Agus Naba

Fuzzy logic principles for wind speed estimation in wind energy conversion systems

Availability of wind speed information is of great importance for wind energy conversion systems (WECS) to extract maximum energy from wind. Most controllers in WECS employ anemometers to measure wind speed. To obtain adequate wind speed information a number of anemometers is required and needs to be installed properly surrounding wind turbine. This paper presents fuzzy logic principles for estimation of wind speed on the center of the wind turbine. The principles are inferred heuristically from a typical wind turbine power curve. The proposed principles have been simulated to estimate the wind speed on the center of the wind turbine during the WECS operation. The simulation results show that the wind speed could be well estimated under the wind speed variations.

Detection of resonant frequency of QCM by using Chirp Z-Transform

One of the main working principles of the Quartz Crystal Microbalance (QCM) is the relationship between the series of resonance frequency and mass change. Commonly, the sensor works as an oscillator system, where the resonant frequency is measured using a frequency counter. For a heavy damped condition, the oscillator stops to operate. This paper deals with the use of the spectral analysis approach to detect the QCM resonant frequency. The scenario is that the QCM sensor is subject to an input signal consisting of multi-frequency components; its frequency and magnitude of the output signal are then analyzed. The resonant frequency must be within the signal frequency input range and have the largest magnitude in the output of signal spectrum. Using FFT, there would be a heavy burden of computation in finding the resonant frequency since the high sampling frequency is larger than at least twice of the required resonant frequency of QCM; while the required bin size of the output signal spectrum is expected as small as possible. Thus, a large portion of unwanted frequencies is computed in FFT yet then ignored. This paper elaborates the use of the Chirp Z-Transform (CZT) to overcome this problem since its computation is less costly and can focus on a limited desired range of the frequency spectrum with smaller bin size. For a case study, A BVD model of QCM of the AT-cut quartz crystal type in HC49/U standard package was numerically simulated and tuned at 10 MHz series resonant frequency. Using the CZT method, a fair estimation of the QCMs resonant frequency was obtained from the spectral analysis of the output signal of QCM, which was subject to the narrow range of the multi frequency input signal adjusted at 40 MHz frequency as a sample.

Sensorless wind energy conversion system using fuzzy wind speed estimator

This paper presents a variable-speed wind energy conversion system (WECS) maximizing wind energy extraction using the tip-speed ratio (TSR) control method without direct measurement of wind speed. In the proposed WECS the wind speed is estimated by a fuzzy wind speed estimator. The wind speed estimates are used to determine the generator speed reference required by TSR control method. Simulated to control a squirrel-cage induction generator-based WECS, the proposed scheme has achieved high performance in maximizing the wind energy extraction despite using the estimated wind speed and the rough estimate of parameter required by the TSR control method. Its high performance was verified by the high power coefficients achieved throughout the simulation.