This project is used for safety purposes, many photovoltaic (PV) systems are designed using galvanic isolation and transformers. This topologies and transformers are expensive. This inverter has high efficiency and cheaper. The inverter is do not contains shoot-through issues. The proposed inverter can easily operate on higher switchingfrequencies due to low switching loss and low conduction loss ofthe power devices maintains high efficiency.
This transformer less inverter main purpose is maximizing the efficiency and reliability as compared to all possibleconfigurations. And also reduce the leakage current. Inverter has reduced the expensive ofthe transformer and weight. This inverter is used six power devices and six diodes for producing the single phase inverter output. And the four inductors are used for reduce the leakage current and spillage current.
Transformer less inverter has four differentoperating modes in one grid cycle. In the positive half-line gridcycle, a sinusoidal reference signal Vcontrol modulates the highfrequencyswitches S1 and S3 and S5 is always in ON position. D5is reverse biased when S1 and S3 are ON, the inductor currents ofiLo1 and iLo3 are equally charged. When S1 and S3 are deactivated,grid receives the energy from DC source. To avoid the CM leakagecurrent, the diode D5 and switch S5 provide the inductor currentiLo1 and iLo3 which provides the freewheeling path whichdecouples the grid from PV panel. In the positive half-line gridcycle, coupled inductor L2 is inactive. Likewise, in the negative half cycle, S6 remains ON and S2 and S4 are changed at highfrequency. Freewheeling occurs through S6 and D6.
Block Diagram Explanation
- Pulse generator: - Here we have used PIC microcontroller (PIC 16F877a) to generate PWM signal.
- Driver circuit: It is used to amplify the pulses and provided isolations using opto coupler. It has two functions,
- Bridge Rectifier: It converts AC supply to DC Supply.
- Transformer less Inverter: This inverter is converts DC voltage into AC voltage.
Pic Controller Board
The PIC controller is used to generate the PWM pulses for converter and inverter circuit. The PIC controller pulses are given to the driver circuit as input. Driver board is mainly used to isolate and amplify the input signals from the controller. The amplified driver output is connected to the main power circuit devices. The power transformer is connected to bridge rectifier and this rectifier is converts ac supply into dc supply. Dc supply is applied to transformer less inverter and inverter is converts the dc supply into ac supply. The inverter output waveform is shown in the below.
Circuit Diagram For Transformer Less Inverter
- High efficiency
- Reduce the leakage current
- Low cost
- PV applications
Inverter has the ability tooperate at higher switching frequencies while maintaining highefficiency with the use of super-junction, which enables reduced cooling requirements and results in systemcost savings by shrinking passive components. TL inverter is also suitable for gridconnectedsolar PV systems.
Output Waveform For Inverter