Unconstant Frequency Dual Integrator Control and its Application to Switch Converters

In this paper, a new large-signal nonlinear control technique, called unconstant frequency dual integrator control - UFDI control, is proposed to control the duty-ratio d_k and cycle T_k of a switch such that in each integration cycle T_k the impulse value of a switched output variable is exactly equal to or proportional to the control reference in the steady-state or in a transient. UFDI control rejects power source perturbations within one integration cycle T_k; the switched output variable exactly follows the dynamic reference in one integration cycle; and there is no steady-state error nor dynamic error between the switched output variable and the reference in one integration cycle. UFDI control appears a very good tracking performance. Simulations with UFDI control of a single-phase bridge inverter have demonstrated the new control method and verified the theoretical predictions. This new control method is general and applicable to all types of pulse-width-modulated, or converters for either voltage or current control in continuous or discontinuous conduction mode

1. Introduction

Switch circuits such as various power switching inverters are usually pulsed nonlinear dynamic systems. Such systems under proper pulsed nonlinear control should have faster dynamic response, and provide better rejection of power-source perturbation than the same systems under linear feedback control [1]. There has been a continuous effort in the control community and the power electronics community to search for large-signal nonlinear schemes to control switching circuits or converters.