74 results about "Ac frequency" patented technology

In an example, an electrochemical monitoring system for determining one or more parameters of interest of an electrochemical cell can include measurement circuitry, which can be configured to obtain, for a plurality of specified alternating current (AC) frequencies: (1) a first AC voltage measurement across nodes which can be coupleable to the electrochemical cell, and (2) a second AC voltage measurement across a sensing impedance which can be elicited in response to the AC stimulus. The sensing impedance can be coupled in series with the electrochemical cell. The electrochemical monitoring system can also include a controller circuit, which can be configured to jointly estimate model parameters corresponding to an equivalent circuit model (ECM) of a combination of the electrochemical cell and the sensing impedance, such as using the first and second AC voltage measurements for the plurality of specified AC frequencies.

Provided is a battery module and battery rack having enhanced fire safety features. The battery module includes a swelling / pressure sensor that detects swelling of a battery cell. An output signal of the sensor is used to halt operation of a battery rack / battery system containing the battery module and prevent charging and discharging of the battery module. In an embodiment, the battery module uses an AC-to-AC power supply to provide AC frequency power for balancing battery cells of the battery module. In an embodiment, the battery rack includes an internal water fire suppression system that provides battery cooling in the event of a battery cell fire to prevent the spread and / or reigniting of the fire.

A measuring system includes a vibration-type transducer and electrically coupled measuring system electronics unit for controlling the transducer and evaluating vibration measurement signals provided by the transducer. The exciter arrangement has a vibration exciter which is positioned and aligned such that a drive offset is no more than 0.5% of the tube length. The measuring system electronics are configured to supply electrical power to the vibration exciter by means of an electrical drive signal having a temporally variable electrical current and to provide the drive signal at least intermittently with a sinusoidal second useful current having a second AC frequency, in order to monitor a quality of the measured substance based upon a corresponding second useful signal component of at least one of the vibration measurement signals.

This application discloses an islanding detection method and apparatus. The method includes: monitoring the AC frequency of an inverter, which fluctuates within a preset range when the inverter is in normal control mode; when the instantaneous offset value of the AC frequency exceeds the preset range, the frequency before the instantaneous offset is taken as the first frequency; if the frequency in the first frequency data within a first preset time range is only greater than or only less than the first frequency, the AC frequency at the end of the first preset time is taken as the second frequency; continuously adjusting the output power of the inverter based on the change of the current AC frequency; and when the frequency in the second frequency data within a second preset time range is only greater than or only less than the second frequency, the inverter can be promptly instructed to report the islanding status. By using a two-step judgment method, the method distinguishes between islanding and normal load switching, avoiding the inverter actively adjusting the system voltage or frequency and improving the accuracy of islanding detection.

This application provides a control method for an energy storage system, comprising: determining the state parameters corresponding to each individual battery cell; determining a multi-dimensional control factor corresponding to each individual battery cell based on different state dimensions indicated by the state parameters at preset calculation cycles; sorting multiple individual batteries cells according to the charge / discharge state of the energy storage system and the multi-dimensional control factor; determining the output demand voltage corresponding to the energy storage system based on the peak reference voltage and AC frequency corresponding to the energy storage system; and controlling the access state of each individual battery cell in the next AC cycle by applying the nearest level approximation method based on the sorting result, the output demand voltage, and the maximum supply voltage corresponding to each individual battery cell in the next AC cycle. This application controls the energy storage units connected to the charge / discharge circuit of the energy storage system and their access time through multi-dimensional control factors calculated from multiple dimensions, thereby achieving full utilization of the energy of the energy storage units.

The application discloses a kind of water pump AC frequency converter energy-saving optimization control system, it is related to water pump energy-saving control technical field;Including: database, identification perception module, operation optimization module and control feedback module.Database acquires water pump operating parameter, and based on this and calculates lift, water pump efficiency and load rate;Identification perception module is based on lift, water pump efficiency and load rate deviation analysis constructs fusion deviation curve, and based on this obtains judging index to analyze curve area, to identify inefficient operation scene;Operation optimization module determines target flow, target lift according to end water demand and pipe network pressure demand, and obtains target frequency in combination with water pump similarity law and efficiency, lift deviation correction;Control feedback module implements frequency conversion control according to target operating parameter, and real-time feedback and secondary correction are carried out to execution result, form closed-loop optimization control, improve energy efficiency identification ability under low load condition, reduce water pump operating energy consumption.

The utility model relates to electrical engineering and can be used to protect electromagnetic voltage transformers from ferroresonant oscillations occurring in voltage transformers in distribution networks with a voltage class of 6-10 kV, alternating current with a frequency of 50 Hz with an isolated neutral.In a device for protecting voltage transformers from ferroresonance phenomena, designed with the possibility of connecting to two terminals of auxiliary secondary windings of three single-phase transformers connected in an open-delta circuit, containing a series-connected RTS thermistor, a damping resistor and an electronic switching circuit with a threshold switching characteristic, which includes a switching element in the form of a triac, the control electrode of which is connected to a control circuit including a dinistor, two resistors and a capacitor, the control electrode of the triac is connected to the control circuit through a normally closed controlled key, the RTS thermistor is equipped with a temperature sensor connected to the controlled key, and the dinistor is selected to be symmetrical.Technical result: increasing the effective operating time of a device for protecting voltage transformers from ferroresonance phenomena in the presence of modes in the network accompanied by prolonged exposure to single-phase short circuits to ground by ensuring restoration of the original operating mode. 2 fig.

The invention discloses a servo system for a ship towing winch and a control method of the servo system. The servo system comprises a rectifying circuit, a three-phase full-bridge circuit, a braking circuit, a DSP control circuit, an output capacitor C, a brake control circuit and a rotary transformer decoding circuit. According to the servo driver, full electrification of releasing, recycling and zero-speed working condition maintaining of the ship winch is achieved, compared with a hydraulic driving device of a traditional winch, the defects that a hydraulic system is complex in structure, large in size and difficult to maintain are overcome, and an electric driving system is high in control precision, simpler to achieve and more convenient to operate. Compared with conventional alternating-current variable-frequency electric drive of an existing winch, servo drive is more suitable for the low-speed large-torque working condition, efficiency is higher, and cooperation of a PLC is not needed. Compared with a traditional speed loop and current loop control method, the control method for four-quadrant operation of the servo driver enables the winch to have an energy consumption braking function, and meanwhile the safety of the towing winch under the extreme working condition is guaranteed by being matched with a brake of the motor.

The invention discloses a frequency sensing and rapid supporting method for a wind power multi-terminal flexible direct current sending-out system. The method comprises the following steps that a fan side VSC control framework and a control framework and control rules of an alternating current power grid side flexible direct current converter station are constructed; an alternating-current power grid frequency-direct-current voltage-wind power plant power mapping model is constructed based on the characteristics of the converter station, and accurate sensing of the alternating-current frequency under the condition of no rapid communication is achieved; based on the mapping model, determining an improved frequency support strategy design scheme of the large-scale wind power multi-terminal flexible direct current sending-out system; and setting parameter constraint conditions for key parameters of the strategy. Accurate sensing of the alternating current frequency can be achieved under the condition of no rapid communication, the lowest frequency point after power disturbance is effectively raised, the frequency change rate is reduced, secondary falling of the frequency is avoided, meanwhile, different topological structures and line fault scenes are adapted, and safe and stable operation of an electric power system is guaranteed.

The utility model discloses a kind of amorphous alloy three-dimensional roll iron core annealing monitoring models, comprising: support, amorphous alloy three-dimensional roll iron core, high voltage coil, low voltage coil, insulating iron hoop, ac frequency modulation power supply, magnetized busbar and power analyzer, high voltage coil and low voltage coil are set in the upper yoke portion of amorphous alloy three-dimensional roll iron core;Insulating iron hoop is used to fix amorphous alloy three-dimensional roll iron core;Magnetized busbar is supported by insulating support plate and placed in the inner frame of the iron core;Ac frequency modulation power supply is electrically connected with high voltage coil;Voltage clamp and current clamp are electrically connected with low voltage coil respectively;Power analyzer is electrically connected with the voltage clamp and current clamp.

The application discloses a pumped storage full-power frequency converter power unit variable frequency control method and device, N power units are cascaded at an AC end to form a test valve, and M power units are cascaded at the AC end to form a test valve; the method is used for controlling the test valve to output several AC frequency target values, and the method comprises the following steps: pre-charging DC capacitors in the test valve and the test valve to target values; determining corresponding output current / power target values according to the AC frequency target values to be output; controlling the turn-on and turn-off time of the turn-off semiconductor of each power unit in the test valve and the test valve, so that the actual output current / power of the test valve is the output current / power target value, and the actual output frequency of the test valve is the AC frequency target value. The application can simulate the continuous speed regulation operation condition of the pumped storage full-power frequency converter power unit on the pumped storage unit.

The invention belongs to the technical field of power system synchronization, and particularly relates to a three-phase phase-locked loop control method and device. The method comprises the following steps: acquiring a q-axis power grid voltage sampling value of a three-phase power grid voltage sampling value under a two-phase rotating coordinate system; inputting the q-axis power grid voltage sampling value into a complex coefficient filtering sliding mode observer, extracting alternating current frequency multiplication disturbance brought by the distorted power grid voltage, and obtaining a q-axis voltage estimated value, a direct current estimated value in the alternating current frequency multiplication disturbance and a total alternating current estimated value in the alternating current frequency multiplication disturbance; the complex coefficient filtering sliding-mode observer is obtained by connecting a complex number filtering item of a complex coefficient filter in parallel in the sliding-mode observer; and calculating a phase angle estimation value of the three-phase phase-locked loop after feedback compensation based on the q-axis voltage estimation value, the direct current quantity estimation value in the alternating current frequency multiplication disturbance, the total alternating current quantity estimation value in the alternating current frequency multiplication disturbance and the power grid phase voltage amplitude. The control efficiency and accuracy of the phase-locked loop are improved, and the method has good stability and robustness.

The invention provides a wind power plant-multi-terminal flexible direct current system grid-source frequency mirror image control method, which comprises the following steps: based on a wind power plant-multi-terminal flexible direct current grid-connected system, adopting a grid frequency-active power-direct current voltage dual droop control strategy in converter stations, and analyzing power distribution characteristics and direct current voltage control characteristics of each converter station; deducing a design principle of a control coefficient; in a wind field-multi-terminal flexible direct-current grid-connected system, a positive and negative pole differential mode frequency transfer method is utilized to map power grid frequency change from direct-current voltage; based on a double droop control strategy of a wind field-multi-terminal flexible direct current grid-connected system and mapping of power grid frequency, a wind power plant side current converter obtains power grid frequency change by detecting direct current voltage and reflects the power grid frequency change on alternating current frequency of a wind power plant. The method solves the problems that when frequency mirroring from an onshore alternating current main network to an offshore alternating current power grid is achieved through droop control, a current converter is prone to overload, the mirroring precision is poor, and the frequency mirroring is prone to being disturbed by power fluctuation.

The invention discloses a control method and system of a ship alternating current and direct current hybrid power system based on a hybrid margin. The method comprises the following steps: collecting a direct current voltage of a direct current sub micro-grid and an alternating current frequency of an alternating current sub micro-grid in real time; for each energy storage unit in the DC sub-microgrid, adjusting the input and output power of the energy storage unit in different modes based on the operation margin corresponding to the state of charge; for each power supply in the AC sub-microgrid, adjusting the power supply output active power in different modes based on the power supply operation margin corresponding to the operation parameter; carrying out normalization processing on the direct-current voltage and the alternating-current frequency and calculating deviation values of the direct-current voltage and the alternating-current frequency; if the two deviation values are both in the margin range, the standby state of the interconnection converter is maintained, and the energy storage unit and the power supply autonomously complete power balance through a self droop control strategy; and if one of the two deviation values exceeds the margin range, power mutual assistance and distribution are performed on the DC sub-microgrid and the AC sub-microgrid through the interconnection converter based on a double-droop control strategy.

A resonant converter has a transformer having a primary winding and a secondary winding magnetically coupled to the primary winding via a transformer core, a controllable primary-side switching element electrically coupled to the primary winding via a primary-side resonant circuit, and a controllable secondary-side switching element electrically coupled to the secondary winding, the primary-side switching element is used for connecting the primary winding with a primary-side alternating current voltage with a predeterminable alternating current frequency, and the secondary-side switching element is used for guiding a secondary-side alternating current with an alternating current frequency through the secondary winding. The transformer has, on the secondary side, a separate secondary-side synchronous winding magnetically coupled to the primary winding for generating a secondary-side synchronous signal, and has a control device. The control device is designed to receive the secondary-side synchronization signal, to detect a zero value of the secondary-side AC current on the basis of the secondary-side synchronization signal, and to determine a time difference between a sign change of the primary-side AC voltage and reaching the zero value.

The application provides a sparse modular multilevel matrix converter topology, a design method and a control method, and the topology has three-phase symmetry on the input and output sides. The design method is for the purpose of reserving the functions and performance of a conventional M3C and reducing the cost, and comprises the following steps: setting the input side and the output side AC frequency of the matrix converter as an integer frequency division relationship; improving the utilization rate of the DC voltage and reducing the modulation amplitude of each bridge arm through a two-side phase coordination control method; and determining the number of bridge arm sub-modules to be less than the number of bridge arm sub-modules of the conventional M3C based on the modulation amplitude. Through the phase coordination technology, the number of bridge arm sub-modules is reduced on the basis of reserving the functions and performance of the conventional M3C, so that the cost is reduced, and the operation efficiency is improved to a certain extent.

The invention provides an off-grid hydrogen production system comprehensive efficiency optimization method based on alternating current frequency modulation, and belongs to the technical field of new energy hydrogen production. Comprising the following steps: establishing an electrolytic cell performance evaluation system; obtaining a performance index weight; dividing a working interval by an improved TOPSIS method; aC frequency information transmission and electrolytic cell power adaptive control are carried out. Compared with the prior art, the system state information is transmitted through the frequency signals, communication does not need to be depended on, and the problem that communication faults affect the system stability is solved. In addition, a hydrogen production power self-adaptive control strategy is designed in combination with the working interval of the electrolytic cell, the influence of the working state of the electrolytic cell is considered, and the method is suitable for various weather conditions.

The application discloses a DC link capacitor configuration method for a ship hybrid power station energy storage system, and the method comprises the following steps: constructing a ship hybrid power station energy storage system model containing an energy storage frequency modulation system and an AC power supply system, setting an inertia time constant and a damping coefficient of a VSG, and calculating an inertia frequency modulation required power; in an online stage, according to an actually measured AC frequency fluctuation and an energy storage output power considering a power ramping constraint, a DC link capacitor is calculated with the target of maintaining a DC voltage fluctuation in a safe range under a maximum frequency step fluctuation. The application quantitatively analyzes the frequency modulation required power / energy, the battery ramping power / energy and the link capacitor power / energy, uses the DC link capacitor energy as a fast frequency modulation resource in the energy storage inertia frequency modulation system, and makes up the difference between the energy storage system ramping power output and the VSG inertia frequency modulation power requirement. According to the power and energy conservation, the DC link capacitor size under the best frequency modulation power requirement of the ship comprehensive power system is obtained, the method is suitable for different types of energy storage systems and system frequency modulation requirements under different disturbances, and the inertia frequency modulation capability and the stable operation capability of the system under multiple working conditions are effectively improved.

This invention proposes a hybrid MMC fault clearing control method and apparatus with a low full-bridge ratio. The invention includes: when a DC fault is detected, the DC controller of the sending-end converter switches to fault mode, generates a fault DC internal potential through proportional control, and applies negative limiting to cut off the fault current; the AC controller switches to fault mode, adjusts the energy storage reference value of the full-bridge submodule, and generates an AC frequency deviation; the grid-side converter of the wind turbine sets the AC power reference value to zero, generates a wind turbine frequency deviation based on the power deviation, and updates the voltage phase; after the fault current returns to zero, each controller switches back to normal mode to restore power transmission. This method can quickly cut off the fault current, stabilize wind turbine operation, and ensure system fault ride-through and reliable recovery.

The invention relates to the technical field of converters, in particular to a bipolar AC-AC frequency converter and a control method thereof.The power frequency side of an AC-AC frequency converter body is connected to a power frequency power grid, the low frequency side of the AC-AC frequency converter body is connected to a low frequency power grid through a three-phase three-winding bipolar transformer, an A-B-C three-phase structure is adopted, and each phase comprises an upper bridge arm and a lower bridge arm; each bridge arm is formed by connecting n full-bridge sub-modules and a bridge arm inductor in series, but the inductance values of the three-phase bridge arm inductors are different. The phase three-winding bipolar transformer comprises a positive pole transformer and a negative pole transformer, the phase difference of corresponding port voltages of the positive pole transformer and the negative pole transformer is 180 degrees, and a symmetrical bipolar structure is formed; and neutral points of the two are interconnected to form a bipolar output loop. The unbalanced capacitor voltage caused by the inductance difference of the three-phase bridge arm is accurately adjusted, so that the working voltage of each module tends to be consistent, and the balanced operation of the system is ensured. Harmonic generation and electric energy fluctuation possibly caused by voltage imbalance are reduced, the electric energy quality is improved, and stable power supply of a power system is guaranteed.

This invention proposes a DC fault ride-through method and apparatus for a new energy islanded DC transmission system. The invention includes: in the event of a DC fault, controlling the receiving-end converter station to enter a zero DC current mode and the sending-end converter station to enter a zero DC voltage mode; the generation unit identifies the fault based on the AC frequency, switches to a load shedding mode, and engages an unloading circuit to dissipate surplus power; when the capacitor voltage of the sending-end converter station submodule drops to a preset threshold, it switches to the zero DC current mode, outputting a negative voltage to quickly suppress the DC current; after the fault is cleared and power is balanced, the converter station resumes normal operation, the generation unit ramps up power recovery, and unloading stops. This invention can quickly suppress faults, stabilize system operation, and achieve smooth recovery after a fault.

This invention provides a fault-passing method and system for an AC-AC frequency converter. The method includes: detecting the operating status of the main power modules on each bridge arm; obtaining the number of faulty main power modules on each bridge arm based on the operating status of the main power modules on each bridge arm; and executing a corresponding bypass mechanism based on the number of faulty main power modules and the number of redundant power modules on each bridge arm. The bypass mechanism includes a power module-level bypass mechanism, a frequency converter module-level bypass mechanism, and a system-level bypass mechanism. This enables three fault-passing modes for the AC-AC frequency converter: six-phase operation, nine-phase operation, or power frequency operation, when the number of main power modules is greater than, less than, or equal to the number of redundant power modules.

The inverter (408) converts the power output from the distributed power source (40) into AC power and outputs it to the AC system. The inverter control circuit (409) generates a target AC voltage value for controlling the inverter (408) and generates a command value for controlling the inverter (408) as a voltage source. When the inverter (408) is connected to the AC system, the inverter control circuit (409) makes the frequency of the target AC voltage value the frequency of the AC voltage detected by the AC frequency detection circuit (4091), and when the target AC power value is in the direction of power operation, it controls the phase of the target AC voltage value to be at least the leading phase relative to the AC voltage of the AC system.

A single-stage multi-path direct current access converter and a control method thereof are provided. The single-stage multi-path direct current access converter includes an AC-side conversion circuit; at least two DC-side conversion circuits; and transformers corresponding to the at least two DC-side conversion circuits. AC sides of the at least two DC-side conversion circuits are respectively connected to primary windings of the corresponding transformers; secondary windings of the transformers are connected in parallel to a first side of the AC-side conversion circuit; each of the at least two DC-side conversion circuits is configured to invert DC power received by the DC-side conversion circuit, or to rectify AC power received by the DC-side conversion circuit; and the AC-side conversion circuit is configured to perform AC frequency conversion.

The utility model discloses an active energy recovery device for double-motor twin trawling, which comprises an AC / DC (alternating current / direct current) inversion device, the input end of the AC / DC inversion device is connected to a three-phase alternating current input line, and the AC / DC inversion device comprises a direct current output end. The number of the DC / AC frequency converter devices is two, and the two DC / AC frequency converter devices are connected in parallel with the DC output end of the AC / DC inversion device. Each DC / AC frequency converter device comprises a three-phase output end. The number of the motors is two, the power connection ends of the two motors are connected with the three-phase output ends of the two DC / AC frequency converter devices respectively, the output shafts of the two motors are oppositely dragged through a butt joint device, and one motor with the small torque in the two motors supplies power to the other DC / AC frequency converter device through the correspondingly connected DC / AC frequency converter device. The device can realize electric quantity recovery and reduce energy waste.

Timing adjustment for accurate zero-crossing determination includes obtaining time offset(s) representing amounts of time between (i) zero-crossings of an input signal waveform, representative of an input AC waveform, input to a zero-crossing detector circuit and (ii) corresponding transitions of an output signal from an output of the circuit to a microcontroller, and determining times of the zero-crossings of the input AC waveform, which includes determining times of the corresponding transitions as detected by the microcontroller and adjusting the determined times using the time offset(s) to produce the times of the zero-crossings of the input AC waveform. In another aspect, input AC frequency is determined by determining pulse width(s) of pulse(s) of the output signal, and adjusting a half-cycle time corresponding to the pulse width(s) using the time offset(s) to provide a duration of half-cycles of the input AC waveform and inform a frequency of the input AC waveform.

The present application relates to the technical field of power grid control and offshore wind power transmission topology, and particularly relates to a parallel DRU-MMC flexible low-frequency transmission system for offshore wind power and a control method thereof. The onshore frequency conversion station comprises a low-frequency side transformer module, an onshore rectifier station, an onshore inverter station and a power frequency side transformer. The onshore rectifier station comprises an MMC rectifier and a DRU rectifier module formed by a plurality of DRU rectifiers connected in series. In the present application, the DRU rectifier and the MMC are integrated on the onshore frequency conversion station, the onshore AC-AC frequency conversion is realized, and thus the offshore wind farm can be directly connected to the onshore through the low-frequency AC submarine cable to provide black start power for the offshore wind farm. Moreover, the present application makes full use of the characteristics of the DRU rectifier, such as higher reliability, smaller investment cost and smaller power loss, overcomes the defects of high cost and poor power quality of offshore low-frequency AC power transmission, and realizes bidirectional optimization of power transmission quality and construction cost control.

The present disclosure provides a positive and negative bipolar modular multilevel alternating current (AC)-AC frequency converter, including a modular multilevel frequency converter and a three-phase three-winding bipolar transformer. The modular multilevel frequency converter has an ABC three-phase structure, each phase includes the same upper bridge arm and lower bridge arm, and the upper and lower bridge arms include n full-bridge sub-modules (FBSMs) and a bridge arm inductor connected in series. The positive and negative bipolar modular multilevel AC-AC frequency converter can be further expanded and enable bidirectional energy flow. In the present disclosure, by introducing a positive and negative bipolar three-winding transformer, an AC-AC frequency converter topology with simple structure, high efficiency, flexibility and reliability is realized, which has high practical value.

The utility model relates to the technical field of lighting lamps, aims to solve the technical problems of high power consumption and high cost of the conventional lamp driving circuit, and discloses an LED (light-emitting diode) footpath lamp for landscape lighting, which comprises a rectifying and filtering circuit, a control module, a triode and a light-emitting diode, the direct current output end of the rectification filter circuit is connected with the power supply end of the control module through the first current-limiting resistor and the second current-limiting resistor in sequence, the driving level output end of the control module is connected with the base electrode of the triode through the third current-limiting resistor, and the collector electrode of the triode is grounded through the fourth current-limiting resistor and the light-emitting diode in sequence. An emitter of the triode is connected with a common node of the first current-limiting resistor and the second current-limiting resistor; the AC frequency sampling end of the control module is connected with the phase line through the sampling resistor and is grounded through the first capacitor. The circuit design is optimized, the circuit structure is simple, the power consumption is low, the cost is low, and the operation is reliable.

The measurement system includes a vibration transducer (10) and measurement system electronics (20), which are electrically coupled to the transducer (10) for controlling the transducer and for evaluating the vibration measurement signals (s1, s2) provided by the transducer. The exciter assembly includes a vibration exciter (31) designed to convert electrical power having a time-varying current into mechanical power such that a time-varying driving force acts on the tube at a drive point formed by the vibration exciter on the tube mechanically connected to the vibration exciter, wherein the vibration exciter (31) is positioned and designed such that the drive offset (ΔE) between the drive cross-sectional area of ​​the tube surrounded by an imaginary circumference of the tube intersecting the drive point and a predefined reference cross-sectional area of ​​the tube, i.e., a minimum distance not greater than 3° mm of the tube length and / or less than 0.5% of the tube length, and wherein the vibration node of the vibration motion formed between two antinodes of the vibration motion of at least one of the second-order or higher-order vibration modes (deviating from the first-order vibration mode) of the tube is located within the reference cross-sectional area. The measurement system electronics (20) are designed to feed electrical power to the vibration exciter (31) via an electrical drive signal (e1) having a time-varying current, causing the tube to perform forced mechanical vibration with one or more vibration frequencies specified by the drive signal (e1), wherein the measurement system electronics provide the drive signal (e1) with a (AC) frequency (f eN1 ) or (AC) frequency (f eN2 The sinusoidal (useful) current components (eN1, eN2) make the (AC) frequency (f) eN1 The resonant frequency (f) of the pipe's naturally inherent odd-order vibration modes. 2n+1 Deviation and (AC) frequency (f) eN2 The resonant frequency (f) of the even-order vibration mode inherent in the tube. 2n+2 The deviation is less than 1% and / or less than 1 Hz, and the measured value of at least one flow parameter of the measurement material guided in the transducer is determined based on the corresponding useful signal component (s1N1; s2N1; s1N2; s2N2) of at least one of the vibration measurement signals (s1, s2).