A Simplified Control Method for Tie-Line Power of DC Micro-Grid

Abstract

Compared with the AC micro-grid, the DC micro-grid has low energy loss and no issues of frequency stability, which makes it more accessible for distributed energy. Thus, the DC micro-grid has good potential for development. A variety of renewable energy is included in the DC micro-grid, which is easily affected by the environment, causing fluctuation of the DC voltage. For grid-connected DC micro-grid with droop control strategy, the tie-line power is affected by fluctuations in the DC voltage, which sets higher requirements for coordinated control of the DC micro-grid. This paper presents a simplified control method to maintain a constant tie-line power that is suitable for the DC micro-grid with the droop control strategy. By coordinating the designs of the droop control characteristics of generators, energy storage units and grid-connected inverter, a dead band is introduced to the droop control to improve the system performance. The tie-line power in the steady state is constant. When a large disturbance occurs, the AC power grid can provide power support to the micro-grid in time. The simulation example verifies the effectiveness of the proposed control strategy.

A comprehensive review of DC microgrid in market segments and control technique

“…Due to the massive invention, a lithium-ion rechargeable battery uses the dead-band droop characteristic, which requires the battery to run in "offline" mode. A floating or standby mode of operation is used to avoid the frequent charge and discharge timing [ 73 ]. Droop control modifies the DC injection current to its reference value, allowing control mechanisms for battery-based energy storage systems to be built.…”

“… Improved voltage control under low loads only, not under heavy loads. Dead band droop [ 73 , 74 ] Avoids charging and draining the battery unnecessarily. The majority of converters in the DC microgrid are regarded to be insufficient for their installation.…”

Improving the Sustainability of Self-Consumption with Cooperative DC Microgrids

“…This approach allows independent control by each converter in each DG without the need for a communication channel between them. As a disadvantage, the control droop presents an inherent commitment between the regulation of voltage and the distribution of demand among the different DGs [22,23]. To solve this problem, droop control variants have been proposed where the gain (slope of the droop characteristic) is adjusted dynamically [23].…”

“…Randomly, a group of households was selected to function as loads (Scenario 1), demanding the power indicated in Table 4 (with a negative value). With an algorithm developed in Matlab, according to Equations (16) to (23), the operating state of the network was obtained (power generated (with a positive value) and voltage in each node). No conventional load flow was used since there was no slack bus.…”

Tie-line Power Flow Control Method for Grid-connected Microgrids with SMES Based on Optimization and Fuzzy Logic

“…This approach was tested and validated by using the modulator aluminum electrolysis load without considering energy storage systems. In [18], an improved droop control strategy was introduced to maintain a constant tie-line power that is suitable for the DC MG by coordinating the designs of droop control characteristics of generators, energy storage units, grid-connected inverter, and a dead band. The SOC and the optimal charging/discharging power of the energy storage units were not included in this study.…”