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Power converter operation on high-impedance grids can result in oscillatory behavior as a result of “self-synchronization” of an inverter's phase detection unit (PDU). This phenomenon is particularly of concern in renewable energy applications and it occurs when the converter's injected current changes the voltage angle at the point-of-common coupling (PCC) and synchronizes to itself through its PDU...
Predictive pole-slip protection is not implemented in commercially available protection relays, since complex modeling of the network and generator is required to do such predictive detection. All pole-slip protection relays on the market will only trip a generator after it has pole-slipped one or more times. This paper introduces a pole-slip protection algorithm, which makes use of a simplified model...
In the DC power systems of More Electric Aircraft, the closed-loop controlled electrical motor drives and power electronic converters can be generally regarded as constant power loads (CPLs), and usually lead to negative impedance-related instability. Depending on Brayton-Moser's mixed potential theory, this paper adopts R parallel damping filters to stabilize the CPLs systems, and derives large signal...
This paper proposes an H∞ mixed sensitivity design of output current tracking controller in a stationary reference frame for general microgrid-tied inverter applications. Variations in a microgrid impedance values have been modeled as multiplicative uncertainty in the plant model. Equivalent microgrid voltage has been considered as the output disturbance acting on the plant. Particular weighting functions...
In this paper, we present an unstable phenomenon in cascaded systems that the source converter might become unstable after connected with the load converter though it can work stably individually. However, by staggering the switches' turn-on time between the source converter and load converter, it can become stable. Analysis in this paper shows that the essential reason for this phenomenon is that...
The stability of the cascaded power converters system is an important design consideration, since the interaction among the individual converters in the cascaded system can lead to the degradation of the system stability and dynamical performances, even make the system unstable. In this paper, the stability analysis methods for the cascaded power conversion system are reviewed at the beginning. Following,...
Cascaded Buck conversion system is a typical structure in dc distributed power system (DPS). It is known that, the interaction between its individually designed power modules/subsystems may cause the instability problem of the whole system. The traditional solution is to design this system by Middlebrook criterion. However, authors found that, even if the entire system meets Middlebrook criterion,...
Stability analysis of cascaded DC-DC converters systems is one of fundamental issues crucial to real-world power supplies applications. Existing techniques for stability analysis of cascaded converters systems are mainly based on Thevenin or Norton equivalents of two-port networks of sub-converters in which impedance-based stability criteria can be applied. In this work, further transformations of...
Advances in switching power electronic converter technology have brought about a resurgence of interest in the use of DC power distribution systems for a variety of applications. However, the notional power electronic based DC distribution system is a complex and extensively interconnected system consisting of multiple power converters. As a result, a number of system-level challenges related to stability...
Instabilities related to dc-side resonances can occur in Voltage Source Converters based HVDC (VSC-HVDC) systems due to undesirable interactions between its dc-transmission link and the VSC dynamics. Previous works have shown that this instability takes place when dc-side resonances coincide with non-passive behavior of one of the VSCs within the VSC-HVDC system, typically, the VSC that controls the...
Detecting the load currents is a basic control method of paralleled active power filter (PAPF). The stability and compensation effect of the system would be influenced by the interactions of the load, weak grid and the paralleled active power filter (PAPF), when the load can't be equivalent to an ideal harmonic current source. The impedance models are established to analyze the stability of the system,...
In this paper a unified Impedance-based Stability Criterion (UIBSC) has been proposed for paralleled grid-tied inverters. Compared to the traditional Impedance-based Stability Criterion (IBSC) which needs to evaluate all minor loop gains (MLGs) of each individual inverter, the UIBSC only checks the derived global minor loop gain (GMLG) once to determine system stability. As a result, the computation...
The interactions of more and more power electronics-interfaced power systems can worsen the power quality and the system stability in distribution networks. System stability can be addressed analyzing the source and load impedances at the interaction section and well-established approaches exist for DC and three-phase AC networks. Some papers focus also on single-phase AC systems, whose study is generally...
When multiple stable systems are combined into one system, the newly formed hybrid system has a certain possibility to be unstable. Such a natural phenomenon has been verified in the fields of chemistry and biology over the last century. The use of electric springs (ES), which must be implemented in large quantity over the power grids, can also suffer from the same issue if specified design are not...
The interaction between STATCOM and voltage-source inverter (VSI) may cause instability in an islanded micro-grid. Impedance models of storage battery power convert system (PCS) and cascaded multilevel static synchronous compensator (STATCOM) are established based on which the interaction mechanism between PCS and STATCOM is studied. Using Nyquist stability criterion and admittance ratio analysis,...
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