137results about How to "Reduce THD" patented technology

The present invention provides a modular parallel three-level Vienna rectifier, a control system and a method. The present disclosure effectively suppresses the zero-sequence circulation of a system,and the waveform quality of the input current is improved remarkably, so the invention is suitable for the working conditions that the current distribution proportions of two three-level Vienna rectifier modules are equal and unequal and the input filter inductances are equal and unequal. The elimination of the zero-point distortion of the input current fully considers the influence of the filterinductor on the relative position of the voltage vector and the current vector. The effect of the input current zero-crossing distortion is better than that in a conventional method, and the total harmonic distortion rate of the input current is reduced.

The invention discloses a maximum power point tracking controller for a three-phase photovoltaic power generation system. The controller mainly comprises a BOOST type DC/DC converting circuit, a three-phase inversion circuit, a control circuit and a power circuit. The technical scheme includes that a variable-structure fuzzy control method is applied to MPPT (maximum power point tracking) of photovoltaic power generation so that tracking precision can be improved, and the method can effectively realize maximum power point tracking when illumination and temperature vary. By means of variable-structure fuzzy control, different fuzzy sub-controllers are designed according to different working conditions, the discourse domain range, control rules, parameters and the like of the fuzzy sub-controllers are different, the fuzzy sub-controllers form a variable-structure fuzzy controller, and accordingly one fuzzy sub-controller constantly enables the system to achieve the optimal control quality in system running.

The invention discloses a switch power supply and a controlling circuit and a controlling method thereof. Through regulating a first multiplying input signal, waveform-following input voltage of an average current is inputted by the switch power supply, so that a harmonic component of an input electric current of the switch power supply is reduced, the THD (Total Harmonic Distortion) is lowered and then the power factor of the switch power supply is increased.

The invention discloses a novel topology of an electric spring and a control method of the novel topology. Along with increase of grid connection capacity of renewable energy power generation of wind energy, solar energy and the like, the stability of a power system faces a severe test; and when large-scale distributed grid connection of renewable energy power generation is carried out, the probability that a power grid, particularly a micro grid is broken down is gradually increased, so that the electric spring is provided primarily aiming at the instability of renewable energy power generation in the micro grid. According to the novel electric spring topology structure and control strategy provided by the invention, the stability of critical load voltage can be ensured; fluctuation of input voltage can be transferred to non-critical load; and the condition that the energy consumption of the non-critical load is kept in accordance with the change trend of the input voltage can also be ensured. The monotonous change relationship between the active power and the input voltage realized by the novel topology cannot be realized by an existing electric spring, so that the novel topology of the electric spring has relatively high practicality when the amplitude of the voltage increases along with increase of generation power.

The invention discloses a permanent magnet synchronous motor prediction current control method and device. According to the predictive current control method, the direct-current bus voltage, the three-phase current, the rotor rotation electrical angular velocity and the rotor electrical angle of the permanent magnet synchronous motor at the current moment are sampled; the reference voltage vectorof the static coordinate system is calculated and obtained, the multi-region division method for basic voltage vector sectors is proposed, an optimal vector is selected under the condition of considering overmodulation, and the accurate simplified expression of the optimal action time of each basic voltage vector is finally given. Therefore, the method provided by the invention can improve the existing overmodulation optimization method and can reduce the use of trigonometric functions, greatly reduces the calculated amount, further reduces the quadrature-direct axis current ripples of the permanent magnet synchronous motor, reduces the torque ripple and the total harmonic distortion rate of the stator current, and improves the steady-state performance of the system.

The invention discloses a three-phase NPC photovoltaic grid-connected inverter based on repeated control. The inverter is based on an NPC topology structure. A system is composed of an LC filter module, a Clark/Park transformation module, a d-axis current regulator, a q-axis current regulator, a composite controller, a Clark/Park inverse transformation module and an SVPWM space vector module, wherein the composite controller is formed by connecting a PI controller and a repetition controller in parallel. Since system grid connection is needed, the reference signal of the q-axis current regulator is zero. Compared to the prior art, the inverter provided by the invention can realize inverter unit power factor grid-connected operation, can effectively inhibit periodical interference in a photovoltaic system at the same time, and can improve the system stability and reliability.

The invention discloses a matrix converter comprising a source damping filtering unit. The matrix converter comprises an input power source, an LC input filtering unit, a switch matrix and a microprocessing unit. Currents provided by the input power source are input to a load successively through the LC input filtering unit and the switch matrix, the microprocessing unit, through control over the resonance damping of an LC filter, controls input current waveforms of the LC filter so as to obtain expected output voltages, and according to the expected output voltages, distributes pulses to each switch tube in the switch matrix to control the work state of each switch tube in the switch matrix. The invention also provides a control method of the matrix converter comprising the source damping filtering unit. The dynamic characteristic is improved, the power supply current harmonic wave content can be reduced, a power supply side is enabled to be always close to a unit power factor, and the efficiency of the matrix converter is improved. At the same time, resonance appearing in the LC filter is effectively inhibited, the total harmonic wave distortion rate of power supply currents is reduced, and the influence exerted by the matrix converter on a power network is decreased.

The invention discloses a multiple symmetrical winding magnetic flux switching motor and a winding design method thereof. The method is based on exertion of complementarity of windings of the magnetic flux switching motor with maximization of induced electric potential of each phase as the principle, and coil compositions of a phase winding, coil compositions of a set of symmetrical windings and coil connection types of all phase windings are obtained in sequence through optimizing the phase difference between two sets of adjacent symmetrical windings. The winding design method is clear in thinking and easy to operate. The multiple symmetrical winding magnetic flux switching motor has the advantages of being high in no-load induced electric potential sine degree and winding utilization rate, large in torque output and small in electromagnetic torque pulsation, and superior motor performance is embodied.

This invention discloses an inverse power supply for analog-controlling instantaneous voltages, in which, PID controller output end is connected with the input of the inverse supply, the output of which is connected with the input of the voltage sensor and the load, its output and a reference volume are connected with the negative and positive input of a subtracter, the output of which is connected with the input of the PID controller and the inverse supply is connected with the DC supply, which has the advantages of quick dynamic response, low rate of general harmonic aberration and accurate stability under non-linear load.

The invention discloses a static synchronous compensation circuit. The static synchronous compensation circuit comprises a static synchronous compensator. The output end of the static synchronous compensator is connected with a capacitor Cc in series and then connected into a power distribution system. The invention further discloses a decoupling control method based on the static synchronous compensation circuit. The decoupling control method based on the static synchronous compensation circuit comprises the steps that firstly, the alternating-current voltage us on a net-side PCC and the alternating-current voltage ucs on the capacitor Cc are detected through a voltage inductor, and a reactive compensation current ic is detected through a current inductor; secondly, the voltage udc on a direct-current capacitor C is obtained through a direct-current voltage detection circuit; thirdly, a balance equation of voltage on the alternating-current side of a VSC and a relational expression between the voltage and the current on the capacitor Cc are listed; fourthly, double loop control of an outer voltage loop and an inner current loop is adopted by the static synchronous compensator. By the adoption of the static synchronous compensation circuit and the decoupling control method based on the static synchronous compensation circuit, the starting performance is remarkably improved, the voltage stress of a switching device is reduced obviously, and the total harmonic distortion of an output current of a compensation device is reduced.

The invention discloses a low-frequency oscillation inhibition method of a high-speed train based on sliding mode control of an extended state observer. The method comprises the steps of constructinga state space model of a net side rectifier of the high-speed train, establishing the extended state observer on the state space model by taking load change as disturbance to obtain an estimated loadpower value, selecting an output of a control system by combining a control objective, establishing two sliding mode faces based on outer ring voltage control, obtaining a reactive component referencevalue of net side current by combining the estimated load power value, completing calculation of a sliding mode face expression, calculating a switching function, multiplying the switching function with direct current side voltage to obtain control voltage, transforming the control voltage into an alpha-beta coordinate system component, and outputting control pulse by sine pulse width modulation.The method takes all external disturbance as one state variable, so that the direct current side voltage can keep constant under sudden change of a load; the net side current can have a low total harmonic distortion rate; and the electric energy quality and the stability of a train net coupled system can be ensured.

The present invention relates to a buck type single-stage LED drive circuit of a unity power factor, and discloses the buck type single-stage LED drive circuit of wide input voltage range and low THD and unity power factor. A forestage circuit adopts a time division multiplexing buck circuit and a buck-boost circuit to be integrated with a back-stage flyback convertor, so that an inherent dead zone of a conventional buck type PFC circuit AC input current is eliminated, and accordingly, the THD of the input current is reduced. By the staged working, the circuit can work in a buck mode and also can work in a buck-boost mode. A buck-boost switching tube works when an input voltage is less than an output voltage, so that the conduction dead zones can be reduced. Meanwhile, two switching tubes in the circuit are in common ground, so that the design of a driving control circuit is simpler, and the unity power factor is realized.

The invention relates to a charger harmonic suppression control method. The invention discloses a harmonic suppression method for a charger of an electric vehicle. The harmonic suppression method comprises the following steps of: 1) constructing a charger topological structure form of a front LCL type filter single-phase PWM (Pulse Width Modulation) rectification mode; 2) establishing a mathematical model of the single-phase PWM rectification charger; 3) analyzing harmonic characteristics in the electric vehicle charger model; 4) analyzing a harmonic suppression method based on a PI current regulator, and establishing a charger system PI control structure; and 5) establishing a PWM rectification charger PIRC composite repetitive controller by adopting an RC and PI current composite control method, optimizing the duty ratio of PWM to suppress the generation of low-order harmonics, and applying the PWM duty ratio to the suppression of the grid-side current harmonics of the charger. The odd harmonic in the grid-side current of the PWM rectification charger can be well inhibited, the open-loop gain of an electric vehicle charger control system is increased, the steady-state and dynamic performance of the charger system is improved, zero-static-error tracking of the grid-side current of the charger is achieved, and the method has a certain promotion effect on popularization and application of electric vehicles.

The invention belongs to the electric power electronic technology field and discloses a full digit single period power factor correction circuit based on triangular wave pulse modulation. The full digit single period power factor correction circuit based on triangular wave pulse modulation comprises a Boost power converter, a digital analog conversion circuit and a control circuit, wherein the control circuit comprises an output voltage difference module, a voltage loop circuit compensation module, a value calculating module, a PWM module and a grid driving module. The beneficial effects are that: the full digit single period power factor correction circuit discloses by the invention can obtain the average value of the Boost inductor current without the needs of the input current sampling circuit of the complicated structure or the high speed digital analog converter, and guarantee that the single-period PDC converter obtains the high power factor and low THD under the full loading condition through a relatively simple control structure and relatively less control circuit hardware resources.

The invention discloses a bridgeless electrolytic-capacitor-free low-ripple-wave high-power constant-current power supply of an LED lamp. The bridgeless electrolytic-capacitor-free low-ripple-wave high-power constant-current power supply of the LED lamp comprises an alternating-current power supply circuit, a control circuit, a coupling-out circuit and a ripple wave restraining circuit. The alternating-current power supply circuit comprises a constant-current drive chip U1, a constant-current drive chip U2, an alternating-current positive half-wave current loop and an alternating-current negative half-wave current loop, wherein the constant-current drive chip U1 and the constant-current drive chip U2 are controlled by the positive half-wave and the negative half-wave of an alternating-current power supply Uin. The current of the alternating-current positive half-wave current loop and the current of the alternating-current negative half-wave current loop both flow through a primary winding N11 and a primary winding N12 of a magnetic integration transformer TR so that an induced voltage can be generated on a secondary winding NV1 and a secondary winding NV2, and then the working voltage of the constant-current drive chip U1 and the working voltage of the constant-current drive chip U2 are provided through the control circuit. An induced secondary current is generated on a center post secondary winding N2 and is output to the loaded LED lamp through the coupling-out circuit. The ripple wave restraining circuit restrains current ripple waves. According to the bridgeless electrolytic-capacitor-free low-ripple-wave high-power constant-current power supply of the LED lamp, a bridge rectifier and an electrolytic capacitor are not adopted, so that the electric power is increased, the reliability is improved, the drive capability of the chips is improved through expanded current, the working temperature of the chips is lowered, the service life of the chips is prolonged, the constant-current precision is high, the current ripple waves are small, the LED lamp does not flicker, and the circuits meet the environmental-friendliness principle.

The invention discloses a step-down switching power supply and a control method thereof. By squaring an input voltage sampled signal, a waveform of average current inputted by a step-down circuit follows the input voltage, so that the harmonic component of input current of a step-down switching power supply is reduced, the THD (Total Harmonic Distortion) is lowered, and the power factor of the step-down switching power supply is improved.

The invention provides a multi-segment-type cascading driving circuit which comprises a power module, a plurality of control modules sequentially connected onto an output line of the power module, a plurality of load modules sequentially connected in series on the output line of the power module and correspondingly connected with the plurality of control modules as well as controlled by the corresponding control modules to run, and a plurality of switching modules connected between the corresponding control modules and the load modules and used for controlling the load modules to run through commands of the control modules, wherein the output terminal of the control module which is lastly connected to the output line of the power module is connected with a stable resistor; each switching module is formed by MOS (Metal Oxide Semiconductor) field effect transistors; each load module is formed by light emitting diodes; a current-limiting resistor is connected between the power module and each MOS field effect transistor; and the sequence of the plurality of control modules connected to the output line is opposite to the sequence of the plurality of correspondingly-controlled load modules on the output line. As the multi-segment-type cascading driving circuit is used, the efficiency and the power factor of a power supply are improved.

The invention discloses a state-tracked digitally-controlled inverter power supply being characterized in that: an input end of a prefilter is connected with a reference amount Ur; an output end of the prefilter is connected with a positive input end of a subtracter; an output end of the subtracter is connected with an input end of a one-stroke delay module; an output end of the one-stroke delay module is connected with a control end of a inverter and a second input end of a prediction observer; a first input end and a third input end of the prediction observer are respectively connected with output ends of a current sensor and a voltage sensor; an output end of the prediction observer is connected with an input end of a state gain matrix; an output end of the state gain matrix is connected with a negative input end of the subtracter; an output end of the inverter is connected with an input end of the voltage sensor and a load; a direct current end of the inverter is connected with a direct current power supply; a load current in the inverter is connected with an input end of the current sensor. The inverter power supply has good dynamic and static characteristics and has low waveform distortion of the output voltage. The invention is widely used in various power supply systems comprising an alternating current stabilized power source.

The invention discloses a highly-efficient inverter fractional order voltage and frequency control method under a microgrid off-grid mode. A mechanism modeling method and abc/dq coordinate transformation are employed to establish a state space model of an inverter in dq coordinates under the microgrid off-grid mode. Droop control, fractional order voltage PI control and fractional order current PI control are employed as voltage and frequency control method. The weighted values of two performance indexes including an integral value of the product of a voltage offset absolute value and time and the integral value of the product frequency offset absolute value and time serve as fitness functions. A colony evolution method based on adaptive variation operation is designed to optimize and set parameters of a fractional order controller, and optimized control signals generated after coordinate transformation are transmitted to a space vector pulse width modulation module, thereby realizing optimized operation of an inverter under the microgrid off-grid mode. Optimized voltage and frequency control effects under complex conditions and the microgrid off-grid mode can be realized.