Cost effective nano grid controller for distributed solar energy storage for small homes

Solar has a lot of potential in Pakistan due to the maximum presence of sun for the whole year. But the cost of installing solar PV system does not allow middle class people to use it. The biggest purpose of this project is to benefit the middle-class people from solar PV system. We are going to mak

Project Title

Cost effective nano grid controller for distributed solar energy storage for small homes

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

Solar has a lot of potential in Pakistan due to the maximum presence of sun for the whole year. But the cost of installing solar PV system does not allow middle class people to use it. The biggest purpose of this project is to benefit the middle-class people from solar PV system. We are going to make an ISMI that will be very suitable for middle class people at a very low cost. An intelligent single phase grid connected solar micro inverter of about 700W will manage the load and will store the distributed solar energy in small homes. It will be able to contact the other Nano-Grid controllers to take from them and send energy to them. People are installing the solar PV systems of 3KW to 10KW with the cost of approximately Rs.0.5M to Rs.1.5M and from net-metering they are giving their generation back to the distributed grid and subtracting their cost of bills. A superior class can afford this but a middle class can’t afford it. More than 60% population is living in small houses with the maximum load of approximately 1kw. They don’t need a system of more than 1KW with the heavy installment cost and roof space. In this project, we are focusing on these energy issues at the domestic level to make system cost-effective and affordable for the domestic consumers such that the cost of system can be minimized from Rs. 70,000 to Rs. 100,000. This Project will be an Intelligent Single-Phase ON-Grid Hybrid Solar PV Inverter that will serve the load in different cases and by Nano-gird synchronizing it will take energy and send back excess energy to Nano-grid. Such as, when solar PV is generating power ISMI will supply the load with charging the battery bank and send excess power to grid. And when the solar is not generating ISMI will supply the load through battery backup or synchronized grid. Our focus is to serve the load at any time. This product is affordable at small domestic level and will be cost effective for them. Moreover, this product can be used in small business sector to overcome the electricity interruption issues. From this product the energy crisis can be solved at small domestic level and small business sectors . [ISMI: Intelligent Solar Micro Inverter]

Figure 1. Main diagram

Project Objectives

• Designing and implementation of DC-DC Buck converter from 40V-30V for charging a 24V 100AH Battery Bank.
• Designing and implementation of DC-DC Boost converter from 24V-40V for discharging of Battery Bank.
• Designing and implementation of DC-DC Boost converter from 40V-110V to minimize the current at input of the inverter.
• Designing and implementation of H-bridge Mosfet based Inverter that will Invert 110VDC to 110VAC.
• Implementation of pure sine wave filter and transformer that will purify the signal and transform it from 110VAC to 220VAC.
• Implementation of intelligent micro-controller that will control Buck converter, Boost converter, Inverter Mosfet by generating pulses according to inputs of their voltages and currents.

 Designing and implementation of PLL (Phase Loop Locked) Circuit that will Synchronize inverter to Nano-Grid for sharing the energy with other small homes.

Project Implementation Method

• Inverter is a device which convert Dc voltage into Ac voltage, in this project we are making an intelligent controller-based inverter which will manage the energy in different situations. Our system will be single phase grid connected hybrid system. This system is intelligent and is controlled by the efficient Arduino controller. In this system for measurements and protection, CTs (Current Transformer), PTs (Potential Transformer) and relays are used. First of all, when system will start Arduino will measure the voltage and current of solar panel, Battery Bank, Grid and then take decisions by intelligent codding and work in the different cases. When solar PV generation is available, the controller will allow only solar power to feed the load and if the load if fully fed and generation is in excess then it will allow solar to charge the battery Bank. And if the solar is not fulfilling the need of load the controller will switch the grid’s breaker and will mix energy of solar with grid and sync them. In the case of extra generation, the controller will allow extra generation back to the grid.
• These are the three different cases, in which load will be served.

Case 1:

when G-pv > Load, it will charge the battery bank and feed to Grid by synchronization. If our battery bank voltages are dropped than referenced fully charged voltages of 24v battery then controller will close the battery charger circuit breaker and excess power will be saved in the form of charged battery backup. Otherwise, excess amount of energy will be saved and shared back to grid.

Case 2:

When G-pv < Load, it will mix power from Grid, Gpv and Batteries. If battery bank voltages are normal then it will close the battery bank circuit breaker. Otherwise, controller will synchronize the inverter with grid by measuring frequency, voltages and angle of voltage signal.

Case 3:

When G-pv and Grid are absent, Battery will be used as UPS. If both sources are not available the it measures battery bank voltages and shift the load to battery backup. If battery bank is 50% to 60% charged then 50% not compulsory load will be switched off. In this way system will be protected and will be life longer for batteries so that load could be served for maximum time.

Main Block diagram:

Figure 2.Main Block Diagram

• Flow-Chart:

Figure 3. Main Process Flow chart

Benefits of the Project

• This product will be very beneficial for small homes who can’t afford the large Solar systems with so much installation cost.
• Small business shops (tailor and Barber shops etc.) who work 24/7, they will use their load without any interruption.
• People with lesser income can easily install this product in the range of Rs.50k to 60k.
• This product will be energy saving that is able to send back the excessive amount of energy back to the grid and protect the grid form overloading in peak energy hours. 
• It is that kind of energy that has no greenhouse effect and no gas emissions from fossil fuels. It is a good replacement to diesel or gas engines that used in rural electrification. Initiative towards the project creates economic development and produce jobs in manufacturing, repairing and installation of project.
• Most of the population of Pakistan is categorized as lower middle class who can’t afford expensive electricity. Our project will enable such sort of class for the electricity to be installed as well as managed at a pretty reasonable cost.

Technical Details of Final Deliverable

• The voltage on the output of the solar terminals is 40v. we will design a boost converter of 40v-110v for giving the 110v to the input of the inverter.
• Inverter will take 110v dc from boost converter and then convert it into ac using Mosfet H-bridge. Then this 110Ac will be given to the transformer which will convert it into 220v and then this 220v will be given to pure Ac filter which will convert it into pure A signal.
• There is a Battery backup  of 24 volt which will be charged as a backup source. So, the buck converter will be designed for lowering the voltage from the dc bus of solar PV. This buck converter will step down the voltage from 40v to 30v from which the battery of 24v will be charged.
• As we know that the battery is a back up source which will be used when needed so we will design a one more boost converter of 24v-40v which will boost the voltage at 40v and connect with solar dc bus.
• PLL circuit will take 220v from grid convert it into 5v dc and will to the controller. Controller will measure the frequency and phase of this signal and generate a PWM signal. This signal will be fed to the inverter so the inverter will do switching according to this wave.

Designing:

Solar PV:

We are using 2 panels of solar pv each of 350 watts 12v monocrystalline. The full load voltage of each panel is 40 volts so we are connecting them in parallel which means that the voltage at the output terminals of solar panels will be 40v and currents will add. And we will make the remaining products according to the voltages of the at the output terminals pf solar pv.

Buck converter(40v-30v):

Boost converter(40v-110v):

Boost Converter(24v-40v):

Inverter:

Rectifier:

Battery:

Battery will be used as a back up source and will be used when needed. It will be charged from both solar and grid. We are using 24v 70Ah battery lithium ion battery

Controller (Arduino):

Arduino will be used as a controller which will manage all the cases according to the situations. The whole system will be made intelligent from this intelligent controller.

Final Deliverable of the Project

Hardware System

Core Industry

Energy

Other Industries

Education

Core Technology

Clean Tech

Other Technologies

Others

Sustainable Development Goals

No Poverty, Affordable and Clean Energy

Required Resources

If you need this project, please contact me on contact@adikhanofficial.com