Typical Control Scheme Research Articles

Current-Sensorless Finite-Set Model Predictive Control for LC-Filtered Voltage Source Inverters

A typical finite-set model predictive control (FS-MPC) scheme for LC-filtered voltage source inverters (VSIs) requires measurements of capacitor voltage and inductor current as well as load current measurement or estimation, which increases the system complexity and cost. To reduce the number of sensors in typical FS-MPC, this paper proposes a new current-sensorless FS-MPC scheme for LC-filtered VSIs. First, based on the inner relationship of the predictive matrices, the predictive model is exactly simplified with the capacitor voltage and its current as the state variables, making it suitable for current-sensorless control. Then, to eliminate the current sensors for cost reduction and reliability enhancement, the dynamic model is reconstructed and an easily implemented capacitor current estimator is designed, which can achieve a comparable performance with typical FS-MPC scheme. Considering the inevitable control delay in digital implementation, the delay compensation is inherently obtained by using the proposed estimator. In addition, the proposed control scheme is flexible to various cost functions and can also reduce the computational cost. The feasibility of the presented control scheme under load variations and model mismatches are verified by the comparative simulation and experimental results with typical FS-MPC.

Multilevel Inverter (MLI)-Based Stand-Alone Photovoltaic System: Modeling, Analysis, and Control

In this paper, a vector control scheme for a multilevel inverter (MLI)-based single-stage, three-phase, photovoltaic (PV) stand-alone system is analyzed. The power circuit employs a PV module-driven MLI, connected to the load/grid through a three-phase transformer having open winding on the MLI side. The control scheme is developed to supply real power even with the variable load and solar irradiance levels. The proposed control can ensure real power stable across the dc-link capacitors of the inverters, as well as satisfy the transient performance indexes of the PV stand-alone system. The dc-link voltage level of the MLI is well maintained throughout the operation to achieve desired power for delivery point by the designed scheme. The control scheme performance is established to be adequate in the simulation environment under different operating conditions. The robust stability, sensitivity, and good disturbance rejection analysis are conducted in this topology, and to evaluate the robustness of the controllers. Real-time results have been validated on a laboratory MLI PV-stand-alone system. Furthermore, the proposed topology results in high efficiency compared to the typical control schemes with the current total harmonic distortion within the limits. The theoretical claims are established with the real-time results successfully.

An optimization-based control strategy for energy efficiency of discrete manufacturing systems

In order to reduce the global energy consumption and avoid highest power peaks during operation of manufacturing systems, an optimization-based controller for selective switching on/off of peripheral devices in a test bench that emulates the energy consumption of a periodic system is proposed. First, energy consumption models for the test-bench devices are obtained based on data and subspace identification methods. Next, a control strategy is designed based on both optimization and receding horizon approach, considering the energy consumption models, operating constraints, and the real processes performed by peripheral devices. Thus, a control policy based on dynamical models of peripheral devices is proposed to reduce the energy consumption of the manufacturing systems without sacrificing the productivity. Afterward, the proposed strategy is validated in the test bench and comparing to a typical rule-based control scheme commonly used for these manufacturing systems. Based on the obtained results, reductions near 7% could be achieved allowing improvements in energy efficiency via minimization of the energy costs related to nominal power purchased.

General Control Scheme for a Dual-Input Three-Level Inverter

This paper proposes a general control scheme for the dual-input three-level inverter, which comes from a neutral point clamped three-level inverter. It can be used for photovoltaic (PV) systems or battery storage systems with two dc sources. The dual-input three-level inverter can be connected with two PV arrays, which are able to realize maximum power point tracking independently. First, the dynamic model of the dual-input three-level inverter is established, which describes the relationship between the dual-input voltages and the duty cycle. After discussing the control theory of the dual-input voltages, a typical control scheme is proposed. The design of a control loop is introduced in details. Afterward, modulation and restriction of the proposed method are discussed. Finally, experiment on a 125 kW dual-input three-level PV inverter is implemented to verify the validity and feasibility of the proposed method.

Reduction of power grid fluctuations by communication between smart devices

The increase of the electric demand and the progressive integration of renewable energy sources threatens the stability of the power grid. To solve this issue, several methods have been proposed to control the demand side instead of increasing the spinning reserve in the supply. Here we focus on dynamic demand control (DDC), a method in which smart devices can autonomously delay its scheduled operation if the electric frequency is outside a suitable range. While typical control schemes can effectively reduce small and medium size frequency fluctuations, the probability of large demand peaks, and hence large frequency fluctuation, may increase due to the need of recovering pending tasks. Although these events are rare they can potentially trigger a failure of the system and therefore strategies to avoid them need to be addressed. In this work we introduce a method including communication among DDC devices belonging to a given group, such that they can coordinate opposite actions to keep the group demand more stable. We show that, with minimal information exchange, our method reduces the amount of pending tasks by a factor 10 while large frequency fluctuations are significantly reduced or even completely avoided.

A Review on Recent Advances and Future Trends of Transformerless Inverter Structures for Single-Phase Grid-Connected Photovoltaic Systems

°CThe research significance of various scientific aspects of photovoltaic (PV) systems has increased over the past decade. Grid-tied inverters the vital elements for the effective interface of Renewable Energy Resources (RER) and utility in the distributed generation system. Currently, Single-Phase Transformerless Grid-Connected Photovoltaic (SPTG-CPV) inverters (1–10 kW) are undergoing further developments, with new designs, and interest of the solar market. In comparison to the transformer (TR) Galvanic Isolation (GI)-based inverters, its advantageous features are lower cost, lighter weight, smaller volume, higher efficiency, and less complexity. In this paper, a review of SPTG-CPV inverters has been carried out. The basic operational principles of all SPTG-CPV inverters are presented in details for positive, negative, and zero cycles. A comprehensive analysis of each topology has been deliberated. A comparative assessment is also performed based on weaknesses, strengths, component ratings, efficiency, total harmonic distortion (THD), semiconductor device losses, and leakage current of various SPTG-CPV inverters schemes. Typical PV inverter structures and control schemes for grid connected three-phase system and single-phase systems are also discussed, described, and reviewed. Comparison of various industrial grids-connected PV inverters is also performed. Loss analysis is also performed for various topologies at 1 kW. Selection of appropriate topologies for their particular application is thoroughly presented. Then, discussion and forthcoming progress are emphasized. Lastly, the conclusions are presented. More than 100 research publications on the topic of SPTG-CPV inverter topologies, configurations, and control schematics along with the recent developments are thoroughly reviewed and classified for quick reference.

A bilateral control scheme for vehicle steer-by-wire system with road feel and steering controller design

Steer-by-wire (SBW) system replaces the mechanical linkages in a conventional steering system with electronic actuators. However, such a steering system has problems regarding how to harmonize angle and torque close loop control strategy whilst guaranteeing SBW system stability. Towards this problem, a bilateral control scheme is proposed for SBW system with steering and road feel feedback control. A new torque and angle feedback deviation type bilateral control scheme is designed based on the analysis of several typical bilateral control schemes. In this bilateral control scheme, it only needs to measure steering wheel angle, steering wheel torque, pinion angle and steering motor torque, whilst it does not need to estimate tire and road force, neither to deploy complicated and expensive sensors or devices. The Llewellyn stability criterion and wave variable control are used to analyze the influencing factors of the stability of the SBW system and to control the stability respectively. The transparency of the SBW system is analyzed based on the impedance theory. In order to improve vehicle handling, the road feel feedback torque is designed by using a compensation controller. The bilateral control scheme and compensation controllers are implemented and their performance is experimentally validated using test vehicle. Test results demonstrate the efficiency and effect of the proposed algorithm.

A Novel Interdependent Source-Channel Coding Technique for Enhanced Energy Efficiency in Communication over Wireless Sensor Networks

Reliable energy efficient information transmission is the primary design objective of a Wireless Sensor Network (WSN), considering its unique energy and resource constraints. Energy efficiency and bit error rate (BER) performance are the basic criteria to be taken into account while designing an optimal error correction scheme for WSNs. In this paper, a novel energy efficient error control scheme is proposed which minimizes the energy overheads of a typical error control scheme such as additional bits’ transmit energy and encoding/decoding energy, while achieving a better BER performance compared to the standard schemes. The redundant bits’ transmit energy is saved by incorporating compression and coding energy is minimized by employing simpler operations compared to other schemes. Further,the proposed scheme is validated in the context of mica2 motes. The BER performance and energy consumption of the presented scheme are studied and compared with standard error control schemes,such as, Hamming (7, 4) and RS (31, 29). Simulation results demonstrate the efficacy of the proposed methodology yielding a coding gain (CG) of 4.093 dB with a parameter selection of {30, 7, 2, 5}, in AWGN channel at BER of \(10^{-5}\), as compared to CG of 0.561 dB and 1.485 dB obtained using Hamming (7, 4) and RS (31, 29), respectively. Further, the standard codes above have a redundancy of 75% and 6.9% respectively while the proposed code with the above parameters achieves a compression of 23.81%. Quantification of energy consumption corresponding to each of the above schemes is also provided to prove the energy efficiency of the proposed technique.

Modeling and Maximum Power Point Tracking Control of Wind Generating Units Equipped with Permanent Magnet Synchronous Generators in Presence of Losses

This paper focuses on the modeling of wind turbines equipped with direct drive permanent magnet synchronous generators for fundamental frequency power system simulations. Specifically, a procedure accounting for the system active power losses to initialize the simulation starting from the load flow results is proposed. Moreover, some analytical assessments are detailed on typical control schemes for fully rated wind turbine generators, thereby highlighting how active power losses play a fundamental role in the effectiveness of the wind generator control algorithm. Finally, the paper proposes analytical criteria to design the structure and the parameters of the regulators of the wind generator control scheme. Simulations performed with Digsilent Power Factory validated the proposed procedure, highlighting the impact of active power losses on the characterization of the initial steady state and that the simplifying assumptions done in order to synthesize the controllers are consistent with the complete modeling performed by the aforementioned power system simulator.

A negotiation-based cooperative RBAC scheme

Owing to the application (APP) software for the mobile users are more and more increasing, there are various attacks or challenges appeared in accessing control of the cooperative multiple servers. However, the typical access control schemes are insufficient to deal with the kind of applications that allow accessing services by way of huge users or groups. Hence, we propose the cooperative RBAC (Role-based Access Control) scheme with negotiation-based hierarchical virtual role in this paper. It could manage not only one resource agent server, but also more than one multiple agent servers on the cooperation domain through negotiated virtual role or role set to access the collaboration agent servers. Furthermore, it provides a hierarchical virtual role structure allowing flexible negotiations among the multiple agent servers in this cooperation domain. Because of concentrating on easily designing the negotiation role approach with both extendable and flexible for RBAC model, it is a highly powerful solution using the innovative research and design of the hierarchical virtual role assignment for negotiation-based RBAC scheme.

Finite Control Set-Model Predictive Control of a Flying Capacitor Multilevel Chopper Using Petri Nets

This paper presents a control scheme based on the predictive control theory and Petri nets (PNs) formalism to control a flying capacitor multilevel converter. The proposed scheme takes advantage of the benefits offered by the finite control set-model predictive control (FCS-MPC) methodology and the versatility of PNs to regulate the capacitor voltages and output current, simultaneously. The inclusion of PNs allows us to simplify the control scheme. A first PN is used to select, from a subset of switching states, the switching state that accomplishes both control objectives. This approach reduces the computational burden if compared with a typical predictive control scheme. Furthermore, a PN-based prediction scheme is used to predict the capacitor voltages. This prediction scheme uses only measurements of output voltage and current, which reduces the number of required sensors. This approach allows us to implement the internal capacitor voltages control independently if a multileg configuration is needed. The scheme is experimentally validated in a five-level flying capacitor multilevel converter.

ROBUST CONTROL OF WIENER SYSTEMS: APPLICATION TO A pH NEUTRALIZATION PROCESS

Fil: Biagiola, Silvina Ines. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Instituto de Investigaciones en Ingenieria Electrica ; Argentina

Different Control Schemes Study on Landslide with Underground Crossing Pipeline

With the progressive proceeding of energy pipeline construction, long-distance petroleum and natural gas transmission pipelines were designed to pass through the mountain area of Midwest China, part of them have been threatened by severe landslide hazard. Therefore, the effective control scheme for the exiting pipelines across landslide area has been increasingly interested. A typical landslide in Western China area was taken as an example, from which the interaction model of landslide and pipeline was performed. On the base of the landslide characteristics analysis and numerical modeling, two kinds of typical control schemes, including anti-sliding piles and anchors supporting, were presented to carry out a comparative analysis and evaluation for landslide control. The results show that the scheme involving anti-sliding pile is the better scheme, whose cost and technical requirement are lower than that of anchors supporting scheme in the aspects of cost and the feasibility of construction. This study can provide a scientific basis for the optimal control scheme determination for the landslides with pipeline underground crossing in Western China.

Efficiency and equity of ramp control and capacity allocation mechanisms in a freeway corridor

This paper investigates the efficiency and equity of morning peak ramp control schemes in a freeway corridor with limited capacity. In terms of efficiency, both short-run and long-run optimal ramp control schemes are obtained by minimizing the total travel cost and maximizing the total social benefit along the corridor. It is found that for a short-run optimum with inelastic demand, the morning peak period is of the same duration for different on-ramp locations. But for a long-run optimum with elastic demand, the peak duration for various on-ramps increases with the local capacity elasticity of demand. In terms of equity, two measures are defined from a demand-based viewpoint and a space-based viewpoint. It is shown that the short-run optimal ramp control scheme is perfectly fair from a demand-based equity viewpoint. Consequently, two typical ramp control schemes—a perfect demand-based equity scheme and a perfect space-based equity scheme—are introduced and compared with the long-run optimal ramp control scheme in terms of efficiency and equity. Numerical simulations using survey data from China suggest that the perfect demand-based equity scheme attains an economic welfare level that is very close to the optimal one and the conflict between efficiency and equity diminishes as demand becomes less elastic.

Kinematics and Dynamics Modeling of a New 4-DOF Cable-Driven Parallel Manipulator

This paper addresses the kinematics and dynamics modeling of a 4-DOF cable-driven parallel manipulator with new architecture and a typical Computed Torque Method (CTM) controller is developed for dynamic model in SimMechanics. The novelty of kinematic architecture and the closed loop formulation is presented. The workspace model of mechanism’s dynamic is obtained in an efficient and compact form by means of natural orthogonal complement (NOC) method which leads to the elimination of the nonworking kinematic-constraint wrenches and also to the derivation of the minimum number of equations. To verify the dynamic model and analyze the dynamical properties of novel 4-DOF cable-driven parallel manipulator, a typical CTM control scheme in joint-space is designed for dynamic model in SimMechanics.

The novel stable control scheme of the light source power in the closed-loop fiber optic gyroscope

The light source power stability of the Fiber-Optic Gyroscope (FOG) affects directly the scale factor and bias stability of FOG. The typical control scheme of the light source power employs an additional photodetector to detect the output power of the light source. When the fiber loss of FOG varied due to the temperature change, the light power in the additional photodetector did not indicate this change, which decreased the control effect. The spike pulse overlapping on the gyro signal denotes potentially the change of the light power and fiber loss. In the novel scheme, the spike pulse is extracted from the gyro signal, and is transformed into the square wave by the differential circuit. According to the change of the square wave amplitude, FOG adjusts the bias current of the light source to keep the stable light power in the signal photodetector. It is a simple and low-cost scheme without an additional photodetector.

Efficiency and Equity of Ramp Control and Capacity Allocation Mechanisms in a Freeway Corridor

This paper investigates the efficiency and equity of morning peak ramp control schemes in a freeway corridor with limited capacity. In terms of efficiency, both short-run and long-run optimal ramp control schemes are obtained by minimizing the total travel cost and maximizing the total social benefit along the corridor. It is found that for a short-run optimum with inelastic demand, the morning peak period is of the same duration for different on-ramp locations. But for a long-run optimum with elastic demand, the peak duration for various on-ramps increases with the local capacity elasticity of demand. In terms of equity, two measures are defined from a demand-based viewpoint and a space-based viewpoint. It is shown that the short-run optimal ramp control scheme is perfectly fair from a demand-based equity viewpoint. Consequently, two typical ramp control schemes—a perfect demand-based equity scheme and a perfect space-based equity scheme—are introduced and compared with the long-run optimal ramp control scheme in terms of efficiency and equity. It is shown that the long-run optimal ramp control scheme without an equity constraint is more unfair than the perfect demand-based equity scheme from a space-based equity viewpoint. Numerical simulations using survey data from China suggest that the perfect demand-based equity scheme attains an economic welfare level that is very close to the optimal one.

Novel DSA Scheme that Uses Traffic Characteristics to Enhance Throughput Performance of Wide Area Ubiquitous Wireless Networks

Wide area ubiquitous wireless networks, which consist of access points (APs) connected to the fixed network and a great many wireless terminals (WTs), can offer a wide range of applications everywhere. In order to enhance network performance, we need to collect different kinds of data from as many WTs as possible; each AP must be capable of accommodating more than 103 WTs. This requirement can be achieved by employing DSA, a typical centralized media access control scheme, since it has high resource utilization efficiency. In this paper, we propose a novel DSA scheme that employs three new techniques to enhance throughput performance; (1) considering that most terminals tend to send data periodically, it employs both polling-based schemes, i.e. request-polling and data-polling, and a random access scheme. (2) In order to enhance bandwidth utilization effectiveness by polling, the polling timing is decided according to the data generation timing. (3) The AP decides the polled data size according to the latest distribution of data size and polls the WT for the data directly. If the data-polling size can not be determined with confidence, the AP uses request-polling instead of data-polling. Simulations verify that the proposed scheme offers better transmission performance than the existing schemes.

ROBUSTNESS ANALYSIS OF WIENER SYSTEMS

As reported in the literature, Wiener models have emerge as an appealing proposal for nonlinear processes representation due to their simplicity and the property of being valid over a larger operating region than a LTI model.In this article, we propose a methodology to analyzed the robustness of a typical control scheme. To perform this analysis, we use a parametric description for the Wiener system. This model allows to describe the uncertainty as a set of parameters for the linear and the nonlinear blocks. Then, the linear block uncertainty is considered as a parameter-affine-dependent model and the nonlinear block uncertainty is studied as a conic-sector. The robustness analysis is then performed using μ-theory.

Thermal Control Schemes for a Micro-Satellite with All-Active and Selectively Active Solar String Designs

In this study, a finite element model of a micro-satellite named X-SAT was developed to perform heat transfer analysis and design a passive thermal control scheme in the form of thermal coatings, film, and paints. To start with, the modeling philosophy and computational methodology were introduced along with the suitable assumptions made. A typical thermal control scheme was proposed and implemented using SINDA/G-NEVADA software. The sensitivity of the results to the software settings was then assessed. It was observed that the limits on the ray counts for Monte Carlo simulation in RENO and VEGAS routines play a vital role in deciding reliability of the results, especially the temperature gradients within solar panels. Subsequently, two types of solar panel designs, one with all-active solar strings and other with selectively active solar strings, were examined. When the panels with all-active type of solar cell strings were adopted, heat dissipation through shunt regulators posed a challenge for thermal control. Various scenarios for the second case with high-efficiency, selectively operable solar strings were also simulated. For both case studies, a sun-tracking mode and an overhead pass-imaging operation were considered for the worst hot and cold cases. The results showed that the switchable string design was preferable in terms of operational flexibility and thermal control.