What are Grid-Tied Solar Inverters?

Inverters are the most common electrical appliances that accompany people in their daily lives. In fact, inverters can be found everywhere from homes to commercial airliners and even outer space.

Inverters offer a wide range of versatile functions such as converting high voltages to low voltages or low currents to high currents. However, these projects generally require high currents or high voltages, which are difficult for people to access. Hence, an inverter is considered useful if it can provide low current and low voltage outputs, one of which is a grid-tied solar inverter.

What Is A Grid-Tied Solar Inverter?

A grid tied solar inverter is an electrical device that changes direct current (DC) into alternating current (AC) by using energy from the sun. The solar inverter then sends this alternating current to homes and buildings where it can be used as electricity.

Most people are familiar with grid-tied solar systems, but how exactly does this process work?

Solar inverters are among the most popular renewable energy inverters, and they are often paired with photovoltaic panels to create a solar power system which works together to convert the sun’s energy into usable electricity. Solar inverters have become incredibly efficient over time, making them more affordable for consumers. Most grid-tied solar inverters are connected to central battery systems that store any unused energy for future use.

A grid-tied solar inverter can be connected to the power grid through an electrical switch, which allows electricity generated by the solar panels to be sent onto the power grid when there is not enough in the batteries.

Electricity that is generated but never used goes back into the grid through an electrical meter and the customer is then charged and credited for their usage.

Types Of Grid-Tied Solar Inverters

Inverter technology for grid-tied energy applications can be divided into three main types:

String Inverters

The string inverters, also known as central inverters, series string inverters, or multilevel inverters,  is commonly used in both stand-alone and utility interactive photovoltaic systems when a large number of solar modules, typically 16 or more, in a series-wired group are expected to be in near-constant use in a system.

String inverters have the ability to work with older polycrystalline modules that are no longer efficient enough to be used in grid-connected PV systems, especially in locations where snow or debris may block the sun for extended periods of time.

String inverters are available as central inverters or as hybrid inverters with accompanying power optimizers. Central inverter technology is also known as a multi-bus inverter system. This is a fully digitalized inverter with a large number of string inputs and one or more high-power DC outputs.

The individual solar modules are connected in series with the use of special connectors, also known as an MC4 connector, at each end of the module bank. The output from all these modules is then fed over a large busbar system to the central inverter.

Multi-module Inverters

Multi-module inverters, also known as parallel inverters or microinverters, work with smaller groups of solar modules and include power optimizers (also called Maximum Power Point Trackers, or MPPT) with each module in the system. The modules are connected in parallel with the use of special junction boxes or prefabricated cable harnesses, and each output is then fed over a large busbar to the inverter.

Power Optimizers

These are also known as Maximum Power Point Trackers (MPPT), charge controllers, DC-AC Inverters, or micro-inverters.

These inverters are usually used in smaller systems, and their function is to match the voltage and current from each solar panel (module) as closely as possible to the line voltage and current, which allows for maximum power extraction from each module.

This matching voltage and current also maximizes overall system efficiency because electricity can be drawn from the modules at their most efficient operating point.

Why Should You Care About The Right Grid-Tied Solar Inverter?

In a grid-tied system, all energy from the solar panels must be converted and sent through the inverter before it can be fed into the grid. Therefore, a grid-tied solar inverter is arguably one of the most critical components in your solar power system.

Therefore, here are three questions to ask yourself when purchasing a grid-tied solar inverter for your system:

  1. How much can you afford to spend on an inverter?

Grid-tied solar inverters come in all shapes and sizes, ranging from less than $200 for a very small system to more than $20,000 for large commercial systems. High power inverter which can go up to 100kW uses high voltage expensive components like IGBT, and hence the higher costs.

  1. How much energy is my system generating?

The size of your solar panels combined with the amount of power you would like to generate determines how big your grid-tied solar inverter needs to be. Home-based single phase solar inverters can range from 1 to 10kW while commercial-based three phase inverters can go up to as high as 100kW.

  1. What kind of environmental and safety conditions will my inverter be facing?

Solar power systems have no moving parts and are built to withstand some of the harshest weather conditions on earth, but there are certain features that can increase health and life expectancy of your inverter in certain climates.

For example, solar inverters placed in extremely hot or cold conditions should have heat sinks to dissipate heat when it’s hot and active cooling fans when it’s cold. Solar inverters placed in humid environments should also have features that protect them from humidity, such as having tight seals around the electrical panels or operating high voltage ranges.

Electrically, to protect the system and the safety of the users, renewable energy inverters should be galvanic isolated from the high voltages using transformers or optocouplers.

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