Switching dc–dc converters are widely used to interface the dc output of renewable energy resources with power distribution systems in order to facilitate the use of energy at the customer side. In the case of residential photovoltaic (PV) applications, high conversion ratio is usually required, in order to adapt the low output voltages of PV modules to a dc bus voltage, while dealing with the appropriate impedance matching. In this paper, a system connected to a PV panel consisting of two cascaded dc–dc boost converters under sliding-mode control and working as loss-free resistors is studied. The modeling, simulation, and design of the system are addressed. First, an ideal reduced-order sliding-mode dynamics model is derived from the full-order switched model taking into account the sliding constraints, the nonlinear characteristic of the PV module, and the dynamics of the MPPT controller. For this model, a design-oriented averaged model is obtained and its dynamic behavior is analyzed showing that the system is asymptotically globally stable. Moreover, the proposed system can achieve a high conversion ratio with an efficiency close to 95 $\%$ for a wide range of working power. Numerical simulations and experimental results corroborate the theoretical analysis and illustrate the advantages of this architecture in PV systems.

Switched power converters are used to interface the dc output in modern distributed power generation systems, which are usually aggregated to the main grid to yield the necessary power using interconnected modules. Synthesis, modeling, and stability analysis of interconnected systems using cascaded converters working under sliding-mode control are considered in this paper. A systematic procedure to synthesize cascaded connection of dc-dc boost converters is introduced. The approach is based on making each module to behave as a suitable canonical element for power processing. Three different elements are considered, which are the dc power gyrator, the dc transformer, and the dc loss-free resistor. These canonical elements are designed by means of a sliding-mode control theory and then their dynamic behavior is studied in detail. The sliding-mode conditions for each case are derived in closed form to obtain design-oriented criteria for selecting the parameters of the system. The aforementioned canonical elements are compared to select the most suitable one for a distributed power system. Simulation results ensure the correctness of the proposed approach. Experimental measurements corroborate the theoretical predictions and the numerical simulations.

Due to nonlinear effects, Power Factor Correction (PFC) ac-dc converters working in Continuous Conduction Mode (CCM) can exhibit nonlinear phenomena such as subharmonic oscillations and chaotic regimes at the line frequency. These undesirable behaviors increase the Total Harmonic Distortion (THD) and shift the dc input line current to non null values. This results in a malfunctioning of the system or even damages caused by the increase of the temperature which can jeopardize enormously the performances and shorten the lifetime of the system. In order to avoid these problems, subharmonic line frequency instabilities must be suppressed. In this paper, a selective notch filter based controller is combined with the output voltage compensator to suppress these instabilities and to stabilize a two-stage PFC ac-dc converter. A frequency domain analysis is used to explain the control mechanism of directing subharmonic and chaotic oscillations into stable periodic motion. A detailed study of the effect of this selective filter on the dynamical behavior of the system is presented. A simple harmonic model is used to obtain the control stability domain. This control technique is simple and allows widening the stability domain and improving the performances of the system being its experimental implementation possible using standard devices such as OAs and passive elements. The correctness of the proposed technique is verified with numerical simulations and experimental measurements.

A unified approach for the stability analysis of both preregulator and two-stage power factor correction (PFC) ac-dc converters is presented. Practical and accurate analytical expressions for the stability boundary are obtained by studying the dynamics of the first harmonic component. The resulting model of this dynamics has an equilibrium point at the origin of the harmonic state space. In the case of a stable equilibrium point, the first-order component converges to zero, and the system oscillates at twice the line frequency. If the equilibrium point loses stability, another equilibrium point depending on high-order harmonics will be reached while the real system will exhibit a period-doubling phenomenon leading to subharmonic oscillations. It is demonstrated that the stability boundaries depend on the power level. Numerical simulations and experimental results in both a preregulator and a complete two-stage PFC converter validate the approach.

This article focuses on analyzing the fast-scale stability in a peak current-mode-controlled boost converter with a constant power load (CPL). Since with this kind of nonlinear loads the analytical expression of the discrete-time model is not available and the existing averaged models are inadequate in describing accurately the fast-scale dynamics of these converters, a piecewise linear switched model is established by approximating the CPL by a composite linear load. The model is first demonstrated to predict accurately the same bifurcation points predicted by the switched model using the nonlinear load. The bifurcation analysis using the Floquet theory and the resulting monodromy matrix and its eigenvalues loci clearly show the effect of system parameters on its stability. The fast-scale stability boundaries in terms of suitable parameters are obtained by using eigenvalues analysis. The effect of the proportional gain of the voltage controller is studied. Finally, experimental results are further given to verify the theoretical analysis and simulation results obtaining a good agreement.

This paper analyzes for the first time a two-loop sliding-mode control (SMC) of a high-order converter supplying a constant power load (CPL). The converter is a single-switch quadratic buck structure (QBC) interfacing a domestic 380 V DC bus to a CPL requiring a regulated voltage of 48 V DC. The converter is unstable in the absence of control and even after the insertion of an inner loop based on SMC of the input inductor current. The addition of an appropriate linear outer loop establishing the reference to the inner loop stabilizes the system and provides output voltage regulation. The regulated QBC shows a fast recovery of the output voltage with negligible overshoot in response to step-type changes of the output power or the input voltage. It is also shown that the implemented regulator for CPL supply can be used directly in the case of a constant current load (CCL) or a constant resistance load (CRL) resulting in similar performance to the CPL case. PSIM simulations and experimental results in a 400 W prototype are in good agreement with theoretical predictions.