Discrete‐time sliding‐mode‐based digital pulse width modulation control of a boost converter

Abstract

In this study, a non-linear digital control of a boost converter based on a sliding discrete-time approximation is presented. The control strategy follows a classical cascade regulation scheme with the inner loop consisting in a nonlinear current-control based on discrete-time sliding mode, and the outer one being composed of a simple discretetime proportional-integral (PI) controller for output voltage regulation. An analytical expression of the current control law is developed using a simplified discrete-time small-signal model of the boost converter. The discrete-time PI compensator is designed from a discrete-time small-signal parametric model of the inner loop obtained by linearisation around the desired equilibrium point. The proposed method is initially based on the notion of discretetime sliding motion to eventually derive a pulse width modulation (PWM) controlled system. Thus, the reported approach can be categorised not only as a direct digital design technique for voltage regulation but also as a competitive method to design sliding-mode-based PWM controllers. Simulated and experimental results in a boost converter operating in continuous conduction mode verify the theoretical predictions.

Fixed Switching Frequency Digital Sliding-Mode Control of DC-DC Power Supplies Loaded by Constant Power Loads with Inrush Current Limitation Capability

“…The output voltage will collapse if the current reference is smaller than P/V g . This fact appears in a clear contrast with the case of resistive load for which the voltage reaches a finite value in steady state when the system is under pure current-mode control [38]. The case studied here is similar to the analog control based on the average inductor current regulation in a buck converter loaded by a CPL, which is still unstable after the introduction of the current control loop [3].…”

“…Fixed frequency DSMC technique has only very recently appeared in the power electronics field. The application of DSMC theory [37] has used first the discrete-time representation of the converters dynamics and subsequently has been used as a natural technique to analyze and to digitally implement SMC-based controllers with fixed-frequency PWM, which were validated in classical two-loop control strategies such as in [38,39] and in the synthesis of a discrete-time loss-free resistors for AC-DC PFC applications [40].…”

“…Fixed-frequency digital control of DC-DC converters with CPL has not been addressed as far as the authors are aware. Direct application of the results in [38], is not possible because the discrete-time model cannot be obtained in closed form without approximations. Here, a direct digital control design is provided by first deriving an approximate discrete-time model which is demonstrated to faithfully predict the dynamics of the exact switched system.…”

Qualified Analysis of DSMC over SMC for Boost Converter

“…When S1 is OFF the system is represented by the following equations (3,4) (3) (4) Using KVL the loop equations are formed, from that we can write (5) (6) The sliding surface is given by (7) Where x1 is the inductor current and x2 is the output voltage, e1 is the voltage error, e2 is the current error [6,7].…”

“…The DSMC is introduced which eliminates the need for ADC, has flexible control algorithm, ease of implementation, reduced ripples in the output so that the efficiency of the system is improved [3,4]. Figure 1 shows the block diagram description of SMC/DSMC.…”