Load Disturbance Conditions Research Articles

Optimised power control with extended phase shift in dual‐active‐bridge dc–dc converters

An optimised power control with extended phase shift (OPC-EPS) for dual-active-bridge (DAB) dc–dc converters is proposed to improve the efficiency and dynamic performance simultaneously. By combining the current stress optimised calculation with direct power control, the smaller current stress and higher efficiency can be achieved compared to the traditional extended phase-shift scheme, and the dynamic response of DAB converters can be significantly improved under the input voltage fluctuation or load disturbance conditions. Meanwhile, the OPC-EPS scheme has strong robustness and it has no dependence on the circuit parameters. Finally, experimental results have verified the excellent performance of proposed scheme and the associated analysis in this Letter.

Synergetic governing controller design for the hydraulic turbine governing system with complex conduit system

The hydraulic turbine governing system plays an indispensable role in maintaining the stability of electrical power system. In this paper, synergetic control theory is introduced to enhance the regulating ability of the hydraulic turbine governing system. For the purpose of describing the characteristics of objective system and deducing the synergetic control rule, a nonlinear mathematic model of a hydraulic turbine governing system with long tail race and two surge tanks is established. Furthermore, the nonlinear characteristic of the hydraulic turbine is described by six variable partial derivatives. For further investigation, the hydraulic turbine governing system is conducted to running under load condition when its coaxial generator connects to an infinite bus. Simulation experiments have been made under both load disturbance and three-phase short circuit fault conditions to compare the dynamic performances of proposed synergetic governing controller and classic PID controller. The results indicate that the proposed synergetic governing controller is an effective alternative in normal condition and a superior one in emergency. Moreover, the robustness of synergetic governing controller has also been discussed at the end of this paper.

Implementation and Comparison of Symmetric and Asymmetric Multilevel Inverters for Dynamic Loads

This paper implements and compares a symmetric hybridized cascaded multilevel inverter and an asymmetric multilevel inverter utilizing a switched capacitor unit for 17 level inverters. The symmetric hybridized multilevel inverter topology consists of a modified H-bridge inverter, which results in an increase in the output voltage to five level from the three level by using a bi-directional switch at the midpoint of a dual-input dc source. In the proposed asymmetric multilevel inverter, dc sources are replaced with the switched capacitor unit, which in turn boosts the output voltage and produces twice the voltage levels at the loads. The proposed topology with the staircase modulation technique has been verified using MATLAB–SIMULINK, and the results are experimentally executed with prototype models, which are interfaced with dSPACE RTI 1104. The results of the proposed topologies are experimentally obtained for steady state, and the performance of the same is tested under different resistive and inductive load disturbance conditions. The results substantiate that these multilevel inverter topologies are better stabilized during load disturbance conditions with low total harmonic distortion, a lesser number of switches, and increased output voltage levels, and these topologies well suit for renewable energy applications.

Multiple Model Predictive Functional Control for Marine Diesel Engine

A novel control scheme based on multiple model predictive functional control (MMPFC) is proposed to solve the cumbersome and time-consuming parameters tuning of the speed controller for a marine diesel engine. It combines the MMPFC with traditional PID algorithm. In each local linearization, a first-order plus time delay (FOPTD) model is adopted to be the approximate submodel. To overcome the model mismatches under the load disturbance conditions, we introduce a method to estimate the open-loop gain of the speed control model, by which the predictive multimodels are modified online. Thus, the adaptation and robustness of the proposed controller can be improved. A cycle-detailed hybrid nonlinear engine model rather than a common used mean value engine model (MVEM) is developed to evaluate the control performance. In such model, the marine engine is treated as a whole system, and the discreteness in torque generation, the working imbalance among different cylinders, and the cycle delays are considered. As a result, more reliable and practical validation can be achieved. Finally, numerical simulation of both steady and dynamic performances of the proposed controller is carried out based on the aforementioned engine model. A conventional well-tuned PID with integral windup scheme is adopted to make a comparison. The results emphasize that the proposed controller is with stable and adaptive ability but without needing complex and tough parameters regulation. Moreover, it has excellent disturbance rejection ability by modifying the predictive multimodels online.

Optimised inverter by switch sharing: a control solution for photovoltaic applications

Switch-sharing-based multilevel inverter can be useful to develop an improved-performance DC–AC converter for low-power photovoltaic applications. However, this cannot be fully achieved without having a reliable control solution. Hence, this study presents a smart control strategy equipped with an adaptive proportional–integral controller. The adaptive characteristic is established through a tuning module that continuously fine tunes only one parameter. With the tuning mechanism, the load current quality is able to be continuously retained at the acceptable level even during the presence of disturbances. To validate the control performance, experimental work has been conducted on a laboratory prototype under load-disturbance conditions.

Robust Stability of Networked Load Frequency Control Systems with Time-Varying Delays

In deregulated power system scenario coupled with smart grid technology, for networked load frequency control (LFC), an open communication structure, owing to low cost and flexibility, is preferred over dedicated networks in the feedback control loop for transmitting/receiving the data between the geographically displaced power system and the control center. In such a control scheme, closing the feedback loop through an open communication channel, in turn, introduces two additive time-varying delays of dissimilar characteristics in the feedback path. These delays degrade the performance of the closed-loop system, and exert a destabilizing effect on the overall system. In this paper, using Lyapunov-Krasovskii functional approach, a less conservative stability criterion is presented to ascertain delay-dependent stability of such network-controlled LFC systems with two additive time-varying delays in the feedback path in the presence of uncertain load disturbance conditions. Unlike the existing results, which are derived by combining these two delays into one, the proposed result considers the two delays as separate entities thereby imparting more generalization into the stability analysis. The effect of unknown exogenous load disturbance is incorporated by mathematically modeling them as a bounded non-linear time-varying function of current and delayed state vectors.

Bat algorithm optimized fuzzy PD based speed controller for brushless direct current motor

In this paper, design of fuzzy proportional derivative controller and fuzzy proportional derivative integral controller for speed control of brushless direct current drive has been presented. Optimization of the above controllers design is carried out using nature inspired optimization algorithms such as particle swarm, cuckoo search, and bat algorithms. Time domain specifications such as overshoot, undershoot, settling time, recovery time, and steady state error and performance indices such as root mean squared error, integral of absolute error, integral of time multiplied absolute error and integral of squared error are measured and compared for the above controllers under different operating conditions such as varying set speed and load disturbance conditions. The precise investigation through simulation is performed using simulink toolbox. From the simulation test results, it is evident that bat optimized fuzzy proportional derivative controller has superior performance than the other controllers considered. Experimental test results have also been taken and analyzed for the optimal controller identified through simulation.

Experimental Investigation on Shock Mechanical Properties of Red Sandstone under Preloaded 3D Static Stresses

Triaxial impact mechanical performance experiment was performed to study the mechanical properties of red sandstone subjected to three-dimensional (3D) coupled static and dynamic loads, i.e., three confining pressures (0, 5, and 10 MPa) and three axial pressures (11, 27, and 43 MPa). A modified 3D split Hopkinson pressure bar testing system was used. The change trend in the deformation of red sandstone and the strength and failure modes under axial pressures and confining pressures were analyzed. Results show that, when the confining pressure is constant, the compressive strength, secant modulus, and energy absorbed per unit volume of red sandstone initially increases and subsequently decreases, whereas the average strain rate exhibits an opposite trend. When the axial pressure is constant, both the compressive strength and secant modulus of red sandstone are enhanced, but the average strain rate is decreased with increasing confining pressure. The energy absorbed per unit volume is initially increased and subsequently decreased as the confining pressure increases. Red sandstone exhibits a cone-shaped compression–shear failure mode under the 3D coupled static and dynamic loads. The conclusions serve as theoretical basis on the mechanical properties of deep medium-strength rock under a high ground stress and external load disturbance condition.

Real power and frequency control of a small isolated power system

This paper describes the dynamic analysis of a small isolated power system comprising a wind turbine generator and a diesel generator. The analysis is carried out in time domain considering simplified models of the system components by taking into account the wind turbine pitch controller and the diesel engine speed governor. Wind disturbance model consisting components of gusting of wind, rapid ramp changes and random noise. The wind generator is always operated with its rated power and the additional power required by the load is supplied by the diesel generator. For better dynamic performances of wind–diesel system under wind and load disturbance conditions, two control schemes are used. In the first case, a proportional–integral (P–I) controller and in the second case a proportional–integral–derivative (P–I–D) controller are used. Gain parameters of these controllers are optimized using genetic algorithm (GA) and Particle swarm optimization (PSO) considering two different objective functions and the results are compared. The sensitivity analysis of the wind diesel system is carried out for parameter uncertainties and the stability of the system is analyzed using D-stability criterion. Analysis is also carried out to examine the effect of power injection to a 69 bus radial distribution network by wind–diesel isolated system.

Frequency Regulation in Hybrid Power System Using Iterative Proportional-Integral-Derivative H ∞ Controller

This study considers frequency regulation in a hybrid power system consisting of conventional and distributed generation resources. The performance of two controllers—an H ∞ design via linear matrix inequalities and an iterative proportional-integral-derivative H ∞ via linear matrix inequalities—is assessed to maintain frequency deviation profile in acceptable limits. In the latter control design, the iterative linear matrix inequality approach is used to tune proportional-integral-derivative controller parameters subjected to H∞ constraints in terms of the iterative linear matrix inequality. The efficacy of the control law and disturbance accommodation properties is shown. The robustness of these controllers is demonstrated in the hybrid power system with different load disturbance conditions, wind power, and parameter variations. Controller performance is compared with a suboptimal controller to demonstrate its superiority. It is found that the second controller design has satisfactory disturbance rejection properties and robustness against parameter variations over a wide range of conditions.

Energy efficient scheme for DC motor drives in parameter uncertainties

In conventional way of cost effective and easy to implement energy efficient scheme for DC motor drives, load perturbations are only taken into account. But, in real industrial applications the moment of inertia, friction coefficient, armature resistance and armature inductance vary as the operating conditions of the plant change. These parameter uncertainties have immense adverse effects on the system in practical applications with light loads, and load disturbance conditions. The proposed H∞ control–based approach ensures energy efficient operation of DC motor drives along with simultaneous robustness in multiple parameter uncertainties. This result in a profitable robust energy efficient approach of DC motor drive operation which can be used in real time industrial applications as robust and efficient operation ensures less overhead and in turn less overall costs. The success of the approach is demonstrated through results which confirm the system is stable and efficient even in multiple parameter uncertainties and load perturbations.

Simulation Research of Inverted Plasma Cutting Power Supply Based on Fuzzy Control

Focusing on load characteristics of inverted plasma cutting power supply, this paper puts forward a nonlinear control method. This method integrates fuzzy control technology into the controller of power supply, thereby optimizing dynamic characteristics of power supply. The SIMULINK simulation technology is also used. To compare steady-state precision, robustness, response speed and other control indexes between fuzzy control and conventional PI control, the comparative simulation experiments were made respectively under constant non-disturbance steady-state condition, aperiodic load disturbance condition, and periodic load disturbance condition. The simulation results show that power supply with fuzzy controller has perfect steady robustness, fast system response and strong harmonic suppression ability. The simulation model is accurate and reliable, and it can be an efficient tool for further studying mechanism and algorithm optimization of plasma cutting power supply.

Online Genetic-Fuzzy Forward Controller for a Robot Arm

The robot is a repeated task plant. The control of such a plant under parameter variations and load disturbances is one of the important problems. The aim of this work is to design Genetic-Fuzzy controller suitable for online applications to control single link rigid robot arm plant. The genetic-fuzzy online controller (forward controller) contains two parts, an identifier part and model reference controller part. The identification is based on forward identification technique. The proposed controller it tested in normal and load disturbance conditions. Kywords: Genitic fuzzy, Robot control, on line control, Model reference Control, Adaptive Fuzzy control.

Electromechanical Modeling of Piezoceramic Actuators for Dynamic Loading Applications

In most piezoelectric applications, including precision motion control, pressure regulation in micropumps, and force control in microactuators, there is a need to develop a model that accounts for hysteresis and describes both the electrical and mechanical properties of piezoceramics, along with the electromechanical coupling between the two domains. A model that characterizes hysteresis and the coupled electromechanical effect of the sensing and actuating signals is presented. The model presented characterizes the electromechanical properties of a piezoceramic actuator when subject to variable mechanical load disturbance conditions. The model is tested under a range of voltage excitations at frequencies up to 111Hz and is shown to offer high accuracy.

An add-on type fuzzy controller for control system retrofit

The present paper advocates the concept of a supervisory fuzzy controller. The proposed FLC algorithm employs a parallel architecture where an additional PD-type FLC can be employed either in conjunction with a conventional PID controller or a static fuzzy controller to improve system performance. The additional FLC implements a different rule base compared to a standard PD-type FLC, when employed alone. The effectiveness of the proposed scheme has been demonstrated by implementing it in simulation for two linear plant models of marine diesel engines and a nonlinear process plant. Its performance has been compared vis-` a-vis a standard PD-type FLC, employed in simulation, for the same processes. The system performance is evaluated under both transient and steady state load disturbance conditions and also under noisy measurement environment.

Control scheme for a universal power quality manager in a two-phase synchronous rotating frame

A universal power quality manager (UPQM) is presented. The active power balance of this UPQM is analysed. Based on the analysis a control scheme is established in a two-phase synchronous rotating dq-frame. In this control scheme the series active filter (AF) is controlled as a current source and makes the input current sinusoidal, while the shunt AF is controlled as a voltage source and it keeps the load voltage at the normal value. The performance of a UPQM with the proposed control scheme under different nonlinear load and source disturbance conditions is experimentally investigated.

Constraint feedforward control for thermal processing of quartz photomasks in microelectronics manufacturing

A feedforward control scheme is designed to improve performance of conductive heating systems used for lithography in microelectronics processing. It minimizes the loading effects induced by the common processing condition of placement of a quartz photomask at ambient temperature on a bake plate at processing temperature. The feedforward control strategy is a model-based method using linear programming to minimize the worst-case deviation from a nominal temperature set-point during the load disturbance condition. This results in a predictive controller that performs a pre-determined heating sequence prior to the arrival of the substrate as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. This procedure is based on an empirical model generated from data obtained during closed-loop operation. It is easy to design and implement for conventional thermal processing equipment. Experimental results are performed for two commercial bake plates and depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance.

PROCESSING OF SEMICONDUCTOR QUARTZ PHOTOMARKS ON BAKE-PLATES

A feedforward control scheme is designed for robust performance of conductive heating systems used for lithography in microelectronics processing. It minimizes the loading effects induced by the common processing condition of placement of a quartz photomask at ambient temperature on a large thermal-mass bake plate at processing temperature. The feedforward control strategy is a model-based method using linear programming to minimize the worst-case deviation from a nominal temperature set-point during the load disturbance condition. This results in a predictive controller that performs a pre-determined heating sequence prior to the arrival of the substrate as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. This procedure is based on an empirical model generated from data obtained during closed-loop operation. It is easy to design and implement for conventional thermal processing equipment. Experimental results are performed for a commercial bake plate and depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance.

Minimum time control of conductive heating systems for microelectronics processing

A minimum time control scheme is designed to improve repeatability by minimizing the loading effects induced by the common processing condition of placement of a semiconductor wafer at ambient temperature on a large thermal-mass bake plate at processing temperature. The minimum time control strategy provides an optimal solution for minimizing the worst case deviation from a nominal temperature set-point during the load disturbance condition. This results in a predictive controller that performs a predetermined heating sequence prior to the arrival of the wafer as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. The controller is easy to design and implement and makes it more suitable for online implementation such as automatic online tuning of a feedforward controller. Experimental results depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance.

Optimal predictive control with constraints for the processing of semiconductor wafers on bake plates

An optimal control scheme is designed to improve repeatability by minimizing the loading effects induced by the common processing condition of placement of a semiconductor wafer at ambient temperature on a large thermal-mass bake plate at processing temperature. The optimal control strategy is a model-based method using linear programming to minimize the worst-case deviation from a nominal temperature set point during the load disturbance condition. This results in a predictive controller that performs a predetermined heating sequence prior to the arrival of the wafer as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. This procedure is based on an empirical model generated from data obtained during closed-loop operation. It is easy to design and implement for conventional thermal processing equipment. Experimental results are performed for a commercial conventional bake plate and depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance.