A method for controlling a three-level back-to-back voltage source power conversion assembly includes receiving an indication of a DC or AC unbalance occurring in voltage of a DC link. The power conversion assembly has a first power converter coupled to a second power converter via the DC link. In response to receiving the indication, the method includes activating a balancing algorithm that includes determining a deviation of a midpoint voltage of the DC link as a function of a total voltage of the DC link, calculating a voltage compensation needed for pulse-width modulation signals of the power conversion assembly based on the deviation, and coordinating common mode voltage injection from each of the power converters independently at a neutral point of the power conversion assembly based on the voltage compensation, thereby minimizing the at least one of the DC unbalance or the AC unbalance at any given operating condition.

Described is a system that includes a polyphase generator and a polyphase bridge rectifier electrically coupled to an output of the polyphase generator. The polyphase bridge rectifier may output a positive rectified ripple signal and a negative rectified ripple signal, and the positive rectified ripple signal and the negative rectified ripple signal may be summed to produce a total ripple signal. Further, the system may include a generator regulation feedback control loop that regulates the output of the polyphase generator with a field control signal. In an embodiment, the field control signal is based on summing the total ripple signal and a reference voltage.

A method of controlling a power generation system following a transient grid event, and a system and controller to control the power generation system are described. The method includes sensing a rate of change of electrical frequency at terminals of a generator, determining a rate of change of shaft line acceleration, and identifying the transient grid event based on the rate of change of shaft line acceleration. The method also includes triggering an action to recover from the transient grid event when the rate of change of electrical frequency exceeds a first specified value and the rate of change of shaft line acceleration exceeds a second specified value for a specified duration.

A method for controlling a multi-phase rotary electric machine is disclosed. The stator of the machine is controlled by a control bridge having a plurality of parallel mounted switching arms, with each arm comprising a high-side switch and a low-side switch connected at a center tap connected to a phase of said rotary electric machine. The machine operates as a generator and is connected to an electrical network on board a motor vehicle. The method involves short-circuiting a phase winding of the stator when a measurement of the voltage of said network exceeds a first predetermined value, and after this, activating a switching arm, the center tap of which is connected to said at least one short-circuited phase winding, during which the intensity in the short-circuited winding is measured, if the measured intensity is positive, the high-side switch of said activated switching arm is moved to the closed position, otherwise, it is moved to the open position.

A system configured to deliver as output a polyphase current of constant frequency from a synchronous generator driven at variable speed. The system includes, at the output of the generator, an AC-to-DC active rectifier including one arm per phase of the current, a DC bus and a DC-to-AC inverter for the output including one arm per phase of the current, the inverter or the DC bus including an arm connected to the neutral, each arm including a controllable switch, the system including an electronic control unit driving the rectifier and including means for tracking a voltage for the rectifier and/or the inverter and means for controlling the inverter, the system including an EMC filter including one arm for each phase of the current, each arm including an inductor, a capacitor connected in a bypass downstream of the inductor, the arm connected to the neutral being connected to each bypass.

This disclosure is directed to a method for operating a wind turbine which includes a speed-variable drive system. The system includes an electrical machine and a pulsewidth modulation-controlled converter. The speed-variable drive system is connected to an electrical grid. In the event of a transient grid fault, a frequency of the pulsewidth modulation is determined in response to a current in an electrical circuit connected to the converter.

A hydroelectric power generation system includes: a generator driven by the hydraulic turbine; a head adjuster adjusting an effective head of the hydraulic turbine; and a controller cooperatively executing: flow rate control for controlling the generator such that a flow rate in the hydraulic turbine is brought close to a target flow rate; and head adjusting control for adjusting the effective head of the hydraulic turbine using the head adjuster such that the effective head of the hydraulic turbine falls within a first range.

An arrangement for controlling a DC-link-voltage of a DC-link-connected between a generator side converter portion and a utility grid side converter portion of a wind turbine includes:

a generalized predictive control module adapted: to receive as control module input values a current value of the DC-link-voltage and a reference value of the DC-link-voltage and to derive a reference value of a DC current based on the control module input value, the reference value of a DC current defining the DC current to be injected into the DC-link, wherein the arrangement is adapted to control the generator side converter portion and/or the utility grid side converter portion based on the reference value of the DC current.

The invention related to a control method for operating a synchronous machine, the machine comprising an exciter connected to a synchronous generator and a controller (40) for controlling the machine field excitation. The method comprises the steps of predefining a stable operation torque derivative range within which a stable operation of the machine occurs, performing a torque measuring or calculating for the machine, calculating the derivative of said torque, determining whether the calculated torque derivative is within the predefined stable operation torque derivative range for the machine, and, if the torque derivative is not within the predefined stable operation torque derivative range, modifying the machine field excitation to bring the torque derivative within the predefined stable operation torque derivative range.

A system contains a double fed induction machine having a stator and a rotor, a fly wheel coupled to the rotor, and a control device for providing a rotor voltage and a rotor current to the rotor. The control device is connected to the rotor and the stator and is capable of generating the rotor voltage and rotor current in response to an electrical signal that is applied to the stator. The control device has a multilevel converter and a control unit for controlling the multilevel converter.