Two-motor direct drive control for elevation axis of telescope

This paper looks at design of a controller for an induction motor electrical drive useful for high speed railway applications. The design of the controller is based on the cascade control mode using the standard model of the motor referred to d-q axes fixed with the rotor flux vector. It is assumed that the speed and the rotor flux are the variables to be controlled and their dynamics must be decoupled, which is accomplished by means of a nonlinear compensator, which gives decoupling of the direct and in-quadrature currents. According to the aforementioned cascade control mode, the bandwidth of the current inner control loops must be selected higher than that of the speed and rotor flux outer control loops. To take into consideration the remarkable uncertainties in the knowledge of the inertia coefficient, adaptive control techniques are used to design the speed control loop. To cope with uncertainties in electromagnetic parameters, robust control techniques are used for designing the rotor flux, the direct, and the in-quadrature current loops. Simulation experiments are displayed to test the entire controller.

Direct current control has been used in many voltage source power converters connected to utility grid, such as Static Var Generators (SVGs) and parallel Active Power Filters (APFs). In their stationary coordinates control systems, there are usually two closed control loops. One is the current loop and the other is the voltage loop. In practical applications, because the voltage source converters are connected to the grid, the output current will be affected and very often a command-tracking error exists in the current control loop. In this paper, a detailed analysis and design considerations are carried out to investigate this command-tracking error caused by the source voltage. Based on the obtained current loop transfer function and block diagram of the system, analytical expressions of the current control error are derived. The variables that affect the current control errors are then identified. The relationship between the circuit/control parameters and the current control errors are extensively explored. The command-tracking error affects the peak value of the modulation wave. When we design a fully digital control system, the peak value of the modulation wave is smaller than the peak value of the carrier wave. Then, according to choosing the values of the variables that affect the command-tracking error, the methods to design a fully digital direct current controlled voltage source converters connected to the grid are presented. The computer simulation investigations and hardware experimental results verify the analysis and design considerations.

Distributed generators based on wind and solar energy will give prominent momentum in near future [1]. A microgrid consists of group of loads and distributed generators that operate as a single controllable system. The microgrid concept introduces hybrid AC/DC microgrid which reduces multiple reverse conversions in an individual AC or DC grid. This project aims at providing a reliable control system for integrating small renewable power generating units with main grid. The control system designed in this work consist of inner current loop and outer voltage control loop collectively known as Multiloop current voltage PI control system. In this work the performance of the hybrid AC/DC microgrid is analysed by using this control system along with d-q Transformation. This method is implemented for the converters to properly co-ordinate the AC sub-grid and DC sub-grid. The circuits with the proposed method are modeled and simulated by using the MATLAB/ SIMULINK. The results show that with this technique, phase and frequency of the converters are synchronised with that of the utility grid. Hence the reactive power in the transmission line is reduced‥ As the reactive power is reduced, we obtain a stabilized output power which is transmitted to the loads and utility grid by using the above proposed method.

This paper analyzes the input admittance/impedance characteristics of a permanent-magnet brushless AC motor drive system, taking account of the influence of both current and speed control loops as well as the motor and inverter losses. It is shown that, if voltage feedforward compensation is not employed, the input admittance of the drive system differs significantly from that of an ideal constant power load, and is influenced by the speed and current control loop bandwidths. It is also shown that, when the drive is connected to a DC supply via an LRC filter, the magnitude of the input admittance at the filter resonant frequency has a crucial effect on system stability margin.

Current limiter complicates the dynamic characteristics of servo motor

<div class="htmlview paragraph">A disk brake clamp force controller for electromechanical brakes (EMB) in automotive brake-by-wire systems may be obtained from a standard motion control architecture with cascaded position, speed and current control loops by replacing the outer position control loop with a force control loop. When implemented with proportional, integral and differential (PID) controllers this architecture generally performs well for standard motion control problems, but the EMB control problem is differentiated by a large operating range in which non-linear load disturbances such as friction become significant at high clamp forces of up to 30kN. This paper investigates the feasibility of a cascaded PI control architecture for an EMB with the intention of establishing a baseline standard against which the performance of future control schemes may be compared. Simulation results are presented based on an accepted EMB model.</div>

With more than three phases, multi-phase induction machines provide an alluring substitute for lowering the strains placed on the machine's switches and windings. The management of overly produced current is one of the most important issues when making quick and significant adjustments to the speed control of a multi-phase induction motor. Thus, if the speed controller lacks an output amplitude limitation, it may cause harm to both the motor and the power electronics converter. The speed control loop and the two internal current control loops are the first two areas in which this research suggests using polynomial predictive controllers to solve the saturation phenomena of the speed regulator. Then, by convexly optimizing the Youla parameter while accounting for time and frequency constraints, the external predictive speed controller is readjusted. This ensures that the speed response to the reference stays in an imposed model with minimal current control during transient periods, while also preserving the closed-loop functionalities that the initial predictive controller had achieved. The results of the simulation demonstrate how well the suggested control system controls speed under different multi-phase induction machine operating situations.

In this research, the performance of the brushless doubly fed induction generator (BDFIG) based wind turbine is studied under sudden disturbances, which occur as a result of the secondary loads change which connected in the terminals of wind turbine and wind speed change. The simulation has been executed at different loads. This paper presents also a simulation for simple control scheme of the BDFIG driven by wind turbine is controlled at unity power factor. The control scheme is designed to keep the voltage constant at (1p.u) value due to sudden change of loads and wind speed. the control system is implemented with PI controller to control the back-to-back converters utilized in the control winding circuit of the BDFIG wind turbine. Two current control loops are designed for regulating control winding current components( icd-icq). The d-axis reference current is estimated using the reactive power control loop to operate at unity power factor and keep the voltage constant at 1p.u value. The q- axis reference current is estimated using the speed control loop. The parameters of PI controllers are calculated by using Ant Colony Optimization (ACO)method. The performance of proposed PI controller is examined through MATLAB simulation of the overall wind energy conversion system using BDFIG and the system is subjected to different disturbances in terms of load and wind speed variation. The simulation results validate the effectiveness and powerful of the control system in sense of less overshoot and fast response.

Augmenting effectiveness of control loops of a PMSG (permanent magnet synchronous generator) based wind energy conversion system by a virtually adaptive PI (proportional integral) controller

The article is dedicated to optimizing the digital current control loop of a thyristor converter-driven electric drive, essential for ensuring stable, precise, and reliable operation of electric drives in automated and industrial systems. The primary goal of this research is to develop and enhance the digital current regulator (DCR), which enables the drive system to achieve desired performance, including rapid and stable response to current changes without excessive overshoot or oscillations. Optimization of the current loop improves energy efficiency, enhances dynamic properties, and increases resistance to external disturbances, all of which are critical for modern electric drive systems. The introduction discusses key aspects of digital current loop optimization, specifically dynamic characteristics such as time delays, sampling rate, and bandwidth, which significantly impact the efficiency of digital controllers. Special attention is given to the tuning of proportional-integral (PI) controller parameters, allowing quick and stable response to current changes. The developed model allows preliminary simulation of the current loop’s performance, providing an opportunity to test different configurations before actual implementation. To improve the accuracy and stability of the system, filtering methods are proposed to reduce the impact of high-frequency noise, ensuring the system’s precision and robustness against external interference. Optimization criteria are introduced, including minimizing the integral square error (ISE) and reducing energy consumption, which significantly decreases system losses and increases the energy efficiency of electric drives. In developing the optimized control loop, the following assumptions are considered: 1) the thyristor converter (TC) operates in continuous current mode, 2) the current loop dynamics are studied within a narrow range of TC phase angle changes, and 3) a discrete dynamic TC model is used with averaging of electromotive force (EMF) over the conduction interval. Optimizing the digital current loop addresses several critical tasks, including enhancing control accuracy, reducing overshoot and oscillations, and improving the system’s dynamic response, allowing for reduced delays and a faster reaction to load changes. The optimization results of the digital current regulator (DCR) show reduced energy consumption and significant improvements in control accuracy. The high-speed performance of the digital current loop enables fast transient processes within a single sampling interval of the thyristor converter, which is crucial for systems requiring rapid regulation. Additionally, the digital control loop provides flexibility in control, as it allows for system adjustments to different operating conditions through a software-based approach. The study’s final results demonstrate the potential of digital current loops in modern electric drives. With advances in microprocessor technology, digital regulators enable more complex control algorithms, including adaptive and predictive strategies, which further enhance system efficiency. These approaches are especially relevant for industrial electric drives that require high precision and response speed, making digital current loops a promising solution for contemporary automated control systems.

This paper proposed a method which was based on DSP and FPGA and applied in the fully digital and high-performance permanent magnet synchronous motor (PMSM) AC servo system. In the system, the position loop control combined PI control and feedforward control was implemented by DSP unit, while the speed loop and current loop control were implemented by FPGA unit. Since FPGA provided a kind of hardware design scheme for the control system, it had the features of a special control IC. The functions of vector control algorithm, velocity and current sampling, space vector pulse width modulation and PI algorithm were included in the special control IC. In the meanwhile, it also provided host communication interfaces that could realize the real-time modification of the control parameters in the IC. Finally, the experimental results indicate that this system has high-speed response and well static state control performance.

This paper proposes a comparison study focusing on the dynamic response and tracking accuracy for the induction motor drive system influenced by the controller design methods. Pole-zero cancellation (PZC) and pole placement (PP) methods are commonly used to define the controller gains for motor drive systems, and both methods are verified in this paper. The bandwidth of controllers for both methods is set equally based on the field-oriented control strategy, which consists of current and speed control loops. Furthermore, the test conditions are defined to examine the drive system performance, i.e., i) load torque rapidly changes with the maintained speed and ii) speed changes in no-load and with-load torque conditions to validate the current and speed control loops, respectively. The validation of the drive system performance influenced by the controller design methods is demonstrated by simulation results.

As a single controllable unit, microgrid can be grid-connected with utility grid and detached from grid to become a controllable autonomous system. When microgrid is switching between grid-connected mode and islanding mode, it will cause fluctuation of voltage, current and frequency, which will have a certain impact on the load. The stable control in both modes is the basic condition to ensure the reliable operation of microgrid. In this paper, control strategy of grid-connected and islanding mode switching based on the master-slave structure of microgrid system is mainly researched. The proposed method of PQ outer loop controller, V/f outer loop controller and current inner loop controller of the master inverter of microgrid is given. Based on the analysis of the structure of the controller, a mathematic model of the master inverter of the microgrid is established, and a current inner loop controller based on the LADRC (Linear Active Disturbance Rejection Control) technique is designed. The presented smooth switching control strategy makes the outer loop controller running in parallel, and the inner loop controller share the improved current inner loop controller. LADRC control structure has strong anti-interference ability, it can effectively inhibit the fluctuations of various parameters, has a good inhibitory effect on the uncertainty of the power grid. The design method is simple and feasible. The simulation results show that the switching range of voltage, current and frequency is small, and the switching process time is less than 20ms, which can achieve stable and smooth switching between microgrid and utility grid.

By adapting the forward converter range of switching regulators to include an additional current-controlled feedback loop, derived from either the secondary or primary power circuit, an improvement in the closed-loop performance of the switching regulator can be obtained. The basic analysis work examines the simple single-ended forward converter, with d.c. plus a.c. current control, derived from the secondary power circuit. An additional fixed voltage ramp is also included in the control loop to provide `feedforward? compensation for input voltage disturbances, and also to extend the maximum duty cycle from 50% up to 100%. Using this circuit configuration a simple small signal equivalent circuit for the current-controlled switching regulator can be obtained, enabling the performance of practical designs to be predicted. Practical implementation of the current mode control technique using a standard large-scale integrated circuit together with a number of applications is also given.

In voltage‐controlled voltage source inverters (VSIs)‐based microgrids (MGs), the inner control is of prime interest task for guaranteeing safe and stable operation. In this paper, an in‐depth investigation of the modelling, control design, and analysis of the voltage and current inner control loops intended for single‐phase voltage‐controlled VSIs is established. The main objective of this work is to provide a comprehensive study of the mathematical modelling, control design, and performance evaluation of the inner control's loops considering different proportional‐integral (PI) controller types with and without compensation, and to determine the optimal scheme that can offer better performance in terms of implementation simplicity, robustness, and transient and steady‐state responses. Thus, the mathematical closed‐loop models of designed outer voltage and inner current control schemes based on PI, P, and feedforward controllers with and without compensation are, first, derived. Following this, a systematic and effective control design for tuning the different PI controllers’ parameters is proposed. Furthermore, an analysis revealing the performance of the designed voltage and current control schemes is provided. This analysis enables us to choose a P controller and PI feedforward controller for the current control loop and the voltage control loop, respectively. The chosen P and PI controllers should be simple; meanwhile, they should offer a wide bandwidth. A simulation study is carried out in MATLAB/Simulink software to assess the performance of the adopted inner control scheme for both linear and non‐linear loads. In addition, an experimental setup, based on a TMS320F2837xD μ C, of a single‐phase VSI supplying linear and non‐linear loads is built to verify the effectiveness and the robustness of the adopted inner controller. The results demonstrated: (1) the necessity of introducing the compensation term, which is responsible for offering control improvement against voltage perturbation, (2) the high tracking performance of the chosen controller in terms of dynamic and steady‐state responses as well as its simplicity of implementation.