Capacitor Voltage Ripple Research Articles

Dead-zone digital controllers for improved dynamic response of low harmonic rectifiers

This paper introduces a simple digital control method that enables fast regulation of the output voltage in low harmonic rectifiers with power factor correction (PFC). The method is based on the use of an insensitive region, i.e., "dead-zone," in analog-to-digital conversion, for elimination of the output capacitor voltage ripple in the feedback loop. The dead-zone can either be fixed and larger than the maximum ripple magnitude, or it can be dynamically adjusted in accordance with the output load. Simple implementations of these two dead-zone controllers are shown on an experimental completely digitally controlled 250-W boost PFC operating at 200-kHz switching frequency. The experimental results show that this control method results in low current harmonics and improved load transient responses, which are significantly faster than in low-harmonic rectifiers with conventional low-bandwidth voltage-loop controllers.

Power conditioning of the output from a linear vernier hybrid permanent magnet generator for use in direct drive wave energy converters

A linear electrical generator may be used to convert the energy in sea waves directly into electrical energy. The reciprocating movement of the generator caused by the waves results in an electrical output that is variable in voltage and frequency, with a low-frequency amplitude oscillation of the same frequency as the reciprocating vertical movement of the waves. Power conditioning is required to extract the energy from the linear generator, and invert it into a mains supply of constant voltage and frequency. A type of power conditioner based on an AC/AC converter is illustrated. Inversion into the mains must take place at constant power by the power conditioner, which must therefore buffer the energy fluctuations produced by the wave energy device. The energy storage requirement for the power conditioner is derived as a function of the generated power, the reciprocating frequency of the wave energy device, the average AC/AC converter DC voltage and the capacitor voltage ripple. Results are presented for the operation of a prototype linear generator and power conditioner inverting into the three-phase supply.