Fault Diagnosis and Tolerant Control of Single IGBT Open-Circuit Failure in Modular Multilevel Converters

Abstract

Abstract-The modular multilevel converter (MMC) is distinguished by its modularity, that is the use of standardized submodules (SMs). To enhance reliability and avoid unscheduled maintenance, it is desired that MMC can remain operational without having to shut down despite some of its SMs are failed. Particularly, in this paper, a complete fault diagnosis and tolerant control solution, including the fault detection, fault tolerance, fault localization, and fault reconfiguration, has been proposed to ride through the IGBT open-circuit failures. The fault detection method detects the fault by means of state observers and the knowledge of fault behaviors of MMC, without using any additional sensors. Then MMC is controlled in a newly proposed tolerant mode until the specific faulty SM is located by the fault localization method, thus no overcurrent problems will happen during this time interval. After that, the located faulty SM will be bypassed while the remaining SMs are reconfigured to provide continuous operation. Throughout the fault periods, it allows the MMC to operate smoothly without obvious waveform distortion and power interruption. Finally, experimental results using a single-phase scaled-down MMC prototype with six SMs per arm show the validity and feasibility of the proposed methods. Index Terms-Fault diagnosis, fault tolerance, insulated gate bipolar transistor (IGBT), modular multilevel converter (MMC), open-circuit failure, redundancy, state observer, submodule (SM).

Reverse-blocking modular multilevel converter for battery energy storage systems

“…Unbalanced SOC of battery banks may cause premature failure after extended cycling due to overcharging or undercharging of batteries. The flat relationship of battery SOC as a function of their voltage, over a wide range of voltages, indicates the need for a SOC balancing algorithm that does not rely on the voltages [30,31]. Thus SOC control in RB-MMC-BESSs is one of the main differences compared to conventional MMCs.…”

The Fault Detection, Localization, and Tolerant Operation of Modular Multilevel Converters with an Insulated Gate Bipolar Transistor (IGBT) Open Circuit Fault

“…In Reference [16], the Kalman filter was used to optimally estimate the state of an MMC and then detect the fault based on comparisons between the measured states and the estimated states. State observer based and other observer-based fault detection and location methods were developed in References [17][18][19][20], which were used to provide an estimation of the states of an MMC and detect the fault by large difference comparisons. In Reference [17], a fault detection method based on the output current and the circulating current observers and a fault localization method based on the faulty SM capacitor voltage exceeding the set threshold were proposed.…”

“…State observer based and other observer-based fault detection and location methods were developed in References [17][18][19][20], which were used to provide an estimation of the states of an MMC and detect the fault by large difference comparisons. In Reference [17], a fault detection method based on the output current and the circulating current observers and a fault localization method based on the faulty SM capacitor voltage exceeding the set threshold were proposed. However, this method is restricted to the phase-shifted carrier-based pulse width modulation (PWM) strategy and an inevitable and unpredictable delay time for the faulty SM capacitor voltage increasing would affect the fault localization speed.…”

Fault Detection and Location of IGBT Short-Circuit Failure in Modular Multilevel Converters

“…Fault occurrence is verified by comparing the observed and the measured states based on a switching model of every SM, then the SMO equations are modified to detect the faulty SM. Reference [17] proposed a fault diagnosis and tolerant control method and the fault diagnosis method detected the fault by a state observer and the knowledge of fault behaviors. In [18], a Kalman Filter (KF) was employed to detect the fault through comparing the measured state value and the estimated state value by KF and the faulty SM was located based on the voltage comparison between the faulty SM and the normal SMs.…”

“…In [18], a Kalman Filter (KF) was employed to detect the fault through comparing the measured state value and the estimated state value by KF and the faulty SM was located based on the voltage comparison between the faulty SM and the normal SMs. Reference [16][17][18] detected the fault by the changes of the circulating current, but the circulating current could also be influenced by other fault types, which may cause misjudgment. Moreover, SMO and KF require complex algorithm, huge computation and complex parameter setting.…”