Inductive power transfer (IPT) for Electric Vehicles (EVs) is an emerging technology that can transfer power wirelessly over certain distances, thus offering some remarkable characteristics in terms of flexibility, position and movability. The output power of an IPT system depends on the coupling factor of the magnetic couplers which can deviates from the nominal operating conditions due to occurrence of misalignment. Nevertheless, misalignment of the magnetic couplers in inductive charging is inevitable, and it usually results in the variation of the mutual inductance and output power of the system with corresponding decrease in the system overall efficiency. So far, the literature has reported various techniques for achieving designs with higher misalignment tolerance. The reported techniques can be mainly classified into three categories, as viewed from the following aspects: magnetic couplers layouts, compensation networks and control strategy. Each of these techniques has its pros and cons in terms of implementation cost, system layout, efficiency, power density and reliability depending on the application. With the increased investigation of more applications of IPT, new modified techniques of improving the misalignment tolerance in the IPT system are continuously being proposed based on permutations and combinations of the existing ones; thus causing some confusion and difficulties for researchers and system vendors to follow. This paper, therefore, aims to provide a comprehensive review of the existing methods for IPT systems that address the misalignment issue in EVs wireless charging. A review of the IPT system is presented and an investigation of the numerous factors affecting the output power and performances of the system when the coils are not aligned. In addition, the advantages and disadvantages of each technique on the IPT system's performance are analyzed in detail.

Circulating current has been an inherent feature of modular multilevel converters (MMC), which results in second-order harmonics on the arms currents. If not properly controlled, the circulating current can affect the lifetime and reliability of a converter by increasing the current loading, loss distribution, and junction temperature of its semiconductor devices. This paper proposes controlled circulating current injection as a means of improving the lifetime and reliability of an MMC. The proposed method involves modifying the reference modulating signals of the converter arms to include the controlled differential voltage as an offset. The junction temperature of the semiconductor devices obtained from an electro-thermal simulation is processed to deduce the lifetime and reliability of the converter. The obtained results are benchmarked against a case where the control method is not incorporated. The incorporation of the proposed control method results in a 68.25% increase in the expected lifetime of the converter and a 3.06% increase on its reliability index. Experimental results of a scaled down laboratory prototype validate the effectiveness of the proposed control approach.

This paper first outlined the motivation behind solid state transformer (SST) against conventional line frequency transformer (LFT) as well as its functional futures and benefits and secondly explore all the possible configurations of SST in terms of circuit configurations, advantages, disadvantages and their potential areas of applications. Four circuit configurations considered in this paper include; single stage SST, two stage SST with low voltage DC link (LVDC), two stage SST with high voltage DC link (HVDC) and three stage SST. Our findings reveals that apart from providing voltage regulation, SST can provide other additional ancillary services to the grid to enable it cope with transients. These services (such as power quality improvement, fault isolation, instantaneous voltage regulation, active and reactive power compensation) are not offered by LFT, as such SST is considered as the potential transformer in smart grid applications, renewable energy integration, modern traction systems and other applications where space and volume are critical.

Grid operators and wind farm vendors often employs multiple circuitries including but not limited to line frequency transformer (LFT), static synchronous compensator (STATCOM) and power factor correction (PFC) devices for grid integration of wind farms. Such components are usually heavy, noisy and causes greenhouse effect. The bulky power transformers for both STATCOM and the wind farm generator hinders this configuration from applications where volume and weight are issues. As such, STATCOM-interfaced wind farm cannot be sited where size, weight, compactness, cable solution, multiport capability and environmental friendliness are critical. This paper demonstrate how solid state transformer (SST) replaces the STATCOM, the bulky transformers, and the additional reactive power compensation devices in grid integration of wind farms thereby providing smaller footprint, compactness and high performance. It is concluded that, SSTinterfaced wind farms can be sited anywhere because of the reduced size, weight, compactness, cable solution, multiport capability and environmental friendliness.