Sensorless voltage balancing method for modular multilevel converter

Abstract

Modular multilevel converters (MMCs) have become prominent for high and medium power applications. The phase-disposition pulse width modulation (PDPWM) technique is a carrier-based method that generates good quality output. However, it has the inherent problem of uneven power distribution. Conventionally, this is solved by expensive voltage and current measurements. In this paper, a capacitor voltage balancing method is presented for MMC, which eliminates the need for voltage and current sensors. It also ensures uniform power distribution among the submodules (SMs). In addition, it needs only one carrier per phase, and one PWM reference, for either upper arm or lower arm to produce N + 1 level with N SMs per arm. The capacitor voltage balancing method is analyzed mathematically and verified for the MMC with two-level half-bridge SMs. The same method is also extended to the MMC with three-level flying capacitor SMs. MATLAB/SIMULINK simulations and experimental results on a laboratory prototype are presented to verify the theoretical concepts. K E Y W O R D Smodular multilevel converter (MMC), sensorless voltage balancing, single-carrier PWM, three-level flying capacitor submodule (3L-FCSM)

An improved method to sub‐module voltage balancing in modular multilevel converters with two voltage sensors

“…these methods varies from 1.72 to 10 kHz. Recent studies [34][35][36] try to eliminate all sensors in the MMC and regulate capacitor voltages using a different Sub structure or modulation strategy. Even though these methods eliminated all sensors, they did not account for the extra properties in Table 4.…”

“…Recent studies attempt to control MMC without sensors by using various Subs structures and modulation methods. [34][35][36] These new control methods effectively eliminate all of the arm's sensors from the MMC, but they are unable to detect Subs' open-circuit faults.…”

“…This method reduces the number of Subs needed in the MMC to reach the same voltage levels; however, a three‐phase system requires many sensors. Recent studies attempt to control MMC without sensors by using various Subs structures and modulation methods 34–36 . These new control methods effectively eliminate all of the arm's sensors from the MMC, but they are unable to detect Subs' open‐circuit faults.…”

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

“…To do this, carrier waveforms are required. However, the single carrier modulation scheme eliminates the need for the multi‐carrier generation regardless of the SM number 19,27 . This scheme is detailed with N = 4 as follows.…”

Decoupled and compensated space vector pulse width modulation algorithm for dual‐channel PMSM with unbalanced power supplies

“…In this manner, the reliability and efficiency of multiple low-power supplies can be greatly improved. In another word, the multi-channel PMSM can be well replicated in other applications, such as microgrid distribution and aerospace propulsion, [5][6][7] because the number of working phases can be dynamically regulated according to the actual demand.…”