AE 868
Commercial Solar Electric Systems

Why Power Conditioning Units for PV?

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Since we learned the difference between DC power and AC power and their properties in the “Basics of Electricity” section in the class Orientation, we know for sure that the power coming from the source needs to be shaped to match the property of the load.

In this lesson, we will focus on how Power Conditioning Units (PCUs) are used and what the main types and configurations are that exist for these PCUs in the solar industry.

PCUs for PV systems

To know what a PCU is, we must first understand we need it for PV systems. All topics on the PV electrical output current, voltage, and power we discussed were in DC form. And since most appliances (fridge, lighting, heating, etc) need AC power, we need a device that can simply convert the DC electric power into an AC power. And that device is called an inverter. Furthermore, since most PV systems are connected to the utility grid, the solar power produced needs to be converted to AC form. This allows solar power to move in and out of the electricity grids we have today.

PCU vs Inverter

Many people use the term inverter as a device that converts DC into AC power. However, the inverter can perform many tasks beyond that. Thanks to the advancements in power electronics, it is common to have inverters that implement an MPPT mechanism before inverting the voltage, thus ensuring that the PV modules or arrays are operating at their maximum power. Furthermore, the inverter can include a battery charger, a DC to DC converter for voltage step-up and step-down, and a transformer for grid isolation and voltage step-up. As we can see, the basic DC to AC conversion that is referred to as inverter is better understood as the package and can be called a Power Conditioning Unit. It should be noted that the commonly used term for this device in the industry is “inverter.”

Note:

Power Conditioning Units are briefly discussed in EME 812 Lesson 6 PV Power Conditioning) and the operating principles, switching devices, and parameters are thoroughly discussed in the same lesson.