Solar Electricity: Contributing to Grid Stability

Dr. Mahesh Morjaria, Vice President PV Systems at First Solar

Governments, utility companies and private enterprises around the world have rapidly been embracing solar energy and for good reason: Solar energy is not only clean and renewable; it has already become the cheapest source of energy in some countries.

With the growing number of photovoltaic power plant installations, there is concern that renewable energy sources can destabilize the electrical grid, which was typically designed and built decades ago on the principle of a centralized energy system of massive power plants transmitting electricity across long distances to the load packets.

A large part of the challenge arises from the variability of renewable energy generators: solar power plants need sunlight to function and passing clouds could impact their ability to consistently generate electricity and maintain the stability of the grid. Conversely, an unusually sunny day in a region with a large volume of distributed generators, during a low demand period, could lead to excess electricity generation, which in turn would impact stability.

Utility-scale PV plants with “grid-friendly” features such as voltage regulation, active power controls, ramp rate controls, fault ride-through, frequency droop control and others have however alleviated these concerns. The viability of PV plants to provide important ancillary services to the grid was recently demonstrated in a test conducted with NREL and CAISO on a 300MW utility-scale PV plant.  The results showed that the PV plant value can be extended to provide services such as spinning reserves, load following, ramping, frequency response, variability smoothing and frequency regulation. The results showed that a PV plant can regulate to 4-second Automated Generator Control (AGC) signal 24-30 points more accurately than even fast gas turbines.

 

Click here to view the final report, and fact sheets on smart inverter technology and the test highlights.