Provided is a power grid adjustment method based on a load of a variable frequency air conditioner. The method includes: establishing a mathematical simulation model of a virtual synchronous motor in a variable frequency air conditioner controller; establishing a virtual inertia control segment and a droop control segment of power grid adjustment according to the mathematical simulation model; obtaining a reference value of rotation speed variation of a compressor by the virtual inertia control segment; obtaining a reference value .sub.ref of rotational angular frequency of the compressor by the droop control segment; and inputting a sum of the reference value .sub.ref of rotational angular frequency of the compressor and the reference value of rotation speed variation of the compressor into a field-oriented controller (FOC) to control rotation of a motor.

A method for controlling a supply of at least one load with voltage and/or electric current through an electric network.

A method for controlling an electrical power which flows into or out of an electrical subnetwork via a connection point is disclosed. The subnetwork has at least one electrical load, and the electrical load is connected to a control device via a communication connection, the electrical power flowing via the connection point is measured and a maximum power consumption of the electrical load is set by means of the control device on the basis of the electrical power flowing via the connection point. A device for connecting a multiphase subnetwork, which has an energy production installation and an energy store, to a superordinate multiphase alternating voltage network is configured to transmit electrical power between the alternating voltage network and the subnetwork and comprises an AC/AC converter having a network connection, two inverter bridge circuits with an interposed intermediate circuit and a subnetwork connection. The device also comprises a control device which is configured to set the electrical powers flowing via the individual phases of the subnetwork connection on the basis of power values of the energy production installation and/or of the energy store by suitably controlling the inverter bridge circuits of the AC/AC converter.

An electrical apparatus configured to electrically connect to a multi-phase alternating current (AC) electrical power distribution network includes: an input electrical network including: a plurality of input nodes, each configured to electrically connect to one phase of the multi-phase AC electrical power distribution network; at least one non-linear electronic component electrically connected to the input electrical network; an impedance network electrically connected between the input electrical network and ground; and a control system configured to: access a voltage signal that represents a voltage over time at the input electrical network; determine a frequency content of the voltage signal; determine a property of the frequency content; and determine whether an input current performance condition exists in the electrical apparatus based the property of the frequency content.

For grid-connected power converter control, a method estimates a d-axis grid voltage from a d-axis reference current modified with a d-axis current, and a q-axis current modified with a filter inductive reactance. The method generates a q-axis grid voltage from a direct current (DC) voltage input modified with the DC bus voltage modified with a notch filter to balance the voltage input and further reduced with the q-axis current. The method modifies the estimated d-axis grid voltage and the q-axis grid voltage by selectively removing second-order harmonics. The method further determines a d-axis voltage output and a q-axis voltage output as a function of the modified estimated d-axis grid voltage and the modified q-axis grid voltage.

A control method for a power supply system includes a driving circuit conducting a switch element of a first backup transforming module of a backup supplying module corresponding to a phase of one of a plurality of power transforming modules in an abnormal operation according to a working signal corresponding to the power transforming module in the abnormal operation, when one of the plurality of power transforming modules corresponding to a three-phase voltage source is in the abnormal operation; and the driving circuit latching unconducted switch elements of at least one of undriven second backup transforming module of the backup supplying module corresponding to the phase, after a logic control circuit detects working signals corresponding to all phases of each backup transforming module, and latching unconducted switch elements corresponding to phases different with the phase of the first backup transforming module.

A power supply apparatus includes converters connected in parallel to a three-phase alternating-current power supply, input current detectors that detect current flowing through the respective three phases of the three-phase alternating-current power supply, and load current detectors that detect load current of the converters. Each of the converters includes AC-DC converters inputs of connected to two of the three phases. The AC-DC converters are connected in parallel to each other using a common output. The AC-DC converters that are driven maintain balance of output current. A controller determines whether switching between a driven state and a stopped state of the respective AC-DC converters is performed based on detection results from the load current detectors and switches between the driven state and the stopped state of the respective multiple AC-DC converters based on detection results by the input current detectors.

An induction machine with localized voltage unbalance compensation is disclosed. The use of an induction machine with a voltage unbalance correction compensator (VUC) may be used to maintain proper working conditions of the machine during intervals of voltage unbalance.

A load balancing apparatus for balancing the current supplied on each phase of a multiple phase supply, Each supply phase feeds an AC load, as well as an AC-DC converter. The apparatus measures the current supplied from each phase of the supply as well as the power consumed by each of the AC loads. The power consumed by each of the AC-DC converters is adjusted so that the sum of the current drawn by any one of the AC loads, plus the current drawn by the AC-DC converter on the same supply phase, is substantially balanced between the supply phases. Typically, the AC-DC converters supply a common DC bus, such as a battery. In some examples each AC load includes a DC-AC converter configured to supply power from the common DC battery to one or more of the AC loads.

A control device generates a voltage command value for controlling a current flowing between a three-phase AC power supply and a power converter such that a full voltage representative value representing voltage values of all power storage devices agrees with a DC voltage command value. The control device generates a zero-phase voltage command value for controlling a circulating current flowing in a delta connection such that the voltage values of the power storage devices are balanced among first to third arms. The control device combines the voltage command value and the zero-phase current command value to generate an output voltage command value for controlling an output voltage of each unit converter. The control device removes a control amount of the full voltage representative value from a computation of the zero-phase voltage command value to cause output current control and circulating current control not to interfere with each other.