Research on dynamic current sharing method of parallel connected IGBT modules for NPC three level converters

The parallel connection of IGBTs has been being applied in high power neutral point clamped (NPC) three level converters. This paper investigates the impact of gate parameters (gate resistor and capacitance) on dynamic current imbalance of parallel connected IGBT for NPC three level converter. A gate parameters calculation method is proposed in the paper, and the delay time and collector current difference can be analysed quantitatively. Experimental results have shown the effectiveness of the method.

Surface-Mounted Smart PZT Sensors for Monitoring Damage Using EMI-Based Multi-Sensing Technique

In this article, a multi-sensing technique on surface-mounted PZT sensors is proposed. The investigation was performed on concrete structures to detect and localize structural damage. Multiple smart sensing units (SSU) were adhesively bonded on the top surface of a concrete beam. As each PZT sensor features a small zone of influence, the use of multiple smart sensors is recommended for effective damage detection. The conductance signatures were obtained at different stages in the frequency range of 0–450 kHz. This article also presents an effective methodology for damage localization, which assumes the parallel connection of SSUs in MISO mode. The methodology adopted for structural damage detection is effective, as it is verified by the experimental results performed on concrete structures with multiple surface-mounted PZT sensors.

Influence of local shadow on output of photovoltaic array

This paper first deduces the engineering mathematical model of photovoltaic cells, then builds the photovoltaic cell and photovoltaic array model in Matlab/Simulink, and then simulates and compares the output of photovoltaic array under the condition of series and parallel connection, the number of shadows and shadow distribution. Finally, the different effects of shadow in series and parallel and the influence of shadow distribution on the output of photovoltaic array are analyzed.

Performance of Parallel Connected SiC MOSFETs under Short Circuits Conditions

This paper investigates the impact of parameter variation between parallel connected SiC MOSFETs on short circuit (SC) performance. SC tests are performed on parallel connected devices with different switching rates, junction temperatures and threshold voltages (VTH). The results show that VTH variation is the most critical factor affecting reduced robustness of parallel devices under SC. The SC current conducted per device is shown to increase under parallel connection compared to single device measurements. VTH shift from bias–temperature–instability (BTI) is known to occur in SiC MOSFETs, hence this paper combines BTI and SC tests. The results show that a positive VGS stress on the gate before the SC measurement reduces the peak SC current by a magnitude that is proportional to VGS stress time. Repeating the measurements at elevated temperatures reduces the time dependency of the VTH shift, thereby indicating thermal acceleration of negative charge trapping. VTH recovery is also observed using SC measurements. Similar measurements are performed on Si IGBTs with no observable impact of VGS stress on SC measurements. In conclusion, a test methodology for investigating the impact of BTI on SC characteristics is presented along with key results showing the electrothermal dynamics of parallel devices under SC conditions.

Modeling Battery Connections in the Electronic Lab

The paper deals with the modeling of the processes of charge-discharge of battery assemblies taking into account their degradation. The results of simulating the cyclic operation of battery assemblies in the Electronics Workbench electronic laboratory are presented, possible schemes of inclusion are given, and options for re-switching batteries during operation are considered as well as connecting additional elements to extend the life of the connection. The simulation took into account the presence of one defective battery in the assembly. The operation of the assembly with a defective battery and a reference battery was compared. As a result of the analysis of parallel-serial and serial-parallel battery connections, the first one is considered preferable. For an assembly with a parallel-serial connection, the time parameters of operation remained almost unchanged, but the differences in the voltages of the defective and other batteries changed more than twice as compared with a serial-parallel connection. The changes in charge, voltage and current of assemblies with a degraded battery and a reference battery are analyzed. Timing diagrams are shown for batteries connected in parallel and in series with defective batteries. Power losses in a defective battery are reduced by choosing a parallel-series assembly, while switching a connection from a serial-parallel connection to a parallel-series one does not lead to compensation for the degradation of battery parameters. Changing the switching time intervals in a wide range does not contribute to increasing the capacity of a defective battery. Degradation of battery parameters leads to sharper surges in voltage, charge and current. The additional power recharge of the defective battery maintains the performance of the entire assembly. Recharge can be performed by connecting in parallel a defective additional battery or a capacitor, which is equivalent to replacing a degraded battery with a new one.