ABSTRACT
Because the generator rotates at the speed of the blades, the frequency at the terminals of the generator is not constant and is changing with wind speed. Therefore, the generator cannot be directly coupled to the grid. Instead, converters are used between the generator and the grid to match the frequency of the grid. One of the designs is shown in Figure 11.2. The converter is called “full converter” as it processes the full amount of power produced by the generator. It consists of three circuits: rectifier bridge, buck-boost
converter, and dc/ac converter. The rectifier bridge converts the variable frequency terminal voltage Va into dc voltage Vave. The buck-boost converter adjusts the voltage of the dc bus Vdc. The dc/ac converter inverts the dc voltage Vdc into ac voltage Vout with frequency that matches the grid frequency. The magnitude and frequency of Vout is controlled by the pulse width modulation (PWM) technique discussed in Chapter 5. The transformer is used to step up the output voltage of the converter to the grid voltage.
