Variable speed wind turbine having a passive grid side rectifier with scalar power control and dependent pitch control

A system comprising:

• a generator side converter;
• a direct current (DC) link coupled to the generator side converter;
• a power dissipating element coupled to the DC link to selectively dissipate excess power from a generator;
• and
• a passive grid side rectifier to convert fixed frequency alternating current (AC) signals from a power grid to DC voltage,
• wherein the DC voltage is supplied to the generator side converter via the DC link and the generator side converter is to convert the DC voltage into variable frequency AC signals for the generator.

A power conversion method comprising:

• receiving power flow from a power generator;
• determining if the power generator is operating at below or above synchronous speed;
• directing the received power flow to the power generator if the power generator is determined to be operating at below synchronous speed;
• and
• dissipating excess power from the received power flow if the power generator is determined to be operating at above synchronous speed.

A variable speed wind turbine comprising:

• a electrical generator connected to wind blades for generating electrical power;
• and
• a power converter coupled to the electrical generator and to control the generated electrical power, the power converter including a generator side converter, a DC link, a power dissipating element, and a passive grid side rectifier, and
• wherein the active side generator converts DC voltage signals from the DC link into variable frequency AC signals that are supplied to the electrical generator or converts variable frequency AC signals from the electrical generator to DC voltage signals that are supplied to the DC link and wherein the power dissipating element dissipates excess power from the DC voltage signals generated by the generator side converter.

A power conversion method comprising:

• sensing a voltage level on a DC link of a power converter;
• determining if the sensed voltage level exceeds a threshold;
• and
• activating a power dissipating element in the power converter to dissipate any excess generated power if the sensed voltage level is determined to exceed the threshold.

A variable speed wind turbine comprising:

• a electrical generator connected to wind blades for generating electrical power;
• a power converter coupled to the electrical generator and to control the generated electrical power, the power converter having at least a DC link and a power dissipating element;
• and
• a controller to sense a voltage level on a DC link of a power converter, to determine if the sensed voltage level exceeds a threshold, and to activate the power dissipating element in the power converter to dissipate any excess generated power if the sensed voltage level is determined to exceed the threshold.