The phenomenon of phase unbalance is prevalent in the low voltage distribution grid due to the presence of single-phase loads. The unbalance can cause issues such as capacity underutilisation, transformer losses and problems with induction motors. To ensure the reliability of the upstream grid, it is important to maintain balanced three-phase power. This becomes more relevant with the proliferation of Distributed Energy Resources (DERs) and storage. This thesis explores the use of power electronic devices as a power redistributor.
To begin with, different topologies of a converter are discussed. These topologies have their own sets of advantages and disadvantages. Based on various operating and design parameters, a comparison between these topologies is made.
Subsequently, different control strategies for the converter are analysed. Among these, the current control strategy ensures supply of balanced and sinusoidal current to the loads with low computational burden, and is hence chosen. This strategy involves the control of sequence components independently in the double synchronous reference frame.
Low-frequency harmonics occur in the DC-link as a result of the compensation of negative-and zero-sequence components by the converter. The magnitude of this low-frequency harmonic and the overall harmonic Root Mean Square (RMS) current in the DC-link are derived mathematically and validated by simulations to represent this converter. It is observed that the DC-link sizing is mainly dependent on the low-frequency harmonics and thus, their accurate estimation will help in better sizing of the DC-side components.
The various configurations of the converter under consideration are benchmarked against each other on parameters such as Total Harmonic Distortion (THD), Power Losses, and DC-Link Sizing.

The need for proper fast charging infrastructures is one of the key challenges for the wide adoption of elec- trical vehicles (EV). The high pulsating demand of fast charging stations (FCS) together with high demand tariffs can cause monthly DSO demand charges to account for a significant fraction of a station’s electric bill. Therefore, weakening the business case for stations located in these high tariff regions. To tackle this issue, demand charge management (DCM) can be applied to suppress peak power demands at FCSs using battery energy storage systems (BESS). This enables the reduction of cost while retaining the station’s fast charging capabilities. However, the implementation of such systems remains a large investment and the proper BESS sizing in fast charging applications is not well studied. This thesis proposes a multi-objective approach for optimal BESS sizing at FCSs considering demand charges and station performance. A BESS assisted FCS model is formulated to analyse the performance of a station’s design based on power flow, charging delays and the expected BESS lifetime. Furthermore, based on a worst-case demand scenario, a multi-objective optimization framework is formulated using the genetic algorithm NSGA-II to obtain the optimal BESS and grid-tie sizing for an existing FCS. Lastly, with demand data measured at four FCSs in the Netherlands, a set of numerical case studies has been conducted in the Mosaik and Pymoo environments to assess the feasibility and the effectiveness of the proposed formulation. These case studies provide new insights on the demand charge reduction and optimal sizing regarding dif- ferent station characteristics, BESS prices, and demand tariffs. These insights show how the FCS utilization rate and installed capacity can effect the optimal BESS sizing and how different demand tariffs or BESS cost can result in different optimal power to energy (P/E) ratios, and thus affecting the performance of a BESS.