Electromagnetic sensing in smart grid

It is well-known from the electromagnetic theory that electric current generates magnetic field, and the information of the current together with the condition of the power system is already embedded in the magnetic field. By measuring the magnetic field, we can actually obtain a lot of information about the status of the power grid. Sensing techniques based on electromagnetic field sensing encompassing contactless sensing technologies, IoT connectivity, energy harvesting and shielding will have a lot to offer to a Cyber-Enabled Grid (CEG) and ultimately an Autonomous Energy Grids (AEGs), a futuristic concept where the grid will be making automated operational decisions [1].

[1] Philip W.T. Pong, Anuradha M. Annaswamy, Benjamin Kroposki, Yingchen Zhang, Ram Rajagopal, Gil Zussman, H. Vincent Poor, "Cyber-Enabled Grids: Shaping Future Energy Systems", Advances in Applied Energy, vol. 1, 100003 (2021)

Figure 1. Pervasive sensing in a power grid enabled by contactless sensing [1]

Contactless monitoring of renewable energy systems

The online-monitoring scheme for aluminum electrolytic capacitors in photovoltaic systems were developed in our Laboratory with magnetic sensors non-invasively. The voltage drops on capacitance is considered in the method to improve the accuracy of  equivalent series resistance (ESR)-estimation and the equation to estimate capacitance is derived.  This condition monitoring technique based on the estimation of ESR by using the current measured by magnetic-field sensing is applicable for the boost converters.

[2] W. Miao, K. H. Lam, Philip W. T. Pong, “Online Monitoring of Aluminum Electrolytic Capacitors in Photovoltaic Systems by Magnetoresistive Sensors”, IEEE Sensors, vol. 20, 767 (2020)

Figure 2. The online condition-monitoring scheme of aluminum electrolytic capacitors in a photovoltaic system [2] 

Contactless monitoring for electric-vehicle transportation

Unexpected faults or failures of electric motors could lead to costly repair or replacement, or even a catastrophic system failure in several mission-critical applications. Therefore, the reliable and valid health monitoring and early fault-diagnostic are highly desired to ensure the high performance of electric vehicles over long periods of time. Fast online detection of inter-turn short-circuit faults for permanent magnet synchronous machines is a challenging task. Our Laboratory developed a new technology to online inter-turn short-circuit fault detection for permanent magnet synchronous machines by means of sensing the external stray magnetic field outside the motor stator yoke. The stray magnetic field provides the information about the phase currents as well as the status of stator windings and thus, the location of interturn short-circuit fault can be detected accordingly.

[3] X. Liu, W. Miao, Q. Xu, L. Cao, C. Liu, Philip W. T. Pong, “Inter-Turn Short-Circuit Fault Detection Approach for Permanent Magnet Synchronous Machines Through Stray Magnetic Field Sensing”, IEEE Sensors, vol. 19, 7884 (2019)

Figure 3. (a) Test permanent magnet synchronous machine in experiments. (b) Tunneling magnetoresistance (TMR) magnetic sensors mounted outside the motor stator yoke to measure the stray magnetic field. [3]