Frequency-Based Energy-Management Strategy for Stand-Alone Systems With Distributed Battery Storage

Abstract

Distributed generation is an attractive solution for stand-alone AC supply systems. In such systems, the installation of two or more energy-storage units is recommended for system redundancy and may also be required when there is a consumption increase following installation. However, energy management with multiple energy-storage units has been but vaguely analyzed in the literature and the few studies made are based on communication cables with a central supervisor. This paper proposes an energy management strategy for a multiplebattery system which makes it possible to avoid the use of communication cables, rendering the system more cost-effective and reliable. The strategy modifies the conventional droop method so that the power becomes unbalanced, allowing for the regulation of one or more battery voltages or currents, as required. Furthermore, whenever the frequency is high, the PV inverters reduce their power in order to prevent the battery from overcharge or high charging currents. On the other hand, whenever the frequency is low, then either the non-critical loads are regulated or the system stops in order to prevent the battery from over-discharge or high discharging currents. Simulation and experimental validation are performed for a system with two battery inverters, two PV inverters and a number of loads.

Method for load sharing and power management in a hybrid PV/battery source islanded microgrid

“…Since m p-i P Bat-S1-i is not measurable directly, it can be determined according to f. As PI controller is used in (5), the unit's frequency follows the frequency of other units that are in State 1; therefore, after some manipulation using (3), (4) and (9) This state is associated with Mode III of the described operating modes in which total PV maximum power is more than total power required by load and charging of the batteries. In this state, the unit's battery is charged with maximum power, output power is controlled by (8) and PV boost converter controls V dc .…”

“…In [1][2][3] three power management methods are proposed based on frequency signaling but the application of these methods are limited to the microgrids composed of only one energy storage unit. In [4] a frequency based energy management strategy is proposed for a microgrid with distributed battery storage but it is only valid for systems with separate battery units not hybrid source units. Similarly the method proposed in [5] is only applicable to separate battery units.…”

Decentralized method for load sharing and power management in a hybrid single/three-phase islanded microgrid consisting of hybrid source PV/battery units

“…These objectives can be achieved by centralized [13][14][15][16][17][18] or decentralized [9,[19][20][21][22][23][24][25][26] power management. The centralized control strategies rely on communication among units and loads in the MG, which reduces the reliability of the system [22,27]. The decentralized control methods, however, only require local measurements.…”

Decentralized Method for Load Sharing and Power Management in a PV/Battery Hybrid Source Islanded Microgrid

“…These objectives can be achieved by centralized [10][11][12] or decentralized [7,[13][14][15][16][17][18] power management. The centralized control strategies rely on communication among units and loads in the MG, which reduces the reliability of the system [16,19]. The decentralized control methods, however, only require local measurements.…”

“…However, the applications of these methods are limited to the MGs composed of only one energy storage unit. In [16] a frequency based energy management strategy is proposed for a MG with distributed battery storage but it is only valid for systems with separate battery units; moreover, in some modes it transfers power from some of the batteries to the others, which reduces the overall efficiency of the system because of the power losses during charging and discharging of the batteries. Similarly, the frequency bus-signaling method proposed in [17] is only applicable to separate battery units.…”