advertisement
ENERCON E-40 Operating Instructions
Page 13 of 96
Above the rated wind speed the power output is constantly kept at rated power by adjusting the blade angles accordingly. The necessary adjustments are determined by evaluating the measured rotational speed and acceleration data.
If wind speeds of 25 m/s on an average during one minute or 30 m/s on an average during 15 seconds are exceeded, the turbine is stopped. It is only started up again if the wind speed keeps below 25 m/s continuously for at least 15 minutes.
Even when the turbine is stopped, the rotor is allowed to idle at low speed. For sites with extrem strong wind speeds, it is possible to extend the operation beyond the
25 m/s range (see chapter 3.9 for details).
The yaw control of the E-40 nacelle is operating at all wind speeds above 1.8 m/s
(which is below the start-up wind speed). The wind vane at hub height continuously detects the wind direction. If the 1-min-average deviation of the nacelle direction compared to the measured wind direction is greater than 8°, the nacelle will be repositioned by means of the yaw motors. The yaw motion will be monitored by counting the rotations of the yaw motor and by checking the yaw time for plausibility.
In case the machine is parked manually or via the control system, the blades are pitched down so that the effective surface of attack for the wind is reduced and the
E-40 slowly turns to a stand-still.
1.5.5 Grid Management
The grid management system converts the current generated by the E-40 generator into AC current by means of rectifiers and inverters according to the requirements and standards given by the utilities and feeds it into the grid via a transformer.
The grid management unit is elastically coupled with the E-40 generator via a
D.C. link. Figuratively speaking, the rotor of the wind energy converter is connected to the electric grid via a soft rubber band. This "elastic" coupling allows the electronics to balance low frequency power fluctuation so that the power output of the E-
40 can be controlled very precisely between 5 kW and 500 kW and no relevant flicker
1
coefficients are occuring. This combination of technologies allows a gridparallel operation without complicated grid connection conditions. Various certificates issued by independent institutes are confirming this.
Depending on the phase angle of the voltage in the grid and the power output by the generator, a reference value is generated for the current to be fed to the grid.
According to this reference value, the rectified current supplied by the generator is converted into alternating current and fed into the grid. This reference value is compared to the actual current (actual value) every 100 s and corrected if necessary.
The shape of the current supplied is sinusoidal and largely without disturbing harmonics. A filter reduces the harmonics even further, which means that the system easily complies with the admissible limit values.
The permissible operating range for grid-parallel operation is limited by the minimum and maximum grid voltage given by the respective utility. These two values
(under- and overvoltage) can be preset separately as limit values for the E-40. In addition to that, minimum and maximum values for the frequency can be preset.
1
Flicker are low-frequency voltage fluctuations. In front of the tower of a wind energy converter a lee is formed as the rotor blades pass the tower, which with most WECs leads to an irregular power output and therefore voltage fluctuations. In the vicinity of a WEC, flicker can be noticed by a slight unsteadiness in the lighting.
Short description of the E-40
ENERCON E-40 Operating Instructions
Page 14 of 96
The E-40 immediately disconnects itself from the grid if these preset limit values are not being kept. As there are no compensating capacitors, voltage and frequency will collapse and the E-40 inverter discouples itself from the grid within a very short time. Therefore even short-term current spikes are not occuring.
In addition to that, the E-40 can operate in the so-called "grid voltage-dependent power feeding" mode (optional). In this option, the grid voltage is constantly measurend and monitored. In case the voltage increases, e.g. due to lack of load during the night, the power output of the E-40 will be decreased immediately.
Short description of the E-40
advertisement
