IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Improvement in the reliability of grid-connected inverters is desirable with their increasing use. Inverter reliability tests usually focus on thermal testing of semiconductor devices. Regenerative methods are adopted to minimize the energy consumed during these tests. Regeneration requires additional systems-converters or passive components. In this paper, a novel method for thermal testing of the passive components associated with a grid-connected inverter is proposed. The method can be used to test the output filter inductors, output ac filter capacitors and input dc electrolytic capacitors. Thermal stress affects the working life of capacitors and can cause insulation failure in inductors. Thermal testing of these passive components, besides the semiconductor device thermal testing, contributes to improved reliabilty of the grid-connected inverter system. Unlike regenerative methods that require additional systems of high-power rating, the proposed method circulates rated current within the three legs of the inverter under test. The only additional system required is a low power dc supply with variable output voltage. The variable dc input supplies the losses in the system under test. The applicability of the proposed test for both three-wire and four-wire grid-connected inverter systems is discussed. © 2015 IEEE.

Department of Electrical Engineering

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Department Of Chemical Engineering

2015 IEEE International Transportation Electrification Conference, ITEC-India 2015

A novel thermal performance evaluation method for inverter passive components

Design of a suitable thermal model, inclusive of the enclosure or cabinet, is an integral part of power electronic thermal management. This stems from the fact that power losses in an inverter may cause severe temperature rise in the enclosed cabinet, causing damage to the inverter switches or components. A thermal enclosure model for a 3φ, back-to-back inverter topology rated 24 kVA, kept in an enclosure having dimensions 1.524 × 1.066 × 1.828 cubic metre is presented. An enclosure air temperature calculation algorithm has been proposed to calculate the enclosure air temperature in steady state when power losses in the inverters and enclosure material and dimensions are the only known parameters. Effects of the enclosure air temperature on the heat-sinks and switches of the back to back inverter have also been investigated for the above mentioned inverter topology. The enclosure air temperature is calculated with an error less than 3%. © 2015 IEEE.

A thermal enclosure model for inverters

Semiconductor device junction temperatures are maintained within datasheet specified limits to avoid failure in power converters. Burn-in tests are used to ensure this. In inverters, thermal time constants can be large and burn-in tests are required to be performed over long durations of time. At higher power levels, besides increased production cost, the testing requires sources and loads that can handle high power. In this study, a novel method to test a high power three-phase grid-connected inverter is proposed. The method eliminates the need for high power sources and loads. Only energy corresponding to the losses is consumed. The test is done by circulating rated current within the three legs of the inverter. All the phase legs being loaded, the method can be used to test the inverter in both cases of a common or independent cooling arrangement for the inverter phase legs. Further, the method can be used with different inverter configurations - three- or four-wire and for different pulse width modulation (PWM) techniques. The method has been experimentally validated on a 24 kVA inverter for a four-wire configuration that uses sine-triangle PWM and a three-wire configuration that uses conventional space vector PWM. © 2015. The Institution of Engineering and Technology.

IET Power Electronics

Thermal test method for high power three-phase grid-connected inverters

Grid simulators are used to test the control performance of grid-connected inverters under a wide range of grid disturbance conditions. In the present work, a three-phase back-to-back connected inverter sharing a common dc bus has been programmed as a grid simulator. Three phase balanced disturbance voltages applied to three-phase balanced loads has been considered in the present work. The developed grid simulator can generate three phase balanced voltage sags, voltage swells, frequency deviations and phase jumps. The grid simulator uses a novel disturbance generation algorithm. The algorithm allows the user to reference the disturbance to any of the three phases at any desired phase angle. Further, the exit of the disturbance condition can be referenced to the desired phase angle of any phase by adjusting the duration of the disturbance. The grid simulator hardware has been tested with different loads-A linear purely resistive load, a non-linear diode-bridge load and a grid-connected inverter load. © 2014 IEEE.

2014 IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2014

A grid simulator to evaluate control performance of grid-connected inverters

Grid-connected inverters require a third-order LCL filter to meet standards such as the IEEE Std. 519-1992 while being compact and cost-effective. LCL filter introduces resonance, which needs to be damped through active or passive methods. Passive damping schemes have less control complexity and are more reliable. This study explores the split-capacitor resistive-inductive (SC-RL) passive damping scheme. The SC-RL damped LCL filter is modelled using state space approach. Using this model, the power loss and damping are analysed. Based on the analysis, the SC-RL scheme is shown to have lower losses than other simpler passive damping methods. This makes the SC-RL scheme suitable for high power applications. A method for component selection that minimises the power loss in the damping resistors while keeping the system well damped is proposed. The design selection takes into account the influence of switching frequency, resonance frequency and the choice of inductance and capacitance values of the filter on the damping component selection. The use of normalised parameters makes it suitable for a wide range of design applications. Analytical results show the losses and quality factor to be in the range of 0.05–0.1% and 2.0–2.5, respectively, which are validated experimentally.