Switching pulse pattern optimisation for modular multilevel converters

• Modular multilevel converters (MMCs) are widely used in different applications such as high voltage direct current (HVDC) applications. The HVDC station loss is highly related to the converter switching pulse pattern which is generated by modulation algorithm and cell selection methods. This paper formulates the switching pulse pattern generation, as a versatile optimisation problem. The problem constraints and objectives are formulated for HVDC applications and compared with similar problems in the field of computer science. To overcome the computational complexity in solving the introduced optimisation problem, a heuristic method is proposed for cell selection algorithm. The method utilizes the current level in order to obtain lossless switching at zero-current crossings. The study of the proposed method, in a time-domain simulation platform, shows that the method can reduce the switching converter losses by 60% compared to carrier-based modulation, maintaining the same capacitor voltage ripple. Although this paper focuses on HVDC, the mathematical model is applicable for any MMC application.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Nyckelord

HVDC power convertors

PWM power convertors

computational complexity

heuristic programming

losses

optimisation

switching convertors

time-domain analysis

zero current switching

HVDC station loss

MMC application

capacitor voltage ripple

carrier-based PWM algorithm

cell selection methods

computational complexity

computer science

converter switching pulse pattern generation optimisation

current level utilization

heuristic method

high voltage direct current applications

mathematical model

modular multilevel converters

switching converter losses reduction

time-domain simulation platform

zero-current crossings

Capacitors

HVDC transmission

Optimization

Switches

Switching loss

Tin

Voltage control

HVDC transmission

Power conversion

Switching frequency

Switching loss

SRA - Energy

SRA - Energi

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