Wind farm layout for mitigating output power intermittency

Abstract

The placement of wind turbines (WTs) on a terrain to form a wind farm (WF) has significant impact on the total output power resulting from aggregating the WT powers at the point of common coupling (PCC). Output power intermittency is inherent in a WT as the wind speed invariably changes in intensity and direction. A combination of fast-acting energy storage (ES) and (relative) slow-acting spinning reserve may be used for smoothing the WF total output power when connected to the power grid. ES adds to the WF capital and operating costs. Thus, the main purpose of this paper is to present a simple methodology for evaluating the output power intermittency and ES requirements for a given WF layout. This methodology should minimize the number of WF layouts requiring more complex analysis before final siting. The methodology is illustrated by considering the spatial smoothing effects in three WF layouts having 16 WTs; namely, the straight-line, circular and square layouts. The total harmonic distortion (THD) of the total output power at the PCC when the wind direction varies from 0 to 90 degrees is used as a comparative figure of merit. For the direction with the worst THD, the amount of ES needed to limit the worst-case power ramp is calculated using a first-order approximation of the ES unit. The best layout is the one whose output power characteristic is least affected by changes in the wind direction, and thus, having the lowest THD and requiring the least amount of ES; this is the circular one for the analyzed layouts.