A Novel Modulation Function-Based Control of Modular Multilevel Converters for High Voltage Direct Current Transmission Systems

Abstract

Abstract:In this paper, a novel modulation function-based method including analyses of the modulation index and phase is proposed for operation of modular multilevel converters (MMCs) in high voltage direct current (HVDC) transmission systems. The proposed modulation function-based control technique is developed based on thorough and precise analyses of all MMC voltages and currents in the a-b-c reference frame in which the alternating current (AC)-side voltage is the first target to be obtained. Using the AC-side voltage, the combination of the MMC upper and lower arm voltages is achieved as the main structure of the proposed modulation function. The main contribution of this paper is to obtain two very simple new modulation functions to control MMC performance in different operating conditions. The features of the modulation function-based control technique are as follows: (1) this control technique is very simple and can be easily achieved in a-b-c reference frame without the need of using Park transformation; and (2) in addition, the inherent properties of the MMC model are considered in the proposed control technique. Considering these properties leads to constructing a control technique that is robust against MMC parameters changes and also is a very good tracking method for the components of MMC input currents. These features lead to improving the operation of MMC significantly, which can act as a rectifier in the HVDC structure. The simulation studies are conducted through MATLAB/SIMULINK software, and the results obtained verify the effectiveness of the proposed modulation function-based control technique.

A Novel Protection and Location Scheme for Pole-to-Pole Fault in MMC-MVDC Distribution Grid

“…A Modular Multilevel Converter (MMC) usually has a large number of sub-modules [5]. To improve the quality of converter output waveform, nearest level modulation (NLM) method has been widely adopted [6].…”

A Switching Frequency Optimized Space Vector Pulse Width Modulation (SVPWM) Scheme for Cascaded Multilevel Inverters

“…They are widely used in medium voltage motor driver [3], high-voltage direct current (HVDC) transmission systems [4], static var generator (SVG) [5], active power filter (APF) [6] and other applications [7,8]. Several topologies for multilevel inverters have been proposed in the past decades, including diode-clamped [9], flying capacitor [1], cascaded H-bridge [10] and modular multilevel [11]. For a given multilevel converter topology, modulation scheme is a key factor [12][13][14][15][16][17].…”

Research on Unbalance Fault-Tolerant Control Strategy of Modular Multilevel Photovoltaic Grid-Connected Inverter

“…Lots of research has been conducted to find effective control methods for MMC topology [5][6][7]16,17]. Reference [5] proposes a control method based on a dynamic model, where six independent dynamical state variables are considered for effectively attaining the switching state functions of MMCs, as well as for an accurate control of the circulating currents.…”

“…With its unique advantages of decentralized energy storages, modular structure, easy redundant SMs (SMs), simple fault identification, and clearance [5], MMC has been widely applied at various levels of power converters, such as high-voltage direct current (HVDC) transmission systems [6,7], DC-DC power electronic transformers [8], battery electric vehicles [9], distributed energy resources (DERs) [10,11], and flexible AC transmission systems (FACTS) [12]. Considering the long-existing issues of low utilization rate of light energy and potential influence on power grid in photovoltaic (PV) grid-connected system, the application of MMC in PV grid-connected systems is gaining more and more attention [13][14][15].…”