Freedom Internal Model Control Research Articles

Closed-Loop Test Based Parametric Independent Control of DC–DC Boost-Converter Using Two Degree of Freedom Internal Model Control Scheme

Closed-Loop Test Based Parametric Independent Control of DC–DC Boost-Converter Using Two Degree of Freedom Internal Model Control Scheme

An internal model control method for wave rotor refrigeration process based on Harris hawks optimization

A novel internal model control (IMC) method for wave rotor refrigeration process (WRRP) based on Harris hawks optimization (HHO) is presented in this paper. Firstly, an identification model is established by the test data of the WRRP. In order to reduce the complexity of the model, the Routh order reduction method was used to reduce the order of the identification model. This procedure yields an approximate second order model with time delay for the WRRP. Secondly, an IMC method based on HHO is proposed after analyzing the time delay characteristics of the WRRP model. This method improves the traditional IMC structure, and introduces a three degree of freedom IMC structure. The parameters of the controller are optimized by HHO to make the comprehensive performance index of the system reach the best. Simulation results demonstrate that the proposed method can achieve a good performance of tracking and disturbance rejection.

Fast Harmonic compensation in hybrid HVDC offshore system

Hybrid HVDC systems have been proposed as an alternative for nominal VSC-Based HVDC for offshore applications. Hybrid HVDC systems consist of an offshore power station composed of the connection of high-power diode rectifiers in series with a fractional power VSC-HVDC. This hybrid configuration allows large power transfer from offshore sites, with the added robustness, simplicity and efficiency of uncontrolled rectifiers. In this research, a robust and fast-acting controller, the Two Degrees of Freedom Internal Model controller (2DF-IMC), is used to control the active power filter features of the fractional-power VSC-HVDC system, resulting in a much faster overall THD reduction in the offshore AC currents in dynamic conditions (i.e. time-varying wind power) when compared with standard active power filter controllers. This improvement is the direct consequence of the fast closed-loop dynamics of the 2DF-IMC controller that do not require filtering stages. Additionally, the increased closed-loop response time did not affect the overall robustness of the control system, thanks to the enhanced disturbance rejection capabilities of the 2DF-IMC configuration.

Suppression of Wind Generator Speed Vibration Based on the Internal Model Control with Three Degrees of Freedom

When the wind power system is working in the maximum wind energy tracking area, or when its mechanical drivetrain system vibrates and the vibration frequency is relatively high, the system cannot suppress the speed vibration of the generator in the drivetrain system by adjusting the pitch angle. In this paper, a generator speed control system based on the three degrees of freedom internal model control (3-DOF-IMC) is established to control the generator speed. Thus, a scheme of using the feedback filter in the 3-DOF-IMC to suppress generator speed vibration caused by drivetrain shaft elasticity and gear clearance in the drivetrain system is proposed. Firstly, the vibration problem and waveform of the two-mass wind power drivetrain systems are discussed, and the generator’s vector control and speed control systems are analyzed. Secondly, the principle of the 3-DOF-IMC is described, and the influence of the three controllers on the speed tracking performance and anti-interference performance of the generator is discussed. The suppression ability of the feedback filter for different forms of disturbance signals is emphasized. Finally, the feedback filter controls the generator speed and eliminates the influence of drivetrain vibration on the generator speed. To verify the superiority of the proposed method, the vibration suppression effect, tracking performance and anti-interference performance of the proposed method are compared with the engineering design method (EDM) and conventional IMC (1-DOF-IMC) method. When the parameter α/β = 0.66, the generator speed amplitude overshoot of the proposed method is the same as the EDM. When α/β = 1, it is only 4% of the amplitude overshoot of the EDM. In addition, the tracking performance and anti-interference performance of the proposed method can be adjusted independently, and it is better than the EDM and the 1-DOF-IMC method.

Load Frequency Controller Design Based on the Direct Synthesis Approach Using a 2DoF-IMC Scheme for a Multi-Area Power System

To maintain reliable and sustainable power supply, the frequency should be kept constant under varying load conditions. The two degrees of freedom internal model control (2DoF-IMC) scheme is a robust control technique and is efficient for load-disturbance rejection problems in industrial process control. The asymmetry of IMC compared to other methods regarding controller design is that it does not guarantee the stability of the system by itself but is based on the stability of the controlled system. For the control of less-stable and unstable systems, it is therefore usually supplemented with an additional controller, establishing two degrees of freedom in the overall design. In this manuscript, the load-frequency-regulation problem was investigated using a 2DoF-IMC scheme for a single-area as well as a multi-area power system. In the 2DoF-IMC scheme, two controllers are used to control the set-point response and load-disturbance response separately. The set-point controller is designed through the internal model control (IMC) principle, whereas the load-disturbance rejection controller is designed via the direct-synthesis (DS) approach. In the DS approach, the closed-loop transfer function of the system model is matched with the desired closed-loop transfer function of the system and the disturbance-rejection controller is approximated at a very low-frequency point to obtain the proportional–derivative (PD) controller parameter. The simulation results of the proposed method provide satisfactory performance for load-frequency control (LFC) in the single-area power system and extended to two-area and four-area power systems. The effect of non-linearity, such as generation rate constraint (GRC), was investigated in the single-area power system to establish the efficacy of the proposed method. A random step loading pattern was also considered to confirm the robustness of the proposed method. The overall performance of the proposed control scheme is comparatively better than the recently reported work.

Stable control of the high-speeding magnetically suspended rotor based on extended state observer and two-degree freedom internal model control for control moment gyros with serious moving-gimbal effects

For a magnetically suspended control moment gyro (MSCMG), which is an ideal attitude actuator for its large outputting control moment and fast response, the moving-gimbal effects due to the coupling between the moving gimbal and high-speeding rotor will make the magnetically suspended rotor (MSR) unstable. To improve control precision, both the dynamic model of MSR and the feedback linearization control are done to decouple tilting motion, and poles of the system are reconfigured to reduce control error. To suppress the varying disturbance moments caused by moving-gimbal effects, an extended state observer (ESO) is originally designed to estimate and compensate them timely and accurately. To improve system robustness, a two-degree freedom internal model control (2-DOF IMC) is researched to suppress model error. Compared with existing proportional integral derivative (PID) control method, simulations done on a single gimbal MSCMG with 200 N.m.s angular momentum indicated that this presented control method with ESO and 2-DOF IMC can suppress the moving-gimbal effects more effectively and make the rotor suspension more stable.

Experimental validation of fractional order internal model controller design on buck and boost converter

In this paper, fractional order internal model control technique is formulated for non-ideal dc–dc buck and boost converter. The fractional order internal model control approach integrates the concept of Commande Robuste d’Ordre Non Entier principle for tuning a fractional order filter with internal model control scheme. The final controller can be expressed as a series combination of proportional integral derivative controller and a fractional order low pass filter. To assess the robustness of the proposed fractional order internal model control scheme, both the servo response and regulatory response of the dc–dc converters are investigated in the presence of disturbances. The efficacy of fractional order internal model control technique is demonstrated via comparison with 2 degrees of freedom internal model control scheme. Furthermore, an experimental validation of fractional order internal model control is conducted on laboratory setup, and a dSPACE 1104 microcontroller is used for hardware implementation. The simulation results and the hardware validation are a testimony to the effectiveness of fractional order internal model control technique.

An AHP based optimized tuning of Modified Active Disturbance Rejection Control: An application to power system load frequency control problem

This paper presents Modified Active Disturbance Rejection Control (MADRC) scheme and a systematic procedure to tune its tuning variables via. observer and controller gains. The problem of tuning is formulated as a constrained multi-objective optimization problem. Depending upon the application appropriate objective functions are chosen, and a unified objective is developed based on weighted sum approach. Five different weight combinations are considered, which result in five objective functions. Each objective function is individually optimized using Teaching-Learning Based Optimization (TLBO), this leads to five sets of tuning variables. Best among five alternatives will be selected based on Analytical Hierarchy Process (AHP). The effectiveness of this approach is validated through its application to a power system with load frequency control problems. Different simulation examples involving single-area and multi-area power systems are considered in the presence of sudden load disturbances, model uncertainties, and parameter variations. Further stability analyses are carried out in a standard two-degree of freedom Internal Model Control (IMC) framework.

Design of two degree of freedom-internal model control configuration for load frequency control using model approximation

In this paper, a modified two degree of freedom-internal model control structure is proposed with dual feedback loop configuration for load frequency control problem of the single area and two area non-reheated power systems to achieve better transient and steady state performance. Predictive model of the proposed configuration is derived through Routh, Padé and SOPDT approximations. Hence, for all three cases, the proposed configuration is simulated considering the single area and two area power systems with non-reheated turbine along with 50% parametric uncertainty. Finally, a comparison with existing techniques is included to validate the effectiveness and performance of the proposed control configuration through responses and error indices. It is observed that the proposed scheme generates better results under parameter variations.

IMC-based Design for Teleoperation Systems with Time Delays

The presence of time delays in communication introduces a limitation to the stability of bilateral teleoperation systems. In this study, we address the design of Internal Model Control (IMC)-based controllers for teleoperation systems with arbitrary time delays. The two degrees of freedom IMC structure is utilized for the master and the slave respectively and thus the passivity-assumption on the external forces is not required. The stability of the overall system is analyzed by regarding the whole system as a multivariable system. A performance-oriented controller design process which guarantees the delayed tracking between the master and the slave is also given. Finally, an example is given to validate the effectiveness of the proposed method.

A modified two-degree of freedom-internal model control configuration for load frequency control of a single area power system

In this paper, we propose a modified two degree-of-freedom internal model control structure, with dual feedback loop configuration for the load frequency control problem of a single-area power system. Our main objective is to achieve better transient and steady state performance. The predictive model of the proposed configuration is derived through the stability equation method, which preserves the stability of the model. The proposed scheme is simulated for a single-area power system with nonreheated turbine and 50% parametric uncertainty. It is observed from the responses and the performance indices that the proposed control configuration gives better results compared to well-known existing techniques.

Projeto de Controlador Baseado no Modelo Interno com 1 Grau de Liberdade Utilizado em Injeção de Potência Ativa na Rede Monofásica a Partir de Geração

Este trabalho apresenta o projeto de um controlador baseado no modelo interno (Internal Model Control – IMC) com 1 grau de liberdade (1 Degree of Freedom – 1 DOF) aplicado a um inversor de tensão conectado à rede elétrica monofásica. É apresentada a modelagem matemática do inversor com filtro LCL, que é utilizada para o projeto do controlador IMC 1DOF, e analisada a compensação da realimentação interna ao sistema, correspondente ao desacoplamento da tensão da rede, através da estratégia de realimentação à frente (Feedforward). Visando-se uma base de comparação, também é aplicado ao sistema, um bem conhecido controlador Proporcional-Ressonante (P+Res) e são apresentados resultados de simulação e experimentais, os quais permitem uma análise e comparação de desempenho de ambos os controladores.

System Identification using GA and its Application to Internal Adaptive Model Control

The requirement for the high quality control of complex and/or structure-unknown plant is growing in the real-world industrial machine. Indiect Adaptive Control (IAC), which identifies model and updates the controllers automatically, is expected as on of the promising way to meet this requirement. The conventional IAC, however, required to know the structure of the structure of the controlled plant, i.e. the order of its transfer function in advance. This paper presents a new IAC scheme which makes use of Genetic Algorithm (GA) in its identification part. In the proposed framework, the information on the order of the plant is not required since GA searches both the structure of the plant dynamics and its parameters autonomously. A two-degree-of freedom Internal Model Control (IMC) is adopted as a basic control architecture since the indirect adaptation can be harmoniously embedded in it. The effectiveness of the proposed scheme is verified though numerical simulations and experiments applied to a velocity control of multi-mass systems.