An inverter is an electric apparatus that changes direct current (DC) to alternating current (AC). It is not the same thing as an alternator, which converts mechanical energy(e.g. movement) into alternating current. Direct current is created by devices such as batteries and solar panels. When connected, an inverter allows these devices to provide electric power for small household devices. The inverter does this through a complex process of electrical adjustment. From this process, AC electric power is produced. This form of electricity can be used to power an electric light, a microwave oven, or some other electric machine.

1. Presented
By
M. Pavan Kumar.
Reg.No:159Y1A0253.
Department of EEE.

2. CONTENTS:
1. Introduction.
2. Technical background on inverter.
3. Over view of advanced inverter functions.
4.Impacts and challenges of advanced inverters adoption.
5. Advancements in PV inverter.
6. Some advancements in application.
7. Market.
8. Conclusion.

3. INTRODUCTION
1.Inverters are power electronics-based devices which convert direct
current (DC) to alternating current (AC).
2. This function is fundamental to the integration of power from many
sources into the distribution system.
3.Widely used in photovoltaic, wind turbine generators and energy storage
resources.
4.In these applications, inverters convert a generated or stored DC to a
precisely modulated and grid synchronized AC waveform.
5. Beyond this fundamental purpose, there exist a range of
complementary, technologically viable, and demonstrated functions that
an inverter may be designed to provide

4. 6.As DER (Distribution Energy Resources) become incorporated onto the
grid at higher penetration levels, advances in inverter functionalities
represent a significant opportunity to improve the stability, reliability, and
efficiency of the electric power distribution system.

5. TECHNICAL BACKGROUND ON INVERTERS
Standard Inverter Key Concepts:
1.Fundamentally, an inverter is a device which converts a direct current
(DC) input to an alternating current (AC) output.
2. Inverters are used in a range of applications, including consumer
power electronics, electric vehicles, and photovoltaic and energy
storage interconnections to power distribution systems at the primary
(4 kV, 13.8 kV, 27 kV, and 33 kV) and secondary (120/240 V, 120/208 V,
240/480 V) levels.
3. In distribution applications, these devices produce a sinusoidal
waveform of the appropriate frequency.

6. 4.Inverters may be
1.Stand alone(off-grid): supply generated or stored power solely to
connected loads.
2. 2. Grid tie : allow generated or stored power to be supplied to a utility’s
distribution network when not needed by the load.

7. Standard Inverter Functionalities:
1.Power Transfer Optimization:
A.Inverters are designed to optimize transfer of power from DER to load,
often through a technique called Maximum Power Point Tracking (MPPT).
B. Based on computation of the ideal equivalent resistance from
measurements of current, voltage, and the respective rates of change.
2.Voltage Conversion:
A. In order to supply power to a load or to the distribution grid, power
generated by a distributed energy resource usually must be delivered at a
different voltage.

8. 3.Grid Synchronization:
A.A central component of an inverter’s efficacy is the ability to construct
an output AC waveform that is synchronized with the utility
distribution system.
4.Disconnection:
A. When fault conditions are present, a grid-tied inverter is required to
disconnect from the distribution system at the point of common
coupling (PCC).
5.Storage Interfacing:
A. inverter may enable the integration of a battery or other energy
storage device with a distributed generator.

9. 6.Anti-islanding protection:
A. Normally, grid-tied inverters will shut off if they do not detect the
presence of the utility grid.
B. There are load circuits in the electrical system that happen to resonate
at the frequency of the utility grid.
C. The inverter may be fooled into thinking that the grid is still active
even after it had been shut down. This is called islanding.
D. An inverter designed for grid-tie operation will have anti-islanding
protection built in; it will inject small pulses that are slightly out of
phase with the AC electrical system in order to cancel any stray
resonances that may be present when the grid shuts down.

10. OVERVIEW OF ADVANCED INVERTER FUNCTIONS
A. Advanced Inverter Key Concepts :
d An advanced inverter has the capacity of as follows
1. To supply or absorb reactive power
2. To control and modulate frequency and voltage, and
3. Voltage and frequency ride-through.
Capacitors could be installed to either supply or absorb reactive power.
Practical limitations include:
A. Limited variability of reactive power that can be supplied or absorbed
dependent on the ability to switch on/off various combinations of capacitors at
a location.
B. Reactive power supplied or absorbed by capacitors will greatly change with
minor changes in voltage level.
As a flexible source and sink of both active and reactive power, advanced
inverters provide an opportunity for the extensive control that enables safety
and reliability in DER applications.

11. B.Advanced Inverter Functionalities:
1.Reactive Power Control:
Definition: The presence of inductive loads results in a phase difference between
voltage and current waveforms, causing losses which reduce the efficiency of real
power distribution.
Less efficient power distribution requires greater current, which magnifies the impact
of line losses.

13. Implementation:
1.The supply of reactive power via capacitors will cause the phase of the
current to lead that of the voltage, while the opposite may be achieved
when an inductive load absorbs reactive power.
2.Integrated thyristor-switched capacitors and capacitors, functioning
together as a Flexible AC Transmission System (FACTS), Solid-state-
and power electronics-based compensators, allow increasingly rapid
and exact provision of reactive power.
3.Advanced inverters, combined with existing FACTS infrastructure and
control Systems.

14. 5.A capability curve prescribes the output reactive power, which is
diminished at lower voltage levels and at higher output active power.
6.These inverters control power factor according to the characteristic
capability curve in order to match the mix of resistive and inductive loads
on the circuit.
Impacts:
1.significant potential to increase efficiency and flexibility of power
distribution.
2.providing sufficient resolution in controlling reactive power.
3.precise modulation of reactive power supplied to the conductor and
load.

15. 2.Voltage and Frequency Ride-Through:
Definition: Ride-through may be defined as the ability of an electronic
device to respond appropriately to a temporary fault in the distribution
line to which the device is connected.
Standard inverters are required to identify a typical fault and
disconnect from the circuit when a fault is detected.
This course of action will inhibit the DER’s operation and prevent it
from functioning under the restored normal conditions.

16. Implementation:
Ride-through capabilities are tied to measurements of the distribution
system’s AC frequency and voltage.
 Ride-through functionality is highly dependent on monitoring, processing,
and algorithmic response.
controlling algorithm will implement a response, such as an increase in
power in response to a low voltage.
If the condition persists and the inverter fails to reach sufficient parameters
within the IEEE 1547 disconnection time frame, the disconnection will take
place as with the standard inverter, ceasing all ride-through responses.
Sags and swells in voltage levels can be remedied by the injection of reactive
power into the line.
Disadvantage: In non-utility scale DER applications such as residential and
small commercial, if ride-through is permitted by standards to prolong the
presence of a fault, people will use a fault circuit to greater risk of damage.

17. IMPACTS & CHALLENGES OF ADVANCED
INVERTERS ADOPTION
Impacts:
1) reactive power control increases efficiency of power distribution by
reducing line losses.
2) The voltage and frequency ride-through functionalities provide
dynamic grid support in the presence of a fault along the
interconnected line.
3) Avoiding “unnecessary” disconnection, especially of large
distributed energy resources, could improve grid reliability.

18. Challenges:
1.These inverters should be integrated with utility distribution
management systems.
Advanced functionalities would work with integration of inverters with
data management system
2. Different safety requirements and standards are to be implemented for
residential and small commercial applications.
3.EPRI(Electric power Research Institute) conducting a study indicating
that over 69% of downtime events are caused by PV inverters.
4.The main contributors to these failures were software bugs material
failures indicating that ,which indicates a need for significant refining
of the inverter technologies being developed.

19. ADVANCEMENTS IN PV INVERTER
Over the last 40 years, solar panels are connected together into strings
and the DC power is wired to a large inverter in a central location
called string inverter.
In 1990s, Micro inverter technology came into existence, in which
inverter installed behind each solar module. All the inverters
connected through busbar.

20. STRING INVERTER
For string inverter systems, individual
solar panels connected into series
strings with each other, deliver
accumulated DC voltage to a single
inverter that transforms the Direct
Current from the entire PV array into
grid-compliant AC power that is fed
into the power grid.
Of all the inverters, the most common
one found in most residential
installations is the string inverter.
Depending on the size of your solar PV
system, multiple string inverters might
be needed.
MICRO INVERTER
These are actually small DC to AC
inverters rated to handle the power
output of a single panel.
Of all the inverters, the most common
one found in most residential
installations is the string inverter.
Individual panel monitoring
Easy to expand
Arguably a safer technology.
 Each panel's individual AC supply is
then combined and fed to your home or
business the same as that from a string
inverter system.

21. SOME ADVANCEMENTS IN APPLICATION
In Air conditioner:
1.Compressor motor is driven by inverter to control its speed.
2.Inverter technology provides a more precise room temperature without
the temperature fluctuations

22.  A microwave inverter is a system used in microwave powering which
uses inverter power supply as opposed to traditional magnetic coils or
transformers. It is more efficient and powerful.
Other applications include welding, HVDC, UPS, LCD screen, Electric
tasers, Hybrid vehicles etc.
Market
Enphase is one of leading suppliers of micro inverters.
World leading central inverters suppliers are Inge-team, ABB, SMA,
Eltek, Sun-grow etc.
In India, research and development of inverter businesses are Su-khila
Power Electronics, APLAB, APD Global, lai-to infotech etc.

23.  Few of the major players operating in India inverter market
include Luminous Power Technologies Pvt . Ltd., V-Guard
Industries, Microtek International Private Limited, Su-Kam Power
Systems Limited, Exide Industries Limited, Amara Raja Batteries
Limited, Genus Innovation Limited, Arise India Limited etc.

24. CONCLUSION
Advanced inverter functionalities may lend significant improvement to
the stability, reliability, and efficiency, of the electric power distribution
system.
Distribution automation systems implemented by utilities will be
central to the integration of these functionalities, which require
protection, control, and communication to reach full efficacy.
Standards for interoperability and performance are being revised to
consider safe and reliable augmentation of inverter functionality to
support increased penetration of DER.