Danjiang Chen

Monitoring the wall temperature of gasifiers in the chemical industry can not only timely detect hot spots and avoid accidents, but also predict the thinning degree of refractory bricks and optimize maintenance cycles. In order to achieve distributed temperature measurement, this paper studies a distributed temperature monitoring system for gasifiers based on optical fiber sensors. The system includes four parts: on-site high-temperature resistant temperature sensors, network transmission system, temperature monitoring host, and temperature monitoring analysis software platform. The experimental results indicate that this system can achieve real-time measurement of the temperature in different areas of the gasifier wall.

Three-level T-type inverters have lower total harmonic distortion in output voltage, higher power density and lower voltage stress of power switches compared with conventional two-level inverters and have been widely used in applications with a wide-power range. Reliability improvement is particularly important for the T-type inverters because of the increased number of power switches and high system complexity. This paper proposes a fault-tolerant topology, which is constructed by adding a redundant leg including halfbridge switches and neutral-point switches connected between the DC bus capacitors and the DC-link midpoint of the conventional T-type inverter. In addition, an after-fault control strategy is proposed based on the results of a fault diagnosis method using bridge voltage. The fault-tolerant control of the open-circuit fault of the power switches and the phase-leg fault can both be achieved by the proposed method. Experimental results are given to verify that the proposed fault-tolerant three-level T-type inverter can output the full voltage level and power during the fault-tolerant operation based on the proposed control strategy.

Multilevel inverters have been widely used in various occasions due to their advantages such as lowharmonic content of the outputwaveform. However, because multilevel inverters use a large number of devices, the possibility of circuit failure is also higher than that of traditional inverters. A T-type three-level inverter is taken as the research object, and a diagnostic study is performed on the open-circuit fault of insulated gate bipolar transistor (IGBT) devices in the inverter. Firstly, the change of the current path in the inverter when an open-circuit fault of the device occurred, and the effect on the circuit switching states and the bridge voltages were analyzed. Then comprehensively considered the bridge voltages, and proposed a fault diagnosis method for a T-type three-level inverter based on specific fault diagnosis signals. Finally, the simulation verification was performed. The simulation results prove that the proposed method can accurately locate the open-circuit fault of the inverter device, and has the advantage of being easy to implement.

Multilevel inverter topologies have been widely used in applications of wide‐power range. Therefore, fault diagnosis of such circuits is becoming more and more important. The T‐type topology, which is one of many multilevel topologies, has an advantage in terms of efficiency compared to the neutral‐point‐clamped type. This study proposes a new diagnosis method of an open‐circuit (OC) fault for a three‐level T‐type inverter (3LT ² I). The proposed method is achieved by measuring the bridge voltage and its duration time. The bridge voltage includes information of switching states of 3LT ² I but not affected by the load. First, according to polarity of the reference voltage and corresponding phase current, working period of the 3LT ² I is divided into four working regions. Then, the bridge voltage is analysed in detail when an OC fault occurs in different working regions. At last, a fault diagnosis circuit is designed to achieve automatic diagnosis for the OC fault. Simulation and experimental results show that the proposed method can identify the faulty switch exactly and quickly.