Circuit Configuration and Modulation of a Seven-Level Switched-Capacitor Inverter

Abstract

In this paper, a step-up seven-level inverter supplied by a single DC source suitable for renewable energy application is presented. Forming the desired output is realized by charging capacitors and synthesizing them based on switched-capacitor concept. This structure is praised for the ability of sensor-less voltage balancing of the capacitors, reducing control complexity to produce a bipolar staircase waveform. It also benefits from regenerative performance, avoiding unwanted capacitors overvoltage. Phase Disposition Pulse Width Modulation (PD-PWM) technique is utilized to control the circuit operation. Furthermore, a comparison with other recent topologies reveals that losses, number of semiconductor devices, and gate driver circuits are reduced. Theoretical analysis is verified through a laboratory prototype implementation. Experimental results under various types of loads approve the performance of the proposed inverter and validity of the design. Finally, maximum experimental efficiency of 94.3% (115 V, 250 W load) was reached.

Fault-Tolerant Operation Strategy for Reliability Improvement of a Switched-Capacitor Multilevel Inverter

“…Generally, power loss in switched-capacitor converters is classified into three groups: switching loss, conduction loss, and the loss caused by capacitor voltage ripple [7].…”

“…The number of circuit elements involved in forming each level is listed in Table I. Moreover, irms-L and iavg-L are the RMS and average current of semiconductors in each level (for [ta, tb]) for a quarter of a cycle, obtained from (7). Finally, the total conduction losses for the proposed inverter can be calculated by:…”

“…The difference between the DC input voltage (Vdc) and each capacitor's voltage is the origin of the capacitor ripple loss [7]. The voltage ripple of a capacitor is acquired from:…”

“…Moreover, MLIs have become popular in many applications such as photovoltaic systems [2], uninterrupted power supply [3], solid state transformers [4], and electric vehicles [5]. These structures benefit from better output quality, improved performance, lower voltage stress on their switches, and less Total Harmonic Distortion (THD) [6], [7]. However, MLIs have a higher number of devices and a more complex control system compared to two-level conventional ones [8].…”

A Novel Switched-Capacitor Inverter with Reduced Capacitance and Balanced Neutral-Point Voltage

“…Inverters using the same working principle are called switched-capacitor multilevel inverters (SCMLI), which have become a recent research topic of interest [17,18]. Unlike…”