The invention relates to a system for generating electric power, comprising: an alternator (1) for coupling with a drive system (7), supplying an AC voltage to an output bus (10); a reversible AC/DC converter (2) in which the AC bus (6) is connected to the output bus (10) of the alternator (1); an electricity-storage element (3) connected to the DC bus (9) of the converter (2); a controller (4) arranged to react to a transient state of load-shedding or charging impact by controlling the converter (2) so as to collect energy on the output bus (10) of the alternator (2) and to store same in the storage element (3) in the case of load-shedding, and to collect energy in the storage element (3) and to inject same into the output bus (10) in the case of charging impact, the converter (2) being controlled so as to inject currents to compensate for harmonic currents into the AC bus (10) of the alternator (1).

A reactive power compensation apparatus includes one or more phase clusters each comprising a plurality of cells, and a controller controlling the one or more phase clusters. When at least one cell in a specific phase cluster among the one or more phase clusters is faulty, the controller controls a voltage of each cell in each of the remaining phase clusters except for the specific phase cluster to be controlled, using a modulation index.

An energy storage system (ESS) for an electrical system includes an energy storage, and a converter interface arranged for connecting the energy storage to the electrical system. The converter interface includes a modular multilevel converter in which each phase leg includes a plurality of series connected cells of which at least one is a half-bridge cell and at least one is a full-bridge cell.

A reactive power compensation apparatus includes one or more phase clusters each comprising a plurality of cells, and a controller controlling the one or more phase clusters. When at least one cell in a specific phase cluster among the one or more phase clusters is faulty, the controller controls a voltage of each cell in each of the remaining phase clusters except for the specific phase cluster to be controlled, using a modulation index.

A static synchronous compensator device connected between a source and a load of a three-phase power system, comprising: a main feedback line configured to provide a main feedback signal from lines between the source and the load; a mixer configured to mix the main feedback signal with a balance function to generate a balanced signal; a signal controller configured to convert the balanced signal to a controlled signal; a gain circuit configured to multiply the controlled signal by 1 and to perform proportional gain and integral gain (P & I) processing on the controlled signal to generate an intermediate correction signal; and a pulse width modulator configured to apply a pulse width modulation pattern to modulate the voltage source inverter to generate an AC waveform that is applied to the lines between the source and the load.

An arrangement includes at least one series circuit having at least two series-connected submodules and an inductor. At least one of the submodules in one or a plurality of the series circuits has a step-up/step-down converter and a storage module. A protective module with at least one actuator is electrically connected between the step-up/step-down converter and the storage module. A method for operating the arrangement is also provided.

An electric power conversion device includes a first arm and a second arm each including converter cells. The converter cell of the first arm is a first converter cell having a full-bridge configuration including an energy storing element and semiconductor switching elements. The converter cell of the second arm is a second converter cell having a half-bridge configuration including an energy storing element and semiconductor switching elements. Thus, short-circuit current between DC terminals is suppressed.

A method for reducing lower order harmonics of a multi-level power converter includes at least one phase leg including a plurality of chain-link connected cells each including a capacitor. The method includes, for each phase leg of the converter: obtaining a present reference voltage for use during a present half switching duration; dividing the half switching duration into a plurality of time samples; and at the beginning of each time sample: predicting the reference voltage waveform for the remainder of the half switching duration based on the obtained present reference voltage; predicting the leg output voltage waveform for the remainder of the present half switching duration for the case that no cell is inserted or bypassed in the leg during the time sample, and for the case that one cell is inserted or bypassed in the leg during the time sample; predicting the flux error at the end of the present half switching duration for each of the cases, based on the obtained present reference voltage, the predicted reference voltage waveform and the predicted leg output voltage waveforms; and determining whether to insert or bypass the cell, during the time sample, based on the predicted flux errors.

An electrical apparatus comprises a chain-link converter which includes a plurality of chain-link sub-modules each of which is operable to provide a voltage source. The electrical apparatus also includes a switching control unit to control the chain-link sub-modules. The switching control unit is operatively interconnected with each chain-link sub-module by an electromagnetic radiation conduit. The length of the electromagnetic radiation conduit between the switching control unit and at least one chain-link sub-module differs from the length of the electromagnetic radiation conduit between the switching control unit and at least one other chain-link sub-module. The switching control unit is configured to discern a difference in the time taken for an electromagnetic signal to propagate through each different-length electromagnetic radiation conduit to thereby identify the or each chain-link sub-module associated with each different-length electromagnetic radiation conduit.

A power conversion device is provided which includes a plurality of series circuits each formed of a voltage source and a controlled current source. At least two of said series circuits formed of the voltage source and the controlled current source are connected in parallel. Further, parallel connection points of the series circuits connected in parallel form output terminals.