228 results about "Voltage distortion" patented technology

Methods and systems for controlling a power inverter in an electric drive system of an automobile are provided. A signal controlling the power inverter is modified utilizing a first voltage distortion compensation method if a modulation index of the signal is less than a first modulation index value. The signal is modified utilizing a second voltage distortion compensation method if the modulation index is at least equal to the first modulation index value.

Disclosed is a dead-time compensation method of a 3-phase inverter using an SVPWM scheme. The dead-time compensation method includes generating a switching signal having dead-time with respect to the power semiconductor switches of the upper and lower arms in order to obtain a predetermined output through the SVPWM scheme, detecting medium phase current from each phase current output through the switching signal, determining polarity of the medium phase current, and generating a switching signal by calculating switching time in order to compensate for time to apply effective voltage according to the polarity of the medium phase current. Through the dead-time compensation method, the distortion of the output voltage and the reduction of voltage having a fundamental wave in the output voltage, which are caused by the dead-time, are minimized through the switching of compensating for the time to apply effective voltage based on the polarity of the load current.

The invention discloses an inverter parallel harmonic wave ring current restraining method for controlling harmonic wave droop. The method comprises a harmonic wave droop control, a power droop control and a voltage control. During the harmonic wave droop control, feature subharmonic power is detected through a rapid Fourier FFT (fast fourier transform algorithm) commutation fractional frequency, according to a harmonic wave droop feature, and a feature subharmonic reference voltage output by an inverter is calculated; and during the power droop control, the fundamental wave reference voltage is calculated, the feature subharmonic reference voltage and the fundamental wave reference voltage are combined into the reference voltage output by the inverter, the output voltage distortion of the inverter is effectively reduced, the inter-harmonic ring current of the inverter is controlled, and the power accurate allocation is realized. The inverter parallel harmonic wave ring current restraining method provided by the invention can be used for solving the problems that when a large number of non-linear loads are switched on the parallel system, the voltage distortion of a system is serious, a harmonic wave ring current is magnified and the like, the inverter parallel harmonic wave ring current restraining method is effectively applied to an industry special power supply, a UPS (uninterrupted power supply) and a distributed energy system.

A power conversion apparatus, such as a UPS, includes a first waveform reference signal generator circuit operative to generate a first waveform reference signal responsive to an AC bus, and a second waveform reference signal generator circuit operative to generate a second waveform reference signal, e.g., a more consistently sinusoidal signal produced by another source. The apparatus further includes a control circuit that selectively generates a third waveform reference signal from the first and second waveform reference signals, and a power converter circuit (e.g., a rectifier and / or inverter) coupled to the AC bus and operative to transfer power to and / or from the AC bus responsive to the third waveform reference signal. In particular, the control circuit may be operative to weightedly combine the first and second waveform reference signals to generate the third waveform reference signal. The control circuit may weightedly combine the first and second waveform reference signals responsive to an operating parameter of the power converter, such as a voltage, a current, a power factor, a source impedance, a voltage distortion and / or a harmonic input current.

The invention relates to a precise phase locking method based on a cross decoupling self-adaptive complex filter, which comprises the following steps: firstly carrying out the Clarke coordinate transformation on three-phase voltage input signals of Ua, Ub and Uc for obtaining voltage signals of Ualpha and Ubeta under an alpha-beta coordinate system; then leading the voltage signals to pass throughthe cross decoupling self-adaptive complex filter for extracting positive sequence voltage components *alpha<plus> and *beta<plus> under the alpha-beta coordinate system; further carrying out the Clarke inverse transformation on the *alpha<plus> and the *beta<plus> for obtaining three-phase voltage positive sequence components of *a<plus>, *b<plus> and *c<plus> under an a-b-c coordinate system; carrying out the Park transformation on the *alpha<plus> and the *beta<plus> for obtaining a d-axis component *d<plus> and a q-axis component *q<plus> under a d-q coordinate system, wherein, the q-axiscomponent *q<plus> reflects the positive sequence amplitude; leading the d-axis component *d<plus> to pass through a PI regulator to obtaining the frequency estimated value *0; feeding the *0 back tothe cross decoupling self-adaptive complex filter for realizing the frequency self-adaption; and carrying out integration on the *0 for 1 / s for obtaining the positive sequence phase *<plus>. The precise phase locking method is characterized by simpleness, easy realization, high phase-locking precision and fast speed, thereby being particularly applicable to the precise phase locking of grid-connected converters under the extreme industrial field situations of power grid voltage distortion, three-phase voltage imbalance, large fluctuation range of voltage frequency and the like.

The invention discloses a microgrid control method having functions of voltage unbalance compensation and harmonic suppression. An integrated controller acquires a common bus voltage and calculates an unbalance factor vector, a characteristic order harmonic component positive-sequence compensation reference vector and a characteristic order harmonic component negative-sequence compensation reference vector of the common bus voltage, and transmits the vectors to a local controller of every parallel inverter through low-bandwidth communication. In the local controller, a characteristic order harmonic positive- and negative-sequence compensation voltage vector is calculated and is superposed with a reference voltage vector, a virtual impedance voltage vector and the common bus voltage unbalance factor vector to synthesize and correct a voltage regulating reference vector, and unbalance compensation and harmonic suppression of the common bus voltage is carried out through inverter voltage and current control. By applying the method provided by the invention to a multi-inverter parallel system in which a common bus is connected with a three-phase unbalanced load and a nonlinear load, three-phase voltage balance of the microgrid can be maintained, output voltage distortion of three-phase inverters can be reduced, and output power of the parallel inverters can be accurately allocated.

A power conversion apparatus is equipped with switching devices to perform power conversion of input AC power supplied from an AC power supply to output AC power having a predetermined voltage and a predetermined frequency, and to supply the power to a motor connected thereto. The apparatus includes a controller controlling switching of the switching devices, a capacitor smoothing a ripple generated by the switching of the switching devices, a current controller controlling a current flowing to the motor, and a voltage distortion corrector detecting a harmonic component caused by distortion in motor input power, and superimposing compensation values on an output of the current controller in accordance with a value of the harmonic component.

Methods and systems for driving an automobile are provided. The system includes a prime mover power source and a two-mode, compound-split, electromechanical transmission, including first and second motors, coupled to the prime mover power source, a power inverter coupled to the first and second motors, and a processor coupled to the first and second motors and the power inverter. The processor is configured to modify a signal controlling the power inverter utilizing a first voltage distortion compensation method if a modulation index of the signal is less than a first modulation index value and modify the signal utilizing a second voltage distortion compensation method if the modulation index is at least equal to the first modulation index value.

The invention discloses an inverter power transistor open circuit fault diagnosis method. The method comprises steps: an envelope function for fault line voltage of the inverter is defined firstly; output line voltage of the inverter is acquired; pretreatment is carried out on the output line voltage to acquire effective fault information; according to the effective fault information and in combination with the line voltage envelope function, voltage distortion features caused by open circuit fault are obtained; and according to the voltage distortion features, a fault bridge arm is positioned. According to the inverter power transistor open circuit fault diagnosis method disclosed by the invention, system control signals do not need to be acquired, the fault can be positioned generally in a carrier period, the diagnosis process has nothing to do with the inverter control mode and the load, the robustness is good, the diagnosis circuit structure is simple, and the method can also be used for bridge arm open circuit fault diagnosis for other three-phase inverter circuits.

The invention discloses a system and method for identifying user change relationships in low-voltage power distribution based on power-frequency voltage distortion. The method includes the following steps of: step 1, signal modulation: after a distribution transformer, a low-voltage line, an end user and two modulation demodulation devices are connected, the system is started, the user end triggers a silicon controlled rectifier around 150 degrees of a power frequency voltage cycle, and therefore, short-circuit current i can be generated between a low-voltage side phase line and a low-voltage side null line, and the magnitude of the short-circuit current i is determined by L2, R2 and the turn-on time of the silicon controlled rectifier; step 2, signal demodulation; and step 3, information exchange. The system and method of the invention are improved based on TWACS technologies. According to the system and method of the invention, a current modulation technique is utilized, and voltage distortion caused by current modulation is fitted, so that threshold values of various kinds of typical transformer areas can be automatically selected; and the number of non-distortion cycles between adjacent distortion cycles is utilized to transfer information; and therefore, the method for identifying the user change relationships in a low-voltage power distribution system can be realized. With the method of the invention adopted, effective and reliable means can be provided for electricity utilization management departments in the realization of user archive establishment, verification and the like.

The invention discloses a microgrid multi-inverter parallel operation control method adopting bus voltage compensation. An integrated controller acquires a common bus voltage and extracts a fundamental negative-sequence component, a characteristic order harmonic positive-sequence component and a characteristic order harmonic negative-sequence component of the common bus voltage, and transmits the common bus voltage components in a dq coordinate system to a local controller of every parallel inverter through low-bandwidth communication. In the local controller, a characteristic order harmonic positive- and negative-sequence compensation voltage vector is calculated and is superposed with a reference voltage vector and a virtual impedance voltage vector to synthesize and correct a voltage regulating reference vector, and imbalance compensation and harmonic suppression of the common bus voltage is carried out through inverter voltage and current control. By applying the method provided by the invention to an island microgrid multi-inverter parallel system in which a common bus is connected with a three-phase imbalance load and a nonlinear load, three-phase voltage balance of the microgrid can be maintained, output voltage distortion of three-phase inverters can be reduced, and output power of the parallel inverters can be accurately allocated.

A system may include an uninterruptible power supply (UPS) configured to provide power to a load via a bypass feed path coupled to a first power source or via an inverter feed path coupled to a second power source. The UPS may include a controller configured to switch between providing power to the load via the bypass feed path and the inverter feed path based at least in part on a real-time calculation of an amount of voltage distortion present on a voltage signal input to the load via the bypass path. As such, the controller may be configured to provide power to the load via the inverter feed path when the amount of voltage distortion is greater than a limit.

The invention discloses a high-power simplified electrolytic and electroplating high-frequency switch power supply and a control method thereof. The simplified electrolytic and electroplating high-frequency switch power supply comprises a three-phase inverter based on three phases and two arms, and a high-frequency DC / DC converter that is formed by serially connecting a single-phase half-bridge inverter, a high-frequency coupling transformer and a low-voltage full-wave rectifier; the three-phase inverter based on the three phases and two arms is formed by connecting two switch arms and two serially-connected capacitor branches at the direct-current side in parallel; the single-phase half-bridge inverter is formed by connecting a switch arm and two serially-connected capacitor branches at the direct-current side in parallel; the three-phase inverter and the single-phase half-bridge inverter commonly share one group of direct-current side capacitors; the input terminal of the three-phase inverter is connected with a power network by a three-phase inductor L; and the output terminal of the three-phase inverter is connected with the single-phase half-bridge inverter. The switch power supply has few switch devices, small loss, high efficiency, small direct-current ripples, high response speed and small voltage distortion and current distortion. The method in the invention has the advantages of improving the response speed of the three-phase inverter and tracking the change of the load power in real time.

A double dropping voltage half-bridge inverter relates to lag loop current control in which the main circuit is composed of two dropping voltage circuits, namely, power Vd1, power switch tube S1, filter inductor L1, filter capacitor C1 and continuous diode D1 to form a dropping voltage inversion circuit and the other inversion circuit is made up of power Vd2, power switch tube S2, filter inductorL2, filter capacitor C and continuous diode D2 which does not need any biased operation circuit to and reduce conductive loss of main circuit apparatus. Since this circuit applies nonlinear lag loop control and automatically adjust increasing switch frequency to limit high frequency ripple of inductance current in a definite loop width, this invention eliminates output voltage distortion resultedfrom continuous or discontinuous inductance current.

The invention discloses a superconductive current-limiting energy storage circuit and a control method thereof. A superconducting magnet is connected in series with a power grid through a current source converter, a filter capacitor, a switch, a voltage dependent resistor, a transformer and the like. In a normal state, the voltage of the filter capacitor is changed and the voltage distortion of the power grid is compensated by controlling the current injected into the filter capacitor by the current source converter so as to improve the quality of the power supply voltage of a load. When a circuit is short-circuited, the filter capacitor is disconnected with the power grid through the switch and the voltage dependent resistor, and all the switches of the current source converter are turned on, so that the superconducting magnet is connected in series with the power grid in the form of uncontrolled rectifier so as to limit the fault current.

The invention relates to photovoltaic power generation device and method based on amplitude-phase control, belonging to the technical field of power electronics. An AC side voltage and current sensor detects three-phase AC voltage and current, and the three-phase AC voltage and current are processed by a voltage and current translation circuit and then transmitted to a DSP of a main control unit for processing; the DSP determines the output vector of voltage regulation through the amplitude-phase control and inner loop control according to set values of the detected AC side current and voltage and DC side voltage and transmits the output vector to an FPGA; output voltage received by the FPGA and a waveform generated by a triangle generator are synthesized into a PWM waveform to be transmitted to a driving and amplifying unit; and a switching device of a main circuit unit generates switch-on and switch-off according to an amplified pulse signal. The photovoltaic power generation method successfully reduces the AC side voltage distortion rate, is suitable for multiple load types, reduces the influence of load current change on output AC voltage and enhances the fast response capacity.

The invention provides a metering error quantitative analysis method for an electric energy meter under a harmonic wave condition. According to the method, a metering error is expressed as an expression of the harmonic wave voltage distortion rate, the harmonic wave current distortion rate and the power factor, and an influence rule of the harmonic wave voltage distortion rate, the harmonic wave current distortion rate and the power factor to the metering error is quantitatively analyzed. The analysis method and result can provide an important basis for improving the accuracy and the reasonableness of a metering system under the harmonic wave condition.

The invention discloses a harmonic current detection method for a novel active power filter (APF). According to the method, for the acquired voltage of a common connection point in a three-phase power grid voltage unbalanced system, the relationship between the grid-side voltage and the compensated grid-side current is represented through introducing an electrical conductance factor. The effective value of a fundamental positive sequence voltage is calculated according to the power conservation principle of the active power filter. Meanwhile, a lagrangian function between the harmonic content of the power grid current and the power grid voltage is constructed, and a target power grid current is obtained through the method of seeking extreme values. Meanwhile, the difference between the target power grid current and a load current is figured out and then is inverted, so that a compensating current command value is obtained. Therefore, the power control of the active power filter is realized, and a control signal is generated based on the PWM technique. The output of the active power filter is controlled. According to the technical scheme of the invention, the phase voltage in the traditional algorithm is replaced by the fundamental wave positive sequence component of the voltage, so that the compensated current waveform of the system is kept to change synchronously along with the fundamental wave positive sequence component of the voltage. Therefore, the defect in the prior art that harmonics cannot be completely eliminated during the power grid voltage distortion process can be overcome.

The invention discloses a series electric energy quality controller, including: an electric energy detecting unit, a control unit, an offset voltage generator, a DC unit, a connect unit and a protective unit It is equivalent to a voltage source in series with the distribution wire of a system to eliminate the effect of system voltage distortion on a load, and is a load-oriented electric energy quality improving device. It is connected in series between the system and load, and quickly outputs an offset voltage as the voltage waveform is distorted, so as to avoid the sensitive load from being affected by the system voltage fluctuation and assure the power supply quality for the sensitive load. It can effectively solve the quality problems of dynamic voltage, like voltage drop, etc., and also give consideration to the quality problems of stable voltage, such as system voltage harmonics, voltage fluctuation, three-phase imbalance, etc..

The invention discloses a grid-connected seamless switching controller based on a capacitive current inner ring and a control method thereof. The controller comprises a microcontroller, a voltage sampling circuit, a grid-connected switch driving circuit and an inverter power tube driving circuit, wherein the microcontroller comprises an electricity grid synchronous module, an output voltage controller, a capacitive reference current generator under a grid-connected mode, a grid inlet current controller, a capacitive current controller, a control command selecting switch and an inverter power tube logic generator. The grid-connected seamless switching controller is connected with an inverter of an electricity grid through a grid-connected switch, is in an output voltage control mode when in dependent operation with load and is in a grid inlet current control mode when in grid-connected operation. The grid-connected seamless switching controller is adaptable to a grid-connected inverter capable of independently operating with grid-connected double modes, increases output voltage load adjustment rate under an independent mode, increases power factors and grid inlet current waveform quality on the condition of non-linear load and electricity grid voltage distortion under a grid-connected mode, and then realizes seamless switching of two work modes.

There are provided a smoothing capacitor (71) for storing an induced electromotive force generated by a three-phase induction motor (5), a regenerative transistor (81 to 86) for switching a terminal voltage of the smoothing capacitor to carry out a power regenerating operation over a three-phase AC power supply (3), a line voltage detecting portion (6) for detecting a line voltage of the three-phase AC power supply, a fundamental waveform generating portion (10) for generating, from a signal output from the line voltage detecting portion, a fundamental waveform defined to be a line voltage waveform of the three-phase AC power supply in which a source voltage distortion component is not mixed, a base driving signal creating portion (7) for creating a base driving signal to be used for an ON / OFF control of the regenerative transistor based on a signal output from the fundamental waveform generating portion, and a base driving signal output portion (9) for outputting the base driving signal.

Methods and apparatus are provided for reducing voltage distortion effects at low speed operation in electric drives. The method comprises receiving a first signal having a duty cycle with a range between minimum and maximum achievable duty cycles, producing a second duty cycle based on the minimum achievable duty cycle if the duty cycle is within a distortion range and less than a first clipping value, producing a second duty cycle based on the closer of minimum and maximum pulse widths if the duty cycle is within the distortion range and between the first and a second clipping value, producing a second duty cycle based on the maximum achievable duty cycle if the duty cycle is within the distortion range and greater than the second clipping value, and transmitting a second signal to the voltage source inverter having the second duty cycle.

The invention relates to a three-ring control method of a three-phase PWM (Pulse-Width Modulation) rectifier for LCL (Lower Control Limit) filtering and belongs to the field of rectifier control. The three-ring control method is characterized in that an output voltage of a rectifier, a grid-side inductive current, an inductive current at the side of a rectifier bridge are respectively sampled by using a group of voltage detection transmitters and two groups of current detection transmitters so as to control an output direct-current voltage and a grid-side power factor of the three-phase PWM rectifier. The control method provided by the invention has the outstanding advantages that the output direct-current voltage of the three-phase PWM rectifier is controlled with high precision and good stability; the grid-side power factor is high; the capability of resisting voltage distortion interference of a power grid is strong; and a bridge arm switching tube is convenient to protect, the control method has high reliability and the like. Therefore, the control method provided by the invention is very suitable for controlling the three-phase PWM rectifier for the LCL filtering.

The invention discloses a control method for a three-phase PWM rectifier suitable for power grid waveform distortion. The control method for the three-phase PWM rectifier suitable for the power grid waveform distortion mainly includes that extracting a current reference signal under input voltage distortion and unbalanced disturbance, and actively injecting negative-sequence current, improved dead-beat inner current loop which is forecast through combining with linear extrapolation, and outer direct voltage loop performed with active disturbance rejection control. The control method for the three-phase PWM rectifier suitable for the power grid waveform distortion plays roles of inhibiting the harmonic wave of the input current of the PWM rectifier, injecting proper negative-sequence current to eliminate the secondary power pulse of the output direct current voltage of the PWM rectifier, improving the transient response of the output direct current voltage, and compensating the influences of all kinds of delay on the dead-beat control. The control method for the three-phase PWM rectifier suitable for the power grid waveform distortion is capable of obviously reducing the secondary wave of the output direct current voltage under the disturbance of the input harmonic wave and unbalanced voltage, improving the transient response speed of the PWM rectifier, reducing the transient offset of the direct current voltage, and improving the system control precision.

A method of compensating output voltage distortion of a half-bridge inverter and a device based on the method discloses that the method includes the steps of measuring the voltage of the capacitor of the half-bridge inverter and then detecting the output voltage of the same; comparing the capacitor voltage and the output voltage to identify how much degree the distortion is resulted from the capacitor voltage unbalance, wherein if the degree of the distortion matches a predetermined condition, proceed to the next step; and charging the capacitor through a compensating circuit to compensate the capacitor for the insufficient electric energy to enable the capacitor to provide the load with the sufficient electric energy. Thus, the drawback that the waveform of the output voltage can be improved to enable the device and the method to have advantages of simple circuit, easy control, reduced capacitance, and being applicable to any output frequency.

The invention provides a passive filter parameter design method based on a multi-objective optimization algorithm. The method is characterized by: firstly, analyzing and establishing a topology structure model of an electric power system; regarding a reactive power capacity which can be compensated for the electric power system as a constraint condition, taking a size of each harmonic current of a filtering channel and a voltage distortion rate as an optimization object so as to obtain a constrained multi-objective optimization problem; finally, using a genetic algorithm to solve the constrained multi-objective optimization problem and optimally calculating so as to obtain a Pareto optimal solution set with various kinds of characteristics which can be selected by a designer. By using the method of the invention, during designing the passive filter of the electric power system, a minimization problem of the each harmonic current of the filtering channel and the voltage distortion rate can be solved and the passive filter can be guaranteed to acquire the best filtering effect.

The invention discloses a method and a device for obtaining power grid synchronic benchmark sine based on the absence of a phase lock loop. The method includes the following steps: firstly, a power grid voltage es of a single-phase power grid or one phase of a three-phase power grid is adopted, the power grid voltage es and reference sin(omega 0t +theta ) and cos (omega 0t +theta) with preset frequencies are processed in a second-order active low-pass filtering mode, and low-frequency signals are extracted to obtain Udcos and Udsin. Secondly, a fundamental wave es1 of the power grid voltage and a power grid voltage fundamental wave orthogonal signal e's 1are obtained. Thirdly, mathematical models of single-phase power grid synchronic sine and cosine are obtained through the power grid voltage fundamental wave es1 and the orthogonal signal e's 1. And lastly, the power grid synchronic sine and the cosine obtained from the third step are introduced to a controller of a grid-connected inverter, so that the current introduced into the power grid and the power gird voltage are guaranteed to be in the same frequency and in the same phase. The method and the device are capable of automatically obtaining the power grid synchronic benchmark sine under the conditions of power grid voltage distortion, multiple times of zero passage of voltage waveform and voltage fluctuation.

The invention discloses a dead-zone compensation method and compensation system for a frequency converter, and relates to the technical field of motor control. According to the scheme, on the basis of a hardware dead-zone compensation method, software correction is carried out on a hardware pulse width detection error, so that the problem of output voltage distortion under a low-current condition is greatly improved; an output voltage error caused by dead time can be detected at extremely high accuracy; dead-zone compensation can be accurately carried out; the output voltage distortion is greatly reduced; and output current harmonic distortion is suppressed.