107results about How to "Reduce Harmonic Distortion Rate" patented technology

The invention provides an active damping scheme for multiple LCL inverter resonant coupling. The active damping scheme comprises a distributed grid-connected power generation system formed by the series connection of a plurality of photovoltaic LCL inverters and a full wave energy metering device. The control structure of the current and active damping control link of each of the LCL inverters comprises an inverter reference output current calculation link, a photovoltaic power front feed reference current compensation link, an inverter output current deadbeat control link and an active damping compensation link. According to the control method of the invention, the harmonic distortion rate of grid-connected total current can be reduced, the metering data reliability of the full wave energy metering device is effectively improved, the specific harmonic amplification interference of inverter output current by the self resonant point of a single inverter filtering link is effectively reduced, the parallel connection resonant coupling among multiple inverter filtering links is effectively reduced, the independence of each inverter output current is ensured, and the interference of the inverter output current by power grid harmonic voltage is effectively reduced. According to the active damping scheme, the safe and stable operation of an inverter parallel system can be ensured.

The invention discloses a diode clamped three-level high-voltage matrix converter and a modulation method thereof. The diode clamped three-level high-voltage matrix converter is a novel high-voltage matrix converter formed by connection of two three-phase bi-directional matrix rectifying modules which are in series connection with one diode clamped three-level inverting module. The matrix converter has the advantages of bidirectional flow of energy, sinusoidal input current, controllable power factors, compact structure, output current of good quality, no requirement for a step of direct current energy storage, strong fault-tolerant capability, and the like, and is particularly suitable for medium high-voltage motor drive and a grid-tied wind power generation system.

The invention relates to photovoltaic power generation device and method based on amplitude-phase control, belonging to the technical field of power electronics. An AC side voltage and current sensor detects three-phase AC voltage and current, and the three-phase AC voltage and current are processed by a voltage and current translation circuit and then transmitted to a DSP of a main control unit for processing; the DSP determines the output vector of voltage regulation through the amplitude-phase control and inner loop control according to set values of the detected AC side current and voltage and DC side voltage and transmits the output vector to an FPGA; output voltage received by the FPGA and a waveform generated by a triangle generator are synthesized into a PWM waveform to be transmitted to a driving and amplifying unit; and a switching device of a main circuit unit generates switch-on and switch-off according to an amplified pulse signal. The photovoltaic power generation method successfully reduces the AC side voltage distortion rate, is suitable for multiple load types, reduces the influence of load current change on output AC voltage and enhances the fast response capacity.

The invention discloses a three-phase four-leg inverter and a control method thereof. The inverter is formed by a rectification circuit, a direct current filtering circuit, a three-phase four-leg inverter circuit, an alternating current filtering circuit, a sampling circuit, a DSP controller, an opto-coupler isolation circuit and a power supply circuit. An input terminal is parallelly connected with two energy storage capacitors which are connected in series. The each energy storage capacitor is parallelly connected with an equivalent voltage-sharing resistor respectively. The control method is based on a gamma component control method in a three-dimensional space vector. A traditional three-dimensional space vector is decomposed into a two-dimensional space vector and a gamma vector. A PI controller is combined. PWM of a fourth leg is generated through controlling the gamma component so as to carry out full compensation on output voltage imbalance caused by various kinds of factors. And the advantages of the two-dimensional space vector are fully used to control the previous three legs. The control method is simple and practicable. A dynamic response is fast. Voltage stabilization precision is high. The output voltage is balanced and a harmonic wave distortion rate is low. A good control characteristic can be possessed under the conditions of unbalanced and non-linear load.

The present invention discloses a matrix V2G quick charge and discharge method. The method adopts an AC/DC matrix converter topology structure, and six bidirectional switches of the structure adopt common-emitter IGBTs. The method comprises four steps of carrying out sector partition and calculating sector angles and effective current duty ratios, setting conducting time for the corresponding bidirectional switch in each sector, performing quick charge by means of voltage-current double closed-loop space vector control, and performing constant-current discharge by means of current loop negative feedback control. The matrix V2G quick charge and discharge method according to the present invention solves the problems of high frequency of electric energy converting, low converting efficiency and long time for charging and discharging of the existing V2G converter. The matrix V2G quick charge and discharge method realizes quick charge and discharge of the storage battery for the electric automobile by means of pulse charging/constant-current discharging the storage battery based on an AC/DC matrix converter, the power factor is 1, and the harmonic distortion of grid-side current is decreased to below 5% by using the double zero vector switch sequences, so that the switching loss is effectively reduced, and the conversion efficiency is increased.

The invention discloses a dual-three-level online-topology switchable inverter, belongs to the field of electrical energy conversion and aims to solve the problem of low working efficiency of existing inverters because of complex structures and large switching loss. According to the dual-three-level online-topology switchable inverter, two three-level inverter bodies provided with auxiliary switches are connected in series and connected with each other through a bilateral switch, when an input voltage of a direct current power supply is changed, the inverter can be switched between a five-level cascaded inverter mode and a three-level inverter mode through the bilateral switch, and the number of power switch devices is reduced, so that the structure of a system is simple, the switching loss of the system is reduced by 20%, the working efficiency of the inverter is further improved by 15%, and meanwhile, the harmonic distortion rate of an output voltage is reduced by 5%. The dual-three-level online-topology switchable inverter is used for converting direct current voltages into alternating current voltages, so that the working efficiency of the inverter is improved, and the working range of the inverter is widened.

Based on change of load, and dynamic output idle work in large range, the disclosed compensating device filters off harmonic in order to reach purposes: raising power factor, compensating asymmetric three phases, lowering flicker, and harmonic distortion rate so as to reduce loss of distribution network, and improve quality of power supply. The compensating device includes inversion bridge, and control unit. Through connection transformer being connected to distribution network, and connected to capacitor bank directly, the inversion bridge is in bridge structure of three levels and three single phases. Using direct current control algorithm based on phase-shifting carrier wave, the control unit collects bus voltages and currents from PT and CT on bus, as well as output current of device from CT of device, and DC voltage from capacitor bank to generate wave form in pulse-width modulation in order to control on/off of each power electronic device in the inversion bridge.

The invention discloses a highly-reliable main circuit topological structure of a railway ground deflector. The highly-reliable main circuit topological structure comprises a rectification unit, an intermediate DC link and an inversion unit, wherein the rectification unit comprises a single-phase input multi-winding isolation transformer and N power modules on the rectification side. The primary side of the single-phase input multi-winding isolation transformer is connected with a railway traction network, and the secondary side of the single-phase input multi-winding isolation transformer is a plurality of electrically isolated multi-winding coils. Each multi-winding coil is connected with the AC input side of a rectification-side power module, the positive DC bus of the power module is in parallel with the positive DC bus of the intermediate DC link, and the negative DC bus of the power module is in parallel with the negative DC bus of the intermediate DC link. M electrical isolation converter sub-systems can be designed according to system power transformation requirements, power modules in the converter sub-systems are controlled through a carrier phase-shift PWM modulation strategy, cascade operation is carried out through the magnetic field of an isolation transformer, and the reliability of a converter is improved.

The invention discloses a model prediction direct power control method based on three vectors, and the method comprises the steps: analyzing the impact on active and reactive power change rates from anon-zero voltage vector and a zero voltage vector, predicting the amplitudes of the active and reactive power under different combinations of voltage vectors, selecting a proper combination of voltage vectors according to a minimum power error rule, and calculating the corresponding action time; driving six switching tubes to operate through the pulse-width modulation technology, controlling theactive and reactive power, and following the given values. The method does not need an AC side grid voltage sensor, thereby saving the cost and improving the reliability of a system. In one period, the method employs three voltage vectors, so the method can effectively inhibit the power pulsation. The method achieves the compensation for the active and reactive power, and reduces the distortion rate of current harmonic waves. The method can avoid the static errors of the active and reactive power through prediction power control.

The invention discloses a battery charger. The battery charger comprises control modules and n charging modules, wherein n is a positive integer; each charging module comprises a control switch and an uncontrollable rectifying circuit separately; the control modules are electrically connected with a plurality of control switches respectively; the output ends of the control switches are electrically connected with the input ends of the corresponding uncontrollable rectifying circuits; the input end of each control switch is connected to alternating current; the output end of each uncontrollable rectifying circuit is connected to the corresponding battery; each control module transmits a control instruction to the corresponding control switch; and the control switch receives the corresponding control instruction and performs switch on and switch off of the electric connection with the corresponding uncontrollable rectifying circuit according to the control instruction. By adoption of the battery charger, the charging task can be completed, harmonic distortion rate is lowered, the power factor on the alternating current side is improved, and the number of the adopted semiconductor devices is small, so that charging efficiency is greatly improved while the manufacturing cost is lowered.

The invention discloses a three-vector-based low-complexity model forecasting direct power control method. The method comprises the following steps: by taking negative conjugate complex power under asynchronous rotating coordinate system as a control variable, calculating a sector where an optimal non-zero voltage vector is positioned according to a power forecasting model of a system so as to select a corresponding voltage vector combination; then calculating action time of each voltage vector by adopting the principle of a minimum error between active power and reactive power; and driving six switching tubes to operate through a pulse width modulation technology, so as to control the active power and the reactive power to follow set values. The method saves the cost and improves the reliability of the system; the control algorithm can be simplified; the power pulse can be effectively suppressed; a switching frequency is fixed, so that the design of a filter is facilitated; the active power and the reactive power are compensated to reduce the current harmonic distortion rate; and by adoption of forecasting power control, no offset is caused between the active power and the reactive power.

The invention relates to a soft starting method improved based on an H-bridge cascade STATCOM (Static Synchronous Compensator). The method is characterized by comprising the main steps of: accessing a current-limiting resistor in series during starting of the STATCOM, controlling pulse signals of all unit switch devices so as to absorb active power provided by a power grid to the greatest extent, and pre-charging a device; removing the current-limiting resistor after pre-charging is completed, and forwarding the device into an idle running period; providing a voltage given value of a DC side by a voltage gradually-increasing method during idle running period; and stably increasing the voltage of the DC side into the given value; forwarding into a load running period and completing the starting process. According to the soft starting method of the device, provided by the invention, the pulse signal of all unit switch devices are controlled from a pre-charging period, harmonic distortion rate of the output current of the device during the pre-charging period is greatly reduced, and the voltage steady-state value of the DC side is also effectively improved during the pre-charging period; and the voltage given value of the DC side is provided by a voltage gradually-increasing method, so that the capacitor voltage of the DC side can be stably increased into the given value without overshoot.

The invention discloses a novel topology of a double-stage matrix converter and a common-mode voltage suppression strategy of the double-stage matrix converter. According to the topological structure,a one-way switch tube is connected with a direct current side upper bus and a direct current side lower bus of a conventional double-stage matrix converter in series separately; when the direct-current side switch tube is switched off, the inversion-stage effective vector is equivalent to an inversion-stage zero vector when the direct-current side switch is switched on, and the inversion-stage zero vector is called as an inversion-stage equivalent zero vector; according to the novel topology, the equivalent zero vector is utilized to participate in modulation, and the inversion stage seven-section type space vector modulation is optimized into three-section space vector modulation, and meanwhile, the inhibition of common mode voltage is realized. The novel topology has the advantages thatthe common mode voltage of the load side can be reduced to be 0.577 times of the peak value of the input phase voltage in the whole area at the voltage transmission ratio of 0-0.866, and the inhibition effect is equivalent to that of the prior art; the current conversion control strategy is simple, the rectification stage can be directly subjected to current conversion, and the reliability of thesystem is improved; and the optimized modulation strategy is simple and easy to realize, the total actual switching frequency of the system is basically unchanged compared with that in a traditionalmodulation strategy, the actual switching frequency of the inversion stage is greatly reduced, the system switch loss distribution is changed, the output current harmonic distortion rate is lowered, the input current quality is kept unchanged, and the electric energy quality is improved.

The invention discloses a three-phase Ac-DC non-contact power supply system with a power factor correction function. Three channels of single-phase alternating current are respectively rectified to unidirectional pulsating direct currents via a single-phase full bridge rectification circuit, high frequency alternating current is obtained via the chopping of the three pulsating direct currents, electric energy is transmitted from primary coils to secondary coils, three secondary coils are respectively connected with a capacitor in parallel to form current sources, the three channels of current sources respectively output energy to a voltage-doubling rectification circuit to form three channels of charging pump circuits, output terminals of the three channels of charging pump circuits are connected in parallel, a unified direct current voltage is obtained, and stable direct current voltage can be obtained by employing a secondary filtering circuit. According to the system, the work is reliable, and the power supply efficiency can reach more than 90% to the maximum.

The invention discloses an adaptive precise harmonic compensation method based on a photovoltaic grid-connected system. The method comprises the following steps: detecting output current and an outputvoltage on an AC side of a photovoltaic grid-connected inverter when the photovoltaic grid-connected inverter works at a maximum power tracking point; detecting the remaining capacity of the photovoltaic grid-connected inverter, judging the active power flow directions of different subharmonics, and formulating a compensation strategy; adaptively outputting a to-be-compensated component switch on-off signal according to the remaining capacity of the photovoltaic grid-connected inverter; and achieving precise harmonic compensation by using a repeated double closed-loop controller according tothe switch on-off signal. According to the adaptive precise harmonic compensation method disclosed by the invention, the remaining capacity of the inverter is dynamically tracked according to the external illumination changes, the compensation cost of the photovoltaic inverter can be effectively reduced, and the distortion rate of the grid side harmonics is maximally reduced while making full useof the limited remaining capacity of the photovoltaic grid-connected inverter.

The invention discloses a hybrid four-level rectifier, which mainly comprises an A-phase circuit, a B-phase circuit, a C-phase circuit, a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R,wherein two ends of the capacitor C1 are recorded as a g end and an h end separately; two ends of the capacitor C2 are recorded as an h end and a j end separately; two ends of the capacitor C3 are recorded as a j end and a k end separately; the A-phase circuit, the B-phase circuit and the C-phase circuit are connected in parallel and then connected to the g end; the capacitor C1 is connected withthe capacitor C2 through the h ends in series; the capacitor C2 is connected with the capacitor C3 through the j ends in series; and the k end of the capacitor C3 is connected with the resistor R inseries and then connected to the g end. According to the hybrid four-level rectifier, the number of output levels is increased, reduction of voltage stress of a switching device is facilitated and theswitching device is applicable to medium-voltage high-power occasions. According to the hybrid four-level rectifier, the harmonic distortion rate of input current is also reduced, the switching lossof a converter is reduced, the switching frequency of the converter is improved, the volume of a passive device is reduced and the power density of the converter can be improved. The hybrid four-levelrectifier is applicable to medium-voltage high-power application occasions and low-voltage high-power density application occasions.

The invention provides a current tracking control method. For a hybrid rectifier including a three-level PWM boost rectifier, the current tracking control method comprises the steps of obtaining three-phase given current, acquiring three-phase input real-time current of the hybrid rectifier, sorting three-phase input phase sequences of the hybrid rectifier according to three-phase set duty ratio from small to big, obtaining the breakover time Tx, Ty and Tz of a three-phase switch in a working period according to a circuit structure of the hybrid rectifier, judging whether 0<Tx<Ts/2, 0<Ty<Ts/2 or 0<Tz<Ts/2 is established or not; correcting the Tx, Ty or Tz; obtaining the three-phase duty ratio of the three-phase switch; respectively performing breakover or turnoff of the corresponding three-phase control switch according to the three-phase duty ratio after pulse width modulation so as to achieve current tracking. The current tracking control method has the advantages of being high power factor, low in harmonic distortion rate and the like and can be widely applied to the field of current tracking control.

The invention discloses a high voltage direct current system control method. VDDCFP is arranged after a VDCOL controller. A VDDCFP control process comprises the steps that S1, three-phase voltage amplitude of an inverter side is monitored in real time, and the voltage value of each sub harmonic of a voltage instantaneous value through Fourier decomposition; S2, voltage distortion current limiting is carried out, namely the harmonic distortion rate is calculated through the voltage amplitude of each sub harmonic after Fourier decomposition, and the maximum harmonic distortion rate in three-phase voltage is taken as a feedback signal; S3, direct current deviation current limiting is carried out, namely the difference between a direct current instantaneous value Id and a rated value Id_ref is calculated in a direct current setting value, and the difference is used as an input signal with the feedback signal in step S2 in a gain process; and S4, an optimizing algorithm is used to select the appropriate gain size. According to the invention, when the harmonic distortion rate of commutation bus voltage is high, direct current is reduced; and commutation is failed due to insufficient influence of harmonics on commutation voltage time area.

The invention discloses a double-T-type four-level inverter unit, application circuits containing the double-T-type four-level inverter unit and modulation methods of the circuits. The double-T-type four-level inverter unit mainly comprises a common-emitter double-T-type four-level inverter unit and a common-collector double-T-type four-level inverter unit; a single-phase four-level inverter circuit and a three-phase double-T-type four-level inverter circuit mainly comprise the common-collector double-T-type four-level inverter unit. The modulation methods mainly comprises two modulation methods of the single-phase four-level inverter circuit and one modulation method of the three-phase double-T-type four-level inverter circuit. Increase of output voltage level of the double-T-type four-level inverter unit and the application circuit topology thereof is favorable for reduction of the harmonic distortion of output voltage.

The invention discloses a built-in permanent magnet rotor structure of an axial flux motor. The built-in permanent magnet rotor structure comprises two rotor discs; each rotor disc comprises a rotor core with an annular cross section; each rotor core is formed by circumferentially winding a thin silicon steel sheet, and three layers of permanent magnet groups are uniformly embedded in the circumferential direction of each rotor core; each permanent magnet group comprises a first layer of U-shaped magnetism gathering structure permanent magnet combination, a second layer of U-shaped magnetism gathering structure permanent magnet combination and a third layer of linear structure permanent magnet which are sequentially arranged from the outer side of the rotor core to the circle center of the rotor core; the two rotor discs are installed on a rotating shaft in a manner that permanent magnet faces are opposite to each other, and a stator disc is arranged between the two rotor discs. According to the built-in permanent magnet rotor structure of the axial flux motor of the invention, the magnetism gathering capability of the permanent magnet rotor discs is stronger, and highly sinusoidal air gap flux density can be realized; the U-shaped permanent magnetcombinations and the linear permanent magnet combinations adopted, so that the salient pole effect of the motor can be improved, the reluctance torque is fully utilized, and the torque or power density of the motor is improved; and the silicon steel sheet is slotted and wound to form the rotor core, so that the machining is convenient and the structural strength is high.

The invention discloses a stator and rotor structure of a permanent magnet wheel hub motor. The structure comprises a stator, a rotor, a stator water hole, a rotor auxiliary groove and a plurality ofHalbach array permanent magnets, and adopts a structure of an inner stator and an outer rotor in order to enable the motor to have better output torque and rotational inertia, exciting windings are placed in winding grooves of the inner stator, two circular holes are formed in stator teeth, a water pipe is connected into the two circular holes to facilitate heat dissipation of the motor, the outerrotor is of a permanent magnet embedded type, each permanent magnet is magnetized through a Halbach array, and a plurality of Halbach array magnets are alternately arranged on the outer rotor in a Vshape and a W shape and are evenly distributed in the axial direction of a rotating shaft. According to the invention, the high magnetism, shielding property and unilateral magnetism gathering effectof the Halbach array magnetic pole can be utilized to reduce use of the permanent magnet, reduce the magnetic flux leakage and enhance the sinusoidal property of the air-gap magnetic field; and the purposes of reducing the waveform distortion rate and controlling the temperature rise are achieved by forming the auxiliary grooves in the rotor and forming the boiling water holes in the stator, so that the motor operates more safely and stably.

The invention discloses a model predictive direct power control method based on fuzzy control. According to the method, the error of active power and reactive power is used as the input of a fuzzy controller, a corresponding output is obtained through a fuzzy control rule, and a new objective function is thus constructed; the influence of a non-zero voltage vector and a zero voltage vector on therate of changes of the active and reactive power is analyzed according to a discretization prediction model of a system, the magnitudes of the active and reactive power are predicted under different voltage vector combinations, and an appropriate voltage vector combination is selected according to the principle that the objective function is minimum; and six switching tubes are driven to act by apulse width modulation technology so as to control the active and reactive power to follow given values thereof. The method saves the cost, improves the reliability of the system, reduces the distortion rate of current harmonics by compensating the active and reactive power, and can achieve floating active and reactive power by using predictive power control.

The invention discloses a narrow pulse suppression and electric energy quality improvement method for a matrix converter. The method is characterized in that: the matrix converter adopts double-voltage modulation; and when control signals of six switches for line voltage synthesis have narrow pulses in a certain switching period, six groups of new modulation functions for switch control are reconstructed and calculated according to the positions of the narrow pulses. The new functions are characterized in that: the new functions comprise instantaneous output current detection information; one of the six switches is kept in an off state; and the modulation functions simultaneously meet input current and output voltage modulation requirements. On the premise of no increase of the switching loss and the number of commutation times of the matrix converter, the number of the narrow pulses is effectively decreased, and the input and output waveform quality of the matrix converter is improved; and the method is particularly suitable for middle and high power places in which commutation time is long.

The invention discloses an improved modulation method based on NLM and PWM hybrid modulation, and the method is characterized in that the method achieves the voltage sharing of the capacitor voltage of a sub-module through employing a sorting algorithm for n-1 sub-modules of a modular multilevel converter, so as to achieve the optimal approximation to a fundamental wave; meanwhile, a sub-module isintroduced into each of the upper bridge arm and the lower bridge arm of the MMC to work in a high-frequency PWM mode, and the PWM carriers of the upper bridge arm and the lower bridge arm adopt thesame carrier. According to the invention, the harmonic distortion rate of the output phase voltage and phase current can be significantly reduced, the output electric energy quality is higher, the complex carrier generation and additional closed-loop voltage balance control are not needed, and the method has the advantages of simple control, low cost and easy realization.