Solar inverter

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A solar inverter , or converter or PV inverter , converts the direct current output (DC) from the photovoltaic solar panel (PV) to the alternating current utility frequency (AC) that can be incorporated into a commercial power grid or used by a local power grid outside the network. This is a critical balance of the system (BOS) -component in a photovoltaic system, enabling the use of regular air-conditioning equipment. Solar power inverters have special functions tailored for use with photovoltaic arrays, including maximum power point tracking and anti-island protection.

Video Solar inverter

Classification

Solar inverters can be classified into three broad types:

1. Stand-alone inverter , used in isolated systems in which the inverter draws its DC energy from a battery filled by a photovoltaic array. Many stand-alone inverters also incorporate an integral charger to recharge the battery from an AC source, if available. Usually this does not interface in any way with network utilities, and as such, is not required to have anti-island protection.
2. Grid-tie inverter , which matches the phase with the sine wave provided by the utility. Grid-tie inverters are designed to shut down automatically after a loss of utility supplies, due to security reasons. They do not provide backup power during a power outage.
3. Battery backup inverter , is a special inverter designed to pull energy from a battery, manage battery charging through an onboard charger, and export excess energy to the utility grille. This inverter is capable of supplying AC energy to the selected load during a power outage, and must have anti-island protection.

Maps Solar inverter

Maximum power point tracking

The solar inverter uses maximum power point tracking (MPPT) to obtain the maximum possible power from the PV array. Solar cells have a complex relationship between solar irradiation, temperature and total resistance resulting in a non-linear output efficiency known as the I-V curve. It is the purpose of the MPPT system to sample the output of the cell and determine the resistance (load) to obtain maximum power for any given environmental conditions.

The fill factor, better known as the abbreviation FF , is a parameter which, together with the open circuit voltage (V _oc ) and short circuit current (I _sc ) from the panel, determining the maximum power of the solar cell. The fill factor is defined as the maximum power ratio of the solar cells for the product V _oc and I _sc .

There are three main types of MPPT algorithms: perturb-and-observe, incremental conductance and constant voltage. The first two methods are often referred to as the hill climb method; they depend on the power curve plotted against the voltage rising to the left of the maximum power point, and falling to the right.

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Solar micro inverter

Solar micro-inverter is an inverter designed to operate with a single PV module. The micro inverter converts the direct current output from each panel into alternating current. The design allows parallel connections of some independent units in a modular way.

The advantages of micro-inverters include single panel power optimization, independent operation of individual panels, plug-and play installation, improved installation and fire safety, minimizing costs with system design and stock minimization.

A 2011 study at Appalachian State University reported that an individual integrated inverter arrangement generates about 20% more power in non-shaded conditions and 27% more power in a shaded state than a string-connected setting using an inverter. Both settings use identical solar panels.

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Grid bonded solar inverter

The solar grid-tie inverter is designed to quickly disconnect from the grid if the power grid goes down. This is a NEC requirement that ensures that in the event of a power outage, the grid fastening inverter will die to prevent the energy it generates from harming any lane worker sent to repair the power grid.

Grid-tie inverters are available on the market today using a number of different technologies. The inverter may use newer high-frequency transformers, conventional low-frequency transformers, or without a transformer. Instead of converting direct current directly to 120 or 240 volts AC, a high-frequency transformer uses a computerized multi-step process that involves the conversion of power to high-frequency AC and then back to DC and then to the final AC output voltage.

Historically, there have been concerns about having a transformer power supply system to the public utility network. The concern stems from the fact that there is a lack of galvanic isolation between DC and AC circuits, which can allow the passage of dangerous DC errors to the AC side. Since 2005, NEC NFPA allows a non-transformer (or non-galvanized) inverter. VDE 0126-1-1 and IEC 6210 have also been changed to allow and establish the necessary security mechanisms for the system. In particular, residual or ground current detection is used to detect possible disturbance conditions. Also an insulation test is performed to ensure DC separation into AC.

Many solar inverters are designed to be connected to utility networks, and will not operate when they do not detect the presence of the grid. They contain special circuits to suit precisely the voltage, frequency and phase of the grid.

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Inverter solar pumping

The advanced solar pumping inverter converts the DC voltage from the solar arrangement into AC voltage to drive submersible pumps directly without the need for batteries or other energy storage devices. By utilizing MPPT (tracking of maximum power point), the solar pumping inverter regulates the output frequency to control the pump speed to save the pump motor from damage.

Solar pumping inverters usually have multiple ports to allow DC current input generated by PV arrays, one port to allow AC voltage output, and a further port for inputs from water level sensors.

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Market

By 2014, conversion efficiency for state-of-the-art solar converters is over 98 percent. While string inverters are used in housing for medium-sized commercial PV systems, central inverters include commercial markets and large utility scales. The market share for central and string inverters is about 50 percent and 48 percent, respectively, leaving less than 2 percent to micro-inverters.

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See also

• Inverter (power)
• Off-the-grid
• Load controllers

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References

Source of the article : Wikipedia