Systems and methods are described for active harmonics cancellation. A wireless charging apparatus includes a wireless-power transfer circuit comprising a wireless-power transfer coil configured to generate or couple to a magnetic field to transfer or receive power and a plurality of tuning capacitors electrically coupled to the wireless-power transfer coil. The apparatus also includes a power converter circuit electrically coupled to the wireless-power transfer circuit. Additionally, the apparatus includes a signal generation circuit different from the power converter circuit and electrically coupled to one or more nodes between capacitors of the plurality of tuning capacitors. The signal generation circuit is configured to generate and inject a signal into the wireless-power transfer circuit at the nodes between the capacitors. The signal generation circuit includes a rejection filter tuned to an operating frequency of the wireless-power transfer coil.

Provided are a power supply circuit and a power supply system. In the power supply circuit, a main circuit output module includes a first DC/DC converter and a first AC/DC inverter, and a conversion module is configured to output DC power to the first DC/DC converter according to input AC power. The first DC/DC converter is configured to convert the DC power into a constant DC voltage, and output the constant DC voltage to a first AC/DC inverter. The first AC/DC inverter is configured to acquire first supplied electrical energy by converting the constant DC voltage into AC power, and output the first supplied electrical energy.

One example provides a power quality improvement system for an electrical power distribution system including a parameter measurement module to measure a power factor of the electrical power distribution system, a number of capacitor steps selectively connectable to the electrical power distribution system, and a number of harmonic filters connected to the electrical power distribution system, wherein a number and size of each capacitor step and a type of the harmonic filters are based on a load profile of the electrical power distribution system. A controller monitors a status of the harmonic filters and automatically connects or disconnects selected capacitor steps from the electrical power distribution to maintain the measured power factor at a set-point power factor, where a delay before connecting or disconnecting each selected capacitor step is based on a load stability factor of the electrical power distribution system, the load stability factor based on the load profile.

A power analyser for analysing an electrical supply to a load, comprising: a processor; an analogue signal module interfaced with the processor, wherein the analogue signal module is configured to: make analogue signal measurements of the electrical supply, and provide raw analogue data corresponding to said measurements to the processor; and wherein the processor is configured to: access a model suitable for, or associated with, the electrical supply and/or the load, and generate a modified electrical supply estimate in accordance with the model and the raw analogue data.

Systems and methods of the present disclosure involve passive, hybrid, and active filtering configurations to mitigate current harmonics for various electrical loads. One hybrid filtering configuration is medium voltage (MV) active filtering using a DC-DC converter and a multi-level inverter, and low voltage (LV) passive filtering. Another hybrid filtering configuration is MV passive filtering and LV active filtering using a two-level inverter. An active filtering configuration includes both MV and LV active filtering. The present disclosure also features power distribution unit (PDU) transformers electrically coupled to respective power supplies on the LV side of an electrical system. Each PDU transformer includes primary coils in a delta configuration and secondary coils in a wye configuration. The secondary coils are in series with respective leakage inductance coils. The secondary coils and the leakage inductance coils are integrated together into a single unit or module.

A method to reduce harmonics in the electrical output (i.e. voltage and current) of a power plant is provided. The power plant is connected via a point of common coupling with an electrical grid. Converters of the power plant provide respective electrical converter output by an applied pulse-width modulation scheme, which is used in the respective converter. The electrical output of the respective converters is summed to generate the electrical output of the power plant. The electrical output of the power plant is provided via the point of common coupling to the electrical grid. Carrier sideband harmonics, which are generated by the converters, are measured in the electrical output of the power plant. A carrier signal of at least one selected converter is adjusted in its phase until specified and characteristic harmonics in the electrical output of the power plant are reduced below a given threshold.

This invention relates to a method of controlling at least one wind turbine of a plurality of wind turbines connected to an electrical grid at a predefined point in the electrical grid. The wind turbine comprises a DC link connecting a generator side converter to a line side converter, where the line side converter is controlled according to a modulation index requested by a power converter controller. The method comprises determining a harmonic frequency signal indicative of a harmonic frequency value at the predefined point in the electrical grid; determining a deviation between the harmonic frequency signal and a permissible harmonic frequency value; determining a permissible modulation index based on the deviation; comparing the permissible modulation index to the modulation index requested by the power converter controller; and, altering a DC link voltage set-point based on the comparison between the permissible modulation index and the requested modulation index.

A control device for an active filter connected in parallel with a load at an installation point with respect to an AC power supply provided in a power system includes a harmonic voltage detector to detect an m-order harmonic voltage (m is an integer not less than two) included in a voltage of the installation point, a phase corrector to correct a phase of the detected m-order harmonic voltage in accordance with whether an m-order harmonic impedance when an AC power supply side is seen from the installation point is capacitive or inductive, a command value generator to generate a first compensation command value for compensating for the m-order harmonic voltage included in the voltage of the installation point based on the m-order harmonic voltage after the correction, and an output controller to control an output of the active filter based on a first compensation command value.

[Problem to be solved] To achieve adjustment of an electric line based on indexes set separately for harmonic components having different orders in a current in the electric line.

[Solution] A power control system causes a device to adjust apparent power in an electric line, and the power control system includes a setting unit that sets an index regarding each adjustment for a harmonic component of a first order group in a current in the electric line, a harmonic component of a second order group higher in order than the first order group in the current in the electric line, and a fundamental component in the current in the electric line, and a control unit that controls each adjustment by the device based on the index set by the setting unit.

[Problem] As compared with the case where the apparent power in the electric line on the supply side is adjusted without supplying the current to the electric line closer to the power supply side than the distribution transformer, there is a reduction in the effect of the state in the electric line closer to the power reception side than the distribution transformer on the adjustment of the apparent power in the electric line closer to the power supply side than the distribution transformer.

[Solution] A power control system includes a device that receives power from an electric line of a distribution system via a distribution transformer, an acquisition unit that acquires electric line information on the electric line, and a control unit that causes the device to generate a current used for adjustment of apparent power in the electric line based on the electric line information acquired by the acquisition unit.