S. Oucheriah^* and A. Azad

Department of Engineering Technology, Northern Illinois University, DeKalb, Illinois, United States

Submitted on 22 April 2025; Accepted on 19 May 2025; Published on 21 May 2025

To cite this article: S. Oucheriah and A. Azad, “Robust Nonlinear Controllers for the Boost Converters with Constant Power Loads,” Insight. Electr. Electron. Eng., vol. 2, no. 1, pp. 1-7, 2025.

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Abstract

The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL, presenting a major challenge in the design of stabilizing controllers. In this note, three different types of stabilizing controllers to regulate the output of the DC-DC boost converter driving a CPL are discussed and compared through simulations.

Keywords: boost converter; robust sliding mode control; constant power load; current-sensorless control; extended state observer

Abbreviations: CPL: constant power load; CCM: continuous conduction mode; UDE: uncertainty and disturbance estimator

1. Introduction

Nowadays, power electronic converters are extensively used in power distribution systems and are often cascaded. Some of these converters operate as tightly regulated loads that absorb constant power and behave as constant power loads (CPLs). These loads exhibit negative incremental impedance, which can lead to serious destabilizing effects on the input source, often another DC-DC converter, and present a major challenge in the design of robust stabilizing controllers for the supply converters.

Numerous design techniques have been published in the literature to regulate the output voltage of DC-DC converters to counter the instability effects caused by CPL-induced negative impedance [1–12]. Some shortcomings of these controller designs are

1. Controllers that are interesting from a theoretical point of view but are very complicated and strongly dependent on precise knowledge of the converter parameters to be of any practical interest in real applications.
2. Controllers that require numerous sensors for their implementation.
3. Controllers that are simple to implement but are not tested for their robustness to parameter uncertainties, parasitics, unmodeled dynamics, and external disturbances.
4. Most of the controllers listed above assume only the load power to be unknown.

The effectiveness and performance of a controller on the output response of a converter depend on its accurate modeling. Ignoring parasitics, parameter uncertainties, component value tolerances, unknown time-varying input voltages, and output load power disturbances in the design of the controller may result in degradation of the output response. In this case, the converters may suffer from substantial steady-state errors with large output variations when subjected to large unknown time-varying external disturbances.

In the context of the boost converter driving a CPL, and to the best of this author’s knowledge, only the controllers proposed in [13] and [14] take into account unknown parameter uncertainties, unknown parasitics, unknown component value tolerances, and unknown time-varying input voltages and load powers. In addition, these two controllers are simple, easy to design, and can be implemented with analog devices. The three controllers proposed in [6], [13], and [14] are discussed and compared using MATLAB/Simulink simulations.

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