Solar inverters come in different sizes and shapes, as they are used for many different scenarios for renewable energy and power generation, but one thing is common to all of them. Their main purpose is to accept direct current (DC) from a series of photovoltaic (PV) solar panels and convert it to alternating current (AC) so that it can be fed to the power grid.
Microinverters may be used for single solar panels, and string inverters for a small series of panels, while central inverters are used in utility scale applications at higher voltages. In performing basic DC to AC conversion, central inverters are like string and microinverters, but that's where the similarity ends. Central inverters are typically provided in enclosures suitable for direct outdoor installation and include electrical switchgear, circuit protection, and monitoring. They usually include advanced features like power factor control, reactive power on demand and revenue metering. Central inverters also benefit from the intrinsic lower cost per kilowatt of a larger inverter, which — combined with the right feature set and high efficiency — often results in a lower total cost of ownership for power generation.
Ease of Serviceability
Serviceability is a concern with central inverters. While a smaller inverter can be swapped out on site, central inverters have traditionally had larger and harder to access components. To counter this, newer designs like the 890GT-S central inverter, with lightweight interchangeable modules improve field serviceability. With a good modular design, maintenance or repairs can be done in an hour or less — rather than several days. If all serviceable components can be accessed externally without requiring an operator to enter the inverter enclosure, safety is enhanced.
Smart features and user value
It’s no secret that more and more renewable energy sources are being connected to the grid. It is expected that 2014 will show 36% growth over 2013 in PV solar alone(1). This is great news for the environment, but most renewable sources do not have the constant, predictable output that the power grid needs to remain stable.
The increasing concern over grid power quality has led to a demand for “smart” central inverters that are grid friendly. Such units provide improved monitoring and fault detection, allowing them to be brought off line in a safe and controlled manner as needed, but grid friendliness does not stop there. In fact, some more sophisticated inverters can also act to improve grid quality. They do this by providing features like
- power factor control
- the ability to supply either real or reactive power on demand
- local voltage support
- controlled curtailment
These smart inverter features increase the inverter's value to the owner as a dispatchable asset.
Inside a central solar inverter
This video offers a look inside Parker's 890GT-S Central Solar Inverter, with particular attention to its modular construction and serviceability.
(1) SEIA/GTM Research
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