Outline • Introduction • PMSG • DFIG • IG • SG • Conclusion
Introduction This paper provides a comprehensive review of past and present converter topologies applicable to PMSG, IG, SG and DFIG. The many different generator–converter combinations are compared on the basis of topology, cost, efficiency, and control complexity.
PMSG • Thyristor supply-side inverter • Hard-switching supply-side inverter • Intermediate DC/DC converter stage
Thyristor supply-side inverter • Advantages : lower device cost and higher available power rating than hard-switched inverters. • Disadvantages : need for an active compensator for the reactive power demand and harmonic distortion created
Hard-switching supply-side inverter Control methods: • Power mapping technique • Using a derivative control on the stator frequency (55–61%) • MPPT with wind prediction control (56–63%))
Intermediate DC/DC converter stage • Maintains appropriate inverter-side DC-voltage • Allows for selective harmonic elimination • Inverter no longer needs to control DC-voltage, and has more flexible control.
DFIG • Static Kramer drive methods • Back-to-back PWM converters • Matrix converter
Static Kramer drive This converter provides a suitable compromise between conversion efficiency and torque oscillation smoothing.
Back-to-back PWM converters Control methods: • Vector control of rotor and supply side space vector modulation • PWM MPPT space vector control
Matrix converter • Advantages : The converter requires no bulky energy storage or DC-link and control is performed on just one converter.
IG The advantages of fuzzy logic control are parameter insensitivity, fast convergence and acceptance of noisy and inaccurate signals.
SG Small wind energy conversion system Large system SG SG
Conclusion • PMSG offer the highest efficiency and are self-exciting machines and are therefore suitable for small-scale designs. • DFIG offers a vast reduction in converter size however they are susceptible to grid disturbances since their stator windings are directly connected to the grid. • SG allows for independent control of both real and reactive power • IG are relatively inexpensive and robust however, they require external excitation circuitry and reactive power from the grid.
Conclusion • The cost of the overall system increases as the complexityof the power electronic converter increases . • The complexity of the controller design also affects cost; for example, the use of MPPT techniques would cost more than a simple lookup table method.