Feeder-flow Control Mode Research Articles

Coordinate control and energy management strategies for a grid-connected hybrid system

This paper explains how to operate a networked hybrid system. A Proton Exchange Membrane Fuel Cell (PEMFC) and a hybrid photovoltaic (PV) array system are taken into account. The hybrid system can run in Feeder Flow Control (FFC) or Unit Capacity Control (UPC) mode. Changes in load demand are adjusted by the main grid because the hybrid source's output is controlled by reference power in UPC mode. Renewable energy is widely used. When light and temperature fluctuate, a PV battery uses Maximum Power Point Tracking (MPPT) to give maximum power to a load. Photovoltaic electricity is uncontrollable because its output varies with the outside and cell temperature. PEMFC should be added to the hybrid system to overcome its limitations. The output of the hybrid source can be controlled by adjusting the output power of the frequency converter. As a result, it is necessary to set a reference value for the output of the hybrid source. In Feeder-Flow Control (FFC) mode, the feeder flow is controlled to remain constant, the hybrid source takes on additional load, and as a result, the feeder reference power needs to be understood. This method reduces load shedding and boosts electricity under high loads. Under light load, the hybrid power supply switches to UPC mode. When the load requirement is near the border of the mode change, UPC or FFC mode is used. Hysteresis eliminates power reference fluctuations. The proposed operation strategy increases system performance, system stability, and mode transitions by consistently operating the PV array at maximum output power and the Photovoltaic–Fuel Cell (PVFC) within its highefficiency range.

Optimal feeder flow control for grid connected microgrids

The optimal management of distributed energy resources is one of the existing challenges for the deployment of microgrids. When microgrids operate under feeder flow control mode, trying to maintain a constant self-consumption, generators adapt their output power to compensate load and non-dispatchable generation variations. So, due to the uncertainty, finding the optimal operation point is an important task that can become complex. This paper proposes an optimal power flow problem formulation for feeder flow controlled microgrids. It iated as a mixed integer second order cone program considering the optimal power flow equations in its relaxed form and uncertainty by means of stochastic formulation. In addition, an algorithm is developed in order to find a feasible optimum solution of the original non-relaxed problem. The proposed algorithm can also be used in other optimal power flow problems with the condition that they must use the same relaxation. The algorithm is validated through the IEEE 33-Bus distribution test system.

Power-Sharing Method of Multiple Distributed Generators Considering Control Modes and Configurations of a Microgrid

This paper describes the active power and frequency-control principles of multiple distributed generators (DGs) in a microgrid. Microgrids have two operating modes: 1) a grid-connected mode and 2) an islanded mode. During islanded operation, one DG unit should share output generation power with other units in exact accordance with the load. Two different options for controlling the active power of DGs are introduced and analyzed: 1) unit output-power control (UPC) and 2) feeder flow control (FFC). Taking into account the control mode and the configuration of the DGs, we investigate power-sharing principles among multiple DGs under various system conditions: 1) load variation during grid-connected operation, 2) load variation during islanded operation, and 3) loss of mains (disconnected from the main grid). Based on the analysis, the FFC mode is advantageous to the main grid and the microgrid itself under load variation conditions. However, when the microgrid is islanded, the FFC control mode is limited by the existing droop controller. Therefore, we propose an algorithm to modify the droop constant of the FFC-mode DGs to ensure proper power sharing among DGs. The principles and the proposed algorithm are verified by PSCAD simulation.