Single‐phase hybrid cascaded H‐bridge and diode‐clamped multilevel inverter with capacitor voltage balancing

Abstract

Diode-clamped and cascaded H-bridge multilevel inverters are two of the main multilevel inverter topologies; each has its distinct advantages and drawbacks. Regarding the latter, cascaded H-bridge inverters require multiple separate dc sources, whereas (semi-active) diode-clamped inverters contain capacitors that require a means to balance their voltages. This paper investigates a hybrid-topology inverter, comprising a single-phase five-level semi-active diode-clamped inverter and a single-phase cascaded H-bridge inverter with their outputs connected in series, as one way to mitigate the drawbacks of each topology. The proposed control scheme for this inverter operates the switches at fundamental frequency to achieve capacitor voltage-balancing while keeping the switching losses low. Moreover, the step-angles are designed for the 13-level and 11-level output voltage waveform cases (as examples) for a fixed modulation index to achieve optimal total harmonic distortion. Furthermore, the scheme also achieves capacitor voltage-balancing for modulation indices that are close to the optimal modulation index, and for a wide range of load power factors, albeit at the cost of increased output voltage distortion. Simulation results are presented to help explain the processes of capacitor recharging and voltage-balancing, while experimental results are shown as verification of the expected behaviour of this inverter and the proposed control scheme.

A coordinated DC voltage control strategy for cascaded solid state transformer with star configuration

“…DC-AC inverter of the output stage is not studied in this paper. Figure 2 describes the average mathematical model of a single-phase cascaded SST, which is established according to [11][12][13]. All variables in Figure 2 are average values in a switching period.…”

“…In contrast, the software method, which includes inphase and interphase DC voltage balancing control methods, is more practical. The inphase DC voltage balancing can be solved by adjusting the amplitude or phase angle of each H-bridge voltage modulation wave [12,13]. Ye et al [14] applied the idea of inphase to the interphase DC voltage balancing, which is equivalent to control the three phases separately without considering the coupling relationship among three phases.…”

Performance Assessment of Modular Multilevel Half Bridge Inverter for High Power PV Application

“…Real power transmission has meager switching utilization and efficiency. Presence of huge number of capacitors make it more opulent and healtier in comparison with multilevel diode-clamped converters [6]. separate dc-sources.…”

“…In a diode-clamped inverter, balancing the capacitor voltage remains as a critical problem in high levels. When the level increases, the use of power semiconductor devices gradually increase and the realization of the inverter become difficult [6]. The CC-MLI topology uses several clamping capacitors as a replacement for of clamping diodes in NPCI.…”

“…The CHB topology is more suitable for high power usage capacity and consistency than other conventional multilevel inverters due to the modular structure. This inverter requires huge number of seperated dc sources for each H-Bridges of CHB-MLI that are generally given by a bulky, multi winding transformer along with rectifiers and to reach higher voltage levels is a challenge for semiconductor technology, increasing the blocking voltage and other related technologies like gate drivers and sensors and numbers of semiconductor devices [6][7][8][9].…”