ECE–590I POWER & ENERGY SYSTEMS SEMINAR
WHEN: Thursday, November 7, 2024
WHERE: ECEB 1013, 1:00 – 2:00 p.m.
SPEAKER: Arun Karuppaswamy, Asst. Professor, IIT Madras
TITLE: Grid-Tie Inverters: A Few Challenges and Possible Solutions
ABSTRACT: Grid-tie inverters serve several useful applications such as dynamic reactive power support (STATCOM), active rectification (front end converter) and distributed generation (to interface renewable energy sources to the grid). Though the grid-tie inverter technology has largely matured, there are still some finer aspects of design and control that is of research and practical interest. This talk discusses some of these aspects. The talk assumes a general audience working in the field of Power Electronics and will start with some simple fundamental ideas related to grid-tie inverters. The talk will then move on to a more detailed discussion, highlighting a few challenges in design and control of grid-tie inverters and some proposed solutions to handle them. A broad overview of the other Power Electronics work carried out in the dSine lab (pronounced as “Design”) at IIT Madras will also be discussed.
Irrespective of the application, the grid-tie inverters typically employ three control loops – phase locked loop (PLL) control, current control and voltage control. The PLL control tracks the magnitude, frequency, and phase of the grid to help with the synchronisation of the inverter to the grid. The PLL controls are well established under ideal grid voltage conditions. However, there are challenges in extracting the fundamental frequency information of the grid voltage under non-ideal grid voltage conditions such as unbalance, harmonics and dc offset. A distorted grid voltage is a reality in weak grids and in systems with high presence of non-linear loads. A part of the talk discusses this issue in detail, touches upon existing approaches to handle the problem and the proposed approach that helps improve the dynamics of some existing methods.
Grid-tie inverters have high frequency components of voltage at their output besides the desired fundamental frequency component, due to the switching nature of the inverter. A third order LCL filter is typically used at the output to limit the high frequency components injected into the grid to the extent prescribed by standards such as the IEEE-1547. Besides the basic requirement of filtering the high frequency components, the filter is expected to meet several other constraints as well. Literature indicates about seven desirable constraints apart from meeting the filter’s attenuation requirement. The selection of LCL filter parameters should ideally meet the basic and the other desirable constraints. Further, the LCL filter also appears as the plant in the current control loop. The third order nature of the filter introduces challenges in the controller design as well. A careful controller design is essential to ensure that the controller is not destabilised due to resonance. The selection of LCL filter parameters usually considers the control aspect as well. The talk will discuss in detail, the challenges in designing the LCL filter and will highlight a few aspects of the proposed filter design that addresses the challenges in the design.
BIOGRAPHY: Arun Karuppaswamy B received his Bachelors in Electrical and Electronics Engineering from College of Engineering, Guindy in 2003, Masters in Power Electronics from NIT, Calicut in 2007 and Doctorate in Electrical Engineering from IISc, Bangalore in 2014 – all in India. During his Masters, he was associated with the Power Electronics Group at CDAC, Thiruvananthapuram for a year. CDAC Thiruvananthapuram is a noted lab for technology development and transfer in Power Electronics in India. Arun Karuppaswamy was awarded a gold medal in his Masters and is a recipient of the POSOCO Power Systems Award for his Ph.D work. The POSOCO award is given by the Power Systems Operation Corporation of India for contributions in areas related to Power Systems. After his Ph.D, Arun Karuppaswamy briefly worked as a Senior Design Engineer with Bloom Energy India Pvt. Ltd, Bangalore for two years. At Bloom Energy, his team worked on grid-connected inverters upto a system power level of 250 kVA.
Since 2016, Arun Karuppaswamy is with the Dept. of Electrical Engineering, IIT Madras as an Assistant Professor. He was a part of the Ministry of New and Renewable Energy’s committee that drafted the “Technical requirements for Photovoltaic Grid Tie Inverters to be connected to the Utility Grid in India”. Arun Karuppaswamy has been working in the area of grid connected inverters for more than a decade. Apart from grid-connected inverters, his present interests are wide-band gap devices, wireless charging of electric vehicles, dc solid state circuit breakers and EMI studies on inverters. He works closely with the industry and has been a consultant for several industries in India like Lucas TVS, Royal Enfield, MRF and L&T besides start-ups like Agnikul Cosmos.