This paper presents the detailed design of an active damping system for the stabilization of an open-loop boost converter in constant-power load (CPL) operation. The reported work analyzes the steady-state regime of the interconnection of a boost converter supplying a CPL, and a loss-free resistor (LFR) in series with the converter input port (SLFR) performing the active damping. The LFR behavior is obtained by peak current mode control (PCMC) imposing proportionality between the steady-state average values of current and voltage in the SLFR input port. The isolated SEPIC fulfills the topological constraints of the interconnection and is selected to implement the SLFR. Finally, PSIM simulations and measurements from a 500 W prototype are in good agreement with the theoretical predictions and illustrate the system stabilization around the specified steady-state operating point for different values of the CPL power.

Modern DC-DC power conversion represents an important challenge because connected loads are not purely resistive as it has been conventionally considered. Furthermore, the corresponding power converters perform functions which are not limited to regulate either a specific output voltage or output current. One of these new functions is the transfer of a regulated power to different types of loads, which emerge in the context of microgrids and electric vehicles, in which the sliding-mode control (SMC) is an important actor because of its versality, robustness and systematic design. This paper presents SMC of a boost converter operating as a loss-free resistor (LFR), which supplies a constant power to the parallel connection of three canonical elements, namely, a constant power load (CPL), a constant current load (CCL) and a dc voltage source with internal resistance. The studied load is defined as a generic nonlinear static load (GNSL). The subsequent analysis of the connection of the controlled power converter and the GNSL reveals the existence of a single equilibrium point, which is unconditionally stable. This feature is preserved when the GNSL is particularized in the single load cases of battery, current source or resistor, and in all cases of two-element and three-element load combinations. The exception is the supply of a single CPL, which results in an infinite number of equilibrium points with marginally stable behavior. Simulation and measurements in a 1 kW prototype are in perfect agreement with the theoretical predictions.

This paper presents a systematic approach to synthetize constant power loads using switching converters under sliding-mode control. The generation of sliding motions is analyzed in converters with a series inductor in the input port and a switching function representing the error between the input power and a suitable power reference. The analysis establishes the existence conditions for sliding-mode and the stability of the resulting ideal dynamics. Simulation and experimental results verifying the theoretical predictions in boost, Ćuk and SEPIC converters illustrate the proposal. The design procedure yields a simple, economical and small-size prototype that can be useful in the experimental validation of converters supplying constant power loads.

The significant improvements that have been recently achieved in HBLEDs technology in terms of lifetime, luminous efficacy, and power rating, make these devices one the most promising candidates to replace conventional light sources in various residential and industrial applications, despite their high cost. The efficiency requirement should be completed by means of the voltage conversion stage by performing Power Factor Corrector. In this paper we consider the problem of Power Factor Corrector and output current regulation for a group of HBLEDs by using a Ćuk converter under a Sliding-Mode Control which must be ultimately implemented by a hysteretic comparator to limit the switching frequency to practical values. However, with a constant hysteresis width, the system exhibits harmful harmonic distortion in the input line current waveform. Therefore, a variable hysteresis window is used thereby avoiding this distortion near the zero crossing of the input current. Using the Ćuk converter under a Sliding-Mode Control with variable hysteresis window, the converter will be forced to behave as a Loss Free Resistor. Simulation and experimental results are presented in this paper to demonstrate the functionality of the proposed technique.

In this paper, a system consisting of two cascaded dc-dc boost converters under sliding-mode control, working as loss free resistors, connected to a PV panel 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 and stability analysis is carried out. It is shown that the cascade connection of boost-based loss free resistors can be a good solution for the impedance matching in PV systems with the standard 380 V dc bus voltage.

In this work a Loss-Free Resistor (LFR) based on a semi-bridgeless boost rectifier is synthesized using sliding mode control. A better efficiency can be obtained from bridgeless boost converters because of their reduced conduction losses in comparison the traditional PFC boost converters. Although different bridgeless topologies have been presented, the semi-bridgeless topology presents less common-mode noise and its practical implementation is more suitable. Sliding mode control is proposed to achieve a LFR behaviour and, therefore, its application in power factor correction is possible.

The synthesis of a Digital Loss-Free Resistor (DLFR) based on a boost converter in Pulse-Width-Modulation (PWM) operation is presented. The proposed control law is obtained by applying discrete-time sliding mode control theory on the discrete-time model of the boost converter to control the input current. The control law calculates the duration of the switch on-time at the beginning of each switching period in order to reach the proposed discrete-time sliding surface. The resulting digital Loss-Free Resistor (DLFR) can be used as a preregulator for power factor correction in one-phase circuits. Simulations are in good agreement with theoretical predictions.

Microgrids consist of distributed electrical generation architectures which have some instability problems due to the cascade interconnection of the converters and their related negative impedance effect. In electric power distribution system, a point of load converter behaves as constant power load (CPL) which result in a well known destabilizing effect. In this paper, different strategies that have been used to eliminate this undesirable behavior will be discussed. Then, an alternative approach based on sliding mode control (SMC) and using canonical elements for power processing will be proposed to stabilize cascaded converters. The proposed approach will be illustrated using a system consisting of two cascaded boost converters behaving as Loss Free Resistors (LFR) supplied from a PV panel and connected to a 380 V dc bus of a microgrid. It will be shown that using LFRs and SMC could be a good strategy to stabilize cascaded boost converters. The theoretical results are verified using simulations and experimental measurements.

In this paper a SEPIC converter, operating as an AC-DC adaptation stage, is studied. It is shown that the system has high efficiency and good power factor being able to work both as a boost (step-up) or buck (step-down) converter. To impose a loss free resistor (LFR) behavior, sliding-mode control is applied. It is shown that the LFR acts as an ideal rectifier with a power factor near the unity. The output of the system is used to power supply a group of HBLEDs, and its brightness (luminosity) is controlled by the output current. The design and the models are validated by mathematical, numerical and experimental results.

The synthesis of a boost-converter-based loss-free resistor (LFR) operating in PWM is presented. The resulting LFR can be used as a preregulator for power factor correction in one-phase circuits. PSIM simulations are in good agreement with the theoretical predictions.