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

ABSTRACT 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

Download full-text

Full-text

Available from: Hannu Laaksonen, Dec 31, 2014
5 Followers
 · 
565 Views
  • Source
    [Show abstract] [Hide abstract]
    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
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Microgrids are receiving an increasing interest to integrate the growing share of distributed-generation (DG) units in the electrical network. For the islanded operation of the microgrid, several control strategies for the primary control have been developed to ensure stable microgrid operation. In low-voltage (LV) microgrids, active power/voltage (P/V) droop controllers are gaining attention as they take the resistive nature of the network lines and the lack of directly coupled rotating inertia into account. However, a problem often cited with these droop controllers is that the grid voltage is not a global parameter. This can influence the power sharing between different units. In this paper, it is investigated whether this is actually a disadvantage of the control strategy. It is shown that with P/V droop control, the DG units that are located electrically far from the load centers automatically deliver a lower share of the power. This automatic power-sharing modification can lead to decreased line losses; therefore, there is overall better efficiency compared to the methods that focus on perfect power sharing. In this paper, the P/V and P/f droop control strategies are compared with respect to this power-sharing modification and the line losses.
    IEEE Transactions on Power Delivery 10/2012; 27(4-4):2318-2325. DOI:10.1109/TPWRD.2012.2212919 · 1.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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 01/2012; 8:382–387. DOI:10.1016/j.procs.2012.01.076