46 results about "Zero crossing distortion" patented technology

Ideal switch bridgeless PFC topologies are presented with the purpose of increasing the efficiency in power factor correction circuits and inverter applications. The topology also leverages the new GaN switches that are available. This patent offers also a very good solution for the Zero crossing distortion problem improving greatly the THD both in power factor correction and inverter applications.

The invention discloses a three-level VIENNA rectifier model prediction control system and method under a power grid unbalanced condition. The invention solves problems of the calculation of referencecurrent when the power network is unbalanced; the balance control of dc side voltage and DC side neutral point voltage; three-phase current zero-crossing distortion; control of unit power factor of grid current. The algorithm divides 25 voltage vectors into 6 sectors according to the current direction and 8 voltage vectors in each sector. Then five voltage vectors are selected according to the deviation of the neutral point voltage, and the optimal space voltage vector is obtained according to the value function, and the optimal space voltage vector controls the state of the switch transistor, so as to realize the control of the three-phase three-level VIENNA rectifier. The algorithm does not require the separation of positive and negative sequence of voltage and current, phase lock of voltage, current inner loop control module and modulation module when the power network is unbalanced.

The invention provides a correction policy of current zero-crossing distortion applicable to all one-way three-phase rectifiers (including three-phase VIENNA rectifiers, three-phase bridgeless rectifiers and all star-connection cascaded three-phase rectifier topologies) based on single-period control. The policy specifically includes following steps: firstly, determining related parameters of a system, then calculating a current distortion initial point, a distortion time and a boundary condition, and finally calculating a parameter introduced compensation amount based on the above parameters.According to the policy, based on the characteristic of single-period direct current control, crossed injection is performed on the feedback of current phase-shift control signals, and superpositionis performed with an original phase-shift feedback amount so that zero-crossing distortion generated by current phase shift of the energy one-way flow three-phase rectifier is corrected without increasing the complexity of the system. According to the policy, the realization is simple, the reliability is high, an effective correction method is provided for the current zero-crossing distortion problem occurring in a single-period control process, and the application range of single-period control is extended.

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 an alternating-current bypass single-phase photovoltaic inverter and a control method and control device thereof. In the method, closed-loop adjustment is carried out on the phase of modulating waves according to the phase difference between a grid-connected current signal and a grid-connected voltage signal so that the phase difference with a certain fixed value can be kept between the grid-connected current signal and the grid-connected voltage signal; the phase of the grid-connected current signal is locked to control an alternating-current bypass power switch tube so that switching of the alternating-current bypass power switch tube can be achieved during zero crossing of a current. The grid-connected current is not interrupted, the zero crossing distortion of the current is reduced or even eliminated, and a reactive current with any angle can be generated by an alternating-current bypass single-phase photovoltaic inverter. The invention further discloses the alternating-current bypass single-phase photovoltaic inverter.

The invention discloses a window control circuit for a power factor correction circuit, which comprises a sinusoidal half-wave voltage sampling circuit, a low-pass filter circuit and a comparison circuit, wherein the output end of the sinusoidal half-wave voltage sampling circuit is connected with the low-pass filter circuit; and the output end of the half-wave voltage sampling circuit and the output end of the low-pass filter circuit are connected with two input ends of the comparison circuit, and different connection ways can be adopted according to whether oscillating capacitance or oscillating resistance is used for deciding switching frequency of a PFC (power factor correction) controller. By adopting the window control circuit, the higher switching frequency is adopted in a region with smaller loss of the power factor correction circuit, that is the regions on two sides of voltage half-waves of an input power grid, the zero-crossing distortion of current of the input power grid can be prevented, and a higher power factor can be ensured; and the lower switching frequency is adopted in the main loss generation region, that is the middle region of the voltage half-waves of the input power grid, thereby reducing switching loss and improving the efficiency of the circuit.

The invention discloses a zero-crossing distortion suppression method of a dual-buck grid-connected inverter, and belongs to the technical field of power conversion. According to the method, a half-cycle SVPWM control method with ripple current negative feedback is led in through control on a three-phase dual-buck grid-connected inverter topology, negative feedback is carried out on a ripple current component of access currents, an amplitude value of the zero-passing portion of the currents is changed, shielding of half-cycle drive signals is achieved through a logical operation circuit, and the zero-crossing distortion problem of the dual-buck grid-connected inverter is solved on the basis that the dual-buck grid-connected inverter is high in efficiency and reliability is guaranteed.

The invention discloses a control method for output waveform improvement and low-loss short-circuit operation of an inverter and belongs to the technical field of the control method for a digital control inverter. The method comprises the steps as follows: when the inverter normally runs, four switch tubes work at the same time at the zero-crossing moment of inductive current through improving the control method of unipolar sinusoidal pulse width modulation and setting boundary conditions according to the inductive current ripple magnitude, and the inductive current is continuous; when the inverter is in ground short-circuit operation at an output side, the switch tubes are normally open to construct an inductive current free-wheeling circuit within a half cycle, so that the descending speed of the inductive current is reduced and the switching frequency of a power device during short-circuit operation is greatly reduced while inductive current limiting is achieved. According to the control method, zero-crossing distortion of an output voltage waveform during normal operation of the inverter is eliminated, and the system loss during ground short-circuit operation of the inverter is reduced.

A control architecture that overcomes limitations of conventional ac-dc converters and enables bidirectional active and reactive power processing is provided. In one implementation, for example, this may be achieved through the use of unrectified sensed ac signals in the generation of the control commands for the converter. This control architecture, in this example implementation, eliminates or at least reduces zero crossing distortions in the ac current of the converter even with relatively low bandwidth controllers. The concept can be applied to different power stage topologies.

The invention discloses a full-duplex communication method and device based on a power line. The method comprises the following steps that: a first device transmits a first code element to a second device through the zero-crossing distortion of two zero-crossing points (P1 and P3) in four zero-crossing points in waveform signals of two continuous periods transmitted on the power line; and the first device receives a second code element transmitted by a second device through the zero-crossing distortion of the other two zero-crossing points (P2, P4) in the four zero-crossing points in the waveform signals of the two continuous periods transmitted on the power line. According to the method and the device, the technical problems of low transmission rate and difficulty in realizing full-duplex communication caused by the representation of a binary bit through two continuous periods in the prior art are solved, the technical effect of full-duplex communication based on the power line is realized, and the channel utilization ratio of the power line is increased simultaneously.

The invention provides a control method for suppressing zero-crossing distortion of a line current of a three-phase star-connected controllable rectifier with one-way flow of all energy. The method comprises: step one, according to conditions met by midpoint voltages uAN, uBN, uCN between the input terminal connected to an inductor of a three-phase rectifier circuit and a three-phase power sourcein a non-distortion state of a three-phase input current, corresponding given value u*AN, u*BN, u*CN are provided; step two, on the basis of determination conditions, whether a certain phase of inputcurrent enters a zero-crossing distortion zone is determined; step three, if all phases of input currents work in a normal working zone, give values u*AO, u*BO, u*CO of input terminal voltages of thethree-phase star-connected rectifier are equal to the u*AN, u*BN, u*CN; and step four, if a certain phase of input current isK enters the zero-crossing distortion zone and K is equal to A, B, and C, acorresponding phase of rectifier bridge input terminal voltage uKO of the current becomes zero and given values of another two phases of rectifier bridge input terminal voltages are corrected, wherein u*HO=u*HN-u*KN, the H is equal to A, B, and C, and H is not equal to K, and fundamental components of the other two phases of rectifier bridge input terminal voltages change with a new given value.Therefore, the zero-crossing distortion of the input current of the three-phase star-connected controllable rectifier is suppressed.

The invention provides an optimal modulation method and an optimal modulation system for a non-isolated alternating-current bypass single-phase grid-connected inverter. The method comprises the following steps: acquiring the phase angle Omega(t) of the voltage of a power grid; acquiring the phase angle Omega(t)+Beta of the output voltage of an inverter; and judging an interval, needing insertion of a dead zone, of the output voltage of the inverter according to the power factor angle Alpha and the phase angle difference Beta between the output voltage of the inverter relative and the voltage of the power grid, and inserting a dead zone between a bypass freewheeling switch and a main switch in an interval in which the output power of the inverter is negative. By using the optimal modulation method for a non-isolated alternating-current bypass single-phase grid-connected inverter provided by the invention, the problem of zero-crossing distortion caused by ignorance of inductance voltage and the problem of reverse charging caused by insertion of a dead zone for the existing modulation method are solved.

The invention discloses a buck-boost tri-level inverter based on Zeta. The buck-boost tri-level inverter based on Zeta is formed through output-series of two improved Zeta circuits which can realize buck-boost output to realize DC/AC single-phase inversion. The basic function of the inverter is to realize buck-boost inversion, and when the input DC voltage is lower or is large in the changing range, the double Zeta buck-boost tri-level inverter can still complete the inversion function normally and can realize AC output with stable points. The buck-boost tri-level inverter based on Zeta has the advantages of being high in reliability, being simple in circuit structure, being easy for control, being high in efficiency, reducing the zero-crossing distortion of the output voltage, being long in service life, having good harmonic wave frequency spectrum, being low in the voltage stress borne by switch tubes, and being low in the loss of switches.

The invention provides an SPWM method of a single-phase full bridge inverter. The single-phase full bridge inverter comprises a main circuit and a control system. The SPWM method comprises the following steps: (A) detecting whether a modulation voltage is in phase with an output voltage of the single-phase full bridge inverter by virtue of the control system, when the modulation voltage is not in phase with the output voltage, carrying out a step (B), and when the modulation voltage is in phase with the output voltage, carrying out a step (C); (B) starting a bipolar SPWM modulation manner by virtue of the control system; (C) starting a unipolar SPWM modulation manner by virtue of the control system; (D) returning to the step (A), and carrying out looping execution. The SPWM method has the beneficial effects that the advantage that the zero-crossing distortion does not exists in the bipolar modulation manner and the advantage of low consumption of the unipolar modulation manner are combined, namely, the inverter works in the bipolar modulation manner in a zero-crossing section of the output voltage and works in the unipolar modulation manner in other sections, the advantages of the two modulation manners are integrated, and the disadvantages of the two modulation manners are abandoned.

The present invention discloses a three-phase dual-buck grid-connected inverter current zero-crossing distortion inhibition method. The voltage of a power grid is collected, the critical point of inductive current of the inverter of a three-phase dual-buck grid-connected inverter controlled by half cycle SPWM entering an intermittent region is determined according to the voltage phase angle [Theta] of the power grid obtained through software phase-locked loop, a compensation duty ratio function at present is obtained through calculation and is overlapped into an original modulated wave to allow the current ripple in the intermittent interval of the inductive current of the inverter to be gradually reduced, and the average value of the inductive current tends to sinusoidal variation in the intermittent interval around the zero crossing so as to effectively eliminate the current zero-crossing distortion on the premise without extra adding devices and ensuring the system stability.

The invention relates to a control method and device for solving space vector pulse width modulation current zero-crossing distortion. The method comprises the following steps: to begin with, collecting each phase of phase voltage; then, judging whether phase voltage crosses zero in a positive zero-crossing manner or a negative zero-crossing manner; when the phase voltage crosses zero in a positive zero-crossing manner, a positive/ negative carrier switching point is arranged within COMP-PRD; and when the phase voltage crosses zero in a negative zero-crossing manner, the positive/ negative carrier switching point is arranged within 0-COMP. The method can effectively increase switching point switch tube conduction time to reduce abrupt change of zero crossing point duty ratio, thereby reducing zero-crossing point current distortion. The method is simple in control process, reduces control complexity and improves control reliability.

The invention discloses a DSOGI-FLL-based three-phase converter non-dead-zone half-period modulation method. The DSOGI-FLL-based three-phase converter non-dead-zone half-period modulation method comprises the steps of: subjecting current signals of a three-phase converter to Clark transform; performing filtering and frequency-locking treatment on two phases of current signals by means of a DSOGI-FLL module, so as to obtain a fundamental wave current signal and an orthogonal signal thereof, and performing Clark transform on the fundamental wave current signal and the orthogonal signal; comparing a voltage modulation signal with a carrier signal in a half-period modulation module to obtain an initial driving signal; and allocating the initial driving signal according to current polarities ofthe fundamental wave current signal after inverse transformation, so as to obtain a non-dead-zone half-period driving signal which can be enabled along with alternation of the current polarities of the fundamental wave current signal after inverse transformation, and controlling the three-phase converter to realize non-dead-zone half-period modulation. The non-dead-zone half-period modulation method can obtain the current polarities precisely under the conditions of three-phase current balance, unbalance and presence of harmonics, realize the non-dead-zone half-period modulation of the three-phase converter, and reduces current zero-crossing distortion.

According to the invention, a method and an amplifier e.g. of the class D type, in particular connected as class BD, wherein an audio signal is pulse-with modulated in that two sets of switches are adapted to make and break signal paths transferring pulses representing the non-inverted or inverted part of the audio signal, comprise attenuating noise and zero crossing distortion which occur because of crosstalk between modulator and control circuit halves in the amplifier. Noise and zero crossing distortion are attenuated by delaying the pulses which represent the non-inverted part and the inverted part, respectively, of the audio signal relative to each other, when the audio signal is in the vicinity of the value 0, thereby achieving modulation of the audio signal which contains characteristics from pulse with modulation of both class AD and BD type. The advantage of this is that at low signal levels the amplifier obtains the linear properties of the class AD amplifiers at zero crossing and the low noise of the class BD amplifier. The pulse-with modulation type is here called class ABD.

The invention discloses a spatial high-voltage high-frequency high-power interleaved three-level PFC converter and method thereof, the converter comprising four high-power fast recovery diodes, an input filter capacitor C1, two boost inductors, four power switching transistors, three freewheel diodes and two output capacitors; The circuit topology skillfully combines the interleaved parallel PFC technology with the three-level PFC technology, The input current ripple after interleaved parallel connection is smaller than that of three-level PFC of a single branch. The branch current is approximately half the input current, thus the current stress of the switching device is reduced, and the voltage stress of each switching device is also reduced by half, which provides a powerful technical support for the research of the high-power PFC converter. The voltage and current stress and the inductance volume of the switching device of the converter are reduced as much as possible while the zero-crossing distortion of the input current is improved.