This paper presents a comparison of conventional single-phase water/glycol liquid and innovative two-phase cooling technology for thermal management of high power electronics automotive IGBT modules during full drive cycle. The proposed two-phase cooling system is built using conventional automotive air conditioning components (condenser, expansion valve, compressor, and vapor and liquid lines) and conventional cold plate as used for single-phase cooling, thus the design does not require the development of new technology for its implementation. 3-D numerical simulation in COMSOL and experimental results of two-phase cooling have been obtained on a prototype and compared to conventional water/glycol cooling high power electronics modules, with considerable improvement on working temperature, power transfer capacity and equalization of die temperatures during a full driving cycle. These results suggest that two-phase cooling using the same cold plates as in single-phase cooling can be used to substantially improve the performance and reliability, of EV power converters without major changes.

Selective harmonic elimination - pulse width modulation (SHE-PWM) can be utilized to improve the efficiency of multilevel voltage source converters due to its ability to provide low switching frequency and tight control of low-order harmonics. In addition, SHE-PWM with half-wave (HW) symmetry provides a higher number of solutions than quarter-wave (QW) symmetry and therefore, the waveform design can be improved. This work proposes a universal formulation, which can be utilized with HW symmetry, that provides a unique system of equations valid for any possible multilevel waveform. Thereby, without using predefined waveforms, this formulation provides the ability to search simultaneously both the firing angles and the switching patterns, simplifying significantly the search process and providing a high number of solutions. With the aim of selecting the optimum sets of firing angles, the solutions provided by HW and QW symmetries are compared, based on several metrics of harmonic performance, for particular test cases. Experimental results also validate the universal formulation with HW symmetry.

Modular multilevel converters (MMCs) require control of the circulating current, i_circ, to improve their operation and efficiency. This is particularly important when low switching frequency modulation techniques, such as selective harmonic elimination (SHE-PWM) are applied. This work provides a novel method to control the circulating current along with (N+1) SHE-PWM. Unlike the case of (2N+1) SHE-PWM, explicit redundant levels are not available and, therefore, different modulation indexes, m_1 and m_2, are employed in the upper and lower arms to obtain the desired modulation index m_a. Unlike previous (N+1) circulating current methods, the distances between m_a, m_1 and m_2 remain constant to not disturb the phase output voltage, with an interchange of m_1 and m_2 between the arms used to follow the desired i_circ. The control adjusts the dc component of the circulating current and the energy stored in the SMs to their references, while maintaining the energy balance between the upper and lower arms. Simulation tests and experimental results, obtained from a single-phase laboratory prototype MMC, validate the proposed control technique.

Unmanned underwater vehicles (UUVs) are key technologies to conduct preventive inspection and maintenance tasks in offshore renewable energy plants. Making such vehicles autonomous would lead to benefits such as improved availability, cost reduction and carbon emission minimization. However, some technological aspects, including the powering of these devices, remain with a long way to go. In this context, underwater wireless power transfer (UWPT) solutions have potential to overcome UUV powering drawbacks. Considering the relevance of this topic for offshore renewable plants, this work aims to provide a comprehensive summary of the state of the art regarding UPWT technologies. A technology intelligence study is conducted by means of a bibliographical survey. Regarding underwater wireless power transfer, the main methods are reviewed, and it is concluded that inductive wireless power transfer (IWPT) technologies have the most potential. These inductive systems are described, and their challenges in underwater environments are presented. A review of the underwater IWPT experiments and applications is conducted, and innovative solutions are listed. Achieving efficient and reliable UWPT technologies is not trivial, but significant progress is identified. Generally, the latest solutions exhibit efficiencies between 88% and 93% in laboratory settings, with power ratings reaching up to 1–3 kW. Based on the assessment, a power transfer within the range of 1 kW appears to be feasible and may be sufficient to operate small UUVs. However, work-class UUVs require at least a tenfold power increase. Thus, although UPWT has advanced significantly, further research is required to industrially establish these technologies.

The DC-Link capacitor plays a crucial role as far as power density and reliability are concerned: it occupies approximately 40% of the inverter, and causes approximately 30% of its failures. Asymmetrical dual three-phase (ADTP) multiphase arrangements are gaining relevance in the automotive sector for powertrain applications. This work focuses on reducing the impact that the widely used double zero sequence injection (DZSI) family of PWM techniques have on such a bulky and failure-prone component in an ADTP arrangement by means of interleaving techniques. By using the double Fourier integral formalism, the input current spectra and the overall performance of these PWM techniques have been derived, in terms of current rms value and voltage ripple in the DC-Link capacitor. Simulations have shown that choosing an adequate interleaving scheme and angle considerably relieves both current and voltage stresses on the DC-Link capacitor compared to noninterleaved operation. Reductions of 84% current rms and 86% voltage ripple have been achieved at static operating points. Finally, by averaging the rms current over WLTP standard driving cycle, reductions up to 26% have been obtained under more realistic conditions. All this would enhance the reliability and reduce the size of the onboard capacitors in future electric vehicles.

Wide Bandgap (WBG) transistors provide better switching performance and higher operating temperatures compared to state of the art Si devices and are suited for high frequency applications due to very short switching times. The main obstacle for implementation of WBG transistors at full potential is the high frequency oscillation in voltage and current during switching transients. Oscillations arise from resonance due to parasitic and device inductances and capacitances. Introduction of WBG transistors depends on the elimination of these oscillations and their negative effect on the performance of power converters. Good layout practice is mandatory, but there is a limit to the reduction of these parasitics and, often, slowing of the semiconductor switching time must be applied. This paper presents a simple methodology for the attenuation of the negative effects of WBG transistor high frequency oscillations without increasing rise and fall times. The proposed methodology is based on determination of the source of feedback resonant frequency between gate and power loops using network analyzer measurement on PCB and utilization of tuned RLC filter. Experimental application of the methodology shows direct relationship between loop resonant frequency and voltage and current oscillations. The proposed method reduces power losses, high frequency oscillations and EMI.