High-power medium-voltage three-phase ac–dc buck–boost converter for wind energy conversion systems

Abstract

This paper proposes three topologies of single-stage three-phase ac-dc buck-boost converters suitable for medium-voltage and high-power wind energy conversion systems (WECS). The proposed converters draw sinusoidal input currents with nearly unity power factor from wind generators over wide range of ac voltages and frequencies. The proposed converters reduce the voltage and current stresses on the self-commutated switching device compared to existing solutions; thus, promising for new generation of relatively cheap WECSs. The proposed converters operate in Discontinuous Condition Mode (DCM), with their ac terminals connected to three-phase generator with open ended windings, or to ac supply using three single-phase transformers with isolated windings at converter side. The validity of the proposed converters and its detailed theoretical analysis and discussions are confirmed using PSCAD/EMTDC simulations, and further corroborated by experimentations, considering different operating conditions. Nomenclature δ: Duty cycle. δc: Critical duty cycle ωg: Generator speed ωopt: Optimal speed CCM: Continuous conduction mode DCM: Dissentious conduction modes DBD1 to DBD3 : Sub-converter blocking diodes DFW1 to DFW3 : Sub-converter freewheeling diodes fs : Switching frequency f : Supply fundamental frequency Ic : dc-link capacitor current Ic_avr : Average dc-side capacitor current Ip : Peak fundamental supply current I * p : Reference peak fundamental supply current Ldc1 to Ldc3 : dc-link inductances Ldc_slc :Selected dc-link inductance for given circuit operation ILa, ILb , and ILc : dc-link inductance current ILmax_a, ILmax_b, and ILmax_c : Peak dc inductor currents is1 to is6 : Currents in the switches of the sub-converters ira ,irb ,and irc : Fundamental component of the pre-filter input current ir_rms : Pre-filter input root mean square current MPPT :Maximum power point tracking PI : Proportional integral R : Load resistance txa, txb and txc Deplete times of the energy stored in the dc-link inductors Ts : Switching period Vdc : dc link voltage Vm : Peak of phase voltage vs(a),vs(b), and vs(c) : Three-phase supply voltages WECS : Wind energy conversion system ZCS : Zero current switching

State of the Art on High Voltage Metrology: Past, Present and Future

“…Hence, AC voltage is converted into DC to be compatible with all DC appliances [11]. Consequently, AC to DC converter is needed to enable efficient conversion for these power devices [12]. By the end of the nineteenth century, power demand was increased, and people started to build power production centres.…”

Control and performance assessment of grid-connected PMSG-based wind turbine equipped with diode bridge rectifier and boost converter using three different control strategies

“…According to (24), the PI controller parameters pP k and iP k are obtained from the following equation: (25) where n  and  correspond to the undamped natural frequency and damping ratio of the PMSG active power control loop, respectively. Since the outer control loop should be much slower than the inner control loop, by selecting 0.1 nb   and 0.7   , the controller parameters are achieved.…”