44results about How to "Reject common mode voltage" patented technology

The invention discloses a finite control set model predictive control method for a multi-motor control system. The finite control set model predictive control method is applied to the multi-motor control system which is composed of m permanent magnet synchronous motors. The finite control set model predictive control method for the multi-motor control system comprises the steps that the electrical quantity of the multi-motor control system is acquired; virtual reference voltage vectors are predicted and a value function is optimized, wherein for each motor, the corresponding virtual reference voltage vector existing at the k moment is calculated, and the value function is established; the process of optimizing the value function is simplified according to the vector zoning method; the common mode voltage of the multi-motor control system is restrained by adding the common mode voltage constraint to the method. Compared with a traditional finite control set model predictive control (FSC-MPC) method, the FSC-MPC method for the multi-motor control system has the advantages that on the basis that the control effect of the traditional method is maintained, the method implementing time is effectively shortened; meanwhile, cooperative control over the speeds of the multiple permanent magnet synchronous motors is achieved, and the purpose of restraining the common mode voltage is achieved.

A motor drive and a choke therefor are disclosed, wherein the choke comprises a magnetic core with an inner leg and two outer legs, and four coils, which may be connected in DC current paths in the motor drive. First and second differential coils are wound around first and second outer legs, respectively; and first and second common-mode coils are wound around the inner leg of the choke. The first and second differential coils smooth the DC current on a DC bus in the motor drive, and the first and second common-mode coils suppress common-mode voltages in the motor drive. Also disclosed is a method for suppressing common-mode voltages in a motor drive.

The invention discloses a method for modulating space vectors of double inverters, and belongs to the field of inverter control. The method is used for solving the problem that in the prior art, when basic space voltage vectors which do not generate common-mode voltage are selected to modulate voltage, the utilization of direct-current bus voltage is low. The method comprises the steps that a space voltage vector plane is divided into six sectors, a reference voltage vector is divided into two vectors, one vector is equivalent to the operation that one of the double inverters is clamped in a specific switching state, and the other vector is modulated by the other inverter in six sub-sectors of the inverter to be achieved; modulation is conducted within the maximum voltage range, an equivalent zero vector distribution factor is introduced when the vectors are synthesized, the common-mode voltage generated in the process of synthesis of the basic voltage vectors is counteracted with common-mode voltage generated by a zero vector, and common-mode voltage of the double inverters is restrained.

The invention discloses a carrier implementation method for low common-mode voltage modulation of a three-phase five-level inverter. The carrier implementation method comprises the steps of sampling a three-phase original modulation wave, and calculating a minimum zero-sequence component; determining the carrier phase according to the three-phase original modulation wave and the minimum zero-sequence component; superposing the minimum zero-sequence component on the three-phase original modulation wave so as to acquire a three-phase intermediate modulation wave; determining an upper boundary and a lower boundary of a located carrier according to the position of the three-phase intermediate modulation wave; calculating the distance between the three-phase intermediate modulation wave and the upper boundary and the distance between the three-phase intermediate modulation wave and the lower boundary, and solving the minimum distance between the upper boundary and the lower boundary; solving a zero-sequence component by using the acquired minimum distance; superposing the zero-sequence component on the three-phase intermediate modulation wave so as to acquire a corrected three-phase modulation wave; and finally comparing the corrected three-phase modulation wave with a three-phase carrier, and generating a PWM wave control five-level inverter. The carrier implementation method disclosed by the invention can realize the advantages of low common-mode voltage, small flying capacitive voltage fluctuation, low harmonic distortion and the like. Because of adoption of carrier implementation, the method is simple to implement, convenient to control and easy to be popularized to actual engineering.

The invention discloses an open winding permanent magnet motor current control method based on limited state prediction. The open winding permanent magnet motor current control method based on the limited state prediction comprises that: double-closed-loop control is adopted; a speed external ring controller consists of a state space controller having a freedom degree and a current reference value is generated; a current internal ring controller adopts a limited state model prediction controller and generates sixty-four switch combinations during power supplying; the limited state model prediction controller predicts a current perdition value corresponding to a next moment under an act of each switch combination according to a motor discrete mathematical model; an evaluation function of a switch function which is only constituted by a current error item and a common mode voltage suppression term; a switch combination which makes the evaluation function value smallest as an optimal switch combination to act on a system to realize current control while common mode voltage is suppresed. The open winding permanent magnet motor current control method based on limited state prediction overcomes a problem that a traditional open winding permanent magnetic motor vector control method is complex in structure and needs an extra space voltage vector regulation link.

The invention relates to a space vector modulation method capable of suppressing the common-mode voltage of a dual-Y shift 30-degree six-phase motor. The method includes the following steps that: (1) 64 basic vectors are generated; (2) 12 intermediate vectors are constructed; (3) the action time of 8 basic vectors is calculated; and (4) the action sequence of the 8 basic vectors is designed. With the space vector modulation method of the invention adopted, the common-mode voltage of the dual-Y shift 30-degree six-phase motor can be effectively suppressed, and the current response, magnetic flux linkage track, electromagnetic torque and rotation speed performance of the motor is unchanged.

The invention discloses a converter device used for a wind generator system. The converter device comprises a filter, a first converter, a second converter, a first capacitor and a second capacitor, wherein the filter is connected to a wind-driven generator of the wind generator system; the first converter is connected to the filter; the second converter is connected to a voltage transformer on the power network side; and the first capacitor and the second capacitor are connected in series between a positive direct-current bus and a negative direct-current bus which are used for connecting the first converter and the second converter, neutral points of the positive direct-current bus and the negative direct-current bus are connected, and nodes of the first capacitor and the second capacitor are grounded.

The disclosed frequency converter is able to filter out common mode signal existed in voltage output from existing frequency converter. Output end of drive circuit in three phases is connected to input end of C5 and PWM inverter. C5 is connected to C6, end of negative pole of Vs1, end of positive pole of Vs2, R4 and non-homonymic end. C6 is connected to output end of drive circuit in three phases and input end of PWM inverter. Output end of the PWM inverter is connected to homonymic ends of (L21-L23) respectively. Collector of T1 is connected to end of positive pole of Vs1, and emitter of T1 is connected to homonymic end of L1 and emitter of T2 etc. the invention eliminates negative effect brought by frequency converter, and possesses advantage of IC module form.

The invention discloses a virtual space vector modulation method of a voltage-type three-level middle-point clamping converter. The virtual space vector modulation method comprises the steps of building a new virtual vector space diagram of a three-level NPC converter; determining whether a reference voltage vector v<ref> is within a first fan section of the new virtual vector space diagram of thethree-level NPC converter or not; judging a triangle where the reference voltage vector v<ref> is located; calculating action time of each virtual vector according to the triangle where the referencevoltage vector v<ref> is located; calculating action of each actual vector according to the action time of each virtual vector; calculating a switch state output sequence corresponding to a vector inthe triangle according to the action time of each actual vector; and controlling a switch state of each switch on the voltage-type three-level middle-point clamping converter according to the switchstate output sequence corresponding to the vector in each triangle so as to complete virtual space vector modulation of the voltage-type three-level middle-point clamping converter. By the modulationmethod, full-modulation degree and full-power factor DC capacitance voltage fluctuation control can be achieved.

The invention provides a zero common-mode voltage and input reactive power control method of a direct matrix converter, not only provides a space vector modulation method of the zero common-mode voltage of the direct matrix converter, but also provides a control method for controlling input reactive power on the basis of the modulation strategy. According to the modulation method, a clockwise rotation vector and an anticlockwise rotation vector are adopted at the same time, and expressions of the duty ratios of the vectors are given. The modulation method can achieve zero common-mode voltage of the direct matrix converter, common-mode current is effectively restrained, the service life of a motor is facilitated to be prolonged, and electromagnetic interference to surrounding equipment is reduced. According to the degree of freedom of the duty ratio in the modulation strategy, a control method for simply realizing input reactive power is provided. In addition, the control method provided by the invention does not need complex sector judgment; and the control method is small in calculation amount and suitable for practical application.

The invention discloses a finite set model prediction control method for suppressing a common-mode voltage of a five-phase inverter. The method specifically comprises the steps that ten large vectorsoutput by a five-phase inverter are used for synthesizing a virtual voltage vector, four adjacent large vectors are selected to synthesize ten virtual effective voltage vectors in an alpha-beta subspace, and two large vectors opposite in direction are selected to synthesize a virtual zero vector; the virtual voltage vector is used as a vector control set, and a current change trend is predicted through a simplified prediction model; an optimal virtual voltage vector is selected by using a simplified evaluation function; and finally a symmetrical switch sequence is designed to output an optimalvector. According to the invention, the common-mode voltage and the low-order harmonic wave current are effectively suppressed, so that the steady-state performance of the output current of the inverter is improved; and due to the characteristic that the virtual voltage vector suppresses the common-mode voltage and the low-order harmonic waves, a prediction model and an evaluation function are simplified, the algorithm calculation complexity is low, and digital implementation is easy.

The invention provides a three-level three-phase four-leg inverting system, a control method of the three-level three-phase four-leg inverting system and a controller. The method comprises steps of judging if direct current side voltage of the three-level three-phase four-leg inverting system is lift up to be more than a preset high limit value through a controller; when the direct current side voltage is lift up to be more than a preset high limit value, controlling two middle switch tubes to open normally and upper and lower switch tubes close normally of a fourth arm of the three-level three-phase four-leg inverting system, so that the three-level three-phase four-leg inverting system is converted to be a three-phase four-wire system, a point in an alternating current filter of the system can be returned, and the output common mode voltage is controlled; when the direct current side voltage is high, the common mode voltage of the system is inhibited, thus the three-level three-phase four-leg inverting system maintains the function of carrying imbalance load; meanwhile, the adaptation is enhanced, and the application scale of the three-level three-phase four-leg inverting system is enlarged.

The invention provides an open-winding six-phase inverter modulation method for inhibiting a third harmonic and a common-mode voltage. The method comprises the following steps: mapping a six-dimensional electromagnetic quantity of a six-phase motor into three orthogonal two-dimensional subspaces; obtaining frequency components corresponding to the orthogonal two-dimensional subspaces; mapping thethird harmonic component to o1-o2 subspaces according to the frequency components corresponding to the orthogonal two-dimensional subspaces, wherein the o1-o2 subspaces refer to zero sequence subspaces; controlling the plane projection of a voltage vector in the o1-o2 subspace to be 0; controlling the common-mode voltage of a six-phase inverter of an independent bus topology to be 0 so as to obtain a voltage vector used for PWM modulation; and controlling the open-winding six-phase inverter according to the voltage vector used by the PWM modulation. Therefore, the common-mode voltage and the third harmonic current of the open-winding six-phase permanent magnet synchronous motor can be suppressed at the same time, and the motor loss caused by the harmonic current is reduced while the common-mode voltage is suppressed.

The invention discloses a high-performance model predictive control algorithm for a diode clamping type three-level converter, which belongs to the field of power electronics and power transmission, and comprises the steps of selecting a basic voltage vector with smaller common-mode voltage amplitude as a control set, reducing the common-mode voltage amplitude by half, and reducing the number of iterations from 27 to 19; and forming a pair of redundant vectors to control neutral-point potential balance by constructing a virtual voltage vector which has the same amplitude and direction as the basic voltage vector and has different neutral-point currents or a neutral-point current of zero with the basic voltage vector. Compared with a traditional model predictive control algorithm, the algorithm achieves common-mode voltage suppression and neutral-point potential balance control at the same time, design of weight items is omitted, the harmonic content of output current is reduced, the problem of current distortion in the transient process that balance is controlled after neutral-point potential pulling deviation is solved, and the algorithm has the advantages of being simple and high in applicability.

The invention relates to a three-level SHEPWM method of inhibiting common mode voltages, comprising the steps of: calculating a switching angle, and drafting a three phase output oscillogram; regarding SHEPWM three phase output as a space vector set consistent with SVPWM, and respectively calculating common mode voltages corresponding to a large vector, a middle vector, a positive small vector, a negative small vector and a zero vector; according to three phase voltage output waveforms, calculating an output vector change and effect section of a period within 360 DEG; determining the type of a three phase output vector at a current time; when the type of the three phase output vector is a positive small vector, switching a three phase switching state into a same position negative small vector which is paired with the positive small vector; and when the type of the three phase output vector belongs to the other four types, a three phase SHEPWM switching state is outputted normally. The method can maintain midpoint voltage self-balance characteristics and effectively reduce inverter output common mode voltages under the condition of not eliminating line voltage specific harmonic waves.

The invention discloses a novel PWM inverter topology structure which is a novel PWM inverter topology structure with the introduction of an LC filter. The LC filter is introduced at an output end ofan inverter, and a new sinusoidal pulse width modulation (NSPWM) strategy is used to carry out modulation. According to the pulse width modulation strategy, zero vector synthesis is not used, but adjacent 3 space vectors are selected for synthesis. According to the principle of volt-second balance, a PWM waveform in a period is sampled individually, and then an obtained turn-on or turn-off time and a triangular wave are compared to obtain a turn-on signal of each phase IGBT. According to the novel PWM inverter topology structure of the invention, the NSPWM strategy is used to effectively inhibit common mode voltage, the higher harmonics of phase voltage can be filtered out by introducing the LC filter, thus the harmonic components of differential mode voltage are eliminated, phase voltageand line voltage of a purer sine wave are obtained, and the common mode voltage is greatly suppressed.

the invention provides a spatial vector modulation method of an indirect matrix converter. The method comprises the following steps of determining a first duty cycle of a zero vector of an inversion stage, selecting a plurality of turning periods in a modulation period, wherein the total time length of the plurality of turning periods is the product of the first duty ratio and the modulation period, taking the starting time of each turning period as the modulation time for the switching states of the rectifying stage and the inversion stage in each turning period, adjusting all the switches ofthe rectifying stage to be disconnected at the starting moment of each turning period, remaining all the switching states of the inversion stage unchanged; namely, disconnecting all the switches of the rectification stage to realize the introduction of a zero vector into the inversion stage, in the modulation process of the indirect matrix converter in a time period when a zero vector originallyneeds to be led into to the inversion stage. The switch state at the initial moments of the time periods at the inversion stage does not need to be adjusted, so that the frequency of the action of theswitch of the inversion stage is reduced on the basis of reducing the common mode current. The loss of the system is reduced.

The invention relates to an alternating current and direct current power supply system with a grounded power supply end. In the scheme, the input end of a power electronic transformer is connected with a medium-high voltage power grid, and the output end of the power electronic transformer is connected with a low-voltage direct current bus; the input end of a low-voltage inverter DC/AC device is connected with the low-voltage direct-current bus, and the output end of the low-voltage inverter DC/AC device is connected with a low-voltage alternating-current load and grounded; and the input endsof non-isolated DC/DC devices are connected to the low-voltage direct-current bus in parallel, and the output ends of the non-isolated DC/DC devices are connected with a low-voltage direct-current load. According to the scheme, a three-phase four-wire or three-phase five-wire power supply mode is established at the alternating current and direct current power supply side, and the problem that a grounding wire system is lacked when a three-phase three-wire inverter supplies power is solved. In addition, a star connection capacitor is additionally arranged on the output side of the low-voltage inverter DC/AC device and is connected with the input sides of the non-isolated DC/DC devices to construct a low-impedance loop of a common-mode voltage, so that the common-mode voltage of the alternating current side to the direct current side can be effectively inhibited, and the problem that the power supply process is interfered due to overlarge common-mode voltage of the non-isolated alternating current/direct current power supply circuit is solved.

The invention discloses a PCB dielectric slice selection method, device and system, and the method comprises the steps: determining a first distance between two pieces of adjacent glass fiber cloth in PCB dielectric slices of various specifications, and then determining a combination of a second distance between two lines of a to-be-set differential line, the impedance of which is preset impedance; subsequently determining the target PCB dielectric sheet from the PCB dielectric sheets satisfying the second distance = N * first distance according to the setting direction of the differential line to be set on the PCB, so that the second distance = N * first distance, the impedance of the PCB dielectric sheets through which the two lines of the differential line pass is the same. Therefore, the two lines generate the same signal delay, the difference Skew influence caused by the glass fiber effect is avoided, the common-mode voltage is inhibited, the system crosstalk and EMI interference are reduced, the signal eye pattern quality is improved, in addition, the cost is low, the utilization rate of the plate is ensured, and the reliability is high.