The silicon carbide (SiC) MOSFET is characterized by high operating voltage, temperature, switching frequency and efficiency which enables a converter to achieve high power density. However, at high switching frequency, the crosstalk phenomenon occurs when the gate voltage spike introduced by high dv/dt and voltage ringing forces false turn-on of SiC MOSFET which causes a crow-bar current thereby increasing switching losses. In order to increase the immunity against the crosstalk phenomenon in a half-bridge configuration, this paper presents a gate driver for SiC MOSFET capable of generating the negative turn-off voltage without using a negative power supply. In addition, the effect of parasitic inductances on the switching response is analyzed and an RC snubber is designed using high-frequency based circuit reduction technique to dampen the switching ringing. The performance of the proposed gate driver and the designed RC snubber is validated using simulation and experiment at the 1 MHz switching frequency. The results show that the proposed gate driver with RC snubber eliminates crosstalk by maintaining any spurious gate spike below the gate threshold voltage.

A novel autotransformer configuration for 24-pulse rectification is proposed that not only maintains the desired power quality but also enables a reduction in autotransformer equivalent power capacity, therefore, lowering cost, volume and weight of the overall 24-pulse rectification system. The significances of the proposed autotransformer configuration are: easier implementation and have reduced windings per autotransformer core limb contrary to the established topology. The topology of the novel autotransformer is such that one of the four 3-phase rectifiers draws current directly from the input power supply instead of the autotransformer hence the power load on the autotransformer is significantly reduced. Higher pulse rectification systems are needed to be investigated because they comply with the stringent power quality standards defined by IEEE-519. The performance of the novel topology is compared with the well-established 24-pulse rectification system where the proposed system exhibit superior characteristics evaluated regarding power quality and simplicity. In this paper, the performance of both 24-pulse power converters is assessed through MATLAB simulations and validated through experimental prototypes.

With the evolution of the More Electric Aircraft (MEA) concept, high pulse converters have gained the attention of researchers due to their higher power quality. Among the high pulse converters, 18-pulse autotransformer rectifier unit (ATRU) offers better power quality level with small size, weight and medium complexity. The conventional topologies of autotransformers that require the use of extra elements such as Inter Phase Transformers (IPT) or Zero Sequence Blocking Transformers (ZSBT), adding to the complexity, weight and size of the overall system, are not considered in the analysis. For 18-pulse rectification, only those topologies of autotransformers which have the intrinsic current harmonic cancellation capabilities are presented here for comparison. These topologies offer current harmonic levels within limits specified by IEEE 519 with reduced weight and size as compared to the conventional multi-pulse converters. A comparison of different differential delta/fork configured 18-pulse autotransformer rectifier units is presented so as to come up with the best among available topologies with respect to weight, size and power quality. Experimental prototypes of each topology were designed and their results are displayed along with the simulation results for comparison.

The crosstalk phenomenon in a phase-leg configuration forbids the operation of SiC devices at high switching speed. A multilevel gate driver (MGD) is well-known for crosstalk mitigation, however, it requires two driver ICs and two voltage supplies to generate four different levels in the gate-source waveform. This paper presents a low-cost quasi-multilevel gate driver (QMGD) for crosstalk suppression which can be implemented on a single driver IC using only positive supply voltage. With a simple auxiliary circuit of the parallel-connected transistor, zener diode, and a capacitor, the proposed driver can generate multilevel output. The auxiliary transistor governs the charging and discharging of the capacitor, controlling voltage at the source terminal of SiC MOSFET and thus generating different voltage levels essential for crosstalk suppression. Performance of the proposed gate driver is validated through Spice based simulation as well as experimental tests conducted with Cree C2M0025120D. It is concluded that the proposed QMGD can replace a complicated MGD without any loss of performance.

In modern distributed energy systems (DES), focus is shifting from the conventional centralized approach towards distributed architectures. However, modeling and analysis of these systems is more complex, as it involves the interface of multiple energy sources with many different type of loads through power electronics converters. The integration of power electronics converters allows distributed renewable energy sources to become part of modern electronics power distribution systems (EPDS). It will also facilitate the ongoing research towards DC-based DES which is mostly composed of commercial DC-DC converters whose internal structure and parameters are unknown. For the system level analysis, the behavioral modeling technique is the only choice. Since most power electronics converters are non-linear systems and linear models can’t model their dynamics to a desired level of accuracy, hence non-linear modeling is required for accurate modeling. The non-linear modeling approach presented here aims to develop behavioral models that can predict the response of the system over the entire operating range. In this work, either a lookup table or a polytopic structure-based modeling technique is used. The technique is further applied to cascade and parallel connected converters, being two DES scenarios. First the procedure is verified via application to switching models in a simulation and then validated for commercial converters via experiments. The results show that the developed behavioral models accurately predict both the transient and steady state response.

Switching models possess discontinuous and nonlinear behavior, rendering difficulties in simulations in terms of time consumption and computational complexity, leading to mathematical instability and an increase in its vulnerability to errors. This issue can be countered by averaging detailed models over the entire switching period. An attempt is made for deriving improved dynamic average models of three phase (six-pulse) and nine phase (18-pulse) diode rectifiers by approximating load current through first order Taylor series. Small signal AC/DC impedances transfer functions of the average models are obtained using a small signal current injection technique in Simulink, while transfer functions are obtained through identification of the frequency response into the second order system. For the switch models in Simulink and the experimental setup, a small signal line to line shunt current injection technique is used and the obtained frequency response is then identified into second order systems. Sufficient matching among these results proves the validity of the modelling procedure. Exact impedances of the integral parts, in interconnected AC/DC/AC systems, are required for determining the stability through input-output impedances.