This paper presents the practical implementation of a fully digital control for boost power factor preregulators (PFPs). The control algorithm, which is simple and fast, provides a significant improvement in the system's dynamic performance compared to the usual analog control techniques. The paper discusses the design criteria and the actions taken for the implementation of the digital control, which is performed by means of a standard microcontroller (Siemens 80C166). The effectiveness of the approach is assessed by experimental tests.

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Simple digital control improving dynamic performance of power factor preregulators

With the emerging installations of multitype renewable energy sources and energy storage elements, the dc electronic distribution systems in residential buildings (dc nanogrid) are becoming an alternative future system solution, achieving a zero net-energy consumption and optimized power management. The concept of the energy control center (ECC), which interconnects the dc system to the traditional ac utility grid, is introduced, and the operation function of ECC converter suitable for dc nanogrid application is defined. This paper investigates a two-stage topology using a full bridge in series with a bidirectional synchronous rectifier dc–dc converter as a single-phase ECC for dc nanogrid, with a significant reduction of the dc-link capacitor value. The operation analysis and the design of passive components are provided. A bidirectional control system and the design process are also presented in terms of the system requirement and the small dc-link capacitor.

Grid-Interface Bidirectional Converter for Residential DC Distribution Systems—Part One: High-Density Two-Stage Topology

The aspects regarding control strategies for Power Factor Correction (PFC) converters are investigated. The major control techniques to absorb sinusoidal input currents in boost PFC's are reviewed and analyzed. Their extension to other converter topologies is discussed and some experimental results for a PFC based on the Sepic topology are reported, which allow comparison of converter performance with different control techniques. Lastly, some considerations regarding dynamic operation are given, together with information about control IC's specifically developed for PFC applications.

Control techniques for power factor correction converters

The boost power-factor-correction (PFC) converter with average-current-mode control is a nonlinear system due to the effects of the multiplier and a large variation of the duty ratio. Although its stability analysis must be studied depending on a nonlinear model, most prior research attempted to make some assumptions to force this nonlinear system to be linear. As a result, the practical dynamics and the nonlinear phenomena were disregarded. In this paper, two kinds of nonlinear phenomena are detected under the conditions that are considered to be stable by the prior criteria: one is period-doubling bifurcation and the other is chaos. Stability maps and phase-plane trajectories are introduced at different loads to clarify the power factor and also the instability regions. It is clear that the output storage capacitor is a main contributing parameter on the system stability, therefore, bifurcation maps are developed to determine the accurate minimum output capacitance value that assures the system stability under all operating conditions. Also, PFC converter stability is explained and judged by comparing the consequence of charging and discharging energy in the output capacitor.

Nonlinear dynamics of power-factor-correction converter

This paper introduces a new method for stability analysis and design of fast voltage-loop compensators in rectifiers with power factor correction (PFC). The method has few constraints and can be used with various implementations of the fast voltage loop. It is based on utilization of circle criterion, which unifies frequency domain and nonlinear system analysis. A step-by-step procedure of stability assessment and compensator design is described and demonstrated on two controller implementations. In the first system, the voltage-loop dynamic response of an experimental 200-W digitally-controlled boost-based PFC is improved with a self-tuning comb filter. In the second implementation, it is shown how the circle criterion can be used to design a fast voltage loop for controllers with regulation band, i.e., ldquodead-zone,rdquo element for ripple elimination.

R. Ridley

Papers

Average small-signal analysis of boost power factor correction circuit