Analysis and minimization of ripple components of input current and voltage of PWM inverters

Analysis of DC-Link capacitor losses in three-level neutral point clamped and cascaded H-Bridge voltage source inverters

“…As a result, the majority of carrier and sideband harmonic groups, which appear around multiples of the switching frequency, belong in the constant-ESR frequency range. Fundamental and baseband harmonics, however, have to be associated with higher ESR values, according to (1). Loss estimation based on current rms expressions (3) fails to treat these harmonics separately, which results in an underestimation of DC-link capacitor losses for the threelevel inverters.…”

“…(8) Equation (8) is not applicable to inverters that operate at low switching frequencies or use capacitors with different ESR characteristics. In these cases, certain carrier -sideband harmonic groups may belong to the low frequency ESR region and therefore the results of a complete harmonic analysis should be used according to (1).…”

“…Equations that give the current rms values of the two-level and three-level NPC and Cascaded H-Bridge inverters are included in the Appendix. Their derivation for the case of the two-level inverter can be found in [1] - [3]. The three-level inverter equations are part of unpublished work [8].…”

“…The rms value of the total current flowing through a capacitor can provide a first approximation for its losses. The literature contains rms expressions for the capacitor current of the two-level [1] - [3] and the three-level Cascaded H-Bridge inverters [4]. Use of these expressions for loss estimation assumes a fixed ESR value.…”

Theoretical and Experimental Investigation of Switching Ripple in the DC-Link Voltage of Single-Phase H-Bridge PWM Inverters

“…The RMS value of the DC-link capacitor current in three-phase voltage source PWM inverters is calculated by using the time domain approach in [14,15]. For synthesizing the DC-link current, only the fundamental component of the line current is considered, and the effect of the line current ripple is neglected.…”