355 results about "Sinusoidal current" patented technology

The invention relates to a super capacitor energy storage type power quality compensator. A system structure comprises a compensation transformer, a series compensator, a parallel compensator, a super capacitor group, a current foldback circuit, a bidirectional DC/DC chopper circuit, a signal sampling circuit, a control circuit, a drive circuit, a human-computer interface and corresponding auxiliary circuits, which form a three-phase three-wire system topological structure. By utilizing the excellent characteristics of great power density, high charging and discharging speed and long cycle life of a super capacitor, the super capacitor energy storage type power quality compensator is matched with the DC/DC chopper circuit to form an energy storage control system which plays the roles of adjusting power and stabilizing the voltage of a direct current bus in work. The invention also has the functions of dynamic voltage recovery, active filter and reactive compensation and can ensure that a load can obtain rated sine voltage and the current of a grid is sine current with the same direction (unit power factor) with that of a voltage fundamental wave positive sequence active component, thereby comprehensively improving the quality of power. The invention has positive generalization and application value for both the public grid and users.

The invention relates to a control method which can be applied to an active-clamp flyback miniature photovoltaic grid-connected inverter device. The active-clamp flyback miniature photovoltaic grid-connected inverter device comprises a flyback converter and a power frequency polarity conversion circuit. In the device, a current reference is used for controlling a flyback primary-side current peak value so that the device can output a half-wave sinusoidal current, and the output voltage is clamped by a grid voltage. When the instantaneous power is lower, a constant frequency current discontinuous mode in combined with a variable frequency current critical continuous mode is adopted in the flyback control method. When the flyback converter works in a variable frequency current critical discontinuous mode, an auxiliary switching tube can be conducted for a period of time when the secondary-side current of the flyback converter reaches zero, the conduction time can be accurately controlled by a digital chip, thus realizing the leakage inductance energy feedback and the soft switch of a master switching tube under the condition of wide-range output voltages and different instantaneous powers and greatly improving the efficiency under the condition of full loads.

A power generation system including a photovoltaic (PV) module to generate direct current (DC) power is provided. The system includes a controller to determine a maximum power point for the power generation system and a boost converter for receiving control signals from the controller to boost the power from the PV module to a threshold voltage required to inject sinusoidal currents into the grid. A DC to alternating current (AC) multilevel inverter is provided in the system to supply the power from the PV module to a power grid. The system also includes a bypass circuit to bypass the boost converter when an input voltage of the DC to AC multilevel inverter is higher than or equal to the threshold voltage.

This invention discloses a dual-feed AC-DC-AC converter control structure for wind power generation, and the rotor exciting magnetic converter using the fuzzy PI adaptive control strategy of current inner loop. When the generator no-load networking, the current inner loop uses the conventional PI regulator, and after networking, as to three modes, sub-synchronization, synchronization, super-synchronous, it uses fuzzy adaptive PI control. The network-side converter uses SPWM control strategy which fixed switching frequency and combining electric network electromotive front-feed. In the invention, both converting processes use four-quadrant operation PWM converters based on full-controlled devices, so it can not only improve the system dynamic response, reduce wastage and impact, achieve the two-way electric transmission, but also it can achieve wind power generation network side unit power factor sinusoidal current networking power generation operating.

An AC/DC power converter has an AC input and a DC output, with an input rectifier circuit coupled to the AC input. The input rectifier circuit includes a passive half-bridge rectifier circuit functional to provide passive rectification of an AC input power sign and at least one current shaper circuit. The current shaper circuit includes an input inductor coupled between the AC input and a switch node in the input active rectifier circuit. The input current shaper circuit is functional to shape an AC input current signal associated with an AC input power signal to a substantially sinusoidal current signal. A bulk capacitor circuit is coupled to the input active rectifier circuit. A DC/AC converter circuit is coupled to the bulk capacitor circuit. A resonant circuit is coupled to the DC/AC converter circuit and an output rectifier circuit may be coupled between the resonant circuit and the DC output.

Based on the measurement of the increase of sinusoidal voltage ΔV=V_maxsine(2πft) on adding a sinusoidal current ΔI=I_maxsine(2πft+φ) to the battery current, where f is the frequency and I_max, the amplitude of the superimposed current, with whose magnitudes the electrochemical impedance of the battery Z(f)=V_max/I_maxe^jφ is calculated, comprising the application of a first sinusoidal signal of prefixed frequency to the battery which generates an alternate voltage component superimposed over the direct one; eliminating the direct component of the response signal; applying a second periodic voltage signal with a frequency identical to that of said first signal and carrying out a synchronous detection of the alternate component generated by the application of said first signal to obtain the voltage proportional to the electrochemical impedance and evaluate the state of health and charge of the battery.

Systems, methods, and apparatus for providing power to an electrosurgical instrument. In particular, a power supply is disclosed in which non-sinusoidal (e.g., pulsed) constant frequency voltage having a variable amplitude is passed to an LC circuit to produce a quasi-sinusoidal current in the LC circuit. The constant driving frequency can be one half the resonant frequency of the LC circuit allowing the LC circuit to operate as an impedance, and thus limit current spikes and arcing. The frequency and phasing of the driving voltage also enables the LC circuit to discharge energy back into a power provider of the power supply so that energy does not build up in the LC circuit. These features result in less severe current spikes and arcing, as well as reduced cutoff times.

Rectifying elements are connected in parallel with switching elements 4-1 through 4-4 in a switching section 4 for the lower voltage side and rectifying elements are connected in parallel with switching elements 5-1 through 5-4 in a switching section 5 for the higher voltage side. An LC resonant circuit 6 is provided between the winding wire 3-2 for the high-voltage side in the transformer 3 and the switching section 5 for the higher voltage side; currents which flows on the primary side and the secondary side is changed into a sinusoidal one; and switching is executed in the vicinity of the zero crossing points of the currents.

An electronic ballast is provided which is capable of compactly powering a discharge lamp from a source of rectified, but unregulated, power having a varying DC voltage. The ballast includes a self-oscillating converter powered by the DC voltage for producing pulses at a nominal operating frequency which is determined by a resonant tank. The resonant tank converts the pulses to a sinusoidal current for powering the discharge lamp and includes an inductive impedance in series with the lamp for providing a voltage drop which varies with the operating frequency. A feed-forward control circuit is coupled to the converter for varying the operating frequency directly with variations in the DC source voltage. The voltage drop across the inductive impedance is substantially proportional to the magnitude of the DC source voltage. This enables regulation of the voltage supplied to the discharge lamp by the ballast without sensing the lamp voltage itself.

A permanent-magnet micro-robot consists of a casing (5), an axially magnetized permanent magnet (1), a radially magnetized permanent magnet (2), a non-magnetic miniature bearing (3) and a propeller (4), wherein, the head of the casing (5) is round and smooth, and a bottom (6) has a cavity (7) which is filled with lubricating grease; the axially magnetized permanent magnet (1) and the radially magnetized permanent magnet (2) are connected by the non-magnetic miniature bearing (3); the radially magnetized permanent magnet (2) and the propeller (4) are fixed via an axle (8) of the propeller. An outside magnetic field is generated by a rotation magnetic field device and a uniform magnetic field device, wherein, the rotation magnetic field consists of three groups of perpendicular Helmholtz coils, a sinusoidal current source and a phaser; the uniform magnetic field device consists of three groups of perpendicular Helmholtz coils and three groups of direct current sources. Under the effect of the rotation magnetic field, the robot rotates with the radially magnetized permanent magnet (2) and produces the axial driving force to drive; at the same time, under the deflecting guidance of the uniform magnetic field, the robot realizes flexible steering and moves along an expected locus.

A photovoltaic powered system and an alternating current (AC) module thereof are disclosed. The photovoltaic powered system provides a direct current (DC) power through a photovoltaic module and converts the DC power into an AC power, which is grid-connected to an AC utility power. The AC module of the photovoltaic powered system produces a continuous quasi-sinusoidal current and the quasi-sinusoidal current is converted into a sinusoidal current. The high-frequency harmonic components of the sinusoidal current are filtered to produce a sinusoidal output current in phase with the AC utility power, thus realizing the maximum power point tracking (MPPT) of the photovoltaic module and feeding unity-power-factor power into the AC utility power.

The invention discloses a totem-pole PFC fully-digital control method and device. The method comprises acquiring corresponding voltage and current information through a sampling module, after digitalphase locking is completed, computing effective value and phase value of input voltage, adjusting error signals through a voltage outer loop adjuster and a current inner loop adjuster, and performingfeed forward compensation on an output duty ratio through duty ratio feed forward. According to the totem-pole PFC fully-digital control method, by introducing the duty ratio feed forward, the currentinner loop adjuster only needs to inhibit small signal disturbance, so that the capability of a controller on tracking power frequency sine-wave current; by collecting the zero crossing point of input voltage for digital phase locking, querying a sine table to acquire the phase value of the input voltage, collecting the real-time value of the input voltage for effective value computation and taking the computed real-time value of the input voltage as input current instruction value and the input value of a feed forward duty ratio computing module, the totem-pole PFC fully-digital control method can eliminate output duty ratio disturbance led by input voltage sampling deviation and improve anti-interference performance and stability of digital control totem PFCs.

The invention relates to an asynchronous motor parameter identification method, in particular to an asynchronous motor parameter off-line identification method. Sine-wave current signals with different frequencies are accessed to an asynchronous motor stator winding twice; equivalent total leakage inductance and mutual inductance are computed according to a T-shaped equivalent circuit in a motor single phase test; trapezoid current signals are accessed to an asynchronous motor stator resistance; the output voltage of a frequency converter on the ascent stage of the trapezoid current signals is detected; a stator leakage inductance and a rotor leakage inductance of an asynchronous motor are computed; the output voltage V of the frequency converter at the horizontal stage of the trapezoid current signals is detected; and an asynchronous motor rotor resistance is computed. Due to the adoption of the method, the parameters of an asynchronous motor can be rapidly identified, and meanwhile, the output of the frequency converter can track the given current signals through a PI (proportional integral) current controller; and the zero crossing point distortion of current which is caused by the influence of frequency converter tube voltage drop and dead zones can be avoided through adding direct current bias in the input current signals of the frequency converter.

The invention relates to a small-current grounding system single-phase grounding fault distance measurement method based on a signal injection method. Under a single-phase grounding fault, a constant-frequency sine current signal is injected through a voltage transformer during secondary lateral fault phase short circuit; the current generates a corresponding voltage drop on a faulted line; relational expressions between injection signal voltage and injection signal current at the head end of the line and the injection signal voltage and the injection signal current on a faulted point can be written by adopting a distribution parameter model of the line based on a long-line equation; relational expressions between the injection signal voltage and the injection signal current on the faulted point and transitional resistance can be also written; the virtual part of the transitional resistance is set to be 0 and the plural equations are solved, so that a fault distance can be obtained. The small-current grounding system single-phase grounding fault distance measurement method based on the signal injection method has the advantages that: due to adoption of an injection signal for distance measurement, influences of a system structure, a running mode and an arc suppression coil can be avoided; due to adoption of the distribution parameter model of the line, an influence of a distribution capacitor can be avoided; therefore, a distance measurement result has higher precision, and the small-current grounding system has high anti-transitional-resistance capability.

Energy storage cell impedance testing devices, circuits, and related methods are disclosed. An energy storage cell impedance measuring device includes a sum of sinusoids (SOS) current excitation circuit including differential current sources configured to isolate a ground terminal of the differential current sources from a positive terminal and a negative terminal of an energy storage cell. A method includes applying an SOS signal comprising a sum of sinusoidal current signals to the energy storage cell with the SOS current excitation circuit, each of the sinusoidal current signals oscillating at a different one of a plurality of different frequencies. The method also includes measuring an electrical signal at a positive terminal and a negative terminal of the energy storage cell, and computing an impedance of the energy storage cell at each of the plurality of different frequencies using the measured electrical signal.

In an electric power steering system, an ECU 11 that controls the operation of the system includes three independent microcomputers 18u, 18v, 18w that perform phase current feedback control with respect to the corresponding phases, so that sinusoidal current is applied to each phase of the motor 12 as a non-connected motor. Also, each of the microcomputers 18u, 18v, 18w monitors a deviation of an actual current value from a phase current command value, with respect to each of two phases other than the corresponding phase, and determines that an abnormality occurs in the phase in question when the deviation exceeds a predetermined threshold value. When two of the microcomputers 18u, 18v, 18w determine that the abnormality occurs in the remaining one phase, the ECU 11 confirms the determination that the phase in question is in an abnormal condition.

A bi-directional boost circuit for power factor correction includes a power factor control circuit and a pair of diodes, a pair of inductors, and a pair of switches. A first diode, a second diode, a first inductor, a second inductor, a first switch, and a second switch convert the AC input voltage, rectify the AC input voltage, and output an intermediate DC voltage. The power factor control circuit receives the AC input voltage and receives the intermediate DC voltage. The power factor control circuit regulates the DC output voltage. Based on the AC input voltage and the intermediate DC output voltage, the power factor control circuit controls an inductor current waveform by driving the first switch and the second switch to create a substantially sinusoidal current as seen by the power source that is in phase with the AC input voltage.

An apparatus and method for estimating rotor angle information for the control of permanent magnet AC motors having sinusoidal current excitation. The disclosed motor drive can provide full load operation at very low speeds including zero speed without the use of a shaft position sensing device. The rotor angle is estimated through injection of high frequency current, and rotor angle is extracted by a signal-conditioning algorithm, which utilizes current amplitude differential to discriminate the rotor angle. Rotor angle magnetic axis orientation (North or South pole) at startup is detected by comparing time average current ripple (at signal injection frequency) content between two different levels of d-axis current injection.

The invention discloses a parameter recognition method for a permanent magnet synchronous motor of an electric vehicle. The method comprises the steps of judging whether the permanent magnet synchronous motor of the electric vehicle needs parameter recognition or not; when parameter recognition needs to be carried out, injecting a low-frequency small-amplitude sinusoidal current signal into quadrature-axis expected current of the permanent magnet synchronous motor, and automatically adjusting the quadrature-axis expected current, direct-axis expected current, quadrature-axis voltage and direct-axis voltage by an adjuster; the rotating speed and position signals of the permanent magnet synchronous motor are measured through a rotating speed sensor, three-phase current of the permanent magnet synchronous motor is collected through a current sensor and converted into direct-axis feedback current and quadrature-axis feedback current, and data are transmitted to a parameter recognition linkin real time; and performing parameter recognition on the permanent magnet synchronous motor through the parameter recognition link until the parameters converge. According to the method, parameter recognition can be carried out under any operation state of the motor, the control requirements of the permanent magnet synchronous motors with different structures can be well met, the identified parameters are accurate, and the application range is wide.

The invention discloses a single-phase non-isolated photovoltaic grid-connected inverter and a control method. The photovoltaic grid-connected inverter mainly comprises a half-bridge circuit, a full-bridge circuit and a control circuit, wherein the control circuit controls the half-bridge circuit and the full-bridge circuit, so that the half-bridge circuit can be modulated in a high-frequency sinusoidal pulse width modulation (SPWM) mode to output half-sinusoidal current, and the full-bridge circuit can commutate in an industrial-frequency mode to commutate the half-sinusoidal current output by the half-bridge circuit and output sinusoidal current required for grid connection. The photovoltaic grid-connected inverter can ensure that the problem of common-mode current in the non-isolated grid-connected inverter circuit is effectively solved, the distortion of the current at the zero crossing point is reduced and the high-frequency switching loss in the circuit is low at any time.

A DC-to-AC power converter is disclosed. The power converter has a DC input to receive DC power from a photovoltaic device, an AC output configured for direct connection to an AC mains power supply line, six semiconductor switches, one isolated high-frequency power transformer, two high-frequency inductors, a small resonant capacitor, and a large non-electrolytic (e.g. film) capacitor energy storage component. One of the semiconductor switches located on the primary side of the transformer operates to regulate the voltage across the non-electrolytic capacitor energy storage component. A second semiconductor switch located on the primary side of the transformer provides a resonant reset for the energy stored in the transformer and allows the first semiconductor switch to operate with nearly zero-voltage-switching. The other four semiconductor switches and a high-frequency inductor coupled to the ac output operate with a variable switching frequency to produce a sinusoidal current into the ac output such that the sinusoidal current may be either in phase or out of phase with the ac output voltage.