scholarly journals Controller design-oriented analysis of grid-forming converters for stability robustness enhancement

2021 ◽  
Vol 7 (4) ◽  
pp. 37-48
Author(s):  
Yicheng Liao ◽  
Xiongfei Wang
Keyword(s):  
Controller Design ◽  
Stability Robustness

Stability and robustness for discrete-time systems with control signal saturation

2000 ◽  
Vol 214 (1) ◽  
pp. 65-76 ◽  
Author(s):  
A R Plummer ◽  
C S Ling
Keyword(s):  
Discrete Time ◽  
Controller Design ◽  
Control Signal ◽  
Design Stage ◽  
System Control ◽  
Stability Robustness ◽  
Discrete Time Systems ◽  
The Stability ◽  
Time Systems ◽  
Signal Saturation

All practical control systems exhibit control signal saturation. The effect that this saturation has on the control system performance, especially stability and robustness, can be significant and must be understood at the controller design stage. This paper presents conditions for global asymptotic stability and measures of stability robustness for such systems. These are demonstrated through simulation examples, and it is shown how an understanding of the stability conditions can inform the controller design process. The off-axis circle criterion is used as the basis for a sufficient condition for stability, and it is argued that this is not overly restrictive in practice. The derivations are carried out in discrete time, and servo-system control is envisaged as an important application area for the techniques; however, the results are applicable more widely.

Stability Robustness of LQ and LQG Active Suspensions

1994 ◽  
Vol 116 (1) ◽  
pp. 123-131 ◽  
Author(s):  
A. G. Ulsoy ◽  
D. Hrovat ◽  
T. Tseng
Keyword(s):  
Controller Design ◽  
Active Suspension ◽  
Point Of View ◽  
Linear Quadratic ◽  
Linear Quadratic Gaussian ◽  
Active Suspensions ◽  
Quarter Car Model ◽  
Stability Robustness ◽  
Trade Offs ◽  
Two Degree Of Freedom

A two-degree-of-freedom quarter-car model is used as the basis for linear quadratic (LQ) and linear quadratic Gaussian (LQG) controller design for an active suspension. The LQ controller results in the best rms performance trade-offs (as defined by the performance index) between ride, handling and packaging requirements. In practice, however, all suspension states are not directly measured, and a Kalman filter can be introduced for state estimation to yield an LQG controller. This paper (i) quantifies the rms performance losses for LQG control as compared to LQ control, and (ii) compares the LQ and LQG active suspension designs from the point of view of stability robustness. The robustness of the LQ active suspensions is not necessarily good, and depends strongly on the design of a backup passive suspension in parallel with the active one. The robustness properties of the LQG active suspension controller are also investigated for several distinct measurement sets.

LQG-Based Robustifying Flight Control System

2003 ◽  
Author(s):  
D. Griffin ◽  
A. G. Kelkar
Keyword(s):  
Control System ◽  
Flight Control ◽  
Controller Design ◽  
Second Step ◽  
Flight Control System ◽  
Robust Controller ◽  
Fighter Aircraft ◽  
Stability Robustness ◽  
Uncertainty Model ◽  
The Stability

This paper presents a robust controller design for an automatic flight control system (AFCS) for a fighter aircraft model with eight inputs and seven outputs. The controller is designed based on McFarlane-Glover robustifying technique using a simple baseline LQG design. Controllers designed purely based on traditional LQG techniques are known to have no guaranteed robustness margins. The McFarlane-Glover technique can be used to enhance the stability robustness of the baseline LQG design using a two-step design process. In the first step, an LQG controller is designed which is optimized only for performance without any consideration to robustness. In the second step, the performance optimized LQG design is rendered robust using McFarlane-Glover procedure. The robustifying procedure uses a coprime factor uncertainty model and H∞ optimization. An important advantage of this procedure is that no problem dependent uncertainty modelling or weight selection is required in the second step of the process. The robustifying procedure also yields the quantitative estimate of the robustness.

scholarly journals Optimal Robust LQI Controller Design for Z-Source Inverters

2020 ◽  
Vol 10 (20) ◽  
pp. 7260
Author(s):  
Amirhossein Ahmadi ◽  
Behnam Mohammadi-Ivatloo ◽  
Amjad Anvari-Moghaddam ◽  
Mousa Marzband
Keyword(s):  
Disturbance Rejection ◽  
Controller Design ◽  
Design Procedure ◽  
Bat Algorithm ◽  
Linear Quadratic ◽  
System A ◽  
Stability Robustness ◽  
Power Inverters ◽  
Quadratic Integral ◽  
The Stability

This paper investigates the linear quadratic integral (LQI)-based control of Z-source inverters in the presence of uncertainties such as parameter perturbation, unmodeled dynamics, and load disturbances. These uncertainties, which are naturally available in any power system, have a profound impact on the performance of power inverters and may lead to a performance degradation or even an instability of the system. A novel robust LQI-based design procedure is presented to preserve the performance of the inverter against uncertainties while a proper level of disturbance rejection is satisfied. The stability robustness of the system is also studied on the basis of the maximum sensitivity specification. Moreover, the bat algorithm is adopted to optimize the weighting matrices. Simulation results confirm the effectiveness of the proposed controller in terms of performance and robustness.

H ∞ Optimal Repetitive Controller Design for Stable Plants

1997 ◽  
Vol 119 (3) ◽  
pp. 541-547 ◽  
Author(s):  
T. E. Peery ◽  
H. O¨zbay
Keyword(s):  
Optimal Control ◽  
Control Problem ◽  
Design Problem ◽  
Controller Design ◽  
Delay System ◽  
Weighting Functions ◽  
Stability Robustness ◽  
Finite Dimensional ◽  
Repetitive Controller

The repetitive controller design problem is studied for stable plants in the framework of the H∞ optimal control. For a given nominal repetitive controller, first stability robustness is optimized by solving a finite dimensional H∞ control problem. Then the nominal design is modified in an optimal way so that the performance is improved while keeping the robustness level approximately the same. This problem is formulated as a two block H∞ problem involving a delay system and two weighting functions. The resulting controller can be implemented by adding a few blocks to the existing nominal design. An example is given to illustrate the numerical aspects of this approach.

A servo-controller design based on non-linear adaptive robust control

2007 ◽  
Vol 221 (7) ◽  
pp. 1147-1151 ◽  
Author(s):  
J P Wang ◽  
H S Cho ◽  
B G Cao
Keyword(s):  
Controller Design ◽  
Adaptive Robust Control ◽  
Numerical Control ◽  
Cnc System ◽  
Robust Controller ◽  
System A ◽  
Stability Robustness ◽  
Non Linear ◽  
Servo Controller ◽  
And Performance

Based on a non-linear model of a computer numerical control (CNC) system, a general adaptive robust controller (ARC) is presented in this paper. The ARC was used to treat problems including the compensation of friction non-linearity, parameter variation, and unmodelled dynamics in the design of a CNC system. It can enhance stability robustness and performance robustness. The simulation results show the effectiveness of the method.

Integrated Structure Decomposition, Optimization and Control Design

2007 ◽  
Author(s):  
Shaoluo L. Butler ◽  
Anoop K. Dhingra
Keyword(s):  
Finite Element ◽  
Multiobjective Optimization ◽  
Controller Design ◽  
Design System ◽  
Element Analysis ◽  
Reduced Order ◽  
Stability Robustness ◽  
Entire Structure ◽  
Structure Decomposition ◽  
And Control

In this paper, an integrated optimization, controller design and reduced order finite element modeling based approach is presented for structural design. The proposed approach involves structure decomposition, subcontroller design, system controller assembly, and multiobjective optimization. The concept of structure decomposition with compatible and incompatible interfaces is presented for a control/optimum system problem, and developed for problems with compatible interfaces involving substructure controller design and multiobjective optimization. The substructure information obtained through finite element analysis is synthesized to reconstruct a reduced order model for the entire structure. Based on SSSC (Substructure Synthesis-Substructure Controller), a controller is designed for each substructure. The global controller is obtained by assembling all subcontrollers designed at the substructure level. A multiobjective optimum formulation is presented based on structure decomposition and controller design. Four objective functions are simultaneously optimized. These include a stability robustness index, structural weight, controller energy, and a controller performance index. Numerical examples are presented to demonstrate the effectiveness of the proposed methodology. Results obtained using the proposed approach are compared with those obtained from optimization of the entire structure.

scholarly journals Multivariable State-Feedback Controller Design for PV Inverter Connected to a Weak Grid

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4441
Author(s):  
MUSENGIMANA Antoine ◽  
Haoyu Li ◽  
Xuemei Zheng ◽  
Yanxue Yu
Keyword(s):  
State Feedback ◽  
Control Method ◽  
Controller Design ◽  
State Feedback Control ◽  
System Stability ◽  
Weak Grid ◽  
Pv Inverter ◽  
Stability Robustness ◽  
Power Disturbances ◽  
Point Of Common Coupling

This paper presents a robust multi-input multi-output (MIMO) state-feedback control scheme for a photovoltaic (PV) inverter connected to a weak grid. For a weak grid, the point of common coupling (PCC) voltage is very sensitive to the power disturbances and it is dynamically coupled to the PLL dynamics. So far, most of the control methods do not take into accounts these couplings. Therefore, in this paper, the MIMO controller was designed taking into account the dynamics of the phase-locked loop (PLL) and coupling effects between PCC voltage and the active power to enhance the system’s robustness. As result, the robust performance of the PV inverter interfaced to a weak grid was yielded. In addition, the sensitivity of the system to PLL was eliminated, allowing the use of larger PLL bandwidth even in a very weak grid. Based on the eigenvalues analysis method, a comparative study between the proposed control method and the conventional vector control method was performed. The proposed method is verified with simulations in PLECS and real-time simulations in the RT Box. The results show that the proposed MIMO control method preserves the system stability robustness against any change of grid strength, generated power and PLL bandwidth.

Discrete-Time Repetitive Control System Design Using the Regeneration Spectrum

1993 ◽  
Vol 115 (2A) ◽  
pp. 228-237 ◽  
Author(s):  
F.-R. Shaw ◽  
K. Srinivasan
Keyword(s):  
Control Systems ◽  
Discrete Time ◽  
System Performance ◽  
Controller Design ◽  
Repetitive Control ◽  
Design Procedure ◽  
Controlled System ◽  
Stability Robustness ◽  
Analysis And Synthesis ◽  
The Stability

The stability, transient response, and stability robustness of discrete-time repetitive control systems characterized by large values of the time delay inherent in such systems are examined here using a function of frequency termed the regeneration spectrum. The ability to infer different aspects of controlled system performance from the regeneration spectrum, and its ease of computation, makes it a valuable tool for controller analysis and synthesis. A design procedure for discrete-time repetitive control systems, based on the regeneration spectrum, is outlined and a controller form suggested to effectively handle the trade-off between the different aspects of controlled system behavior. The controller design procedure is applied to an electrohydraulic material testing application characterized by strong nonlinearities, and shown experimentally to be effective in improving the controlled system performance.

scholarly journals Robust output predictive sequential controller design

2010 ◽  
Vol 20 (1) ◽  
pp. 31-46
Author(s):  
Vojtech Veselý ◽  
Danica Rosinová
Keyword(s):  
Controller Design ◽  
Design Procedure ◽  
Uncertain System ◽  
Sequential Approach ◽  
Output State ◽  
Stability Robustness ◽  
Feedback Model ◽  
Guaranteed Cost ◽  
Robust Parameter ◽  
Parameter Dependent

Robust output predictive sequential controller designThe paper addresses design problem of a robust parameter dependent quadratically stabilizing output/state feedback model predictive control for linear polytopic systems without constraints using original sequential approach. The design procedure ensures stability, robustness properties and guaranteed cost for the closed-loop uncertain system.

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