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Enhancing power cycling capability of power semiconductor devices is highly demanded in order to increase the long-term reliability of multilevel inverters. Ageing of power switches and their cooling systems leads to their accelerated damage due to excess power losses and junction temperatures. Therefore, thermal stresses relief (TSR) is the most effective solution for lifetime extension of power...
Among various converters, the LLC electric current resonant converter attracts attention because of high power density, low noise and high efficiency. However, this converter cannot apply the analysis of averaging method, and impossible to derivate the transfer function, so designing is difficult. In this study, we devised a method to derive a frequency response characteristic with a transfer function...
Multilevel Inverters play key role in grid integration of photovoltaic (PV) systems. Although power semiconductor devices in multilevel inverters represent the most expensive and vulnerable parts according to the recent reliability surveys. Thermal stresses in power semiconductor devices represent the main cause of their failures. Therefore, improved controllers with lower thermal stresses are highly...
This paper focuses on zero-crossing spike current issue in totem-pole bridgeless PFC converter. Spike current occurs at every input voltage zero-crossing and becomes a severe conducted common mode noise source. The zero-crossing issue is discussed by theoretical analysis and mathematical calculation, the conducted noise caused by zero-crossing issue can be predicted by calculating Fourier coefficient...
This paper analyzes the conducted noise generation mechanism of totem-pole bridgeless PFC converter in consideration of frame ground capacitor and LISN at every input voltage zero-crossing. The spike current occurs at zero-crossing and causes severe common mode noise. The frequency range on noise spectrum caused by zero-crossing issue is discussed by mathematical calculation. Furthermore, the experimental...
This paper presents a unified space vector modulation (SVM) algorithm for lifetime prolongation of thermally-overheated power semiconductor devices in multilevel inverters. Thermal overheating is the main cause of shortened-lifetime and open-circuit faults of the devices. Power semiconductor devices are subjected to thermal overheating due to their ageing that results from continuous overloading and...
Two feedback active damping technique for LCL filter resonance is proposed using the capacitor voltage and the grid current. The proposed method is derived in continuous time domain with discussion for its discrete implementation. Based on the proposed method, excitation of un-stable open loop pools, which implies non-minimum phase behavior, can be avoided over a wide range of resonant frequencies;...
This paper proposes a new active damping method for LCL filter resonance. The proposed method employs a dual feedback loop of the capacitor voltage and the grid current. Based on the proposed method, non-minimum phase behavior can be avoided over a wide range of resonant frequencies. Co-design procedures for both the active damping loops along with the fundamental current regulator are introduced...
Active damping of grid-connected LCL filter resonance by means of an observer loop to estimate the capacitor current is a well-known method. However, with variation of the grid side inductance due to grid conditions, the system robustness has to be checked. This work discusses the effect of the observer design on the system robustness against grid side inductance variation. Different values of resonant...
The common mode (CM) noise mechanism of totem-pole bridgeless PFC converter is analyzed in this paper. The conducted noise performance of a bridgeless totem-pole PFC converter using GaN HEMTs is investigated under experimental conditions: 230V ac input, 390V dc output, and 50kHz switching frequency. The CM noise located around the input voltage zero-crossing of the converter is noticed to be significant...
In order to develop a new style drill for the factories, the ultrasonic spindle was designed. Rotary transformer was introduced to solve the design problems existing in the specification and structure. However, rotary transformer's voltage conversion ratio is markedly lower than the inductance ratio, it cannot transmit sufficient electric power to the ultrasonic element. Then, this problem is being...
This paper proposes an efficient neutral point control algorithm for three level T-type inverters. The proposed algorithm helps to get balanced neutral point voltage with high efficiency steady state operation. The proposed controller relies on using the hysteresis control for DC link capacitors' voltage balancing. The proposed algorithm is implemented by adjusting the type of redundant small vectors...
Since the loss of input rectifying diode bridge in the conventional PFC converter reduces the efficiency, the bridgeless PFC converter has been proposed. The totem-pole bridgeless PFC converter is the most representative one. However the common mode noise current occurring around the input voltage zero-crossing brings severe EMI problem restricts its practical application. In order to improve noise...
LCL filters are widely used for grid-connected converters because its superiority over L and LC filters, however the resonance problem produced by these filters requires a more effort in the design process to damp it. Active damping techniques which use the sensed capacitor current are widely used in this regard to solve this problem; however this requires an increase in the number of sensors. Based...
PWM converters are widely used to connect the distributed energy sources to the grid. LCL filters are widely used for these converters because its superiority over L and LC filters, however the resonance problem produced by these filters requires a more effort in the design process to damp it. Active damping techniques which use the sensed capacitor current are widely used in this regard to solve...
Optimal techniques for power supply with transient current circuit are introduced in this paper. The circuit reduces switching loss of buck converter's main switch effectively. However, in our previous researches, it could be operated with high efficiency only at heavy loading. The techniques to get rid of this disadvantage are proposed and the validity of it is verified through experiments.
Since the loss of input rectifying diode bridge in the conventional PFC circuit reduces the efficiency, the bridgeless PFC circuit has been proposed. However, the performances of EMC in some bridgeless PFC circuits are unsatisfactory. In order to improve noise performance, the noise mechanism should be investigated as the first step. In this study, common mode noise current of conventional bridge...
In recent times, more than 60 percent of the world's energy is used to drive electric motors. Because of the growing requirements of speed control, pulse width modulated (PWM) inverters are widely used in adjustable speed drives. Noise generated by PWM inverter fed AC motor drive systems causes severe parasitic current problems, especially at the cases of high frequency. This paper proposes two new...
In renewable energy systems such as the PV system, the batteries are connected to ensure a stable supply of energy. Therefore, the bi-directional power conditioners have a key role in renewable power systems. In this paper, bi-directional LLC resonant converter as the power conditioner is proposed. The ac analysis and operating characteristics of bi-directional LLC resonant converter are investigated.
In DC power supply system, a fast response circuit breaker is required. Semiconductor DC circuit breaker is an important key technology in DC power supply system. This paper considers the malfunction issue of Silicon Carbide-Static Induction Transistor (SiC-SIT) based DC circuit breaker in DC power supply system. The malfunction mechanism is explained, and a solution methodology proposed. Investigations...
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