Automated methodology for adjustment of component values in passive converter circuit for wind turbine generators

Abstract

-The current paper proposes an automated design approach for a previously developed passive converter circuits for wind turbine generators. This suggested approach allows to calculate the components for all passive converter circuits approved in European patent number PCT/EP2010/055637, where only minor changes in the source code of the mathematical and simulation software have to be made when different circuits are involved. An optimisation based on steepest descent method results in power/frequency (power/speed) curve that matches well the cubic dependence (P wtmax~ω 3 ) of the extracted power.Keywords -Converter circuit, Simulation, Wind energy.I. INTRODUCTION It is a valid fact that wind turbines are most efficient in variable speed mode [1][2][3][4]. The first electrical conversion AC/DC from the three phase generator has key role in the energy extraction. An active or passive rectifier will determine the type of electrical control that is used in the system. Usually the use of single three phase uncontrolled full wave rectifiers (passive) is limited to low power applications. An advantage is the lack of complicated control unit which significantly reduces the design time and the final price. Disadvantage is the poor electrical efficiency compared with the fully controlled thyristor or transistor rectifiers or so-called active.A novel design for passive converter circuit ( fig. 2.) improves the overall efficiency. The circuit includes the following components: two 3-phase full bridge uncontrolled rectifiers build with diodes D1÷D12, external inductors L ext1 ÷L ext3 and a simplified model of the permanent magnet synchronous generator consisting of voltage source V1÷V3 and inductor L gen1 ÷L gen3 for every single phase. The modeling of a power/frequency curve of a wind turbine with PMSG and passive converter is done by specifically developed methodology. It includes parametrical optimization of the values of L ext and L gen . As a result the power/frequency curve should match the well-known cubic dependence P wtmax ~ ω 3 [5].

Comparison of multiple stage braking circuits for wind driven generators

“…The rectifier consists of a two three phase uncontrolled rectifiers connected to every winding at both ends of the three phase generator. Simulations shows that external inductors improve significantly low speed power output of the wind turbine [6].…”

“…Using two full wave three phase rectifiers and externally connected inductors this circuit has some significant advantages over the conventional back to back converters. The circuit uses diodes instead of transistor to form a power/frequency output curve that is as close as possible to the ideal cubic dependence of the wind speed and power output of the machine [6].…”