A level enhanced voltage balancing method for modular multilevel converter without using sensors

Abstract

The intrinsic characteristics such as modular structure, filterless operation, and absence of DC-link capacitor have made the modular multilevel converter (MMC) superior to the conventional multilevel converters. However, the submodule (SM) capacitor voltage balancing is crucial. This paper presents a voltage balance control method for MMC. The proposed method generates 2N + 1 levels (where N is the number of SMs per arm) which halves the step size of output voltage and improves the harmonic performance as compared to N + 1 level generation. It requires only one carrier per phase and no voltage and current measurements are needed for the implementation. Therefore, the proposed method makes the system cost-effective and reduces the implementation issues related with carrier-based methods substantially. It also alleviates the non-uniform charge distribution problem with the phase disposition pulse width modulation (PDPWM) technique. Further, a detailed mathematical analysis is presented which enhances the understanding of balancing algorithm. In addition to this, the circulating current with 2N + 1 modulation is analyzed and a control technique is presented. The proposed voltage balancing method is simulated comprehensively in MATLAB/SIMULINK software and validated by the experimental results obtained from a laboratory prototype.

A new generalized predictive current control algorithm with integration of fractional part function based modulation technique: Single phase self‐balanced type multilevel inverter topologies

“…It gives many advantages as compared with other conventional SCPWM techniques. [26][27][28][29][30][31][32] The basic definition of FPF is nothing but a difference between the reference signal (RS) and the floor of the reference signal. The FPF function can also be represented as {RS} mathematically expressed in (1).…”

“…It is nothing but the mimic switching behavior of the LS‐PWM technique, and it provides the best harmonic performance. It gives many advantages as compared with other conventional SCPWM techniques 26–32 . The basic definition of FPF is nothing but a difference between the reference signal (RS) and the floor of the reference signal.…”

“…A generalized hybrid PWM approach for asymmetrical cascaded type MLI topologies has been suggested in Tammali et al 25 The SCPWM approach with rem and floor functions has been suggested to supervise the MMC. 26 The SCPWM template for CHB-MLI topology with two unity-offset sinusoidal signals and floor function has been disclosed in Odeh et al 27 The SCPWM technique for MMC with the use of the floor function has been demonstrated in the literature, 28,29 and it is a modified version of the techniques in previous works. 26,27 In Lingom et al, 30 a generalized SCPWM technique with the abs function has been stipulated, but its implementation needs more mathematical expressions and ifelse loops.…”

A modified modular multilevel converter to reduce the second order ripples in the submodule capacitor voltage: Design and analysis

“…The most appealing topology for the High Voltage DC transmission system is the modular multilevel converter (MMC) 1 . Interestingly, MMCs also have displaced traditional converters in many high‐power and medium‐power applications, for example, motor drive systems 2,3 because of their ability to perform transformer‐less ac‐dc and dc‐ac conversions with lower harmonic pollution and improved efficiency 4 . Depending on the application, MMCs structure is constructed by utilizing SMs such as half‐bridge and full‐bridge SMs and also many other SMs are preferred 5 …”