Compensation Control Method Research Articles

An Improved Virtual Impedance Control Based Oscillation Suppression Method for MMC DC System

The oscillation phenomenon has detrimental effects on the stable operation of the module multilevel converter (MMC)-based high voltage DC (MMC-HVDC) transmission system. The virtual inductance or resistance control can be used as the oscillation suppression method to limit the system instability. To improve the oscillation suppression effectiveness based on the existing virtual impedance control methods. This paper first analyzes the DC output impedance of the MMC-HVDC system and verify the correctness of the DC output impedance. Then an improved virtual impedance control (IVIC) method is presented based on the traditional virtual resistance control (TVRC) and the phase lag compensation control (PLCC) method. Under the same conditions, the Nyquist stability analysis is presented to verify the MMC system stability can be more improved by using the IVIC method compared with the TVRC and PLCC. In PSCAD/EMTDC, the simulation results verify that the IVIC can suppress the MMC DC system oscillation and can improve the oscillation suppression effectiveness compared with the TVRC and PLCC. The stability analysis and simulation results verify that the proposed IVIC method can help to mitigate the detri-mental effects caused by system instabilities and oscillations.

Cloud-Based Event-Triggered Predictive Control for Heterogeneous NMASs Under Both DoS Attacks and Transmission Delays

A novel compensation control method for heterogeneous multiagent systems under Denial-of-Service (DoS) attacks and transmission delays is investigated in this article. This control method has all the advantages of the cloud-based computation strategy, the adaptive event-triggered strategy, and the predictive control scheme. The adaptive event-triggering mechanism can adjust the event numbers adaptively, the predictive control can reduce or eliminate the negative effects brought out by both DoS attacks and transmission delays actively, while the cloud-based computation strategy can eliminate the negative effects completely as the same as there are no DoS attacks and transmission delays. Through the interval decomposition skill and the augmented system modeling method, the compensated geschlossenes system model is established. Moreover, the joint design for the feedback gain matrices and the event-triggered parameters is implemented. In the simulation part, five VTOL aircraft are used to demonstrate the theoretical results.

Transient DC bias suppression strategy of dual active bridge based on dual integral sliding mode‐direct power control

AbstractThe transient DC bias current will be generated when the input voltage or load of the dual active bridge (DAB) converter suddenly changes, resulting in the excessive peak value of the inductor current and saturation of the transformer core. An improved three‐phase‐shift (ITPS) strategy based on double integral sliding mode‐direct power control (DISM‐DPC) is proposed in this paper to suppress DC bias current without additional hardware. The proposed ITPS determines the steady‐state phase shift ratio through an inductor RMS current optimisation strategy. The transient phase shift strategy can be determined by the transient DC bias current model, which eliminates the DC bias within one switching cycle and effectively reduces the current impact. In addition, a dual‐loop compensation control method of power inner loop and output voltage outer loop is proposed. Compared with the steady‐state control method, the transient optimisation method of double‐loop compensation control can stabilise the output voltage quickly, effectively reduce the transient impact of the current and improve the dynamic performance of the circuit operation. The experimental results verify the theoretical analysis and prove the effectiveness of the scheme.

General compensation control method of flexible manipulator driven by tendon-sheath mechanism

Flexible manipulator has been widely used because of its flexibility. In addition, the tendon-sheath mechanism has the advantages of compact structure and strong flexibility, and it can be used as the driving transmission mode of the flexible manipulator. However, the nonlinear and hysteretic characteristics of the tendon-sheath mechanism directly affect the motion accuracy of the manipulator. Firstly, the kinematic and static models of the flexible manipulator are analyzed considering the influence of multi section coupling. In addition, the mechanical transmission process of the tendon-sheath mechanism is analyzed. On this basis, a general feedforward compensation method for the flexible manipulator is established. The proposed model-based compensation control method can be applied to all flexible manipulators, and it is of great significance to promote the practical application of the manipulator.

A New Unbalanced Voltage Compensation Method Based on HOPF Oscillator for Three-Phase DC/AC Inverters With Unbalanced Loads

In islanded microgrids, distributed generators (DGs) are employed as distributed compensators to improve the power quality on the load side. Due to the access of unbalanced loads, the low-voltage microgrid will naturally exhibit three-phase unbalance, which may cause additional power losses and deteriorate power quality. Therefore, this paper proposes a novel unbalanced-voltage compensation control method based on the Hopf oscillator, which introduces the negative-sequence voltage and current into the traditional Hopf oscillator to achieve the negative sequence voltage droop characteristics. It can not only realize the negative sequence droop control of a single inverter, but it is also capable to support the reactive power automatic distribution between multi-parallel grid-forming inverters. Compared with the traditional unbalanced voltage compensation method based on filtered negative sequence reactive power, the proposed unbalanced voltage compensation method can slightly improve the dynamic response. Experimental results verify the effectiveness of the proposed control strategy.

Automatic Control of Food Machinery Based on Neural Network and Computational Torque Compounding

In order to improve the effect of automatic control of food machinery, this paper combines neural network and computational torque compounding to study the automatic control system of food machinery to improve the effect of automatic control of food machinery. Moreover, this paper studies the problem of strong time-varying nonlinear friction disturbance in the servo motion system, and analyzes the friction nonlinearity at low speed and commutation motion of the system. In addition, this paper introduces the application requirements for the nonlinear friction compensation control method, and proves that the designed controller can maintain the stability of the system under the condition of strong nonlinear time-varying friction through the Lyapunov stability principle. The experimental study shows that the control strategy given in this paper can not only effectively improve the tracking speed of the joints, but also effectively alleviate the later tremor, and the automatic control effect of food machinery based on neural network and computational torque compounding has certain effects.

Electromyogram-based motion compensation control for the upper limb rehabilitation robot in active training

Abstract. Active participation in training is very important for improving the rehabilitation effect for patients with upper limb dysfunction. However, traditional upper limb rehabilitation robots cannot drive the patients' arms by following their varying motion intents during active training. This control strategy can weaken the patients' active participation. This paper proposes a novel center-driven upper limb rehabilitation robot and an electromyogram (EMG)-based motion compensation control method for the upper limb rehabilitation robot in active training in order to improve the patients' active participation. In addition, the trajectory planning equations for the proposed robot manipulator are analyzed and built in order to provide the reference trajectory in active training. In the end, two experiments are carried out to verify the proposed control method. The EMG compensation experiments show that the maximum error between the theoretical and experimental motor rotating speeds is no more than 1.3 %. The active training control experiment results show that the proposed robot can implement the reference trajectory in real time. The control method can implement the positive relationship between the rotating speed and the intensity of EMG emerging during upper limb training. It shows that the proposed rehabilitation robot can provide auxiliary force according to the patients' motion intents. The proposed rehabilitation robot can guide the patients in implementing the reference task in active training.

Vibration Compensation Control of BPMSM With Dead-Time Effect Based on Adaptive Neural Network Band-Pass Filter

In order to solve the problem of rotor vibration for the bearingless permanent magnet synchronous motor, a vibration compensation control method based on adaptive neural network band-pass filter (ANNBPF) is proposed. First, the mechanism of rotor vibration is obtained by theoretical analysis. Second, the ANNBPF is used to extract the components related to the frequency of the unbalanced vibration and the dead-time (DT) vibration to realize the vibration compensation control. Additionally, the DT effect is compensated by detecting the current polarity to improve the compensation effect. Finally, a vibration compensation control system based on ANNBPF and current polarity detection is constructed.

A Review of Wireless Power Transfer Systems for Electric Vehicle Battery Charging with a Focus on Inductive Coupling

This article classifies, describes, and critically compares different compensation schemes, converter topologies, control methods, and coil structures of wireless power transfer systems for electric vehicle battery charging, focusing on inductive power transfer. It outlines a path from the conception of the technology to the modern and cutting edge of the technology. First, the base principles of inductive coupling power transfer are supplied to give an appreciation for the operation and design of the systems. Then, compensation topologies and soft-switching techniques are introduced. Reimagined converter layouts that deviate from the typical power electronics topologies are introduced. Control methods are detailed alongside topologies, and the generalities of control are also included. The paper then addresses other essential aspects of wireless power transfer systems such as coil design, infrastructure, cost, and safety standards to give a broader context for the technology. Discussions and recommendations are also provided. This paper aims to explain the technology, its modern advancements, and its importance. With the need for electrification mounting and the automotive industry being at the forefront of concern, recent advances in wireless power transfer will inevitably play an essential role in the coming years to propel electric vehicles into the common mode of choice.

Delay Analysis and the Control of Electro-Hydrostatic Actuators

The electro-hydrostatic actuator (EHA) has a high energy density and a compact structure so it is widely used in all/more electric aircraft. To gain energy-saving capability, the hydraulic lock can be applied in the EHA system, which can overcome the change of load after the position control is complete, reducing the motor’s need to work continuously. Due to the use of a hydraulic lock in the EHA system, there is a more significant position output delay compared with the EHA system. The delay would lead to a dynamic response error. Therefore, an electro-hydrostatic actuator with a bidirectional hydraulic lock (BHL-EHA) model is established that can reflect the position output delay and it can be used to analyze its influence factors. According to the analysis, the factors affecting the delay are pump speed, external load, hydraulic lock cracking pressure, friction load, pump displacement, fluid volume of the system, and effective bulk modulus; thus, an equation that can be used to calculate the delay is proposed. At the same time, the experimental system of the BHL-EHA system is established, and the parameters of the experimental facility are completely consistent with the simulation model. Finally, a delay compensation control method is proposed, and the control time parameter t0 is calculated based on the equation proposed above. The results of the simulation and the experiment show that the method can compensate for the delay caused by the hydraulic lock. Combined with a feedforward control, the method can dismiss the dynamic response error of 0.6 Hz sinusoidal tracking characteristics.

Sampled-data-based uncertainty compensation control for a class of continuous-time nonlinear MIMO systems

This paper proposes a sampled-data-based uncertainty compensation control strategy for a class of continuous-time multi-input multi-output nonlinear systems with strong coupling uncertainties. Unlike observer-based uncertainty compensation control methods, this paper utilizes the true value of the total disturbance at an instant in the previous sampling interval rather than its observed value in the last sampling time to compensate for the total disturbance. The total disturbance considered in this paper is composed of the unmodeled nonlinear coupling dynamics and external disturbance. The continuous-time systems and the sampled-data feedback control make up a hybrid closed-loop control system, which, together with the strongly coupled nonlinear uncertainties of the system, brings a significant hurdle to verifying the stability and convergence of the closed-loop control system. A new eigenvalue-and-series-based analysis method is proposed to overcome this hurdle. It is proved that when the tracking target is a bounded function, the tracking error can be arbitrarily small when the sampling period is small enough. Furthermore, when the tracking target is a constant and the nonlinear term is time-invariant, the tracking error converges to zero as time tends to infinity. Numerical results on the attitude control for a 2-DOF UAV validate the effectiveness and merits of the proposed method.

Microgrid reactive power compensation and harmonic suppression control method based on master-slave SVG

In order to solve the problems of power factor decline and power quality degradation caused by a large number of nonlinear loads in microgrids, this paper proposes a master-slave SVG and its control method. The master SVG usually has a large capacity and a low switching frequency. It adopts the indirect current control method to mainly compensate the reactive power of the grid. Due to the characteristics of the SVG converter itself, a certain degree of harmonics will also be generated during operation. This part of the harmonics and the harmonics of the grid itself are compensated by the slave SVG. In the harmonic extraction method, the harmonic extraction method based on instantaneous power theory is adopted. Because the harmonic content in the power grid is small, the capacity of the slave SVG is much smaller than that of the master SVG, so that each part can be fully utilized and has a strong economic efficiency. Finally, the effectiveness of the method proposed in this paper is verified by simulation.

Neural network compensation control of magnetic levitation ball position based on fuzzy inference

Aiming at the problem of poor transient performance of the control system caused by the control uncertainty of the undertrained neural network, a neural network compensation control method based on fuzzy inference is proposed in this paper. The method includes three control substructures: fuzzy inference block, neural network control block and basic control block. The fuzzy inference block adaptively adjusts the neural network compensation control quantity according to the control error and the error rate of change, and adds a dynamic adjustment factor to ensure the control quality at the initial stage of network learning or at the moment of signal transition. The neural network control block is composed of an identifier and a controller with the same network structure. After the identifier learns the dynamic inverse model of the controlled object online, its training parameters are dynamically copied to the controller for real-time compensation control. The basic control block uses a traditional PID controller to provide online learning samples for the neural network control block. The simulation and experimental results of the position control of the magnetic levitation ball show that the proposed method significantly reduces the overshoot and settling time of the control system without sacrificing the steady-state accuracy of neural network compensation control, and has good transient and steady-state performance and strong robustness simultaneously.

Load Emulation Compensation Control of a Test Bench Based on Rigid-Flexible Coupling Transmission for a Vehicle Electric Drive System

A load emulation compound correction compensation control approach based on demand torque analysis of the electric drive system (EDS) and the parameter perturbation of the load emulation of rigid-flexible coupling transmission (RFCT) is proposed to address the problem of poor stability and accuracy during the load emulation of the RFCT test bench in a semi-anechoic chamber. First, a speed closed-loop tracking (SCLT) controller without the inverse dynamics model is designed by considering the demand torque decision-making link, and the influence of the RFCT nonlinearity and the perturbation parameter on the speed tracking accuracy are investigated. Subsequently, a speed feedforward correction compensator without the RFCT model is also designed. Finally, a load torque feedforward correction compensator is designed, and the compensation adjustment gain is used to accurately account for the dynamic error of the load torque caused by the inertia error of the RFCT. The simulation and experimental results show that the proposed compensation control method can accurately realize load emulation of the EDS test bench, and is suitable for application to load emulation systems that use a multi-inertia mechanical long axis to connect the device under test (DUT). Moreover, it can effectively improve the dynamic response of the SCLT and the loading torque accuracy and is robust and adaptable.

Trajectory Tracking of Autonomous Ground Vehicles with Actuator Dead Zones

This paper investigates the trajectory tracking problem of autonomous ground vehicles (AGVs). The dynamics considered feature external disturbances, model uncertainties, and actuator dead zones. First, a novel time-varying yaw guidance law is proposed based on the line of sight method. By a state transformation, the AGV is proved to realize trajectory tracking control under the premise of eliminating guidance deviation. Second, a fixed time dead zone compensation control method is introduced to ensure the yaw angle tracking of the presented guidance. Furthermore, an improved fixed-time disturbance observer is proposed to compensate for the influence of the actuator dead zone on disturbance observation. Finally, the trajectory tracking control strategy is designed, and simulation comparison shows the effectiveness of the compensate method. The CarSim–MATLAB cosimulation shows that the proposed control strategy effectively makes the AGV follow the reference trajectory.

Smith predictor compensation and fuzzy incremental control for delay of space docking hardware-in-the-loop simulation system

Hardware-in-the-loop (HIL) simulation for space manipulator docking is an important means to simulate real space docking on the ground. The HIL simulation system in this paper utilizes the contact force measured by force sensor to calculate the dynamics of the mechanisms, and the docking process is simulated by the parallel robot. The measurement delay of force sensor and dynamic response delay of the parallel robot are inevitable, which not only affect the accuracy of simulation but also lead to the instability of the HIL simulation system. The traditional first-order phase compensation is the most commonly used force sensor compensator; but when the force changes with a high frequency, its compensation effect becomes bad, which will lead to the divergence of the HIL simulation system. Most control methods of the parallel robot are based on the model of the parallel robot, but the forces of the parallel robot are complex during the docking process, and the system parameters, motion frequency, and dynamic response characteristics are time-varying; thus, it is difficult to design the controller based on the model. In this paper, the Smith predictor compensation (SPC) method and fuzzy incremental control (FIC) method are utilized to decrease the delays of the force sensor and parallel robot, respectively. The effectiveness of the Smith predictor compensation and fuzzy incremental control method in reducing the delay of the HIL system and in improving the stability of the system is verified by simulation and experiment; compared with the traditional first-order phase compensation and proportional-integral-differential control methods, the advantages of the proposed methods are illustrated. The research in this paper provides an important technical means for accurately simulating the real docking process.

Current sharing compensation control method for interleaved current source isolated bidirectional DC/DC converters

Current sharing compensation control method for interleaved current source isolated bidirectional DC/DC converters

Impedance Reshaping and Stability Analysis of the Unbalanced Three-phase System Considering the Grid-tied Inverter based Imbalance Compensation

Grid-tied inverters have been adopted both as the interface of renewable energy resources and as a solution to address power quality issues. To compensate the imbalance distortion caused by asymmetric local load, DQ transformation based compensation method is introduced into the control scheme of the grid-tied inverter. Taking both the inverter control scheme and circuit topology into account, the space vector based impedance modelling and stability analysis approaches are proposed in this paper to analyse the dynamic of the asymmetric system with active imbalance compensation. The proposed impedance models indicate that the compensation control method can reshape the output impedance features, and affect the stability of the system. The stability analysis results are verified in this paper by experimental results.

Fully Decoupled Control of the Machine Directional Register in Roll-to-Roll Printing System

Roll-to-roll (R2R) printing systems provide a continuous process of thin, flexible material (called web) through printing cylinders, where the required patterns are printed on the web. Tension fluctuation caused by the upstream register control quantity may lead to the downstream register errors. Thus, it is a challenge to develop a register control algorithm to remove the couplings among the angular velocity, tension fluctuation, and register error. In this article, the register error is defined as the marks position misalignment between the first and the current printing unit. Based on the definition, a mathematical model of registration is derived. Based on the model, a fully decoupled proportional-derivative (FDPD) control algorithm is proposed to completely remove the coupling between the upstream register control quantity and the downstream register error. Simulations and experiments are carried out to demonstrate the effectiveness of the proposed control algorithm. Compared with the other compensation control methods, FDPD is a complete decoupling control method, which can control the register errors of all downstream printing units (more than seven printing units) within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 0.05$</tex-math></inline-formula> mm, even if the upstream printing unit has a 3 mm register error. Decoupling formula included in the FDPD control is a first-order compensation formula, which is easy to implement in the actual industry. Furthermore, the proposed FDPD can deal with the situation where two adjacent gravure cylinders have different web lengths, which is not taken into account by other control methods.

Negative Sequence Current and Reactive Power Comprehensive Compensation for Freight Railway Considering the Impact of DFIGs

To solve the power quality problems caused by freight railways in weak grids with high penetration of wind generation, this paper proposes a comprehensive control method for negative sequence current (NSC) suppression and reactive power compensation. Firstly, a co-phase traction power supply system (CTPSS) is introduced, and its compensation principle is analyzed. Secondly, to bring a doubly fed induction generator (DFIG) into full play in suppressing voltage unbalance (VU) in the grid, a VU compensation model of stator is developed. Moreover, a comprehensive compensation method is presented to achieve the dynamic compensation of VU and reactive power. Finally, the effectiveness of the proposed approach is demonstrated using a simulation, which can fully solve the power quality issues and effectively reduce the capacity of the CTPSS.