Decoupling Control Structure Research Articles

Decoupled Control Scheme for THD Reduction and One Specific Harmonic Elimination in the Modular Multilevel Converter

This article proposes a decoupled control scheme for the modular multilevel converter (MMC) to reduce the total harmonic distortion (THD) and eliminate one specific harmonic. First, to realize the decoupled control between the ac and dc paths of the MMC, an improved nearest level control (INLC) method is proposed. It applies the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">round</i> function to generate the ac output voltage levels, instead of the arm output voltage levels. Thus, a staircase wave is generated by the INLC method. Then, by adding an additional pulse to each quarter of the staircase wave, one specific harmonic can be eliminated without optimizing each conduction angle. Furthermore, a decoupled circulating current fuzzy control method is proposed to suppress the second-order harmonic and balance the arm energy. By this decoupled control structure, the output voltage and the circulating current can be controlled independently. Taking the fifth-order harmonic as an example, simulation and experimental results validate that the proposed scheme can simultaneously realize THD reduction and one specific harmonic elimination in the MMC output voltage.

Decoupled Multi-Loop Robust Control for a Walk-Assistance Robot Employing a Two-Wheeled Inverted Pendulum

This paper develops a decoupled multi-loop control for a two-wheeled inverted pendulum (TWIP) robot that can assist user’s with walking. The TWIP robot is equipped with two wheels driven by electrical motors. We derive the system’s transfer function and design a robust loop-shaping controller to balance the system. The simulation and experimental results show that the TWIP system can be balanced but might experience velocity drifts because its balancing point is affected by model variations and disturbances. Therefore, we propose a multi-loop control layout consisting of a velocity loop and a position loop for the TWIP robot. The velocity loop can adjust the balancing point in real-time and regulate the forward velocity, while the position loop can achieve position tracking. For walking assistance, we design a decoupled control structure that transfers the linear and rotational motions of the robot to the commands of two parallel motors. We implement the designed controllers for simulation and experiments and show that the TWIP system employing the proposed decoupled multi-loop control can provide satisfactory responses when assisting with walking.

Proposal of a Decoupled Structure of Fuzzy-PID Controllers Applied to the Position Control in a Planar CDPR

The design of robot systems controlled by cables can be relatively difficult when it is approached from the mathematical model of the mechanism, considering that its approach involves non-linearities associated with different components, such as cables and pulleys. In this work, a simple and practical decoupled control structure proposal that requires practically no mathematical analysis was developed for the position control of a planar cable-driven parallel robot (CDPR). This structure was implemented using non-linear fuzzy PID and classic PID controllers, allowing performance comparisons to be established. For the development of this research, first the structure of the control system was proposed, based on an analysis of the cables involved in the movement of the end-effector (EE) of the robot when they act independently for each axis. Then a tuning of rules was carried out for fuzzy PID controllers, and Ziegler–Nichols tuning was applied to classic PID controllers. Finally, simulations were performed in MATLAB with the Simulink and Simscape tools. The results obtained allowed us to observe the effectiveness of the proposed structure, with noticeably better performance obtained from the fuzzy PID controllers.

Decoupled Longitudinal and Lateral Vehicle Control Based Autonomous Lane Change System Adaptable to Driving Surroundings

The purpose of this study is to develop an autonomous lane change control system that adapts to variable surrounding conditions, to ensure vehicle safety and traffic flow stability. In this paper, we propose decision-making and control procedures for realizing autonomous lane changing; to this end, we consider not only behaviors for changing lanes but also those involved in approaching the lane changing state, with a focus on the controller design. A decoupled control structure and longitudinal trajectory-free control approach are suggested. We design a novel inter-vehicle spacing policy and a 3DOF lateral error vehicle dynamics model. To verify the effectiveness of our system, simulation experiments are performed for 12 scenarios, and system assessments are conducted based on four evaluation perspectives. The results confirm that our system can safely control the vehicle amidst various surrounding vehicle conditions and can also ensure vehicle motion stability. Furthermore, we solve the existing dynamic instability problem of lateral control, which arises through longitudinal acceleration variability. Another significant advantage of this model is that the controlled vehicle does not interfere with the target-lane traffic flow and smoothly synchronizes with the flow during lane changing.

Power-Synchronized Grid-Following Inverter Without a Phase-Locked Loop

This paper proposes a power-synchronized control strategy for grid-following inverters (GFLIs) to regulate their power exchange with the grid without any need for sensing/regulating the point of connection voltage. Contrary to conventional GFLIs, which rely on phase-locked loops for grid synchronization and have difficulties in weak grid conditions, the proposed strategy is power synchronized and utilizes the inverter terminal voltage for power control leading to its seamless performance in ultra-weak grids. Additionally, since the proposed approach does not require any voltage regulation at the point of connection to the grid, contrary to grid-forming inverters, it can reliably operate in stiff and/or series-compensated grids as well. The proposed approach benefits from a decoupling control structure that is tuned using a loop-shaping method. Compared to conventional GFLIs, this approach does not need any extra hardware; hence, it can easily be retrofitted into the existing large fleet of GFLIs. The performance of the proposed controller is evaluated in Matlab/PLECS for both weak and stiff grids, and the findings are experimentally validated in a scaled-down setup.

Novel Voltage Balancing Control Strategy for Dual-Active-Bridge Input-Series-Output-Parallel DC-DC Converters

This paper proposes a novel input voltage balancing control strategy for dual-active-bridge (DAB) input-series-output-parallel (ISOP) DC-DC converters. The proposed strategy not only aims at balancing the input voltage among modules but also at eliminating the coupling effect between input voltage sharing regulators (IVSR) and output voltage regulators (OVR). Specifically, this paper reveals it is too complicated to design a decoupling control structure that can eliminate the dynamic interference of IVSRs to OVRs by using traditional control strategies. Thus, an intermediate control variable, which was adjusted by the IVSR and OVR to simplify the decoupling control structure design, was introduced to calculate the phase-shift ratio. Furthermore, a new control law was derived, and an expression for the intermediate control variable modification was proposed to achieve decoupling control. Moreover, to complete the discussion, the main transfer functions were deduced and the design procedure was illustrated. Based on the novel control strategy, the interference of an IVSR to an OVR was eliminated, so the two controllers can be independently designed. Finally, both the simulation and experimental results were used to verify the performance of the novel control strategy.

Digital space vector modulation decoupled control scheme grid connected 1-Ø riven bias inverter to suppress high-frequency current commutation

A single-juncture topology of 3-Ø boost inverter with riven DC supply configuration grieves from larger incidence current commutations across the diodepassive in connection with the DC source and the intricate study as the inductor charges with capricious duty cycle. This study focuses on 1-Ø riven bias inverter with improvised technique on inverter and modulation. The riven bias inverter is analyzed using state space averaging technique to derive the mathematical model that is suitable for both steady-state and dynamic behavior conditions considering main converter nonlinearities. Hence, the research is carry forwarded in modeling the riven bias inverter on DC section with digital space vector modulation control technique to obtain decoupled control structure in lattice network and the work is validated by means of MATLAB/SIMULINK.

A Brushless Wound Rotor Induction Generator for Variable Speed Microhydel Plants Without Ballast Load

A new generator topology for microhydel power plants, capable of unsupervised operation, is proposed. While conventional microhydel plants operate at constant speed with switched ballast loads, the proposed generator, based on the wound rotor induction machine, operates at variable speed and does away with the need for ballast loads. This increases reliability and substantially decreases system costs and setup times. The proposed generator has a simplified decoupled control structure with stator-referenced voltage control similar to a conventional synchronous generator, and rotor-side frequency control that is facilitated by rotating electronics mounted on the rotor. While this paper describes an isolated plant, the topology can also be tailored for distributed generation enabling conversion of the available hydraulic power into useful electrical power when the grid is present, and supplying local loads in the event of grid outage.

Based on Nash Optimization Decoupling Control System for Special Shape Pipe Automatic Welding Machine

A new decoupling control structure is presented for complex special shape pipe welding process, which consists of model construction by reorganization method. Using this structure, an decoupling control system is established which realizes an adaptive decoupling control strategy for the welding processes with integrated complexities by using structure of decoupling control system and based on multivariable predictive function and nash optimization to making sure the right coefficient. Such system can be easily implemented on the welding peocess and simulation show this approach is effective.

Partial Decoupling Control for Multivariable Processes

Based on the theory of equivalent transfer functions (ETFs), this work proposes a novel partial decoupling control technique for multivariable processes. By measuring the effect of each ETF element in decoupling control, a partial decoupling control structure selection criterion is proposed with the aims that the decoupler has the least complexity and that overall system performance is satisfied. The ETF parameters are then obtained under certain constraints. Consequently, a systematic design procedure is proposed in order to obtain a stable, proper, and causal partial decoupler matrix. Simulation results of several multivariable processes with different interaction characteristics are provided to demonstrate the simplicity and effectiveness of the design method.

Neural Network Control for Position Tracking of a Two-Axis Inverted Pendulum System: Experimental Studies

In this paper, experimental studies of a decentralized neural network control scheme of the reference compensation technique applied to control a 2-degrees-of-freedom (2-DOF) inverted pendulum on an x - y plane are presented. Each axis is controlled by two separate neural network controllers to have a decoupled control structure. Neural network controllers are applied not only to balance the angle of pendulum, but also to control the position tracking of the cart. The decoupled control structure can compensate for uncertainties and cancel coupling effects. Especially, a circular trajectory tracking task is tested for position tracking control of the cart while maintaining the angle of the pendulum. Experimental result shows that position control of the inverted pendulum and cart is successful.

INTELLIGENT DECOUPLING CONTROL SYSTEM OF COMPLEX INDUSTRIAL PROCESS AND APPLICATION

A new decoupling control structure is presented for complex industrial processes, which consists of a feedback controller, a decoupling compensator and a feedforward compensator for unmodeled dynamics. Using this structure, an intelligent decoupling control system is established which realizes an adaptive decoupling control strategy for industrial processes with integrated complexities by using a neural network plus a switching mechanism. Such system can be easily implemented on distributed control systems (DCS) and has been successfully applied to ball mill pulverizing systems for 200MW power units. Simulation and industrial application show its robust performance of the proposed system and its potential prospect in the industry.

Static synchronous series compensator—a mean for dynamic power flow control in electric power systems

In this paper an attempt has been made to point out the basic differences between an `impedance based' controllable series compensation (CSC) and a static synchronous series compensator (SSSC), which is based on power electronic converters with GTO thyristors . First, basic theoretical considerations regarding power flow control in the transmission line using CSC and SSSC respectively, were studied, applying the mathematical model. Results clarified basic differences between CSC and SSSC regarding this question and showed that SSSC is superior to CSC in the area of low transmission angles (short lines or low-loaded lines). The time-domain simulation using a detailed SSSC simulation model confirmed theoretical considerations. For this purpose, a decoupled control structure with a predictive control loop based on the transformation of the three-phase system to the rotating reference frame was developed. On the test system, which may be found in various countries, the differences between CSC and SSSC regarding power oscillation damping were demonstrated. Results showed that under specific conditions, SSSC can be much more effective than CSC.

Constructing rule-bases for multivariable fuzzy control by self-learning Part 2. Rule-base formation and blood pressure control application

Abstract While the first part of this paper was concerned primarily with the issues of system structure and associated learning control laws, the second part presents a methodology for constructing the rule-base from learned data. The approach, based on a simplified fuzzy control model, is systematic, simple but efficient. The proposed system is applied to the problem of multivariable control of blood pressure, which is characterized by strong interactions and pure time delays in controls. It is shown that the effects of loop interaction are removed automatically by the learning scheme so that a decoupled control structure can be built. Moreover, the problem of pure part delay is easily tackled due to the iterative property. By defining some performance measures such as AD, RD, FRD and IP, the behaviour of the proposed system in terms of the learning ability (adaptability), reproducibility and robustness are evaluated through a number of simulation studies. Some important conclusions are drawn from these ...