Experimental Study of a Centralized Control Strategy of a DC Microgrid Working in Grid Connected Mode

Abstract

The results concerning the integration of a set of power management strategies and serial communications for the efficient coordination of the power converters composing an experimental DC microgrid is presented. The DC microgrid operates in grid connected mode by means of an interlinking converter. The overall control is carried out by means of a centralized microgrid controller implemented on a Texas Instruments TMS320F28335 DSP. The main objectives of the applied control strategies are to ensure the extract/inject power limits established by the grid operator as well as the renewable generation limits if it is required; to devise a realistic charging procedure of the energy storage batteries as a function of the microgrid status; to manage sudden changes of the available power from the photovoltaic energy sources, of the load power demand and of the power references established by the central controller; and to implement a load shedding functionality. The experimental results demonstrate that the proposed power management methodology allows the control of the power dispatch inside the DC microgrid properly.2 of 25 highly stable, even in the case of low quality distribution grids [8]. When the distribution grid fails, the microgrid must regulate the DC bus voltage without the ILC. Some control methods have been developed and proposed in the literature [9][10][11] for reaching this goal. The typical objectives of the DC microgrid in grid-connected mode are: to minimize the cost of the imported energy from the main grid, to optimize the power dispatch among the converters and the DC bus and to regulate the DC bus voltage [12]. For the optimization of the power dispatch, communications between the devices of the MG and the grid operator are necessary [13,14].Regarding the control system, one of the main challenges in MGs is how to maintain the generation and consumption energy balance [15]. Power imbalance is a common scenario in MGs, which is caused by the discontinuous power generation availability caused in turn by the intermittent nature of renewables and the variable power demand of the loads connected to the MG, among other factors. These imbalances should be managed fast, safely and effectively by the MG control in order to avoid electrical transients, which can damage or destabilize the system [6][7][8]. Therefore, proper power management control strategies have been developed. These strategies are aimed mainly at: (i) controlling the connected DGs and energy storage system, (ii) regulating the DC bus voltage, (iii) optimizing the power dispatch between DC/DC converters and the DC bus voltage to minimize the cost of imported energy from the main grid, (iv) managing and optimizing the ESS operation, and (v) managing current sharing between parallel converters [16,17]. At present, the major control strategies to maintain power balance in DC microgrids are the well-known droop control methods [14][15][16][17][18], which don't require any communication infrastructure, or other solutions using communications [2...

A Real-Life Application of a Smart User Network

“…In a hierarchical control architecture, the micro-source controllers and the load controllers are used [14][15][16][17]. A microgrid central controller provides the micro-source controllers with the demand requirements among other control functions [18][19][20][21].…”

Power Flow Control Strategy and Reliable DC-Link Voltage Restoration for DC Microgrid under Grid Fault Conditions

“…Recently, many power flow control strategies (PFCSs) based on the centralized control approach have been presented for the purpose of ensuring the system power balance under various conditions [16][17][18][19]. In Ref [16], an improved voltage control strategy for a DCMG composed of photovoltaic and hybrid ESSs, such as batteries and supercapacitors, is proposed to stabilize the DCV.…”

“…In both cases, maintaining the power balance in DCMG by a battery is not possible due to the power limit. To deal with this issue, the maximum charging and discharging currents of the battery are considered in the design of PFCS under the grid-connected mode in Ref [18]. In Ref [19,20], to avoid the system collapse in case of power shortage, an appropriate load shedding (LS) is implemented to disconnect less important loads.…”

Internet of Things for Smart Grid Automation

“…Generally speaking, the micro grid provides clean, green and sustainable energy to the user [8,9]. In the distribution power system, the micro grid is connected to the feeder circuit.…”