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This paper presents a new technique to detect the junction temperature of Silicon Carbide (SiC) MOSFET devices. The process of detection is based on injecting a high frequency/low amplitude sweep signal into the gate lead of a SiC device during its OFF-state period. A frequency response analysis is carried out to determine the variation in the impedance which is a function of temperature change. The...
In this paper, an improved control strategy for three-phase inverter is proposed, which ensures three-phase output voltage symmetry under unbalanced grid voltage. Firstly, the positive and negative sequence separation module is used to obtain unbalance output voltage and current during the grid faults. By calculating output power of the inverter, an improved P-ƒ, Q-U and Q-G droop control strategy...
In the conventional variable speed drive, the dc-link including the dc-choke and electrolytic capacitor is bulky with limited lifetime. The slim dc-link drive is thus proposed for the lower cost and longer lifetime by using the film capacitor to replace the electrolytic capacitor and dc-choke. However, such drive system suffers from the potential instability issue, due to the negative incremental...
This paper presents a division-summation (D-Σ) digital controlled three-phase four-leg voltage source inverter with load impedance estimation for uninterruptible power supply applications. The D-Σ digital control developed for current tracking can accommodate wide filter inductance variation, which has been successfully adopted in grid-tied applications. This paper proposes a load impedance estimation...
This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion with consideration of the inverter nonlinearities. Small current disturbance is injected into grid-connected inverter...
In the previous studies, it has been shown that the steady-state operation of a class-E resonant inverter can be rapidly simulated in the frequency domain by extending the concept and mathematical form of electrical impedance. This paper provides a more comprehensive solution for the efficient simulation of practical class-E resonant inverter, which is driven by a MOSFET switch. The parasitic components,...
DC power distribution gains popularity in future residential, renewable energy, transportation and data centers. Such dc system can be connected to ac system through bidirectional interface converter. Compared with isolated converters, transformerless solutions have the advantages of higher power density, efficiency, and lower cost. One concern about the non-isolated connection is the coupled common-mode...
Due to the high frequency nature and constant power load characteristics, stability issue exists widely in contemporary power electronic systems. Impedance-based criteria can be used in stability prediction. Thus, the accurate extraction of impedance becomes significantly important. For AC systems, impulse injection method has been proposed for its short measurement duration, but the accuracy needs...
Inverters in voltage control mode including droop control and virtual synchronous generator (VSG) are promising for interconnecting the renewable energy to the grid, which are both emulating the frequency and voltage regulating functions of synchronous generators through droop method. However, improper transient impact current and reactive power output are observed for inverters in voltage control...
This work will present a novel photovoltaic (PV) inverter with integrated short-term storage. The topology combines advantages of microinverter topologies, such as module-specific maximum-power-point tracking, failure-tolerance, safety due to limited voltages, modularity, use of low-cost low-voltage components such as silicon field-effect transistors (FET), and simple expandability, with those of...
The nonlinear loads in microgrid not only distort the voltage but also degrade the harmonic power distribution in a conventional droop-controlled microgrid. This paper starts with analyzing the trade-off between voltage total harmonic distortion (VTHD) and harmonic sharing effectiveness. A multi-framed droop controller is proposed to improve the harmonic power sharing without deteriorating VTHD by...
This paper proposes a design method of the wireless power transfer system which obtains high power and high efficiency by using LC filter circuit in the transmitting side. This study forcuses on the maximum efficiency point of impedance. In the simulation, the proposed design achieved 2.5kW output power with the efficiency of 73%. In the experiment, the proposed circuit achieved 1.8kW wireless power...
Cascaded DC converters are becoming widely used in DC distributed power system. When a DC converter is tightly regulated, it operates as a constant power load (CPL). In a cascaded system, instability problems usually occurs due to the negative incremental impedance characteristic caused by a CPL. In order to mitigate instability, this paper proposes a new approach by adding an additional stabilizer...
Researches to control water content of Polymer Electrolyte Membrane(PEM) are actively performed for increasing performance & durability of Fuel cell. This Research to control water content focused on measurement of PEM impedance. In this paper, The measurement system of PEM Impedance based on AC impedance method is proposed. Bi-directional DC/DC converter is designed to measurement of PEM impedance...
When a severe grid voltage sag has happened, the transient rush current caused by grid voltage sag can not be effectively suppressed by the voltage controlled grid tied inverter based on the conventional virtual synchronous generator(VSG) control. In order to improve the capacity of voltage controlled grid tied inverter to withstand power grid voltage sag, the paper proposes an enhanced robust strategy...
A newly proposed concept for CM impedance boosting has been developed and demonstrated. The impedance boosting is through a three-winding common mode(CM) choke with its auxiliary winding connected to an negative impedance circuit. However, in practical CM choke the imbalance of the windings will lead to impedance variations. The aim of this paper is to analyze these impedance variations. The DM and...
The well-known active power-frequency and reactive power-voltage amplitude droop control is widely used in the coordinated control of parallel inverters in microgrids. However, the dynamics of the conventional droop method is slow due to the low-pass filters used for power calculation purposes. Stability concerns also exist in the conventional droop method. This paper proposes a novel droop control...
An advanced co-phase traction power substation system based on the cascade- parallel converter was proposed in this paper, for addressing the power capacity problems of traction power substation and the problems of electrification phase, reactive power, negative sequence and harmonic in railway. The 3-level neutral point clamped (NPC) converter was used in power substation, while the converter was...
The microgrid can operate in grid-connected mode and islanded mode, and the parallel operation of inverters will be involved in both modes. However, due to the differences of output characteristic among various inverters, the load power can't be shared equally. As a result, some methods without communication lines such as droop control and VSG (virtual synchronous generator) control have been proposed...
This paper explores the interconnection of multiple microgrid with “tie-line”. Tie-line control can be managed to control the power flow from microgrid and voltage at respective microgrid buses at the point of interconnection. Formation of such DC microgrid cluster ensures higher reliability of power supply and flexibility to manage distributed energy resources and loads in the system. Two identical...
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