1.0 BASIC PRINCIPLE OF SOLAR INVERTER
A solar inverter, or PV inverter, converts the variable direct current (DC) output of a
photovoltaic (PV) solar panel into a utility frequency alternating current (AC) that can be fed into a commercial electrical grid or used by a local, off-grid electrical network. It is a critical component in a photovoltaic system, allowing the use of ordinary commercial appliances. Solar inverters have special functions adapted for use with photovoltaic arrays, including maximum power point tracking and anti-islanding protection
1.1 NEED OF SOLAR INVERTER
There are two types of sources for electrical power generation. One is conventional and other is non- conventional. Today to generate most of electrical power conventional sources like coal, gas, nuclear power generators are used. Some of conventional source are polluted the environment to generate the electricity. And nuclear energy is not much preferable because of its harmful radiation effect on the mankind. After some of ten years conventional sources will
not sufficient enough to fulfill the requirements of the mankind. So some of the electrical power should be generated by non-conventional energy sources like solar, wind .With the continuously reducing the cost of PV power generation and the further intensification of energy
crisis, PV power generation technology obtains more and more application.
Conventionally, there are two ways in which electrical power is transmitted. Direct current (DC) comes from a source of constant voltage and is suited to short-range or device level transmission. Alternating current (AC) power consists of a sinusoidal voltage source in which
a continuously changing voltage (and current) can be used to employ magnetic components. Long distance electrical transmission favors AC power, since the voltage can be boosted easily with the use of transformers. By boosting the voltage, less current is needed to deliver a given
amount of power to a load, reducing the resistive loss through conductors.
The adoption of AC power has created a trend where most devices adapt AC power from an outlet into DC power for use by the device. However, AC power is not always available and the need for mobility and simplicity has given batteries an advantage in portable power. Thus, for portable AC power, inverters are needed. Inverters take a DC voltage from a battery or a solar panel as input, and convert it into an AC voltage output.
1.2 TYPES OF SOLAR INVERTER
Solar inverters may be classified into three broad types.
1. Stand Alone Inverters
2. Grid Tie Inverters
3. Battery Backup Inverters
1.3 STAND ALONE INVERTERS
Stand-alone inverters, used in isolated systems where the inverter draws its DC energy from batteries charged by photovoltaic arrays. Many stand-alone inverters also incorporate integral battery chargers to replenish the battery from an AC source, when available. Normally
these do not interface in any way with the utility grid, and as such, are not required to have antiislanding protection.
1.4 GRID TIE INVERTERS
Grid-tie inverters, which match phase with a utility-supplied sine wave. Grid-tie inverters are designed to shut down automatically upon loss of utility supply, for safety reasons. They do not provide backup power during utility outages.
1.5 BATTERY BACKUP INVERTERS
Battery backup inverters, are special inverters which are designed to draw energy from a battery, manage the battery charge via an onboard charger, and export excess energy to the utility grid. These inverters are capable of supplying AC energy to selected loads during a utility
outage, and are required to have anti-islanding protection.
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