In one embodiment, a method of operating a power electronic converter device for an electrical power converter system is provided. The power electronic converter device includes a converter circuit, a first converter, and a second converter. The first converter and the second converter are switch with a switching pattern such that the first converter and the second converter generate voltages with stepwise voltages changes and an output voltage of the power electronic converter device results frum a superposition of the voltages of the first converter and the second converter. The switching pattern includes switching instants for the second converter such that the voltage of the second converter leaves the fundamental voltage component of the voltage of the first converter unchanged, such that the second converter does not generate a fundamental component of the output voltage.

Provided is an active filter circuit connected to a power-receiving terminal of a power line for an alternating-current power supplied to a power converter device from an alternating-current power grid or a direct-current power source interconnected with the alternating-current power grid, or for a direct-current power supplied from the direct-current power source for reducing a harmonic component of a conduction noise propagating to the power line and outputting the reduced harmonic; and a controller for monitoring a variation in the state of an input power entering a power source module for generating drive power for an active element constituting the active filter circuit, or a variation in the state of the drive power supplied from the power source module, and diagnosing an abnormality of a circuit operation for a circuit including the active element of the active filter circuit therein.

System and method for generating one or more compensation currents for a DC-to-DC voltage converter. For example, a system for generating one or more compensation currents for a DC-to-DC voltage converter includes: a voltage generator configured to receive a reference voltage and generate a first ramp voltage and a second ramp voltage based at least in part on the reference voltage; and a current generator configured to receive the first ramp voltage, the second ramp voltage, an input voltage, and an output voltage; wherein the current generator is further configured to: if the output voltage is smaller than the input voltage, generate a first compensation current based at least in part on the first ramp voltage; and if the output voltage is larger than the input voltage, generate a second compensation current based at least in part on the second ramp voltage.

A method is provided for limiting double-frequency internal power distortion in a power system. The method includes receiving an input voltage from a voltage source at a power converter from which an output power is provided to an electrical load, measuring the output power having a waveform with a steady-state component and a double-frequency transient component, executing computer-readable program code, via processing circuitry, to determine a compensating waveform equal in amplitude to the double-frequency transient component, and that is anti-phase to the double-frequency transient component, and causing the power converter to generate the compensating waveform such that the waveform and the compensating waveform superpose, and the double-frequency transient component of the waveform and the compensating waveform destructively interfere, leaving the steady-state component that is delivered to the electrical load.

A method is provided for limiting double-frequency internal power distortion in a power system. The method includes receiving an input voltage from a voltage source at a power converter from which an output power is provided to an electrical load, measuring the output power having a waveform with a steady-state component and a double-frequency transient component, executing computer-readable program code, via processing circuitry, to determine a compensating waveform equal in amplitude to the double-frequency transient component, and that is anti-phase to the double-frequency transient component, and causing the power converter to generate the compensating waveform such that the waveform and the compensating waveform superpose, and the double-frequency transient component of the waveform and the compensating waveform destructively interfere, leaving the steady-state component that is delivered to the electrical load.

A method of controlling a multi-phase power converter having a plurality of power stage circuits coupled in parallel, can include: obtaining a load current of the multi-phase power converter; enabling corresponding power stage circuits to operate in accordance with the load current, such that a switching frequency is maintained within a predetermined range when the load current changes; and controlling the power stage circuits to operate under different modes in accordance with the load current, such that the switching frequency is maintained within the predetermined range when the load current changes.

A plurality of active filter devices (41, 42, 43) that each have an output connected to a harmonic-generating load device (2) and are capable of generating a compensating current for performing at least one of reduction of a harmonic current of the harmonic-generating load device (2) and improvement of the power factor of the fundamental wave are provided. The plurality of active filter devices (41, 42, 43) provide two or more types of capacities, and the number and combination of operating active filter devices among the active filter devices (41, 42, 43) change in accordance with the magnitude of the compensating current.

Described herein is a method of operating a power electronic converter device for an electrical power conversion system. The power electronic converter device includes a converter circuit including an input side, an output side, a first converter, and at least one second converter. The second converter includes at least one floating cell with a DC intermediate circuit and semiconductor devices. The method includes: switching the semiconductor devices of the floating cell at switching instants determined with optimized pulse patterns or carrier-based pulse width modulation; determining a fundamental voltage component for the floating cell; and generating the fundamental voltage component in the actual voltage of the floating cell by modifying the switching instants, such that a voltage V.sub.C AF of the DC intermediate circuit is lying in a given reference voltage range for balancing the DC intermediate circuit of the floating cell.

A control method of a three-phase multi-level inverter includes: determining a modulation ratio based on output of the three-phase multi-level inverter, where the modulation ratio indicates a ratio of an amplitude value of a sinusoidal modulation wave in pulse width modulation to an amplitude value of a carrier; generating, based on the modulation ratio and a modulation ratio threshold, a common-mode voltage regulation signal for regulating a common-mode voltage in phase voltages of the three-phase multi-level inverter; adding the common-mode voltage regulation signal and a differential-mode voltage regulation signal for regulating a differential-mode voltage in the phase voltages of the three-phase multi-level inverter to obtain a composite regulation signal, where the composite regulation signal is presented as a modulation wave for discontinuous pulse width modulation (DPWM); and generating, based on the composite regulation signal, drive signals for controlling switches of phases of the three-phase multi-level inverter.

A method for controlling an LLC resonance converter controls a converter through the steps of detecting parameter values related to operation of the converter, determining a switching duty of the converter on the basis of the detected parameter values, and controlling the converter with the determined switching duty to improve nonlinearity of a gain curve of the converter, thereby reducing output current ripples and achieving low-gain output.