Abstract: A system includes a first inverter connected between a dc power source and an input terminal of a first leg of a coupled inductor, a second inverter connected between the dc power source and an input terminal of a second leg of the coupled inductor, a third inverter connected between the dc power source and an input terminal of a third leg of the coupled inductor, and an output filter connected between the coupled inductor and an ac power source, wherein output terminals of the first leg, the second leg and the third leg of the coupled inductor are connected together and further connected to the output filter.

Abstract: The present disclosure discloses a heat dissipation plate for chip heat dissipation, a server heat dissipation system, and a heating device. One end of the heat dissipation plate may be blocked. Another end of the heat dissipation plate may be provided with a water inlet and a water outlet. A pipeline assembly in the heat dissipation plate may include a plurality of branch water inlet pipelines and a plurality of branch outlet pipelines. One end of the plurality of branch water inlet pipelines may operably connect to the water inlet. One end of the plurality of branch water outlet pipelines may operably connect to the water outlet. Another end of the plurality of branch water inlet pipelines may be operably connected to another end of the plurality of branch water outlet pipelines through a connection pipeline.

Abstract: A method for judging rotating characteristics of light sources based on summation calculation in visible light indoor positioning is disclosed. The method is implemented based on an LED positioning system, and comprises the following steps: firstly, arranging the light sources into a convex pattern in order, and arranging the emitted sequence for each light source according to set conditions; secondly, fixing the position and attitude of a cell phone as a receiving end, continuously shooting with the cell phone camera to obtain a set of light source pictures, and performing image processing to obtain emitted sequences of the light sources; thirdly, performing sequence correlation operation on adjacent light sources to obtain emitted sequence delays, and performing summation calculation on the emitted sequence delays, to judge true and false light sources; and finally, excluding the false light source, and then completing positioning using a positioning algorithm.

Abstract: A simulation method for flow field of multi-stage fracturing on horizontal well in tight oil reservoir is provided.

Abstract: A photovoltaic power system includes a DC/AC inverter circuit, N DC/DC converter circuits that are located at a previous stage of the DC/AC inverter circuit and that are respectively connected to photovoltaic strings, and a controller connected to the DC/AC inverter circuit and the N DC/DC converter circuits. The controller is configured to: perform MPPT control on n DC/DC converter circuits, and perform CPG control on (N-n) DC/DC converter circuits. In the two control manners, a fast and accurate power reserve or limit of a photovoltaic string inverter with any illumination intensity and ambient temperature can be implemented, and fluctuation of a DC bus voltage and AC output power of the photovoltaic string inverter can be eliminated. Control on a virtual synchronous generator of the photovoltaic string inverter is implemented, and a lifespan of the photovoltaic string inverter is prolonged, without a need to add an energy storage element.

Abstract: A simulation method for flow field of multi-stage fracturing on horizontal well in tight oil reservoir is provided.

Abstract: A method for identifying a medium structure coupling and a fracture network morphology of a shale gas reservoir includes the following steps. Firstly, performing a fracturing test on shale cores by using a modified Brazilian disc test and categorizing the fracture network morphology. Secondly, performing a shale matrix-fracture structure and stress sensitivity test on the shale cores having different fracture network morphology. After that, determining a stress sensitivity constant of different fracture network morphology according to indoor core data and finally preparing an identification chart of the fracture network morphology based on an indoor core stress sensitivity text combined with a production practice. The identification chart can be applied to an actual fracturing well, and the fracture network morphology is directly identified by a real-time effective stress and a normalized flow.

Abstract: A control method and apparatus for a single-phase five-level converter are provided. The method includes: obtaining a first-phase initial modulated wave and a second-phase initial modulated wave of the single-phase five-level converter; obtaining a first-level modulated wave, a second-level modulated wave, a third-level modulated wave, a fourth-level modulated wave, and a fifth-level modulated wave that are output by the single-phase five-level converter; calculating the first-level modulated wave, the second-level modulated wave, the third-level modulated wave, the fourth-level modulated wave, the fifth-level modulated wave, the first-phase initial modulated wave, and the second-phase initial modulated wave, to obtain a common-mode modulated wave of the single-phase five-level converter; and calculating the first-phase initial modulated wave, the second-phase initial modulated wave, and the common-mode modulated wave, to obtain a pulse-width modulated wave of the single-phase five-level converter.

Abstract: A method for processing a direct current electric arc and an apparatus, includes: obtaining a first current which is a direct current input current of a direct current cable of a photovoltaic cell system; obtaining a second current, where the second current is a direct current common mode current of a direct current cable or an alternating current common mode current of an alternating current cable; calculating a correlation coefficient between a frequency domain component of the first current and a frequency domain component of the second current; and when determining that the first current meets an electric arc occurrence condition and the correlation coefficient is greater than or equal to a preset coefficient threshold, skipping sending a direct current electric arc fault alarm. The correlation coefficient is used to reflect a proportion of common mode noise generated by the second current, and the preset coefficient threshold is set.

Abstract: Provided are sampling pumps and gas analyzers using the sampling pumps. The sampling pump may include at least one reciprocating pump set and a control system. Each reciprocating pump set can include two reciprocating pumps. The control system can output drive signals for controlling reciprocating drawing and compressing operations of the reciprocating pumps, where the control system may be designed to output the drive signals that cause the two reciprocating pumps within the same set to provide opposing impact directions at the same time.

Abstract: The present disclosure provides a method for optimizing bunch distance of fractured horizontal wells of shale gas, which relates to the technical field of oil exploration. The method comprises first establishing a stress field distribution model for a single fracture; then establishing an induced stress distribution model of segmented single-bunch fracturing for a horizontal well; later establishing an induced stress distribution model of segmented multi-bunch fracturing for a horizontal well; last optimizing fracturing parameters and fracture distance according to the distribution pattern of the induced stress difference.

Abstract: The present disclosure provides a method for optimizing bunch distance of fractured horizontal wells of shale gas, which relates to the technical field of oil exploration. The method comprises first establishing a stress field distribution model for a single fracture; then establishing an induced stress distribution model of segmented single-bunch fracturing for a horizontal well; later establishing an induced stress distribution model of segmented multi-bunch fracturing for a horizontal well; last optimizing fracturing parameters and fracture distance according to the distribution pattern of the induced stress difference.

Abstract: A single-phase converter control method and apparatus, includes calculating on a voltage corresponding to a first level output by a single-phase converter, a voltage corresponding to a second level output by the single-phase converter, and a voltage reference value about the voltage corresponding to the first level and the voltage corresponding to the second level to obtain a common-mode modulated-wave change rate of the single-phase converter, where the first level is a direct-current-side positive-bus level, and the second level is a direct-current-side negative-bus level, calculating on a first-phase initial modulated wave of the single-phase converter, a second-phase initial modulated wave of the single-phase converter, and the common-mode modulated-wave change rate to obtain a common-mode modulated wave of the single-phase converter, and calculating on the first-phase initial modulated wave, the second-phase initial modulated wave, and the common-mode modulated wave to obtain a pulse width modulated wave

Abstract: Provided are sampling pumps and gas analyzers using the sampling pumps. The sampling pump may include at least one reciprocating pump set and a control system. Each reciprocating pump set can include two reciprocating pumps. The control system can output drive signals for controlling reciprocating drawing and compressing operations of the reciprocating pumps, where the control system may be designed to output the drive signals that cause the two reciprocating pumps within the same set to provide opposing impact directions at the same time.

Abstract: A time-sharing wave recording method is provided. Firstly, N1 operating variables are selected, and the storage addresses of the N1 operating variables are mapped to N1 index variables. Then, N2 record channels in a sequential relationship are provided, and a mapping relationship between each record channel and the N1 index variables is established. Then, the values of the operating variables are assigned to a first record channel of the N2 record channels in response to a rising edge of a pulse of a clock signal and a start triggering signal, the values of the operating variables are sequentially assigned to the rest of the N2 record channels in response to a rising edge of each pulse of the clock signal and the start triggering signal, and the assigned values of the operating variables for the N2 record channels are recorded to the memory.

Abstract: A converter system and method is provided. The converter system includes a converter and a control module. The converter is electrically connected with a DC bus and a load. The converter is configured to realize the conversion between a bus voltage of the DC bus and a load voltage of the load. The control module is electrically coupled with the converter. When the converter is in a standby mode, the control module generates a first-side compensation signal according to the bus voltage and generates a second-side compensation signal according to the load voltage. And the control module generates an instruction current signal according to the first-side compensation signal, the second-side compensation signal and a reference current signal. The control module generates the driving signal according to the instruction current signal, so as to control an output current of the converter to be stable.

Abstract: A system includes a first inverter connected between a de power source and an input terminal of a first leg of a coupled inductor, a second inverter connected between the de power source and an input terminal of a second leg of the coupled inductor, a third inverter connected between the de power source and an input terminal of a third leg of the coupled inductor, and an output filter connected between the coupled inductor and an ac power source, wherein output terminals of the first leg, the second leg and the third leg of the coupled inductor are connected together and further connected to the output filter.

Abstract: A method for controlling a DC bus voltage in a DC bus system, the system including a DC bus and an energy storage unit coupled to the DC bus, includes: detecting a DC bus voltage; detecting, by the energy storage unit, a DC bus voltage of the DC bus; determining, by the energy storage unit, a power reference value based on the DC bus voltage; and adjusting, by the energy storage unit, one of output power and absorbing power based on the power reference value.

Abstract: A system comprises a plurality of inverter units having inputs connected to a power source and a coupled inductor comprising a plurality of windings and coupled between the plurality of inverter units and an output filter, wherein each winding of the plurality of windings has a first terminal connected to an output of a corresponding inverter unit and second terminals of the plurality of windings are connected together.

Abstract: A wave loss detection circuit includes: an anode of the diode receives a first drive signal, and a cathode of the diode is connected to a first end of the first resistor; a second end of the first resistor is connected to a first end of the first energy storage unit, a first end of the second resistor, and a first input end of the comparison unit; a second end of the first energy storage unit and a second end of the second resistor are connected to a ground level, and a resistance of the first resistor is less than a resistance of the second resistor; a second input end of the comparison unit is configured to receive a threshold voltage, and if a voltage signal received by the first input end is less than the threshold voltage, which indicates that a wave loss occurs in the first drive signal.