Comparison of bipolar sub-modules for the alternate arm converter

Abstract

Abstract-Research on dc-fault tolerant multilevel converters has gained noticeable attention over recent years. The alternate arm converter (AAC) is one of such emerging multilevel converter topologies, and a hybrid topology of the two-level converter and the modular multilevel converter (MMC). Bipolar submodules (SMs) that can produce both positive and negative voltages are the building blocks of the AAC. This paper analyses the operation of an AAC with the full-bridge SM (FB-SM) and the crossconnected SM (CC-SM). The conduction and switching losses of the two SM configurations are evaluated and compared, in order to identify the suitability of CC-SM for AACs and its performance compared to the FB-SM. The CC-SM with identical semiconductor devices has reduced losses compared to the CC-SM with higher rated devices in the cross-connected path. It is concluded that the CC-SM does not offer advantages in the losses, construction, and application to the AAC, compared to FB-SM.

Recent contributions and future prospects of the modular multilevel converters: A comprehensive review

“…Wickramasinghe et al investigate the feasibility of MMC SMs for alternate arm converter (AAC). Additional director switches in the upper and lower arm are inserted to conventional MMC topology to obtain AAC.…”

Arm energy balancing control in AACs: a comparative analysis

“…Among various types of multilevel VSCs, modular multilevel converter (MMC) has become a remarkably appealing topology for high-voltage-direct-current (HVDC) transmission system and medium-voltage applications [5,6]. In addition to the inherited feature of multilevel VSCs -generation of close sinusoidal output voltage and current with low harmonic distortion, the MMC is also excellent in terms of modularity, scalability, ability to handle a wide range of power ratings, redundancy and efficiency [6][7][8].…”

“…Among various types of multilevel VSCs, modular multilevel converter (MMC) has become a remarkably appealing topology for high-voltage-direct-current (HVDC) transmission system and medium-voltage applications [5,6]. In addition to the inherited feature of multilevel VSCs -generation of close sinusoidal output voltage and current with low harmonic distortion, the MMC is also excellent in terms of modularity, scalability, ability to handle a wide range of power ratings, redundancy and efficiency [6][7][8]. Thus, other potential applications for MMC include flexible alternating current transmission systems (FACTS), photovoltaic generation, wind turbine applications, electric drives, static var compensation (STATCOM), frequency converters and battery energy storage systems (BESSs) [5,7,8].…”

“…1 and it can be seen that every sub-module (SM) is constructed with a half-bridge (H-bridge) cell. Despite the advantages above, the lack of DC-side short-circuit fault handling capability is one of the main drawbacks of the MMC [4,6,[9][10][11]. This is due to the employment of the H-bridge cell in each SM -which is susceptible to DC-side faults, where an uncontrolled current path is present during the DC-side fault and the only way to isolate the fault is by using circuit breakers [4,11].…”

Review of technologies for DC grids – power conversion, flow control and protection

“…2: High-level comparison selected hybrid converters (A≡ AAC, B≡ CMC-MMC, C≡ AFC-B converter, and D≡ hybrid converter with alternate common arm and director switches)[42,54,55,57,[110][111][112][113][114][115][116] …”