Grid tied PV Inverter

Project Title

Grid tied PV Inverter

Project Area of Specialization Shared EconomyProject Summary

The objective of this project is to design and implement a photovoltaic grid connected inverter system equipped with a maximum power point tracker. The developed system acts as a sinusoidal current source synchronized with the utility grid and is applicable for household use. A two-stage topology was developed to build the system. The first stage is a DC/DC converter which is controlled by a Maximum Power Point Tracking (MPPT) algorithm.
The second stage is a DC/AC inverter that converts DC power to AC power. Gate driver were developed as an intermediate layer between the microcontroller and the gates of the power transistors used in the converter and the inverter. The DC power produced by the PV panels is first passed through the DC/DC converter, which steps up the panels voltage to the required level at the DC link. A large DC link capacitor , provides power decoupling capability and therefore, reduces fluctuations that may lead to distortion at the output. Next, the DC/AC inverter, the filter and the 1:2 transformer altogether convert the DC power to AC and synchronize the phase, the voltage and the frequency with the grid. All measured signals such as current and voltage of the PV panels and the system output, DC link voltage, and the grid voltage are processed in the microcontroller. Based on the obtained measurements, the microcontroller issues two pulse width modulated switching signals: one for the converter control and one for the inverter control. The signals are passed through the gate drivers circuitry that provides amplification and isolation between high and low power components of the system. Overall system testing was performed and the system excluding the solar panels was able to connect with the grid and push power as well as being able to synchronize with the grid.

Project Objectives

The objectives of the project are economical and social in nature. It basically aims to:

1.design and fabricate three phase grid connected PV inverter with Net-Metering.

2.Promote the use of sustainable, economic and least-cost decentralized electrification solutions for areas not feasible for grid connection

3.Apply solar energy technology as the enabling technology for sustainable development.

4.Improve life style of people.

Project Implementation Method

Method  used for hardware impletmentation

1) PV array

¡Photovoltaic array absorb sunlight as a source of energy to generate electricity. A Photovoltaic modules constitute the photovoltaic array of a photovoltaic system that generates and supplies solar electricity in commercial and residential applications.

2) MPPT

MPPT or Maximum Power Point Tracking is algorithm that included in charge controllers used for extracting maximum available power from PV module under certain conditions. The voltage at which PV module can produce maximum power is called ‘maximum power point’ (or peak power voltage). Maximum power varies with solar radiation, ambient temperature and solar cell temperature

3) DC/DC converter

It is used to regulate DC voltage at desired output using MPPT.

4) Phase lock loop

In this technique inverter control converts the voltage and currents to per unit values. PLL takes the grid voltage and finds its angle and frequency. This plays an important role in making inverter output and grid angles equal. Clarke and Park transformation  converts three phase voltages and currents from abc to dq0 reference frame. Conversion into dq0 frame provides accurate control for the signals.

5) Inverter 

Dc-to-ac converters are known as inverters. The function of an inverter is to change a dc input voltage to a symmetric ac output voltage of desired magnitude and frequency. Voltage source inverter is the inverter topology where independently controlled ac output is voltage signal. The ac output voltage from inverter may be either fixed or variable. The input dc source may be fixed dc source or it may be rectified from fixed ac source. This dc voltage is converted to ac by using network of switches to alternate between positive and negative dc buses. The output magnitude and frequency is varied by controlling the switching sequence which is done by various modulating techniques. In this project, sinusoidal PWM generated using analog circuits is used as modulating signal to control the switching sequence.

6) Filter

Filter is used to remove harmonic in system.

Benefits of the Project

Grid Tie System is the simplest and most cost effective way to connect PV modules to regular utility power. Grid-Connected systems can supply solar power to your home and use utility power as a backup. As long as there is enough electricity flowing in from your PV system, no electricity will flow in from the utility company. If your system is generating more power than you are using, the excess will flow back into the grid, turning your meter backwards. The utility company will pay you for the electricity your home generates and deliver to grid.

Technical Details of Final Deliverable

1) PV array

The PV array is rated for 75 W of maximum power, 4.4 A of maximum power point current, and 17 V of maximum power point voltage.

2)DC/DC converter

The DC/DC converter is the hardware platform on which the Maximum Power Point Tracking is performed. The input voltage of the DC/DC converter provided by the solar panels is rated for 34 V at the maximum power point. The output voltage of the DC/DC converter is specified by the product specifications to be at 100 V.

3) DC/AC Inverter

The DC/AC inverter stage of the system is responsible for converting the DC power generated from the solar panels into AC power and transfer it to the electrical grid.Control to maintain constant voltage at the inverter output and for synchronization of the output frequency with the electric utility grid, phase locked loop and regulators have been designed and The output voltage of the DC/AC inverter is specified by the product specifications to be at 310 V.

4) Filter

Before connection to the grid, sinusoidal signals must contain a total harmonic distortion of less than 5% so filter is design to reduce harmonic in system.

5) Gate Drivers

The driver circuit takes in a 3.3 V input from the microcontroller and outputs the required gate voltage of 12V at a higher current to switch the gates of the DC/DC converter and DC/AC inverter.

Final Deliverable of the Project Hardware 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)	71535
PV panels	Equipment	2	8000	16000
IGBT	Equipment	6	800	4800
Bypass diode	Equipment	3	589	1767
Inductor	Equipment	1	25	25
Heat sink	Equipment	2	160	320
IGBT module	Equipment	2	2696	5392
DC-link Capacitor	Equipment	1	850	850
Inverter side Inductor	Equipment	1	1450	1450
Capacitor	Equipment	2	54	108
DC/DC driver	Equipment	5	586	2930
DC/AC driver	Equipment	1	1265	1265
Grid Side Inductor	Equipment	1	136	136
bootstrap diode	Equipment	3	106	318
bootstrap capacitor	Equipment	3	186	558
opto coupler	Equipment	6	118	708
buffer	Equipment	5	98	490
Xor gate	Equipment	1	86	86
Not gate	Equipment	3	24	72
bypass Capacitor	Equipment	10	32	320
half effect sensor	Equipment	3	628	1884
opto voltage detector	Equipment	3	724	2172
opto current detector	Equipment	3	682	2046
isolation amperlifer	Equipment	2	365	730
potential Transformer	Equipment	2	860	1720
Current transformer	Equipment	1	854	854
op-amp	Equipment	3	108	324
coupling capacitor	Equipment	10	50	500
variable auto transformer	Equipment	1	1860	1860
back-end transformer	Equipment	1	1800	1800
controller	Equipment	2	1100	2200
PCB board	Equipment	3	900	2700
battery	Equipment	1	7800	7800
shiping	Miscellaneous	7	250	1750
thesis book print	Miscellaneous	4	800	3200
market	Miscellaneous	12	200	2400