Figure 3-1 shows a schematic diagram of a typical hybrid wind–diesel generation system. The main components of a hybrid wind–diesel power generation system are: wind turbine with associated controls, diesel engine; electrical generator with power electronic controllers (PEI), loads and bidirectional power electronic converter.
The wind turbine should be capable of capturing maximum energy by Maximum Power Point Tracking (MPPT) during low wind speed as well as high wind speed conditions. The tip speed ratio has to be brought to a particular value to achieve MPPT during low speed conditions. This can be done by adjusting the electromagnetic torque of the generator by employing ...view middle of the document...
The general practice is to use PMSG as a direct driven (gear-less) generator along with the wind turbine. Appropriate controls of the power electronic circuits are used to regulate the frequency and voltage and also to maintain the power factor of the generator at unity. The power electronic controllers also aid in achieving MPPT for varying wind velocity conditions.
3.1 Control strategies for wind–diesel generation systems
The wind–diesel hybrid systems, should meet the load demand even with varying wind velocities and sparingly use of diesel oil. This could be done by using power converters connected to the generator and a control strategy for controlling the power electronic converter. The different strategies employed along with a wind turbine are 1) DFIG with current-linked configuration with thyristorized rectifier and inverter for only for real power flow. 2) DFIG with voltage source converters are employed for both real and reactive power flow from the generator.
The following sections discuss the control schemes for different types of generators and also for the Bidirectional converters:
Permanent Magnet Synchronous Generator (PMSG) control with diode rectifier and chopper
The block diagram of a PMSG with a diode rectifier, thyristor based chopper and an inverter is shown in Fig. 3-2. The PMSG is coupled to the wind turbine whose variable frequency three phase output is rectified by the diode rectifier. As the wind velocity varies, the output voltage magnitude and frequency of the PMSG will change. This will result in variations in the diode rectifier output, which has to be maintained at a preset value for the DC link inverter input terminals. The sinusoidal pulse width modulated (SPWM) inverter converts this...