A Four-Level Single-Phase Diode-Clamped Inverter with Natural DC-Link Capacitor Voltage Balance

Natural DC‐link voltage balance in a single‐phase NPC inverter with four‐level legs and novel modulation method

“…In the F Cn functions, the f s frequency dominates, thus the output voltage (1) can be approximated, in the switching frequency domain ( f s ), by the following function [14]: where a 1−3 are amplitudes, dependent on capacitors’ voltages, phase shift of a harmonic in relation to the symmetric system.…”

“…Considering target implementations and some indicators, the NPC inverter can offer more favourable solutions than other inverters, such as, for example the modular multilevel converter [4]. An increase of the NPC converter modulation to four levels [5–15] or higher [16–23] is favourable for voltage stress on switches and output voltage quality.…”

“…Most of the proposed methods are based on the use of an appropriate PWM since the flow of the output current has a fundamental impact on the voltages of capacitors. Several concepts related to the operation of multilevel NPC converters, including input voltages balancing and PWM impact, are presented in [2–19, 21–36]. In [6], the DC‐link voltage balance is achieved by adequate space vector PWM.…”

“…A literature review shows research results of the application of the natural DC‐link voltage balance in the three‐level three‐phase diode clamped inverter [24, 35] in the single‐phase bridge with three‐level legs [25, 26] as well as in four‐level legs single‐phase inverter [14]. For the three‐level NPC inverter with a natural balancing ability, the relatively simple carrier‐based switching strategy can be used.…”

“…Stala [14] introduces the idea of utilisation of the natural balancing process achieved by special switching patterns, reinforced by a balancing booster. The concept was supported by steady‐state simulation results.…”