DC microgrid has attracted more and more attention due to its unique characteristics, but the development of DC microgrid is also facing some challenges, such as interruption and isolation of short circuit fault currents. Therefore, DC circuit breaker plays an important role in ensuring the normal work of DC microgrid. In this paper, a novel bidirectional DC solid-state circuit breaker is proposed to realize the bidirectional flow of energy, which ensures the higher operating efficiency of the DC microgrid. Compared with other solid-state circuit breakers, the proposed novel topology has simpler structure, common ground and fewer components. Firstly, this paper makes a detailed analysis of the different working stages of the circuit when the fault occurs in combination with simulation results of the circuit topology. Then, the standard of selecting the components through the calculation and analysis of the circuit is given in this paper. Finally, the performance of the novel bidirectional solid-state circuit breaker is verified by experiments.

Junction temperature is an important converter design/operation parameter as well as a significant indicator of device health condition. As compared to the Si counterparts, it is more critical for SiC devices due to the reliability concern introduced by immaturity of new material and packaging. This paper proposes a practical implementation using an intelligent gate drive for online junction temperature monitoring of SiC devices based on turn-off delay time as the thermo-sensitive electrical parameter. First, the sensitivity of turn-off delay time on the junction temperature for fast switching SiC devices is analyzed. A gate impedance regulation assist circuit is proposed to enhance the sensitivity by a factor of 60 in the case study with little penalty of the power conversion performance. Next, an online monitoring unit based on gate assist circuits is developed to monitor the turn-off delay time in real time with the resolution within hundreds of ps. As a result, the micro-controller is capable of “reading” junction temperature during the converter operation. Finally, a SiC-based half-bridge inverter is constructed with the intelligent gate drive consisting of the gate impedance regulation circuit and online turn-off delay time monitoring unit. Experimental results demonstrate the feasibility and accuracy of the proposed approach.

The development of the DC microgrid system on-board has promoted the development of the DC circuit breaker, due to that the short circuit fault may cause serious damage to the system. However, the traditional DC circuit breaker exists many problems such as long period of fault interruption, complex circuit structure, existing arc, low reliability and low anti-interference. Aiming to solve these problems, a novel solid-state DC circuit breaker was proposed in this paper. Firstly, this paper analyzes the working principle and process of the circuit in detail according to the results of the simulation based on Saber. Secondly, this paper gives the criteria on how to choose the parameters of the components correctly in the circuit. The concept of the maximum fault resistance according to the minimum fault current is also introduced. Moreover, this paper analyzes the influence of the minimum fault ramp rate on the circuit performance. Finally, experimental results verify that the performance of this novel solid-state circuit breaker agree with theoretical analysis.

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.

Based on color theory, a precise chromaticity coordinates tracking strategy for LED color-mixing system is proposed. The relationship between the resulting mixing color and the flux ratio of primary colors is derived according to center of gravity rule on CIE1931 chromaticity diagram. Based on this, the hysteresis control is introduced to minimize the color shift caused by aging and temperature effects without requiring any temperature sensor. A prototype with Red-Green-Blue (RGB) strings has been built and evaluated. The experimental results show that the luminous output can be controlled between 100lm and 600lm with an error within ±2%. Any chromaticity coordinate within the triangle enclosed by the points corresponding to RGB can be controlled accurately and the color distance between the output coordinate and the reference coordinate in CIE1976 is less than 0.007 over the whole color gamut.

Interleaved LLC resonant converters are widely used in various fields. However, interleaved LLC converters under Pulse Frequency Modulation (PFM) will lose the regulation of individual phases, causing a load sharing problem. Existing load sharing solutions have limitations; for example, phase shedding and current sharing cannot be realized at the same time. This paper proposed a novel current sharing method for interleaved full-bridge LLC resonant converters. Based on Zero-Vector-Injection, the voltage applied to the resonant tank is controlled to compensate for the difference in gain caused by component tolerance. The modulation strategy is proposed to maintain soft switching after Zero-Vector-Injection, and the phase shedding technique is also used to improve the efficiency at a light load. The detailed theoretical analysis and implementation method are proposed and validated using simulations. Experiments are also carried out to verify the feasibility of the proposed strategy based on a 2-phase 1.8 kW prototype.