The control system also provides frequency droop control to handle unusual grid situations1. For example, in case of above-normal frequency, the controller will reduce the active power of the plant as illustrated in Figure 9 below. If the plant is under curtailment, the power can also be increased if the below-normal frequency is detected. Note that all the parameters illustrated in the figure are configurable and are shown here for illustrative purposes only.

Frequency Droop Function

Fault Ride-Through Capability

The ability to ride through specific low and high voltages or low- and high-frequency ranges is being designed effectively into all modern variable generators. Most utilityscale inverters have this capability. With proper design practices, the PV plant is engineered to ensure that all components besides inverters also have the ability to ride through short-term grid events.

Grid-Friendly PV Plants Are Operational Today

We have described a utility-scale “grid-friendly” PV power plant that incorporates advanced capabilities essential to supporting grid stability and reliability. It includes features such as voltage regulation, active power controls, ramp-rate controls, fault ride through, and frequency control. It also has the ability to minimize the impact of cloud cover. These capabilities provide the intrinsic benefits of reliable plant operation in the grid, which in turn results in additional plant yield and potential additional revenue. These “grid-friendly” capabilities, essential for increased penetration of large-scale PV plants into the electric grid, are operational and available today for utility-scale PV plants ranging from several megawatts to several hundred megawatts. These advanced plant features enable solar PV plants to behave more like conventional generators and actively contribute to grid reliability and stability, providing significant value to utilities and grid operators.

First Solar Operations Center in Mesa, Arizona, USA

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Mahesh Morjaria, VP, Product Management, First Solar, leads the development of First Solar’s grid integration capability for utility scale PV plants. His academic credits include B.Tech from IIT Bombay and Ph.D. from Cornell University in USA.

Dmitry Anichkov, Principal Engineer, Plant Controls, First Solar, is responsible for the development of the First Solar Real-Time Plant Control System. Dmitriy holds a MS degree from St. Petersburg Polytechnic.