ACTIVE RECTIFIER FOR DOWNHOLE APPLICATIONS

摘要

An apparatus for generating direct current (DC) electrical energy downhole at a selected voltage includes a drill tubular, a turbine to convert drilling fluid flow energy into rotational energy, an alternator coupled to the turbine to provide AC electrical energy, and an active rectifier configured to rectify the AC electrical energy into DC electrical energy at a controllable voltage. The active rectifier includes (a) a bridge circuit having a circuit branch having first and second rectifier sets including a semiconductor switch in parallel with a diode for each phase of the AC electrical energy and (b) a feedback control loop having a micro-processor and configured to receive an output voltage measurement and a voltage measurement and/or a current measurement in at least one circuit branch as an input and to provide a control signal to each semiconductor switch in order to provide the DC electrical energy at the selected voltage.

主权项

1. An apparatus for generating direct current (DC) electrical energy downhole at a selected voltage, the apparatus comprising:
a drill tubular configured to drill a borehole penetrating the earth; a turbine coupled to the drill tubular and configured to convert energy of drilling fluid flowing through the drill tubular into rotational energy of the turbine; an alternator configured to convert the rotational energy of the turbine into alternating current (AC) electrical energy; and an active rectifier coupled to the alternator and configured to rectify the AC electrical energy into DC electrical energy at a controllable voltage, the active rectifier comprising (a) a bridge circuit comprising a circuit branch for each phase of the AC electrical energy, each circuit branch comprising a first rectifier set and a second rectifier set with a connection to the alternator between the first rectifier set and the second rectifier set, the first rectifier set comprising a semiconductor switch having power conducting terminals in parallel with a diode and configured to control a voltage across the first rectifier set, the second rectifier set comprising a semiconductor switch having power conducting terminals in parallel with a diode and configured to control a voltage across the second rectifier set and (b) a feedback control loop comprising a micro-processor, the feedback control loop being configured to receive an output voltage measurement and a voltage measurement and/or a current measurement in at least one circuit branch as an input and to provide a control signal to each semiconductor switch in order to provide the DC electrical energy at the selected voltage.