Synchronous islanded operation of an inverter interfaced renewable rich microgrid using synchrophasors

Abstract

This paper describes a novel strategy for microgrid operation and control, which enables a seamless transition from grid connected mode to islanded mode, and restoration of utility supply, without loss or disruption to loads sensitive to frequency or phase angle dynamics. A simulation study is conducted on a microgrid featuring inverter connected renewable generation, and power electronic interfaced loads. Therefore, the microgrid inherently has low inertia, which would subsequently affect the dynamic characteristics of the microgrid, in particular during mode transition. The microgrid is controlled by means of synchrophasor data to achieve synchronous island operation, enabling the microgrid to track the utility frequency and phase angle. The simulation includes synchrophasor acquisition and telecoms delays, allowing for detailed investigation of the microgrid dynamics under various mode transition scenarios, including the risk of commutation failure of the inverter sources. The proposed method is demonstrated to successfully maintain a microgrid in synchronism with the main utility grid after the transition to islanded mode without significant impact on various equipment connected to the microgrid. Thus, synchronous island operation of low inertia microgrids is feasible. This study also showed that utility supply could be seamlessly restored if the microgrid is operated as a synchronous island.

Research on smooth switching and islanding detection technology for ER system

“…If the grid voltage deviates from the inverter output voltage frequency or phase, then e q ≠ u oq . Therefore, the resulting error (e q - u oq ) is processed by the PI regulator to generate the frequency offset f sync , which will then superimpose with the output frequency of the droop controller according to (8) to produce the inverter output frequency reference. This method achieves simultaneous frequency and phase angle synchronisation, avoiding the contradiction between frequency and phase synchronisation…”

Technique for stability enhancement of microgrids during unsymmetrical disturbances using battery connected by single‐phase converters

“…Its advantage over the existing schemes for enhancing the stability of microgrids lies in the fact that it provides unsymmetrical injection of active and reactive power in every phase. Unlike the proposed technique, the existing models for the enhancement of stability include only the three-phase control and elements [7,8,10,13,14,16,17,[22][23][24]32], except in the case of single-phase systems [21], whose actual application is limited to low-voltage networks. Practically all existing techniques of centralised control that are applied in medium voltage assume the use of three-phase converters topologies [33].…”

Improving quality of supply in small‐scale low‐voltage active networks by providing islanded operation capability

“…Active networks have the potential to maintain load supply fully or partially when the utility voltage is lost. However, according to current regulations and practices, in the event of a disruption in the utility grid resulting in the loss of supply, the sources in the network should be disconnected [8,9], to avoid the risk of damaging equipment and to protect the health and safety of personnel [10][11][12][13]. Clearly, this means that the potential for active networks to maintain load supply cannot be exploited.…”

“…In the literature concerning microgrids (MGs), different strategies have been presented for enabling energy sources to operate in both grid-connected and islanded modes [10,13,26,27,29]. However, active networks are not designed as MGs and such strategies are not applicable.…”