Scaled-Up Slack Generator Based on Parallel Inverters for a Reliable IFSA Microgrid

Abstract

It is expected that the penetration of renewable-energy-based generators will rapidly increase worldwide. These factors also lead to an increase in the portion of inverters in the power system. This paper proposes a method to scale up the slack generator size based on parallel inverters. All of the multiple parallel inverters except one share the measured power from the slack bus to the grid by a predetermined ratio based on their sizes. A single inverter that does not participate in power sharing is allocated to be in charge of clearing the small power gap caused by the control delay and the measurement error (i.e., the physical slack). As a result, the net size of the scaled-up slack generator is n times greater than that of the physical slack when n non-slack inverters are added to the physical slack inverter. The proposed method is validated based on a real island power system model in Korea using a power system computer-aided design/electromagnetic transient including DC (PSCAD/EMTDC TM ).INDEX TERMS DG acceptability, large IFSA microgrid, load sharing, parallel inverter connection, scaleup of slack generator.

Optimal Allocation of BESS to Maximize Efficiency Under Constrained SOC in Parallel Inverter-Based Scaled-Up Slack Bus

“…Unfortunately, the practical inverter has a much smaller power rating than the conventional generator. To overcome the limit, the control and operation of multiple inverter groups are proposed for a slack operation [6]. Similarly, the backbone energy source must be composed of plural energy sources unless a unit source is large enough to cover the maximum output.…”

“…It has been challenging to accurately balance the energy using conventional power-sharing methods such as droop and VMS in [24], [25], [26], and [27]. The proposed method allows the multiple inverter-based scaled-up slack generator [6] to operate its backbone power source efficiently so that the group of small-size inverters can stably operate a relatively large inertia-free stand-alone (IFSA) microgrid [5].…”

“…The system in Figure 4 is considered for the following case studies. The size of each BESS is assumed as 0.1 MW/0.3 MWh considering the actual islanded power system in Korea of the previous study [6]. The main target of this study is the green slack control box in Figure 4.…”

Voltage Stability Assessment of a Campus DC Microgrid Implemented in Korea as a Blockchain-Based Power Transaction Testbed

“…PVs, V2Gs, ESSs, and EV chargers are composed of current sources and diodes, current sources, voltage sources, and resistors, respectively. The PCS is composed of a general grid-connected inverter, and its control is performed by a generic PQ controller, as shown in Figure 2 [23]. The PQ controller consists of an outer loop for power and an inner loop for current, where the control variables are on the d-q axis synchronized to the grid voltage via a phase-locked loop (PLL).…”