Smart Transformer for the Provision of Coordinated Voltage and Frequency Support in the Grid

Considering the increase in renewable generation and the consequent reduction in power system inertia, the Virtual Synchronous Machine (VSM) control method has been proposed to control power converters to emulate the inertia and other the characteristics of the synchronous machine. However, to achieve the function of VSM control, an extra energy base, typically storage, is required to connect to the controlled converter. In this work we investigate the application of the VSM control to the distribution system demand through the use of a VSM controlled smart transformer. Through control of the demand in this way, the demand itself can be used to emulate inertia and provide frequency support. This paper presents the details of the flexible demand control applied to a smart transformer supplying a low voltage distribution grid. The operation of the control is validated on scaled hardware using real time simulation with hardware in the loop. Simulations on a 400 kVA, 400 V distribution network are used to quantify the demand flexible. IEEE 39 bus is used to verify the benefit of the proposed control in terms of voltage and frequency in the power system.