• Introduction

The belt rectification load synchronous generator system has widely existed to the power plant, the ships, the airplane and so on in the independent power supply system. Have received many scholars' attention regarding the rectification system model computation and the simulation. But as a result of the synchronous machine and the rectification bridge mathematical model establishment and the solution complexity, has brought the certain difficulty for people's analysis research.

Along with MATLAB software promoting with the development, this software formidable computation ability and the consummation electrical power system model causes the belt rectification load the synchronous generator simulation question to change simple and direct and is accurate. This article through the establishment belt rectification load synchronous generator system MATLAB simulation model, has analyzed this system each kind of dynamic process, the contrast simulation and the test result, proved MATLAB the simulation model can satisfy the actual electrical power system research the need, the result quite is ideal. At the same time, the simulation result regarding rectification work and so on system parameter design, fail safe, equipment movement reliability all has the vital significance.

• Rectification system model establishment

2.1 synchronous generators dynamic mathematical model

When analysis synchronous generator dynamic mathematical model, makes the following supposition that, (1) The generator parameter is constant; (2) The magnetic saturation, the magnetic lag, the vorticity effect ignore; (3) Stator three-phase symmetry; (4) Neglects the magnetic field the higher harmonic.

The synchronous machine is composed by the stator and the rotor two parts, on the stator has A, B, the C three windings, on the rotor has a exciting winding, two damping windings, between these six windings has the mutual electromagnetic coupling relations. The synchronous generator d axis and q axis equivalent circuit diagram like chart 1 shows.

Chart 1 synchronous generator d axis, q axis equivalent circuit diagram

According to the electric circuit KVL law, the generator six windings may establish the following six return routes voltage balance equation:

(1)

(2)

(3)

(4)

(5)

(6)

The in the formula symbol showed that,

D, q: 直轴, hands over the axis component;

R, s: Rotor, stator component;

L, m: Leaks the feeling, the self inductance;

F, k: Exciting winding component, damping winding component;

According to six windings between flux linkage coupling relations, according to the right-hand screw rule, may obtain the generator mathematical model as follows six flux linkages equation:

(7)

(8)

(9)

(10)

(11)

(12)

2.2 rectification bridges mathematical model

The rectification bridge is composed by the three-phase full-wave rectification electric circuit. The rectification bridge 桥臂 may by the diode, the crystal thyratron, GTO, MOSFET, IGBT and so on the many kinds of forms constitute. Each kind of pipe mathematical model all is by leads passes the resistance, leads passes the inductance and first to the pressure drop series constitution. The pipe mathematical model is as follows -like:

Vak= (Ron+Xon) i+Vf (13)

In the formula, Ron: Leads passes the resistance; Xon: Leads passes 电抗; Vf: First to pressure drop

2.3 rectification system model establishment

The synchronous generator and the rectification bridge simulation model establishes which according to above, this article has established like chart 2 synchronous generators rectification system simulation model. In order to eliminate the harmonic interference which the rectification bridge produces, in direct current side parallel filter electric capacity C and resistance.

Chart 2 synchronous generator rectification system simulation model

In the simulation, synchronous generator power input Pm, excitation voltage Vf and the original state hypothesis may need to produce according to the load by the Powergui module. The Powergui module is in the MATLAB6.5 electrical power system simulation a function very formidable module, may carry on the electrical machinery the original state hypothesis, the stable state movement computation, the inductance, the frequency measurement, Fourier analyzes and so on the simulation. The Powergui module may act according to the synchronous generator which requests to output hands over streamline voltage value Uab and active power value P calculates the synchronous generator power input Pm, parameter and so on excitation voltage Vf and original state.

• Simulation and experimental analysis

In system simulation generator, rectification bridge, load parameter by experimental survey determination. The synchronous generator is 5kVA/380V, the 1500r/min constant 电压�? excitation synchronous machine (non- excitation adjusting device), the rectification bridge is the 380V/300A three-phase diode not controllable rectification bridge, the filter electric capacity is 100 mu F, the load is 4.2resistances.

The synchronous generator concrete parameter (sign �? value) see Table 1:

Table 1 synchronous generator parameter

Under to the synchronous machine belt rectification load shock load, suddenly unloads the load and suddenly short-circuits the dynamic process to carry on the simulation analysis.

3.1 rectification systems shock load simulation analysis

Because experiments the rectification load rated power to be smaller, in order to be advantageous for the simulation result and the test result carries on the contrast, when simulation, (有效�? establishes the generator exchange output line voltage is 42V.

Single synchronous generator rectification system shock load simulation result like chart 3 shows (load switch when t=1s closed). (a) is the rectification bridge output voltage Uz profile, (b) is the load beginnings and ends voltage Usc profile. May know by the chart, when generator idling, rectification bridge output voltage Uz approximately is 56V, after the switch closed, as a result of the non- excitation adjustment, the voltage will descend after the short transient process will be 18V. Load voltage Usc closed rapidly rises after the switch the peak value, then recedes to 16V about.

(a) voltage Uz profile

(b) voltage Usc profile

Chart 3 generator movement simulation result

Above in order to examine the MATLAB simulation to be correct or not, this article has carried on and the simulation parameter same synchronous generator belt rectification load test. In the experiment, the synchronous machine rotational speed the direct current motor which controls by the LTG1-55kW direct current velocity modulation cabinet (220V/90A) provides, the synchronous machine excitation by is constant 电压�?provides. Experimental profile through Wavestar For Oscilloscopes software from oscilloscope TDS220 input. Test result like chart 4 shows (load switch when t=1s closed). (a) is the rectification bridge output voltage Uz profile, (b) is the load beginnings and ends voltage Usc profile. Contrast chart 3 and chart 4 corresponding voltage waveforms, the simulation basic was consistent with the test result, has proven the simulation accuracy.

(a) voltage Uz profile

(b) voltage Usc profile

Chart 4 generator performance test result

3.2 rectification systems suddenly unload the load simulation analysis

The synchronous generator suddenly unloads the load is time the synchronous machine belt rectification load movement another model transient process. This article used the same simulation model to carry on the simulation analysis to this process. Simulation result like chart 5 shows (load switch when t=5s separates). (a) is the rectification bridge output voltage Uz profile, (b) is the load beginnings and ends voltage Usc profile. May know by chart 5, rectification bridge output voltage Uz after switch separation rapid rise to 50V, then the experience approximately 3s time restrains to lost motion stable state value 56V. Load voltage Usc after the switch separation the rapid drop is 0.

(a) voltage Uz profile

(b) voltage Usc profile

Chart 5 generator movement simulation result

Attempted 6 pieces to produce the synchronous machine from the load to the idling experimental profile, (a) was the rectification bridge output voltage Uz profile, (b) was the load beginnings and ends voltage Usc profile. The simulation and the test result also are quite tallies.

(a) voltage Uz profile

(b) voltage Usc profile

Chart 6 generator performance test result

3.3 rectification systems suddenly short-circuit the simulation analysis

The rectification system suddenly short-circuits the breakdown is the electrical power system common one kind of breakdown, also is the question which the system protection must consider, the huge short-circuit current is threatening the system safe operation. The short-circuit current size determination 整定 the design has the vital significance regarding the rectification system protective device. The simulation model establishment enable this design process to obtain greatly simplifies.

The rectification system direct current side short-circuits is equal three-phase symmetrically short-circuits to the exchange side. Chart 7 is the rectification system under the rated voltage 230V lost motion condition, the rectification side occurs suddenly short-circuits the breakdown direct current side and the exchange side current waveform. By the chart obviously, the system direct current side most greatly short-circuit current peak value approximately is 280A.

(a) direct current side current waveform

(b) exchanges the side three-phase current profile

Chart 7 rectification system suddenly short-circuit current profile

In order to study between the short-circuit current and the synchronous machine parameter relations, and the discussion reduces most greatly the short-circuit current peak value method. This article supposes the generator other parameters to be invariable, 直轴 ultra transient 电抗 Xd ' ' from 0.073 will become 0.15, will carry on same the direct current side will short-circuit the simulation, short-circuit current profile like chart 8 shows. May know by the chart, along with Xd ' ' increasing, most greatly short-circuits the peak value remarkably to reduce.

Attempts 8Xd ' ' the =0.15 short-circuit current profile

The further simulation research also discovered short-circuits the magnitude of current size and Tdo ' ' the related department. Supposes the generator other parameters to be invariable, Tdo ' ' becomes 0.01s from 0.0701s, short-circuit current profile like chart 9 shows. Because Tdo ' ' reducing, most greatly the short-circuit current peak value has obvious reducing.

Attempts 9Tdo ' ' the =0.01s short-circuit current profile

• Conclusion

(1) has established the belt rectification load synchronous generator MATLAB simulation model, through the contrast simulation and the experimental profile, has confirmed this simulation model accuracy.

(2) through suddenly short-circuits to the rectification system the process simulation research discovery, 直轴 ultra transient 电抗 Xd ' ', 直轴 ultra transient short-circuits time-constant Tdo ' ' to have a more tremendous influence to the system most greatly short-circuit current peak value.

(3) in the rectification system design, may according to the short-circuit current control need, the design and the choice appropriate synchronous machine parameter, guarantees the fail safe installment the security movement.