The modular multilevel converter (MMC) is expected to be used extensively in high-voltage direct current (HVDC) transmission networks because of its superior characteristics over the line-commutated converter (LCC). A key issue of concern is balancing sub-module capacitor voltages in the MMCs, which is critical for the correct operation of these converters. The majority of voltage balancing techniques proposed thus far require that the measurement of the capacitor voltages use a reliable measuring system. This can increase the capital cost of the converters. This paper presents a voltage balancing strategy based on capacitor voltage estimation using the adaptive linear neuron (ADALINE) algorithm. The proposed estimation unit requires only three voltage sensors per phase for the arm reactors and the output phase voltages. Measurements of sub-module capacitor voltages and associated communication links with the central controller are not needed. The proposed strategy can be applied to MMC systems that contain a large number of sub-modules. The method uses PSCAD/EMTDC, with particular focus on dynamic performance under a variety of operating conditions.

This paper investigates the simulation of distributed wireless networked control systems (WNCS) over mobile ad-hoc network (MANET). The simulation model includes multiple plants with a single controller and random node mobility. The widely used network simulation software optimised network engineering tool (OPNET) has been utilised to implement a realistic wireless signal propagation model using path loss and fading effects. System performances for two ad-hoc network routing protocols: DSR and AODV have been explored.

A Multi-Terminal High Voltage Direct Current (MT-HVDC) network is being considered for utilising the full potential of offshore wind power whereas its realisation is currently being hampered by protection issues. In this paper, a protection strategy for future DC grids based on Modular Multilevel Converter (MMC) based HVDC system is presented. Firstly, a fault detection technique based on initial di/dt measurement is presented and thereafter protection strategies for future DC grids are presented. The fault detection technique presented is based on estimating the initial rate of rise of the current, IRRC (di/dt) at fault inception using measured data and thereafter calculating the line inductance. The calculated line inductance is compared with a setting value to determine whether or not a fault has occurred, thus paving the way for a distance protection strategy. Simulations were carried out using Matlab/SIMULINK for varying fault distances. The results obtained show the validity of the technique in detecting and locating DC side short circuits. An advantage of this technique is that it relies only on information from the local end terminal and as such, no communication channel is required, hence satisfying the protection requirement of fast fault detection and location technique for MT-HVDC systems.

MATLAB is a software simulator which is good for simulating the mathematical modeling and feedback control, while OPNET is a software tool which is good for simulating the network communication behavior. However, currently simulating the communication behavior of a wireless ad hoc network within MATLAB is difficult, where complex queuing models in OPNET are also difficult to create and manipulate. In this paper, we have created an interface between MATLAB and OPNET to allow MATLAB to use its strong mathematical functionality and OPNET to use its ability to manipulate network simulations.