281 results about "Harmonic elimination" patented technology

Three-level inverter and rectifier power conversion systems and space vector modulation (SVM) controls having even-order harmonic elimination for neutral voltage balancing with a predefined vector switching sequences for half-wave symmetry in open loop system operation. The vector sequence listings for each SVM diagram segment includes switching state entries individually indicating one of three possible switching state levels positive (P), zero (0), or negative (N) for each of three or more switching groups of the power conversion system, with listings for each pair of first and second diametrically opposite diagram segments include symmetrically opposite switching states, with positive levels in the entries of the listing for the first segment corresponding to negative levels in the entries of the listing for the second segment and vice versa.

A method of designing a random pulse width modulation (RPWM) inverter with unwanted harmonic elimination, which first uses a Fourier analysis and a numerical analysis to eliminate the unwanted harmonic components, next uses the equal area approach to produce switching angles to be used as start values for solving non-linear equations, next selects low-order harmonics to be eliminated and randomly sampled harmonics to solve the equations and obtain pluralities of switching angles for eliminating different harmonics, next applies pluralities of harmonics to a random probability function to thereby obtain a harmonic distribution, and finally uses a random sampling to evenly disperse the higher side-band harmonic components and effectively suppress the low-order harmonic components.

The present invention discloses a long and thin bore diameter and cylindricity measurement method based on dual-sensor error separation. A standard ring gauge is taken as a calibrating device to sleeve a dual-sensor measuring head, a first harmonic elimination approach method is employed to calibrate the dual-sensor measuring head, the dual-sensor measuring head is sleeved with the bore of a measured workpiece, the complete cycle scanning measurement is performed section by section along the axial direction and the circumferential direction of the bore, the distance measurement data of each section of the two sensors are employed to obtain average values and perform difference to realize calculation and separation of line feed errors of each section and the eccentricity error of each section is separated to convert the finally processed measurement data to a rectangular coordinate system and add the eccentricity error of the corresponding section in the data points of each section so as to restore the contour of the measured bore, the least square method is employed to obtain the diameter of the bore contour, and the cylindricity evaluation method is employed to perform cylindricity calculation. The long and thin bore diameter and cylindricity measurement method based on the dual-sensor error separation can realize calibration of an unidirectional electronic measurement head so as to effectively separate the line feed errors of a guide rail and the eccentricity error of each section of the bore of the workpiece so as to greatly improve the detection precision of the long and thin bore diameter and the cylindricity.

The invention discloses a micro-grid voltage disturbance control method with voltage harmonic compensation, and belongs to the field of electrical technology. According to the invention, droop control, proportional resonance control and harmonic compensation control are mainly employed for a plurality of inverters in parallel connection. When a micro-grid voltage fluctuates, reactive power is uniformly divided through droop control, and a disturbance voltage is adjusted. Also, the high-order harmonic wave of the micro-grid voltage can be extracted through detection, the first-order elimination is carried out through proportional resonance control, and then the second-order elimination is carried out through the harmonic compensation control. Finally, the above results are outputted in a voltage mode through a PWM control inverter. The method can effectively improve the operation characteristics of an intermittent and unstable power supply in real time, also can adjust the voltage disturbance and the harmonic voltage, achieves the effects of voltage stabilization and voltage harmonic elimination, improves the capability of micro-grid regulation and control, improves the stability and reliability of the micro-grid operation, and improves the grid-connected capability of a micro-grid.

The invention relates to a five-level ANPC (Active Neutral-Point-Clamped) converter, particularly to a suspended capacitor voltage control method of the five-level ANPC converter. The suspended capacitor voltage control method comprises the following steps of applying SHEPWM (Selective Harmonic Elimination Pulse Width Modulation) pulse waves to the five-level ANPC converter; performing real-time detection on a suspended capacitor voltage value of the five-level ANPC converter, performing comparison on the suspended capacitor voltage value and a reference value of the suspended capacitor voltage and determining whether a suspended capacitor needs to be charged or discharged; detecting whether the load current of the five-level ANPC converter is positive or negative and selecting the redundancy switch state which is suitable for the ANPC converter according to the positive or negative load current of the five-level ANPC converter and the determined charging and discharging state required by the suspended capacitor; performing charging and discharging on the suspended capacitor of the five-level ANPC converter through the selected switch state until that the variable quantity of the suspended capacitor voltage is zero within a sampling period and performing repeated detection on the suspended capacitor voltage value. According to the suspended capacitor voltage control method of the five-level ANPC converter, the appropriate redundancy switch state is selected according to the direction of the load current and the size of the suspended capacitor voltage so as to enable the suspended capacitor voltage to be fluctuated within a small range.

The invention relates to a single-phase earth fault line selection method of a 10kV power distribution network earthing system. When the ratio between the inductance impedance value of an arc suppression coil and the impedance value of a harmonic elimination resistor is within some ratio range, and a single-phase earth fault occurs in the 10kV power distribution network earthing system, the difference between the zero-sequence voltage and the zero-sequence current of a fault outgoing line will be smaller than a preset value, and a protection device outputs a fault indication signal and an outgoing line switch actuating signal when the conditions are satisfied. The single-phase earth fault line selection method of the 10kV power distribution network earthing system has the advantages that parameter characteristic values on an arc suppression coil loop of the10kV power distribution network earthing system are adopted to be combined with the zero-sequence voltage and the zero-sequence current of the 10kV power distribution network earthing system, the changes of a phase angle cannot be easily influenced by factors such as operation conditions of the10kV power distribution network earthing system, criterion output is stable, and accuracy of judgment is high. The single-phase earth fault line selection method of the 10kV power distribution network earthing system can rapidly achieve fault location, can greatly improve the degree of automation of a power distribution network, can greatly reduce the time of a blackout of a user, reduces loss caused by the blackout, overcomes the defects existing in a small-current earthing operation mode, and has good social benefit and economic benefit.

The invention discloses a specific harmonic eliminating optimum method of three-level single-phase bridge inverter, which is characterized by the following: calculating the harmonic eliminating angle of single-phase bridge left and right bridge arms; eliminating more high order harmonic wave; reaching less harmonic wave distortion rate of inverter output voltage; improving harmonic wave property of output voltage effectively.

The invention discloses an active power filter (APF) and thyristor switched filter (TSF) hybrid compensation device for an electric rig, which comprises a passive part, an active part, an electric quantity data acquisition module of a well site and the compensation device, a control module of a TST, and a control module of an APF. The filtering characteristics of the TSF are improved by utilizing the APF, so that when the TSF works in a combined manner, 2 to 10 times of harmonic currents injected into a power supply system of the well site are controlled within a given value, and the harmonic currents of the well site are prevented from being amplified when different filtering branches of the TSF are switched in a combined manner; and by adopting the structure that the APF is connected in parallel with a fundamental resonance module of a fifth filtering branch of the TSF through a coupling transformer, the capacity of the APF is very small, so that the APF is beneficially controlled, the cost of the whole set of device is reduced, the problem of overlarge harmonic currents occurring when the TSF is switched in a combined manner is effectively solved, and then the tasks of reactive compensation and harmonic elimination of the well site can be completed more safely and more effectively.

The invention relates to a method for realizing selective harmonic elimination modulation by adopting a fixed control cycle. The method is technically characterized by comprising the following steps of adopting the fixed control cycle to control the vector decoupling of a PWM (pulse width modulation) rectifier, so as to obtain the amplitude and the angle of the given voltage, and deriving the angle of the given voltage to obtain the frequency of the given voltage; using the angle of the given voltage as an initial value, and carrying out number integration on the frequency, to obtain a relatively continuous angle; carrying out monotone processing on the relatively continuous angle; according to the monotone-processed continuous angle and the received amplitude, searching a table to output the SHEPWM (selective harmonic elimination pulse width modulation) pulse. The method has the advantages that the vector closed loop control method of the fixed cycle is combined with the selective harmonic elimination modulation, so the complicated variable cycle control is avoided, a power converter system has the quick and accurate dynamic response capability and good current harmonic property in the steady state, the low-order harmonics in the output voltage of a converter can be obviously inhibited, and the method is especially suitable for high-power application occasions.

The invention provides a one-phase open-circuit fault-tolerant control method for a six-phase permanent magnet synchronous motor, and relates to the technical field of multi-phase motor control. The method comprises: aiming at fault tolerance research after one-phase open circuit of the six-phase permanent magnet synchronous motor with the phase displacement of 30 degrees, using a neutral point isolation mode, considering the influence of fifth harmonic waves, providing a six-phase static coordinate transformation matrix corrected after a fault is established, and establishing a voltage and torque mathematical model under fundamental waves according to the matrix and a rotating coordinate transformation matrix; under the condition that a no-load air-gap magnetic field is not sinusoidal, deriving a mathematical model of a quintuple harmonic space, analyzing the coupling relation of d-q subspaces in a voltage equation transformed by a rotation transformation array, and providing a secondary rotation coordinate transformation array and a voltage compensation formula for eliminating d-q axis voltage coupling after decoupling. In consideration of the influence of the quintuple harmonicflux linkage and inductance on the voltage and torque of the six-phase permanent magnet synchronous motor in a fault-tolerant mode, torque pulsation containing four times of angular frequency and sixtimes of angular frequency is eliminated by injecting quintuple harmonic.

The invention discloses a selective harmonic elimination pulse width modulation control method of eliminating dead zone effect and a device thereof, which are used for a neutral point clamped NPC multi-level converter. The selective harmonic elimination pulse width modulation control method comprises steps that the current voltage closed-loop control of the NPC multi-level converter is carried out, and a voltage modulation ratio and a real-time phase are calculated in a real-time manner; a preset switching angle storage table is queried according to the voltage modulation ratio, and a standard switching angle corresponding to the voltage modulation ratio is acquired; the standard switching angle is modified according to the output current direction, the delayed- conduction arc value, and the early-shut off arc value of the NPC multi-level converter, and the dead zone effect of the standard switching angle is eliminated, and then the modified standard switching angle is acquired; based on the modified standard switching angle, an angle interval, in which is disposed the real-time phase, is determined, and a driving pulse having a dead zone corresponding to a real-time angle is acquired according to the angle interval and a preset corresponding relation table, and then the NPC multi-level converter is driven. The influences of the dead zone effect on the driving pulse of the converter are eliminated, and the harmonic level of the converter is optimized.

A reactive power compensation system for compensating reactive power requirements in an electrical power system. The reactive power compensation system includes a static synchronous compensation unit, a current harmonics elimination unit, and a compensation control unit. The static synchronous compensation unit includes a plurality of static synchronous compensation modules for compensating reactive power in the electrical power system. The current harmonics elimination unit includes a plurality of active filter modules for eliminating current harmonics generated in the electrical power system. The compensation control unit implements a sequential control mechanism for regulating the operation of the static synchronous compensation modules and the active filter modules.

The invention provides a switched capacitor N-level inverter and a modulation method thereof. The inverter comprises a single DC input power supply, a switched capacitor unit and a full bridge unit. The switched capacitor unit is connected in parallel with the single DC input power supply and used for performing series-parallel conversion between the single DC input power supply and the capacitorsof the switched capacitor unit and outputting a multi-step voltage. The full bridge unit is connected in parallel with the switched capacitor unit, and is used for outputting the multi-step voltage output by the switched capacitor unit after positive-negative polarity conversion. The modulation strategy adopted is a step wave specific harmonic elimination modulation mode based on the combinationof specific harmonic elimination and step wave modulation. The inverter of the invention can output any level by expanding the modular structure of the switched capacitor sub-modules, and the number of power devices of the inverter is greatly reduced through a simpler modular structure.

The invention relates to a fast switching arc and harmonic elimination-based single-phase grounding fault line selection and location method and belongs to the circuit protection technical field. According to the fast switching arc and harmonic elimination-based single-phase grounding fault line selection and location method, when grounding occurs, zero sequence voltage triggers a line selection device to enter a collection state to collect zero-sequence current in each loop, and the zero-sequence current in each loop is processed, and first-stage zero-sequence current data of each loop is extracted; if arc light grounding occurs, an arc elimination device forcedly converts the arc light grounding into metal grounding, and the line selection device enters the collection state again to collect the zero-sequence current in each loop, so that second-stage zero-sequence current data can be obtained; corresponding first-stage zero-sequence current data are subtracted from the second-stage zero-sequence current data of each loop, so that incremental values can be obtained, and a line with the largest increment is a fault line; and one or more positioning methods are combined together to carry out fault interval positioning. The fast switching arc and harmonic elimination-based single-phase grounding fault line selection and location method of the invention is not affected by factors such as the magnitude of grounding resistance and the distance of a short-circuit point, and can select a fault line within 3ms after a grounding fault occurs. The method is stable and reliable and has high precision.

The invention discloses a repetitive controller, which comprises an internal model part, a cycle delay module, a compensation module and a frequency-specific gating module, wherein the input quantity of the repetitive controller is input from the input end of the internal model part; the internal model part, the cycle delay module and the compensation module are connected in series with one another; and the frequency-specific gating module is connected in series with the internal model part, the cycle delay module and the compensation module or is arranged on a forward channel of the internal model part. In the repetitive controller, the frequency-specific gating module is arranged, so that only a selected frequency-specific harmonic wave can be filtered out of an error signal, and the repetitive controller can perform harmonic elimination on the frequency-specific harmonic wave.