J. Q. WANG ET AL.

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Figure 4. Simulation model.

Figure 5. Current waveform.

In Buck converter simulation, set the voltage feedback

loop control system, the converter input voltage E = 200

V, output voltage Uo = 120 V, the initial resistive load is

1.5 Ω, due to it is assumed that the converter has been

working in CCM state[10-12], according to inductance

L、C of formula, it can obtain the value of the L, C, and

then multiplied by a certain margin coefficient, and fi-

nally set L = 6e-5 H, C = 5e-4F,make simulation time is

0.02 seconds, and paralle a plurality of resistive load in

the load terminal, then trigger pulse at different times, the

purpose of increasing the load is to observe the change of

the input current, and the validation of the negative im-

pedance characteristics. The simulation model is shown

in Figure 4.

4. Results of Simulation

Since the input voltage is maintained at 200 V, only ob-

serve the input current, the increase resistive load added

in 0.002 s, 0.005 s, 0.01 s, taking into account the effi-

ciency of the inverter is 100%, The obtained current

waveform is shown in Figure 5.

Seen by the waveform diagram of the current in the

load side of the power increase, the average of the input

current increases, the input voltage to maintain the same

circumstances, and seen by the Ohm’s law, the input re-

sistance of the converter decreases, showing negative

impedance characteristics.

5. Results of Simulation

It get the same conclusion whether in theoretical way or

simulation way, the voltage Buck converter exhibit nega-

tive impedance characteristics. In order to avoid the ad-

erse effects of the negative impedance characteristics in

engineering, They often put filter in the converter pre-

ceding, increasing the positive impedance to counteract

the negative impedance converter produced, It lead us to

use Buck converter input impedance characteristics to the

next research, such as provides a good reference for

study on DC bus stability.

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