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Grid-forming control is a promising solution for renewable power integration. This work presents a variable pairing scheme for the voltage controller of V/f controlled modular multilevel converter in an islanded network with a synchronous machine, which is a special type of grid-forming control. Based on the concept of the relative gain array (RGA), it is found that the RGA can be derived using steady-state sensitivity analysis. Then, the steady-state characteristics of the typical electrical components in the islanded network are considered, and the analytical expression for calculating the RGA is derived. Based on a typical system, a variable pairing scheme is then suggested using the calculated RGA elements. The time-domain simulations are conducted using PSCAD/EMTDC, and the results verify the feasibility and advantages of the suggested variable pairing scheme. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Grid-forming control is a promising solution for renewable power integration. This work presents a variable pairing scheme for the voltage controller of V/f controlled modular multilevel converter in an islanded network with a synchronous machine, which is a special type of grid-forming control. Based on the concept of the relative gain array (RGA), it is found that the RGA can be derived using steady-state sensitivity analysis. Then, the steady-state characteristics of the typical electrical components in the islanded network are considered, and the analytical expression for calculating the RGA is derived. Based on a typical system, a variable pairing scheme is then suggested using the calculated RGA elements. The time-domain simulations are conducted using PSCAD/EMTDC, and the results verify the feasibility and advantages of the suggested variable pairing scheme.

This paper deals with modelling and robust control of linear multivariable uncertain systems based on the new linear multivariable ARX (Auto-Regressive with eXogenous input)-Laguerre model and the loop-shaping design procedure with the relative gain array theory. In fact, to guarantee significant parameter number reduction of the multivariable ARX-Laguerre model compared with the classic multivariable ARX model, we propose the optimization of the Laguerre poles of the model using the genetic algorithm where the Fourier coefficients are identified using the recursive least square method. Later, the optimized multivariable ARX-Laguerre model is exploited to propose a robust control algorithm for linear multivariable uncertain systems. Indeed, we propose to combine the loop-shaping design procedure approach and the relative gain array theory to develop a simplified final robust controller guaranteeing reference tracking and robust stability against parametric uncertainties. This proposition aims for the simplification of the control's scheme by adjusting the weighting matrix and the final robust controller calculated from the loop-shaping design procedure for a simpler and more experimentally applicable control scheme. The identification of Fourier coefficients and Laguerre poles as well as the robust multivariable control algorithm are experimentally validated on a laboratory coupled two-tank system showing good results in terms of modelling and attending desired control performances. [ABSTRACT FROM AUTHOR]

Input-output pairing effectively minimizes the loop interaction in MIMO processes and avoids integral instability. In this article, a modified Relative Normalized Gain Array is proposed for the Input-Output Pairing and design of the First-order and Second-order Equivalent Transfer function. The proposed modified Relative Gain Array (mRNGA) matrix is derived by Normalizing the Relative Gain Array matrix with a normalization factor, which is calculated by minimizing the Integral Square Error of the given MIMO process. After that, the first order and second order Equivalent Transfer function is design by the derived mRNGA matrix, which offers an improved estimation of the Effective open-loop transfer function of the given MIMO process. The proposed method is corroborated with the help of the Input-Output pairing examples up to the 5 × 5 MIMO processes and three ETF design example. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient discrete‐time decoupling algorithm for multiple input multiple output (MIMO) systems having strong coupling between inputs and outputs. A design method for discrete decouplers is proposed to eliminate the cross‐coupling effects present in MIMO systems. The proposed decoupling technique is based on relative gain array (RGA) approach of MIMO system. In order to perform closed‐loop control, individual discrete‐time PID controllers are designed based on Kharitonov theorem for each of the SISO control loops of the resulting decoupled MIMO system. The closed‐loop performance of the MIMO system under consideration is investigated in simulation and in real time which illustrate that the proposed decoupling algorithm satisfactorily nullifies the interaction between the inputs and outputs. The control scheme exhibits perfect tracking of the reference commands even in presence of disturbances. Twin rotor MIMO system (TRMS) is considered as the real‐time example to validate the proposed method. Further, the performance of the compensated TRMS system is analyzed in frequency domain in presence of common actuator nonlinearities dead zone and saturation together. The performances of the controllers are found to be efficient even in presence of actuator nonlinearities. [ABSTRACT FROM AUTHOR]

Dynamometers are used to evaluate the real-world performances of drivetrains in various loading conditions. Due to its superior power density, high bandwidth, and design flexibility, a hydrostatic power-regenerative dynamometer is an ideal candidate for hydrostatic wind turbine transmission testing. A dynamometer can emulate the wind turbine rotor dynamics and allow the investigation of the performance of a unique hydrostatic drivetrain without actually building the physical system. The proposed dynamometer is an energy-efficient system with counter-intuitive control challenges. This paper presents the dynamics, control synthesis, and experimental validation of a power-regenerative hydrostatic dynamometer. A fourth-order non-linear model with three inputs was formulated for the dynamometer. The strength of input–output couplings was identified, and two different decoupling controllers were designed and implemented. During wind turbine testing, the synchronous generator turns at a constant speed and the system model is linear. A steady-state decoupling controller was developed for independent control of the drive and transmission. The implemented decoupling controller demonstrated a negligible change in rotor speed for a 40 bar step increase in pressure, but a 20 bar pressure spike for a 4 rpm step change in rotor speed. However, during starting and stopping, the synchronous generator speed is not constant, and the system model is nonlinear. Therefore, a steady-state decoupling controller will not work. Thus, a decentralized controller with feed-forward control and gain scheduling was designed and implemented. A reference command was designed to avoid cavitation, pressure spikes, and power flow reversal during start-up. The experimental results show precise tracking in steady-state and transient operations. The decentralized controller demonstrated a negligible change in rotor speed for a 40 bar step increase in pressure but a 100 bar pressure spike for a 4 rpm step increase in rotor speed. The pressure spike was reduced by 80 bar with the implementation of feed-forward gain. The proposed electro-hydro-mechanical system requires less power and has the potential to reduce energy expenditure by 50 % . [ABSTRACT FROM AUTHOR]

In this paper, the design and application of robust interactive PID control for a medical robot system is presented. The aim is to solve the problem of precise position tracking required for human walking, using a simple type of control while taking into account the interactions of the systems’ input and outputs. The medical robot system can be interpreted as pendulum links to obtain a complete motion of all muscles. Two control actions are required to be applied for the two joints. The interactions of this multivariable system have been examined using the relative gain array (RGA). In this work, PID and Fuzzy PID controllers are implemented with interactions effects. In addition, two other non-conventional types of PID control structures have been considered for comparison, where the RGA cannot be applied. These are the two-degree PID (2DoFPID) and nonlinear PID (NPID) controllers. Simulation results show that in the case of not considering the interaction effects, the Fuzzy PID controller can provide an improvement of 44% as compared with conventional PID controller. While this improvement has been increased to 70% with the consideration of interaction effects. Meanwhile, NPID controller shows higher rise and settling times (almost more than 2 seconds for the settling time). While 2DoFPID controller shows difficulty in implementation due to its highly chattered control signals with higher overshoots in the transient response as compared with the results of the interactive Fuzzy PID controller. Finally, robustness against disturbances and system uncertainties has been tested with all the developed controllers. It has been concluded that the interactive Fuzzy PID controller achieves better performance in terms of less ISE, settling time, rise time, and overshoot. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study presents an analysis method of harmonic interaction characteristics between direct‐drive wind turbines (DDWTs) based on αβ coordinates and the relative gain array (RGA). First, considering the digital delay of inverters, the capacitive current feedback active damping is applied to suppress the resonance of LCL filter, and the output current of DDWT is regulated by quasi‐proportional resonant controller in the αβ coordinates and then combined with the topology of the direct‐drive wind farm (DDWF), the transfer function matrix of the DDWF is established. Second, based on the RGA principle, the relationship between parameters and harmonic interaction characteristics is quantitatively analysed. The results show that with the proportional coefficient increasing, the degree of negative interaction between DDWTs is strengthened, which increases the harmonic content in the negative interaction frequency band. However, the increase of resonance coefficient and number of DDWTs will weaken the degree of negative interaction. In addition, with the increase of capacitive current feedback coefficient and grid inductance, the interaction frequency gradually decreases. Finally, the DDWF model is built both on Matlab/Simulink and StarSim + PXI hardware‐in‐the‐loop platform to verify the analytical results. The harmonic interaction characteristics can be used to guide the parameter design of DDWTs, so as to optimise power quality of the wind farm. [ABSTRACT FROM AUTHOR]

• Establish an inertia response model based on DC power flow. • Introduce RGA to evaluate inertia response. • Present a spatial characteristics analysis of inertia response using RGA. This paper proposes a novel method to evaluate the spatial distribution characteristics of inertia response in power systems. Under the effect of grid topology and the inertia distribution of generators, the influence of power disturbance on frequency variations during inertia response has distinctive spatial characteristics. Compared with early studies, this paper focuses on spatial characteristics and presents a quantitative method to evaluate inertia response. This paper first builds an inertia response model that retains spatial distribution characteristics by adopting DC power flow. Then, it introduces the relative gain array (RGA) theory for calculating the relative gain array between the rate of change of frequency (RoCoF) and the active power disturbance during inertia response. Based on the magnitude and distribution of the relative gain array elements, the paper conducts a quantitative analysis of inertia response, thus presenting a description of the spatial characteristics of inertia response. Simulation results of the IEEE 39-bus system validate the effectiveness of the proposed method in evaluating the spatial characteristics of inertia response. [ABSTRACT FROM AUTHOR]

• Reduced fouling potential by considering control pairings. • Relative gain array method was used to analyse cross couplings. • The different control pairings were compared numerically and experimentally. • A pilot plant was used to experimentally test the considered pairings. • Accounting for control loops interactions improved control performance. Despite membrane filtration being extensively used in many industries, it is not widely used for offshore produced water treatment because of the large installation footprint required. Commonly, PID-controllers are deployed to maintain the operating conditions that minimize fouling, but the design of the controllers is rarely highlighted. The interaction between the deployed controllers can cause undesired performance and even instability. In this study, the relative gain array method was used to find the set of control pairings that minimized the interaction between the control loops. Experimental results showed that by accounting for cross couplings in the design phase of the control system, the controllers performance in terms of reference tracking can be improved significantly. By improving the reference tracking and disturbance rejection capabilities of the filtration system, the selected operating point which minimizes fouling growth, can be maintained consistently subject to disturbances in terms of varying feed flow rate. Better tracking of the operating point can reduce membrane resistance, and consequently reducing the operating cost. [ABSTRACT FROM AUTHOR]

The Combined matrix of a nonsingular matrix A is defined by ϕ (A) = A ∘ A - 1 T where ∘ means the Hadamard (entrywise) product. If the matrix A describes the relation between inputs and outputs in a multivariable process control, ϕ (A) describes the "relative gain array" (RGA) of the process and it defines the Bristol method (IEEE Trans Autom Control 1:133–134, 1966) often used for Chemical processes (McAvoy in Interaction analysis: principles and applications. Instrument Society of America, Pittsburgh, 1983; Papadourakis et al. in Ind Eng Chem Res 26(6):1259–1262, 1987; Wang et al. in Chem Eng Technol, 10.1002/ceat.201500202, 2016; Kariwala et al. in Ind Eng Chem Res 45(5):1751–1757, 10.1021/ie050790r, 2006; Golender et al. in J Chem Inf Comput Sci 21(4):196-204, 10.1021/ci00032a004, 1981). The combined matrix has been studied in several works such as Bru et al. (J Appl Math, 10.1155/2014/182354, 2014), Fiedler and Markham (Linear Algebra Appl 435:1945–1955, 2011) and Johnson and Shapiro (SIAM J Algebraic Discrete Methods 7:627–644, 1986). Since ϕ (A) = (c ij) has the property of ∑ k c ik = ∑ k c kj = 1 , ∀ i , j , when ϕ (A) ≥ 0 , ϕ (A) is a doubly stochastic matrix. In certain chemical engineering applications a diagonal of the RGA in wchich the entries are near 1 is used to determine the pairing of inputs and outputs for further design analysis. Applications of these matrices can be found in Communication Theory, related with the satellite-switched time division multiple-access systems, and about a doubly stochastic automorphism of a graph. In this paper we present new algorithms to generate doubly stochastic matrices with the Combined matrix using Hessenberg matrices in Sect. 3 and orthogonal/unitary matrices in Sect. 4. In addition, we discuss what kind of doubly stochastic matrices are obtained with our algorithms and the possibility of generating a particular doubly stochastic matrix by the map ϕ . [ABSTRACT FROM AUTHOR]

Different APFs (Active Power Filter) interact with each other when multiple APFs are connected to the grid, and the interactions deteriorate the control performance of APFs and even lead to system instability. This paper presents a method to analyze the dynamic interaction of multiple APFs in a weak grid. This method uses the Norton equivalent principle to establish the mathematical model of a single APF. The mathematical model of the multiple APFs connected to the grid is set up based on the single APF mode. The RGA (Relative Gain Array) principle is used to analyze the interactions among multiple APFs. Besides, this paper analyzes the effect of changing circuit parameters and controller parameters on the change of the interactions. The strategy of weakening and eliminating the interaction is proposed based on rational selection and combination of parameters. Analysis, along with time domain simulation and experimental results, is presented to verify the feasibility and effectiveness of the proposed method and strategy. [ABSTRACT FROM AUTHOR]

As there is presently insufficient information on the relation between sequencing method and controllability, this study is aimed to explore such relation between the driving force sequencing method and controllability. The methodology used consists of three stages; sequence synthesis, energy comparison, and controllability comparison. In the first stage, an energy efficient distillation columns sequence is synthesised using the driving force method, and other sequences are synthesised for comparison purposes. In the second stage, their energy usages are compared. In the third stage, relative gain array method is used to determine the controllability; the interaction between control loops in a sequence. The methodology is applied to a four component hydrocarbon mixture. Results showed that the sequence with the best controllability is the one synthesised based on the driving force approach. [ABSTRACT FROM AUTHOR]

So far, not much is known about the controllability of distillation columns derived from algorithms as there are many types of algorithms exist and many forms of mixtures to be separated. It is therefore aimed in this study to analyse the controllability of a distillation columns design method, known as the driving force approach. This study makes use of a four stage methodology and those stages are; sequence design, energy comparison, sensitivity comparison, and controllability comparison. In the first stage, a distillation columns sequence is designed based on the driving force algorithm. In the second stage, the energy consumption of the different designs is compared. In the third stage, the sensitivity of the different designs is compared and in the final stage the relative gain array method is used to determine the interaction between the designs’ control loops. The methodology is applied to a five component hydrocarbon mixture. Results showed that while the driving force design is the most energy efficient and robust, it does not have the best controllability. [ABSTRACT FROM AUTHOR]

The combined matrix of a nonsingular matrixAis the Hadamard (entrywise) product. This paper deals with the characterization of the diagonal entries of a combined matrixC(A) of a given nonsingular real matrixA. A partial answer describing the diagonal entries ofC(A) in the positive definite case was given by Fiedler in 1964. Recently in 2011, Fiedler and Markham characterized the sequence of diagonal entries of the combined matrixC(A) for any totally positive matrixAwhen the size is 3. For this case, we characterize totally negative matrices and we find necessary and sufficient conditions for the sequence of diagonal entries ofC(A), in both cases, symmetric and nonsymmetric. [ABSTRACT FROM PUBLISHER]

Control of multi-input multi-output (MIMO) plants poses a challenging control problem. The problem becomes much more complicated if the degree of interaction between the inputs and outputs is high. Most of the MIMO control schemes do not take into consideration the cross-coupling effect and are based on either decoupled or decentralized control schemes. These schemes can offer acceptable control performance if the degree of interaction is low. Ignoring the interaction is unrealistic for many plants and employing multiple MISO controllers results in degraded control performance. Almost all such strategies require a plant model a priori. In this work, an extension of SISO model-free fuzzy adaptive controller (MFFAC) is proposed for MIMO plants while taking into consideration the cross-coupling effect. No a priori knowledge about the plant is assumed, and the control scheme does not make use of any decoupler. SISO MFFAC is based on a special type of reinforcement learning, i.e., feedback error learning (FEL). The control architecture of SISO MFFAC is modified to work with MIMO plants by proposing a novel FEL scheme. The novel FEL mechanism incorporates the interaction between the input and output of a MIMO process by using relative gain array (RGA). Simulation results have demonstrated the efficacy of the proposed MIMO control scheme. [ABSTRACT FROM AUTHOR]

With the advent of more than Moore’s law era, control of plasma etch process is expected to become inevitable. Given that highly complex plasma is a medium of etch processes, plasma parameters are key factors to be controlled. In addition, highly interactive plasma characteristics require multivariate control schemes. In this paper, we design a multi-loop controller which controls effective plasma parameters in Ar plasma conditions. The effective plasma parameters obtained by optical emission spectroscopy are paired with plasma reactor instrumental variables through relative gain array and singular value decomposition. Each single input-single output (SISO) system based on the pairing result shows successful disturbance rejection performance but interactions between SISO controllers occur. In order to handle the interactions, 2 × 2 multiple input-multiple output (MIMO) controllers with and without decouplers are simulated to track set point change. Based on the simulations, a MIMO controller with decouplers is implemented in a capacitively coupled plasma reactor and show feasible control performance without interaction. Hopefully, the results introduced in this paper contribute to making progress in plasma parameter control. [ABSTRACT FROM AUTHOR]

Input-output pairing is an important problem in control system design and is often performed using the relative gain array (RGA) based approaches. While RGA-based approaches have been very successful in many applications, they have some well-known limitations. For example, they may give results which are not consistent with the physical topology since only the strength of interaction between inputs and outputs is taken into account in the RGA. In this work, we propose a new measure for input-output pairing that explores both strength and structural information in input-output coupling. Specifically, we take advantage of the tool of relative degree to measure the physical closeness of input-output pairs and to explore the strength of interaction progressively with respect to the relative degree. We call the proposed measure relative sensitivity array (RSA) between inputs and outputs. Detailed analysis is performed to reveal the relationship between the gain matrix used in the RGA and the sensitivity matrix in the RSA from a mathematical point of view. Since the RSA is an analog of the RGA, many existing pairing guidelines developed for the RGA can be used in the proposed RSA-based pairing. The proposed RSA-based approach is applied to two examples. The results show that pairs formed by the proposed approach are consistent with the physical topologies of the processes. Also, the results show that the proposed approach can handle larger systems that cannot be effectively handled by RGA-based approaches. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1226-1235, 2017 [ABSTRACT FROM AUTHOR]

Call an n -by- n invertible matrix S a Perron similarity if there is a real non-scalar diagonal matrix D such that S D S − 1 is entrywise nonnegative. We give two characterizations of Perron similarities and study the polyhedra C ( S ) : = { x ∈ R n : S D x S − 1 ≥ 0 , D x : = diag ( x ) } and P ( S ) : = { x ∈ C ( S ) : x 1 = 1 } , which we call the Perron spectracone and Perron spectratope , respectively. The set of all normalized real spectra of diagonalizable nonnegative matrices may be covered by Perron spectratopes, so that enumerating them is of interest. The Perron spectracone and spectratope of Hadamard matrices are of particular interest and tend to have large volume. For the canonical Hadamard matrix (as well as other matrices), the Perron spectratope coincides with the convex hull of its rows. In addition, we provide a constructive version of a result due to Fiedler [9, Theorem 2.4] for Hadamard orders, and a constructive version of the Boyle–Handelman theorem [2, Theorem 5.1] for Suleĭmanova spectra. [ABSTRACT FROM AUTHOR]

A novel technique to determine the best pairing of inputs and outputs for the design of wide-area damping controllers (WADCs) is proposed. The method extends the conventional use of the relative gain array (RGA) for interacting control systems, to the block relative gain (BRG) to analyze interactions among multi-input multi-output (MIMO) controllers. First, geometric measures of controllability and observability are used to screen the most effective stabilizing signals for partially centralized control of large interconnected power systems. Then, the BRG analysis is used to quantify the potential for adverse interactions between a given set of controllers or subsystems. This gives candidate sets for supplementary controllers which are solved using linear matrix inequality (LMI) techniques and are evaluated in closed-loop mode to detect and quantify process interactions. In general, this approach also allows better coordination of control capabilities and the use of interaction measures to help in the choice of control location and structure. The effectiveness of the proposed control scheme on system behavior is tested on a realistic 5-area model of the Mexican interconnected power system. [ABSTRACT FROM AUTHOR]

Some plants have better "built-in" disturbance rejection capabilities than others, that is, their dynamic resilience (controllability) with respect to disturbance rejection is better. In the paper we consider controller independent disturbance measures for six classes of problems:

Abstract: This work implements model-based controls for the simulation of reverse osmosis (RO) desalination process for both servo and regulatory problems. Pressure from high-pressure (HP) feed pump and recycle ratio (RR) are manipulated inputs to the RO process, while permeate flow rate, concentration and pH are considered as output. Control configuration for this 2x3 process is selected using regular interaction analysis methods. Two control strategies are adopted, namely, multiloop internal model control–proportional integral controller (IMC-PI) under centralized scheme and multivariable PI controller with decoupler under decentralized scheme. The non-square model for synthesizing the model-based control purpose is formulated using the mass balance continuity equation and model parameters are estimated. In both the cases, satisfactory results are obtained by reducing the fluctuation in the controlled parameters in the closed loop control systems. The performances of the two controllers are compared using the integral of absolute error (IAE) performance index criteria. Results with MPC are encouraging for implementation on desalination process. [Copyright &y& Elsevier]

This paper presents automatic guidance control of a single-articulated all-wheel-steered vehicle being developed by the Korea Railroad Research Institute. The vehicle has an independent drive motor on each wheel except for the front axle. The guidance controller is designed so that the vehicle follows the given reference path within permissible lateral deviations. We use a three-input/three-output linearised model derived from the nonlinear dynamic model of the vehicle. For the purpose of simplifying the controller and making it tunable, we consider a decentralised control configuration. We first design a second-order decoupling compensator for the two-input/two-output system that is strongly coupled and then design a first-order controller for each decoupled feedback loop by using the characteristic ratio assignment method. The simulation results for the nonlinear dynamic model indicate that the proposed control configuration successfully achieves the design objectives. [ABSTRACT FROM AUTHOR]

Highlights: [•] An effective procedure to collect and analyze sensor data with respect to manipulated variables at one time is proposed. [•] A numerical criterion is developed for effective selection of important sensor variable. [•] The usefulness of our technique is well demonstrated in a virtual metrology for semiconductor manufacturing. [ABSTRACT FROM AUTHOR]

By a plant's inherent control limitations we mean the characteristics of the plant which will cause poor control performance irrespective of what controller is used. Another frequently used term is 'dynamic resilience' which is the best closed-loop performance achievable using any controller. Since a plant's dynamic resilience cannot be altered by change of the control algorithm, but only by design modifications, it follows that the term controllability provides a link between process design and process control. In this paper we focus on two aspects of controllability. The plants' sensitivity to disturbances and the limitations imposed by interactions when using decentralized control. We use simple tools such as the RGA, the PRGA (Performance RGA) and the closely related Closed Loop Disturbance Gain (CLDG). For example, if kth column of the CLDG is large, then this indicates that disturbance k will be difficult to reject. This may pinpoint the need for modifying the process. The PRGA provides a measure of interaction which also includes one-way coupling. In the paper we apply these measures to distillation column control and fluid catalytic cracker (FCC) control.

• A review and comparison of mathematical models for bioreactors. • Development and implementation of a mathematical model for a perfusion bioreactor. • Global sensitivity analysis is performed, and the results are analyzed for two different scenarios. • A relative gain analysis is performed and interpreted. Perfusion bioreactors are important tools in tissue engineering that are used for cell cultivation. Unfortunately these types of processes are not yet fully understood in literature and information about the model is scarce. Furthermore, mathematical models that are used for perfusion bioreactors have posed significant challenges. This work presents a concise overview and analysis of mathematical models for a perfusion bioreactor process. The comprehensive mathematical model of convection and diffusion in a perfusion bioreactor, combined with cell growth kinetics, is developed using Computational Fluid Dynamics. The model describes the spatio-temporal evolution of glucose concentration, oxygen concentration, lactate concentration and cell density within a polymeric scaffold. For an in-depth understanding of this type of processes, global sensitivity analysis and simulations is performed using the method of high-dimensional model representation (RS-HDMR). A quantitative analysis of the complex kinetic mechanisms using recently developed advanced mathematical approaches to global sensitivity and uncertainty analysis through RS-HDMR can be exploited to investigate the important features of the perfusion bioreactor process as well as possible factors underlying qualitative discrepancies. Moreover, for a further understanding of the process, a relative gain analysis is performed. The results will help us gain an in depth understanding of the process and will be used as the foundation for advanced control algorithms that will facilitate manufacturing for any type of cell culture using a continuous perfusion bioreactor thus paving the way towards Industry 4.0. [ABSTRACT FROM AUTHOR]

The mathematical model for the two interacting tanks system was derived and the dynamic behavior of this system was studied by introducing a step change in inlet flow rate. In this paper, the analysis of the interaction loops between the controlled variable (liquid level) and manipulated variable (inlet flow rate) was carried out using the relative gain array. Also decoupling technique is applied to eliminate the effect this interaction by design suitable decouplers for the system. The results show that the gain of each loop is cut in half when the opposite loop is closed and the gain of other loop changes sign when the opposite loop is closed. The decoupling method show that the liquid level of tank one is constant when the second inlet flow changes and to keep the liquid level of tank two constant the first inlet flow must be changed.

Power oscillations can be damped effectively through modulation of both active and reactive power of a voltage source converter based high voltage direct current link. The challenge, however, is how to coordinate the control action properly at the two ends of the link without using a centralized control scheme, which requires fast communication of control signals to remote actuator (converters) sites. A full centralized controller may result in a closed-loop performance worse than that of an open loop in case of a communication loss of feedback signal(s). Alternatively, with a block-diagonal control structure, the individual control loops are decoupled from each other, which is not only easier to implement in a decentralized way, but also shown to guarantee a certain level of performance. Here, the concept of homotopy is applied to obtain a single block-diagonal controller from a set of full controllers, individually designed to ensure specified closed-loop performance for a set of operating conditions. Simulation studies in DIgSILENT PowerFactory are carried out on two test systems to demonstrate both the robustness and control coordination in a decentralized framework. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents a loop pairing method for determining the control configuration for multi-input–multi-output (MIMO) processes represented by Takagi–Sugeno (T–S) fuzzy models. The method is simple with straightforward calculation and it provides more accurate results compared with existing fuzzy pairing approaches, since both steady-state and dynamic information for the system is utilized. Each individual loop in the MIMO process is represented by a T–S fuzzy model based on the data and the models are then assembled to form the MIMO model. Simple formulae are derived to calculate the steady-state and dynamic information for the loops. In this way, interactions among the loops can be assessed and loop pairing can be determined according to the relative normalized gain array (RNGA) criterion. Two examples are provided to show that loop pairing decisions obtained from T–S fuzzy models are the same as those obtained from precise mathematical models. This demonstrates the effectiveness of the proposed interaction measure and the loop pairing method. [Copyright &y& Elsevier]