Ehsan Jamshidpour

Open- and Short-Circuit Switch Fault Diagnosis for Nonisolated DC–DC Converters Using Field Programmable Gate Array

Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc-dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For validation, computer simulations are first carried out. The proposed detection scheme is validated on a boost converter. Effects of input disturbances and the closed-loop control are also considered. In the experimental setup, a field programmable gate array digital target is used for the implementation of the proposed method, to perform a very fast switch FD. Results show that, with the presented method, FD is robust and can be done in a few microseconds.

Photovoltaic Systems Reliability Improvement by Real-Time FPGA-Based Switch Failure Diagnosis and Fault-Tolerant DC–DC Converter

The increased penetration of photovoltaic (PV) systems in different applications with critical loads such as in medical applications, industrial control systems, and telecommunications has highlighted pressing needs to address reliability and service continuity. Recently, distributed maximum power point tracking architectures, based on dc-dc converters, are being used increasingly in PV systems. Nevertheless, dc-dc converters are one of the important failure sources in a PV system. Since the semiconductor switches are one of the most critical elements in these converters, a fast switch fault detection method (FDM) is a mandatory step to guarantee the service continuity of these systems. This paper proposes a very fast FDM based on the shape of the inductor current associated to fault-tolerant (FT) operation for boost converter used in PV systems. By implementing fault diagnosis and reconfiguration strategies on a single field-programmable gate array target, both types of switch failure (open- and short-circuit faults) can be detected, identified and handled in real time. The FDM uses the signal provided by the current sensor dedicated to the control of the system. Consequently, no additional sensor is required. The proposed FT topology is based on a redundant switch. The results of hardware-in-the-loop and experimental tests, which all confirm the excellent performances of the proposed approach, are presented and discussed. The obtained results show that a switch fault can be detected in less than one switching period, typically around 100 ms in medium power applications, by the proposed FDM.

Distributed Active Resonance Suppression in Hybrid DC Power Systems Under Unbalanced Load Conditions

Power-electronics-based hybrid dc power systems (HDCPSs) are increasingly used in many industrial applications such as land, sea, and air vehicles. In these systems, small dc-link and LC filter capacitors are of great interest for weight saving. Usually, in HDCPSs, there are constant power loads and negative dynamic impedance of these loads may generate unstable oscillations. Besides, the risk of resonance may be increased under unbalanced load conditions. In this paper, a distributed active oscillation suppression approach is presented. It is based on the analytical study of the linearized model of the studied system around the operating point. The studied system consists of one main dc source and one storage element supplying two loads: a permanent magnet synchronous motor connected to the dc link by a voltage source inverter and a resistive load supplied by a dc/dc converter through the same dc bus. The proposed approach is particularly used to overcome the resonance under unbalanced load conditions and allows reducing dc link and LC filter capacitors for weight saving. Simulations and experimentations are carried out which confirm the validity of the proposed approach.

Single-Switch DC–DC Converter With Fault-Tolerant Capability Under Open- and Short-Circuit Switch Failures

This paper proposes fault-tolerant (FT) operation of a single-switch dc-dc converter under a switch failure. In order to improve the reliability in critical applications, FT operation is mandatory to guarantee service continuity. The FT operation of a power system can be performed in three steps: fault diagnosis (detection and identification) and remedial actions. In the case of a switch failure, suitable fault detection is essential to avoid its propagation to the whole system. This study is based on a fast and efficient open- and short-circuit switch fault diagnosis. Both types of switch failure can be detected, identified, and handled in real time by implementing fault diagnosis and reconfiguration strategies on a field-programmable gate array target. No additional sensor is required to perform the fault detection. A redundant switch and a bidirectional switch are needed for converter reconfiguration in postfault operation. The results of hardware-in-the-loop and experimental tests, which all confirm the good performances of the proposed approach, are presented and discussed.

FPGA based fault detection and fault tolerance operation in DC-DC converters

Single-ended non-isolated DC-DC converters are used in embedded and safety critical applications. In more applications like airplanes, trains, electric vehicles, ships and distributed power systems fast fault detection is a mandatory step in order to make a suitable response to a switch fault. On the other hand, a fault tolerant topology is necessary to prevent further damage and to guaranty continuity of service. This paper proposes a very fast and efficient open circuit switch fault detection method associated to fault tolerant converter topology. Fault detection method is based on the shape of the inductor current. To perform very fast switch fault detection a Field Programmable Gate Array (FPGA) digital target is used for the implementation of the proposed method and control. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. Results show that the proposed method is fast, robust, and can be done in a few microseconds.

Fault tolerant operation of single-ended non-isolated DC-DC converters under open and short-circuit switch faults

Fault tolerant operation of single-ended non-isolated DC-DC converters used in embedded and safety critical applications is mandatory to guaranty service continuity. This paper proposes a new, fast and efficient FPGA-based open and short-circuit switch fault diagnosis asssociated to fault tolerant converter topology. The results of Hardware-In-the-Loop and experimental tests are presented and discussed.

Distributed stabilization in DC hybrid power systems

Nowadays Distributed Power Systems (DPSs) are used in different applications such as aerospace industry, submarines, ships and hybrid electric vehicles. However, interaction between the converters in these technologies, also create new challenges like instability due to the “Constant Power Loads” (CPL). In this paper, the small-signal analysis results of a DC hybrid power system are presented. This system is constituted of two load-converters with tight regulation, that exhibit CPL behavior and a battery with a DC-DC converter that are connected to a DC network. A distributed linear stabilization approach is considered to increase the reliability of the system; hence, an oscillation compensation technique is proposed to improve the stability margin of the system. Simulation and experimentation confirm the validity of the proposed approach.

Switch failure diagnosis based on inductor current observation for boost converters

ABSTRACT Face to the growing number of applications using DC–DC power converters, the improvement of their reliability is subject to an increasing number of studies. Especially in safety critical applications, designing fault-tolerant converters is becoming mandatory. In this paper, a switch fault-tolerant DC–DC converter is studied. First, some of the fastest Fault Detection Algorithms (FDAs) are recalled. Then, a fast switch FDA is proposed which can detect both types of failures; open circuit fault as well as short circuit fault can be detected in less than one switching period. Second, a fault-tolerant converter which can be reconfigured under those types of fault is introduced. Hardware-In-the-Loop (HIL) results and experimental validations are given to verify the validity of the proposed switch fault-tolerant approach in the case of a single switch DC–DC boost converter with one redundant switch.

MPPT and output voltage control of Photovoltaic systems using a Single-Switch DC-DC converter

This paper presents the simultaneous Maximum Power Point Tracking (MPPT) and output voltage regulation of a stand-alone Photovoltaic-battery-load power system, based on a Single-Switch DC-DC converter. In the literature, the well-known two-stage buck converter cascaded with a buck-boost one is mentioned as the most suitable non-isolated DC-DC converter for such a Photovoltaic (PV) system. Based on an unified approach to develop Single-Stage power converters, we propose to use an equivalent Single Switch Converter (SSC) for the studied PV system, thus increasing its reliability and decreasing the overall system cost, thanks to the reduced number of switches. In the same spirit, the MPPT algorithm has been chosen among the most used ones. The Perturb and Observe (P&O) algorithm appears as the best compromise, performing good tracking factor, simple implementation and satisfactory accuracy. The resulting PV system has been modeled and simulated; the results confirm the effectiveness and the robustness of the simultaneous MPPT and output voltage regulation.

Energy management and control of a stand-alone photovoltaic/ultra capacitor/battery microgrid

In this paper, the aggregation and implementation of a new energy management method in a microgrid power system is presented. The energy management is based on the use of a hybrid storage system. The Ultra Capacitors are used for facing high frequency variation of the load, such as in transient state, while the batteries are in charge of slow load /source variations. Then early ageing of the batteries are avoided. The advanced control system proposed in this study allows to choose the suitable storage element in order to face correctly the production/consummation variation. The whole system, including PV generator, hybrid storage system and a realistic load, all connected to a common DC-bus, is first modeled. The simulations by using Matlab are then carried out which confirm the good performances of the proposed energy management and associated control system.