Duty Cycle Limitations Research Articles

Probabilistic performance evaluation of the class-A device in LoRaWAN protocol on the MAC layer

LoRaWAN is a network technology that provides a long-range wireless network while maintaining low energy consumption. It adopts the pure Aloha MAC protocol and the duty-cycle limitation at both uplink and downlink on the MAC layer to conserve energy. Additionally, LoRaWAN employs orthogonal parameters to mitigate collisions. However, synchronization in star-of-star topology networks and the complicated collision mechanism make it challenging to conduct a quantitative performance evaluation in LoRaWAN. Our previous work proposes a Probabilistic Timed Automata (PTA) model to represent the uplink transmission in LoRaWAN. It is a mathematical model that presents the nondeterministic and probabilistic choice with time passing. However, this model remains a work in progress. This study extends the PTA model to depict Class-A devices in the LoRaWAN protocol. The complete characteristics of LoRaWAN’s MAC layer, such as duty-cycle limits, bidirectional communication, and confirmed message transmission, are accurately modeled. Furthermore, a comprehensive collision model is integrated into the PTA. Various properties are verified using the probabilistic model checker PRISM, and quantitative properties are calculated under diverse scenarios. This quantitative analysis provides valuable insights into the performance and behavior of LoRaWAN networks under varying conditions.

A Methodology to Optimize PMSM Driven Solar Water Pumps Using a Hybrid MPPT Approach in Partially Shaded Conditions

Solar water pumps are crucial for farmers, significantly reducing energy costs and providing independence from conventional fuels. Their adoption is further incentivized by government subsidies, making them a practical choice that aligns with sustainable agricultural practices. However, the cost of the required solar panels for the chosen power makes it essential to optimize solar water pumping systems (SWPS) for economic viability. This study enhances the efficiency and reliability of permanent magnet synchronous motor (PMSM)-driven SWPS in rural areas using hybrid maximum power point tracking (MPPT) algorithms and voltage-to-frequency (V/f) control strategy. It investigates the sensorless scalar control method for PMSM-based water pumps and evaluates various MPPT algorithms, including grey wolf optimization (GWO), particle swarm optimization (PSO), perturb and observe (PO), and incremental conductance (INC), along with hybrid combinations. The study, conducted using MATLAB Simulink, assesses these algorithms on convergence time, MPPT accuracy, torque ripple, and system efficiency under different partial shading conditions. Findings reveal that INC-GWO excels, providing higher accuracy, faster convergence, and reduced steady-state oscillations, thus boosting system efficiency. The V/f control strategy simplifies control mechanisms and enhances performance. Considering system non-idealities and maximum duty cycle limitations, PMSM-based SWPS achieve superior efficiency and stability, making them viable for off-grid water pumping applications.

Dual‐input single‐output high step‐up DC–DC converter for renewable energy applications

AbstractThis paper introduces a dual‐input single‐output (DISO) non‐isolated DC–DC converter with the capability to accommodate multiple input ports. It supports both bidirectional and unidirectional power flows. The proposed converter employs the switched‐capacitors (SC) technique, resulting in a high‐ voltage transfer gain. Although the use of the SC technique leads to discontinuous input current, this issue has been addressed by incorporating an inductor at the input side. The DISO high‐voltage gain converter offers flexible control options, reduces current and voltage stress on semiconductors, and imposes no duty cycle limitations due to the proposed switching methods. Furthermore, when Port 2 fails, the proposed converter can transfer energy to the load by sources in Port 1 without interruption. The steady‐state model and small‐signal analysis (SSA) of the proposed converter are examined at continuous conduction mode (CCM). To evaluate accurately, the proposed converter is compared with the recently presented converters based on important characteristics. Additionally, a comprehensive power loss analysis is performed. Following the design specifications, an evaluation and testing of a prototype are conducted to verify the feasibility and performance of the converter.

Tristate Converters with Limited Duty Cycle

Replacing the active switch of a DC/DC converter with a series connection of two active switches and a diode which is connected to the connection point of the two switches, changes the converter into a tristate one. The tristate concept changes the voltage transformation ratio of the original converter and influences the dynamics. Starting from a topology for limited duty cycles, four converters can be derived. There are two possibilities for the position of the second capacitor and so eight converter structures can be achieved. The position of the second capacitor influences the input current, the inrush, the stored energy, and the voltage stress of this component. When the input voltage has the other polarity, again eight converters can be designed. Changing all active electronic switches by current bidirectional ones (an electronic switch with an antiparallel diode) leads to bidirectional converters and increases the number of converters that are derived from the basic topology to thirty-two. The function of the four basic structures is explained, and the voltage transformation ratio calculated and graphically shown. The connections of the currents are explained. For one converter the large and the small signal models and two transfer functions are calculated, and simulation of the dynamics are shown.

Multi‐input multi‐output converter for simultaneous buck and boost voltage conversion

SummaryInternet of Things (IoT) devices, portable electronics, and electric vehicle (EV) accessories have increased the need for DC power distribution with various outputs. Multiport converters (MPCs) handle numerous inputs and loads with fewer components, low power losses, and less cost. Most multi‐input converters are time‐shared and restrict the duty cycle's working range, limiting energy sources and output voltage. Single‐input multi‐output (SIMO) converters have inductor current and duty cycle limits. In this study, a dual‐input dual‐output (DIDO) converter is proposed to overcome the limitations mentioned above. It can operate multiple loads without restrictions on charging inductor currents and cross‐regulation problems. Any variations will not influence the proposed converter's output voltage VO1 (VO2) by the load current iO2 (iO1). To verify the feasibility of the proposed configuration, a 250 W laboratory prototype has been developed, and experimental results are validated.

Analytical traffic model of 6TiSCH using real-time in-band telemetry

In industrial environments, the IETF 6TiSCH stack is a protocol stack consisting of standardized layers (IEEE 802.15.4, TSCH, 6LoWPAN, RPL, CoAP) that enable reliable wireless communications. To efficiently manage the network, gathering insights is critical. This allows for detecting traffic bottlenecks, predicting energy consumption, checking duty cycle limits, adjusting network topology, and identifying interference. As such, detailed knowledge of the traffic quantity can be used to create a digital twin of the network to help prevent node or network failures by re-configuring network parameters. To that end, this paper presents an analytical model to calculate the transmitted and received bytes for every node in a 6TiSCH network, considering the complete 6TiSCH network stack. Real-time in-band network telemetry is used to limit monitoring overhead by piggybacking information onto transmitted data packets. Simulations demonstrate that our model provides accurate predictions with a median of 95 to 99% under various circumstances, such as topology changes and packet loss. The model can enhance network robustness and can be extended to predict the energy consumption of 6TiSCH devices easily.

A Class of Bidirectional Single-Phase Z-Source AC–AC Converter With Continuous Input Current and Reduced Component Count

In this paper, a class of single-phase Z-source ac-ac converters is proposed. Share ground and continuous input current are the common features of the proposed converters. The proposed converters have unique features that differentiate them from their counterparts. These features include the buck operation in both in-phase and out-of-phase mode, being bidirectional, the minimum component counts, the ability to boost without duty cycle limitation, and reducing total power ratting of switches is known as switching device power (SDP) parameter. Reducing SDP leads to a reduction in the voltage and current rating of the semiconductors and consequently to a reduction in converter' cost. A safe commutation strategy is applied to eliminate voltage and current spikes on the switches without snubber circuits. The experimental results verify the performance of the laboratory prototype of the proposed converters.

Third Order Converters with Current Output for Driving LEDs

Light emitting diodes LEDs are highly efficient in changing electrical energy into light. The applications are lightning, but also medical treatments, and disinfection. After a short discussion of the simplest converter which is based on the Buck converter several third order current converters, which are suitable to drive an LED load, are treated. The Buck converter with input filter, the output current Boost converter, and the output current Cuk converter are shortly treated, but for the other topologies simple control techniques are given. These converters are the current output converter based on the Zeta converter, two converters with a quadratic term of the duty cycle in the voltage transformation ratio, the quadratic step-down converter with current output and the D square divided by one minus d current output converter, which is a step-up-down converter, and two converters which function only for a limited duty cycle, the (2d-1)/d step-down and the (2d- 1)/(1-d) step-up-down output current converters. The dynamics of example converters is shown with the help of LTSpice simulations.

Model predictive control of DC/DC boost converter with reinforcement learning

Power electronics is seeing an increase in the use of sophisticated self-learning controllers as single board computers and microcontrollers progress faster. Traditional controllers, such as PI controllers, suffer from transient instability difficulties. The duty cycle and output voltage of a DC/DC converter are not linear. Due to this non-linearity, the PI controller generates variable levels of voltage fluctuations depending on the operating region of the converter. In some cases, non-linear controllers outperform PI controllers. The non-linear model of a non-linear controller is determined by data availability. So, a self-calibrating controller that collects data and optimizes itself as the operation goes on is necessary. Iteration and oscillation can be minimized with a well-trained reinforcement learning model utilizing a non-linear policy. A boost converter's output power supply capacity changes with a change in load, due to which the maximum duty cycle limit of a converter also changes. A support vector calibrated by reinforcement learning can dynamically change the duty cycle limit of a converter under variable load. This research highlights how reinforcement learning-based non-linear controllers can improve control and efficiency over standard controllers. The proposed concept is based on a microgrid system. Simulation and experimental analysis have been conducted on how reinforcement learning-based controller works for DC-DC boost converter.

Steady‐state hybrid extended Kalman filter based sensorless voltage controller for a phase‐shifted full‐bridge converter

This study proposes a steady-state hybrid extended Kalman filter-based control method for sensorless output voltage regulation of a phase-shifted full-bridge DC/DC converter. Unlike the conventional applications, there are some specific cases where the voltage feedback needs to be received indirectly. For example, in wireless power transmission applications, obtaining a “continuous” and real-time feedback without relying only on wireless communication could significantly advance the systems' performance and robustness. Specifically, in this paper, a method that can estimate the output voltage feedback as well as load resistance in real-time for sensorless voltage control is proposed. The approach in this study relies on estimating the output voltage using processed primary current measurement. Although the exemplary converter system is modelled in discontinuous conduction mode (DCM), the method can also estimate the load resistance and provide a stable operation in continuous conduction mode (CCM). However, for very low load resistances which cause limit states such as current control limit or duty cycle limit, method cannot estimate the load resistance properly. Throughout the paper, the modelling framework is first introduced and then the design of the proposed sensorless voltage control scheme is presented. Finally, the algorithm's performance is verified through experimental studies.

A novel time-slotted LoRa MAC protocol for scalable IoT networks

Long Range (LoRa) networks provide long range, cost-effective and energy-efficient communications by utilizing the free unlicensed ISM band, which makes them appealing for Internet of Things (IoT) applications. However, in high density networks, reliable performance might be hard to achieve due to the nodes’ random-access method. Furthermore, the duty cycle restrictions that are imposed on nodes and gateways transmissions can limit the scalability of the network. More importantly, the duty cycle restrictions that are imposed on the downlink communication from the server to nodes can impose further challenges. Consequently, the server in high density networks might not be able to communicate with all network nodes due to its limited duty cycle. Besides, the server might not be able to send individual controlling packets from server to nodes. One way to mitigate such a limit is to allow nodes autonomously determine their transmission parameters without the need for any downlink transmission from the server. Thus, this paper presents the Sector-Based Time Slotted SBTS-LoRa MAC protocol that allows nodes to determine their transmission parameters autonomously based on their location to the gateway. SBTS-LoRa is targeting large scale networks. Simulation results show that our proposed protocol significantly enhances the scalability and outperforms its counterparts by maximizing throughput without compromising the energy efficiency. Specifically, the average throughput for dense networks was enhanced 14 times compared to the Adaptive Data Rate ADR-LoRaWAN.

A Generalized sequential AC/DC power flow algorithm for VSC MTDC system with series interline DC current flow controller

In this paper, a generalized average model for various topologies of series interline power flow controller is developed and incorporated in AC/DC VSC MTDC power flow model. A new Newton Raphson based power flow formulation of AC/DC VSC MTDC system with series interline power flow controller in proposed.The proposed formulation accommodates the inclusion of capacitor voltage limits of Current Flow Controller (CFC), DC line current and duty cycle limits. Steady State feasibility of wind power evacuation is analyzed for different wind power penetration levels and CFC injected voltages. The impact of CFC injected voltages on rerouting and nullifying the power flows in MTDC grid are analyzed for different wind power penetration levels. Initialization of state variables for feasible steady state solution has been addressed. In order to ensure feasible solution a novel convergence criteria is proposed. The validity of the proposed AC/DC power flow formulation is demonstrated on 39 bus AC/DC system.

High voltage power supply controller for Electrostatic precipitators

Gaseous exhausts from various industries pollute the environment with fly-ash generally filtered by electrostatic precipitators (ESPs) before being released to the atmosphere. This paper presents the development of a controller for ESP power supply. The controller maintains the voltage applied to ESP at its maximum average value by duty cycle control that results in an improvement in dust collection-efficiency. The limiting factor for the output voltage is the breakdown of gas (spark/arc) in the electrode gap of ESP. During a spark/arc condition, the duty cycle limit imposed by the controller causes a reduction in output voltage that leads to the prevention of spark/arc. The present design has a response faster than line frequency power supply controllers. The control circuit is simpler, easy to implement and uses a standard PWM controller IC. The design of power stage uses a flyback current-fed push-pull DC-DC converter with multiple secondary circuits, which has the advantages of instantaneous current limit and less voltage stress on rectifier-diodes. Simulation is performed to obtain a 1 kV, 100 W output from a 24VDC source. The results are compared with experimental values to validate the controller’s ability to achieve good load regulation during normal operation and a reduction in output voltage during spark/arc condition.

Impact of Inter-Gateway Distance on LoRaWAN Performance

The large-scale behaviour of LoRaWAN networks has been studied through mathematical analysis and discrete-time simulations to understand their limitations. However, current literature is not always coherent in its assumptions and network setups. This paper proposes a comprehensive analysis of the known causes of packet loss in an uplink-only LoRaWAN network: duty cycle limitations, packet collision, insufficient coverage, and saturation of a receiver’s demodulation paths. Their impact on the overall Quality of Service (QoS) for a two-gateway network is also studied. The analysis is carried out with the discrete-event network simulator NS-3 and is set up to best fit the real behaviour of devices. This approach shows that increasing gateway density is only effective as the gateways are placed at a distance. Moreover, the trade-off between different outage conditions due to the uneven distribution of spreading factors is not always beneficial, diminishing returns as networks grow denser and wider. In particular, networks operating similarly to the one analysed in this paper should specifically avoid SF11 and 12, which decrease the average overall PDR by about 7% at 10% nodes increment across all configurations. The results of this work intend to homogenise behavioural assumptions and setups of future research investigating the capability of LoRaWAN networks and provide insight on the weight of each outage condition in a varying two-gateway network.

Data Link with a High-Power Pulsed Quantum Cascade Laser Operating at the Wavelength of 4.5 µm.

This article is a short study of the application of high-power quantum cascade lasers and photodetectors in medium-infrared optical wireless communications (OWC). The link range is mainly determined by the transmitted beam parameters and the performance of the light sensor. The light power and the photodetector noise directly determine the signal-to-noise power ratio. This ratio could be maximized in the case of minimizing the radiation losses caused by atmospheric attenuation. It can be obtained by applying both radiation sources and sensors operated in the medium infrared range decreasing the effects of absorption, scattering or scintillation, beam spreading, and beam wandering. The development of a new class of laser sources based on quantum cascade structures becomes a prospective alternative. Regarding the literature, there are descriptions of some preliminary research applying these lasers in data transmission. To provide a high data transfer rate, continuous wave (cw) lasers are commonly used. However, they are characterized by low power (a few tens of mWatts) limiting their link range. Also, only a few high-power pulsed lasers (a few hundreds of mWatts) were tested. Due to their limited pulse duty cycle, the obtained modulation bandwidth was lower than 1 MHz. The main goal of this study is to experimentally determine the capabilities of the currently developed state-of-the-art high-power pulsed quantum cascade (QC) lasers and photodetectors in OWC systems. Finally, the data link range using optical pulses of a QC laser of ~2 W, operated at the wavelength of ~4.5 µm, is discussed.

Design of a solar energy harvesting system for supplying energy to an autonomous wireless sensor node

Introduction: This paper is the product of the research “Generation of a modular electronic platform for the conformation of a WSN” developed in the EAFIT University in 2019.
 Problem: Wireless Sensor Networks (WSNs) are used as a technology of information and communication (TIC) to automate processes. Its implementation is considered non-efficient, because of their high cost concerning to the batteries replacement that the nodes conforming the WSN, require.
 Objective: The objective of the research is to develop more efficient solar energy harvesting systems that can guarantee an average performance of the wireless sensor node at a low cost.
 Methodology: Here we present the design and the implementation of a solar energy harvesting system that integrates a buck converter, a maximum power point tracking (MPPT) control, and a wireless sensor node. Besides, we do measures of voltage at the output of the buck converter and estimation of energy autonomy in the wireless sensor node.
 Results: Autonomous operation with the solar energy harvesting system was rich for the node sending packages each 20 min.
 Conclusion: This article presented a solar energy harvesting system with the implementation of an MPPT control.
 Originality: Through this research, parameters of the MPPT control are formulated for the first time for the solar energy harvesting system design, based on the duty cycle limits.
 Limitations: The availability of the devices used in the implementation of the proposed design.

Model-Based Design of a Pseudo-Cogenerative Heating System for e-Boat Battery Cold Start

Full-electric boats are an expression of recent advancements in the area of vessel electrification. The installed batteries can suffer from poor cold-start performance, especially in the frigid season and at higher latitudes, leading to driving power limitations immediately after startup. At state, the leading solution is to adopt a dedicated heater placed on the common cooling/heating circuit; this implies poor volume, weight, and cost figures, given the very limited duty cycle of such a part. The Heater-in-Converter (HiC) technology allows removing this specialized component, exploiting the power electronics converters already available on board: HiC modulates their efficiency to produce valuable heat (pseudo-cogeneration). In this work, we use the model-based approach to design this system, which requires heating power minimization to fulfill power electronics limitations, while guaranteeing the user-expected startup time to full power. A multistage model is used to get the yearly vessel temperature distribution from latitude information and some additional data. Then, a lumped parameter for the cooling/heating circuit is used to determine the minimum required power as a function of the properties of the thermal interface material used for the battery coupling. The design is validated on a 1:5 test bench (battery power and energy), which demonstrates how the technology can be to scaled up to also fit different boats and battery sizes.

Asymmetrical PWM Series-Capacitor High-Conversion-Ratio DC–DC Converter

In this letter, an asymmetrical pulsewidth modulated (PWM) scheme is proposed to solve the inductor current unbalance and nonlinear voltage gain issues of the series-capacitor (SC) high-conversion-ratio (HCR) converter when D > 0.5. With the proposed scheme, the converter can achieve both current balancing and high step-down conversion even for D > 0.5. As a result, combined with the conventional PWM scheme, the duty cycle limitation of the SC-HCR converter is completely eliminated. A 2-kW prototype SC-HCR converter was fabricated and tested to validate the performance of the proposed PWM scheme.

Energy Efficiency of Slotted LoRaWAN Communication With Out-of-Band Synchronization

Although the idea of using wireless links for covering large areas is not new, the advent of LPWANs has recently started changing the game. Simple, robust, narrowband modulation schemes permit the implementation of low-cost radio devices offering high receiver sensitivity, thus improving the overall link budget. The several technologies belonging to the LPWAN family, including the well-known LoRaWAN solution, provide a cost-effective answer to many Internet-of-things (IoT) applications, requiring wireless communication capable of supporting large networks of many devices (e.g., smart metering). Generally, the adopted MAC strategy is based on pure ALOHA, which, among other things, allows to minimize the traffic overhead under constrained duty cycle limitations of the unlicensed bands. Unfortunately, ALOHA suffers from poor scalability, rapidly collapsing in dense networks. This work investigates the design of an improved LoRaWAN MAC scheme based on slotted ALOHA. In particular, the required time dissemination is provided by out-of-band communications leveraging on FM-RDS broadcasting. An experimental setup based on low-cost hardware is used to characterize the obtainable synchronization performance and derive a timing error model. Consequently, improvements in success probability and energy efficiency have been validated by means of simulations in very large networks with up to 10000 nodes. It is shown that the advantage of the proposed scheme over conventional LoRaWAN communication is up to 100% when short update time and large payload are required. Similar results are obtained regarding the energy efficiency improvement, which is close to 100% for relatively short transmission intervals and long message duration; however, due to the additional overhead for listening to the time dissemination messages, efficiency gain can be negative for short-duration messages fastly repeating.

Stability analysis and duty cycle limitation of grid‐connected current control strategy for multiple parallel three‐level T‐type grid‐connected inverters

Stability analysis and duty cycle limitation of grid‐connected current control strategy for multiple parallel three‐level T‐type grid‐connected inverters