30results about How to "Eliminate common mode voltage" patented technology

A double reference wave modulation scheme for filterless power amplifiers is disclosed for reducing EMI and common mode voltages. In the filterless power amplifier, differential outputs for driving load impedance are feedback and corrected based on input audio signals. Reference wave generators generate reference waves. A control logic results pulses in the pair of differential outputs in response to a clock signal or a reference voltage and a cross relationship between the input audio signal and the first and second reference waves. Pulses of one of the differential outputs are not overlapped with pulses of the other of the differential outputs for eliminating common mode noises of the power amplifier.

The invention discloses an electromobile driving system vector control method using double inverters. The electromobile driving system vector control method includes the following steps: collecting three-phase stator current, rotor position and rotating speed in an unwinding permanent magnetic synchronous motor, wherein the three-phase current is subjected to 3S/2R conversion to acquire current under a two-phase rotating coordinate system. A system adopts the vector control method with id equal to 0, a stator voltage instruction under the two-phase rotating coordinate system is acquired through double closed-ring control of a rotating speed outer ring and a current inner ring, stator voltage under the two-phase static coordinate system is acquired through 2R/2S coordinate conversion, control pulse of the double inverters is acquired through a single-power-source double-inverter SVPWM (space vector pulse width modulation) module, and switch devices of the double inverters are triggered to realize vector control of double-inverter SVPWM of the unwinding permanent magnetic synchronous motor. The electromobile driving system vector control method has the advantages that the unwinding permanent magnetic synchronous motor is quick to start, high in overload capability and good in speed adjusting performance; due to the single-power-source double-inverter SVPWM, voltage level of the system is increased, and safety and reliability of the system are guaranteed.

The invention discloses a single-stage booster inverter non-isolated grid-connected photovoltaic power generation system. A coupled inductor passive network is introduced to couple the main circuit of the inverter with a power source, the booster function is realized through primary transformation, and at the same time, a fourth diode is added, the electrical connection between the effective vector and the photovoltaic cell end and the power grid side in the traditional zero vector state can be disconnected, so the common mode voltage generation current circuit in the state can be blocked. The invention further discloses a single-stage booster inverter non-isolated grid-connected photovoltaic power generation system control method, in the control method, the adjacent effective vector synthesis pulse width modulation and direct connection control mode is adopted, and the traditional zero vector does not adopted, so the common mode voltage when the traditional zero vector is switched to other states can be eliminated, and the common mode voltage amplitude of the effective vector can be reduced.

The invention discloses a fault-tolerant modulation method for co-busbar double-end cascade type five-level inverters. The method includes the steps that a stator winding of a motor is opened, the two ends of the stator winding are powered up by the two inverters which are completely the same, the two inverters share one set of direct-current busbar, and accordingly the co-busbar double-end cascade type five-level topology is formed; in order to ensure that the reference voltage vector track of each inverter is a circle, when short-circuit trouble happens to a switching device, the maximum output voltage of the inverter is lowered to be half of the voltage before, and only the inside hexagon available switching state is used for synthesizing the reference voltage vector; through rotation and per-unit treatment of a coordinate system, the five-level modulation method is effectively simplified, and the hardware requirement for system control is reduced; by the adoption of equilibrium factors, midpoint potential balance is achieved on the premise that fault-tolerant control is guaranteed. Based on the high-fault-tolerant characteristic of the double-end cascade type five-level inverters, when the switching device breaks down, fault-tolerant operation of the inverters is achieved by reselecting the voltage vector. An optimized 60-degree modulation method is provided according to the double-end cascade type system.

The invention discloses a motor driving shaft grounding device. A conductive sealing ring (12) sleeves the driving shaft (20) in a sealing mode and rotates along with the driving shaft; the conductivesealing ring forms a first sealing surface along the side surface, axially deviating from the motor, of the driving shaft; the first sealing surface is provided with multiple first annular parts (122) arranged radially; one side of the first sealing surface of the conductive sealing ring is provided with a sleeving part (124); a conductive fixing ring (14) is fixed on a motor housing (30) and sleeves the sleeving part; a second sealing surface is formed on the side surface, facing the first sealing surface, of the conductive fixing ring; the second sealing surface is provided with multiple second annular parts (122) arranged radially; shapes of the second annular parts and the first annular parts are complementary; a conductive connection part (162) of a grounding element (16) is connected with the conductive sealing ring or the conductive fixing ring, and the conductive contact part (164) of the grounding element continuously contacts the other one in the conductive sealing ring or the conductive fixing ring. The grounding device can eliminate common mode current. The invention also provides a motor.

The invention discloses a topology circuit for a mining frequency converter. The topology circuit comprises a series reactor, a grounding coupling circuit, a pre-charging circuit and a power unit, wherein the output end of the series reactor is connected with the input ends of the grounding coupling circuit and the pre-charging circuit respectively; the output end of the pre-charging circuit is connected with the input end of the power unit; the output ends of the grounding coupling circuit and the power unit are connected with the input end of a motor at the same time. The topology circuit is simple in structure; through the series reactor, the grounding coupling circuit and the pre-charging circuit, the frequency converter can be effectively prevented from releasing harmonic waves into a power grid, and impact on a rectification unit at the moment of electrification is further eliminated; through the grounding coupling circuit, the common-mode voltage can be better eliminated, and the electromagnetic interference is eliminated.

The invention discloses a multi-level inverter model prediction control method and system. The method comprises the steps of: presetting a control threshold value for controlling a floating capacitor voltage fluctuation range, and determining the balance priority of a midpoint voltage and a floating capacitor voltage; constructing a neutral-point voltage and floating capacitor voltage balance condition, and screening a switch sequence through the balance condition; constructing a value function, constructing a space vector diagram, performing sector division on the space vector diagram according to a vector value function value, and determining a first target sector where the reference voltage is located; carrying out secondary division in the first target sector by taking a virtual vector as a benchmark, carrying out tertiary division on a second target sector according to a rhombic diagonal line, and determining a final position of the space vector diagram where the reference voltage is located; determining a zero common mode vector according to the final position; reordering the vectors according to an inner and outer ring division principle of the space vector diagram to obtain a sequence with reduced switching loss and fixed switching frequency; and obtaining a duty ratio according to the value function so as to control the action of an inverter switching tube.

The invention discloses an AC/DC power supply system characterized in that a grounding device is additionally arranged between an AC system and a converter system, and the grounding device is also connected with a null line and the ground, so that the null line and a grounding point are provided for the conversion system, and the wiring mode of the conversion system is not limited to a three-phase three-wire system; a common-mode voltage elimination circuit is connected to the alternating current side and the direct current side of the conversion system, and the common-mode voltage elimination circuit is not limited to restraining common-mode voltage between the alternating current side and the direct current side of the conversion system; and meanwhile, reverse common-mode voltage of a corresponding proportion is inducted, and the reverse common-mode voltage is connected into a direct current bus and a ground wire loop in series; therefore, the ground common-mode voltage of the conversion system is eliminated.

The invention discloses a single-phase three-level inverter circuit which comprises a bus, a first power switch module 1, a second power switch module 2, a third power switch module 3, a fourth power switch module 4, a fifth power switch module 5, a sixth power switch module 6, a first diode D1, a first inductor L1 and a second inductor L2. Or the fifth power switch module 5 and the sixth power switch module 6 are replaced by a seventh power switch module 7 and an eighth power switch module 8. The first power switch module 1 to the eighth power switch module 8 respectively comprise a main power switch and an auxiliary circuit. The auxiliary circuit is unidirectionally conducted when the main power switch is conducted, and reverse current is prevented from flowing through the main power switch. The auxiliary circuit for protecting the main power switch is added, the main power switch is prevented from being attacked by reverse current, the service life of a device is prolonged, the stability of the circuit is improved, soft switching of the main power switch can be achieved, and the working efficiency of the inverter is improved.

The invention discloses a three-level zero common-mode voltage modulation method based on a DSP (digital signal processor) and a CPLD (complex programmable logic device). PWM (pulse-width modulation) pulse wave modulated by two levels is distributed and adjusted to produce a group of median vector on-off states effective for a three-level inverter, and three-level median vector combination is directly adopted for directly controlling a three-level main circuit to achieve the purpose that the output common-mode voltage is zero. The modulation method is simple and easy to implement without any additional hardware circuits, and applicable to any modulation wave. All output common-mode voltages are zero so as to eliminate leakage current caused by common-mode voltage and drain capacitance, and fundamentally eliminate the common-mode voltage.