The failure-tolerant control purpose lies in directing against different trouble sources and symptoms, take the corresponding fault-tolerant processing measure, compensate for trouble, dispel or repair automatically, in order to guarantee the apparatus continues safe reliability service, or regard sacrificing characteristic losses as the cost, guarantee the apparatus finishes its basic function within stipulated time. If you want to adopt failure-tolerant control, have structure or redundancy functionally in the real-time analysis system at first. Find through analyzing, as to the inverter circuit of single-phase full-bridge, in fact the structural redundancy exists. Can regard the whole-bridge circuit as the superposing of two pieces of half bridge converter, if can be after the gas switching tube trouble of the power of a bridge arm of the inverter of the full-bridge, blockade this bridge arm, reconstruct the characteristic of certain holding circuit as the half bridge converter of the whole-bridge circuit, realize failure-tolerant control. Fig. 1 is the equivalent electrical circuit that the circuit reconstructs after full-bridge circuit topology with fault-tolerant capability and first, two bridge arm switch troubles.
In Fig. 1a, divides into two the electric capacity C1 as half bridge converter of the direct-flow Filtering capacitance in the whole-bridge circuit, C2, links the first bridge arm middle point A with two electric capacity middle points o with the bidirectional thyristor VTr1, the bidirectional thyristor VTr2 links the second bridge arm middle point B with point o, forms full-bridge circuit topology with fault-tolerant capability in this way.
Normal working hour, VTr1, VTr2 is the off state, the circuit equivalent is the normal full-bridge inverter circuit. After the trigger impulse takes place and lose the trouble in the power tube VM1, adopt the fault-tolerant control strategy to close the power tube VM3 of the same bridge arm, touch off VTr2 to turn on at the same time, VTr1 keeps off, the whole-bridge circuit is reconstructed as the half bridge converter, the circuit equivalent, in order to pursue 1b at this moment. After the trigger impulse takes place and lose the trouble in the power tube VM2, adopt the fault-tolerant control strategy to close the power tube VM4 of the same bridge arm, touch off VTr1 to turn on at the same time, VTr2 keeps off, the whole-bridge circuit is reconstructed as the half bridge converter, the circuit equivalent, in order to pursue 1c at this moment. The original control device should carry on corresponding adjustment according to the change of the control objective after the circuit is reconstructed, in order to guarantee the characteristic maintains at the acceptable range.
Sum up the fault-tolerant control strategy as follows, suppose VMi i =1,2,3,4The trigger impulse is lost. The whole fault-tolerant control process can be divided into the following several step: Judge the switch position of the trouble in fault detection and diagnostic circuitry; Blockade the trigger impulse of power switch on VMi and the same bridge arm in control unit, touch off the bidirectional thyristor which connects this bridge arm; The control unit changes the controller parameter, it is topological after make it adapt to reconstructing.
On the foundation of analyzing in the principle and artificial experiment, have designed and made a low-powered experimental provision. The experimental parameter is: Switching frequency fs =10 kHz; Export the filtering inductance L =1 mH; Filtering capacitance C of the output =20 F; Input the Filtering capacitance C1 =C2 =1 000 F; Direct-flow input voltage Uin =48 V. All power switches adopt the power MOSFET of the Model IRF650A, the output voltage adopts the voltage to isolate the man of great talent AD202 to measure after partial pressure. The output current measures and adopts the electric current transducer of Hall of Model CSB6-50A. The sense resistor of electric current of elementary straight flow side adopts 4 times 0. The resistance of 3 / 2 W is connected in parallel. Input the filtering resistance and is formed by two pieces of 1 000 F electric capacity, o some connect A, B bipunctate with VTr2 by VTr1. The bidirectional thyristor chooses BTA16-600B, drive and choose the bidirectional thyristor to drive special purpose chip MOC3 021. The main control chip of the circuit adopts the Model TMS302LF2407A DSP, is finished implementation of failure diagnosis and fault-tolerant tactics by it.
Experimental analogy VM1 is on the appointed phase place 90 degrees, 170 degrees, 270 degrees The trigger impulse takes place to lose the trouble, after the testing signal is judged by DSP trouble diagnostic element, carry out the fault-tolerant control procedure, blockades VM2 trigger impulse, touches off VTr1, it is 2 fold to change the given sine wave uref.
