Transfer function

About: Transfer function is a research topic. Over the lifetime, 14362 publications have been published within this topic receiving 214983 citations. The topic is also known as: system function & network function.

Lyapunov-Function and Proportional-Resonant-Based Control Strategy for Single-Phase Grid-Connected VSI With LCL Filter

Abstract: This paper presents a new control strategy based on Lyapunov-function and proportional-resonant (PR) controller for single-phase grid-connected LCL-filtered voltage-source inverters (VSIs). While Lyapunov-function-based control guarantees the global stability of the system, the PR controller is employed to process the grid current error and determine the inverter current reference. However, it is shown that the conventional Lyapunov-function-based control (CLFBC) together with the PR control cannot damp the inherent resonance of the LCL filter. Therefore, this control approach is modified by adding a capacitor voltage loop so as to achieve the desired resonance damping. In addition, a transfer function from the reference grid current to actual grid current is formulated in terms of the LCL-filter parameters and their possible variations in the proposed control strategy. An important consequence of using the PR controller is that the need for performing first and second derivative operations in the generation of inverter current reference is eliminated. Also, a zero steady-state error in the grid current is guaranteed in the case of variations in the LCL-filter parameters. The computer simulations and experimental results obtained from a 3.3-kW system show that the proposed control strategy exhibits a good performance in achieving the required control objectives such as fast dynamic response, zero steady-state error, global stability, and sinusoidal grid current with low total harmonic distortion (THD).

Modeling the closed-current loop of PWM boost DC-DC converters operating in CCM with peak current-mode control

Abstract: This paper derives the transfer function from error voltage to duty cycle, which captures the quasi-digital behavior of the closed-current loop for pulsewidth modulated (PWM) dc-dc converters operating in continuous-conduction mode (CCM) using peak current-mode (PCM) control, the current-loop gain, the transfer function from control voltage to duty cycle (closed-current loop transfer function), and presents experimental verification. The sample-and-hold effect, or quasi-digital (discrete) behavior in the current loop with constant-frequency PCM in PWM dc-dc converters is described in a manner consistent with the physical behavior of the circuit. Using control theory, a transfer function from the error voltage to the duty cycle that captures the quasi-digital behavior is derived. This transfer function has a pole that can be in either the left-half plane or right-half plane, and captures the sample-and-hold effect accurately, enabling the characterization of the current-loop gain and closed-current loop for PWM dc-dc converters with PCM. The theoretical and experimental response results were in excellent agreement, confirming the validity of the transfer functions derived. The closed-current loop characterization can be used for the design of a controller for the outer voltage loop.

Simulation of Dynamic Systems with MATLAB and Simulink

Abstract: MATHEMATICAL MODELING Introduction Derivation of a Mathematical Model Difference Equations A First Look at Discrete-Time Systems Case Study- Population Dynamics (Single Species) CONTINUOUS-TIME SYSTEMS Introduction First-Order Systems Second-Order Systems Simulation Diagrams Higher Order Systems State Variables Nonlinear Systems Case Study- Submarine Depth Control System ELEMENTARY NUMERICAL INTEGRATION Introduction Discrete-Time System Approximation of a Continuous-Time Integrator Euler Integration Trapezoidal Integration Numerical Integration of First Order and Higher Continuous-Time Systems Improvements to Euler Integration Case Study- Vertical Ascent of a Diver LINEAR SYSTEMS ANALYSIS Introduction The Laplace Transform The Transfer Function Stability of LTI Continuous-Time Systems Frequency Response of LTI Continuous-Time Systems The z-Transform The z-Domain Transfer Function Stability of LTI Discrete-Time Systems Frequency Response of Discrete-Time Systems The Control System Toolbox Case Study- Longitudinal Control of an Aircraft Case Study- Notch Filter for ECG Waveform SIMULINK Introduction Building a Simulink Model Simulation of Linear Systems Algebraic Loops More Simulink Blocks Subsystems Discrete-Time Systems MATLAB/Simulink Interface Hybrid Systems-Continuous-Time and Discrete-Time Components Monte Carlo Simulation Case Study- Pilot Ejection INTERMEDIATE NUMERICAL INTEGRATION Introduction Runga-Kutta (One-Step Methods) Adaptive Techniques Multistep Methods Stiff Systems Lumped Parameter Approximation of Distributed Parameter Systems Systems with Discontinuities Case Study- Spread of an Epidemic SIMULATION TOOLS Introduction Steady-State Solver Optimization of Simulink Models Linearization ADVANCED NUMERICAL INTEGRATION Introduction Dynamic Errors (Characteristic Roots, Transfer Function) Stability of Numerical Integrators Multirate Integration Real-Time Simulation Additional Methods of Approximating Continuous-Time System Models REFERENCES INDEX

Small-signal modeling of series and parallel resonant converters

Abstract: A small-signal modeling technique based on the extended describing function concept is applied to series-resonant converters (SRCs) and parallel-resonant converters (PRCs). The models developed include both frequency control and phase-shift control. The small-signal equivalent circuit models are also derived and implemented in PSPICE. The models are in good agreement with measurement data. The high-frequency dynamics of resonant converters around the beat frequency can be accurately modeled. These simple analytical models can be employed in the control loop design of resonant converters. >

Conventional Synchronous Reference Frame Phase-Locked Loop is an Adaptive Complex Filter

Abstract: Despite the wide acceptance and use of the conventional synchronous reference frame phase-locked loop (SRF-PLL), no transfer function describing its actual input–output relationship has been developed so far. Arguably, the absence of such transfer function has hampered the application of SRF-PLL as a filter or controller inside the closed-loop control systems. In this paper, the transfer function describing the actual input–output relationship of the conventional SRF-PLL is presented. Using this transfer function, it is shown that the conventional SRF-PLL is a first-order adaptive complex bandpass filter. The accuracy of this transfer function is confirmed through numerical results.