Single Phase Transformnerless grid tied Inverter

Project Title

Single Phase Transformnerless grid tied Inverter

Project Area of Specialization Shared EconomyProject Summary

Grid -tied  have now becoming choice of technique adopted by many electric supply companies based on Solar energy for net metering purposes .In this project we are making single phase Grid-Tied Inverter which is based on tranformerless technique .The basic function of this project is that it takes input from grid and make it as reference for inverter sot that it can generate output as exactly like grid voltage for sending it to grid when load is in off-state otherwise only operate load along  charging of  reachargeable battery .Sending voltage to grid should be  without any harmonics and also meets its standard. By doing literature review of several research papers ,this inverter is designed with prospect to domectic load so we are making it in single phase .As this inverter is only for domestic load so cost is economical factor ,that's why we are making it transformerless which would reduce its weight as well as cost .First input of 24Vdc is taken from solar panels and is converted into 312Vac using full bridge technique . After that that AC outptu is purified to reduce harmonics using TLCL filter technique .Most challenging part of this project is synchronization of output of inverter with grid which is WAPDA in our case. This process requires phase shifting and frequency matching for both grid and inverter output ..Dealing with 220Vac requires accurate calculatons as well as precise calibration otherwise current with flow in opposite direction from grid to inverter which will burn out whole model.

Project Objectives

Cost efficient            

Cost is most economical factor while making any product  suitable for large scale consumer specially in case of domestic consumers.We making this inverter transformerless which will reduce its weight which makes its cost to reduce .

Reduce isolation problems for highly efficient                                                                                              

As there is no transformer involved in this inverter so there will isolation problems between grid and inverter which will rise the problem of leakage current which reduce its efficiency .so, we are modified form of H6 toplogy in inverter to reduce leakage current  to get high effiency fro inveter .

Pure Sinosoidal wave at output                      

 Pure sinusiodal output wave is important for highly efficient and also for long lasting operation .

Reactive power flow                                                                                                                                                          

As most of load is now inductor in nature so inverter should allowreactive power to flow.Based on modified H6 toplogy this inverter is capable for reactive power flow.    

Project Implementation Method

1. 24Vdac is taken from solar panel and is converted into 312Vdc using boost converter .As we are making tranformerless inverter so input and output magnitude of inveretr should be same .
2.  After that ,full bridge technique based on  modified H6 topology is used for converting 312Vdc to 312Vac  and also this step also reduce leakage current problems This topology only uses HIGH POWER MOSFETS and for gate driving of MOSFETS we are using unipolar SPWM using microcontroller .
3. Then that inverter  output is purified using TLCL filter which would in pure sinusoidal waveform.
4. After that we come to synchronization part where 220Vrms is take from grid and is stepped down to 24V .This 24V and ouput of inverter will go to phase detector and synchronizor circuit which will detect phase difference between them and after that with operation amplifier phase shift technique their phases will be minimized . 
5. After that ,this whole model is connected to load for fuether testing .

Benefits of the Project

1. Net metering:
   The key concept to understand about a grid-tied system is that it gives you the ability to feed power to the grid during the day, when you may be producing excess energy, and to use the grid supply at night. Net metering is a billing process that credits the owners of grid-tied systems when they produce more energy than the home needs.Because grid-tied homes are usually net-metered, the power meter tracks this exchange between your solar system and the grid. Excess energy generation leads to your power meter spinning backward rather than forward, thus giving you a credit. The credit can be used to offset payments for future power usage.
    
2. No local industry for grid-tied inverter:
   Net-Metering using solar energy is started in pakistan since 2015 by few companies but none of them is making there  own grid-tied inverter which would be more economical factor for any company .All of these companies are importing grid-tied inverter which are high in cost and also increases its installation charges which would not inspire many customers .so,our project would be more  beneficial for these companies instead of importing it from foreign area .Also ,this project gives us motivation from entrepreneurship point of view.
     
3. Costs:
   To function properly, off-grid solar energy systems require more specialized equipment that gets expensive quickly. Clearly, less equipment generally means lower installation and maintenance costs. This happens to be the case with most grid-tied systems. Since the power grid functions as a battery for your system, you not only don’t have to pay for batteries, you do not have to pay for the maintenance that is involved with those batteries.Also ,this grid-tied inverter is transformerless which will further reduce cost.
    
4. Reliability:
   Solar panel systems are not perfect. There are bound to be days when efficiency is not what it could be and the system doesn’t produce enough. However, many of your daily (and nightly) activities will continue to require the use of electricity.
   Unlike off-grid systems which may run out of power, grid-tied solar systems are less likely to leave you in the dark at inopportune times. If the power generated from your solar panel system is less than optimal, extra energy will be pulled from the grid. The grid essentially acts as a backup for your solar energy system.
   Less energy is wasted as a result and the efficiency of your solar power system goes up. Except in the event of a power outage, you will always have access to electricity during any time of day, as long as your system is connected to the grid

Technical Details of Final Deliverable

1. Specifications of project:

   (a) Input voltage =24Vdc

     (b)Outputvoltage=312Vac      

     (c) Max Output  Power =500W   

     (d)  Inverter should charge the external rechargeable battery 

     (e) Inverter output should be synchronized with grid so if load is in off-state ,inverter output goes to grid othwerwise operate load .

     (f) Output frequency =50Hz     

     (g)   Switching frequency of mosfets=24kHz      

     (h)    Maximum Output Current=26A.

   
    
2. Overall cost  and completion date of project:
   Overalll cost for completing  this project is estimated to 32000 Rs . This project is estimated          to be completed within 5 months starting from March 20,2019.
    
3. Previously used topologies regarding transformerless inverter: 
   Several topolies have been proposed regarding trasnformerless inverter to reduce leakage current problems .Some of better topologies are H5,HRE ,HERIC and dual  converter ,but these topologies have some deficiencies .There is more concuction losses in them swictches operation at a same time is more .Also some of these toplogies don't include reactive power flow which wouldn't allow inverter to operate inductive load .And all of these tpologes have twon level output.
    
4. Used topology:
   We are using modified H6 topology which have least condcution losses as there are only two siwtches operate at a same time and aslo output harmonics are least with effeciency of 99.8% .This topology is also capable to operate inductive load.
    
5. Modulation scheme 
   We are using SPWM technique for generating pure sinusoidal wave at the output with the help TLCL filters .Output wave should be pure sin wave for long lasting operation of inverter and it will reduce noise effect.
    
6. Effeciency:
    Effeciency of inverter should macth with theoratical result which is approximately around 99%.
    
7. Synchronized output: 
   Output of inverter should synchronized with grid to deliver power to grid whithout harmonics and mismatched frequency .When load is in-on state inverter charge battery as well as deliver power to load .When load is in off-state,all the power would be deliver to grid.

Final Deliverable of the Project HW/SW integrated systemType of Industry Energy Technologies Shared EconomySustainable Development Goals Affordable and Clean EnergyRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	33125
ATMEGA 2560 Microcontrller	Equipment	1	1200	1200
Solar Panel 24V 500W	Equipment	1	8000	8000
IRF40 MOSFET	Equipment	8	60	480
Resistor	Equipment	12	10	120
Rechargeable Battery	Equipment	1	8000	8000
Isolation Transformer	Equipment	1	2000	2000
PCB Board 10x15	Equipment	4	600	2400
Fast-Blow fuse	Equipment	3	60	180
Connecting Wire	Equipment	10	150	1500
Arduino Wires	Equipment	20	10	200
LM741 IC	Equipment	2	60	120
LM585 PLL IC	Equipment	2	350	700
60W Blub	Equipment	3	80	240
Inductor	Equipment	5	40	200
Capacitor	Equipment	7	30	210
Research Papers IEEE	Miscellaneous	13	400	5200
Transport	Miscellaneous	1	2000	2000
Diode	Equipment	10	20	200
Potentiometer	Equipment	5	35	175