Control of a Brushless Doubly-Fed - U
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Control of a Brushless DoublyFed Induction Machine The University Of Chile Presented by: Roberto Cárdenas University of Chile Doubly-Fed Induction Generators • This machine is widely used in variable speed wind energy applications. Currently this topology occupies close to 50% of the wind energy market. Some commercial DFIGs in the 1MW to 3MW power range Typical topology for a DFIG * * Power converters are usually designed for a nominal power of 30% of that of the doubly-fed machine. Problems related to the use of Brushes slip rings • In most of the applications where robustness is required, the use of brushes has to be avoided. • For instance in remote areas, where regular maintenance is difficult to achieve. Proposed Brushless Topology • This is just a representation. • Two DFIGs in the same shaft (“cascaded” implementation). The signals induced in the rotor of the first machine are used to excite the power machine. Proposed Brushless Topology • The Brushless DFIG (BDFIG) could be also implemented using two (3 each one) stator windings. • Mathematically the BDFIG implemented using two cascaded machines is similar. Stator 1 Rotors Stator 2 3x3 MC r r* Encoder board Variac 3 grid Current Tranducers Isolation Encoder Cage Machine Excitation DFIM Power DFIM Voltage Tranducers Proposed Brushless Topology r sc sg DFIG DFIG r feg fsl fec To Matrix Converter To Grid Power Converter used in this applications Grid input Input Filter Bidirectional Switch A B s11 s22 s21 s12 s13 s23 C s31 a s32 s33 b c To the stator of the excitation machine Power Converter used in this applications MC input Input Capacitor Gate Circuits for the Bidirectional switches Current Transducer Designed in the University of Nottingham MC output Clamp Voltage Transducers Vector Control System e sg d isdg q e isg e e sg isg DFIG DFIG isqg q Control system Power machine currents r r DFIG feg Power machine currents Excitation machine currents DFIG fsl Excitation machine currents fec Relationship between the currents in the excitation and power machines Gd() Relationship between the currents in the excitation and power machines Gq() Control Loops Nested control loops. The outer loop is regulating the currents of the power machine. The inner control loop is regulating the currents of the excitation machine. Experimental System 3x3 MC r r* Encoder board Variac 3 grid Current Tranducers Isolation Encoder Cage Machine Excitation DFIM Power DFIM Voltage Tranducers Experimental System Encoder r r Excitation Machine DFIG Current Regulation D/A A/D isc SVM Algorithm FPGA Based Switching A/D conversion DSP+FPGA ir isg vs DFIG Power Machine Matrix Converter Input Filter Grid Wind speed (ms-1) Experimental Results 10 8 6 isgq d-q Currents (A) 10 5 isgd 0 5 iscd 0 -5 iscq -10 0 5 10 15 20 25 Time (s) 30 35 40 Power (W) Experimental Results 3000 P 2000 Speed (rpm) 1000 800 750 r 700 650 0 5 10 15 20 25 Time (s) 30 35 40 Experimental Results 10 a) iasc b) iar c) iasg 0 Currents (A) -10 20 0 -20 10 0 -10 0 0.1 0.2 0.3 0.4 0.5 Time (s) 0.6 0.7 0.8 0.9 Conclusions • The BDFIG is an alternative to the conventional Doubly-Fed Generator in remote sites where maintenance is not simple to achieve. • The simplified model proposed here can be used to design the control system. The simplifications arise from the fact that wind energy systems have slow dynamic due to the relatively large blade inertia. • Experimental results have been obtained which confirm the performance of the proposed methodology. Any question?
