SVPWM Rectifier
Transcript of SVPWM Rectifier
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