806 results about "Voltage loop" patented technology

A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal by multi-sampling a voltage signal of a transformer. The discharge-time signal represents a discharge time of a secondary-side switching current. A voltage-loop error amplifier amplifies the voltage-feedback signal and generates a control signal. An off-time modulator correspondingly generates a discharge-current signal and a standby signal in response to the control signal and an under-voltage signal. The under-voltage signal indicates a low supply voltage of the controller. An oscillator produces a pulse signal in response to the discharge-current signal. The pulse signal determines the off-time of the switching signal. A PWM circuit generates the switching signal in response to the pulse signal and the standby signal. The standby signal further controls the off-time of the switching signal and maintains a minimum switching frequency. The switching signal is used for regulating the output of the power supply.

The invention provides a grid-connected generation control method for a photovoltaic power generation converter. The method comprises the following steps of: grid voltage software phase lock, voltage outer loop establishment, current control and grid voltage orientated vector control, wherein the grid voltage software phase lock adopts a software three-phase phase-locked loop method; a phase-locked loop consists of a phase detector, a loop filter and an oscillator; the grid voltage orientated vector control adopts a double-closed-loop cascade control structure, namely a voltage outer loop and a current inner loop; the voltage loop controls a direct-current bus voltage; and the current loop controls an alternating-current side input current. By the method, the orientation is accurate, the direct-current bus voltage is controlled to be stable, and maximum power point tracking control is realized. Deadbeat control design is performed aiming at the current loop, so that the current loop controls the alternating-current side input current according to a current command given by the voltage loop and unit power factor operation is realized. By adopting a feedforward decoupling control method, stable grid-connected operation can be realized.

The invention discloses a space vector modulation based harmonic current compensation system for a high-speed permanent magnet motor. The system comprises a rotor position and speed observation module, a stator phase current harmonic compensation module, a phase current feedback module, a rotation speed PI adjustment module, a current PI adjustment module and an SVPWM (space vector pulse width modulation) conversion output module. The stator phase current harmonic compensation module comprises a harmonic current extraction module, a proportional controller, a harmonic current adjustment module and a harmonic voltage compensation amount calculation module. The harmonic current extraction module extracts phase current harmonics of a permanent magnet synchronous motor in real time by the aid of an adaptive band-pass filter; the proportional controller adjusts the harmonic current and feeds the harmonic current to a current loop; the harmonic current adjustment module and the harmonic voltage compensation amount calculation module are used for calculating harmonic voltage compensation amount on the basis of a mathematical model of the high-speed permanent magnet motor and feeding back to the voltage loop. By the space vector modulation based harmonic current compensation system for the high-speed permanent magnet motor, voltage compensation amount can be calculated accurately, real-time compensation can be realized, phase current waveforms in operation of the permanent magnet synchronous motor can be improved effectively, torques and rotation speed pulses can be reduced, and accordingly operation efficiency, stability and reliability of the motor can be improved.

Controller of LED lighting to control the maximum voltage of LEDs and the maximum voltage across current sources is provided. A voltage-feedback circuit is coupled to the LEDs to sense a voltage-feedback signal for generating a voltage loop signal. Current sources are coupled to the LEDs to control the LED currents. A detection circuit senses the voltages of the current sources for generating a clamp signal in response to a maximum voltage of the current sources. Furthermore, a buffer circuit generates a feedback signal in accordance with the voltage loop signal and the clamp signal. The feedback signal controls the maximum voltage of the LEDs and the maximum voltage across the current sources.

The invention relates to a low and medium power high frequency DC-DC converter suitable for high-voltage input, which is based on the fundamental principle that: series capacitors are connected to a high-voltage direct current input, each capacitor serves as an input of the high-frequency forward DC-DC converter, and the outputs of the high-frequency forward DC-DC converter share a filter inductor, a freewheeling diode and an output filter capacitor; voltage feedback is acquired by sampling the output voltage of the high-frequency forward DC-DC converter, and a given reference voltage is compared with the voltage feedback so as to obtain a voltage loop output, namely a main output, by voltage regulation and calculation; and then, high-frequency forward DC-DC converter driving signals which are equational and alternate in phase are acquired to realized the control over a main circuit. The DC-DC converter has the advantages that: a low-voltage switching element is used under high voltage direct current input; the topology is simple; the cost is low; and the output has excellent dynamic and static performance.

A control method for a high-voltage direct-current flexible system for supplying power to a passive network includes: arranging a rectifier controller at the head end of a direct-current transmission line of the high-voltage direct-current flexible system, performing constant direct-current voltage control for a VSC (voltage source converter)-rectifier on the alternating-current system side, arranging a VSC-inverter controller at the tail end of the direct-current transmission line, and performing constant direct-current voltage control for the a VSC-inverter. A double closed-loop vector control policy is used for VSC-rectifier constant direct-current voltage control, fuzzy PI (proportional integral) control is used for an outer voltage loop, and current decoupling control is used for an inner voltage loop, so that active power and reactive power are controlled independently. The method avoids complicated offline parameter adjustment of a traditional PI adjustor and is capable of performing online PI parameter adjustment according to changes of the system running state and high in adaptive adjustment capability, the system is higher in response speed and control precision for various interferences and failures, and anti-interference capability and dynamic and steady-state performances of the system are improved.

The invention discloses an exciting current given device for an induction motor of an electric vehicle. On the basis of the prior art, the exciting current given device is additionally provided with an exciting current limiting calculation module and a limiting PI (proportional integral) control module. When the induction motor normally runs, the calculated amplitude limiting maximum value (isd.Max) of the exciting current decreases along with the increase of the real synchronous speed omega e. The exciting current isdref of a voltage loop PI controller decreases under the condition of invariable maximum voltage vector (usm). Due to the decrease of the exciting current (isdref), the counter electromotive force of the induction machine decreases, therefore, under the condition of invariable busbar voltage uDC, the induction motor can rise to a higher rotating speed. In addition, according to the exciting current given device of the induction motor of the electric vehicle, the calculation of switching points among a constant torque area, a constant power area and a constant voltage area is eliminated, so that the level jump of output exciting currents caused by the inaccurate calculation of switching points can be effectively prevented, the given value of the exiting currents can vary stably, the joggling of the induction motor control caused by the level jump of the given valueof the exciting currents is reduced, and the safety of the induction motor control is improved.

An amplifier circuit comprising an amplification chain having a differential output stage; a common mode correction block acting on the input of the output stage as a function of a common mode voltage at the output of said stage and introducing a phase shift between its input and its output for frequencies close to the cut-off frequency of the circuit; and, in parallel with the correction block, a means introducing no phase shift between its input and its output and having at frequencies greater than or equal to the circuit cut-off frequency an output impedance much smaller than the output impedance of the correction block.

The invention discloses a self-adaptive fuzzy control method for an active power filter based on feedback linearization, relates to the technical field of an active power filter, and respectively designs independent self-adaptive controllers aiming at a current loop and a voltage loop. As the current loop adopts the self-adaptive fuzzy controller for the active power filter based on the feedback linearization, the feedback linearization theory, fuzzy control, sliding mode control, self-adaptive control and Lyapunov stability theory are comprehensively utilized, and on the basis of ensuring the global stability, the purpose of harmonic compensation is realized. As the voltage loop adopts the self-adaptive fuzzy PI (process integration) control, according to the fuzzy rule, the control strategy can automatically adjust the PI parameter, strengthen the robustness of the system, improve the dynamic performance of the system, and ensure the tracing to the command voltage.

The invention discloses a control method and a system for inhibiting a secondary ripple current and improving a dynamic characteristic. A voltage-current double closed-loop control is carried out on a front-stage direct-current (DC) converter, wherein the secondary ripple current in the front-stage DC converter is inhibited by lowering the cut-off frequency of a voltage loop greatly; a load current feed-forward is adopted on the basis of the double closed-loop control; and a wave trap is added to a feed-forward branch circuit to filter out a double frequency component in a feed-forward signal, thereby inhibiting the second ripple current in the front-stage DC converter and improving the dynamic characteristic of the front-stage DC converter in load hopping. As a result, the efficiency of the DC converter is improved.

The invention relates to an improved droop control based microgrid auxiliary master-slave control method. The method is used for maintaining stability of the voltage and power of the microgrid. The microgrid comprises multiple DGs connected with alternating current buses respectively; each DG comprises a master-control DG, an auxiliary DG and a slave-control DG; the master-control DG and the slave-control DG are used as a master-control unit and a slave-control unit in the master-slave control method respectively; the inverter in the auxiliary DG adopts voltage and current dual-loop control; a load current io is multiplied by a dynamic virtual impedance Zvir, and the obtained product is used as an instruction voltage to be added in a feedback signal to a voltage loop, so that the output impedance of the inverter is sensitive. Compared with the prior art, the inverter of the auxiliary DG adopts the dynamic virtual impedance, so that matching between the output impedance of the inverter and the circuit impedance can be ensured, voltage drop can be effectively relieved, and the power quality is ensured; and in addition, the improved droop control is adopted, and an integral link is introduced in the reactive power control link, so that steady state voltage without static errors is realized, and the steady state performance of the system is improved.

With the fast development of power electronic technologies, the development of power electronic system integration techniques becomes a tendency. In application situations of high-voltage input and large-current output, a DC (direct-current) converter system with multiple modules having series inputs and parallel outputs can be used widely. The key problem of the DC (direct-current) converter system with multiple modules having series inputs and parallel outputs is to ensure voltage sharing of input ends of all modules in the system. For the purpose of realizing the voltage sharing, a voltage loop, a current loop and a voltage-sharing ring are traditionally used to control, each module is required to input voltage detection signals, the circuit is complicated and the control difficulty is high. The invention provides a voltage-sharing technology among modules at input ends, thus realizing the voltage sharing of the multiple modules at the input ends. The control characteristics are as follows: a voltage-current dual-loop control method is adopted, voltage sampling is output voltage sampling, current sampling is the total current sampling of the current output of each module, and each module is controlled by the same duty ratio, thus realizing the voltage sharing at the input ends. The circuit is controlled simply and certain redundancy is provided.

The invention provides an adjusted micro-grid DC/DC convertor grid-connected control device and control method based on drooping characteristics. The output quantity of DC/DC convertor electric current loops serves as the adjustment amount of the main component of voltage loop command signals; in electric current closed loop control, command signals of an electric current loop controller come from a micro-grid upper layer energy management system or are generated by the maximum power tracing module in a distributed power generation system control software; the main component of command signals of a voltage loop controller is obtained through calculation of the actual output current according to the drooping characteristics of the preset DC/DC convertor; the PWM modulating control signal is obtained through the amplitude limiting processing of the positive saturated amplitude limiting link on the synthetic command signals of the voltage loop controller and the calculation of the voltage controller according to the command signals and the feedback actual micro-grid busbar voltage deviation. A plurality of distributed power generation systems can run at own possible best operating points and can realize stable parallel output according to own available power.

The invention discloses a tracing to the source direct current correcting method for a Delta-typed direct current. By externally adding a stable AC voltage source, AC voltage output forms a voltage channel by a voltage divider, low conversion voltage value of a voltage loop is obtained from the voltage channel; the AC voltage output of the stable AC voltage source is connected with a current transformer by a high precision resistance, thus forming a current channel; and the measured voltage value representing current is obtained from the current channel by impedance conversion; precise stable voltage direct current reference voltage and the measured conversion voltage value of the voltage loop are connected into an AC/DC voltage comparator with self correction, so as to obtain a sine voltage output by the voltage source steadily; composite ratio and angular difference of the current transformer and an equivalent impedance of a secondary load are obtained in a way that the measured voltage value obtained in the AC/DC voltage comparator is combined and connected based on the obtained sine voltage, error compensation parameters are stored for error compensation of impedance conversion measured by the following current. The invention has few error sources, simple electrical structure and high precision.

The invention relates to an energy accumulation converter-based active micro power grid seamless switching method under peer-to-peer control and belongs to the technical field of distributed generation micro power grids. The method is characterized in that a mode controller of a control layer is coordinated to perform mode switching, traditional P/Q current source control is used during grid connection, phase voltage amplitude/phase angle control based on a single voltage loop is used during grid disconnection, stable operation during grid connection and grid disconnection is achieved, easy control setting, few control links and fast dynamic response are achieved, and the problems that control manners of mode switching of existing micro power grids are basically the same, mode switching is sensitive to parameters, and control stability during grid connection and grid disconnection cannot be kept at the same time are solved. The method has the advantages that smooth switching of the operation states of the micro power grids is achieved, the output of an energy accumulation converter is smooth, continuous during switching, uninterrupted power is provided for loads and other distributed energy, and control strategies are good in universality.

The invention discloses an unsymmetrical fault ride-through method of a double-fed wind generating set. According to the method, a rotor-side convertor control circuit comprises a rotating speed outer ring and a rotor positive and negative sequence current control inner ring, and in order to eliminate the influence of direct-current decrement of a stator flux linkage, a corresponding compensation item is introduced at an outlet of a positive sequence current controller; in order to avoid the overcurrent or overvoltage of the rotor convertor, a novel current amplitude limiting link is designed, and an integral saturation link and an output amplitude limiting link are respectively introduced for the current controller; according to a network-side convertor, actual active power of a rotor is introduced in an outer ring direct-current voltage circuit to balance power on the two sides of a direct-current bus in real time; meanwhile, actual measurement negative sequence network voltage is an inner ring positive sequence current control circuit to eliminate the influence of negative sequence voltage. The defect that an existing control strategy cannot take the influences, on the network-side/rotor-side convertor, of occurrence of the generator terminal negative sequence voltage and the requirement for idle supporting of a power network in the failure period into account at the same time yet is overcome, and therefore the fault ride-through capacity of the double-fed wind generating set is improved.

The invention provides a device for detecting wear of an apparatus and a shield machine provided with the same. The device for detecting the wear of the apparatus provided by the invention comprises a resistance unit which is arranged on the apparatus to be detected and can be worn synchronously along with the apparatus, wherein the resistance unit is connected to a fixed-voltage loop; the current intensity of the resistance unit corresponds to the wearing capacity of the resistance piece one by one; and the wearing capacity of the resistance unit corresponds to the wearing capacity of the apparatus one by one. In the shield machine provided by the invention, the device for detecting the wear of the apparatus is arranged. Due to the adoption of the technical scheme, the device has the advantages of simple structure, low cost and easiness for detecting.

The invention discloses an active filtering three-phase and four-wire system type photovoltaic grid-connected system and a method. The active filtering three-phase and four-wire system type photovoltaic grid-connected system comprises a DC/DC boost circuit and a DC/AC inverter circuit, wherein the DC/DC boost circuit and the DC/AC inverter circuit are connected in series to form a circuit of a topological structure of the active filtering three-phase and four-wire system type photovoltaic grid-connected system and the decoupling control strategy is conducted on the zero-sequence current of the circuit. The DC/DC boost circuit is used for tracking a maximum power point for photovoltaic power generation. The control of the DC/AC inverter circuit is realized by an electric current loop and an electric voltage loop, wherein the decoupling control strategy is conducted on the zero-sequence current of the electric current loop and the proportion integral (PI) control strategy is conducted on the electric voltage loop. By means of the PI-controlled electric voltage loop, the voltage of a DC bus of an inverter system can be stably controlled and a photovoltaic active current reference value is generated. The method comprises three steps, namely the generation of a reference current, the decoupling control of the zero-sequence current of the electric current loop based on a Dq coordinate system, and the synthesis of a reference voltage and the pulse width modulation. According to the technical scheme of the invention, by means of the electric current loop with the zero-sequence current thereof subjected to decoupling control, not only the output of the photovoltaic active current is tracked and controlled, but also the harmonic current and the zero-sequence current of a neutral line are tracked and compensated. Therefore, the functions of photovoltaic power generation and unbalanced current compensation are realized at the same time.