Low voltage ride-through of permanent magnet synchronous generator wind energy systems

Low Voltage Ride-Through (LVRT) capability is considered a critical feature that should be implemented within a Wind Energy Conversion System (WECS). The mismatch produced between the generated active power and the power delivered to the grid during any dip incidence at the Point of Common Coupling causes a dc link voltage rise, and increase in grid currents and generator speed-up. Failure to ride-through grid voltage dips would lead to converter failures within the WECS. This thesis focuses on enhancing LVRT capability of PMSG based WECS using magnetic amplifiers. LVRT techniques vary according to the turbine and utility grid variables. A survey of the state-of-art LVRT techniques highlighting the merits and demerits of each approach is carried out. A 1.5 MW wind turbine system is modelled, which includes the wind turbine, PMSG, and power converters. Also PMSG control, maximum power point extraction, and grid active and reactive power control are investigated. System performance is studied in compliance with British grid codes for active and reactive power sudden changes, frequency excursion, and grid voltage phase angle jump. The model is tested for LVRT capability under symmetrical network dips. Magnetic amplifiers have been used in various applications such as instrumentation, fault current limiting, and battery chargers. In this thesis, magnetic amplifiers are proposed as part of a LVRT capability enhancing technique. Two possible configurations are proposed; 3-phase and dc-side configurations. LVRT capability enhancement is investigated for the 1.5MW WECS using the two magnetic amplifier configurations. The 3-phase topology is able to reduce the dc link voltage rise; however, it causes an increase in the stored rotor inertia accompanied by an increase in generator speed. The dc-side magnetic amplifier topology is able to limit the dc-link voltage rise which in turn protects the power converters without affecting generator performance. In addition to simulations, a scaled prototype with the dc side magnetic amplifier configuration is used to verify the effectiveness and applicability of the proposed technique during steady state and transient behaviour under various operating conditions.Low Voltage Ride-Through (LVRT) capability is considered a critical feature that should be implemented within a Wind Energy Conversion System (WECS). The mismatch produced between the generated active power and the power delivered to the grid during any dip incidence at the Point of Common Coupling causes a dc link voltage rise, and increase in grid currents and generator speed-up. Failure to ride-through grid voltage dips would lead to converter failures within the WECS. This thesis focuses on enhancing LVRT capability of PMSG based WECS using magnetic amplifiers. LVRT techniques vary according to the turbine and utility grid variables. A survey of the state-of-art LVRT techniques highlighting the merits and demerits of each approach is carried out. A 1.5 MW wind turbine system is modelled, which includes the wind turbine, PMSG, and power converters. Also PMSG control, maximum power point extraction, and grid active and reactive power control are investigated. System performance is studied in compliance with British grid codes for active and reactive power sudden changes, frequency excursion, and grid voltage phase angle jump. The model is tested for LVRT capability under symmetrical network dips. Magnetic amplifiers have been used in various applications such as instrumentation, fault current limiting, and battery chargers. In this thesis, magnetic amplifiers are proposed as part of a LVRT capability enhancing technique. Two possible configurations are proposed; 3-phase and dc-side configurations. LVRT capability enhancement is investigated for the 1.5MW WECS using the two magnetic amplifier configurations. The 3-phase topology is able to reduce the dc link voltage rise; however, it causes an increase in the stored rotor inertia accompanied by an increase in generator speed. The dc-side magnetic amplifier topology is able to limit the dc-link voltage rise which in turn protects the power converters without affecting generator performance. In addition to simulations, a scaled prototype with the dc side magnetic amplifier configuration is used to verify the effectiveness and applicability of the proposed technique during steady state and transient behaviour under various operating conditions