Solar Photovoltaic Growing Pains

In today’s guest post, Emerson’s Jim Cushman, a member of the Power & Water Solutions team, describes the challenges utilities and independent system operators (ISOs) face in regulating power on the grid with the increasing number of solar photovoltaic (PV) alternative energy-based systems being installed in commercial and residential properties.

The solar photovoltaic market continues to expand as the price of solar panels drops and the cost of construction goes down. Residential and commercial markets never were a concern to grid stability, since most of these projects were less than 1MW and were installed on the grid with no controls. Utilities clearly recognize the need to control 20MW, 50MW, 170MW and beyond, since they can have major impact on the grid if they go off or online without coordination to traditional power generation sources. With distributed solar PV generation, utilities are now concerned with large amounts of small-scale projects and see the need for controls.

Southern California Edison’s 250MW Rooftop Program is a good example of this concern. The picture in this article shows a 1MW rooftop installation in Southern California. It is simple to understand that the growing number of 1MW Plants (as many as 250 currently exist) could have significant impact on the grid if they drop off line or power on when other generation is meeting the current load or electrical demand.

Control is not difficult in these plants, but is an important factor to the utilities and ISOs. Volt-ampere reactive (var) control, which is the ability to regulate power on the grid, is very important to utilities and has become a requirement for the SCADA systems being installed in these plants. Inverters in these solar PV plants can absorb reactive power from the grid thus allowing utilities to produce and get paid for the real power they produce.

As solar PV plants continue to fill the landscape, utilities and independent power producers will require the need to control the output of their plants and avoid the result of an unstable grid of ad hoc plants being connected with no curtailment capability.



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