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Open-Loop Synchronization Systems for Grid-Tied Power Converters: Literature Overview, Design Considerations, Advantages, and Disadvantages

Authors: S. Golestan, J. M. Guerrero, Y. Al-Turki, A. M. Abusorrah and J. C. Vasquez Extended Abstract: With the ever-increasing penetration of power electronics converters into power systems in recent years, grid connection codes have enforced more stringent requirements on these converters. Fulfilling these requirements using the phase-locked loop (PLL) concept, which is currently the central concept in designing grid synchronization systems, can sometimes be challenging. To improve the speed/accuracy trade-off of closed-loop synchronization systems (especially PLLs), designing open-loop synchronization (OLS) systems for grid-tied power converters has received attention recently. This article provides a unified summary of recent progress in designing OLS systems. It shows that recent contributions in designing filtering stages and correction systems, which are the key elements of OLS algorithms, are mostly equivalent (or, at least, very similar) concepts/methods. Based on these findings, different OLS systems are combined into some general structures as shown below and comprehensive design guidelines are provided. Directions for future research in the area are also provided in the article. All in all, in scenarios where an improved speed/accuracy tradeoff is required, an OLS algorithm (if designed wisely) might be advantageous over a PLL and therefore deserves to be considered/investigated as an ...
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Review on Single-DC-Source Multilevel Inverters: Topologies, Challenges, Industrial Applications, and Recommendations

Authors: M. Trabelsi, H. Vahedi and H. Abu-Rub Extended Abstract: Having a reduced number of switches and isolated DC sources yet generating a higher number of voltage levels has been always the challenge when selecting the appropriate Multilevel Inverter (MLI) topology. Nowadays, Single-DC-Source Multilevel Inverter (SDCS-MLI) topologies are being considered as more suitable for many power system applications such as Renewable Energy (RE) conversion systems and electrified transportations compared to the Multiple-DC-Source MLIs (MDCS-MLIs). Moreover, increasing the power rating and minimizing the switching frequency while maintaining reasonable power quality using a SDCS-MLI is an important requirement and a persistent challenge for the industry. Thus, this paper presents a general review on the available SDCS-MLI topologies and future trends. Existing solutions are discussed and analyzed based on their topologies, number of output voltage levels, number of active/passive components, advantages/limitations, maturity, and industrial applications. Furthermore, recommendations for future research and development are suggested in this paper. Accordingly, the objectives of this paper are listed as follows.
  1. To review the available SDCS-MLIs.
  2. To discuss the merits and limitations of each SDCS-MLI.
  3. To presents potential industrial applications for each topology.
  4. To give recommendations for further research and development.
This paper has ...
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Design of a SAE Compliant Multicoil Ground Assembly

Authors: Feiyang Lin, Grant A. Covic and Morris Kesler Extended Abstract: Inductive power transfer is a technology that enables power to be transferred from a primary (ground assembly) to a secondary (vehicle assembly) without a physical connection, simplifying the charging process. Recommended practice proposed by the SAE J2954 working group has put flux limitations for human exposure in stationary electric vehicle charging applications, constraining it to 27 μT RMS. In this article, a complete interoperability test is performed for the UGA and each of the vehicle assemblies presented in the SAE J2954 document. A new multicoil ground assembly (MCGA) is also proposed to reduce the leakage flux. The MCGA can decrease the flux levels by over 25% while enabling interoperable operation with all of the proposed vehicle assemblies proposed in the standards. As such, all the vehicle assemblies studied can meet the EMF requirements. In this work, the ground assembly is the main contributor to leakage flux, except when the DDP WPT3/Z3 secondary vehicle assembly becomes the main contributor. The proposed MCGA is also able to provide similar dc–dc efficiencies compared to the existing Universal Ground Assembly of >89% at the most misaligned point. Additional information: This work was done by ...
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Terminal Sliding Mode Control – An Overview

Authors: Xinghuo Yu; Yong Feng; Zhihong Man Extended Abstract: Sliding mode control (SMC) has been a popular control technology due to its simplicity and robustness against uncertainties and disturbances since its inception more than 60 years ago. Its foundation of stability and stabilization is built on the principle of the Lyapunov theory, which ascertains asymptotic stability. In the 1990s, a novel class of SMC called the terminal sliding mode control (TSMC) was proposed, which has been studied extensively, giving rise to a robust control with tunable finite-time convergence to deliver fast response, high precision, and strong robustness. The benefit of TSMC is brought out by using a simple fractional power to ramp up the control force to accelerate convergence when near the target. In recent years, interest in this control technology has been increasing. The uptake of TSMC was reported in many applications such as control of an upper limb exoskeleton, ankle movement using functional electrical stimulation of agonist-antagonist muscles, spacecraft altitude control, missile guidance, control of near space hypersonic vehicles, robots, renewable energy and storage systems, power electronics and power systems, to name just a few. This paper provides an overview of the state of the art of the ...
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Family of Transformerless Active Switched Inductor and Switched Capacitor Ćuk DC–DC Converter for High Voltage Gain Applications

Authors: António Manuel Santos Spencer Andrade, Tiago Miguel Klein Faistel, Ademir Toebe, and Ronaldo Antonio Guisso Extended Abstract: This article presents a family of transformerless active switched inductor and switched capacitor Ćuk high voltage gain dc–dc converters. The configuration of this family has the advantages of nonpulsating output current, high step-up voltage gain, low voltage, and current stress across the component. Thus, conduction losses are decreased owing to the low-voltage-rating of the semiconductors. The Ćuk converter with two switched-capacitor cells is evaluated in detail. The experimental results are provided to verify the theoretical analysis. This paper is published in IEEE Journal of Emerging and Selected Topics in Industrial Electronics. Check full paper at: ...
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Hierarchical Abstraction of Compensator for Reaction Torque Observer Based on Element Description Method

Authors: Issei Takeuchi and Seiichiro Katsura Extended Abstract: The expansion of the applicable range of robots and machines requires the ability to cooperate with humans and adapt to external environments. It is necessary to use torque information in order to achieve these capabilities. A reaction torque observer is one of the effective methods to obtain torque information because it does not need a torque sensor and it can deal with torque information in the high-frequency domain. However, it needs a correct compensator to reject disturbances to estimate the precise torque. Generally, the disturbance compensator of the reaction torque observer is derived by manual model selection and manual/automatic parameter fitting. This method not only takes time and effort but also does not always obtain an optimal solution because it depends on a predetermined model. In particular, it is well known that nonlinear elements such as friction are difficult to model. To overcome this issue, an automatic design method of a disturbance compensator is proposed in this article. The compensator is abstracted automatically using an element description method. Using the element description method, model design in advance is not needed because the model selection and the parameter fitting are conducted simultaneously. Therefore, the ...
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Modular Multilevel Converters: Recent Achievements and Challenges

Authors: Marcelo A. Perez; Salvador Ceballos; Georgios Konstantinou; Josep Pou; Ricardo P. Aguilera Extended Abstract: The modular multilevel converter (MMC) is currently one of the power converter topologies, which has largely increased its research and development worldwide. Its features, such as high quality of voltages and currents, highly modular structure, and high voltage rating, have made the MMC a good option for several high-voltage high-power applications, including high-voltage dc (HVdc) transmission, static compensators (STATCOMs), and motor drives. However, its unique features, such as a large number of submodules, floating capacitor voltages, and circulating currents, require a dedicated control system able to manage the terminal variables as well as the internal variables with high dynamical performance. Over the past years, several research studies have been conducted to address the technical challenges associated with the operation and control of the MMC. In this paper, a review of the latest research and development on MMCs is shown, focusing on the challenges and proposed solutions proposed for this power converter still faces in terms of modeling, control, reliability, power topologies, and new applications. This paper has been published in IEEE Open Journal of the Industrial Electronics Society Check full paper at: ...
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Analysis and Design Considerations of a Contactless Magnetic Plug for Charging Electric Vehicles Directly From the Medium-Voltage DC Grid With Arc Flash Mitigation

Authors: Richard B. Beddingfield, Suvendu Samanta, Mark S. Nations, Isaac Wong, Paul R. Ohodnicki Jr., and Subhashish Bhattacharya Extended Abstract: High power electric interconnects are challenging to create safely. Furthermore, disconnecting them while a load is energized can often lead to a localized arc within the plug as the electrical contact is broken. Communication failures can lead to unsafe plug operation in ‘smart’ plugs. Similarly, exposed electrical contacts make medium voltage plugs inherently unsafe. This paper re-envisioned the plug into a gapped magnetic coupling for applications where safety is paramount or MV training is not requisite for general users (e.g. data centers, electric vehicle charging, and harsh environments). This novel magnetic plug guarantees safe operation and connection through galvanic and physical separation from the MV side. It achieves this with a gap and barrier in the transformer core in between the MV and LV windings. We introduce a unique asymmetry in the core to localize parasitic capacitance, fully separating the medium and low voltage regions. This approach eliminates arcing risk and allows high power, MV interconnect capabilities to be delivered to the general public. Detailed results from finite element analysis are presented in the reference along with experimental data to verify operation in an EV charging application. A 20kW, 1kV to 50V ...
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Frequency-Domain Modeling of Dual-Active-Bridge Converter Based on Harmonic Balance Approach

Authors: Sayandev Ghosh, Dhiman Das, Bhim Singh, Sindhu Janardhanan, Sukumar Mishra Extended Abstract: The dual active bridge (DAB) converter contains both AC and DC states. Hence, state space average modeling of DAB is intricate. In the literature, several models of DAB have been developed to reconstruct the AC state. However, full order models provide better accuracy than reduced order models. Frequency domain based modeling captures the total behaviour of the converter such as generalized average modeling (GAM) or series-based solutions. However, with the consideration of more harmonics in the model, derivation of state equations and thus state matrices become tedious. Thus, it poses a limitation in the consideration of the harmonics in the large signal model. This paper proposes a harmonic state space (HSS) modeling framework for DAB that overcomes above obstacles and accurately models both the AC and DC states depending on the inclusion of the number of harmonics in it. The modeling framework described here is applicable to single, dual and triple phase shift modulation schemes. This modeling framework presents a straightforward approach and has a definite structure, which presents flexibility and ease in deriving the input-output relationship. This framework is based on complex form of Fourier series ...
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Performance Supervised Plant-Wide Process Monitoring in Industry 4.0: A Roadmap

Authors: Yuchen Jiang, Shen Yin, Okyay Kaynak Extended Abstract: The intensive research and development (R&D) efforts directed towards large-scale complex industrial systems in the context of Industry 4.0 indicate that safety and reliability issues pose significant challenges. During online operation, system performance degradation will lead, not only to economic losses, but also potential safety hazards. In the existing research and technical routes, the target of the fault diagnosis systems is to trigger alarms to report the fact of the existence of malfunctions as well as the underlying reasons accurately. However, it remains unanswered how urgent it is to fix it, and what degrees of fault-tolerance, maintenance, and fault recovery are needed. Further analyses are necessary to evaluate the impact of the detected fault on the plant-wide performance. In this article, to enable a more comprehensive and precise description of the plant-wide operational status, the roles of the commonly used performance metrics, the state-of-the-art performance evaluation approaches, as well as the performance-oriented and plant-wide process monitoring techniques are investigated. On this basis, an alternative straightforward technical route, embedded in the cyber-physical-social system framework is proposed. The paper rethinks the technical route of plant-wide process monitoring and highlights the alternative research ...
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An Artificial Intelligence Approach for Real-Time Tuning of Weighting Factors in FCS-MPC for Power Converters

Authors: Sergio Vazquez; Daniel L. Marino; Eduardo Zafra; Maria Dolores Valdes Pena; Juan J. Rodriguez-Andina; Leopoldo Garcia Franquelo; Milos Manic Extended Abstract: In this paper a finite control set model predictive control is used to track a current reference in a power converter connected to an RL load. An artificial intelligence (AI) approach is presented for real-time determination of the weighting factor that regulates the average switching frequency, independently of the operating point. The paper focuses on the design, training, and digital implementation of an artificial neural network (ANN) that can be developed in a low-cost control platform. It is presented a sampling and offline ANN training procedure, together with a low-cost hardware implementation based on integer quantization of the ANN. The above approach provides a standalone application, serving as a framework for development of ANN applications for power-converters. The main advantage of the presented approach is that the ANN inference is executed in real-time. In this way, the weighting factor is automatically updated in real-time, allowing the system to quickly adapt to any reference step changes, and consequently provide the desired behavior. Executing the setup in laboratory prototype confirmed the theoretical analysis and successful tracking of the reference frequency. Published in IEEE Transactions on Industrial ...
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A Resonant Frequency Tracking Technique For LLC Converters Based DC Transformers

Authors: Yuqi Wei, Quanming Luo, Alan Mantooth Extended Abstract: Large circulating current and reactive power exist for the LLC / CLLC converter in the case that f s < f r , where f s is the switching frequency and f r is the resonant frequency; on the other hand, in the scenario of f s > f r , the switching losses for both primary and secondary semiconductor devices are increased due to the large turn-off current and high di / dt related reverse recovery issue, respectively. When operating at the natural resonant frequency of inductor and capacitor or f s = f r , the regulation capability for LLC / CLLC converter is lost since the voltage conversion ratio is constant. This application of the LLC is known as a DC transformer (DCX), which has been widely adopted in energy storage systems as an interconnection between different units. However, due to the variation of circuit parameters, the switching frequency is different from the resonant frequency, which results in converter efficiency degradation and loss of output voltage regulation capability for two-stage applications. In this article, by sensing both the output and input voltage, the converter voltage conversion ratio is computed on-line. Based on the comparison result between the calculated gain and unity, the switching ...
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Towards Grid of Microgrids: Seamless Transition between Grid-Connected and Islanded Modes of Operation

Authors: Silvanus D'silva, Mohammad Shadmand, Sertac Bayhan, Haitham Abu-Rub Extended Abstract: With the ever-increasing number of blackouts in distribution systems arising from a variety of natural and manmade disasters, the frequent and necessary isolation/reconnection of loads without power deviations/fluctuations has become an important issue. Grid of microgrids (MGs) is a promising solution towards a highly resilient and efficient power grid operation. To facilitate this implementation, seamless transition with the utility grid is a key feature today’s MG control scheme need to possess. This transition is of great prominence, especially after the accelerated adaptation of distributed renewable energy sources (RES) in MGs. This ability of the MGs should ensure uninterrupted energy services to critical loads and infrastructures. Thus, the implementation of MG control strategies to enable smooth transition between grid-connected (GC) and islanded (IS) operation modes is mandatory. The control scheme implemented should therefore be capable of mitigating the stirring voltage/current deviations due to frequency/phase misalignment during the transition process. This paper provides an overview of the various MG control schemes that enable seamless transition between GC and IS modes of operation. The main purpose of this paper is to provide a generic overview of the challenges and existing techniques available in literature ...
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A Survey on Event-Triggered Sliding Mode Control

Authors: Abhisek K. Behera; Bijnan Bandyopadhyay; Michele Cucuzzella; Antonella Ferrara and Xinghuo Yu Extended Abstract: Event-triggered control (ETC) is a novel strategy for designing controllers for sampled-data systems. Here, by incorporating an event condition in the feedback loop, the data transmission is regulated over the network subject to the satisfactory response of the closed-loop system. Under this feedback constraint, the ETCs have shown promising results, even in the presence of uncertainties/disturbances. Sliding mode control (SMC) is an effective tool for uncertain systems guaranteeing robust performance. In the past decade, many results were reported on the design of event-triggered SMC, which can handle both feedback constraint and disturbance effect. Indeed, a new sliding motion is obtained, known as the practical sliding mode, in which any arbitrary bound for the sliding function can be achieved by appropriately designing the event condition. This paper catalogues almost all developments in event-triggered SMC, from its initial proposal to various applications till the appearance of this paper. We give an overview of the design of classical SMC for both linear and nonlinear systems in the event-triggering framework. The different event-triggering conditions are covered with emphasis on their respective advantages. Some discussion is also presented on the higher-order SMC. The wide application of ...
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ZPUC: A New Configuration of Single DC Source for Modular Multilevel Converter Applications

Saeed Arazm, Kamal Al-Haddad ABSTRACT: Z packed U-cell (ZPUC) converter topology is presented in this paper as a new type of multilevel converter topology that can be operated in a single phase as well as in three-phase configurations while using a single DC source. Since each U-cell includes two switches which operates complimentarily and one capacitor, in this topology, three U-cells are needed to generate 5 or 7 voltage levels. Moreover, the proposed configuration for the ZPUC is more appropriate for high-power application modular multilevel converters (MMCs) to increase the voltage levels compared to other topologies. ZPUC generates unipolar waveform which is highly functional on MMC application to generate higher voltage levels compared to bipolar topologies such as (packed U-cells) PUC and full-bridge (FB). However, it requires DC fault circuit breaker for disconnecting of DC fault current. Moreover, the components count of ZPUC are less than half of the half-bridge (HB) unipolar topology. The remarkable note is that the DC voltage source on ZPUC is divided among the submodules of leg (one phase), while it is divided among the submodules of the arm on the other topologies. This solution reduces the cost, weight, and volume of the ZPUC converter compared ...
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DCM-Based Bridgeless PFC Converter for EV Charging Application

Authors: Abhinandan Dixit; Karan Pande; Sivanagaraju Gangavarapu; Akshay Kumar Rathore Abstract:  On-board battery chargers (OBC) are a crucial part of electric vehicle (EV) industry. OBC comprises of a two-stage structure where front-end converter is a power factor correction (PFC) unit and a back-end DC-DC converter which controls the battery charging process. The front-end converter is the most complex part of the battery charger in terms of control and design. This paper proposes a single-phase switched-mode bridgeless ac-dc buck-boost derived converter that can serve as a front-end converter for the on-board EV charging application. The bridgeless scheme rules out the orthodox bridge rectifier and the affiliated losses. The proposed converter operates in discontinuous current conduction mode (DCM), thus achieving natural power factor correction for variable ac input. In addition to this, sensing of input voltage and input current is fended off because of DCM operation making the converter reliable, cost-effective, and robust compared with conventional continuous current conduction mode converters. Furthermore, the control becomes simple with the employment of a single sensor and the elimination of the phase-locked loop. The proposed front-end converter is well suited for low-voltage battery chargers ranging between 1.0 and 3.3 kW installed in golf-carts and E-rickshaws. A ...
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Isolation barrier design

Gate Drivers for Medium-Voltage SiC Devices

Authors: Anup Anurag, Sayan Acharya, Nithin Kolli and Subhashish Bhattacharya Extended Abstract: Extensive research in wide-bandgap material technology such as silicon carbide (SiC) has led to the development of medium voltage (MV) power semiconductor devices with blocking voltages of 3.3 kV to 15 kV. When these devices are used in various applications, they are exposed to a high peak voltage stress and a very high dv/dt (50 V/ns to 100 V/ns). These impose stringent requirements on the gate driver requiring a high isolation voltage capability along with a high dv/dt ruggedness, which makes it necessary to have an ultra-low coupling capacitance between primary and secondary sides of the isolated gate driver power supply. One of the key issues in achieving this MV isolation pertains to the necessary clearance and creepage requirements, as defined in IEC 61800-5-1 standards. For the successful operation of these gate drivers to be demonstrated in MV converter applications such as Solid-State Transformers [SST], MV grid-connected converters, and MV motor drives, substantial research to improve the gate drivers' performance and provide a plug-and-play solution is needed. This work aims to comprehensively review and develop these gate drivers and consolidate various required design features concerning their galvanic isolation ...
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A Comprehensive Review of the Integration of Battery Energy Storage Systems Into Distribution Networks

Authors: Marco Stecca; Laura Ramirez Elizondo; Thiago Batista Soeiro; Pavol Bauer; Peter Palensky Abstract: Recent developments in the electricity sector encourage a high penetration of Renewable Energy Sources (RES). In addition, European policies are pushing for mass deployment of Electric Vehicles (EVs). Due to their non-controllable characteristics, these loads have brought new challenges in distribution networks, resulting in increased difficulty for Distribution System Operators (DSOs) to guarantee a safe and reliable operation of the grid.  Battery Energy Storage Systems (BESSs) are promising solutions for mitigating the impact of the new loads and RES. In this paper, different aspects of the BESS's integration in distribution grids are reviewed. At first, the physical layer will be considered, focusing on the main battery technologies commercially available and on the power electronics converter. Secondly, the different functionalities that a grid-connected BESS can provide will be investigated, and then its sizing, location and control in distribution network will be discussed. In addition, an overview of actual BESSs installations is given. All in all, this paper aims at providing a comprehensive view of BESSs integration in distribution grids, highlighting the main focus, challenges, and research gaps for each one of these aspects. Published in IEEE ...
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voltage gain graph

A Simple Technique for Fundamental Harmonic Approximation Analysis in Parallel and Series-Parallel Resonant Converters

Authors: Akshay Kumar Rathore, Senior member IEEE, and Venkata R Vakacharla, student member IEEE Abstract The Fundamental Harmonic Approximation (FHA) analysis favored engineers by alleviating obstacles in analysis, loss computation, and optimization by reducing complex resonant converter into a mere Resistance-Inductance-Capacitance (RLC) circuit. However, to improve the power density of an X-ray machine power supply, elimination of filter inductor leaves parallel and series-parallel resonant converters with capacitive filter in output, which forces the Rear End Rectifier (RER) to draw discontinuous currents. These unprecedented discontinuous currents through resonant tanks complicate the FHA analysis, a simple and elegant approach, by forcing it to adopt computer-aided techniques and numerical methods similar to the time domain, state-space, and state-plane approaches. Therefore, all available tools, including traditional FHA, fail to model these converters with reduced complexity and labor. Addressing this issue, this paper presents a technique to restore the simplicity of FHA analysis in the case of parallel and series-parallel resonant converters terminated with capacitive filters. The authenticity, simplicity, and accuracy of the proposed technique are demonstrated through results. Further, a detailed comparison with existing modeling techniques is also provided. This paper is published in IEEE Transactions on Industrial Electronics Check full paper at: ...
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Small-Signal Modeling and Closed-Loop Control of a Parallel–Series/Series Resonant Converter for Wireless Inductive Power Transfer

Authors: Suvendu Samanta ; Akshay Kumar Rathore Abstract: Usually, the parallel-compensated inductive power transfer (IPT) topology fed by a current-source inverter is controlled through variable switching frequency and fixed 50% duty cycle method. This enables the system to operate at resonance frequency, which drifts due to load and other parameter variations. Owing to this control constraint, the load requirements are fulfilled by adding extra dc-dc chopper at the output. This paper presents a new control technique for a parallel-series/series IPT network, fed from a full-bridge current-source inverter to meet the load demand directly by an inverter. Therefore, the extra chopper stage at the output side of the converter is eliminated. The control goals are achieved through a two-loop control method, where the inner input current loop controls the source current and the outer output current loop meets the load requirements. The detailed steady-state operation, converter design, small-signal modeling, and control are reported, and experimental results obtained from a 1.6-kW lab prototype are included to verify the mathematical analysis. This paper is published in IEEE Transactions on Industrial Electronics Check full paper at: ...
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