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Records with Subject: Process Control
Showing records 1 to 25 of 208. [First] Page: 1 2 3 4 5 Last
Improving Performance for Full-Bridge Inverter of Wind Energy Conversion System Using a Fast and Efficient Control Technique
En-Chih Chang
January 23, 2020 (v1)
Keywords: chatter, finite-time convergent SMGL (sliding-mode guidance law), Fourier nonlinear grey Bernoulli model (FNGBM), full-bridge inverter, singularity-free
This paper proposes a fast and efficient control technique with application to a full-bridge inverter of a wind energy conversion system that is capable of yielding better performance in transience and steady state. The presented control technique is made up of a finite-time convergent SMGL (sliding-mode guidance law) and a Fourier nonlinear grey Bernoulli model (FNGBM). The finite-time convergent SMGL provides a faster convergence rate of system states, as well as a singularity-free solution. However, in case the overestimation/underestimation of the uncertain system boundary occurs, the chatter/steady-state error may exist in finite-time convergent SMGL and then causes serious harmonic distortion at the full-bridge inverter output. An efficient calculational FNGBM is integrated into the finite-time convergent SMGL, thus overcoming chatter/steady-state error problems if the estimated value of the uncertain system boundary cannot be satisfied. Simulation results indicate that the propo... [more]
Improvement of Refrigeration Efficiency by Combining Reinforcement Learning with a Coarse Model
Dapeng Zhang, Zhiwei Gao
January 19, 2020 (v1)
Keywords: coarse model, data-driven methods, refrigeration, reinforcement learning
It is paramount to improve operational conversion efficiency in air-conditioning refrigeration. It is noticed that control efficiency for model-based methods highly relies on the accuracy of the mechanism model, and data-driven methods would face challenges using the limited collected data to identify the information beyond. In this study, a hybrid novel approach is presented, which is to integrate a data-driven method with a coarse model. Specifically, reinforcement learning is used to exploit/explore the conversion efficiency of the refrigeration, and a coarse model is utilized to evaluate the reward, by which the requirement of the model accuracy is reduced and the model information is better used. The proposed approach is implemented based on a hierarchical control strategy which is divided into a process level and a loop level. The simulation of a test bed shows the proposed approach can achieve better conversion efficiency of refrigeration than the conventional methods.
Multiple-Input Single-Output Control for Extending the Steady-State Operating Range—Use of Controllers with Different Setpoints
Adriana Reyes-Lúa, Sigurd Skogestad
January 19, 2020 (v1)
Keywords: control structure, optimal operation, parallel control, PID, split range control, valve position control
This paper deals with a case when multiple inputs are needed to cover the steady-state operating range. The most common implementation is to use split range control with a single controller. However, this approach has some limitations. In this paper, we use multiple controllers with different setpoints and demonstrate that this structure can be optimal in some cases when the cost of the input can be traded off against the penalty of deviating from the desired setpoint. We describe a procedure to find the optimal setpoint deviations. We illustrate our procedure in a case in which three inputs (cooling and two sources of heating) are used to control the temperature of a room with a PID-based control structure and without the need of online optimization.
Optimal Tuning of Model Predictive Controller Weights Using Genetic Algorithm with Interactive Decision Tree for Industrial Cement Kiln Process
Valarmathi Ramasamy, Rakesh Kumar Sidharthan, Ramkumar Kannan, Guruprasath Muralidharan
January 19, 2020 (v1)
Keywords: cement kiln, Genetic Algorithm, interactive decision tree, model predictive controller, weight tuning
Energy intense nature of cement kiln demands optimal operation to minimize the energy requirement. Optimal control of cement kiln is achieved by proper tuning of the model predictive controller (MPC), which is addressed in this work. Genetic algorithm (GA) is used to determine the MPC weights that minimize the overall energy utilization with reduced tracking error. Single objective function has been formulated using importance weighted performance metrics like energy utilization and integral absolute error in tracking the desired response. Importance weights are determined in specific to the control scenarios using an interactive decision tree (IDT). It interacts with the operator to detect the weaker metrics and raises the importance level for further improvement. The algorithm terminates after attending all the metrics with the consent from the operator. Five control scenarios that predominantly occur in industrial cement kiln have been considered in this study. It includes tracking,... [more]
Design and Implementation of the Off-Line Robust Model Predictive Control for Solid Oxide Fuel Cells
Narissara Chatrattanawet, Soorathep Kheawhom, Yong-Song Chen, Amornchai Arpornwichanop
January 7, 2020 (v1)
Keywords: control synthesis, off-line calculation, robust model predictive control, solid oxide fuel cell
An off-line robust linear model predictive control (MPC) using an ellipsoidal invariant set is synthesized based on an uncertain polytopic approach and then implemented to control the temperature and fuel in a direct internal reforming solid oxide fuel cell (SOFC). The state feedback control is derived by minimizing an upper bound on the worst-case performance cost. The simulation results indicate that the synthesized robust MPC algorithm can control and guarantee the stability of the SOFC; although there are uncertainties in some model parameters, it can keep both the temperature and fuel at their setpoints.
Design, Simulation, and Experiment of an LTCC-Based Xenon Micro Flow Control Device for an Electric Propulsion System
Chang-Bin Guan, Yan Shen, Zhao-Pu Yao, Zhao-Li Wang, Mei-Jie Zhang, Ke Nan, Huan-Huan Hui
December 13, 2019 (v1)
Keywords: electric propulsion system, flow characteristic, low-temperature co-fired ceramic (LTCC), xenon feeding system, xenon micro flow control device (XMFCD)
A xenon micro flow control device (XMFCD) is the key component of a xenon feeding system, which controls the required micro flow xenon (µg/s−mg/s) to electric thrusters. Traditional XMFCDs usually have large volume and weight in order to achieve ultra-high fluid resistance and have a long producing cycle and high processing cost. This paper proposes a miniaturized, easy-processing, and inexpensive XMFCD, which is fabricated by low-temperature co-fired ceramic (LTCC) technology. The design of the proposed XMFCD based on complex three-dimensional (3D) microfluidic channels is described, and its fabrication process based on LTCC is illustrated. The microfluidic channels of the fabricated single (9 mm diameter and 1.4 mm thickness) and dual (9 mm diameter and 2.4 mm thickness) XMFCDs were both checked by X-ray, which proved the LTCC method’s feasibility. A mathematical model of flow characteristics is established with the help of finite element analysis, and the model is validated by the e... [more]
Performance Improvement of a Grid-Tied Neutral-Point-Clamped 3-φ Transformerless Inverter Using Model Predictive Control
Hani Albalawi, Sherif A. Zaid
December 13, 2019 (v1)
Keywords: 3-φ transformerless inverter, boost converter, maximum power point tracking, Model Predictive Control, NPC, PV
Grid-connected photovoltaic (PV) systems are now a common part of the modern power network. A recent development in the topology of these systems is the use of transformerless inverters. Although they are compact, cheap, and efficient, transformerless inverters suffer from chronic leakage current. Various researches have been directed toward evolving their performance and diminishing leakage current. This paper introduces the application of a model predictive control (MPC) algorithm to govern and improve the performance of a grid-tied neutral-point-clamped (NPC) 3-φ transformerless inverter powered by a PV panel. The transformerless inverter was linked to the grid via an inductor/capacitor (LC) filter. The filter elements, as well as the internal impedance of the grid, were considered in the system model. The discrete model of the proposed system was determined, and the algorithm of the MPC controller was established. Matlab’s simulations for the proposed system, controlled by the MPC... [more]
Salp Swarm Optimization Algorithm-Based Controller for Dynamic Response and Power Quality Enhancement of an Islanded Microgrid
Touqeer Ahmed Jumani, Mohd. Wazir Mustafa, Madihah Md. Rasid, Waqas Anjum, Sara Ayub
December 13, 2019 (v1)
Keywords: dynamic response enhancement, microgrid, Optimization, power quality, salp swarm optimization algorithm, voltage and frequency regulation
The islanded mode of the microgrid (MG) operation faces more power quality challenges as compared to grid-tied mode. Unlike the grid-tied MG operation, where the voltage magnitude and frequency of the power system are regulated by the utility grid, islanded mode does not share any connection with the utility grid. Hence, a proper control architecture of islanded MG is essential to control the voltage and frequency, including the power quality and optimal transient response during different operating conditions. Therefore, this study proposes an intelligent and robust controller for islanded MG, which can accomplish the above-mentioned tasks with the optimal transient response and power quality. The proposed controller utilizes the droop control in addition to the back to back proportional plus integral (PI) regulator-based voltage and current controllers in order to accomplish the mentioned control objectives efficiently. Furthermore, the intelligence of the one of the most modern soft... [more]
Extremum Seeking Control for Discrete-Time with Quantized and Saturated Actuators
Martin Guay, Daniel J. Burns
December 13, 2019 (v1)
Keywords: constrained systems, extremum-seeking control, real-time optimization
This paper proposes an extremum-seeking controller (ESC) design for a class of discrete-time nonlinear control systems subject to input constraints or quantized inputs. The proposed method implements a proportional-integral ESC design along with a discrete-time anti-windup mechanism. The anti-windup enforces input saturation while preserving the input dither signal. The technique incorporates a mechanism for adjusting the amplitude of the extremum seeking control dither signal. This mechanism ensures that any violation of constraints due to the dither signal is removed while maintaining the probing signal active. An amplitude update routine is also proposed. The amplitude update is coupled with a saturation bias estimation algorithm that correctly accounts for the inherent bias associated with systems operated at or near saturation conditions. The amplitude update is designed to remove the dither signal when the system approaches the optimum. It also ensures that a lower bound of the a... [more]
A Review of Convex Approaches for Control, Observation and Safety of Linear Parameter Varying and Takagi-Sugeno Systems
Francisco-Ronay López-Estrada, Damiano Rotondo, Guillermo Valencia-Palomo
December 13, 2019 (v1)
Keywords: convex systems, fault diagnosis, fault tolerant control (FTC), linear matrix inequalities (LMIs), linear parameter varying (LPV) systems, Takagi-Sugeno systems
This paper provides a review about the concept of convex systems based on Takagi-Sugeno, linear parameter varying (LPV) and quasi-LPV modeling. These paradigms are capable of hiding the nonlinearities by means of an equivalent description which uses a set of linear models interpolated by appropriately defined weighing functions. Convex systems have become very popular since they allow applying extended linear techniques based on linear matrix inequalities (LMIs) to complex nonlinear systems. This survey aims at providing the reader with a significant overview of the existing LMI-based techniques for convex systems in the fields of control, observation and safety. Firstly, a detailed review of stability, feedback, tracking and model predictive control (MPC) convex controllers is considered. Secondly, the problem of state estimation is addressed through the design of proportional, proportional-integral, unknown input and descriptor observers. Finally, safety of convex systems is discusse... [more]
Adaptive Control of Biomass Specific Growth Rate in Fed-Batch Biotechnological Processes. A Comparative Study
Vytautas Galvanauskas, Rimvydas Simutis, Vygandas Vaitkus
December 13, 2019 (v1)
Keywords: adaptive control, biotechnological processes, fed-batch process, gain scheduling technique, model-free adaptive control, specific growth rate control
This article presents a comparative study on the development and application of two distinct adaptive control algorithms for biomass specific growth rate control in fed-batch biotechnological processes. A typical fed-batch process using Escherichia coli for recombinant protein production was selected for this research. Numerical simulation results show that both developed controllers, an adaptive PI controller based on the gain scheduling technique and a model-free adaptive controller based on the artificial neural network, delivered a comparable control performance and are suitable for application when using the substrate limitation approach and substrate feeding rate manipulation. The controller performance was tested within the realistic ranges of the feedback signal sampling intervals and measurement noise intensities. Considering the efforts for controller design and tuning, including development of the adaptation/learning algorithms, the model-free adaptive control algorithm prov... [more]
Research on the Vertical Vibration Characteristics of Hydraulic Screw Down System of Rolling Mill under Nonlinear Friction
Yongshun Zhang, Wanlu Jiang, Yong Zhu, Zhenbao Li
December 13, 2019 (v1)
Keywords: flow control, friction-induced vibration, hydraulic screw down system, LuGre model, PID controller, rolling mill, vertical vibration
The rolling mill with hydraulic system is widely used in the production of strip steel. For the problem of vertical vibration of the rolling mill, the effects of different equivalent damping coefficient, leakage coefficient, and proportional coefficient of the controller on the hydraulic screw down system of the rolling mill are studied, respectively. First, a vertical vibration model of a hydraulic screw down system was established, considering the nonlinear friction and parameter uncertainty of the press cylinder. Second, the correlation between different equivalent damping coefficient, internal leakage coefficient, proportional coefficient, vertical vibration was analyzed. The simulation results show that, in the closed-loop state, when Proportional-Integral-Derivative (PID) controller parameters are fixed, due to the change of the equivalent damping coefficient and internal leakage coefficient, the system will have parameter uncertainty, which may lead to the failure of the PID con... [more]
A PSO-Based Recurrent Closed-Loop Optimization Method for Multiple Controller Single-Output Thermal Engineering Systems
Xingjian Liu, Lei Pan
December 13, 2019 (v1)
Keywords: identification, Optimization, PID, PSO, thermal engineering process
For solving the problems of closed-loop optimization on controller parameters of multiple-controller single-output thermal engineering system, this paper proposes a recurrent optimization method that is based on the particle swarm computing and closed-loop simulation (PSO-RCO). It consists of a set of closed-loop identification, simulation, and optimization functions that are organized in a recurrent working flow. The working flow makes one controller tuned at a time whilst others keep their values. It ends after several rounds of overall optimizations. Such a recurrently alternative tuning can greatly speed up the convergence of controller parameters to reasonable values. Verifications on practical data from a superheated steam temperature control system show that the optimized control system performance is greatly improved by reasonable controller parameters and practicable control action. With the advantage of not interfering system operation and the potential supporting on big data... [more]
Control Applied to a Reciprocating Internal Combustion Engine Test Bench under Transient Operation: Impact on Engine Performance and Pollutant Emissions
Ismael Payo, Luis Sánchez, Enrique Caño, Octavio Armas
December 10, 2019 (v1)
Keywords: diesel engine, dynamics, dynamometer braking system, methodology, PID control, test stand
This work presents a methodology to adjust the electronic control system of a reciprocating internal combustion engine test bench and the effect of the control parameters on emissions produced by the engine under two extreme situations: unadjusted and adjusted, both under transient operation. The aim is to provide a tuning guide to those in charge of this equipment not needed to be experts in control engineering. The proposed methodology covers from experimental plant modelling to control parameters determination and experimental validation. The methodology proposed includes the following steps: (i) Understanding of test bench and mathematical modeling; (ii) Model parameters identification; (iii) Control law proposal and tuning from simulation and (iv) Experimental validation. The work has been completed by presenting a comparative experimental study about the effect of the test bench control parameters on engine performance profiles (engine speed, engine torque and relative fuel air r... [more]
Critical Speed Control for a Fixed Blade Variable Speed Wind Turbine
Morgan Rossander, Anders Goude, Sandra Eriksson
December 10, 2019 (v1)
Keywords: control, critical speed, eigenfrequencies, natural frequencies, optimal torque, speed exclusion zone, variable speed, vertical axis wind turbine
A critical speed controller for avoiding a certain rotational speed is presented. The controller is useful for variable speed wind turbines with a natural frequency in the operating range. The controller has been simulated, implemented and tested on an open site 12 kW vertical axis wind turbine prototype. The controller is based on an adaptation of the optimum torque control. Two lookup tables and a simple state machine provide the control logic of the controller. The controller requires low computational resources, and no wind speed measurement is needed. The results suggest that the controller is a feasible method for critical speed control. The skipping behavior can be adjusted using only two parameters. While tested on a vertical axis wind turbine, it may be used on any variable speed turbine with the control of generator power.
A Polar Fuzzy Control Scheme for Hybrid Power System Using Vehicle-To-Grid Technique
Mohammed Elsayed Lotfy, Tomonobu Senjyu, Mohammed Abdel-Fattah Farahat, Amal Farouq Abdel-Gawad, Hidehito Matayoshi
December 10, 2019 (v1)
Keywords: frequency control, hybrid power system, minimal-order observer, polar fuzzy, supply balance, V2G
A novel polar fuzzy (PF) control approach for a hybrid power system is proposed in this research. The proposed control scheme remedies the issues of system frequency and the continuity of demand supply caused by renewable sources’ uncertainties. The hybrid power system consists of a wind turbine generator (WTG), solar photovoltaics (PV), a solar thermal power generator (STPG), a diesel engine generator (DEG), an aqua-electrolyzer (AE), an ultra-capacitor (UC), a fuel-cell (FC), and a flywheel (FW). Furthermore, due to the high cost of the battery energy storage system (BESS), a new idea of vehicle-to-grid (V2G) control is applied to use the battery of the electric vehicle (EV) as equivalent to large-scale energy storage units instead of small batteries to improve the frequency stability of the system. In addition, EV customers’ convenience is taken into account. A minimal-order observer is used to estimate the supply error. Then, the area control error (ACE) signal is calculated in ter... [more]
Microstructure Control of Tubular Micro-Channelled Supports Fabricated by the Phase Inversion Casting Method
Yuliang Liu, Arash Rahimalimamaghani, Martin van Sint Annaland, Fausto Gallucci
December 10, 2019 (v1)
Keywords: ceramic membrane, CGO-MgO support, channel length, phase inversion casting, shrinkage behaviour, tubular micro-channelled support
Thin-film membrane layers coated onto porous supports is widely considered as an efficient way to obtain high-performance oxygen transport membranes with both good permeability and high mechanical strength. However, conventional preparation methods of membrane supports usually result in highly tortuous channels with high mass transfer resistance. Tubular porous MgO and MgO/CGO supports were fabricated with a simple phase inversion casting method. Long finger-like channels were obtained inside the dual-phase supports by adjusting the ceramic loading, polymer concentration and particle surface area, as well as by introducing ethanol inside the casting slurries. Slurries that exhibit lower viscosity in the zero-shear viscosity region resulted in more pronounced channel growth. These supports were used to produce thin supported CGO membranes for possible application in O2 separation. Similar shrinkage speeds for the different layers during the sintering process are crucial for obtaining de... [more]
Five Megawatt Wind Turbine Power Output Improvements by Passive Flow Control Devices
Unai Fernandez-Gamiz, Ekaitz Zulueta, Ana Boyano, Igor Ansoategui, Irantzu Uriarte
December 10, 2019 (v1)
Keywords: blade element momentum (BEM) model, flow control, gurney flaps (GFs), vortex generators (VGs), wind turbine power
The effects of two types of flow control devices, vortex generators (VGs) and Gurney flaps (GFs), on the power output performance of a multi-megawatt horizontal axis wind turbine is presented. To that end, an improved blade element momentum (BEM)-based solver has been developed and BEM-based computations have been carried out on the National Renewable Energy Laboratory (NREL) 5 MW baseline wind turbine. The results obtained from the clean wind turbine are compared with the ones obtained from the wind turbine equipped with the flow control devices. A significant increase in the average wind turbine power output has been found for all of the flow control device configurations and for the wind speed realizations studied in the present work. Furthermore, a best configuration case is proposed which has the largest increase of the average power output. In that case, increments on the average power output of 10.4% and 3.5% have been found at two different wind speed realizations. The thrust f... [more]
A New Backward Euler Stabilized Optimum Controller for NPC Back-to-Back Five Level Converters
Miguel Chaves, José Fernando Silva, Sónia Ferreira Pinto, Elmano Margato, João Santana
December 10, 2019 (v1)
Keywords: back-to-back converters, backward Euler based control, capacitors voltage balancing, multilevel converters
This paper presents a backward Euler stabilized-based control strategy applied to a neutral point clamped (NPC) back-to-back connected five level converters. A generalized method is used to obtain the back-to-back NPC converter system model. The backward Euler stabilized-based control strategy uses one set of calculations to compute the optimum voltage vector needed to reach the references and to balance the voltage of the DC-bus capacitors. The output voltage vector is selected using a modified cost functional that includes variable tracking errors in the functional weights, whereas in classic approaches, the weights are considered constant. The proposed modified cost functional enables AC current tracking and DC-bus voltage balancing in a wide range of operating conditions. The paper main contributions are: (i) a backward Euler stabilized-based control strategy applied to a double, back-to-back connected, five level NPC converter; (ii) the use of cost functional weight varying as a f... [more]
Frequency-Adaptive Modified Comb-Filter-Based Phase-Locked Loop for a Doubly-Fed Adjustable-Speed Pumped-Storage Hydropower Plant under Distorted Grid Conditions
Wei Luo, Jianguo Jiang, He Liu
December 10, 2019 (v1)
Keywords: adjustable speed pumped storage hydropower plant, distorted grid conditions, FAMCF-PLL, versa module eurocard (VME) bus
The control system of a doubly-fed adjustable-speed pumped-storage hydropower plant needs phase-locked loops (PLLs) to obtain the phase angle of grid voltage. The main drawback of a comb-filter-based phase-locked loop (CF-PLL) is the slow dynamic response. This paper presents a modified comb-filter-based phase-locked loop (MCF-PLL) by improving the pole-zero pattern of the comb filter, and gives the parameters’ setting method of the controller, based on the discrete model of MCF-PLL. In order to improve the disturbance resistibility of MCF-PLL when the power grid’s frequency changes, this paper proposes a frequency-adaptive modified, comb-filter-based, phase-locked loop (FAMCF-PLL) and its digital implementation scheme. Experimental results show that FAMCF-PLL has good steady-state and dynamic performance under distorted grid conditions. Furthermore, FAMCF-PLL can determine the phase angle of the grid voltage, which is locked when it is applied to a doubly-fed adjustable-speed pumped-s... [more]
High-Gain Disturbance Observer-Based Robust Load Frequency Control of Power Systems with Multiple Areas
Ismi Rosyiana Fitri, Jung-Su Kim, Hwachang Song
December 10, 2019 (v1)
Keywords: area control error (ACE), high-gain disturbance observer (HDOB) controller, load frequency control (LFC)
This paper proposes a high-gain disturbance observer (HDOB)-based controller for load frequency control (LFC) of power systems with multiple areas. The main goal of LFC problem is to maintain the frequency to its nominal value. The objective of this paper is to reject frequency variations due to abrupt load changes and diverse uncertainties (e.g., inertia and damping parameters, and interconnection topology, etc.) by employing the HDOB for the LFC. The simulation results demonstrate the effectiveness of the proposed HDOB-based LFC by showing that it successfully rejects frequency variations owing to load changes and frequency variations occurring in various locations in interconnected power systems. Besides, it is shown that the proposed LFC can eliminate frequency deviations although there are delays in transmission among the power systems with multiple areas.
Control Strategy of Single-Phase Three Level Neutral Point Clamped Cascaded Rectifier
Xiaoqiong He, Xiaolan Lin, Xu Peng, Pengcheng Han, Zeliang Shu, Shibin Gao
December 10, 2019 (v1)
Keywords: 3-level neutral point clamped cascaded rectifier (3LNPC-CR), capacitor voltage balancing, mutual-module voltage balancing, phase shift carrier space vector pulse width modulation (PSC-SVPWM)
Single-phase 3-level neutral point clamped cascaded rectifier (3LNPC-CR) has been successfully made its way into traction drive system as a high-voltage traction converter. In this passage, the control issue of the 3LNPC-CR is considered. A transient current control strategy, combined with proportional integral (PI) controllers, is adopted to achieve unity power factor, satisfactory sinusoidal grid current, regulated overall dc voltage, and even efficient voltage balance between each module. Besides, with regard to the instinct voltage fluctuation problem among dc-link capacitors in one 3-level neutral point clamped (3LNPC) rectifier module, a phase shift carrier space vector pulse width modulation (PSC-SVPWM) worked along with a reasonable redundancy selection scheme is addressed. In addition, two auxiliary balancing circuits for a single-phase 3LNPC rectifier is proposed. The voltage balancing capacity of these internal-module balancing schemes are analyzed and compared. Finally, the... [more]
A Short-Current Control Method for Constant Frequency Current-Fed Wireless Power Transfer Systems
Yanling Li, Qichang Duan, Weiyi Li
December 10, 2019 (v1)
Keywords: current-fed, frequency drift, inductance damping, short current, wireless power transfer
Frequency drift is a serious problem in Current-Fed Wireless Power Transfer (WPT) systems. When the operating frequency is drifting from the inherent Zero Voltage Switching (ZVS) frequency of resonant network, large short currents will appear and damage the switches. In this paper, an inductance-dampening method is proposed to inhibit short currents and achieve constant-frequency operation. By adding a small auxiliary series inductance in the primary resonant network, short currents are greatly attenuated to a safe level. The operation principle and steady-state analysis of the system are provided. An overlapping time self-regulating circuit is designed to guarantee ZVS running. The range of auxiliary inductances is discussed and its critical value is calculated exactly. The design methodology is described and a design example is presented. Finally, a prototype is built and the experimental results verify the proposed method.
H∞ Repetitive Control Based on Active Damping with Reduced Computation Delay for LCL-Type Grid-Connected Inverters
Wei Jin, Yongli Li, Guangyu Sun, Lizhi Bu
December 10, 2019 (v1)
Keywords: active damping, delay effects, grid-connected inverter, H∞ theory, inductor-capacitor-inductor (LCL) filter, power quality, repetitive control
In the paper, the H∞ repetitive current control scheme based on active damping along with the design method is proposed for three-phase grid-connected inverters with inductor-capacitor-inductor (LCL) filters. The control scheme aims to reduce the harmonic distortion of the output currents and achieve better efficiency. The design method introduces capacitor-current-feedback active damping into the H∞ controller design process by proposing an equivalent controlled plant. Additionally, based on the discrete model of the controlled plant with variable computation delay, the algebraic expression of the stable region for the feedback coefficient and the computation delay is obtained to avoid system instability caused by the digital control delay. Finally, the stability criterion is proposed to evaluate the stability of the discrete control system with the H∞ repetitive current control scheme. The theoretical analysis and experimental results prove that the control scheme presented in this p... [more]
Predictive Direct Flux Control—A New Control Method of Voltage Source Inverters in Distributed Generation Applications
Jiefeng Hu
December 10, 2019 (v1)
Keywords: inverter flux, predictive control, voltage source inverter (VSI)
Voltage source inverters (VSIs) have been widely utilized in electric drives and distributed generations (DGs), where electromagnetic torque, currents and voltages are usually the control objectives. The inverter flux, defined as the integral of the inverter voltage, however, is seldom studied. Although a conventional flux control approach has been developed, it presents major drawbacks of large flux ripples, leading to distorted inverter output currents and large power ripples. This paper proposes a new control strategy of VSIs by controlling the inverter flux. To improve the system’s steady-state and transient performance, a predictive control scheme is adopted. The flux amplitude and flux angle can be well regulated by choosing the optimum inverter control action according to formulated selection criteria. Hence, the inverter flux can be controlled to have a specified magnitude and a specified position relative to the grid flux with less ripples. This results in a satisfactory line... [more]
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