A Real-Time Estimator for Capacitor Voltages in the Flying Capacitor Multilevel Converter

Petric, Ivan Z.; Iyer, Rahul K.; Brooks, Nathan C.; Pilawa-Podgurski, Robert C. N.

doi:10.1109/compel53829.2022.9829954

Cited by 9 publications

(4 citation statements)

References 15 publications

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“…Note that for balanced operation where ∆E Dc = 0, at D c ∆I = 0, which is a known property of PS-DPWM. Due to this property, the operating points defined by (1) are sometimes called nominal conversion ratios [5].…”

Section: Switching Ripple Around Critical Operating Points In Unbalan...mentioning

confidence: 99%

“…Its inherent ZOH function transforms m s to m and compares it with the carrier w i , belonging to DPWM i . In this 2 PS-DPWM with triangular carriers simplifies the choice of sampling instants that coincide with the average current values [5]. Moreover, it allows dual-edge modulation [37], which improves the transient response capabilities; hence, triangular carriers are typically chosen over the sawtooth ones.…”

Section: A System Descriptionmentioning

confidence: 99%

“…A widely used modulation strategy for MC-VSCs is the digital phase-shifted pulsewidth modulation (PS-DPWM) [2]- [5], [7], where the carriers of the subsequent cells are phaseshifted with respect to each other, so that harmonic cancellation is achieved at the output [10], [11]. Under balanced conditions, this yields an increased frequency of the output current ripple, i.e., frequency multiplication [12], enabling output filter reduction [7], [12] and control loop bandwidth improvement [6], [13]- [17].…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, ideally balanced operation is rarely achieved in practice due to tolerances of passive components, timing mismatches in gatedriving circuits, transients, different nature of the sources/loads connected to each cell's dc link, etc. [1], [5], [9], [22]- [25], [28]- [32]. Imbalance deteriorates frequency multiplication and causes the switching ripple to appear in the feedback.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinearities of Multisampled Phase-Shifted PWM in Unbalanced Multicell Converters

Cvetanovic,

Petric,

Mattavelli

et al. 2024

IEEE J. Emerg. Sel. Topics Power Electron.

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This article reveals, analyzes and proposes the method to mitigate nonlinear effects of multi-sampled multiupdate (MSMU) digital phase-shifted pulsewidth modulators (PS-DPWM) that appear in unbalanced multi-cell voltage-source converters (MC-VSCs). For balanced MC-VSCs, the harmonic cancellation of PS-DPWM allows for an increase in the sampling frequency, ensuring that the average current is acquired at the peaks, valleys, and intersections of all triangular carriers. For unbalanced operation, which is typically encountered in practice, e.g., due to cell voltage mismatch in multilevel MC-VSCs and inductance mismatch in interleaved MC-VSCs, harmonic cancellation of PS-DPWM is compromised and, thus, the increased sampling frequency brings switching ripple in the feedback signal. Since in MSMU control the modulating signal is also updated at peaks, valleys, and intersections of all carriers, this may cause vertical intersections between the modulating signal and the carriers, resulting in specific nonlinear effects. The nonlinearities are shown to introduce limit-cycle oscillations and output waveform distortion. A method to prevent such detrimental impact of MSMU-PS-PWM is also proposed. A simple analytical procedure is proposed to quantify the analyzed non-linear effects, revealing that they are more emphasized for higher levels of imbalance and control bandwidth. Moreover, the modulator nonlinearity is shown to decrease as the number of cells increases. The analyses are verified in simulations and experiments, using laboratory prototypes of three-and four-level MC-VSCs.

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Section: Switching Ripple Around Critical Operating Points In Unbalan...mentioning

confidence: 99%

Section: A System Descriptionmentioning

confidence: 99%