1. ADVANCEMENTS IN INVERTER
TECHNOLOGY
P. BHANU TEJA
B100338EE
NATIONAL INSTITUTE OF TECHNOLOGY CALICUT

2. CONTENTS
1.
INTRODUCTION
2.
TECHNICAL BACKGROUND ON INVERTERS
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

Inverters are power electronics-based devices which
convert direct current (DC) to alternating current (AC).

This function is fundamental to the integration of power
from many sources into the distribution system.

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.

Beyond this fundamental purpose, there exist a range of
complementary, technologically viable, and demonstrated
functions that an inverter may be designed to provide.

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:

Fundamentally, an inverter is a device which converts
a direct current (DC) input to an alternating current
(AC) output.

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.

6. In distribution applications, these devices produce a
sinusoidal waveform of the appropriate frequency.
 Inverters may be

1.
2.
Stand alone(off-grid): supply generated or stored power
solely to connected loads.
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:
 Inverters are designed to optimize transfer of power from
DER to load, often through a technique called Maximum
Power Point Tracking (MPPT).
 Based on computation of the ideal equivalent resistance
from measurements of current, voltage, and the respective
rates of change.
2.Voltage Conversion:
 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 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
 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
 An inverter may enable the integration of a battery or
other energy storage device with a distributed generator.

9. 6.Anti-islanding protection:

Normally, grid-tied inverters will shut off if they do not detect
the presence of the utility grid.

There are load circuits in the electrical system that happen
to resonate at the frequency of the utility grid.

The inverter may be fooled into thinking that the grid is still
active even after it had been shut down. This is called
islanding.

An inverter designed for grid-tie operation will have antiislanding 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
Advanced Inverter Key Concepts
 An advanced inverter has the capacity
1.
2.
3.

To supply or absorb reactive power
To control and modulate frequency and voltage, and
Voltage and frequency ride-through.
Capacitors could be installed to either supply or absorb reactive
power. Practical limitations include:
1.
2.

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.
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. 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:

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.

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.

Advanced inverters, combined with existing FACTS
infrastructure and control Systems.

14. 
A capability curve prescribes the output reactive power, which
is diminished at lower voltage levels and at higher output
active power.

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:
 significant potential to increase efficiency and flexibility of
power distribution.
 providing sufficient resolution in controlling reactive power.
 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.

The controlling algorithm will implement a
response, such as an increase in power in response
to a low voltage.

17. 
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 or injury.

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

19. Challenges:
1.
There is ongoing work to develop interoperability
standards for DER devices including inverters and
inverter controllers.
Therefore, limitations are there to how much these
advanced functionalities can be used autonomously
without adversely impacting the grid or other
customers’ equipment
2.
Different safety requirements and standards are to be
implemented for residential and small commercial
applications.

20. 3.
EPRI (Electric Power Research Institute)
conducted a study, indicating that over 69% of
downtime events are caused by the PV inverters.
The main contributors to these failures were
software bugs and material failures, which indicates
a need for significant refining of the inverter
technologies being deployed.

21. 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.

22. STRING INVERTER
MICRO INVERTER
PROS:
 lower initial cost per peak
watt price.
 easier to install, maintain.
CONS:
 cost more per peak
watt.
 difficult to install,
maintain.
CONS:
 problems with one panel
are felt across the entire
string.
 difficult to fix.
 takes more space.
PROS:
 one panel won’t impact
other.
 easy to fix.
 takes less space.

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

24. 
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.

25. MARKET

Enphase is one of leading suppliers of micro inverters.

World leading central inverters suppliers are
Ingeteam, ABB, SMA, Eltek, Sungrow etc.

In India, research and development of inverter businesses are
Sukhila Power Electronics, APLAB, APD Global, laito infotech etc.

26. 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.