96 results about "Over modulation" patented technology

Disclosed is a high-speed control method for a permanent magnet synchronous motor-compressor system, including the following steps: initial design is carried out; a motor is detected through DSP, including detecting the two-phase current of the stator of the motor, the voltage Udc of a DC generatrix; the voltage of a d-p shaft is calculated; faults of overcurrent, overpressure and undervoltage are detected; if any fault exists, the PWM pulse signals are blocked and then the control program is paused; if no fault exists, the following steps will be carried out; the rotating speed of the motor and the position of the rotor are identified in the process of speed-position estimation; the current and the voltage of the reference d-q shaft of the motor are calculated; switching signals of an inverter are acquired through haplotype over-modulation; the data are recorded and waveforms are displayed; judgment of whether to pause the control program is carried out; if not, the second step is carried out again; if yes, the control program will be paused. The control method applies haplotype over-modulation method into the permanent magnet synchronous motor-compressor system, realizing sensorless over-modulation to the synchronous motor-compressor vector control system.

The invention provides an AC side fault ride-through control method for a hybrid multi-terminal DC transmission system. The method comprises the steps: configuring the maximum DC voltage control for a rectification station LLC on the basis that the rectification station LCC employs constant direct current control, an inversion station MMC selects constant DC voltage control, and other inversion stations MMCs select constant direct current control; and configuring low-voltage current-limiting control for all inversion stations MMCs selecting the constant direct current control. The beneficial effects of the invention are that the rectification station and all inversion stations respectively carry out the corresponding operation (distributed control) for an AC side fault of any convertor station of a hybrid DC power transmission system, so as to coordinate the power distribution among stations; the DC voltage and current are controlled to be stable; and there is no DC overvoltage and low-voltage over-modulation risk. The method does not need quick inter-station communication for processing the AC fault, is simple in structure of a controller, is convenient for the setting of parameters, and is convenient for engineering application.

A method and apparatus are provided for supporting the transmission of communications data in a satellite communications network 10 between user terminals 15–18 and a ground station 14 via a satellite 12. At least one carrier signal is generated in a beam spot and conveys communications data over at least one downlink 22–25 to the user terminals 15–18. The carrier signal is modulated simultaneously with independent communications data streams EDP15 and EDP 18 over modulation channels 802 and 804, respectively, of a multi-dimensional modulator 400. By passing independent data streams over each dimension of an n-dimension modulation technique, different encoding schemes may be assigned to user terminals 15–18 based upon the strength of the signal received by the user terminal 15–18.

The invention discloses a control method of a PID controller by combining multiple control algorithms. The existing PID control method has the following defects: as for integral, integral accumulation, which causes PID operation, results in integral saturation, causing great over modulation of the system; and as for differential, differential is especially sensitive to interference, and frequent fluctuations of the given value can result in system oscillation. The invention is characterized by comprising the following steps: carrying out scale operation on the amount of deviation to obtain the output value of a proportional part; carrying out variable speed integral operation on the amount of deviation, and then carrying out trapezoidal integral operation to obtain the output value of an integral part; carrying out incomplete differential operation on the amount of deviation to obtain the output value of a differential part, thereby obtaining the output value of PID; carrying out output amplitude limiting operation; and finally, carrying out output rate limiting operation. On the premise of maintaining integral, eliminating static error of and enhancing precision, the invention reduces the over modulation amount; and the invention eliminates the external interference to some extent and eliminates oscillation caused by frequent motions.

The invention provides a method and a system for over-modulating three-level space vectors. The method comprises the following steps: calculating the modulation ratio and angle of a reference voltage; dividing the modulation ratio into a first setting interval and a second setting interval; positioning the modulation ratio in the first setting interval and calculating the duty cycle of a short vector, a long vector and a medium vector by intervals according to the angle of the reference voltage; correcting the duty cycle of the short vector, the long vector and the medium vector respectively according to the magnitude of the short-vector duty cycle; calculating the N-action duty cycle and the P-action duty cycle of each phase according to the corrected duty cycle; positioning the modulation ratio in the second setting interval and calculating the keeping angle of the reference voltage; calculating the N-action duty cycle and the P-action duty cycle of each phase by intervals according to the resulting of comparing the keeping angle with the angle of the reference voltage; and conversing the N-action duty cycle and the P-action duty cycle of each phase into action time and mapping the action time back to the prior sector. The method and the system have the advantage of ensuring that SVPWM over-modulation is simple in calculation steps and higher in modulation precision.

An interface between a network component and an optical fiber section communicates with a remote interface and a remote network component at an opposite end of the optical fiber section through over-modulation of optical signals sent between the interfaces and network components. The over-modulation is at frequencies much lower than the ordinary modulation of the optical signals. The over-modulation allows communication between the interfaces for performing management, testing and maintenance operations and permits superior detection of faults in the optical fiber section.

The invention discloses a two-level three-phase space vector pulse-width modulation device and an SVPWM optimization method thereof. Aiming at influence of dead-zone time and narrow pulse-width limit, a practical linear modulation zone is expanded, an over-modulation algorithm is optimized and linear processing of an over-modulation zone is simply realized. The two-level three-phase space vector pulse-width modulation device comprises six modules of a given reference voltage correction module, a voltage coordinate transformation module, a voltage interval calculating module, a vector time calculating module, a modulation algorithm optimization module and a PWM comparison point time calculating module. Bus voltage is fully utilized via the simplest algorithm so that linearity of output fundamental wave voltage is enhanced and total harmonic wave distortion of the output voltage is reduced.

This invention discloses a super-resolution microscopy method and device, of which the method comprises the following steps: converting laser beam into linearly polarized light after collimation; linearly polarized light is deflected and phase modulated by a spatial light modulator; the deflected beam is focused, collimated and then converted into circularly polarized light for projection on the sample to collect signal light from various scanning points on the sample, and obtaining the first signal light intensity; switching over modulation function to project linearly polarized light modulated by the second phase modulation on the sample to collect signal light from various scanning points on the sample, and obtaining the second signal light intensity; calculating valid signal light intensity to obtain the super-resolution image. This device features in a simple structure and easy operation, which can obtain a super-resolution beyond diffraction limit at a lower luminous power; it is quick in image formation with the frame frequency over 15 frames when the number of scanning points in each image is 512×512 .

The invention discloses a feed-forward voltage compensation-based direct-current side oscillation suppression method for a metro traction converter. Proper damping parameters are selected according toa stability criterion condition. Meanwhile, based on the principle that the ratio of effective vectors is maximum and the disturbance is minimum, a feed-forward voltage compensation parameter of a dqshaft is calculated. According to the principles of equal effective action vectors and power conservation, a reference voltage vector after the amplitude-limiting adjustment is obtained through calculation. As a result, the direct-current side stability control of a metro traction transmission system under the compensation over-modulation condition is ensured. According to the invention, the dynamic compensation for the feed-forward voltage is adopted, and the oscillation of the direct-current side voltage and the direct-current side current during the operation process of the traction transmission system is suppressed. The stability of the voltage at the direct-current network side is ensured. Meanwhile, the over-modulation condition caused by voltage compensation is considered, so thatthe effectiveness of the oscillation suppression method under the over-modulation condition is ensured. The condition that existing reference current compensation schemes are easily limited by currentloop bandwidth is avoided, so that the faster dynamic response is achieved.

The invention provides a current detecting method capable of stably operating even in an over-modulation area, an inverter device and a convertor device using the same. In a motor driving device having an alternated current motor, a current detecting unit for detecting the bus bar current or each branch current at the direct current side of the inverter and the convertor for driving the alternated current motor, and a control unit for controlling the alternated current motor by using a current detected value acquired from detection, a current reference value of the alternated current motor is calculated by using a past detected value of the current acquired from the current detecting unit or a current instruction value of the control unit, the error between a one phase current detected value and the current reference value is calculated when only the one phase current of the alternated current motor can be detected by the current detecting unit, and the current at other phases of the alternated current motor can be presumed by using the error.

The invention discloses an inter-phase voltage-sharing control method for a DC bus of a cascaded star-connected static synchronous compensator (STATCOM). The voltage-sharing control method comprises the following steps of regulating a d-axis component of a modulation wave output from a current ring according to the deviation between DC voltages of a phase A and a phase B and a reference value; converting dq-abc conversion on the modulation, wherein a negative-sequence component is overlaid with the modulation wave, so that the output of the STATCOM generates the negative-sequence voltage. The negative-sequence voltage is used for generating a negative-sequence current, the negative-sequence voltage, the negative-sequence current, positive-sequence current and positive-sequence voltage are separately used for changing allocation of three-phase power flow, and the balance among three phase DC voltages is achieved. In the voltage-sharing method proposed by the invention, a mode of overlaying the negative-sequence modulation wave is simple and is easy to implement, the stability of the current ring is not affected, meanwhile, the introduced modulation wave zero-sequence component is also removed, over-modulation caused by the zero-sequence component is avoided, and the reliability of STATCOM running is improved.

The invention discloses a SVPWM (Space Vector Pulse Width Modulation) method which comprises the following steps of: confirming an angle theta 0 corresponding to each PWM (Pulse Width Modulation) period within a single period of a fundamental wave according to a carrier-to-noise ratio; calculating a present angle theta n according to the theta 0; obtaining an amplitude value of a three-phase output at the present by a quantified SPWM (Sinusoidal Pulse Width Modulation) wave; injecting a higher harmonic on the basis of the quantified SPWM wave to enable the shape of the outputted SVPWM waveforms with different frequencies to be consistent with the shape of the waveform obtained according to a traditional SVPWM method and realize an over-modulation function; and meanwhile, setting the frequency, thereby enabling the flux linkage rotation of the space vector to be more approximate to a circular magnetic field. According to the SVPWM method provided by the invention, the dependence on mechanical parameters of system is weakened, the operation volume is reduced, the harmonic influence is reduced, the robustness of the system is enhanced, and the generality and timeliness are higher.

A control device 1 for an electric motor of the present invention includes: a current control unit 4 configured to calculate voltage command values v_d*, v_q* used to drive an electric motor 100, on the basis of a state quantity for voltage command value calculation and q and d-axis current detection values i_d, i_q, the state quantity calculated from a torque command value T*; and an over-modulation processing unit 16 configured to determine whether the electric motor 100 is stable or unstable in an over-modulation state, on the basis of the voltage command values v_d*, v_q*, current control constants, and electric motor constants, and to drive the electric motor 100 in the over-modulation state when determining that the electric motor 100 is stable.

The invention provides a method and device for suppressing difference of capacitor voltage fluctuation of a hybrid MMC sub-module. The method includes the steps: when a hybrid modular multilevel converter is running in a steady state through over-modulation, determining the third harmonic voltage correction according to the operating state of the system, then determining the circulating current suppression voltage correction, and finally determining the modulation wave voltage of the hybrid modular multilevel converter. The method and device for suppressing difference of capacitor voltage fluctuation of a hybrid MMC sub-module can suppress the difference of the capacitor voltage fluctuation of a full-bridge sub-module and a half-bridge sub-module of the hybrid modular multi-level converter, and at the same time, can reduce the fluctuation level of the capacitor voltage of the whole converter, and the light weight effect is obvious, and the hybrid modular multilevel converter can be running stably. The technical solution provided by the method and device for suppressing difference of capacitor voltage fluctuation of a hybrid MMC sub-module introduces the third harmonic voltage injection rate, and can effectively suppress the capacitor voltage fluctuation of the full-bridge sub-module and the half-bridge sub-module of the hybrid modular multi-level converter on the premise of maintaining the voltage of the DC bus and the transmission power unchangeable, and can reduce the sub-module capacitor voltage ripple level of the overall converter.

The invention discloses a PWM method for an electric vehicle motor inverter. The method comprises the steps of performing PWM on the inverter by an NZPWM method, and reasonably arranging a reference voltage vector synthesis sequence and a PWM pulse action mode of each section; correcting a three-phase modulation wave generated by NZPWM to obtain an inverter boundary modulation ratio parameter, andrespectively executing NZPWM and SVPWM according to the modulation ratio parameter; performing over-modulation on the inverter by a discrete PWM method after a voltage vector enters an over-modulation region from a linear modulation region, dividing the over-modulation region into two regions, and setting a modulation ratio of lower boundaries of the two regions; and executing discrete PWM of thetwo over-modulation regions according to the modulation ratio to obtain an expected PWM waveform. By the method, the common-mode voltage output amplitude at zero vector is effectively reduced, motorshaft current amplitude is suppressed, the service lifetime of a motor bearing is prolonged, the vibration and the noise output of a motor inversion system are reduced, and the driving quality of thewhole vehicle is improved.

The invention relates to a method for optimizing the dynamic property of an optical fiber gyro, which comprises sequentially connected forward path links: sagnac effect, photoelectric conversion, filtering amplification, AD conversion, cosine response bias modulation and demodulation, first field integral digital storage and digital interception, and sequentially connected backward links: second order integral, D/A conversion power amplification, power amplification, phase modulation and coil delaying. The treatment procedure comprises the following steps: establishing a simplified gyro closed-loop model; establishing a precise gyro closed-loop model; determining gyro stabilization and over modulation conditions; and selecting closed-loop parameters for the optical fibre gyro, and predicting gyro dynamic property through simulation. The method of the invention is reasonable in design, can realize zero bias effect prediction of the gyro during vibration, provides reference for optimizing gyro closed-loop parameters, and improves the dynamic property of the optical fiber gyro.

The invention provides a wind power converter high voltage ride-through control method and device. The control method comprises steps: a positive-sequence voltage D-axis component/phase voltage effective value of the power grid side of the converter is acquired; if the positive-sequence voltage D-axis component/phase voltage effective value is larger than a preset ride-through starting voltage value, the converter is determined to enter a high voltage ride-through mode; and according to a preset over modulation control strategy, a floating DC bus voltage control strategy and/or a reactive priority control strategy, the converter is controlled to ensure the converter to operate stably. According to the wind power converter high voltage ride-through control method and the control device provided in the invention, the wind power converter can operate stably in a high voltage operation range, the stability of the power grid is improved, large-scale wind power grid disconnection caused by voltage disturbance or failure is prevented, the working stability of each component in a wind turbine can be improved at the same time, and the practicability of the control method is improved.

The invention relates to the field of pulse width modulation, and discloses a voltage space vector pulse width modulation method. The method comprises the following steps of: 1, giving a reference voltage vector Ur, and decomposing the given reference voltage vector into synthesis of two voltages on axes alpha and beta; 2, converting the Ualpha and Ubeta into a three-phase voltage; and 3, according to Umin=Min(Ua, Ub, Uc), Ua'=Ua-Umin, Ub'=Ub-Umin, Uc'=Uc-Umin and U*max=Max(Ua', Ub', Uc', Vdc), obtaining the switching time Ta', Tb' and Tc' of the three-phase voltage: Ta'=Ua'/U*max, Tb'=Ub'/U*max and Tc'=Uc'/U*max. Because multiple times of calculation of trigonometric functions is not needed and the over-modulation area does not need to be judged, the method is simple and convenient to implement, low in calculation frequency and convenient to realize a digital mode, and can be applied to all three-phase inverter systems.

The invention provides a high power factor diode rectifier permanent magnet motor control method adopting a low capacity thin film capacitor. According to the method, a d-q axis specified is obtained via optimization algorithm-based off line calculation, and a PWM prediction controller is adopted for replacing a PI current controller based on conventional vector control. To compensate deviation between expected inverter output power and output power calculated based on a real time motor current and specific voltage, a voltage correction vector is added. A novel over-modulation algorithm is adopted; while voltage outputting capability of an inverter is increased, the specific voltage of a corrected inverter is enabled to be always in an inverter output voltage limiting scope. According to the control method, application of grid side high power factor control does not require any extra power factor correction circuit or input wave filter, and an input current harmonic wave component of a power grid can be suppressed. Compared with a conventional motor driver, a motor driving control solution put forward in the invention is markedly advantageous in terms of cost, size and reliability.

The invention discloses a reactive power compensation control method for an open-winding dual-inverter photovoltaic power generation system. Two groups of photovoltaic arrays in an open-winding dual-inverter photovoltaic power generation system can be controlled by independent MPPT to improve a solar energy utilization rate. However, if affected by shielding or component damage, the two groups ofphotovoltaic arrays may have a great difference in maximum output power, which may cause an over-modulation problem and thus result in poor grid-connected current performance and even system instability. In view of the over-modulation problem of the two groups of photovoltaic arrays, which have a great difference in maximum output power, of the open-winding dual-inverter photovoltaic power generation system, the invention provides a simple and easy-to-implement reactive power compensation control method. The reactive power compensation control method can effectively avoid the over-modulation problems, broadens the maximum power point operating range of the two groups of photovoltaic arrays in the open-winding dual-inverter photovoltaic power generation system, and improves the power generation efficiency of the photovoltaic system.

Digital values representing an audio signal are formed in a FM transmitter. The deviation of the amplitude of the audio signal as represented by the digital values, from a reference amplitude level, is measured. The audio signal is filtered based on the deviation measured by processing the digital values, with the filtering designed to filter different frequency components of the audio signal with different respective magnitudes. Another set of digital values representing the filtered audio signal is generated, and used to frequency modulate a carrier signal to generate a FM signal. Over-modulation of the FM signal is thereby controlled.

Power conversion systems and methods are provided for operating a multi-phase inverter to drive a load while mitigating reflected waves, in which one or more PWM modulating signals are selectively adjusted if at least one of the phase signals or values is transitioning into or out of an over-modulation range outside a pulse width modulation carrier waveform range.