Back to results
US 8,577,508 B2Granted
Converter control of variable-speed wind turbines
AssigneeUniversity of Alabama
InventorsShuhui Li, Timothy A. Haskew
Life of this patent
Estimating the term…
Abstract
Embodiments according to the present invention provide methods and a system for a control approach that effectively maintains the DC link voltage at a constant set value under variable system conditions and keeps the converter operating within an optimal power factor range.
Claims8
A method of controlling a variable-speed wind-turbine comprising:
- providing an AC/DC/AC PWM frequency converter comprised of a machine-side self-commutated PWM converter, a DC-link, and a grid-side self-commutated PWM converter, wherein the machine-side self-commutated PWM converter is operably connected to the wind turbine and the grid-side self-commutated PWM converter is operably connected to an electrical grid and the DC-link interconnects the machine-side self-commutated PWM converter and the grid-side self-commutated PWM converter;
- providing a control system operably connected to the AC/DC/AC PWM frequency converter, wherein the control system is comprised of a DC-link voltage controller and a reactive power controller;
- providing a q-axis control voltage, Vcq, to the control system, wherein Vcq is used by the DC-link voltage controller to control voltage of the DC-link and Vcq is determined by comparing a DC-link voltage reference value to a measured DC-link voltage value;
- providing a d-axis control voltage, Vcd, to the control system, wherein Vcd is used by the reactive power controller to control reactive power absorbed from the electrical grid by the grid-side self-commutated PWM converter and Vcd is determined by comparing a reactive power reference value to a measured reactive power value;
- and
- injecting, by the grid-side self-commutated PWM converter, a voltage into the electrical grid, wherein the injected voltage is less than Vdc/2√{square root over ( )}2, where Vdc is the measured DC-link voltage value.
3 more elements
A system for controlling a variable-speed wind-turbine comprising:
- an AC/DC/AC PWM frequency converter comprised of a machine-side self-commutated PWM converter, a DC-link, and a grid-side self-commutated PWM converter, wherein the machine-side self-commutated PWM converter is operably connected to the wind turbine and the grid-side self-commutated PWM converter is operably connected to an electrical grid and the DC-link interconnects the machine-side self-commutated PWM converter and the grid-side self-commutated PWM converter;
- and
- a control system comprised of a DC-link voltage controller and a reactive power controller operably connected to the AC/DC/AC PWM frequency converter,
- wherein the DC-link voltage controller compares a DC-link voltage reference value and a measured DC-link voltage value and determines a q-axis control voltage, Vcq, where Vcq is used by the DC-link voltage controller to control voltage of the DC-link,
- wherein the reactive power controller compares a reactive power reference value to a measured reactive power value and determines a d-axis control voltage, Vcd, where Vcd is used by the reactive power controller to control reactive power absorbed from the electrical grid by the grid-side self-commutated PWM converter,
- wherein the grid-side self-commutated PWM converter injects a voltage into the electrical grid, and the injected voltage is less than Vdc/2√{square root over ( )}2, where Vdc is the measured DC-link voltage value.
3 more elements
Dependencies are inferred from the claim text.