1024 results about "Variable frequency control" patented technology

Control methods for resonant converters offer improved performance in resonant converters that operate with a wide input-voltage range or a wide output-voltage range (or both) by substantially reducing the switching-frequency range. Reduction in the switching frequency range is achieved by controlling the output voltage with a combination of variable-frequency control and time-delay control. Variable-frequency control may be used to control the primary switches of an isolated resonant converter, while delay-time control may be used to control secondary-side rectifier switches provided in place of diode rectifiers. The secondary-side control may be implemented by sensing the secondary current or the primary current (or both) and by delaying the turning-off of the corresponding secondary switch with respect to the zero crossings in the secondary current or the primary current.

The invention relates to the technical field of heating and energy conservation and provides a centralized heating public building heat supply energy-saving control method. The method comprises the following steps of: calculating a thermal load required by a public building room in the current time period; calculating water supply quantity required by the public building room in an equivalent area of a building which meets the heating requirement in the current time period; calculating hydraulic power of each pipe section in a pipe network and the total pipe network, performing circulating pump and fan frequency variable control on a water supply main pipe by employing a quantity regulating mode, and performing valve opening control on a water supply branch; and controlling power of a heat source. According to the embodiment, the real-time thermal load required by the building is calculated according to the indoor and outdoor thermal disturbance, the heat waste is reduced, the hydraulic power of the distribution pipe network is reasonably calculated, the pipe section with a proper pipe diameter and a circulating pump with a proper lift are selected according to the calculation, the time and area control and on-demand heating of the thermal load can be realized, and the functions of supervising, calculating and controlling are truly integrated.

The present invention relates to a quality regulation control method of central air-conditioning refrigerating station and its system. It belongs to a method for controlling operation of central air-conditioning refrigerating station and its system. Said system includes internal weather parameter monitoring portion, central air-conditioning system operation parameter monitoring portion, quality regulation control main machine, cold water machine unit control unit for controlling water supply temperature for refrigeration, cooling tower frequency conversion control unit for controlling cooling tower outlet temperature, refrigerating water pump frequency conversion control unit and cooling water pump frequency conversion control unit. Besides, said invention also provides the concrete steps of its quality regulation control method.

The invention provides a frequency converting control method for a refrigerator. The method includes that (1) whether the refrigerator meets a refrigeration condition or not is determined after defrosting of the refrigerator is finished; (2) if the refrigerator meets the refrigeration condition, an environment temperature and a setting temperature are detected, and a preset revolution meter is inquired so as to control the operation of a compressor at a corresponding maximum revolution speed until the refrigeration is completed; (3) when the refrigerator meets the refrigeration condition again, the operation of the compressor is controlled at a corresponding minimum revolution speed; (4) whether the compartment temperature of the refrigerator decreases to a preset temperature or not after preset time is determined; (5) if the compartment temperature of the refrigerator does not decrease to the preset temperature, the revolving speed of the compressor is increased by one level, and the step (4) is returned; and (6) if the compartment temperature of the refrigerator decreases to the preset temperature, the compressor is controlled to continue operating until the refrigeration is finished. According to the frequency converting control method for the refrigerator, the revolving speed of the compressor is continuously adjusted according to the environment temperature, interior temperatures of compartments and the like, so that the frequency conversion is achieved, the cooling speed of the refrigerator is improved, waste of cooling capacity of the compressor is reduced, and the energy consumption is lowered.

Disclosed herein is a charging equipment of variable frequency control for power factor. In addition, the present invention relates to a charging equipment of variable frequency control for power factor including: an AC-DC converter converting AC power into DC power; a DC-DC converter converting DC power output from the power factor calibration circuit into DC power for charging a battery and outputting the converted DC power; and a power factor calibration circuit calibrating power factor by the operation of the switching device and outputting the calibrated power factor; and a power factor calibration circuit controller performing the switching control by varying the frequency of the pulse signal when performing a switching control by modulating a pulse width of a pulse signal on the switching devices of the power factor calibration circuit, thereby making it possible to maintain the power factor even in the light load status.

The invention relates to a high-precision constant-temperature and humidity air conditioner operated in a wide temperature range. The air conditioner comprises an outdoor machine and an indoor machine, wherein the outdoor machine is provided with a condenser and a condensing fan; the indoor machine comprises an evaporator, a thermal recovery exchanger, an electric heater, a humidifier and a blower; and a compressor is formed by connecting in parallel a constant-frequency compressor and a variable-frequency compressor (or a digital scroll compressor) and is arranged in the indoor machine. As the system adopts frequency conversion technology or digital vortex technology and electronic expansion valve technology and unique classified evaporator control, condenser fan frequency-conversion control technology and evaporator frostless structural design, the air condition broadens the use environment range, indoor temperature control environment (between 7 and 30 DEG C) and relative humidity control environment (between 35 and 70 percent RH), can be reliably operated in the outdoor high-temperature environment of 45 DEG C, also improves the controlling precision of indoor temperature and humidity, and is applicable to places with severe requirements on temperature and humidity and large environmental temperature change.

The invention discloses a control device of a frequency convertible refrigerator and a control method thereof. The control device comprises a frequency conversion control panel (3) and an intelligent control panel (2) connected with the frequency conversion control panel (3), wherein, the input end of the intelligent control panel (2) is connected with a temperature sensor (1), and the output end thereof is connected with the input end of the frequency conversion control panel (3); the control device is added with the intelligent control panel (2), so as to add the environmental temperature and the accumulated running time of a compressor into the running control of the refrigerator; according to the temperature of a refrigerating room and a cold preserving room, the cooling rate, the environmental temperature and the accumulated running time of the compressor, the control device of the refrigerator can control the running frequency of the frequency conversion compressor in real time to avoid the compressor from being started and stopped frequently, and the service life of the compressor can be prolonged. The invention improves the refrigerating efficiency of the refrigerator at utmost, and has the advantages of rapid temperature reduction, little energy consumption and easy energy conservation. By adopting the frequency convertible refrigerator, the effects of food cold preserving and fresh-keeping are good.

The invention relates to one voltage decoupling transducer gear vector control method with parameters self-integrating functions, which tests transducer displacement motor stator end voltage, current and rotor speed through outlet voltage test unit, current test unit and speed test unit; according the vector converting the three-phase voltage, current into two-phase rotation coordinates value; for control given value exerting negative feedback adjust and for computation; through decoupling to get control value through inverse vector conversion computation to get three-phase voltage control value for recycle execution.

The invention discloses a method for controlling frequency conversion of a frequency conversion refrigerator. The frequency conversion refrigerator comprises a main control panel, a freezing sensor and a compressor; the method comprises the following steps that: firstly, the compressor starts up; before that, the compressor is inactive, and three reasons cause the shutoff: non-electrification, energy-saving shutoff and shutoff in defrosting stage; therefore, when the compressor starts up, the main control panel judges whether the compressor is started after power off and electrification, after energy-saving shutoff in operation or after defrosting; and according to different situations, the compressor enters different control steps. The frequency conversion technology fully realizes the accurate control of the temperature of the refrigerator, improves the fresh-keeping function of food and greatly reduces the power consumption of the refrigerator; the method also effectively reduces noise; and in particular, the refrigerator can automatically find the lowest rotating speed in operation at nighttime so as to achieve the effect of reducing noise.

In a multi-phase power converter using a phase-locked loop (PLL) arrangement for interleaving of pulse frequency modulated (PFM) pulses of the respective phases, improved transient response, improved stability of high bandwidth output voltage feedback loop, guaranteed stability of the PLL loop and avoidance of jittering and phase cancellation issues are achieved by anchoring the bandwidth at the frequency of peak phase margin. This methodology is applicable to multi-phase power conveners of any number of phases and any known or foreseeable topology for individual phases and is not only applicable to power converters operating under constant on-time control, but is extendable to ramp pulse modulation (RPM) control and hysteresis control. Interleaving of pulses from all phases is simplified through use of phase managers with a reduced number of PLLS using hybrid interleaving arrangements that do not exhibit jittering even when ripple is completely canceled.

The invention discloses a method for enhancing the non-uniform variation grid width of the light load efficiency of an integrated switch DC-DC converter, a Buck-Boost converter in the invention adopts the design of a CSMC 0.5mu m CMOS process library, whole-circuit integration is realized except for a passive filter, the external filter inductance is 2.2mu H, and the filter capacitance is 1mu F. According to the requirements of input voltage and output voltage, the converter can work in three modes: Buck (voltage reducing), Buck-Boost (voltage reducing and boosting) and Boost (voltage boosting), the range of the input voltage is 2.5V-4.2V, the range of the output voltage is 1.5V-5V, and the working frequency is 5MHz. A non-uniform grid width modulation method is adopted in the whole load current range of 10mA-650mA. When the converter works at high frequency of 5MHz, the efficiencies of medium load and heavy load keep above 90 percent all the time, and the efficiency of light load (10mA) can reach above 80 percent. As the grid width of a switching tube is only changed and a control link of the working efficiency of an extra switching tube is not adopted, negative effects caused by frequency conversion control are eliminated fundamentally.

The invention provides a fish swimming capability measuring method and a submerged open-type measuring device. The method includes 1, making preparation before experiments; 2, testing and correcting systems; 3, testing swimming capabilities of fishes; 4, collecting experiment data; and 5, maintaining and cleaning the systems. A water outlet tube with a water level adjusting device is mounted at the bottom of a water tank of the submerged open-type testing device. A support, an experiment table base, a stabilizing cove and a testing tube are mounted in the water tank. A water current creating system formed by a motor, a water inlet hole and a vane wheel is arranged at one end of the testing tube. The water current creating system and a test area with an inspection window are respectively connected with two ends of a rectifying device. The test area with the inspection window is connected with a flow rate test area. A current meter is mounted in the flow rate test area connected with a water level control area. A water current flow rate monitor, a frequency conversion controller and a water quality monitor are mounted on a control panel. A water inlet tube is mounted at one end of the upper portion of the water tank.

The invention relates to a mobile phone remote intelligent irrigation system, which is designed so as to solve the technical problem that the existing similar intelligent irrigation system has a poor control mode and a poor structural design and lacks of smart mobile phone remote control. The intelligent irrigation system comprises a network data processor and a smart mobile phone; APP (application) intelligent irrigation software is installed in the smart mobile phone; an electromagnetic valve controller is a wireless electromagnetic valve controller; a water flow touch sensor is arranged in a water flow switch valve; the electromagnetic valve controller automatically starts to work according to setting, and the work is controlled remotely through the APP intelligent irrigation software in the smart mobile phone, and a signal that water flows is sensed by the water flow sensor, and a water pump is started to work; the work of the electromagnetic valve controller is controlled through the mode, and after sensing a signal that the water hardly flows, the water flow sensor automatically turns off, and the water pump automatically stops working; therefore the goal that the work of an intelligent frequency conversion control cabinet at a head part is intelligently controlled and triggered through the electromagnetic valve controller at a tail end is achieved through the process.

The invention discloses a cooperative control method for a wind power plant and a flexible direct current transmission system for improving an inertial level of a power system. The control method is used for simulating the inertia of a synchronous generator by virtue of a direct-current capacitor and the kinetic energy of a DFIG (Doubly Fed Induction Generator) rotor. The cooperative control method comprises the steps that a GSVSC (Grid-Side Voltage Source Converter) enables the direct-current capacitor to correspondingly absorb or release energy through the slip frequency control on a direct-current voltage under the disturbance of a power grid; then, a WFVSC (Wind Field Voltage Source Converter) converts the changed direct-current voltage into a wind field side alternating-current system change frequency signal through frequency conversion control after feeling the fluctuation of the direct-current voltage, so that a maritime alternating-current system and a shore alternating-current system are artificially coupled, and the communication between convertor stations at two ends is omitted; finally, a power instruction value is adjusted by a DFIG power controller in order to respond to the frequency change of the WFVSC, and the rotating speed of the rotor is also correspondingly changed. Through a series of cooperative control, a maritime wind field takes part in the frequency adjustment of a power system so as to play an important significance to the introduction of a large maritime wind field.

The invention discloses a drying line of pulp moulding that is based on a frequency-varying speed regulation technique, and a production technique of the drying line, and is applied into a belt drying line with convectional hot air and used for designing a set of automatic controlling systems with optimized efficiency; the invention implements the modeling of complex objects according to the drying property of pulp moulding and different sizes and weights of wet ground papers, adopts a process control technique, the alternate-current frequency-varying speed regulation technique and a modern detecting technique, realizes stepless control of frequency-varying speed regulation of a circulating fan, an electric air door, a dehumidifying fan, a drive motor of conveying chains according to temperature and humidity signal that are detected on the spot, reasonably adjusts the running speed of a conveying belt inside a parching channel, the working temperature of a desiccator in each segment, and the blast volume of hot air and the discharge of water vapor, etc., and forms a reasonable drying curve, thus reducing product deformation to the utmost degree, saving the loss of electricity energy and heat energy to the utmost extent, accelerating parching speed, increasing the yield of the parching production line, and realizing optimal control.

The invention discloses a fan frequency conversion control system and method for air pressure dynamic balance of a mine stope. The fan frequency conversion control system comprises an alternating-current frequency converter console, a counter rotating axial flow fan, carbon monoxide sensors, air speed sensors, a differential pressure sensor, an intrinsically safe power supply, and an intrinsically safe junction box, wherein the alternating-current frequency converter console has two sets of alternating-current frequency converters; the frequency converters, the counter rotating axial flow fanand the intrinsically safe power supply are arranged in an inlet alley; the air speed sensor 1 is arranged in the air inlet alley; the differential pressure sensor and the air speed sensor 2 are arranged in an air return alley; and the two carbon monoxide sensors are arranged in an air return corner region. Data such as carbon monoxide content, air quantity, air pressure and the like is real-timemonitored, ventilation quantity of a mining working surface is automatically controlled, so that the mining working surface and the environment air pressure automatically achieve dynamic balance, thus the safety production of the mining working surface is achieved when a plurality layers of mine goafs are communicated with each other, the working efficiency, the precision degree and the safety degree are improved; the fan is driven by frequency conversion, so that the fan has energy-saving effect, broad adaptability, social benefits and economic benefits.

The invention relates to an asymmetrical radial forging highly efficient precision feeder which comprises at least the drive mechanism, radial forging feeding and stroke micro tuning structure and bar material fixture device, with the radial feeding device using hammer cycloid design, cam using cylinder roller device, without impact and stable movement. The turbine worm stroke adjusting device uses separate turbine gear structure, and be able to improve stroke adjustment structure' kinematic behavior. Through servo generator variable-frequency control function, it can make precise blank with various material and different size.

The invention provides a household air-conditioning intelligent temperature control system on the basis of human behaviour characteristic, comprising a compressor which is provided with a wind conveying port, and a temperature controller and a frequency conversion controller which are connected with the compressor; the temperature controller and the frequency conversion controller are respectively connected with a behaviour characteristic intelligent sensor which comprises a motion detector, a signal controller and a micro-control unit; the output terminal of the micro-control unit is connected with the temperature controller and the frequency conversion controller; furthermore, the input terminal of the signal amplifier is also connected with a temperature detector. The invention provides the control system based on the behaviour control on human-machine engineering science, uses the directional wind blowing to lead the human to get rid of the shortage of the fixed wind blowing of the existing air conditioning on the basis of the comfortableness of the human, improves the energy-saving efficiency of the air-conditioning, detects the human behaviour char by the behaviour intelligent sensor, realizes the automatic turn-on/off, controls the refrigeration quantity and heating quantity by detecting the human behaviour characteristic, realizes the most economical refrigeration and heating according to the requirement and realizes the object of energy-saving.

The invention discloses a three-phase three-level LLC resonance direct current converter which comprises an input voltage partial capacitor unit, a half-bridge three-level unit, a full-bridge unit, a resonance network, a three-phase isolation transformer and a rectification and filter circuit. The input voltage partial capacitor unit, the half-bridge three-level unit, the full-bridge unit, the resonance network, the three-phase isolation transformer and the rectification and filter circuit are sequentially connected. According to the three-phase three-level LLC resonance direct current converter, as the resonance network is additionally arranged, the soft-switching function of the three-phase three-level LLC resonance direct current converter is achieved, and switching losses are reduced. The invention further discloses a control method of the three-phase three-level LLC resonance direct current converter. Frequency converting control is adopted to the control method, ZVS of a switching tube and ZCS of an auxiliary edge rectifier tube can be achieved within a wide voltage range and a wide load range, and the three-phase three-level LLC resonance direct current converter has the high efficiency and the high power density.

The invention relates to a method for controlling the temperature of a mechanical refrigerator in a frequency conversion mode. The method comprises the following steps of: (a), a control chip of the refrigerator partitions environment temperature and sets corresponding standard temperature; (b), the control chip of the refrigerator calculates temperature difference between the temperature of a refrigerating chamber and the standard temperature of a temperature interval in which the current environment temperature is positioned; (c), the control chip drives a compressor of the refrigerator to refrigerate the refrigerating chamber within preset time according to the temperature difference, and calculates the temperature difference between the environment temperature and the current temperature of the refrigerating chamber; (d), if the temperature difference is greater than corresponding preset temperature, the control chip repeats the step (c), and stops the running of the compressor until the temperature difference is smaller than or equal to the corresponding preset temperature; and (e), the control chip starts to execute from the step (b) at regular time. By the method, the mechanical refrigerator can be subjected to frequency conversion control according to the current temperature and has the effects of energy conservation, low noise, quick freezing and the like; and the rotation speed of the compressor of the refrigerator can be adjusted at any time, the temperature of the refrigerator can be controlled accurately, and the frequent starting and stopping of the compressor can be avoided.

The invention discloses a control method and device of an electronic expansion valve. Due to the facts that the opening degree of the electronic expansion valve can be adjusted only by obtaining the operating frequency and exhaust temperature of a compressor, and the operating frequency of the compressor can be directly obtained from a variable frequency control system of the compressor, so that only a temperature sensor for sensing and obtaining the exhaust temperature of the compressor is needed, and the number of temperature sensors in use is decreased. Normal operation of the electronic expansion valve can be ensured as long as the temperature sensor for sensing and obtaining the exhaust temperature of the compressor does not break down, so that reliability of the electronic expansion valve is improved, and meanwhile the cost for the temperature sensor is reduced. By means of the control method or device of the electronic expansion valve, a variable-frequency air conditioner system or a variable-frequency water heating pump system or the like operates more safely and stably, and the required cost for the temperature sensor is reduced.

The invention discloses an energy-saving operation control method for an inverter air conditioner. The energy-saving operation control method for the inverter air conditioner comprises the following steps of establishing energy-saving operation parameter libraries which correspond to different working conditions and comprise energy-saving working frequency; enabling the inverter air conditioner to work in the inverter control mode; detecting the indoor temperature T1i and the outdoor temperature T4i; judging the degree of closeness of the indoor temperature T1i and the set temperature Ts; and when the degree of closeness achieves a preset energy-saving control preset value, enabling the inverter air conditioner to invoke a corresponding energy-saving operation parameter to work according to the working condition. Because the energy-saving operation control method for the inverter air conditioner, which is disclosed by the invention, is characterized in that the corresponding energy-saving operation parameter is invoked for working when the degree of closeness achieves the preset energy-saving control preset value, the inverter air conditioner is prevented from working under the low-frequency condition so as to improve the total energy efficiency of the inverter air conditioner, and the energy saving effect is achieved.

An integrated fan drive system for air-cooled heat exchangers. The integrated fan drive system has a high-torque, low speed permanent magnet motor having a rotatable shaft, a fan that is directly connected to the rotatable shaft, and a variable frequency drive device in electrical signal communication with the permanent magnet motor to control the rotational speed of the permanent magnet motor. The high-torque, permanent magnet motor comprises no more than two bearings in operative association with the shaft. The variable frequency drive device has a variable frequency controller that has an input for receiving AC power and an output for providing electrical signals that control the operational speed of high-torque, permanent magnet motor. The variable frequency drive device also includes a user interface in electronic data signal communication with the variable frequency controller to allow a user to input motor speed control data. Other embodiments of the invention are described herein.

The invention discloses a wide gain control method of a variable topology LLC resonant converter. The wide gain control method is applied to a variable topology LLC resonant converter composed of an inverter circuit, an LLC resonant cavity, a transformer and a secondary rectifier and filter output circuit. An input voltage range is divided into a low voltage section, a medium voltage section and ahigh voltage section which correspond to three different modes; the variable topology LLC resonant converter adopts variable-frequency PFM control of an FBLLC structure in the low-voltage section ofthe input voltage, and the output voltage gain is changed by changing the switching frequency; the variable topology LLC resonant converter adopts fixed-frequency PWM control of an FBLLC structure inthe medium voltage section of the input voltage, and the output voltage gain is changed by changing the duty ratio of an inverter circuit switching tube (S1); and the variable topology LLC resonant converter adopts fixed-frequency PWM control of an HBLLC structure in the high voltage section of the input voltage, and the output voltage gain is changed by changing the duty ratio of the inverter circuit switching tube (S1).

The invention discloses a frequency converting control method and system of a condensate pump of a condensed steam generator set. When a frequency converter is in a liquid control mode, the water level of a deaerator is controlled by the frequency converter and a water adjusting valve on the deaerator, and the frequency converter controls the water level of the deaerator by adjusting the rotating speed. A water feeding main adjusting valve on the deaerator is maintained at certain aperture according to the load of a machine unit; and under the same load, when the machine unit is in a load up stage, the aperture of the water feeding main adjusting valve is maintained to be small, and when the machine unit is in a load down stage, the aperture of the water feeding main adjusting valve is maintained to be large. Simultaneously certain load space can be generated by control of two clamped curves during load up and load down, and frequent aperture changing of the water feeding adjusting valve caused by small load fluctuation can be avoided. The rotating speed of the frequency converter can be lower, the current is small, the output frequency of the frequency converter is in the adjustable and economical range, and energy consumption of the frequency converter is reduced.

The invention discloses a control method of an inverter compressor of a heat pump clothing dryer and the heat pump clothing dryer. The heat pump clothing dryer comprises a heat pump clothing drying system comprising a heat pump module comprising the inverter compressor, a condenser, a throttling device and an evaporator, or further comprises a fan used for decreasing the temperature of the surface of the inverter compressor to adjust the load. In the clothing drying process, the operating frequency of the inverter compressor is controlled segmentally; the method includes compressor frequency rising control, compressor frequency inverting control and clothing drying finish determination. If a set clothing drying condition is not achieved after detection, the processes of compressor frequency inverting control and clothing drying finish determination are repeated circularly. The compressor frequency rising control means controlling the inverter compressor to rise the frequency to an ultimate frequency and operate stably; the compressor frequency inverting control means adjusting the operating frequency of the inverter compressor segmentally corresponding to the detection temperature. the control method and the heat pump clothing method have the advantages that drying efficiency is improved, operating efficiency of the inverter compressor is optimized, and service life of the inverter compressor is prolonged.

The invention discloses a method for controlling an inverter air conditioner, which is characterized in that an indoor target temperature and a working frequency of a compressor are preset; after a control component of the inverter air conditioner receives the indoor target temperature and the working frequency set by a user and before the indoor temperature reaches the indoor target temperature, the working frequency of the compressor adopts a fixed frequency mode to work; after the indoor temperature reaches the indoor target temperature, the working frequency of the compressor adopts a variable frequency control mode to work; and the working frequency of the compressor is not higher than the working frequency set by the user. The user sets the indoor target temperature and the working frequency of the compressor through a remote controller key or a control key on an indoor unit of the inverter air conditioner. The working frequency of the compressor has more than two set values which are uniformly distributed or not uniformly distributed. The method has the characteristics of flexible operation, good comfort, relatively constant temperature, small fluctuation, comfortable use, low energy consumption and broad application range.

The invention discloses a high-cost performance system for controlling combustion redundancy of a coal-fired heat transfer material heater, which relates to the technical field of DCS industrial control systems, in particular to the system for controlling the combustion redundancy of the coal-fired heat transfer material heater of a large-scale chain coal bed. The system comprises a PLC, an operation management system, a frequency conversion control technical system and a conventional electric control system. The combustion control and the heating circulation control of the control system areensured by two sets of control systems and bumpless control right transfer is realized, and the two sets of systems have low cost and high cost performance, and ensure the safety and the reliability of heat medium heater control system; a humanized operator interface is adopted and an expert diagnostic system is provided; and control software is designed with a standardized, functionalized and modularized structure and has easily expanded functions, add programs and adjust parameters. The system ensures the safe production of a heat medium heater, heat medium temperature control accuracy and the probability of improving the combustion efficiency of fire coal, and has good control effect and relatively lower running cost.

The invention provides a control method and a device for connecting wind power to a flexible HVDC transmission system. Firstly, the actual frequency of an AC grid at a receiving end, the actual frequency of an AC bus bar at a wind farm side, the actual voltage at a DC side of a receiving end converter station are obtained, and the reference voltage at the DC side of the receiving end converter station is determined. Then, the voltage of DC line, the frequency of AC bus and the active power of wind farm are controlled separately, which has high reliability, short frequency modulation response time and good frequency modulation effect. Virtual synchronous machine droop control is adopted in the sending-end converter station, which improves the response speed of frequency regulation and shortens the time of frequency modulation. The frequency of the alternating current bus on the wind farm side is controlled by fixed frequency control or frequency conversion control, The active power of wind farm is controlled by virtual inertia, which makes the increased or decreased power released or supplemented in time when the flexible HVDC system provides frequency modulation for the receiving AC network, and reduces the risk of HVDC line voltage exceeding the limit, and greatly improves the reliability of HVDC system.

A device for realizing powder high-density vibration compression moulding comprises a base 1, a mechanical vibration device 2, a clamp 3, a mould component 4, a hydraulic system 5, an ultrasound vibration device 6, a bearing seat 7, a data acquisition system 8, a motor 9 and a frequency adjustment control system 10. The device has the advantages that three-dimensional mechanical vibration with accurate and controllable amplitude and frequency, two-way axial compression with different impact speed and pressure, and ultrasonic vibration with adjustable frequency are used for cold-state moulding, organic bonding of various links from initial powder filling in a mould to powder transmission then to tightening under the vibration condition is comprehensively considered, and accordingly a high-performance densification compact with uniformly distributed inner density and stress is obtained, quality and performance of powder metallurgy parts and ceramic products are enhanced, and production cost is lowered. The whole process is controlled by a PLC (programmable logic controller), visualization of compact macroscopic performance change during powder tightening can be achieved by data acquisition and conversion, and process optimization and production automation are convenient to realize.