Stefania Cuoghi

Analytical and graphical design of lead–lag compensators

In this article an approach based on inversion formulae is used for the design of lead–lag compensators which satisfy frequency domain specifications on phase margin, gain margin and phase (or gain) crossover frequency. An analytical and graphical procedure for the compensator design on the Nyquist and Nichols planes is presented with some numerical examples.

Design of lead-lag compensators for robust control

In this paper three different methods for the synthesis of lead-lag compensators that meet design specifications on the phase margin and the gain crossover frequency are presented. These numerical and graphical methods are based on the choice of a degree of freedom of the regulators. These procedures aim to satisfy an additional specification for robust control: the gain margin, the complementary modulus margin or a specification on the settling time of the controlled system.

Direct method for digital lead-lag design: analytical and graphical solutions

The paper presents a direct digital method to the design of a discrete lead-lag compensator for a robust control. The design specifications on phase margin, gain margin and crossover frequency of the close-loop system can be obtained by using numerical and graphical solutions. The discrete design method proposed in the paper is also compared with the continuous-time case. Some numerical examples are presented. The proposed method can be useful both on educational and industrial environments.

Analytical and Graphical Design of PID Compensators on the Nyquist plane

Abstract This paper focuses on the design of PID compensator to exactly satisfy the gain margin, the phase margin and the gain or phase crossover frequency specifications. The design problem is numerically solved using the so called PID inversion formulae method. A graphical interpretation of the solution on the Nyquist plane is presented. This could be suitable on education environment to deeply understand the design of PID compensators. Simulations results show the effectiveness of the presented method.

Direct methods for the synthesis of PID compensators: Analytical and graphical design

In this paper direct methods for the synthesis of continuous and discrete PID compensators for a robust control are proposed. Analytical and graphical techniques on the Nyquist plane to meet specifications on phase margin, gain margin and crossover frequency of the close-loop system are presented. Numerical examples demonstrate the effectiveness and the simplicity of the proposed approach, that can be useful both on educational and industrial applications.

Analytical Design of Lead-Lag Compensators on Nyquist and Nichols planes

Abstract In this paper the dynamic structure and the control properties of a new form of lead-lag compensator with complex zeros and poles are presented. A simple and exact analytical and graphical method on the Nyquist and Nichols planes for the design of lead-lag compensators satisfying design specifications on gain margin, phase margin and crossover frequency is proposed. Simulations results show the good performances of the presented method.

Power control of grid-connected photovoltaic systems

In this paper the Power Oriented Graph technique is used for modeling a grid-connected single-phase 3kW DC/AC power converter for solar energy conversion system. A DC/DC stage, controlled by a maximum power point tracking (MPPT) technique, is used to boost the time-varying input voltage provided by photovoltaic panels. A buck DC/AC stage, including a PWM inverter, is implemented to transfer the active power to the grid. A new control scheme for the DC/AC stage is proposed.

A Novel Instructional Approach to the Design of Standard Controllers: Using Inversion Formulae

This paper describes a range of design techniques for standard compensators (Lead-Lag networks and PID controllers) that have been applied to the teaching of many undergraduate control courses throughout Italy over the last twenty years, but that have received little attention elsewhere. These techniques hinge upon a set of simple formulas-herein referred to as Inversion Formulae -for the computation of the parameters of the controller as functions of the typical specifications of steady-state performance, stability margins, and crossover frequency.

New inversion formulae for PIDF controllers with complex zeros for DC-DC buck converter

This paper presents a new tracking controller design method for the widely used DC-DC buck converter involving a PIDF (i.e., PID + filter) controller. This controller, differently from the classical PID controller, has the advantage of being characterized by a proper transfer function. Secondly, the further degree of freedom introduced in the transfer function of the low pass filter can be exploited to satisfy further specifications. This new design procedure is a conjunction of the classical pole-zero cancellation method with the so-called inversion formulae design method. These two techniques are used to reduce the negative effects introduced by the complex poles in the transfer function of the converter and to exactly satisfy steady state requirements on the tracking error, as well as to meet frequency-domain specifications on the phase margin and on the gain crossover frequency. The robustness of the proposed control procedure under load variations and plant uncertainty is evaluated and compared with other methods.

On the use of inversion formulae for the synthesis of discrete PID controllers

This paper presents a new set of formulae for the design of discrete proportional-integral-derivative (PID) controllers under requirements on steady-state performance and robustness specifications, such as the phase and the gain margins, as well as the gain crossover frequency. The proposed technique has the advantage of avoiding trial-and-error procedures or approximations connected to an a posteriori discretisation. This method can also be implemented as a graphical design procedure in the Nyquist plane.