A Five-Level Three-Phase Hybrid Cascade Multilevel Inverter Using a Single DC Source for a PM Synchronous Motor Drive
Summary (1 min read)
Introduction
- These approaches required a DC power source for each phase.
- This topology was proposed by one of the authors in [9].
- It is shown that one can simultaneously maintain the regulation of the capacitor voltage while achieving an output voltage waveform which is 25% higher than that obtained using a standard 3-leg inverter by itself.
II. MULTILEVEL INVERTER ARCHITECTURE
- Authorized licensed use limited to: Boise State University.
- The method consists of monitoring the output current and the capacitor voltage so that during periods of zero voltage output, either the switches S1, S4, and S6 are closed or the switches S2, S3, S5 are closed depending on whether it is necessary to charge or discharge the capacitor.
- Remark As Fig. 2 illustrates, this method of regulating the capacitor voltage depends on the voltage and current not being in phase.
III. SIMULATION RESULTS USING MULTILEVEL PWM
- A simulation of the multilevel converter driving a PM synchronous machine was carried out.
- The scheme is modified so that during those time periods when the converter is supplying zero volts, either the switches S1, S4, and S6 are closed or the switches S2, S3, S5 are closed depending on whether the current is positive or negative and whether it is necessary to charge or discharge the capacitor.
- For comparison purposes, simulations were performed using both the multilevel inverter of Fig. 1 capable of supplying ±200 V and a standard 3-leg inverter (i.e., only the bottom half of Fig. 1) capable of supplying ±100 V.
- The PM motor was run to achieve the highest possible speed under the given load and available voltage.
IV. CAPACITOR VOLTAGE REGULATION
- To illustrate how the capacitor voltage regulation works, scaled versions of the capacitor voltage, stator voltage, and stator current for phase 1 are shown in Fig. 11 for a fundamental frequency switching scheme (The technique is easier to illustrate using a fundamental switching scheme though the PWM scheme uses the same method).
- Note that the capacitor discharges when the inverter is supplying ±200 V, stays constant when the inverter is supplying ±100 V, and recharges when the inverter is supplying 0 V.
- A little after t = 5.575 seconds, the current (in black) becomes positive and the inverter is supplying 200 V (blue).
- Following this, when the inverter is only supplying 100 V, the capacitor voltage is constant.
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Citations
4 citations
Cites background from "A Five-Level Three-Phase Hybrid Cas..."
...A similar configuration where floating capacitor H-bridges are used to generate multiple voltage levels has been presented in [5] and [6]....
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4 citations
Cites methods from "A Five-Level Three-Phase Hybrid Cas..."
...It is noted that the above capacitor voltage regulation method is described using a fundamental frequency modulation scheme because it is easier to illustrate [7]....
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...The H-bridge can use a separate DC power source or a capacitor as the dc power source [7-11]....
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4 citations
Cites methods from "A Five-Level Three-Phase Hybrid Cas..."
...Another approach proposes a multilevel power inverter, with the structure of the cascade H-bridge inverter, using only one DC source [21-23]....
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3 citations
Cites background from "A Five-Level Three-Phase Hybrid Cas..."
...Series connected inverters, with different configurations [9, 28-33]....
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3 citations
References
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465 citations
"A Five-Level Three-Phase Hybrid Cas..." refers methods in this paper
...The motor is controlled using a standard field-oriented controller [10]....
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289 citations
"A Five-Level Three-Phase Hybrid Cas..." refers background in this paper
...Such inverters have been the subject of research in the last several years [1][2][3][4][5], where the DC levels were considered to be identical in that all of them were capacitors, batteries, solar cells, etc....
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237 citations