Effect of Unipolar and Bipolar SPWM on the Lifetime of DC-link Capacitors in Single-Phase Voltage Source Inverters

Abstract

This paper explores the impact of different modulation techniques on the lifetime of DC-link capacitors for different modulation indices and varying operating power of voltage source inverter system. The conducted analysis show that the capacitor lifetime improves when using unipolar Sinusoidal pulsewidth modulation (SPWM), which introduces the highest lifetime for DC-link capacitors when a single unit voltage source inverter is used. Likewise, for two paralleled voltage source inverter unit' topology, both units using unipolar SPWM, having the same switching frequency produces the least thermal stress on the capacitor and consequently giving the highest lifetime.

DC-link Current Harmonic Mitigation via Phase-shifting of Carrier Waves in Paralleled Inverter Systems

“…In this study, a diode rectifier with boost power factor corrector (PFC), and DC-filter (consisting of a DC-choke and a large electrolytic DC-link capacitor) is implemented due 8 to its simplicity, cost-effectiveness, and reliability advantages [6]. Aluminium electrolytic 9 capacitors (El-caps) are used as DC-link capacitors, due to their advantage of providing a 10 high capacitance per unit volume at low costs compared to other types of capacitors [15].…”

“…Reducing the harmonics ripples in the DC-capacitor current helps to improve the lifetime L x of the DC-capacitor as the overall electrical and thermal stress in the capacitor significantly decreases [15]. The lifetime prediction model used in this paper is shown in Equation ( 10) and explained in detail (including the equivalent circuit model of capacitor) in [26].…”

“…V is the actual operating voltage. The value of the exponent p is between 3-5 for El-caps [15]. The hot-spot temperature T h of the DC-capacitor, estimated by Equation (11) depends upon the operating temperature and P loss the power loss of the capacitor (which is a function of ripple current and ESR).…”

DC-Link Current Harmonic Mitigation via Phase-Shifting of Carrier Waves in Paralleled Inverter Systems

“…In this study, a diode rectifier with a boost power factor corrector (PFC) and a DC-filter (consisting of a DC-choke and a large electrolytic DC-link capacitor) is implemented due to its simplicity, cost-effectiveness, and reliability advantages [6]. Aluminium electrolytic capacitors (El-caps) are used as DC-link capacitors, due to their advantage of providing a high capacitance per unit volume at low costs compared to other types of capacitors [17]. The boost PFC employed improves the power factor, as well as facilitates power supply hold-up, which ensures that the system can maintain the DC voltage until the backup power supply is connected, in case of a power supply disruption [18,19].…”

“…Reducing the harmonics ripples in the DC-capacitor current helps to improve the lifetime L x of the DC-capacitor as the overall electrical and thermal stress in the capacitor significantly decreases [17]. The lifetime prediction model used in this paper is shown in Section 5 and explained in detail (including the equivalent circuit model of capacitor) in [28].…”