Wind turbine transformer control

A wind turbine electrical system comprising:

• a transformer comprising a primary side with a primary winding configured to be coupled to a power grid and a secondary side with a secondary winding configured to be coupled to an electrical power generating system of the wind turbine, wherein the wind turbine transformer further comprises an electronic on-load tap changer, wherein the electronic on-load tap changer comprises semiconductor switches that are connected and configured such that by controlling the semiconductor switches, a turns ratio of the primary winding to the secondary winding of the wind turbine transformer is adjustable to compensate for voltage changes on the primary side and/or the secondary side of the wind turbine transformer;
• and
• a control system coupled to the electronic on-load tap changer to control the turns ratio, wherein the control system comprises a converter controller of a converter of the wind turbine electrical system, wherein the converter controller is configured to control the electronic on-load tap changer, wherein the control system is configured to perform:
• monitoring a voltage on the primary side of the wind turbine transformer, a voltage on the secondary side of the wind turbine transformer, or both;
• and
• in direct response to a change in the monitored voltage, automatically controlling the semiconductor switches of the electronic on-load tap changer to adjust the turns ratio of the wind turbine transformer to compensate for the change in the monitored voltage, wherein compensating for the change in the monitored voltage includes adjusting the turns ratio of the transformer so as to keep the voltage on the secondary side of the transformer within a predetermined voltage range, wherein compensating for the change in the monitored voltage is independent of a current reference and/or is independent of current monitoring;
• wherein the electronic tap changer comprises at least one, or at least two tap changer modules,
• wherein each tap changer module comprises a first arm connected at one end to a first tap of the primary winding and/or the secondary winding and a second arm connected at one end to a second tap of the primary winding and/or the secondary winding, wherein the other ends of the first and second arms are connected together at a connection point, wherein each arm comprises at least one semiconductor switch to switch on and off a current path via the respective tap, and wherein at least one of the arms comprises a changeover impedance connected in series with the semiconductor switch;
• and
• wherein the tap changer module further includes a third arm connected at one end to a third tap of the primary winding and/or the secondary winding and at its other end to the connection point, the third arm comprising a semiconductor switch to switch on and off a current path via the third tap,
• wherein in at least two of the three arms, a changeover impedance is connected in series with the respective semiconductor switch.

A wind turbine electrical system comprising:

• a transformer comprising a primary side with a primary winding configured to be coupled to a power grid and a secondary side with a secondary winding configured to be coupled to an electrical power generating system of the wind turbine, wherein the transformer further comprises an electronic on-load tap changer, wherein the electronic on-load tap changer comprises semiconductor switches that are connected and configured such that by controlling the semiconductor switches, a turns ratio of the primary winding to the secondary winding of the wind turbine transformer is adjustable to compensate for voltage changes on the primary side and/or the secondary side of the wind turbine transformer;
• and
• a control system coupled to the electronic on-load tap changer to control the turns ratio, wherein the control system comprises a converter controller of a converter of the wind turbine electrical system, wherein the converter controller is configured to control the electronic on-load tap changer, wherein the control system is configured to perform:
• monitoring a voltage on the primary side of the wind turbine transformer, a voltage on the secondary side of the wind turbine transformer, or both;
• and
• in response to detecting a change in the monitored voltage, automatically controlling the semiconductor switches of the electronic on-load tap changer to adjust the turns ratio of the wind turbine transformer to compensate for the change;
• wherein the electronic tap changer comprises at least one, or at least two tap changer modules,
• wherein each tap changer module comprises a first arm connected at one end to a first tap of the respective transformer winding and a second arm connected at one end to a second tap of the respective transformer winding, wherein the other ends of the first and second arms are connected together at a connection point, and wherein the tap changer module further includes a third arm connected at one end to a third tap of the respective transformer winding and at its other end to the connection point, wherein in at least two of the three arms, a changeover impedance is connected in series with the respective semiconductor switch.