Duty Cycle Control Strategy Research Articles

A Three-Phase Single-Stage ac/dc Converter Based on Swiss Rectifier and Three-Level LLC Topology

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter is widely used due to its soft switching, high power density, and high efficiency. To incorporate the merits of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant tank into a three-phase single-stage ac/dc converter, this article proposes a three-phase single-stage ac/dc converter based on Swiss rectifier and three-level <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> topology. It takes advantage of the high-efficiency Swiss rectifier to convert three-phase ac voltages into three variable dc voltages and interface a three-level <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant circuit. With help of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant tank, all the high-frequency three-level switches achieve soft switching. To both regulate the output voltage and achieve three-phase power factor correction, the frequency modulation in combination with the duty cycle control strategy is employed by splitting the resonant current into three parts and then forming three phase sinusoidal currents. The proposed converter's detailed operation principles, steady-state characteristics, and design considerations are given. Finally, a 10 kW experimental prototype with three-phase 220 Vac inputs and 500 Vdc output is built to verify the effectiveness and feasibility of the proposed topology and its control strategy.

Duty Cycle Control Strategy for Dual-Side LCC Resonant Converter in Wireless Power Transfer Systems

The dual-side inductor–capacitor–capacitor (LCC) topology circuit has been widely adopted in wireless power transfer (WPT) systems due to its constant output current characteristic. However, most conventional control methods need specific synchronization techniques between the primary and secondary sides to avoid the oscillation in the system, which increases the cost and control complexity. To solve this issue, this article proposes a new duty cycle control (DCC) strategy for a dual-side LCC resonant converter with a semibridgeless active rectifier (SAR). With such a control strategy, gate signals of the primary- and secondary-side circuits do not need to be synchronized, which could reduce the complexity and the cost of the WPT system. Besides, the switching frequency of the secondary side can be decreased significantly. This article first presents the modal analysis of phase shift control (PSC) and DCC. Then, generalized state-space averaging (GSSA) modeling with PSC and the hybrid average modeling with DCC are performed. In addition, controllers’ design for both strategies is conducted to achieve the constant output voltage. Finally, the eigenvalues’ analysis is used to determine the stability region of the WPT system. The theoretical analysis has been validated by both simulation and experimental results.

Comparative Analysis of Torque Ripple for Direct Torque Control based Induction Motor Drive with different strategies

ABSTRACT Direct Torque Control (DTC) method is one of the most outstanding and proficient control techniques of the induction motor. The foremost drawback of DTC induction motor drive is high torque pulsation, variable frequency of inverter switching. The main reason of torque pulsation is torque and flux hysteresis band utilised in DTC. DTC method is utilising hysteresis comparators which produce high torque pulsation and unpredictable switching frequency. In this paper, torque ripple analysis of fuzzy logic controller (FLC) based Direct Torque Control (DTC) of three-phase induction motor drive has been discussed. The space vector pulse width modulation (SVPWM) based DTC technique, which operates with the regular switching frequency, helps to solve the fundamental issues of torque pulsation. In addition to this, literature proposes different solutions like a prediction scheme, fuzzy logic controller technique, global minimum torque ripple strategy, constant frequency torque controller (CFTC) Technique, optimal switching instant scheme, duty cycle control scheme, SVPWM DTC for torque ripple reduction. The fuzzy logic controller capabilities for DTC technique are applied with the induction motor (IM) drive for high-performance applications. The simulation results of Conventional DTC, SVPWM DTC, Carrier SVPWM DTC and FLC-DTC method for the induction motor are illustrated. Fuzzy-based DTC technique compared with CSVPWM DTC method and conventional DTC method are presented. The torque ripple of 7.4% for 5 HP induction motor is achieved by FLC-based DTC method. Hardware results for DTC induction motor drive are also demonstrated and discussed. This paper presents improvement in torque ripple reduction with the help of carrier space vector pulse width modulation (CSVPWM) and FLC-based DTC.

Model predictive duty cycle control for three‐phase Vienna rectifiers

The Vienna rectifiers are widely used in industrial applications. The computationally efficient optimal switching sequence model predictive control directly optimizes the switching sequences. Thus, it requires to store the switching states of 25 voltage vectors, which increases the memory usage. Moreover, the neutral-point (NP) voltage is regulated by redundant vector preselection. As only one redundant vector is applied during the whole sampling period, the NP voltage ripple is relatively large, and the grid current performance is still not satisfactory. To overcome these drawbacks, this paper proposes a model predictive duty cycle control strategy for three-phase Vienna rectifiers, which directly optimizes three-phase duty cycles. The three-phase duty cycles are first obtained by predicting the effects of three-phase duty cycles on instantaneous current variations and minimizing a cost function. To guarantee the grid current performance, a novel three-phase duty cycles modification method is proposed by considering the structural characteristics of the Vienna rectifier. To suppress the NP voltage ripple, the obtained three-phase duty cycles are further optimized. With the proposed method, low memory usage, low harmonic distortion in the grid current, and low NP voltage ripple are achieved simultaneously. Experiments are conducted to verify the effectiveness of the proposed method.

ADCC: An effective adaptive duty cycle control scheme for real time big data in Green IoT

Currently, large number of devices have been connected to the Internet of Things (IoT). Ubiquitous IoT devices encounter emergencies and generate much data which may lead to congestion and urgency to be processed timely. To alleviate it, many approaches have been proposed and Adaptive Duty Cycle Control (ADCC) scheme is an effective one. The main contributions of this paper are as follows: (a) Unlike previous studies that mostly the efficiency of congestion control and real-time processing is experiment-oriented, specially, this paper theoretically gives a targeted optimization of duty cycle ratio, which can effectively guide the design of ADCC scheme for real time big data. (b) A general design principle is proposed to guide the scheme designing in order to improve the efficiency and performance of networks. (c) A comprehensive congestion avoidance and real-time processing scheme combining dynamic duty cycle adjustment and full utilization of residual energy is proposed. Thus, these ideas can meet the concept of Green IoT. Through our extensively theoretical and experimental analysis, the principle can effectively guide the design of ADCC scheme, and can reduce the delay, data drop ratio by 20.95% − 77.85% and 29.63% − 100% respectively, without affecting network lifetime, compared with previous scheme.

Small-Signal Models of Resonant Converter With Consideration of Different Duty-Cycle Control Schemes

Duty-cycle control is a widely used control method of resonant converters. In this article, the existing model of duty-cycle controlled resonant converters is found to have discrepancy compared with the simulation and experimental results. The reason behind is investigated, showing the phase change in the output voltage of the inverter bridge caused by the duty-cycle perturbation was ignored in the existing model. The phase change law is highly dependent on the duty-cycle scheme used, which is further determined by the forms of the carriers and the switching sequences of the resonant converters. With this consideration, improved models of both full-bridge and half-bridge resonant converters with different duty-cycle control schemes are rederived. It is revealed that different duty-cycle control schemes lead to different phase curves of the duty-cycle-to-output-voltage transfer functions, therefore care should be taken when selecting the appropriate duty-cycle control scheme. In the end, a series-series compensated wireless power transfer system is built to verify the validity of the proposed models.

Model Predictive Based Direct Torque Control for Induction Motor Drives by Sole-Evaluation of Two Parameter Independence Duty Ratios for Each Voltage Vector

Due to importance of duty cycle based model predictive torque control (MPTC), it has been accepted as an effective and common alternative control strategy for industry. Since its major drawback is great dependency on duty ratio parameter, the robustness and the complexity of control system has been respectively decreased and increased. A duty-ratio set considering limited members can be replaced with continuous and dependent parameters form duty cycle relationship. Hence, this paper proposes a new and applicable discrete duty cycle control strategy to reduce both the torque and flux ripples appeared in MPTC method. In the proposed method, after preselecting around half of all admissible voltage vectors based on the torque sign or speed variation and the stator flux position, two duty ratios have just been selected for the preselected active voltage vectors. These two duty ratios are achieved based on the equivalent voltage concept with independent motor parameter. Then, the model predictive control method is employed to select the optimum active voltage vector and its relevant duty ratio among the reduced feasible voltage vectors which reduces both the flux and torque ripples, especially in low speed ranges. The simulation results have confirmed the performance of the proposed method in order to reduce the torque and flux ripples, and the experimental results have accordingly validated its performance. Since the number of voltage vectors and duty ratios is significantly decreased, the execution time of the proposed method is further reduced, and virtually worked with a constant switching frequency for all speed ranges.

A Robust Simplified Dynamic Observer-Based Backstepping Control of Six-Phase Induction Motor for Marine Vessels Applications

This article presents a robust simplified dynamic observer-based backstepping control (RSDO-BSC) and direct torque control (DTC) synthesized with duty cycle control strategy of a six-phase induction motor (6PIM) for marine vessels applications. RSDO-BSC and DTC are employed to estimate the rotor speed, while the DTC is utilized to accomplish enhanced steady-state torque performance via accurate inputs applied to the switching table of the six-phase inverter. Furthermore, by using the duty cycle control approach, the loss components in the subspace are disregarded via the appropriate choice of virtual voltage vectors. Consequently, the 6PIM torque ripples and the current harmonics are significantly reduced. First, both the flux and the torque are decoupled using Lyapunov theory on a 6PIM two-axis mathematical model represented in the stationary reference frame. The 6PIM actual stator voltages are acquired from the dc-link voltage via the space vector pulsewidth modulated inverter. Subsequently, when the 6PIM is loaded under the rated speed, a rapid search approach is used to maximize the 6PIM efficiency. A 750-W 6PIM drive test setup employs a dSPACE 1104 for real-time implementation. The proposed RSDO-BSC performance is experimentally investigated at different speed commands, load disturbance, and low speed command with low load torque conditions.

Process variation tolerant wide-band fast PLL with reduced phase noise using adaptive duty cycle control strategy

ABSTRACT This paper presents the effects of manufacturing process variations on the phase-locked loop (PLL) performances like lock time, lock range and phase noise. At higher operating frequencies, due to process variations, there is a shift in the duty cycle of the divider output to phase-frequency detector, which leads to lock failure. To alleviate this problem an adaptive duty cycle control (ADCC) strategy is proposed and used in the frequency divider present in the feedback path of PLL. The proposed technique makes the PLL process variation tolerant and lock at higher frequencies where otherwise PLL was out of lock. It assists the PLL to lock faster and achieve low phase noise at all frequencies under nominal conditions. The operating temperature range is also enhanced to −50° to 50o C. Simulation studies in Cadence design environment on a 3.5 GHz PLL reveals the lock range improvement of 40% and phase noise improvement of 15%.

Model Predictive Flux Control of Semicontrolled Open-Winding PMSG With Circulating Current Elimination

In this article, an improved finite-control-set model predictive flux control (FCS-MPFC) is developed and implemented to eliminate the circulating current in the semicontrolled open-winding permanent magnet synchronous generator supplied by a single dc power. First, the references of torque, flux, and zero-sequence current are combined into the stator flux vector reference along with the implementation of maximum torque per ampere control to eliminate the weighting factors of the cost function in the conventional finite-control-set model predictive torque control. Then, to further improve the steady-state performance, a developed double-vector method based on the uncontrollable side voltage vector adjustment is conducted, which has the advantage of low computation burden. Moreover, a modified duty cycle control strategy is presented, in a manner where the reference value of flux is superseded with the measurement one to effectively calculate the duration of the optimal vector. Finally, experimental results verify the effectiveness and superiority of the proposed FCS-MPFC scheme.

A Dynamic Priority Factor Loop for Fast Voltage Equalization Applied to High Power Density DC–DC Converter System

A fast output voltage equalization control strategy applied to 10-kV/100-kW high power density photovoltaic dc–dc converter system is proposed in this paper. The converter modules in the system have two dynamic priority factor loops for fast response with an inconsistent voltage between modules and a soft start-up circuit to precharge output capacitance for solving inrush current problem in boost circuit. The proposed strategy can realize fast voltage equalization control under inconsistent leakage inductance and parasitic resistance parameters condition between modules compared to the traditional unified duty cycle control strategy. The fast equalization performance is verified by 10-kV/100-kW photovoltaic dc–dc converter system. The converter system adopts an isolated boost full-bridge topology and input parallel output series structure, which meets high conversion ratio and high-power density requirements.

A Novel Vector Control Strategy for a Six-Phase Induction Motor with Low Torque Ripples and Harmonic Currents

In this paper, a new vector control strategy is proposed to reduce torque ripples and harmonic currents represented in switching table-based direct torque control (ST-DTC) of a six-phase induction motor (6PIM). For this purpose, a new set of inputs is provided for the switching table (ST). These inputs are based on the decoupled current components in the synchronous reference frame. Indeed, using both field-oriented control (FOC) and direct torque control (DTC) concepts, precise inputs are applied to the ST in order to achieve better steady-state torque response. By applying the duty cycle control strategy, the loss subspace components are eliminated through a suitable selection of virtual voltage vectors. Each virtual voltage vector is based on a combination of a large and a medium vector to make the average volt-seconds in loss subspace near to zero. Therefore, the proposed strategy not only notably reduces the torque ripples, but also suppresses the low frequency current harmonics, simultaneously. Simulation and experimental results clarify the high performance of the proposed scheme.

Dynamic duty cycle control strategy for surface nuclear magnetic resonance sounding system.

The surface nuclear magnetic resonance (SNMR) technique exploits the NMR phenomenon to quantitatively determine the subsurface distribution of water. In the SNMR sounding system, deeper regions are probed by increasing the pulse moment (the product of the current amplitude and pulse duration). However, the amplitude of the current in the transmitter coil inevitably decays due to the energy loss in the storage capacitor. In practical application, the maximum amplitude of the current in one transmission process is recorded and used as the current amplitude. However, this approach results in errors in calculating the pulse moment and the sensitivity kernel function. In this paper, we build a simulation of the transmission process and the current decay phenomenon appears. From the simulation results, the current amplitude at the end of the pulse is 83% of the maximum. We present a dynamic duty cycle control strategy for a constant excitation current. We calculate the 1D sensitivity kernel function based on the two cases of constant and decaying excitation current, respectively. We observe that the maximum difference between them is greater than 200 nV/m. The inversion results based on a 1D aquifer model containing two aquifers show that the decaying excitation current results in aquifers deeper than the model and the water content of the second aquifer is 50% of the model. A comparative experiment between the decaying excitation current system and the constant excitation current system was conducted in a field experiment. Compared with traditional SNMR instruments, our new system can effectively avoid the phenomenon of excitation current decay in field experiments, and the new SNMR sounding system enables accurate inversion of aquifers.

A practical sleep coordination and management scheme with duty cycle control for energy sustainable IEEE 802.11s wireless mesh networks

We consider the energy sustainable operation of solar powered IEEE 802.11s wireless mesh networks. Our main contribution is the development of a simple and novel sleep scheduling scheme that is local and distributed and provides contiguous sleep intervals that can be used for putting both radio interface cards and the main-board into deep sleep mode. We show this provides substantial energy savings as main-board power consumption comprises a significant portion of total node power. Unlike many sleep coordination schemes developed for Wireless Sensor Networks, our approach is suitable for Wireless Mesh Networks having much larger traffic demand and non-tree-like routing pattern. In addition, we propose a local duty-cycle control scheme, which regulates node awake time and naturally limits the amount of elastic traffic that moves along energy limited nodes. This is coupled with an implicit admission control scheme, which limits the number of non-elastic flows admitted to the network. More importantly, our scheme does not modify the IEEE 802.11 MAC and does not require information of the traffic demand nor input energy pattern. We have evaluated the performance of our approach using NS3 simulations by considering its traffic volume, lifetime and numerous other parameters and have also compared it to both perfect scheduling and default IEEE 802.11s behavior. Our results are also backed by evaluating numerous randomly generated topologies. A detailed discussion of the effect of topological aspects of the network on its sustainability characteristics is also provided.

A Simple Duty Cycle Control Strategy to Reduce Torque Ripples and Improve Low-Speed Performance of a Three-Level Inverter Fed DTC IPMSM Drive

This paper presents a novel duty cycle-based direct torque control (DDTC) strategy for a three-level neutral point clamped inverter fed interior permanent magnet synchronous motor. DDTC methods proposed in the literature for three-level inverter fed DTC (3L-DTC) are complicated, parameter dependent, and pay little attention to inverter inherent switching constraints. In this paper, a simple yet robust duty ratio calculation method, which respects the inverter switching constraints, is proposed. Additionally, a novel switching strategy is adopted to minimize the effects of flux drooping phenomena seen in 3L-DTC drives during low-speed operations. The proposed 3L-DTC method is efficient in reducing both torque and flux ripples while operating at low switching frequencies. Therefore, it is suitable for medium-high power ac drives. Experimental results on a scaled down test rig and comparative analysis are provided to validate the effectiveness of the proposed strategy.

A Ring Diode–Capacitor Network for Current-Balancing Multiple LED Strings

A ring diode–capacitor network for current-balancing multiple LED strings is presented. The concept is based on utilizing the charge-balance property of capacitors to balance the currents of two adjacent LED strings in each switching cycle. Such current-balancing mechanism propagates over a ring network. The network has several merits, including 1) high current-balancing accuracy, 2) a simple structure, 3) modular and scalable, 4) current-balancing property being less dependent on the string voltages and the values of the capacitors, 5) inherent galvanic isolation between the driver and the LED strings, and 6) operation of the healthy LED(s) being unaffected by the failure LED(s). In addition, the capacitors in the network can be used as resonant tank components for the front-stage driver. An 80-W prototype for balancing the currents of ten LED strings has been built and evaluated. Each string has eight pieces of 1-W LED connected in series. The prototype is driven by a series-resonant converter. Results reveal that the string current variation is less than ±0.5%, irrespective to the variation of the string voltages and capacitor values. The total LED power can be dimmed to 10% of the rated output by a hybrid switching frequency and duty-cycle control scheme. The overall efficiency from the driver input to all LED strings is around 95% over the operating range. Modeling, design, and analysis of four possible configurations will be given.

Control of Wafer Temperature Using a Vortex Water-Wall Argon Arc

This paper describes a constant switching frequency variable duty cycle control strategy that adjusts the current in a vortex water-wall argon arc lamp to achieve wafer temperature tracking in response to a temperature ramp request. The control system includes a model for the following: 1) the outer loop temperature controller; 2) the inner loop current controller; 3) the wafer temperature; and 4) the irradiation produced by the arc lamp in response to arc current changes. The controller design is able to provide a well-behaved arc current and good temperature tracking performance that accommodates for no temperature feedback below 300 °C and a bumpless transfer once temperature feedback is available.

A Novel Control Scheme of DCM Boost PFC Converter

The discontinuous current mode boost power factor (PF) correction converter features a zero-current turn-on for the switch, no reverse recovery in diode, and constant frequency operations. However, when the duty cycle is constant in a line cycle, the input current contains rich third harmonic which has a phase difference of π with respect to the fundamental component. The harmonic results in not only a lower PF but also larger peak and RMS current values of the main power components, which lead to a higher conduction and switching turn-off loss. In this paper, a variable duty cycle control scheme is proposed to make the input current contain only third harmonic which is in phase with fundamental component, while remaining the same PF at a certain input voltage as that of constant duty cycle control. A method of fitting the duty cycle is further proposed for simplifying the circuit implementation. The efficiency is improved as the critical inductance increases and the peak and RMS current values consequently decrease. The proposed method also achieves an output voltage ripple or the output storage capacitance reduction. The experimental results from a prototype of 120 W are given to verify the effectiveness of the proposed method.

Modified Three-Phase Three-Level DC/DC Converter With Zero-Voltage-Switching Characteristic-Adopting Asymmetrical Duty Cycle Control

In the applications for high-power dc/dc conversion, the power devices usually suffer high voltage and current stress in traditional single-phase dc/dc topologies such as forward, half-bridge, and full-bridge converters, which limits the power level of converter to reach higher. As a superior alternative solution, a three-phase three-level (TPTL) dc/dc converter was investigated in this paper, which has the advantages of lower voltage and current stress on switches, as well as fewer power devices. Adopting a symmetrical control strategy, the input current and output current frequency can be increased by a factor of six compared to the switching frequency, resulting in a reduced filter requirement. However, all the switches are hard-switching, leading to a considerable switching loss. In this paper, an asymmetrical duty cycle control strategy was proposed to the TPTL dc/dc converter. The modified converter remains all the advantages of original control strategy; meanwhile, soft-switching can be achieved using the energy stored in output filter inductance and leakage inductances of transformers (or resonant inductances). The theoretical analysis was presented in details, along with the characteristics and soft-switching condition of the converter. Experimental results from 540 to 600 V input and 48 V/20 A output were presented to verify the theoretical analysis and the performance of the modified converter.

Duty cycle control with joint optimisation of delay and energy efficiency for capillary machine‐to‐machine networks in 5G communication system

AbstractA hybrid network architecture has been proposed for machine‐to‐machine (M2M) communications in the fifth generation wireless systems, where M2M gateways connect the capillary networks and cellular networks. In this paper, we develop novel energy efficient and end‐to‐end delay duty cycle control scheme for controllers at the gateway and the capillary networks coordinator. We first formulate a duty cycle control problem with joint‐optimisation of energy consumption and end‐to‐end delay. Then, a distributed duty cycle control scheme is proposed. The proposed scheme consists of two parts (i) a transmission policy, which decides the optimal number of packets to be transmitted between M2M devices, coordinators and gateways; and (ii) a duty cycle control for IEEE 802.15.4. We analytically derived the optimal duty cycle control and developed algorithms to compute the optimal duty cycle. It is to increase the feasibility of implementing the control on computation‐limited devices where a suboptimal low complexity rollout algorithm‐based duty cycle control (RADutyCon) is proposed. The simulation results show that RADutyCon achieves an exponential reduction of the computation complexity as compared with that of the optimal duty cycle control. The simulation results show that RADutyCon performs close to the optimal control, and it performs no worse than the heuristic base control. Copyright © 2014 John Wiley &amp; Sons, Ltd.