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Design and Implementation of Sinusoidal PWM Inverter (Paper ID: 212ET3011201505)


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Design and Implementation of Sinusoidal PWM Inverter

(Paper ID: 212ET3011201505)

Mr. Chetan G. Patel Mr. Amarpal R. Kanojiya

Electrical Engineering Asst. Prof. at Electrical Engineering Dr. Jivraj Mehta Institute of Technology, Mogar Dr. Jivraj Mehta Institute of Technology, Mogar

Anand, India Anand, India

Patelchetan304@gmail.com Amarpal.1986@gmail.com

Abstract: This Paper aims to generate pure sine wave with minimum Harmonics. SPWM is widely used in power electronics to digitize the power. SPWM switching techniques is commonly used in various industrial applications. Sinusoidal pulse width modulation techniques are characterized by constant amplitude pulse with different duty cycle for each period. This Pulses width are Modulated in order to obtain Inverter Output voltage and to decrease its Harmonic contents.

Here the unipolar and bipolar voltage modulation is selected because this method offer advantages of effectively doubling the switching frequency of the inverter voltage, thus making the output filter smaller, cheaper and easier to implement. SPWM is most useful method of Motor Control and Inverter Application. At the Desired frequency Triangular wave and sinusoidal wave are compared.

Keywords: SPWM (Sinusoidal pulse width modulation), Inverter, Unipolar switching, bipolar switching, Mat lab, Simulation, Modulation , UPS.


The Dc to AC converter is called Inverter. It converts DC Power into AC Power at desired output frequency and voltage.

Now a Days, Energy crisis are of special attention. Most of the available UPS are square wave or quasi sine wave inverter.

The available sine wave is not pure sine wave ant contents some harmonics and it will be damage some electronics devices The different topologies of sine wave are discussed in [1] The Sine wave inverter are widely used in different purposes . The output voltage waveforms of ideal Inverter should be sinusoidal. However, the waveforms of practical inverters are not sinusoidal and contain certain harmonics.


The Inverter Converts dc supply into ac supply. There are line commutated inverters and force commutated inverter. Phase controlled converters when operated in the inverter mode is called line commutated inverter.

The Inverter can broadly classify into two operations.

(1) Voltage source Inverter (2) Current source Inverter.

The Voltage source Inverter is one in which the DC Source has small or negligible impedance. The Current source inverter has high impedance. From Semi conductor devices inverter can be classified as

 Bridge Inverter

 Series Inverter

 Parallel Inverter Bridge Inverter can be classified as

 Half Bridge

 Full Bridge

Single Phase Full Bridge Inverter:

Fig. 1. Single Phase Full Bridge Inverter

As Shown In Figure 1 Single Phase Full Bridge Inverter. This consists of 4 switching devices, two of them on each leg. The Full Bridge Inverter can produce an o/p power twice that of the half-bridge inverter with the same i/p voltage. The SPWM switching techniques improves the characteristic of the inverter. The objective is to add a zero sequence voltage to the modulation signals in such a way to ensure the clamping of the devices to either the positive or negative dc rail; in the process of which the voltage gain is improved, leading to an increased load fundamental voltage, reduction in total current distortion and increased load power factor. In Figure S11 & S21 are top devices and S12 & S22 As a bottom Devices.

Vd/2 (S11-S12) = Van + Vno = Vao Vd/2 (S21-S22) = Vbn + Vno = Vbo

Vab = Van – Vbn

Where, Van,Vbn = Output voltage from phases A & B to a arbitrary point n,

Vno = The neutral voltage The switching function of the devices can be approximated by the Fourier series to be equal to ½ * M.

Where, M= Modulation Signal From the equation 1,2,3 expression

M11 = 2 (Van + Vno) /Vd M21 = 2(Van +Vno)

Upper two equation gives for the modulation signal for single phase DC to AC converters.



Single Pulse Width Modulation

In Single Pulse width Modulation control, there is only one pulse are Half cycle and the width of the pulses is varied to control the inverter output voltage The gating signal are generated by comparing a rectangular reference signal of the amplitude Ar with triangular carrier wave of amplitude Ac, The frequency of the carrier wave determines the fundamental frequency of output voltage. The Ratio of Ar to Ac is the control variable and defined as the modulation Index. [2][3]

Multiple Pulse width Modulation

The Harmonic content can be reduced by using several pulses in each half-cycle of output voltage. The generation of gating signals for turning on and off of transistors by comparing a reference signal with a triangular carrier wave. The frequency of the reference signal sets the output frequency f0, and carrier frequency fc, determine the number of pulses per half cycle p.

The modulation index control the output voltage the number of pulses per half cycle is found from,

P= fc/2f0=mf/2

Where, mf=fc/f0 is the frequency modulation ratio. This Type of modulation is known AS Uniform pulse width Modulation [4]

Sinusoidal Pulse Width Modulation (SPWM)

Instead of maintaining the width of all pulses the same as in the case of multiple-pulse modulation, the width of each pulse is varied in proportion to the amplitude of a sine wave evaluated at the center of the same pulse. The Distortion Factor (DF) a and low order Harmonics (LOH) are reduced significantly. The SPWM is commonly used in Industrial Application. The gating signals are generated by comparing a sinusoidal reference signal with a triangular carrier wave of frequency Fc. The frequency of reference signals fr, determine the inverter output frequency and its peak amplitude Ar, control the modulation index M, and Vrms output voltage Vo.

The Number of pulses per half cycle depends on carrier Frequency. [5] Inverter that uses a PWM Switching techniques have a DC input voltage that has usually constant in magnitude. The inverter work is to take this input voltage and output ac where the magnitude and frequency can be controlled. There are many different paths PWM can be implemented to shape the output to be ac power. A common technique is called SPWM. Now compare the sinusoidal waveform and triangular waveform. The inverter than uses the frequency of the triangular wave as the switching frequency. This is usually kept constant. [6][7]

Fig. 2. Compared Desired frequency with triangular waveform

Fig. 3. PWM (Pulse with generator)

Vcontrol < Vtriangular


: on , TA+

: off TA+

: on, TA-

: off Ma= Vcont/Vtria

Where, Vcont = Peak amplitude of the control signal IV. DEVELOPMENT OF SOFTWARE SYSTEM USING MATLAB

Before the Constructed Inverter, Required How to components selected and simulated. So everything built in mind purpose the efficiency and keeping power losses to a minimum. Now a Day for gating controlled AC Inverter is used. Inverter is converting Uncontrolled DC into Controlled AC. There are many Inverter types like three levels. Five level etc. It is very simple techniques for Harmonic Reduction. In this techniques Pulse Magnitude will be constant and pulse width (time) can be changed. In these Pure sine wave is compared with carrier wave and produce gate pulses and Harmonic can be reduced. The sine wave has Fundamental Frequency and carrier wave has more than Fundamental Frequency.


Fig. 4. SPWM Inverter Block Diagram


A. PWM with bipolar voltage switching B. PWM with unipolar voltage switching


A. SPWM with Bipolar Switching

Fig. 5. PWM Generator of bipolar Switching

Figure 5 shows the basic idea to produce PWM Bipolar voltage switching. A Comparator used to compare between the reference voltage waveform Vr with the triangular carrier signal Vc and produce the bipolar switching signal. When this pattern is applied at single phase inverter all the switches are turned on and turned off at the same time. The output of leg equal and opposite to the output of lag B.

When compare the reference signal and carrier signal than output voltage is determined.

Fig. 6. SPWM waveforms for Bipolar Voltage Switching

a. Triangular and Reference waveforms Difference b. Gating Pulses for S1 and S4

c. Gating Pulses for S2 and S3 d. Output Waveforms

In this system opposite switches s11, s21 & s12, s22 are turned on

or off at same time. The output of lag A is equal and opposite to the output of lag B. When compare the control signal and triangular signal than output voltage is determined. Figure shows the switching pulses for the devices, and the switching pattern and output waveforms. [8]

B. SPWM with Unipolar switching:

In this technique, the triangular carrier waveform is compared with two reference signals which are positive and negative signal. Produce SPWM with unipolar switching. The different between the Bipolar Sinusoidal pulse width Modulation generators is that the generator uses another comparator to compare between the inverse reference waveform –Vr. When two signal compare than produce the Unipolar voltage switching signal. In Unipolar voltage switching the output voltage switches between 0 and Vdc. The effective switching frequency is seen by the load is doubled and voltage pulse amplitude is halved. So the harmonic content of the output voltage waveform is reduced compare to bipolar switching. In unipolar voltage switching scheme also, the amplitude of the significant harmonics and its sidebands is much lower for all modulation indexes thus making filtering easier, and with its size being significantly smaller. Between o and –Vdc. This is in contrast to the bipolar switching strategy in which the swings between Vdc and –Vdc. AS a result, the change in output voltage at each. [2],[6]

Fig. 7. PWM generator of Unipolar Switching


Fig. 8. SPWM Waveform for Unipolar Voltage Switching

a. Triangular waveform and Reference waveforms Difference

b. Gating Pulses for S1 And S4

c. Gating Pulses for S1 And S3

d. Output waveform

In this method, the devices in one leg are turned on or off based on the comparison of the modulation signal Vr with a high Frequency triangular wave. The device in the other lag are turned on or off by the comparison off the modulation signal –Vr with the same high frequency triangular wave.


In this scheme the output voltage level changes between either 0 to –Vdd or from 0 to +Vd.


Design and test Unipolar voltage switching and also simulation in MATLAB.

Fig. 9. Matlab Simulink Model For Unipolar Voltage Switching

Fig. 10. Without Filter current and voltage output waveform For Unipolar Voltage switching

Fig. 11. With Filter Voltage and current output waveform for Unipolar Voltage switching

Fig. 12. Experimental Result of Unipolar Voltase switching Pulses

Table 1. Efficiency table for unipolar voltage switching (Experimental)

Load (W)

Vin Iin Pdc Vout

(V) Iout


Pac %


40 12.23 3 60 215 0.34 49.45 60

60 12.67 7 62 213 0.54 54.71 72

80 12.08 9 70 208 0.45 62.33 83

100 12.40 10 86 207 0.68 68.66 88 120 12.66 12 88 203 0.55 80.92 79


In this paper SPWM Microcontroller based inverter is designed and tested for fixed modulation index 0.5 and uses unipolar voltage switching. There are meets different results voltage and current for different resistive loads. The Maximum effiency is 88%. And also get better sinusoidal signal from simulation and also get Sinusoidal waveform.


[1] E.Koutroulis, J.Chatzakis, K.Kalaitzakis and N.C.Voulgaris. “ A Bidirectional, sinusoidal, high frequency inverter Design”, IEEEProc- Electr.power appl, Vol, 148, No. 4 July, 2001,pp.315-318

[2] Owen, E.L., "History [origin of the inverter]," Industry Applications Magazine, IEEE, vol.2, no.1, pp.64-66, Jan/Feb 1996


[3] Chien-Ming Wa ng, "A novel single-stage full-bridge buck-boost inverter," Applied Power Electronics Conference and Exposition, 2003. APEC '03.

[4] B. Ismail, s.taib mieee, a. R mohd saad, m. Isa, C. M. Hadzer,

“Development Of A Single Phase Spwm Microcontroller-Based Inverter” First international

[5] Clint Reitsma, Student Member, “An introduction to Inverters and Applications”

[6] B. Ismail, S. T. (November 28-29, 2006), “Development of a Single Phase SPWM Microcontroler -Based Inverter” , First International Power and Energy Conference PEC (p. 437). Putra jaya, Malaysia:


[7] Danny Li and Christian Ramos, “Design Of High-Low Unipolar Pulse Width Modulated Inverter”, Electrical Engineering Depart ment, California Polytechnic State University, San Luis Obispo, spring 2010.


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