AN4070 datasheet(38/53 Pages) STMICROELECTRONICS

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Experimental test results

AN4070

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Doc ID 022934 Rev 1

and the DC-AC converter to be adjusted by acting on the duty cycle and modulating index

respectively. The duty cycle has been adjusted to obtain a DC bus voltage of 390 V and the

modulating index in order to get 230 V AC on the output for each test point. The efficiency

characterization of the DC-DC converter and of the system is shown in Figure 28 and 29

respectively. The peak system efficiency is about 94% and the CEC efficiency is 93.4%.

While Figure 27 shows the MIC output waveforms when operating in open loop mode,

Figure 30 shows the same waveforms when the system is operating at nominal power in

closed loop mode and grid connection. In these operating conditions the current THD is

2.8%. When operating in grid connection, the current THD is higher and equal to 4.8% at full

load while the power factor is equal to 0.92. Figure 30 shows the current and voltage

waveforms during grid connected operation. It is worth noting that the PLL signal (yellow

track) is synchronized with the peak of the grid voltage. Finally, Figure 31 and 32 show the

variation of output current THD and power factor across the operating profile of the system.

Figure 27.

DC-AC converter output voltage and current waveforms

AN4070 Datasheet(PDF) 38 Page - STMicroelectronics