A direct power conversion device includes a control unit. tb=1/|fdc−n×fL|. fdc is a frequency twice as high as a frequency of an AC power supply, fL is a frequency of periodic load fluctuations, and n is a positive integer that maximizes tb. In a half period of power supply during a period of tb, the half period including a timing at which peaks of a fundamental wave of load torque and an absolute value of a power supply voltage substantially coincide with each other, the control unit being configured to control the switching elements so that two or more local maximum points appear in the half period of power supply, in a waveform obtained by combining a second harmonic, a fourth harmonic, and a sixth harmonic of a power supply frequency contained in a waveform of an absolute value of a motor current vector.

An electrical device for a converter has at least one capacitor having a first connection and a second connection, a first busbar and a second busbar is disclosed. A respective busbar has a greater extension along a transverse direction than along a longitudinal direction, and has a greater extension along the longitudinal direction than along a vertical direction. The respective busbar has a first surface and a second surface which are opposite one other with respect to the vertical direction. The device also has a first contact-connection device electrically conductively contact-connected to the first connection and via which the first connection is electrically conductively connected to the first busbar, and a second contact-connection device electrically conductively contact-connected to the second connection via which the second connection is electrically conductively connected to the second busbar. The busbars delimit a connection space in the vertical direction for connecting a semiconductor power unit.

An electrical device for a converter has at least one capacitor having a first connection and a second connection, a first busbar and a second busbar is disclosed. A respective busbar has a greater extension along a transverse direction than along a longitudinal direction, and has a greater extension along the longitudinal direction than along a vertical direction. The respective busbar has a first surface and a second surface which are opposite one other with respect to the vertical direction. The device also has a first contact-connection device electrically conductively contact-connected to the first connection and via which the first connection is electrically conductively connected to the first busbar, and a second contact-connection device electrically conductively contact-connected to the second connection via which the second connection is electrically conductively connected to the second busbar. The busbars delimit a connection space in the vertical direction for connecting a semiconductor power unit.

Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.

Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.

Method and apparatus include a first stage converter configured to generate a half sine wave, and a second stage converter in electrical communication with the first stage converter and configured to transform the half sine wave into a power signal. The second stage converter may further supply the power signal to an electrical grid. In one example, the second stage converter may include an isolated, unregulated, resonant direct current/alternating current (DC/AC) converter.

Methods and apparatus for active EMI cancellation in a switch mode power supply are provided herein. For example, an apparatus comprises an active EMI cancellation circuit coupled to a switch mode power supply circuit comprising an isolation transformer, wherein the active EMI cancellation circuit is positioned such that current flow through an EMI coupling capacitor substantially matches displacement current flow through a primary-to-secondary interwinding capacitance of the isolation transformer.

In large PV power plants, grounding of individual PV modules may lead to problems. The present invention overcomes such problems. The basis for the invention is a PV power plant comprising one or more PV generators, each comprising a PV string and an inverter with a DC input and an AC output. The PV string comprises at least one PV module and is electrically connected to the DC input of the inverter. The inverter comprises means for controlling the DC potential at the DC input depending on the DC potential at the AC output. The AC outputs of the inverters are coupled in parallel. The novel feature of the invention is that the PV power plant further comprises an offset voltage source, which controls the DC potential at the AC outputs. Thereby, the DC potential at the DC input will be indirectly controlled, and it is thus possible to ensure that the potentials with respect to ground at the terminals of the PV modules are all non-negative or all non-positive without grounding the PV modules. Ground loops can be avoided, and there is no need for the use of transformer-based inverters.

In large PV power plants, grounding of individual PV modules may lead to problems. The present invention overcomes such problems. The basis for the invention is a PV power plant comprising one or more PV generators, each comprising a PV string and an inverter with a DC input and an AC output. The PV string comprises at least one PV module and is electrically connected to the DC input of the inverter. The inverter comprises means for controlling the DC potential at the DC input depending on the DC potential at the AC output. The AC outputs of the inverters are coupled in parallel. The novel feature of the invention is that the PV power plant further comprises an offset voltage source, which controls the DC potential at the AC outputs. Thereby, the DC potential at the DC input will be indirectly controlled, and it is thus possible to ensure that the potentials with respect to ground at the terminals of the PV modules are all non-negative or all non-positive without grounding the PV modules. Ground loops can be avoided, and there is no need for the use of transformer-based inverters.

The present invention provides an electric stove having a single free-zone burner, the electric stove comprising: a controller which outputs a first output signal comprising a first output level signal and a first synchronization signal, and a second output signal comprising a second output level signal and a second synchronization signal; a first inverter which successively receives the first output signal and second synchronization signal, and outputs first high-frequency power to a first working coil; and a second inverter which successively receives the first synchronization signal and second output signal, and outputs second high-frequency power to a second working coil, wherein the first inverter and second inverter simultaneously output first high-frequency power and second high-frequency power when the first synchronization signal and second synchronization signal are both received.