The negative impedance caused by constant power load (CPL) may lead to the instability of overall power system. In this paper, the regulation problem of output voltage of DC-DC converters subject to unknown CPLs is addressed. Our main contribution of this paper is to design an adaptive energy shaping control (ESC) algorithm, which combines passivity theory with immersion and invariance (I&I) technology, to stabilize DC-DC buck converter and boost converter with CPLs, respectively. Three nice features of proposed control method are that (i) the stability analysis and controller design are based on large signal model, (ii) the proposed control scheme is implemented without needing the knowledge of power load and (iii) the estimation of domain of attraction is presented to guarantee strictly the asymptotic convergence of closed-loop system. The performance of the proposed controller is assessed via detailed simulation and experimental results.

It is known that constant power load (CPL) may cause a negative impedance, which seriously affects the stability of power system. In this paper, a new control algorithm for DC–DC buck converter feeding unknown CPL is proposed. First, under the assumption of known extracted power load, the standard passivity–based control (PBC) is presented to reshape the system energy and compensate for the negative impedance and a proportion‐integration (PI) action around passive output is added to improve disturbance rejection performance, which forms the PBC plus PI (PBC+PI). Then, a parameter estimation algorithm is developed, based on immersion and invariance (I&I) technique, in order to online estimate the extracted power load. In the next step, the online estimation scheme is adopted to construct an adaptive strategy. Finally, the stability analysis of the cascaded system containing a closed‐loop control system and observer error dynamics is conducted. Simulation and experimental results are demonstrated to validate the performance of the proposed controller.

In this article, the sensorless control problem of a large class of power converters with unknown load conductance is investigated. A reduced-order generalized parameter estimation-based observer (GPEBO) is presented to reconstruct the unmeasurable states and estimate the unknown load conductance of the system. Three nice features of this observer are as follows: finite-time convergence (FTC) is guaranteed, an alertness preservation is imposed to be able to estimate a possibly time-varying load, and the required excitation condition is very weak and can be satisfied in normal operation of power converters. Then, replacing the estimated states and parameter, in a certainty equivalent manner, in a PI passivity-based controller, a sensorless control scheme is proposed to stabilize the systems with exponential convergence. By virtue of the FTC property of the GPEBO, the global exponential stability of the overall closed-loop system is established. Simulation and experimental results of the proposed controller with application to the boost and Ćuk converters are given to assess its effectiveness.