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1

Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 2: Small Normalised Voltage Command

Reznikov Boris, Ruderman Alex, Galanina Valentina

Power Electronics and Drives

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2020

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Vol. 5 (40)

41--57

EN

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

2

Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 1: Large Normalised Voltage Command

Reznikov Boris, Ruderman Alex, Galanina Valentina

Power Electronics and Drives

|

2020

|

Vol. 5 (40)

27--40

EN

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

3

Analysis of Transients in a Three-Level DC–DC Flying Capacitor Converter. Time Domain Approach

Reznikov Boris, Ruderman Alexander, Galanina Valentina

Power Electronics and Drives

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2019

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Vol. 4 (39)

33--45

EN

The paper considers a discrete state-space model for transients in a three-level flying capacitor DC–DC converter. A transition matrix is obtained for a pulse width modulation (PWM) period. The matrix elements are expanded into a power series using a selected small parameter. The matrix eigenvalues that determine the natural balancing dynamics transients are presented in the form of power series as well. Four separate transients are constructed based on four possible PWM period initial states (topologies). Inductor current and capacitor voltage transients are found for the voltage source power-up as the arithmetic average of the four separate transients. The discrete solutions are replaced by continuous ones. The resulting transients that are elementary functions of the circuit parameters, PWM period, and voltage reference demonstrate good agreement with the simulation results.

4

A Study of The Balancing Process in Multicell ac/ac Converter

Stala R., Mondzik A.

Przegląd Elektrotechniczny

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2009

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R. 85, nr 7

168-172

EN

The paper presents the experimental and simulation study of the balancing process forced by passive RLC circuit in a multicell ac/ac converter. The multicell ac/ac converter bases on the flying capacitor concept. Appropriate charging and reversing charge of the flying capacitors in the converter is necessary for its proper operation. This is achieved by application balancing circuit - a series RLC circuit connected at the converter output, that improves natural balancing process in the converter. The main issue is the correct choice of the balancing circuit characteristic impedance and the converter parameters (switching frequency, capacitances of cells capacitors) that allows maintaining a correct shape and proportion of voltages across cells capacitors at minimum balancing current.

PL

Artykuł prezentuje wyniki badań symulacyjnych i eksperymentalnych procesu balansowania za pomocą pasywnych obwodów RLC w wielokomórkowym przekształtniku typu AC/AC. Przekształtnik wielokomórkowy bazuje na koncepcji „flying capacitors”. Ładowanie i rozładowywanie kondensatorów jest niezbędna dla prawidłowego funkcjonowania układu. Osiągnięto to poprzez obwód balansujący – szeregowy obwód PLC połączony na wyjściu przekształtnika. Główne zadanie polega na prawidłowym doborze charakterystyki impedancyjnej obwodu balansującego oraz parametrów samego przekształtnika (częstotliwości przełączeń, pojemności kondensatorów).