Good Steady-state Performance Research Articles

Frequency-Adaptive Modified Comb-Filter-Based Phase-Locked Loop for a Doubly-Fed Adjustable-Speed Pumped-Storage Hydropower Plant under Distorted Grid Conditions

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-storage hydropower experimental platform.

PMSM Sensorless Control by Injecting HF Pulsating Carrier Signal Into ABC Frame

Spatial-saliency-tracking-based high-frequency (HF) pulsating carrier injection method is widely employed in permanent-magnet synchronous machines sensorless control. In order to avoid the problems of long convergence time, potential start-up failure and limited system stability existing in tracking observers, a strategy to inject three HF pulsating voltages with different frequencies and amplitudes into ABC frame is proposed in this paper. With the proposed method, three frequency components in the response current signals are demodulated and then combined together to calculate the rotor position directly. Different from the conventional method, the proposed solution utilizes both d- and q-axis carrier current instead of only the q-axis carrier current to enhance the acquisition of the rotor position information. Meanwhile, a new signal processing strategy is developed to completely eliminate the effects of system delay. Furthermore, the compensation of cross-saturation effect is deduced in detail to improve the accuracy of rotor position estimation. In addition, magnetic polarity detection is implemented with the same proposed solution by demodulating the second harmonic components from the response current signals, which simplifies the magnetic polarity process. Finally, the experimental results demonstrate that the proposed strategy can obtain an accurate rotor position with good steady-state and dynamic performance.

Continuous‐time model predictive control of a permanent magnet synchronous motor drive with disturbance decoupling

The design and the experimental validation of a continuous-time model predictive control (CTMPC) for a permanent magnet synchronous motor (PMSM) drive with disturbance decoupling is discussed. The CTMPC approach uses Taylor series expansion to derive a closed-form solution to the problem of model predictive control even though the system behaviour is described by a non-linear model. This type of controller requires an exact knowledge of the system model to guarantee an accurate prediction of the system behaviour, while the PMSM is usually subjected to model uncertainties and external disturbances such as the load torque. Moreover, in the proposed approach, the predicted speed tracking error is directly used to determine the required voltage command without the need for a cascaded control scheme. As a result, the load torque is seen as unmatched disturbance which makes exact disturbance decoupling more challenging. To overcome such a problem, a non-linear disturbance observer is designed and combined with the CTMPC method to enhance the prediction accuracy under parameter variation and unknown load torque. The feasibility of the proposed approach is experimentally investigated, and good transient and steady-state performances are obtained.

Hybrid Fuzzy PI Speed Controller for Brushless DC Motor Drives

List of issues // // In future, Electric vehicles (EV) are trend setters for transportation with zero greenhouse gas emission and higher efficiency. In EV applications, Brushless DC motors (BLDCM) are most predominantly used. Here, a Hybrid Fuzzy PI controller is intended for effective speed regulation of BLDCM. In general, Fuzzy logic controllers (FLC) provide better transient performance and results steady state error. The PI speed controller gives good steady state performance but poor transient performance. For getting an excellent performance, the referred Hybrid fuzzy PI controller combines the merits of the above two controllers. Also, this paper presents relative study among PI,FLC and Hybrid Fuzzy PI controller for a BLDCM. In Matlab/Simulink environment, the BLDCM with proposed controller is designed and simulated. Results prove the predominance of intended Hybrid Fuzzy PI for BLDC motors.

Research on vane end face of cam-rotor vane servo motor based on disturbing torque

Cam-rotor vane motor (CRVM) is one of the new continuous hydraulic servo motors with the characteristics of no pulsation of instantaneous flow rate and output torque, small volume and rotating inertia. It is one of the appropriate actuators for hydraulic servo system which has good dynamic and steady-state performance requirements. The ideal output torque of CRVM is pulseless, but the actual output torque of CRVM is pulsating. This is caused by the disturbing torque of contact components, especially the friction between vane and cam-rotor. In order to get better performance of CRVM, which means more stable output torque and smaller disturbing torque, we discuss four kinds of vane end faces (VEFs). Analytic formulae of the normal contact force and the disturbing torque caused by the vane are derived from systematical force analysis. The normal contact force and the disturbing torque vary through a period under different VEF, and the reduced oil pressure is simulated in this paper. The simulation shows that the VEF with the proper round and reduced oil pressure can significantly decrease the disturbing torque and get better servo performance. The experiment results verify the correctness of the theoretical analysis and simulation.

A Neutral-Point Voltage Balance Controller for the Equivalent SVPWM Strategy of NPC Three-Level Inverters

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

PMSM Sensorless Control by Injecting HF Pulsating Carrier Signal Into Estimated Fixed-Frequency Rotating Reference Frame

For permanent-magnet synchronous machines (PMSMs) sensorless control, the widely employed high-frequency (HF) pulsating carrier signal injection method is based on tracking the rotor saliency. It may face the problems of long convergence time, potential start-up failure, and limited system stability. Different from the conventional schemes, the proposed strategy is a direct estimation method. In which, a HF pulsating carrier voltage is injected into the estimated fixed-frequency rotating reference frame other than the estimated synchronous reference frame (SRF). With this approach, spatial saliency tracking observer, which is necessary in the conventional sensorless control, is removed to simplify the control structure and improve the system stability. Furthermore, the rotor position information is directly obtained from the response of injected HF pulsating carrier signal, which can avoid potential convergence failure of tracking observer. In addition, the compensation of system delays existing in the proposed sensorless control strategy is deduced to improve the accuracy of rotor position estimation. For magnetic polarity detection, a new method which has the advantages of high signal-to-noise ratio and low vibration is also investigated. Finally, the experimental results on a PMSM indicate that the rotor position with good steady state and dynamic performance can be obtained accurately with the proposed sensorless control strategy.

Robust attitude control design for a low-cost hexarotor micro aerial vehicle

This article proposes a new practical robust attitude state feedback controller of a low-cost hexarotor micro aerial vehicle under the effects of noise in angular velocity measurements and multiple uncertainties (called the equivalent disturbance), which consist of external time-varying wind disturbance, nonlinear dynamics, coupling and parametric uncertainties. The proposed method is designed in two simple steps. Firstly, a nominal cascade controller is designed to reduce noise in angular velocity measurements and to achieve good attitude tracking performance in nominal conditions. Then, a second-order robust compensator is integrated into the closed-loop system to reduce the effects of the equivalent disturbance. The proposed control design is a linear time-invariant controller which is easily implemented in practical applications. Compared to other advanced attitude controllers, the proposed controller incurs lower computational costs and can easily be implemented in a low-cost embedded microcontroller system. In addition, a practical computational design procedure and an intuitive online tuning method for the proposed controller are presented in this article in order to provide a complete reference to micro aerial vehicle developers. The simulation and experimental results are presented to demonstrate the robustness of the proposed controller in operation in outdoor environments, to show good steady-state and dynamic tracking performance of the closed-loop system and to prove that the tracking errors are ultimately bounded within desired limits.

Flexible active compensation based on load conformity factors applied to non‐sinusoidal and asymmetrical voltage conditions

This study proposes a flexible active power filter (APF) controller operating selectively to satisfy a set of desired load performance indices defined at the source side. The definition of such indices, and of the corresponding current references, is based on the orthogonal instantaneous current decomposition and conformity factors provided by the conservative power theory. This flexible approach can be applied to single- or three-phase APFs or other grid-tied converters, as those interfacing distributed generators in smart grids. The current controller is based on a modified hybrid P-type iterative learning controller which has shown good steady-state and dynamic performances. To validate the proposed approach, a three-phase four-wire APF connected to a non-linear and unbalanced load has been considered. Experimental results have been generated under ideal and non-ideal voltage sources, showing the effectiveness of the proposed flexible compensation scheme, even for weak grid scenarios.

Hybrid observer for improved transient performance of a marine vessel in dynamic positioning

Abstract: Dynamic positioning (DP) systems are used on marine vessels for automatic station keeping and tracking operations solely by use of thrusters. Observers are key components of DP systems, and two main types are proposed in this paper. The model-based type is used in steady state conditions since it is especially good at filtering out first order wave induced motions and predicting states in the case of signal loss, and the signal-based type typically has superior performance during transients. In this paper a hybrid observer including a signal-based part and a model-based part with a performance monitoring function is proposed. The observer part that provides the best estimate of the vessel position and heading is used in closed-loop control, thereby allowing for improved transient response while maintaining good steady-state performance. The contributions of this paper include the design of a hybrid signal-based and model-based observer with performance monitoring, stability analysis of the vessel with hybrid estimates in output feedback control, and simulations of a platform supply vessel during a set point and heading change.

Variable Modulation Offset SPWM Control to Balance the Neutral-Point Voltage for Three-Level Inverters

In order to solve the neutral-point voltage unbalancing problem for three-level inverters, this paper proposes a method to balance the neutral-point voltage for three-level inverters with variable modulation wave offset sinusoidal pulse-width modulation (SPWM) control. Based on the mathematical expressions of neutral-point voltage unbalancing, the factors are studied, which affect the fluctuation of neutral-point voltage. Theoretically the mathematical expressions of the neutral-point voltage with the proposed method are derived, and the mathematical relationship between the fluctuation of neutral-point voltage and the adjusting offset of modulation wave is studied. This proposed method realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the modulation wave based on SPWM (DCOSPWM). This DCOSPWM method is very simple, which has good steady-state performance and is easy for digital implementation. The simulation results verify the correctness of the theoretical analysis in this paper, and the feasibility and effectiveness of this method is verified by the experiments in the experimental platform of neutral point clamped three-level inverters based on digital signal processor (DSP)-complex programmable logic device (CPLD).

EXPERIMENTAL VERIFICATION OF A PRACTICAL DIGITAL DRIVER WITH SWITCHED GAIN-TUNING FOR FIVE-PHASE STEPPING-MOTORS

A digital driver that has a switched self-tuning gain in its current regulator is designed for five-phase stepping motors so that their performance could be improved and adjusted more easily, than with an analog driver. The regulator has a fixed gain block in its feedback loop and an adjustable gain in the feedforward path, replacing the integrator and the high gain that were required in previous designs to achieve good steady-state performance and fast response. Extensive experiments have been conducted under typical and extreme actuation conditions, and revealed that the proposed driver performs better than the analog drivers or their discretized equivalents, especially in eliminating undershoots, which were problematic with previous drivers.

Quaternion-Based Robust Attitude Control for Uncertain Robotic Quadrotors

A robust nonlinear attitude control method is proposed for uncertain robotic quadrotors. The proposed controller is developed based on a nonlinear model with the quaternion representation and subject to parameter uncertainties, nonlinearities, and external disturbances. A new state feedback controller is proposed to restrain the effects of nonlinearities and uncertainties on the closed-loop control system. These uncertainties are considered as input equivalent disturbances and their effects are guaranteed to be attenuated. Experimental results are given to show good steady-state and dynamic tracking performance of the closed-loop system by the proposed robust control method compared with other nonlinear control methods.

Parameter Plane Synthesis and Performance Investigation of a Three-Phase Three-Level Bidirectional Rectifier

Abstract In this paper, parameter plane synthesis of a three-phase neutral-point clamped bidirectional rectifier has been performed. The converter involves one outer-loop PI voltage controller and two inner-loop PI current controllers for the closed-loop control. D-partition technique has been employed for the precise design of the voltage controller. An experimental prototype of the converter has been developed, and the experimental investigation of the converter performance in closed loop has been carried out. DSP DS1104 of dSPACE has been used for real-time implementation of the designed controller. The converter gives a very good performance in steady state and dynamic state (for rectification as well as inversion modes of operation) using the designed controller parameters.

Low-Complexity Model Predictive Power Control: Double-Vector-Based Approach

Conventional model predictive power control (MPPC) achieves good steady-state performance and quick dynamic response by minimizing a cost function relating to the power errors. However, applying single voltage vector during the whole control period fails to reduce the power ripples to a minimal value; particularly in the two-level converter with limited switching states. Recently, the concept of duty cycle control has been introduced in MPPC to achieve further power ripple reduction. Although better steady-state performance is obtained, a lot of calculations are needed when deciding the best voltage vector and its corresponding duration. This paper proposes a low-complexity MPPC with quick voltage selection and fast duty cycle calculation. Different from prior MPPC, the negative conjugate of complex power in synchronous frame is selected as the control variable. As a result, only one prediction is required to select the best voltage vector, and its duration is determined base on the principle of error minimization of both active and reactive power. Further study reveals that the proposed low-complexity MPPC is equivalent to the recently reported MPPC with duty cycle control. Simulation and experimental results obtained from a two-level three-phase ac/dc converter are presented to confirm the theoretical study and the effectiveness of the proposed method.

Modeling and Simulation of PMSM Double-Loop Control System Based on Matlab/Simulink

A double-loop control system simulation model is created in Matlab/Simulink based on mathematical model of PMSM, as well, the structures and properties of each functional module are introduced in detail. The simulation results prove that the model was effective and it had good steady-state and dynamic tracking performance. Finally, experiments were carried out to prove the validity of the simulation model in the development of practical engineering.This model provides an effective auxiliary method for theoretical analysis and engineering design of PMSM double-loop control system.

PSO Tuned PID-Based Model Reference Adaptive Controller for Coupled Tank System

In process industries control of nonlinear processes like level process is a common problem. For these nonlinear processes, to have a good performance even in the presence of environmental changes, the controller must have the ability to adopt changes in plant dynamics. So a Model Reference Adaptive Control (MRAC) based on PID controller is designed. Main objective of this work is to design PID-MRAC to include adaptiveness and to give good steady-state and transient performance for coupled tank system both with interaction and without interaction. A Particle Swarm Optimization (PSO) algorithm is used to fine tune the PID controller parameters. Simulations are done to show the effective performance of PID-MRAC compared to simple MRAC applied to couple tank system.

Single and three phase moving average filter PLLs: Digital controller design recipe

This work proposes a simple and easy to use design recipe for the proportional–integral digital controller of a Phase Locked Loop using moving average filter and multiplier type phase detector. Based on fast controllers predesigned in this paper for the most common situations (50/60Hz grid frequency, single and three-phase systems, presence of odd and/or even harmonics) the new proportional–integral controller parameters are obtained using analytical formulas for new operation conditions (input amplitude and sampling frequency). The new controller parameters obtained using this method avoids trial and error procedures and keeps the same PLL transient and steady state performance of the original design. Simulation and experimental results validate the proposed design recipe. Comparison with recent results in the literature confirms that the proposed design recipe method provides faster transient response and good steady state performance.

Novel Sensorless Control Strategy With Injection of High-Frequency Pulsating Carrier Signal Into Stationary Reference Frame

In this paper, a novel sensorless control strategy with the injection of a high-frequency pulsating carrier signal into a stationary reference frame is proposed. Differing from the two most commonly used conventional high-frequency carrier signal injection methods, i.e., the injection of a rotating carrier voltage into a stationary reference frame and the injection of a pulsating carrier voltage into an estimated synchronous reference frame, the new proposed strategy injects a pulsating high-frequency carrier voltage into a stationary reference frame, which is as stable as the rotating carrier signal injection method. Then, the rotor position information can be retrieved from the carrier current response that is amplitude-modulated by the machine saliency, which is as simple as the pulsating carrier signal injection method. The signal demodulation process, the compensation of the cross-saturation effect, and magnetic polarity detection are also discussed and analyzed in detail. The experimental results on an interior permanent-magnet synchronous machine demonstrate that the new proposed strategy has a robust magnetic polarity detection and that it can achieve an accurate rotor position estimation with good steady-state performance and dynamic performance.

Design and Simulation Analysis on Self-Tuning Fuzzy Controller Based on Scaling Factor and Quantitative Factor

Along with the development of modern science and technology information, fuzzy control theory based on its unique advantage becomes more and more popular with scientists and engineers, therefore it is quickly applied to all walks of life, and is one of the advanced teaching theory introduced in educational industry. Firstly, on the basis of mapping between classical set and fuzzy set, the paper comprehensively analyzes the intelligent fuzzy control theory. Based on the improved fuzzy controller which is self-correcting through scale factor and quantification factor, we establishes the fuzzy control model of moral education. In order to verify the feasibility of the model, we design the fuzzy controller to carry out the applied simulation by using the MATLAB fuzzy logic toolbox, and the results show that the system has fast response, strong adaptability, and good steady-state performance.