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Christoph Haederli - Les thèses en ligne de l'INP - Institut National ...

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NP Control with Carrier based PWM 119<br />

Figure 80 shows the complete state machine for three SMC modulation types. The states are<br />

numbered such that each bit corresponds with the state of an individual cell {c11 c12 c21 c22}.<br />

Any g<strong>en</strong>eric PWM modulator can be used for the <strong>de</strong>termination of the output levels of the<br />

individual phases.<br />

5.3.4 Experim<strong>en</strong>tal verification<br />

For the experim<strong>en</strong>tal verification, 5-level SMC (operated at 100V, 15A) has be<strong>en</strong> used. The<br />

prototype features curr<strong>en</strong>t s<strong>en</strong>sors in the neutral point to observe and / or control the NP curr<strong>en</strong>ts<br />

and voltages. One phase leg is shown in Figure 81.<br />

Figure 81, SMC phase leg (7-level, operated as 5-L)<br />

5.3.4.1 Verification of NP curr<strong>en</strong>ts<br />

The NP curr<strong>en</strong>t measurem<strong>en</strong>t is based on an H-bridge configuration to verify the NP curr<strong>en</strong>ts<br />

in any giv<strong>en</strong> operating point (random voltage and curr<strong>en</strong>t). One half bridge is operating as a voltage<br />

source in op<strong>en</strong> loop. The other half bridge is controlling the curr<strong>en</strong>t in the load (R-L load) in closed<br />

loop with a PID controller.<br />

Experim<strong>en</strong>tal results for the NP curr<strong>en</strong>t are shown in Figure 82. The operating point is chos<strong>en</strong><br />

at α L=0.625. The NP curr<strong>en</strong>t either corresponds with the output curr<strong>en</strong>t or remains at zero.<br />

(a) (b) (c)<br />

Figure 82, Measured data: standard type (left), type A (middle) and type B (right), Ch1 (blue): phase<br />

curr<strong>en</strong>t, Ch2 (red): NP curr<strong>en</strong>t, Ch3 (gre<strong>en</strong>): output voltage<br />

The NP curr<strong>en</strong>ts in the whole operating range of the converter has be<strong>en</strong> verified by measuring<br />

the NP curr<strong>en</strong>t in selected operating points (Figure 83).

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