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| Hybrid Grid connected Solar Power Inverter | ||||||||||||||||||||||
| Paper Id :
16333 Submission Date :
2022-08-12 Acceptance Date :
2022-08-19 Publication Date :
2022-08-25
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| Abstract |
This paper proposes a simpler synchronized series RC phase angle control based push pull inverter topology using parallel combination of Power MOSFETS and a step up center-tap transformer to convert DC power available through solar panels, supported by battery backup to AC grid. A single phase quasi square wave three level inverter is employed to convert Solar DC solar power to a quasi square AC voltage, using a step-up centre tap transformer. The output voltage and phase angle of the inverter connected to the AC bus is kept controllable by duty ratio control and phase angle cantor respectively. A proposed prototype inverter model tested to verify power fed to 230 Volts AC supply.
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| Keywords | MOSFET, Transformer, Inverter | |||||||||||||||||||||
| Introduction |
Sun Energy is abundantly available unending energy from sunlight where as non – renewable energy resources are depleting fast. The proposed topology can be utilized for minimizing electric bills during the availability of AC power and also for making the availability of AC power in case of power failure or stand alone mode. During stand alone mode the ac power will be generated using independent free running oscillator. All countries are moving toward the renewable energy. The advantage of hybrid green energy utilization system is that the power can be utilized during power failure also.The battery is continuously charged with the solar panel and the stored energy in battery is converted into AC voltage using inverter circuit. In presented scheme a battery charge controller is employed to continuously charge the battery with solar PV panels. Earlier, following researchers have contributed to utilize solar power and also to feed power to a single phase AC system. Off grid applications, sine wave PWM modeling have been explained in[1-4] Power Quality in Grid connected Renewable Energy systems [5] and SCR based solar to grid feedback is explained in[6].Capacitive isolated solar to grid is explained [7] Design technique of mixed solar power inverter system for connecting to the grid is presented in [8].Novel yet simpler method for synchronized phase shifting for grid power control with improved power quality using only simple two sets of parallel connected semiconductor switches is proposed with experimental results have been presented in this paper. A well known push pull inverter topology with parallel connected MOSFETS to minimize conduction losses and obtaining increased current rating is used to convert DC power having low voltage and high current to high voltage low current line synchronized
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| Objective of study | A simple push-pull inverter using 4/6/8 MOSFETs IRFZ44N 150 has been fabricated. Initially to test the performance of the system for 150 W, 440V Quasi Square wave Inverter to minimize the harmonics using 9V-0-9V/230V, 50 Hz, center tap transformer are connected as shown in Fig.3. Two synchronized AC pulse using RC phase shift limb connected across the supply is used to obtain two 180 phase shifted gate pulses which are generated using zero crossing detector circuit across resistance of the RC branch and fed to the four parallel connected MOSFETs bank of push pull inverter.Synchronized phase shifted gate pulses are generated and fed to the two MOSFET banks (four MOSFETs connect parallel) are alternately are switched on and off.Generated solar DC power is feedback to grid by controlling the leading phase shift angle of inverter by controlling pulse width and phase shift of the gate pulses by using control circuit working test modal is created and tested successfully. |
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| Methodology | Inverter to minimize the harmonics using 9V-0-9V/230V, 50 Hz, center tap transformer are connected as shown in fig 1. Two 180 phase shifted gate pulses are generated and fed to the Eight MOSFETs are alternately are provided from our control circuits shown in Fig.2. The practical gate pulse controller have been fabricated using IC 555, IC 324 and IC 4017 to generate controllable variable Gate pulses with variable pulse width as shown in Fig.6. These pulses are generated either independently or in synchronized mode depending upon whether we wish to operate in stand alone or grid connected mode. The Solar Power to be feedback to grid is controllable by R-C phase shift circuit by varying the value of resistance and power factor is controlled by pulse width of the gate pulses from control circuit. |
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| Analysis |
Fig 1: Block diagram proposed grid connected solar inverter
Fig 2: Concept and circuit for proposed Buck-Boost Charge controller
Fig 3: Schematic Diagram of Power Circuit of proposed Push–Pull Inverter. Proposed three level solar inverter feeds 50 Hz ac power to the ac low voltage bus of 230 volts AC.A simple push-pull inverter using 4 MOSFETS IRFZ44N in parallel in each push pull inverter limb have been fabricated.A150 W, 440V Quasi Square wave Inverter to minimize the harmonics using 9V-0-9V/230V, 50 Hz, center tap transformer are connected as shown in fig 1. Two 180 phase shifted gate pulses are generated and fed to the Eight MOSFETs are alternately are provided from our control circuits shown in Fig.2. The practical gate pulse controller have been fabricated using IC 555, IC 324 and IC 4017 to generate controllable variable Gate pulses with variable pulse width as shown in Fig.6. These pulses are generated either independently or in synchronized mode depending upon whether we wish to operate in stand alone or grid connected mode. The Solar Power to be feedback to grid is controllable by R-C phase shift circuit by varying the value of resistance and power factor is controlled by pulse width of the gate pulses from control circuit. Prototype working model is and tested successfully is shown in Fig 2.High frequency 25 kHz, Buck-boost converter is employed to charge the Battery bank under different solar intensity and load power and load conditions operating under MPPT .Duty ratio of the buck boost is controllable from 16Volts to 20volts. Output voltage Buck boost converter is controlled using Duty ratio control. Power Circuit A simple push-pull inverter using 4/6/8 MOSFETs IRFZ44N 150 has been fabricated. Initially to test the performance of the system for 150 W, 440V Quasi Square wave Inverter to minimize the harmonics using 9V-0-9V/230V, 50 Hz, center tap transformer are connected as shown in Fig.3. Two synchronized AC pulse using RC phase shift limb connected across the supply is used to obtain two 180 phase shifted gate pulses which are generated using zero crossing detector circuit across resistance of the RC branch and fed to the four parallel connected MOSFETs bank of push pull inverter.Synchronized phase shifted gate pulses are generated and fed to the two MOSFET banks (four MOSFETs connect parallel) are alternately are switched on and off.Generated solar DC power is feedback to grid by controlling the leading phase shift angle of inverter by controlling pulse width and phase shift of the gate pulses by using control circuit working test modal is created and tested successfully.
Control Circuit For off grid applications a100 Hz oscillator is used in a stable multi vibrator mode. For grid connected system a series resistance capacitance RC limb is connected across the AC side of the control circuit and an ac voltage across resistance R is used to generate the phase shifted synchronized square pulsesThisSquare wave clock pulse at pin 3 are fed to dived by two digital divider using IC 4017.The Control circuit of solar power inverter with stand alone mode. These pulses are fed to the base of two pulses amplifier through pulse amplifier using transistor BC547. The complimentary output from output from driver circuit using transistor are fed to two Power MOSFET banks MOSFET banks are connected to the power circuit in pushpull configuration. The ac voltage output across low voltage winding of centre tap transformer is fed to the low voltage grid using step-up transformer whose high voltage winding terminals are connected to the AC grid .This way the low voltage AC from push pull inverter is step up to 230 volt AC. |
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| Result and Discussion |
Experimemntal Results
Fig.4 Low voltage side, inverter voltage AC 50 Hz waveform, at 70% duty ratio quasi square wave
Fig.5 Low voltage side, inverter voltage AC 50 Hz waveform, at 40% duty ratio quasi square wave
Fig.6
Complementary Gate pulses for maximum inverter voltage for square wave output Table
1.Phase angle Vs Solar inverter output power fed to grid
Experimental Results: Fig.5 Shows Low voltage
side, inverter voltage AC 50 Hz waveform, at 40% duty ratio. Fig.6 Shows Complementary
Gate pulses for maximum inverter voltage for square wave output at 50% duty
ratio. Table
1and Fig. 7, shows the increase in output power fed from solar hybrid inverter
to the grid as the inverter phase angle becomes leading. The phase angle is variable
from 0-90 degrees using variable resistance of R-C series branch with upper
terminal of the capacitor connected to the ac source available from transformer
and bottom terminal of their resistance is connected at the other terminal of
ac supply available across low voltage side of the 230V to 9 Volt transformers. The increase in output power fed from solar hybrid
inverter to the grid as the inverter phase angle becomes leading. The phase
angle is variable from 0-90 degrees using variable resistance of R-C series
branch with upper terminal of the capacitor connected to the ac source
available from transformer and bottom terminal of their resistance is connected
at the other terminal of ac supply available across low voltage side of the
230V to 9 Volt transformers.
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| Conclusion |
From the experimental results it is concluded that the power fed to grid using 3 level inverter increases as the leading phase shift angle between ac grid voltage and inverter ac voltage is increased from 0 to 90 degrees. The maximum power fed to the grid is found near 90 degrees leading with respect to ac grid voltage. In absence of grid power the solar power can be utilized using independent 100 Hz square wave oscillator to obtain 50 Hz quasi square wave output 230 volts Ac supply .which can be used to drive domestic electrical utilities.The proposed hybrid inverter has therefore the specialty that it can feed to the ac grid during availability as well as non availability of ac grid supply. It can also provide the ac power in absence of sun energy for some time because of the power stored in the battery. During availability of grid supply it will minimize the electric bills if net metering type energy meter is used. The proposed scheme is very simple and economic easily applicable. |
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| References | 1. Amir MushtaqPalla. Nipun Aggarwal, “ Desing of Hybrid Grid-Connected inverter for renewable Energy Generation with power QualityConditioning” IJRTE ISSN:2277-3878, Volume-8 Issue-3,September 2019.
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7. Khadem, Basu, Conlon, "Power Quality in Grid connected Renewable Energy systems: Role of Custom Power Devices", European Association for the Development of Renewable Energies, Environment and Power Quality, 2010.
8. T I Maris, St. Kourtesi, L. Ekonomou and G.P. Fotis, “Modeling of a Single- phase Photovoltaic Inverter”, Elsevier Journal on Solar Energy Materials and Solar Cells, 91(18), pp. 1713-1725,November 2007. |
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