solar inverter

Topics: Photovoltaics, Solar energy, Solar power Pages: 20 (5865 words) Published: January 5, 2014
A solar inverter, or PV inverter, converts the variable direct current (DC) output of a photovoltaic (PV) solar panel into a utility frequencyalternating 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. Contents

1 Classification
2 Maximum power point tracking
3 Anti-islanding protection
4 Solar micro-inverters
5 Grid tied solar inverters
6 Solar charge controller
7 Solar pumping inverters
8 Inverter failure
8.1 Capacitor failure
8.2 Inverter bridge failure
8.3 Electro-mechanical wear
9 See also
10 References
11 External links

Simplified schematics of a grid-connected residential photovoltaic power system[1] Solar inverters may be classified into three broad types:[citation needed] 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 anti-islanding protection. 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. 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. Maximum power point tracking[edit]

Main article: Maximum power point tracker
Solar inverters use maximum power point tracking (MPPT) to get the maximum possible power from the PV array.[2] Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces 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 cells and determine a resistance (load) to obtain maximum power for any given environmental conditions.[3] The fill factor, more commonly known by its abbreviation FF, is a parameter which, in conjunction with the open circuit voltage and short circuit current of the panel, determines the maximum power from a solar cell. Fill factor is defined as the ratio of the maximum power from the solar cell to the product of Voc and Isc.[4] There are three main types of MPPT algorithms: perturb-and-observe, incremental conductance and constant voltage.[5] The first two methods are often referred to as hill climbing methods; they rely on the curve of power plotted against voltage rising to the left of the maximum power point, and falling on the right.[6] Anti-islanding protection[edit]

Main article: Islanding
In the event of a power failure on the grid, it is generally required that any grid-tie inverters attached to the grid turn off in a short period of time. This prevents the inverters from continuing to feed power into small sections of the grid, known as "islands". Powered islands present a risk to workers who may expect the area to be unpowered, but equally important is the issue that without a grid signal to synchronize to, the power output of the inverters may drift from the tolerances required by customer equipment connected within the island. Detecting the presence or lack of a grid source would appear to be simple, and in the case of a single inverter in any given possible physical island (between disconnects...

References: 100–300 EJ[10]
Primary energy use (2010)
539 EJ[11]
Electricity (2010)
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