Five-Level Single Source Voltage Converter Controlled Using Selective Harmonic Elimination

Abstract

The paper presents a 5-level cascaded H-bridge voltage source inverter. The converter topology composed of two-cascaded H-bridge modules connected in parallel and powered by a single DC source. The benefit of this topology in comparison with the conventional H-Bridge configuration is that it uses single input DC source instead of two to achieve the same output steps/levels. Selective Harmonic Elimination (SHE) is the modulation technique employed. The generated non-linear transcendental equations are solved using an optimised Genetic algorithms to find the switching angles. This property makes the topology and the control function suitable for three phase applications where triplen harmonics are said to cancel out at the line-to-line voltages. This concept of SHE modulation extends the value of the filter cut-off frequency, which translates to smaller sized filter, compact cooling system and reduced system weight. This advantage makes the topology attractive to automotive and renewable energy applications. The topology was simulated using PSIM software.

Performance comparison of series and parallel damped LCL filters using 5-level voltage source converter

“…Based on selective harmonic elimination theory, the converter eliminates (N − 1) harmonics, meaning all the 11 lower-order odd harmonics. In the prior study presented in [4], only the odd nontriplen harmonics were selected for elimination, i.e. (5th, 7th, 11th, 13th, 17th, 19th, 23rd, 25th, 29th, 31st, 35th).…”

“…MVSI appears to have overcomes the numerous drawbacks posed by the conventional two-level topologies [4,5]. Its modular nature makes it possible to achieve a high power rating by concatenating smaller power modules [4,6]. In the event of damage/ fault, it modularity warrants the ease of having component replacement and repair.…”

“…Converters with less harmonic-order elimination capability tend to have larger-sized filter components, hence increasing its physical size, weight and cost [21]. This issue is addressed by employing special modulation technique or new converter topology or both to eliminate the lower harmonics, hence, leaving behind only the higher-order ones that require a smaller-sized filter component [4,16,21].…”

“…the LCL filter with series resistors (LCL-S-R) and also the parallel resistor (LCL-P-R) connections. In some researches, it has been shown that the introduction of parallel damping resistors is better at suppressing the resonance effect and the THD component as compared to the series-configured one [4,9,13]. However, the majority of researchers fail to report the efficiency deterioration caused by incorporating the passive component into the system [38][39][40].…”

“…The contribution of this article is that it is the first to apply and assess the harmonic content of the proposed 5-level voltage source inverter presented in Shanono et al [4] using LCL, LCL-R-S and LCL-R-P passive filters. In addition, most research articles only analyse and report harmonic elimination capabilities of a specific filter at a fix output power, ignoring that the inverter output THD content along with the filter eliminating ability changes with an increase in loading.…”