Make in India is one of the major policy initiatives of Prime Minister Narendra
Modi which covers almost every sector. Solar, as a part of renewable energy, is
one of the focused sectors which is expected to grow to 100GW by 2022. Increasing
demand for clean energy along with government incentives has expanded the solar
market, but the high initial cost of photovoltaic (PV) systems is still inhibiting
its widespread adoption.
A PV system typically consists of the PV array, inverter and other protection systems
that form part of the balance of systems. In the PV array, individual solar cells
that produce DC power are grouped together into a solar panel or module. Several
of these are then grouped together to form a PV array.
The DC power from the solar array needs to be converted to alternating current,
or AC power, before it can be connected to the utility grid. Thus, inverter becomes
an integral part of any solar power system. It plays a key role in the utilisation
of solar energy for the end user by feeding it to the existing grid. It converts
solar power direct current (DC) to alternating current (AC) through a delicate electrical
switching process. Advancements in inverter technologies are making them smarter
and more critical to the success of solar power generation. There are majorly three
different types of grid-tied inverters available - micro, string and central. Each
inverter has its own advantages and disadvantages based on the application.
Traditionally, choosing an inverter for a commercial system would begin with determining
the PV system size. A central inverter is used to convert the entire PV array into
grid-synced AC. This inverter can be placed indoors or be outside with some protection.
Solar installations of megawatt scale typically have a large central inverter that
takes the direct current generated by a group of panels and converts it into AC
for the electrical grid.
The industry standard string inverter solar system comprises a number of solar panels
linked together in series forming strings. The voltage and current of all panels
is combined into a single output that is fed into the inverter. The problem with
this is that any drop in current or voltage within one panel affects the entire
string; a decline in the performance of one solar panel and will automatically hamper
the performance across the entire string which is also known as Miss-Match losses.
Micro inverters are able to address this issue since they are electrically connected
in parallel rather than in series. What's more, they optimise the power conversion
process by adapting the system to changing environmental conditions (shading, dust
and debris, non-uniform temperatures, sub-optimal irradiance angles etc.). So if
one panel suffers from environmental interference or a panel failure, it does not
affect the entire array. The electric power from several micro-inverters is combined
and fed into an electrical grid. These small sized inverters have some distinct
advantages over central inverters and the string inverters. Besides reducing the
miss-match losses, each micro-inverter obtains optimum power by performing maximum
power point tracking for its connected panel, thus improving efficiency and reliability.
One of biggest advantages of using micro-inverters is that there is no limitation
to sizing the plant capacity. To increase the size of a solar plant, you can simply
add single or any number of panels of different wattages and even different manufacturers
in parallel to the existing power plant. It even gives the liberty to curtail the
start-up cost and can be expanded in the later stages. Other advantages of Micro-inverters:
Other advantages of Micro-inverters:
- Micro-inverter is easy and faster to install as compared to traditional inverters.
It reduces the wiring time and removes the need for DC switching points.
- The installation of Micro-inverters is not limited by string design, marginal designs,
co-planarity, and miss-matched modules.
- MPPT (expand) is applied to each individual panel which yields in 5-25% increase
in power as compared to systems using string inverters
- It is possible to monitor each panel and inverter performance which helps in maintenance.
The life of micro inverters is more than traditional sting inverters as they are
not exposed to as high power and heat loads as central inverter.
- Micro-inverters typically come with a warranty of 20-25 years - 10-15 years longer
than central inverters. With minimal budget, one can start implementation as it
is flexible and scalable. One can add new solar panels as and when required.
With a micro inverter, it becomes an AC module system, and the installer's crew
or the maintenance personnel are not exposed to high voltage DC which is highly
dangerous and unsafe to work with, even in terms of operation and maintenance.
In traditional string inverter, DC bus voltage is as high as 600V DC or 1000V DC
so while installation and performing maintenance, a user has to de-energize the
AC distribution which results in service interruption. In case of fire, shutting
off power with circuit breakers only shuts off the centre inverter and not the DC
voltage generated from the panel. As a result, it is dangerous to spray water as
it can actually make a fire worse.
Major Drawbacks of Micro inverters compared to String Inverters
Primary disadvantages of micro inverters are that they have a higher initial cost
per peak watt than a central inverter, and second, as they are located near the
panel, they may be harder to reach and maintain. But these problems could be overlooked
by their higher durability, efficiency and ease of installation.
Micro inverters are placed individually to the rack below each panel, due to which
these are exposed to hottest part of system and could lead to problems in case of
insolation areas. Typically, they are used for smaller size systems. For large scale
power plants, it becomes economically and technically difficult to implement.
Looking at the large number of advantages, many inverter manufacturers have engaged
in research and development to overcome the challenges in the implementation of
Micro-inverters. In the near future, the market would provide AC rated power generating
solar modules with plug and play mechanisms to ease the clean energy requirements.
i-Vision max Solar SCADA for PV Plants
Today monitoring and performance analysis of solar PV plants has become extremely
critical due to the increasing cost of operation and maintenance as well as reducing
yield due to performance degradation during the lifecycle of the plant equipment.
This means that the use of centralised monitoring & control system is essential
to ensure high performance, low downtime, and fault detection of a solar PV power
plant during the entire lifecycle.
Keeping in mind the need of the industry, C&A has developed a solution for
Solar PV - i-Vision max Solar ® an advanced, ideal best
in class monitoring & control tool to manage your solar photovoltaic plant. It enables
centralized control & operation from a central location and incorporates all the
basic features available in a high-end Generation SCADA system and primarily used
at:
- Local level: Best in class to manage your solar photovoltaic plant locally
- Remote level: Enables clear overview of complete plant for remote monitoring
It offers
- Open architecture allows easy upgrading to new technology Enables Plant parameter
Monitoring, Electrical Control in a plant
- Weather Data - Solar Irradiance, Wind Speed, Wind Direction, Ambient Temperature,
Relative humidity, Particulate Meter & Rain Gauge
- Formulas and rules to the parameters measured to obtain efficiencies, trends, performance
ratios and estimation of losses at the solar plant
Communication health monitoring
Basic features
- Electrical Network Monitoring & Control
- Inverter & String Performance Monitoring
- Tracking Control
- Alarms & Events logging
- Trends & Reporting
- Email and SMS Alert
- Secured User Administration
- Dashboard / KPIs of the Solar Photovoltaic Plant in real time
Basic features
- Asset Management
- Security Surveillance
- Yield Reports
- Performance Ratios O&M Calenders