Simplified Thermal Modeling for IGBT Modules With Periodic Power Loss Profiles in Modular Multilevel Converters

Abstract

One of the future challenges in Modular Multilevel Converters (MMCs) is how to size key components with compromised costs and design margins, while fulfilling specific reliability targets. It demands better thermal modeling compared to the state-of-the-arts in terms of both accuracy and simplicity. Different from two-level power converters, MMCs have inherent dc-bias in arm currents and the power device conduction time is affected by operational parameters. A time-wise thermal modeling for the power devices in MMCs is therefore an iteration process and time-consuming. This paper thus proposes a simply analytical thermal modeling method, which adopts equivalent periodic power loss profiles. More importantly, time-domain simulations are not required in the proposed method. Benchmarking of the proposed methods with the prior-art solutions is performed in terms of parameter sensitivity and model accuracy with a case study on a 30-MW MMC system. Experiments are carried out on a specifically designed scaled-down system to verify the electro-thermal aspects. Index Terms-Insulated gate bipolar transistor (IGBT), modular multilevel converter (MMC), power semiconductor, reliability, thermal stress estimation, thermal design.

Power Electronics Reliability: State of the Art and Outlook

“…This simplifies the modeling at different timescales by coordinating different thermal time constants and the frequencies of power loss profiles. In [94], a simplification method is proposed for thermal modeling with periodic power loss profiles. An analytical error model is derived for different degrees of simplifications.…”

“…An analytical error model is derived for different degrees of simplifications. Because the ambient temperature change is relatively slow, IGBT module junction temperatures are assumed to change simultaneously with the ambient temperature in [93,94]. Nevertheless, the thermal time constants of capacitors or large heatsinks range from a few minutes to hours, which are comparable with ambient temperature dynamics.…”

Performance Assessment of Grid Forming Converters Using Different Finite Control Set Model Predictive Control (FCS-MPC) Algorithms

“…In order to perform the assessment, a three-phase voltage source converter (VSC) has been used, as shown in Figure 1. The simulation study has been performed by developing a loss model using a PLECS circuit to make a preliminary investigation and obtain the losses distribution in each strategy [16,17]. The purpose of this paper is not only to show how the selected MPC algorithms are influencing the converter efficiency, but also to highlight their preferences.…”

Development of a Hardware Simulator for Reliable Design of Modular Multilevel Converters Based on Junction-Temperature of IGBT Modules

“…The MMC has many advantages, such as low voltage stress in the switching device, a small amount of electromagnetic interference noise, and high output quality (close to an ideal sinusoidal output waveform) [5,6]. To improve the performance and efficiency of the MMC, numerous methods have been employed such as capacitor-voltage balancing control [7,8], modulation schemes [9,10], fault tolerance [11], thermal modeling [12], and lifetime-prediction modeling [13]. HVDC and MVDC systems using MMCs operate in harsh environments, because they are exposed to the outside; and operating the MMCs for a long time increases the probability of failure.…”

“…For the MMCs, the shape of current flowing to the IGBT is different from the typical inverter system. In contrast to the conventional converter, the arm current is composed of a direct-current (DC) component as well as an AC component [12,22]. Owing to the DC offset, the current flowing to each IGBT chip and diode in the IGBT module has a different shape and duration.…”