Submodule Level Power Loss Balancing Control for Modular Multilevel Converters

Abstract

This paper investigates the power loss imbalance in Modular Multilevel Converters (MMCs) with Nearest Level Modulation (NLM) resulting from the low switching frequency operation and the parameter mismatch. The imbalance might pose a challenge to the cooling system design as well as the reliability of the MMC. To address this problem, a submodulelevel power loss balancing control (PLBC) is proposed. Compared with the normal control strategy without the thermal balancing, this method is able to decrease the degree of power loss imbalance among submodules (SMs) to at least half without deteriorating the performance of the converter efficiency and the capacitor voltage ripple. The effectiveness of the proposed control is validated by simulations.

Enhance Reliability of Semiconductor Devices in Power Converters

“…Thanks to this method, the most damaged cells can be preserved. Regarding MMC, this type of multilevel converter has received a great deal of study in terms of various aspects as output performance improvement [105][106][107][108], reduced computational burden [109][110][111], power losses balancing among SMs [104,112,113], etc. Due to the relatively large number of SMs, the ATC is usually conducted to achieve similar thermal stress distribution among the different SMs to enhance the lifetime of the power system [104].…”

“…A method proposed in [116] achieved SM thermal balancing by regulating the capacitor voltage of each SM in an arm while keeping the sum of the SM capacitor voltages at nominal value to control the dc-link voltage. As shown in Figure 22, the temperature of each SM 𝑇𝑇 SM,𝑖𝑖 is compared with the Regarding MMC, this type of multilevel converter has received a great deal of study in terms of various aspects as output performance improvement [105][106][107][108], reduced computational burden [109][110][111], power losses balancing among SMs [104,112,113], etc. Due to the relatively large number of SMs, the ATC is usually conducted to achieve similar thermal stress distribution among the different SMs to enhance the lifetime of the power system [104].…”

Analysing dynamics and synthesising a robust vector control for the dc‐voltage power port based on the modular multilevel converter in multi‐infeed AC/DC smart grids

“…Different technologies are being employed in MIACDC grids, among which the modular multilevel converter (MMC) is one of the emerging and pioneering technologies in the power electronics industry nowadays. In fact, among all converters' topologies, two-level and neutral-point-clamped (NPC) ones are giving ground to the MMC technology for various technical reasons as MMC has significantly been developed in the power industry [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

“…According to the space-phasor representation and control theory of voltage-sourced converters (VSCs), the instantaneous power of all different energy-storing components plays a key role in the whole dc-voltage dynamics -as per VSCs' control techniques (see [30][31][32][33] and references therein). Although both recent and early research works on grid-tied MMCs and their topologies/controls have conducted comprehensive studies associated with the operation and controls of these converters [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], none of them have proposed any control design strategy for the MMC-based dcvoltage power ports considering their robust operating. There is a need to synthesise a controller -which is able to optimally and robustly control the dc voltage by these highly emerging converters and assure both robust stability and performance.…”

Power Losses Control for Modular Multilevel Converters Under Capacitor Deterioration

“…However, it can not balance the power losses distribution among the SMs in the arm under capacitor deterioration. Reference [18] presents an SM level power loss balancing control for the MMC based on switching loss model, unbalance degree extractor, power level balancing control regulator and enable module. However, it only reduces the imbalance of the SM switching losses distribution in the arm.…”