Conference Paper

Voltage and Frequency Control of Inverter Based Weak LV Network Microgrid

VTT Processes, Vaasa, Finland
DOI: 10.1109/FPS.2005.204293 Conference: Future Power Systems, 2005 International Conference on
Source: IEEE Xplore


In this paper voltage and frequency control of islanded microgrid after intentional and unintentional switching events are investigated. The weak low voltage (LV) network based microgrid consists of two inverter based distributed generation (DG) units. One unit is a storage (battery) unit and the other is a photovoltaic (PV) cell. In this case the battery inverter with rapid response is considered to act as a master and it has the main responsibility to control the voltage and frequency in microgrid when islanded from the main distribution network. The studies are performed on a PSCAD simulation software package. Simulation studies show the voltage - active power and frequency - reactive power dependency in weak LV network. The studies also show that in order to maintain frequency balance in islanded microgrid, there is need for a reference sine wave generator inside master unit which imitates the main network phase voltages and gives the input for master units' (battery storage) PLL (phase locked loop) during islanding

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Available from: Hannu Laaksonen, Dec 31, 2014
264 Reads
    • "A. Generator Power Output Control Fig. 1 shows the equivalent circuit for a generator. The active power and reactive power outputs can be determined by (1) and (2) respectively [14]. "
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    ABSTRACT: Droop control is a load sharing strategy applied in conventional power systems. In this paper, droop control strategy has been adopted for the generators in a remote area power supply (RAPS) system in order to share active and reactive power load based on the rated capacities of the generators. Different characteristics of conventional and inverter-based energy resources make it difficult to share load in proportion to the rated capacities of the generators in a RAPS system. Therefore, this paper investigates the load sharing performance of different combinations of conventional and inverter-based energy resources in RAPS systems. The study scenarios investigated in this study comprised of conventional energy resources, inverter-based energy resources, and both conventional and inverter-based energy resources. Simulation results have illustrated the effectiveness of droop control strategy to share load among conventional and inverter-based energy resources in a RAPS system. Furthermore, due to different characteristics of generators, power sharing performance has impaired, in particular, in RAPS systems consisting of both conventional and inverter-based generators compared to the RAPS systems with generators of the same type.
    AUPEC 2013, Hobart, Australia; 09/2013
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    • "The active power controller of the DG units defines the reference terminal voltage v g,ref (t) of their voltage-source inverter (VSI) interface, which is depicted in Fig. 2. Because of the mainly resistive nature of the low-voltage microgrid lines, a linkage between active power P and rms voltage V g , and, a linkage between reactive power Q and phase angle differences are valid [38]. Therefore, P /V g droops and Q/f droops [39] are used to determine v g,ref (t). "
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    ABSTRACT: For the islanded operation of a microgrid, several control strategies have been developed. For example, voltage-based droop control can be implemented for the active power control of the generators and the control of the active loads. One of the main advantages of a microgrid is that it can be implemented as a controllable entity within the electrical network. This requires the ability of the utility grid to control or influence the power exchange with the microgrid by communicating with only one unit. However, little research has been conducted on controlling the power transfer through the point of common coupling (PCC). This paper addresses this issue by introducing the concept of a smart transformer (ST) at the PCC. This unit controls the active power exchange between a microgrid and the utility grid dependent on the state of both networks and other information communicated to the ST. To control the active power, the ST uses its taps that change the microgrid-side voltage at the PCC. This voltage-based control of the ST is compatible with the voltage-based droop control of the units in the microgrid that is used in this paper. Hence, the microgrid units can automatically respond to changes of ST set points and vice versa. Several simulation cases are included in this paper to demonstrate the feasibility of the ST concept.
    IEEE Transactions on Industrial Electronics 04/2013; 60(4):1291-1305. DOI:10.1109/TIE.2011.2165463 · 6.50 Impact Factor
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    • "There will be another PLL system in the frequency regulator as a frequency reference. [6] A voltage regulator will be included to maintain the voltage magnitude as well. "
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    ABSTRACT: We propose a concept of microgrid for electric power distribution with lattice topology in which every node is interconnected with a number of closest neighbors. Such a toppology directly reflects special arrangement of households throughout subdivisions in cities. Each node of the microgrid is assumed to be an electric load and possibly a power-delivering inverter simultaneously. We introduce a method of local control for the inverters to collectively regulate the voltage and frequency in the microgrid. Our control method does not require data communication between the nodes nor is it necessary to define a dominant node to act as a central utility. Therefore all inverters remain autonomous at all times. We provide numerical simulation results demonstrating stability and controllability of voltage and frequency in the microgrid.
    Procedia Computer Science 12/2012; 8:382–387. DOI:10.1016/j.procs.2012.01.076
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