Current limiter complicates the dynamic characteristics of servo motor

This chapter describes the sliding-mode control of permanent magnet synchronous motor (PMSM) servo systems. The typical structure of the systems consists of the position, velocity, and current control loops. The design of three controllers, position controller, speed controller, and current controller, and a filter in speed loop has been described respectively, aimed at reaching high-performances of PMSM servo systems, such as fast response, strong robustness, and high precision. The digitization of terminal sliding-mode (TSM) controllers of PMSM servo system has been discussed for the purpose of practical implementation.

Microgrid (MG) control in off-grid mode of operation is one of the main challenges in MGs. Under different loading conditions, voltage and frequency deviate from their nominal limits. The droop control method that applied with the current control and voltage control loops can restore the MG voltage and frequency to their nominal limits. However, it can’t regulate these parameters to their specified values. Additionally, the droop control method can’t do well when the system supplies either nonlinear or unbalanced loads. This paper proposes a control technique for adjusting the voltage and frequency of an MG in islanded mode under different loading conditions. The proposed method is based on applying the H-infinity ($$H\infty$$) robust control as a secondary controller with the droop control method to improve its performance. The proposed method is composed of four stages including; droop control loop, voltage control loop, current control loop and control loop for inductance–capacitance–inductance (LCL) filter and coupling circuit. $$H\infty$$ control has an internal model that can control the frequency and improve the system power quality by decreasing the disturbance frequencies. Moreover, it has two weighted parameters $$\xi$$ and $$\mu$$ that must be correctly adjusted to improve the stability of the system. For a proper adjusting of these parameters, the Harmony Search (HS) optimization method is applied. To prove the effectiveness and superiority of the proposed method, it is applied on a test system with three different loading scenarios using MATLAB/Simulink program. The results are compared with those of droop controller and they confirm that the proposed control method is more effective in controlling the microgrids under islanded mode operation.

This paper presented a vector controlled drives of permanent Magnet Synchronous Motor (PMSM) by using Proportional-Integral (PI) Speed controller based dSPACE implementation. The concept of vector control is applied to PMSM to obtain linear dynamics similar to that of a DC motor. The model consist of two control loops, hysteresis current controller is used for inner loop current control and PI controller for outer loop speed control. PI speed controller selected due to simplicity compare to fuzzy, neutral etc. to make sure dSPACE DS1103 successfully implemented. The PMSM vector control algorithm for a theoretical basic has been verified by experimental results and created a rapid control prototype environment by using MATLAB/ Simulink and the DS1103 DSP of dSPACE.

Two-motor application has become a very attractive filed in important field which high performance is permitted to achieve of position, speed, and acceleration. In the elevation axis of telescope control system, two-motor direct drive is proposed to enhance the high performance of tracking control system. Although there are several dominant strengths such as low size of motors and high torsional structural dynamics, the synchronization control of two motors is a very difficult and important. In this paper, a multi-loop control technique base master-slave current control is used to synchronize two motors, including current control loop, speed control loop and position control loop. First, the direct drive function of two motors is modeled. Compared of single motor direct control system, the resonance frequency of two motor control systems is same; while the anti-resonance frequency of two motors control system is 1.414 times than those of sing motor system. Because of rigid coupling for direct drive, the speed of two motor of the system is same, and the synchronization of torque for motors is critical. The current master-slave control technique is effective to synchronize the torque, which the current loop of the master motors is tracked the other slave motor. The speed feedback into the input of current loop of the master motors. The experiments test the performance of the two motors drive system. The random tracking error is 0.0119" for the line trajectory of 0.01°/s.

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.

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.

<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>

In the transmission process of gear system, the change of load will make the system in different states of motion, which affects the transmission efficiency of gear system. It is important to investigate the nonlinear dynamic characteristics of gear system under different load states. Using straight cylindrical gears as the object of study, the concentrated mass method is used to establish a dynamic model that takes into account nonlinear factors such as tooth side clearance, time-varying meshing stiffness and transmission errors. The differential equations of the system are solved by the Longe-Kutta method to obtain the bifurcation diagram, the maximum Lyapunov exponent diagram and the phase plane diagram of the gear system to analyze the effect of the meshing damping ratio on the dynamic characteristics of the system under different load states. The results show that the influence of the engagement damping ratio on the dynamic characteristics of the system is greater under light load conditions, showing different states of motion as the engagement damping ratio gradually increases. Under heavy load conditions, the effect of the engagement damping ratio on the dynamic characteristics of the system is small. Appropriately increasing the mesh damping ratio is beneficial to the gear system to avoid the chaotic zone and maintain a stable cyclic motion state. The results of the study provide a reference for the design of gear systems with variable loads.

Experimental study on thermal dynamic characteristics of gear transmission system

A comparison of fuzzy self‐tuning (FST), sliding mode control (SMC) and conventional proportional–integral (PI) control methods is performed under unbalanced grid conditions using a bridgeless power factor correction (PFC) converter. The bridgeless PFC converter operates the correction of AC line current to obtain a DC output voltage without full bridge rectifier based on these control methods. These control methods generate the duty cycles to provide higher unity power factor and lower total harmonic distortion of input current, even if AC line voltage is distorted. This study focuses on the performance analysis of FST and SMC methods adaptation to the input current for the bridgeless PFC converter and comparing with the conventional PI controller. Although the SMC method is only used in the current control loop, the FST method is used in both current and voltage control loops for eliminating harmonics of input current and regulating of output voltage. The performance of control methods is evaluated with a TMS320F2812 digital signal processor. The simulation and experimental results are compatible with the limits for harmonic current emissions, IEC 61000‐3‐2 and show that the FST and SMC are better than the conventional PI control method and FST is superior to the SMC.

A novel algorithm is proposed to identify the parameters of a synchronous dual-drive ball screw gantry system in this paper. The modeling of the gantry system is described in this paper, and dynamic equations are used to derive the relationship from the motor to the coupling mechanism. The modeling results are used to design the algorithm used to identify the model parameters. The proposed algorithm uses two disturbance observers (DOB) to identify the parameters for the coupling mechanism and sliding stages. The sinusoidal position and velocity commands for the proposed identification algorithm are relatively smooth to avoid damaging the mechanism. The proposed method is easy to implement in the position control loop and velocity control loop. Finally, simulation and experimental results show that the proposed DOBs can accurately estimate the parameters for a gantry system, and the estimated results can be further used to design a corresponding controller for the gantry stage.

The proposed topology is used to connect a single-phase and a three-phase renewable energy resources to the grid. The single-phase source is coupled to a single-phase PFC boost converter, which enhances the input PF utilizing two feedback loops: outer voltage loop control and inner current loop control. The basic hightlight is to study the PFC converter in microgrid application where renewables are integrated with the systems. The basic aim is to observe the overall performance of the converters with various disturbances such as load variations, etc. Here, the single-phase and three-phase stand-alone inverter is used to get the the output of the PFC boost converters. A symmetrical sinusoidal output voltage waveform should be produced and maintained by the inverter. The three-phase source is also coupled to a PFC buck converter, which enhances the input PF utilizing two feedback loops: outer voltage loop control and inner current loop control. The single-phase stand-alone inverter receives the output of the PFC buck converter. The transformer receives the outputs of both the inverters as it is a multi-winding high-frequency transformer and offers isolation between the grid and the source. The pulses for the switches in the single-phase inverter coupled stand-alone system were generated using a sinusoidal pulse width modulation approach. Both the PI controllers are implemented to maintain the regulations. The simulation results are achieved by varying the load, maintaining a constant voltage, and observing whether the current varies as the load changes. It also provides the efficacy of the study.

The paper design a current control based active power filter (APF) for improving power quality by reactive power compensation and harmonic filtering. The designed APF is based on a voltage source inverter (VSI), where the VSI is controlled by two loops, the voltage control loop and the current control loop. The voltage control loop is used to regulate the DC link capacitor voltage of the VSI. Via triangular wave control, the current control loop is used to produce a tracking PWM signal to shape the harmonic current such that it is in-phase with the same shape as the input voltage. The major advantage of the proposed APF is to search the reference current for improving power quality by using dq0 detecting method. Simulation results are given to validate the proposed scheme. From the results, it shows that the reduction of %THD is better in power system networks.

Voltage source converters (VSCs) have emerged as the key components in modern power systems, facilitating efficient energy conversion and flexible power flow control. Understanding the fundamental circuit model of VSCs is essential for their accurate modeling and analysis in power system studies. A basic voltage source converter circuit model connected to an LC filter is essential because it lowers the harmonic distortions and enhances the overall power quality of the micro-grid. This guarantees a clean and steady power supply, which is necessary for the integration of multiple renewable energy sources and sensitive loads. A comprehensive methodology for developing a basic circuit model of VSCs, focusing on the key components and principals involved, is presented in this paper. The methodology includes the modeling of space vector pulse-width modulation (SVPWM) as well as the direct quadrature zero synchronous reference frame. Different design controls, including the design of current control loop in the S-domain, the design of the direct current (DC) bus voltage control loop in the S-domain, and the design of the alternating current (AC) voltage control loop in the S-domain, are explored to capture the dynamic behavior and control strategies of VSCs accurately. The proposed methodology provides a systematic framework for modeling VSCs, enabling engineers and researchers to analyze their performance and assess their impact on power system stability and operation. Future studies can be conducted by using case studies and simulation scenarios to show the efficiency and applicability of the developed models in analyzing VSC-based power electronics applications, including high-voltage direct current (HVDC) transmission systems and flexible alternating current transmission systems (FACTS). The significance of this work lies in its potential to advance the understanding and application of VSCs, contributing to more resilient and efficient power systems. By providing a solid foundation for future research and development, this study supports the ongoing integration of renewable energy sources and the advancement of modern electrical infrastructure.

This paper develops the impedance models of grid-connected converters under the virtual synchronous generator (VSG) strategy with a cascaded inner control loop and analyzes the system stability of VSG controlled converters with different kinds of weak grid. Different from existing small-signal models with high dimensions, a single-in-single-out (SISO) impedance model with simple mathematical expression is obtained in this paper, which is applied to identify the influence of the cascaded control loop on impedance characteristics and system stability. It is found that the impedance characteristics of VSG controlled converters can become capacitive below the fundamental frequency, and it is mainly caused by the voltage controller in the cascaded control loop of the VSG strategy. Impedance-based stability analysis shows that the capacitive impedance characteristics can benefit the compatibility of converters operated with the series-compensated weak grid, but may deteriorate the system stability with the inductive weak grid, which can be avoided by increasing the proportional coefficients of the cascaded voltage and current controllers or applying a larger virtual resistor to reduce the negative resistance in the capacitive frequency range. Experiments based on the control-hardware-in-loop (CHIL) platform were carried out to verify the developed analytical models and possible system instable cases.