Properties of reactive current injection by AC power electronic systems for loss minimization
01 Sep 2012-
TL;DR: In this article, the authors derived the mathematical condition for optimal share of both active and reactive currents for a single load connected to a network represented by its Thevenin equivalent, and analyzed the properties of reactive current control for system loss minimization under changing grid impedances and grid voltage.
Abstract: This paper derives the mathematical basis for analysing optimal injection of reactive current from power electronic interfaces, considering loss minimization in an AC system. The power electronic interface, working as load or generation, is modelled as constant power on the AC side, assuming a high bandwidth controller maintaining the DC-link voltage constant. Under these considerations the mathematical condition for optimal share of both active and reactive currents are derived for a system composed of a single load connected to a network represented by its Thevenin equivalent. The presented analysis is based on the active and reactive current components of the converter, which better suits a system in which the variables under control are the currents, in contrast to the classical power system approach in which active and reactive power are the variables under control. The derived mathematical expressions illustrate the properties of reactive current control for system loss minimization under changing grid impedances and grid voltage. An interesting property to be highlighted is the relation between power factor and minimum losses of the system: for the realistic case of non-zero grid impedance it is demonstrated how the widely accepted unity power factor approach is clearly not the optimal point of operation, neither from the grid perspective nor from the power electronics perspective.
Citations
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TL;DR: A method for real-time compensation of the unintended reactive power, which decouples the reactive power from the active power of a photovoltaic inverter, which outperforms conventional power factor control even when the conventional method is tuned optimally with known grid inductance.
28 citations
Cites background from "Properties of reactive current inje..."
...Unintended reactive power increases transmission losses, reduces the maximum transmission capacity, compromises system stability, and strains the grid with excessive reactive power requirements [31,30,21,38,36]....
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...Several studies have shown the localized reactive power compensation to be an effective and favorable method [21,31,33,39,5]....
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01 Oct 2012
TL;DR: The paper shows first that implementation of a virtual inductance is naturally suited for combination with Virtual Flux-based control systems, and that it can be extended to the more general case of avirtual reactance, and presents the structure of a control system for operation under unbalanced conditions.
Abstract: Conditioning of network impedance by insertion of a virtual inductance as an inherent feature of the converter control system has the potential to extend the range of stable operation of the overall system. This paper presents a scenario in which such potential is explored and its range of application is identified. It shows first that implementation of a virtual inductance is naturally suited for combination with Virtual Flux-based control systems, and that it can be extended to the more general case of a virtual reactance. The paper then presents the structure of a control system for operation under unbalanced conditions, where the virtual inductance directly influences the current reference calculation. Compared with the standard approach of unity power factor control of grid integrated converters, the suggested technique allows for improving the stability range of converters operating in high-impedance grids, and for remote point control of reactive power or power factor.
12 citations
Cites background from "Properties of reactive current inje..."
...5 pu, due to the destabilizing effects of the load, as analyzed in [24]....
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...This is because non-zero values of Virtual Inductance effectively results in reactive current injection from the converter to the grid, that will reduce the total current and the total losses of the radial line in a similar way as discussed in [24], while at the same time increasing the stability margin of the system....
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01 Jan 2005
TL;DR: In this article, the authors investigated whether the DG unit converters can contribute to reducing Harmonics, badly damped transients, and showed that for converters with conventional control this contribution is limited, and in some cases even negative.
Abstract: Anincreasing numberofDistributed Generation (DG)units isbeing connected tothedistribution network. Thisintroduces alarge numberofpower electronic converters. Due totheoutput capacitance of these andother convertersthere isarisk onharmonics, badly damped transients andsoon.Inthis paperit hasbeeninvestigated whether theDG unit converters cancontribute tothedamping inthegrid. The analysis showed that for converterswithconventional control this contribution islimited, andinsome casesevennegative. Additional controllers ontheDGunit converterareproposed thatwill significantly increase thedamping inthenetwork towhichitisconnected.
6 citations
01 Jan 2016
TL;DR: In this article, the performance of an active front-end (AFE) rectifier with direct and quadrature axis current control method was investigated and the PI controllers for that specific loop has been omitted to deal with the easy control of the controller.
Abstract: This work investigates the performance of an Active Front-End (AFE) Rectifier with direct and quadrature axis current control method. Most of the research works describe that the controller for an AFE Rectifier requires three Proportional-Integral (PI) controllers to regulate DC voltage, d-axis and q-axis current. Normally, the outer loop for DC voltage control requires high gain value to stabilize the DC voltage and the inner loop for current control requires low gain values to regulate the current. In this proposed work, due to lower gain of the inner current loop, the PI controllers for that specific loop has been omitted to deal with the easy control of the controller.
3 citations
Cites methods from "Properties of reactive current inje..."
...In such PWM rectifier, generally PI controllers are used as cascaded control [4-9]....
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References
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TL;DR: New trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented and a review of the appropriate storage-system technology used for the Integration of intermittent renewable energy sources is introduced.
Abstract: The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented
3,799 citations
"Properties of reactive current inje..." refers background in this paper
...Firstly, power electronics technology has become the enabling technology for grid integration of renewable energy resources, distributed generation and energy storage systems [1], [2]....
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TL;DR: In this article, power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems.
Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.
2,296 citations
"Properties of reactive current inje..." refers background in this paper
...Firstly, power electronics technology has become the enabling technology for grid integration of renewable energy resources, distributed generation and energy storage systems [1], [2]....
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Journal Article•
TL;DR: In this article, power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems.
Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.
2,076 citations
TL;DR: This paper presents an exhaustive review of three-phase improved power quality AC-DC converters configurations, control strategies, selection of components, comparative factors, recent trends, their suitability, and selection for specific applications.
Abstract: Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.
1,691 citations
"Properties of reactive current inje..." refers background in this paper
...Secondly, the relatively low harmonic impact, the high degree of controllability and the possibility for regenerative operation has made actively controlled converters a viable alternative to replace diode rectifiers [3], [4]....
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TL;DR: In this article, a phase-locked loop (PLL) system under distorted utility conditions is presented and a control model of the PLL system is developed and recommendations are made on tuning of this model specially for operation under common utility distortions such as line notching, voltage unbalance/loss, and frequency variations.
Abstract: Operation of a phase locked loop (PLL) system under distorted utility conditions is presented. A control model of the PLL system is developed and recommendations are made on tuning of this model specially for operation under common utility distortions such as line notching, voltage unbalance/loss, and frequency variations. The PLL is completely implemented in software without any filters. All analytical results are experimentally verified.
1,061 citations
"Properties of reactive current inje..." refers methods in this paper
...The synchronization of the control system was based on voltage measurements at the grid side of the filter inductor, processed by a traditional synchronous reference frame Phase Locked Loop (PLL) [22]....
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