335 results about "Virtual synchronization" patented technology

The invention discloses a variable power point tracking control method of a two-stage type no-energy-storage photovoltaic virtual synchronization machine, and belongs to the technical field of new energy power systems and micro-grids. The variable power point tracking control method comprises the steps of changing an original single augmented variable mode into a mode of judging whether an SUdc(k) represented DC bus voltage value is steady based on a DC bus voltage through improving the conventional perturbation observation MPPT (Maximum Power Point Tracking) method for DC/DC circuit control in a two-stage type photovoltaic system; and giving full play of a regulation effect of a DC/DC converter on the output power of a photovoltaic battery. Inertia support for the virtual synchronization machine and energy supply needed by one regulation are realized under the precondition of not adding any energy storage device; and control of the photovoltaic virtual synchronization machine is realized by combining a VSG control strategy of an inverter. When a load changes suddenly or the external environment condition changes, the photovoltaic system can reflect the characteristics of the synchronization machine, can keep steady system voltage/frequency and power balance, and can realize variable power point tracking relevant to the DC bus voltage.

The invention discloses an AC-DC hybrid micro grid bidirectional power converter virtual synchronization motor control method, and relates to the AC-DC hybrid micro grid virtual synchronization motorcontrol field; the bidirectional power converter is a three-phase voltage source type PWM converter formed by IGBT switch tubes; the AC side is connected to a AC bus via a LC filter and a line impedance Z ac; the DC side is connected to a DC bus via a DC capacitor Cdc and an line impedance Zdc; the energy bidirectional transmission can be realized respectively via a frequency control unit, a virtual excitation control unit and a bidirectional power transmission control unit; the AC frequency and DC voltage can be directly controlled so as to keep AC-DC subnet load balancing; throughput characteristics of various types of power supplies and loads of the AC-DC subnet can be fully utilized so as to provide inertia for the AC frequency and DC voltage, thus enabling the bidirectional power converter to present sagging characteristics under a stable state, and building a bidirectional power converter closed loop system small signal model so as to provide a key parameter design method.

The invention discloses a method, a device and a system for controlling photovoltaic grid connection on the basis of a virtual synchronous machine. A photovoltaic grid connection system on the basis of the virtual synchronous machine comprises a photovoltaic cell panel, a DC/DC converter and a DC/AC inverter. The photovoltaic cell panel is connected with direct-current bus, one end of the DC/DC converter is connected with the direct-current bus, the other end of the DC/DC converter is connected with an energy storage cell, the direct-current bus is connected with a direct-current side of the DC/AC inverter, and an alternating-current side of the DC/AC inverter is connected into a transformer. The method, the device and the system have the advantage that the problem that an existing photovoltaic grid connection system is incapable of simultaneously controlling photovoltaic array terminal voltages and implementing functions of an existing virtual synchronous machine can be solved by the aid of the method.

A distributed virtual synchronous-generator low voltage crossing control method is disclosed. The method comprises the following steps of using an improved virtual synchronous generator reactive powerring to accelerate a response speed of the reactive power ring and increase a reactive power support capability to a grid connection point; when a grid connection point voltage is detected to drop and an instantaneous overcurrent is detected, introducing virtual impedance control, correcting a voltage reference value and restraining the instantaneous overcurrent; using a balance current virtual synchronization control method to control positive and negative sequence currents, and when a grid connection voltage is imbalance, realizing balance control of an output current and restraining a stable state overcurrent; and according to a low voltage crossing requirement, resetting a power instruction value so that a system satisfies a reactive current injection requirement, and after a fault isremoved, setting the power instruction value to an original value. Through the above steps, low voltage crossing requirements of instantaneous and stable state overcurrent restraining, reactive current injection according to the requirement and the like are satisfied.

The present invention discloses a virtual synchronization grid-connected control method and system based on a dual stator-winding induction generator set. The generator employed by the dual stator-winding induction generator set is a dual stator-winding induction generator, control winding on the stator is connected with an inverter at a control side so as to realize effective control of the whole generator set, and power winding on the stator is connected with an uncontrolled rectifier bridge to transmit power to a direct current bus. The grid-connected control method of the dual stator-winding induction generator set employs a virtual synchronization grid-connected control method, in the microgrid inverter control method based on a virtual synchronous generator, a quasi-synchronization paralleling algorithm is added to perform presynchronization of a control algorithm, based on the virtual impedance algorithm of a second-order generalized integrator, and the space voltage vector modulation method based on a quasi-proportional resonance algorithm is employed. The virtual synchronization grid-connected control method and system based on the dual stator-winding induction generator set can realize effective and stable operation of the whole dual stator-winding induction generator set and can automatically select grid connection opportunity to allow the grid connection moment not to have impact current so as to realize effective and flexible grid connection.

The invention discloses a current transformer virtual synchronization control system under asymmetric power grid voltage and a method thereof. A cross-coupled structure of double phase-locked and amplitude-locked loops is adopted to directly control output voltage of a current transformer to be synchronized with a power grid so that output power of the current transformer is controlled. A synchronization controller is realized by adopting positive sequence and negative sequence phase-locked and amplitude-locked devices, and change of positive and negative sequence voltage can be respectively tracked so that synchronization between the current transformer and the power grid is realized when power grid voltage is asymmetric. With application of the system and the method, the current transformer is enabled to possess capability of spontaneously providing dynamic power support without time delay to the power grid, and negative sequence current outputted by the current transformer can be eliminated and fluctuation of active power and reactive power can be suppressed when power grid is asymmetric so that advantages of virtual synchronization control can be maintained, stability is great, dynamic power supply without time delay can be spontaneously provided to the power grid, negative sequence current outputted by the current transformer when power grid voltage is asymmetric can be effectively suppressed, and thus safe and stable operation of the current transformer can be guaranteed.

The invention provides a virtual synchronous generator control method based on direct power control when a grid voltage is unbalanced. The virtual synchronous generator control method comprises the steps of: firstly, utilizing ROGI to obtain grid voltage and grid-connected current positive sequence components, and output instantaneous power and average instantaneous power of an inverter; secondly,regarding the average instantaneous power as feedback quantities, and utilizing a traditional virtual synchronization control strategy to obtain reference modulation signals under alpha-beta stationary coordinates; thirdly, adopting a vector proportional integral resonant controller to establish a direct power control loop, regarding the output instantaneous power as feedback quantities, and utilizing direct power control to obtain modification modulation signals through setting different power instruction values separately; and finally, superimposing the reference modulation signals and themodification modulation signals to obtain a final modulation signal, and sending the final modulation signal to an SVPWM modulation module to realize two independent control targets of sinusoidal andbalanced output current and constant output power without fluctuations. The virtual synchronous generator control method reserves the original control features of the VSG, does not require a phase-locked loop, improves the dynamic response capability of the system, and is easy in engineering implementation.

The invention provides a virtual synchronous generator system applied to a photovoltaic power station and a control method, which are simple and effective, and are beneficial to engineering application. The system comprises a photovoltaic inverter, a virtual synchronous machine controller and an energy storage converter DC/AC, wherein the photovoltaic inverter is used for realizing a grid-connected power generation function; the virtual synchronous machine controller is directly connected to a dispatching system; the energy storage converter DC/AC is arranged at an alternating current grid-connected point of the photovoltaic inverter or a direct current collection point of a photovoltaic array, is directly connected to the virtual synchronous machine controller and is used as an executionunit to respond to a power command of the virtual synchronous machine controller; the virtual synchronous machine controller and the energy storage converter DC/AC coordinate to realize the functionsof a virtual synchronous generator of the whole photovoltaic power station, and the photovoltaic inverter still runs in a maximum power point tracking (MPPT) mode to realize the grid-connected power generation function; and the virtual synchronous machine controller and the energy storage converter DC/AC independently construct a high-speed communication network in order to realize high-speed mutual transmission of an active/reactive power command between the virtual synchronous machine controller and the energy storage converter DC/AC.

The invention discloses a virtual synchronous control method and system of a doubly-fed wind generating unit. The method comprises the following steps: performing improved virtual synchronous controlon an acquired stator voltage three-phase alternating-current signal and a stator output current three-phase alternating-current signal of a doubly-fed generator to obtain a stator voltage instructionand a stator virtual synchronous angular frequency instruction of the doubly-fed generator; calculating the collected rotor rotation angular speed of the doubly-fed generator and the stator virtual synchronization angular frequency instruction to obtain a positive sequence slip angle and a negative sequence slip angle of the doubly-fed generator; and performing positive sequence control and negative sequence control based on the positive sequence slip angle, the negative sequence slip angle and the stator voltage instruction, and generating an SVPWM control signal of a doubly-fed generator rotor side converter switching tube. According to the method, the condition that three-phase imbalance occurs in stator end current under the unbalanced power grid voltage is considered, and the three-phase balance of the stator current is realized by adding the negative sequence control loop under the existing virtual synchronous control strategy.

The invention provides an energy storage inverter virtual synchronization method and system for adaptive optimization of power grid strength. The method includes data acquisition, power calculation, output calculation of a virtual speed governor, output calculation of a rotor mechanical equation, power grid impedance calculation, damping value spline interpolation fitting and parameter updating. Improvement is made on the virtual damping link. By introducing differential into the virtual damping link, the virtual damping has no effect on the virtual difference coefficient, and the steady stateerror of the primary frequency modulation of a virtual synchronous machine is eliminated. Meanwhile, a first-order inertia link is introduced to improve the stability of the system. Adaptive parameter optimization control is carried out on the virtual damping link. The impedance of the power grid is detected online by harmonic injection, and the parameters of the damping link are adjusted onlineaccording to the detected impedance of the power grid and an adaptive formula, so that the virtual synchronous machine can have better response characteristic before and after the change of power gridstrength.

The invention discloses a multi-machine parallel stability control and inertia matching method of virtual synchronous machines. In order to solve the problem of large-scale micro power supply access stability control in a new energy power system, a virtual synchronous machine multi-machine parallel connection stability control strategy is studied, and a VSG active-frequency and reactive-voltage controller is built, a simplified virtual inertia simulator is provided, so that a control system does not need to introduce a PLL link, and the influence of phase locking precision on VSG control characteristics is reduced; and establishing an accurate small signal model of a VSG multi-machine parallel operation system, and analyzing the change condition of the characteristic root of the system when parameters such as virtual rotational inertia, a droop coefficient, a line parameter and virtual impedance change, and the influence rule of the change condition on the stability of the small signal. The VSG multi-machine parallel system inertia matching method is provided, the virtual inertia of each VSG is configured according to the inertia matching principle, and it can be guaranteed that each VSG can achieve load distribution according to the capacity proportion in the steady-state and transient-state processes.

The invention provides a control method and system for a modular multilevel flexible direct current converter station. The control method comprises the steps of, obtaining an induced electromotive force and a voltage regulating voltage through three-phase alternating current information obtained by sampling via a virtual synchronous motor controller and a circulating current controller; according to the induced electromotive force and the voltage regulating voltage, obtaining a three-phase voltage reference value; and via modulation of the three-phase voltage reference value by PWM, outputting a switch signal, and achieving control of the modular multilevel converter station. The control method is advantageous in that, according to frequency and voltage variation of an alternating current system, active power and reactive power can be automatically adjusted and output, thereby effectively reducing frequency and voltage fluctuation of the alternating current system.

The invention provides a virtual synchronous control system of a flexible switching device of a power distribution network. The system comprises a data acquisition detection module, a transformation calculation module, a virtual synchronous control module, a current loop control transformation module and a pulse width modulation module, wherein the data acquisition and detection module acquires three-phase voltage and current values and detects phase angles, the transformation calculation module performs coordinate transformation on the three-phase voltage and current values and calculates active power and reactive power, and the virtual synchronous control module receives data information transmitted by the transformation calculation module and outputs a current instruction value; the current loop control transformation module converts the current instruction value, calculates and outputs a fundamental wave voltage instruction value of the converter at the receiving end of the flexible switch, and performs coordinate transformation on the fundamental wave voltage instruction value; and the pulse width modulation module receives the transformed fundamental wave voltage instructionvalue, generates a flexible switch modulation signal through space vector synthesis, improves the power distribution performance, and maintains the safe and stable operation of a power distribution system.

The present invention provides a virtual synchronous generator self-synchronizing control method based on phase difference real-time regulation, belonging to the new energy electric power conversion technology field. The technical steps comprises: calculating voltage phase difference [Delta][Theta] of two sides of a filtering inductor in a corresponding inverter output power; employing a phase-locked loop (PLL) to collect voltage phase information of two sides of the LC filter inductor; calculating phase angle determination signals Judge=[Delta]-[Theta]o; calculating regulation determination signals x=Judge-[Delta][Theta]; editing a conversion switch logic control module; and constructing an operation mode conversion switch logic. The virtual synchronous generator self-synchronizing control method based on the phase difference real-time regulation calculates phase angle difference corresponding to a target power value in real time, rapidly regulates voltage phase angle difference of two sides of the LC filter inductor and realizes self synchronization with the power grid with no need for power grid phase information and the presynchronization link. The virtual synchronous generator self-synchronizing control method based on the phase difference real-time regulation enhances control of the power grid side to a distributed generation to allow the distributed generation to be better serve the power grid. The virtual synchronization generator employs an uniform inner ring control structure when the virtual synchronization generator performs island/grid-connected operation so as to avoid causing stability problem caused by changing of inner ring control.

The invention discloses a VSG virtual inertia and damping cooperative adaptive control system and a method, and the method comprises the steps: building a small signal model containing a wind speed variable according to a doubly-fed fan virtual synchronous control schematic diagram, and employing a fuzzy controller to take the operation wind speed and frequency deviation as the input to determine a virtual inertia coefficient steady-state value; in order to avoid system oscillation instability, determining a damping coefficient steady-state value according to the magnitude relationship between the critical oscillation wind speed and the operation wind speed; and according to the relationship between the frequency deviation and the frequency change rate and the control parameters and the demand change of the frequency modulation process, adjusting the control parameters in a staggered and adaptive manner. According to the VSG virtual inertia and damping cooperative adaptive control system and the method provided by the invention, a doubly-fed fan is facilitated to adapt to different wind speeds, and the frequency modulation effect is improved on the premise of avoiding system oscillation instability.

The invention discloses an energy storage primary frequency modulation virtual synchronous machine parameter analysis method, which applies dynamic virtual parameter VSG control to primary frequency modulation control of a microgrid energy storage grid-connected inverter to improve the primary frequency modulation performance of microgrid energy storage. In order to analyze related parameter values in dynamic virtual parameters, a small signal model analysis method is adopted, a small signal model of a synchronous generator is used for reference, a transfer function between VSG control outputactive power and reference active power is established, and a virtual parameter steady-state value range is obtained. A dynamic virtual parameter VSG control strategy is adopted in a microgrid energystorage primary frequency modulation control system, inertia and damping support can be provided for a power grid, and the primary frequency modulation performance is good.

A loom having a first drive motor (10), which for instance drives a batten (13), and having at least one second drive motor (44), which drives a dobby (46), is provided with a control and regulating device (48), which forms a rotational angle course for a virtual synchronization shaft of the loom and communicates such rotational angle course to respective control and regulating units (49, 51) of each of the drive motors (10, 44), which synchronize the drive motors in at least one angular position relative to the virtual synchronization shaft.

The invention relates to a photovoltaic power station virtual synchronization control method and a control system thereof. The control method comprises the following steps of (1) acquiring photovoltaic power station data; (2) determining primary frequency modulation and inertial element reserve capacity; (3) distributing the reserve capacity; (4) releasing the reserve capacity. According to the technical scheme provided by the invention, a photovoltaic power station has no need to be provided with an extra energy storage device, so that the cost is saved, and the primary frequency modulation retention time of the photovoltaic power station is not restricted by the capacity of the energy storage device. When the photovoltaic power station is provided with enough inverters, only photovoltaic inverters at a hot standby state are need to be switched on and off, an active power output value has no need to be controlled, and the requirement can be met, so that the response time is faster, and the accuracy is high.

The invention discloses a virtual synchronous machine current harmonic suppression method and a virtual synchronous machine control system. On the basis of a traditional voltage control type virtual synchronous machine control algorithm, three-phase current harmonic information is extracted, and the three-phase current harmonic information is fed forward to modulation waves through a proportionaldifferential (PD) regulator, so that the purposes of reducing current harmonics on the alternating current side of the virtual synchronous machine and improving the current quality are achieved. Considering the direct extraction difficulty of the harmonic current, the method employs a generalized quadratic integration (SOGI) method to extract the harmonic current, can effectively inhibit the high-frequency noise of an input current signal, and achieves the quick and accurate extraction of the harmonic current.

The invention provides a signal processing method of a base band receiver of a base station in a digital wireless trunking communication system based on a TDMA (Time Division Multiple Address) technique, comprising the following steps of: filtering; converting single sampling signal flows; demodulating each haploid sampling signal flow; sequentially storing each demodulating code sequence; and then recovering a frame structure of one demodulating code sequence selected from the demodulating code sequences according to synchronously judged outputs. The invention provides a realization method for processing base band signals by accomplishing the final selection of the demodulating code sequences and the recovery of the frame structures according to judgment and presets a frame synchronization time window for the characteristics of a TDMA burst structure to greatly reduce the virtual synchronization probability of frame synchronization. Because the frame synchronization is respectively carried out on the demodulating code sequences, the invention avoids data loss caused by wrong bit synchronization, reduces the synchronization loss probability of the frame synchronization, and improves the sensitivity of the base band receiver.

The invention discloses an inverter reactive power control method based on a virtual synchronization mechanism. At present, the inverter reactive power control method is not accurate in control. Whenthe grid voltage fluctuates slightly, the voltage cannot be controlled without any difference; when the grid voltage drops deeply, and the whole reactive power ability of the inverter cannot be played. The reactive power control method is divided into three phases: when it is monitored that the voltage of the grid-connected point is normal, a reactive power control module aims to control the output reactive power of the inverter; when the voltage drop of the grid-connected point is monitored, the reactive power control module superimposes the voltage of the grid-connected point to reduce the voltage drop; and when it is monitored that the voltage of the grid-connected point is further dropped, an LVRT control module controls the inverter to switch to a low voltage ride-through control modeto perform low voltage ride through. The invention can automatically and flexibly control the output reactive power of the inverter, improve the reactive power utilization rate of the inverter, stabilize the grid-connected point voltage, reduce the grid voltage drop degree, and does not affect the low voltage ride through capability of the inverter.

The invention discloses a method for improving wind power grid-connected primary frequency modulation performance by using adaptive virtual parameters. The method comprises the steps of 1) establishing a wind power primary frequency modulation droop control mathematical model; 2) establishing a simulated synchronous generator mathematical model and a mechanical power mathematical model; 3) designing an adaptive virtual inertia and rotating speed difference control function; 4) designing an adaptive damping coefficient and rotating speed difference control function; 5) applying the adaptive virtual inertia and the adaptive damping coefficient to a virtual synchronous generator control system of the wind power generation grid-connected control system; 6) establishing a wind power generationoutput power mathematical expression; 7) solving a first-order derivative and a second-order derivative of the step 6); 8) obtaining a reference output power expression of a virtual synchronous machine; 9) calculating a characteristic root in the step 8); 10) obtaining the natural oscillation rotating speed and the damping ratio of the system; 11) calculating the rated virtual inertia value range;and 12) setting a rated damping coefficient on the basis of considering the damping coefficient. According to the invention, the wind power grid-connected primary frequency modulation performance isimproved.