An electric working machine according to one aspect of the present disclosure comprises a motor, a rectifier circuit, a capacitor, a series switching element, a resistive element, a drive circuit, a peak voltage value acquirer, and a controller. The capacitor smooths power rectified by the rectifier circuit. The series switching element is coupled in series with the capacitor. The resistive element is coupled in parallel with the series switching element. The controller brings the series switching element into conduction in a case where AC power is inputted to the rectifier circuit and where a specified conducting condition based on a peak voltage value acquired by the peak voltage value acquirer is satisfied.

An air conditioning apparatus including an outdoor unit and an indoor unit comprises a converter main circuit that rectifies and smooths an AC power supply, and allows a DC voltage to be generated across a main circuit capacitor, an inverter main circuit that converts the DC voltage generated by the main circuit capacitor into an AC voltage, a compressor motor driven by the inverter main circuit, an outdoor fan, a fan motor that rotationally drives the outdoor fan, and a microcomputer that controls the outdoor unit. When the fan motor rotates due to outside wind hitting the outdoor fan and enters a power generating state during a standby power saving mode of the outdoor unit, the microcomputer prevents the outdoor unit from shifting to a non-operating state from the standby power saving mode.

A power converter includes a rectifier configured to rectify an AC voltage supplied from an AC power supply, a booster circuit configured to boost the voltage rectified by the rectifier, a smoothing capacitor configured to smooth the voltage output from the booster circuit, a power module configured to convert a DC voltage obtained by smoothing the output voltage by the smoothing capacitor into an AC voltage, and a snubber capacitor configured to absorb a surge voltage superimposed on the DC voltage to be input to the power module. The snubber capacitor is mounted in the power module.

A conversion device includes: an inductor electrically connected to the AC power grid; a first-stage converter configured to output a bus voltage according to the AC power grid, wherein the first-stage converter includes an N-level alternating current-direct current (AC-DC) converter, and the N-level AC-DC converter includes a plurality of switch bridge arms, wherein both an upper bridge arm and a lower bridge arm of each of the plurality of switch bridge arms of the N-level AC-DC converter include a plurality of semiconductor devices connected in series, and a rated withstand voltage Vsemi of each of the semiconductor devices is greater than or equal to (Vbus*δ)/((N−1)*Nseries*λ); and a second-stage converter configured to convert the bus voltage into an output voltage to supply energy to the load.

A system for load balancing on a multi-phase power line connected to a single phase lateral power line, includes a contactor configured to selectively connect each phase of the multi-phase power line to the single phase lateral power line. There is a phase change device connected in parallel with the contactor and a controller. During the phase change state, the controller connects the input of the phase change device to the multi-phase power line and connects the output of the phase change device the single phase lateral power line. The controller causes the phase change device to output a voltage to the single phase lateral line initially aligned with the first phase and then rotated to align with the second phase and causes the contactor changes connection to the second phase of the multi-phase power line and disconnect the phase change device from the power lines.

In one embodiment, an apparatus includes a surge voltage blocker circuit to couple between a distribution grid network and a grid-side power converter of a power conversion system. The surge voltage blocker circuit may include a plurality of series-coupled AC switch circuits, each including: a bidirectional switch formed of a first power transistor and a second power transistor; and a transient voltage suppression device coupled in parallel with the bidirectional switch.

A converter includes an input section including an inductive element, the input section configured to receive a multiphase, AC input voltage; a rectifier section coupled to the input section; a voltage regulator section coupled to the rectifier section, the voltage regulator section configured to control a DC output voltage across a positive DC bus and a negative DC bus; and a controller in communication with the voltage regulator section, the controller configured to command the voltage regulator section to operate in one of a first mode and a second mode.

A device determines a first current, of a first input phase of a power system, and a second current, of a second input phase of the power system. The device determines whether the first input phase and the second input phase are balanced based on the first current and the second current. When the first input phase and the second input phase are not balanced, the device selects the first input phase and an output phase of the power system. The device balances the first input phase and the second input phase by using the first input phase and the output phase.

A ground fault detection method for a power converter is provided, including: measuring, by a voltage sensor, a first voltage and a second voltage respectively, and converting the first voltage and the second voltage into a first digital voltage signal and a second digital voltage signal; receiving, by a controller, the first digital voltage signal and the second digital voltage signal, extracting a corresponding feature quantity of the first voltage and a corresponding feature quantity of the second voltage according to the first digital voltage signal and the second digital voltage signal; and further determining a type of the ground fault of the power converter and locating a ground fault; and when the power converter has a ground fault, shutting down the power converter.

A generator system can include a generator configured to produce an output of alternating current (AC), a rectifier connected to the generator to rectify the AC into direct current (DC) rectifier output, an inverter connected to the rectifier to receive the DC rectifier output and configured to output three phase AC inverter output, and a plurality of output lines connected to the inverter to receive the three phase AC inverter output. The system can include a control module configured to control the output of the inverter. The control module can be operatively connected to one or more of the output lines via one or more local sense leads to receive a local feedback. The control module can be configured to control the inverter as a function of the local feedback to provide one or more of protection, voltage regulation, or harmonic correction.