72results about How to "Improve current quality" patented technology

The invention discloses a method for controlling an active power filter through model reference self-adaption fuzzy control. An alternating-current side current compensation controller designed according to the T-S fuzzy control theory and the Lyapunov method has all aspects of advantages of fuzzy control and self-adaption control, integrates the advantage of strong disturbance rejection performance of T-S fuzzy approximation and T-S fuzzy control on the premise that the overall system stability is guaranteed and utilizes the advantages that model reference and self-adaption control can overcome uncertainty of controlled objects and can achieve fast and accurate tracking, and therefore voltage is set through precise tracking of the voltage of a direct-current side capacitor, current is compensated for at the same time to quickly and accurately track a directive current signal, the compensation performance and system robustness of the active power filter can be greatly improved, harmonics can be eliminated, and the quick popularization of the active power filter is facilitated.

The invention discloses a modulation method for suppressing leakage current of a two-H-bridge cascaded inverter. The method comprises the following steps of calculating total parasitic capacitor voltage v<Nto> value of the two-H-bridge cascaded inverter at each switch-on state; selecting all switch-on states when the total parasitic capacitor voltage v<Nto) is -v<dc>; forming a combination of two switch-on states according to requirements of maximum level output, switch stress reduction and output power balance of a module; and comparing a modulation wave with a triangle carrier wave which is laminated by two same or opposite phases, and generating pulse width modulation (PWM) signals conforming to the above switch-on state combination, and allocating the PWM signals to corresponding pins. By the scheme, extra hardware cost is not needed, leakage current flowing into a power grid can be eliminated, and meanwhile, the leakage current of a single module is suppressed; and the method only requires two carrier waves to compare, the computation of a processor is reduced, and the implementation mode is simple.

The present invention provides a circuit for driving a flat panel display, including a storage capacitor, a transmission gate and a current-limiting transistor. A first terminal of the storage capacitor is coupled to a system voltage, and a second terminal of the storage capacitor is at storage voltage. A first input / output terminal of the transmission gate is coupled to the storage voltage, and the second input / output terminal of the transmission gate is coupled to the data current source. A first gate terminal of the transmission gate is coupled to the first signal; a second gate terminal of the transmission gate is coupled to the second signal. A gate terminal of the current-limiting transistor is coupled to the storage voltage, wherein a first source / drain terminal is coupled to the system voltage, and a second source / drain terminal provides current for driving the flat panel display.

In a method for current measurement in a multiphase current network, a conductive connection is produced between a plurality of the phases of the multiphase current network such that the plurality of the phases is short-circuited with one another. At a detection time, a current value flowing between the conductive connection and a first voltage potential is detected.

The invention discloses a resonance suppression method and system for an electrolytic-capacitor-free variable-frequency drive system, and belongs to the field of drive control of permanent magnet synchronous motors. The method comprises the steps: multiplying a bus voltage resonance component by the feedback proportional gain to obtain a damping current of the system; multiplying a damping currentby a current bus voltage to obtain equivalent damping power of the input side of an inverter, and converting LC oscillation of the input side of a driving system to the output side of the inverter; dividing the equivalent damping power of the input side of the inverter by the current output current of the inverter to obtain the equivalent damping output voltage of the inverter, and superposing the equivalent damping output voltage to the damping voltage of the alpha axis and the damping voltage of the beta axis according to the current of the alpha axis and the beta axis of the motor, so thatresonance components are absorbed by the current of the motor, and LC resonance suppression is realized. According to the invention, the LC resonance in the driving system can be effectively suppressed, the power factor of the driving system without the electrolytic capacitor can be improved, the calculation is simple, and the digital realization is easy.

The invention discloses a three-phase non-isolated grid connection converter and an air-conditioning system. The three-phase non-isolated grid connection converter comprises a direct current terminal, a first alternating current terminal, a second alternating current terminal, a third alternating current terminal, a first capacitor, a second capacitor, a first inductor, a second inductor, a third inductor, a first switch and a second switch, wherein the first capacitor and the second capacitor are connected between the direct current terminal and the ground in series; the first ends of the first inductor, the second inductor and the third inductor are respectively connected to the first alternating current terminal, the second alternating current terminal and the third alternating current terminal; the second ends of the three inductors are respectively connected to a first intermediate node, a second intermediate node and a third intermediate node; the third intermediate node is the intermediate node between the first capacitor and the second capacitor; the first ends of the first switch and the first switch are respectively connected to a first node and a second node; the second ends of the switches are connected to the direct current terminal; the third ends of the switches are connected to the ground; the fourth ends of the switches are connected to a third node; and the first ends of the first switch and the second switch are selectively connected to one of the second ends, the third ends and the fourth ends. Electric energy from a power grid, solar energy and a storage battery is selectively adopted by the air-conditioning system for providing electricity to a compressor of an air conditioner.

The invention provides an input / output linearization-based quasi-Z-source inverter photovoltaic grid-connected control method. According to the method of the invention, the input / output linearizationmodeling method of a QZSI (quasi-Z-source inverter) and a QZSI grid-connected control strategy are provided, and therefore, when the QZSI changes greatly at an operating point, a reference input voltage can be better tracked, the influence of a direct-current side on an alternating-current side can be decreased, and grid-connected current quality can be improved.

The invention relates to the technical field of grid-connected inverter control, and relates to a fractional phase compensation control method and device for an LCL grid-connected inverter under a weak power grid. The method comprises the steps: 1, respectively obtaining a voltage signal and a grid-connected current signal; 2, extracting voltage phase angle information; and generating a grid-connected current reference signal in the control system; 3, dividing the obtained grid-connected current signal into two paths, feeding back an inherent harmonic peak of an active damping suppression LCL grid-connected inverter through the grid-connected current, obtaining an error signal by subtracting the other path from the grid-connected current reference signal, and transmitting the error signal to a current controller for modulation; 4, after the error signal is modulated by a current controller, subtracting the error signal from a grid-connected current feedback active damping signal to obtain a modulated wave signal; and 5, comparing to obtain a control signal. The current controller structure is a proportional resonance parallel repetitive control structure with a fractional phase compensation function, the design is simple, and flexible fractional phase compensation can be provided under a weak power grid.

The invention discloses a dead zone compensation method for H-bridge topology. With the method adopted, the influence of odd-order harmonics brought by dead zone control can be decreased when the deadzone control is carried out, and output quality is improved. The method includes the following steps that: A, all working modes of an H-bridge topology circuit in corresponding modulation modes are analyzed; B, the average error voltage of the H-bridge topology circuit in each working mode is calculated; C, the current working mode of the H-bridge topology circuit is judged; D, an average error voltage corresponding to the current working mode of the H-bridge topology circuit which is judged in the step C is selected from the average error voltages calculated in the step B; and E, the averageerror voltage selected in the step D is converted to a PWM duty cycle compensation amount, and the PWM duty cycle compensation amount is superimposed on the original PWM duty cycle reference of the current H-bridge topology circuit.

According to a three-phase two-level inverter current ripple minimum effective value PWM method and system provided by the invention, a relation between a current ripple RMS and PWM is established by constructing a current ripple RMS prediction model, zero vector distribution is optimized in real time through a calculation result, and finally, a three-phase reference modulation signal is calculated by using an optimized zero vector distribution factor, and an output control pulse is generated. When the current ripple RMS of an inverter is reduced, the current THD and the switching frequency are reduced, the current quality is effectively improved, and the loss is reduced.