36results about How to "Reduce current harmonic content" patented technology

The present invention provides a single-phase five-level topology and an inverter. The single-phase five-level topology includes: a first capacitor, a three-level bridge arm module and four switch tubes, and the four switch tubes are respectively the first switch tubes , the fifth switch tube, the sixth switch tube and the eighth switch tube; each switch tube is connected in reverse parallel with a diode; the three-level bridge arm module includes two switch tubes and a double switch unit, and the first switch tube of the third switch tube terminal connected to the first node, the second end of the third switch tube is connected to the neutral point N through the double switch unit; the first end of the fourth switch tube is connected to N through the double switch unit, and the second end of the fourth switch tube is connected to the first node Two nodes. Output five level states, reduce the current harmonic content of the system, reduce the filter inductance, increase the voltage level, suppress the common mode voltage, and improve the operating efficiency. The balance control of the capacitor voltage under full power and full modulation can be realized without adding additional hardware circuits, and the phase output voltage of the system can be prevented from degrading from five-level to three-level.

The invention discloses a double-coil connected medium-voltage power feed system and a power feed method for an urban rail power supply system. The system includes a rectifier transformer, a double-coil connected power feed device and a rectifier unit. The type energy feed device comprises two double energy feed branches arranged in parallel, and each heavy energy feed branch includes an AC-side low-voltage circuit breaker, an isolation transformer, an inverter and a DC-side contactor arranged in series; the method steps include: When starting, the rectifier transformer and rectifier unit take current from the medium-voltage AC power grid and inject it into the DC traction network; Feed back the train braking energy to the medium voltage AC grid. The invention can realize energy saving and DC bus voltage stabilization, and has the advantages of high flexibility, small size, high degree of integration with existing systems, high power factor, low harmonics injected into the AC side, and good versatility.

The invention provides a steady-state test device and method for a modular multi-level converter valve. The device includes a load reactor, a sample valve, an auxiliary valve, a water cooling device, a DC power supply, a control device and a protection device, and the reactor The AC component of the current and the DC component of the current can be controlled separately, and the structure of the steady-state test circuit is simple. The steady-state test method provided by the present invention realizes modularization by unlocking or locking the auxiliary valve and the sample valve during the charging stage and the test stage, and charging the supporting capacitors in the auxiliary valve and the sample valve at different stages. Steady-state test of the level converter valve; the present invention only charges and supplements the support capacitor in the auxiliary valve through the N output interfaces provided by the DC power supply, and does not need to separately set up another DC power supply for the test valve. The charging of the supporting capacitor makes the cost of the whole test circuit lower, and the invention can fully reproduce the actual operating conditions of the modularized multilevel converter valve.

The invention discloses a permanent magnetic wind electric generator control method based on a power factor correction and rectification algorithm in micro grid construction. A three-phase PMSG is controlled through a PFC method, and in order to meet the requirement for rotor position information needed in the control, an original position di / dt detection method, a rotation high-frequency voltage injection method and a double-salient-pole decoupling observer are combined. The three-phase PMSG is controlled through the PFC method, the original position di / dt detection method, the rotation high-frequency voltage injection method and the double-salient-pole decoupling observer are combined to accurately and effectively provide accurate and reliable rotor position information to current control of the PMSG, so that current harmonic content is reduced, power factors in the PMSG approach 1, direct-current output is maintained, and good control of the PMSG based on the PFC method is achieved.

The invention relates to a six-level circuit topology structure for a power conversion system. The circuit includes a left circuit composed of first to fifth bus capacitors connected in series in the same direction, and a first switching device A1 and a second switching device. A2, the third switching device A3, the fourth switching device A4, the fifth switching device A5, and the sixth switching device A6 are connected in series in sequence to form the right circuit, the middle circuit one is composed of the ninth switching device A9, and the seventh switching device A7 The middle circuit 2 composed of the tenth switching device A10 in series, the middle circuit 3 composed of the eighth switching device A8 and the eleventh switching device A11 in series, the middle circuit 4 composed of the twelfth switching device A12, and three clamping capacitors . The invention can effectively reduce the switching loss, reduce the harmonics of the voltage in the circuit, can also flexibly control the switching tube, and can be applied to power conversion devices such as inverters.

The application provides a double-rotor motor and an air-conditioning unit. The double-rotor motor includes a stator, an outer rotor and an inner rotor, the stator is fixedly arranged, and the stator forms an outer stator section and an inner stator section connected along its height direction, the outer rotor is arranged outside the outer stator section, and the inner rotor is arranged on the inner stator section inside. By applying the technical solution of the present invention, only the stack height of the outer rotor with a larger radius can be increased, and the increased cost is less, but the resulting moment of inertia increases significantly. Increase the moment of inertia of the motor, reduce the torque fluctuation of the low-frequency operation of the compressor, reduce the current fluctuation of the low-frequency operation, reduce the harmonic content of the current, make the compression speed at low-frequency operation more stable, and improve the efficiency of the compressor at low-frequency operation.

The present invention discloses a harmonic current compensation device used for a rectifier. The harmonic current compensation device comprises a harmonic injection circuit, and the harmonic injectioncircuit comprises a first filtering capacitor, a second filtering capacitor, a third filtering capacitor, a compensation filtering inductor, a first switching tube and a second switching tube. A first current detection module is used to detect a current flowing through the compensation filtering inductor, a second current detection module is used to detect a load current of the rectifier, a voltage detection module is used to detect the voltage of a three-phase power grid, and a control module is connected with the current detection modules, the voltage detection module, the control end of the first switching tube and the control end of the second switching tube separately and is used to generate a switch control signal according to the voltage of the three-phase power grid, the load current and the current flowing through the compensation filtering inductor and control the first and second switching tubes according to the switch control signal, thereby distributing a harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid.

A new single-phase hybrid three-level rectifier comprises a single-phase uncontrollable diode rectifier bridge, a filter, a single-phase VIENNA rectifier bridge, a voltage and current sampling circuit, and a signal conditioning circuit. Through employing the above structure and a single-period control algorithm, the rectifier is simple in control method, is simple in structure, and just needs to collect an output voltage and an input current. The rectifier is very high in robustness, is high in power density, is large in power factor, is stable in output voltage, and is high in system reliability. Compared with a conventional single-phase rectifier, the rectifier provided by the invention can greatly improve the conversion efficiency, is large in application range, can greatly reduce the voltage stress of a power switching tube through employing the three-level structure, and can save a large amount of material resources and financial resources.

The invention provides an opening-winding permanent-magnet synchronous motor driving system for mine traction and a working method thereof. The driving system is composed of a first power supply circuit connected with a three-phase voltage, a second power supply circuit connected with the three-phase voltage, a permanent-magnet motor connected with the first power supply circuit and the second power supply circuit, a sampling module connected with the permanent-magnet motor, a main control module connected with the sampling module, and a driving module connected with the main control module, the first power supply circuit and the second power supply circuit. The driving system has the following beneficial effects: the neutral point of the permanent-magnet synchronous motor is opened to form a winding opening structure with dual ports; the opening-winding permanent-magnet synchronous motor is used as a driving motor of the mining electric locomotive, so that the requirement of the largestarting torque is met and the starting characteristic of the driving system is improved; and two converters are connected to the two ends of the opening-winding permanent-magnet synchronous motor, so that the system stability is improved and the fault rate is reduced.

The invention discloses a common-mode-voltage inhibiting method applicable to a matrix converter. An effective vector of the matrix convertor is selected according to a traditional double-voltage modulation method. A pair of large vectors with maximum amplitudes and a pair of intermediate vectors with intermediate vectors on adjacent directions of the effective vector are used to form opposite vectors which are used to substitute a zero vector in a traditional double-voltage modulation method so that an output line voltage is synthesized. A modulation functional expression is constructed on the basis of the traditional double-voltage modulation method so that control demands of input current and output voltage of the matrix converter are met and at the same time, a common-mode voltage amplitude is reduced effectively and it is also ensured that only two ideal switches change when ideal switches of the same output phase are switched. It is proved by experiments that the common-mode-voltage inhibiting method applicable to the matrix converter is capable of reducing a common-mode voltage to 57.7% of an input power-supply amplitude and at the same time, harmonic content of input current and output current is less than that of a current frequently-used optimization zero-vector modulation position method.

The invention discloses a three-phase three-level high-frequency link matrix rectifier topology and a modulation method thereof, and relates to the field of topology and modulation of electronic powerinverters. The three-phase three-level high-frequency link matrix rectifier topology comprises a three-phase three-level matrix inverter of which the input terminal is electrically connected with a power network and the output terminal is electrically connected with the primary side of a transformer; each phase of the three-phase three-level matrix inverter comprises four groups of two-way switchunits that are common-emitter series-opposition structures; and the three-phase three-level matrix inverter is also provided with a three-level structure in which a neutral point clamped diode and aneutral point clamped capacitor are replaced with two-way switch units respectively. From the view of circuit topology, the three-phase three-level high-frequency link matrix rectifier topology has advantages of large output capacity, high output voltage, low current harmonic content and the like by introducing more switch tubes. By adopting the decoupled and coupled dual-carrier SPWM modulation method, the voltage-withstanding level of components is beneficially reduced, the unit power factor in the grid side is realized, and the content of low-order harmonics of the input current is reduced.

The invention discloses a concentrated direct-current power supply skid-mounted electric automobile charging device. A solid insulating ring network cabinet is arranged in a high-voltage chamber; a dry transformer is arranged in a transformer chamber; a low-voltage switch cabinet, a monitoring cabinet, an AFE (analog front end) and a charger are arranged in a low-voltage distribution chamber; a hoisting hanging point is formed at the bottom of a charging house; a grounding copper bar is arranged at the bottom of the charging house; an air-conditioning outdoor unit chamber is arranged above the transformer chamber and used for assembling an air-conditioning outdoor unit; and the outer wall of the charging house is provided with wire inlet and outlet holes. The device has the advantages of concentrated rectification, dispersed direct-current power supply, direct supply of direct-current power supply to multiple chargers after the alternating current is converted into direct current by adopting rectification of the AFE, high power factor, low current harmonic content, no influence on power quality of a power grid, capability of directly connecting the electrical energy generated by new energy generating equipment of solar energy, wind energy and the like to a direct-current bus, small volume and high protection level due to the use of a skid-mounted house body, integral field assembly, convenience for transportation, and waterproof, fireproof and wind-sand resistant properties of the house body.

The invention discloses a common-mode voltage suppression method based on a 60-degree coordinate system open-winding dual-inverter space vector modulation, which achieves the effect of common-mode voltage suppression by changing the duty cycle of a specific vector combination. In this method, every time the switching state is changed, the switching tube only changes once and the mutual difference of the common-mode voltage generated by adjacent switching sequences is the minimum value of the generated common-mode voltage value, which reduces the switching frequency of the system and reduces the current and torque ripple. , to achieve the effect of dynamic common-mode voltage suppression, which essentially solves the problems of common-mode voltage in the open-winding dual-inverter topology, and reduces the current harmonic content and torque ripple when the permanent magnet motor is running.

The invention relates to the technical field of power electronic converters, in particular to a three-phase isolated buck-mode PFC rectifier and a control method thereof. The three-phase isolated buck-mode PFC rectifier comprises a three-phase rectifier bridge unit and a switch array unit, wherein the three-phase rectifier bridge unit comprises three rectifier bridge arms, and each rectifier bridge arm comprises an upper diode and a lower diode separately; and the switch array unit comprises a high-frequency switch group and three bidirectional switch groups, the high-frequency switch group iscomposed of a first switch tube, a second switch tube, a third switch tube and a fourth switch tube which are connected in series, and the three bidirectional switch groups comprise a first bidirectional switch group, a second bidirectional switch group and a third bidirectional switch group. According to the three-phase isolated buck-mode PFC rectifier and the control method thereof, the whole system structure can be simpler, the efficiency is improved, the three-phase isolated buck-mode PFC rectifier has the advantages of high power factor, low current harmonic content, high power supply density and high efficiency and can be widely applied to occasions where three-phase power supply with higher power density requirements are supplied.