong Hue Tran,” Matlab/ Simulink Implementation and analysis

of three PWM Techniques.”

Output Voltage

R-L-Load R=100, L=2e-3

Input Current &Voltage

% THD of Input Current

Dynamic Response

References

1. Power Electronic Converter by P.S.Bimbhra.

2. Phuong Hue Tran,” Matlab/ Simulink Implementation and

analysis

of three PWM Techniques.”

3. Shutuan Zhang, Kai Zhang, Zhongshan Jiang and Fang Lu,

“Modeling and Simulation of Three-phase Rectifier Based on

SVPWM. ”

4. High-Power Converters and AC Drives by Bin Wu.

THANK YOU