Real Mission Profile Research Articles

A Reliability-Optimized Maximum Power Point Tracking Algorithm Utilizing Neural Networks for Long-Term Lifetime Prediction for Photovoltaic Power Converters

The reliability of power converters in photovoltaic systems is critical to the overall system reliability. This paper proposes a novel active thermal-controlled algorithm that aims to reduce the rate of junction temperature increase, therefore, increasing the reliability of the device. The algorithm works alongside a normal perturb and observe maximum power point tracking algorithm, taking control when certain temperature criteria are met. In conjunction with a neural network, the algorithm is applied to long-term real mission profile data. This would grant a better understanding of the real-world trade-offs between energy generated and lifetime improvement when using the proposed algorithm, as well as shortening study cycle times. The neural network, when applied to 365 days of data, was 28 times faster than using standard electrothermal modeling, and the lifetime consumption was predicted with greater than 96.5% accuracy. Energy generated was predicted with greater than 99.5% accuracy. The proposed algorithm resulted in a 3.3% reduction in lifetime consumption with a 1.0% reduction in the total energy generated. There is a demonstrated trade-off between lifetime consumption reduction and energy-generated reduction. The results are also split by environmental conditions. Under very variable conditions, the algorithm resulted in a 4.4% reduction in lifetime consumption with a 1.4% reduction in the total energy generated.

Development and Reliability Assessment of Si and SiC Power Devices-Based Solid-State Transformer for Urban Railway Vehicle

A Solid-state transformer (SST) is regarded as a promising alternative to conventional low-frequency (LF) transformers in railway vehicles. Through SST, efficiency improvement and reduction of weight, and volume can be achieved. On the other hand, the cost and reliability are the main concerns of an SST over an LF transformer. Nevertheless, there is a lack of study on the reliability of SST in state-of-the-art research. In this paper, a solid-state transformer for urban railway vehicles is designed by considering different aspects such as cost, efficiency, weight, and volume depending on the number of SST modules. Then, a full-scale prototype of Si and SiC power devices-based SST modules is developed and its operation is experimentally verified. Finally, the system-level reliability of the designed SST is assessed based on two real mission profiles of urban railway vehicles by focusing on the lifetime of different power devices.

Reliability-Oriented Design of Modular Multilevel Converters for Medium-Voltage STATCOM

Modular multilevel converters (MMC) are complex systems, composed of many elements, and exposed to critical load demands in some cases. Thereby, a detailed design of its components is of preeminent importance to achieve a high system-level reliability. However, the high number of devices challenges the tradeoff between cost and reliability. This article, introduces a reliability-oriented design methodology, based on the cost to achieve a predefined unreliability level ( $U_x$ ). A flowchart presents the main steps of the process, including the mission profile definition, selection of power devices, thermal modeling, reliability modeling, and the reliability-oriented selection. To evaluate the proposed methodology, a case study considering 17 MVA/13.8 kV MMC-static synchronous compensator (STATCOM) with a real mission profile data is conducted. A $U_x - cost$ map is introduced to compare various design solutions, based on power devices of different voltage classes and current capabilities.

Reliability evaluation of PV converter based on modified hybrid power control method

With the increasing proportion of photovoltaic grid-connected systems in the global power system, many advanced active power control strategies have been introduced into power network management. In this paper, a hybrid method to optimize power control for two-stage PV converter is proposed. The proposed method adopts the mixed modulation strategy of maximum power point tracking (MPPT) control and Power Reserve Control (PRC). In this method, the power devices of the inverter have a relatively alleviated junction temperature stress, and thereby the reliability of the power devices are enhanced. The reliability of the converter using proposed method is predicted under a real mission profile in photovoltaic application.

Reliability analysis of the optimized Y-source inverter with clamping circuit

Y-source inverter has been proposed for a few years, but it still has some drawbacks. So, many studies of related topologies have been carried out to address the issues of traditional Y-source inverter (T-YSI). This paper proposes an optimized topology of Y-source inverter to solve the problems such as discontinuous input current and dc-link voltage spikes. However, the additional circuits probably influence the electrical and thermal stress of the IGBT modules, which affect their lifetime. And the lifetime of IGBT modules contribute to the lifetime of the inverter. Thus, it is important to predict the lifetime of the inverter based on the lifetime of the IGBT module. The lifetime of the IGBT modules is predicted by using the Coffin-Manson-Arrhenius model. The thermal behaviour is obtained considering real mission profile. Then the reliability of the IGBT module in the optimized Y-source inverter with clamping circuit is derived using Weibull distribution. Finally, the lifetime of the proposed inverter is analysed by Reliability Block Diagram (RBD) based on component-level reliability.

Zero-emission casting-off and docking maneuvers for series hybrid excursion ships

Ecological areas visits require appropriate management of key ecological features. In protected reserves innovative systems should be developed to facing problems of pollution, exhaust fumes and noise. These underlying conditions lead to special challenges for excursions ships. The switching to a cleaner, safer and quieter transport system seems to be a sustainable long-term solution for the problems of ecological areas, where more electric ship can be an important part of the solution and principally for the last mile. This paper presents a design approach of a hybrid Energy Storage Systems (ESS) for new generation of series hybrid excursion ship devoted to ecological areas to avoid any emission during the casting-off and the docking maneuvers. The main purpose of the paper is to show that, even if the hybrid ESS plus series-hybrid propulsion were already used to other vehicles, the gain for a ship with no regenerative capability is not evident. The proposed hybridization is built upon a fully-active parallel topology with battery and supercapacitors. The sizing methodology and the configuration of the ESS are detailed. For a real mission profile in Alster Lake (Hamburg, Germany) it is shown that a small battery pack of 2 kWh with a supercapacitor bank of 0.54 kWh are necessary to have zero-emission maneuvers. The graphical formalism Energetic Macroscopic Representation (EMR) is used to describe the model and to establish an energy analysis tool. An inversion-based control scheme is then deduced from the EMR and simulation results are provided to validate the proposed methodology. The usage of hybrid ESS avoids 1.39 kg of CO2 during the casting-off and docking maneuvers despite increasing consumption of 0.2 l (+8%). However, the plug-in capability can be introduced and a recharge of the battery when the ship is docked could reduce the global consumption and emissions by 20% in comparison to the original ship.

Lifetime prediction of a modified Y-source inverter in photo-voltaic application

Y-source inverter has been proposed for a few years, but it inherits many problems from coupled-inductor impedance-source inverters (CISIs). So, many studies to address the issues of traditional Y-source inverter have been carried out. However, the reliability of a field working Y-source inverter has never been studied. In this paper, a modified topology of Y-source inverter is proposed which can solve the problem of discontinuous input current and increase boost ratio. The reliability of the proposed modified Y-source inverter (M-YSI) is studied using Physics-of-Failure approach. The lifetime of the proposed topology is predicted under a real mission profile in photo-voltaic application.

A Lifetime Prediction Method for LEDs Considering Real Mission Profiles

The light-emitting diode (LED) has become a very promising alternative lighting source with the advantages of longer lifetime and higher efficiency than traditional ones. The lifetime prediction of LEDs is important to guide the LED system designers to fulfill the design specifications and to benchmark the cost-competitiveness of different lighting technologies. However, the existing lifetime data released by LED manufacturers or standard organizations are usually applicable only for some specific temperature and current levels. Significant lifetime discrepancies may be seen in the field operations due to the varying operational and environmental conditions during the entire service time (i.e., mission profiles). To overcome the challenge, this paper proposes an advanced lifetime prediction method, which takes into account the field operation mission profiles and also the statistical properties of the life data available from accelerated degradation testing. The electrical and thermal characteristics of LEDs are measured by a T3Ster system, used for the electrothermal modeling. It also identifies key variables (e.g., heat sink parameters) that can be designed to achieve a specified lifetime and reliability level. Two case studies of an indoor residential lighting and an outdoor street lighting application are presented to demonstrate the prediction procedures and the impact of different mission profiles on the lifetime of LEDs.

Long-Term Reliability of Railway Power Inverters Cooled by Heat-Pipe-Based Systems

This paper analyzes the impact of a nonuniform temperature distribution inside insulated-gate bipolar transistor (IGBT) power modules on the reliability of railway power inverters. The interaction between the chosen cooling system (a heat-pipe-based one) and the power module is considered in detail. After showing the experimental setup and thermal conditions, thermal mapping inside the power module is carried out. Then, the effects of the thermal cycles on the constitutive elements of the IGBT module are pointed out when considering a real mission profile. Finally, the experimental results from the thermal cycles are linked to problems on the power-inverter reliability. Concretely, the thermal-grease distribution is analyzed on failed IGBT modules coming from the field, and the solder-delamination pattern observed in IGBT modules after endurance cycling tests is also reported.

Power Simulation for All Electric Combat Vehicles

Research and development of electric weapons is currently in progress in several countries for their benefits of higher muzzle velocities and insensitive munitions compared with conventional chemical guns. The integration of these weapons aboard land based vehicles will likely require careful consideration of the energy balances and power flows to all of the major loads aboard. Leveraging against ongoing research in electric drive trains capitalizes on a common power system bus and sharing of prime power between these loads, and such conceptual vehicles are classified as "all electric". Early conceptual studies of "all electric" vehicle power systems under the complex dynamic loadings experienced in real mission profiles are needed to optimally configure and size their components. This paper describes a power simulation model built in the Matlab/ Simulink programming environment, which allows these early studies to be rapidly conducted. This tool can also be used to evaluate the relative penalty in mobility and firepower performance for degradation in selected component characteristics, thus highlighting weak links in the power system architecture. An example case study is presented showing the influence of reduced weapon pulsed energy storage on the mobility and firing performance of the vehicle in an offensive type mission profile.