Efficient electrical measuring instrument verification system and verification method

Abstract

The invention relates to the technical field of electric power measurement testing, and discloses an efficient electric measuring instrument verification system and method, and the system comprises a central control unit and a central low-power-consumption reference source which are located in a primary potential domain, and a plurality of distributed active servo nodes located in a secondary floating potential domain. The nodes are connected through a virtual floating ground bus, a four-quadrant power conversion unit, a differential error amplification unit and an embedded Kelvin sensing circuit are integrated in the nodes, and the Kelvin sensing circuit collects terminal voltage feedback signals of the input end of a measured instrument. And the differential error amplification unit compares the signal with an analog standard reference signal transmitted through fluxgate isolation, and generates an instruction to control the power conversion unit to actively compensate the line voltage drop. Through the distributed floating ground architecture and tail end closed-loop feedback, zero-voltage-drop high-precision transmission of verification signals is achieved, common-mode interference is effectively restrained, and the dynamic topology reconstruction and energy feedback functions are achieved.

Description

Technical Field

[0001] This invention relates to the field of power metering and testing technology, specifically to an efficient electrical measuring instrument calibration system and calibration method. Background Technology

[0002] With the advancement of smart grid construction, the calibration of electrical measuring instruments places higher demands on the output accuracy, stability, and field adaptability of signal sources. Existing electrical measuring instrument calibration devices typically employ a centralized signal source architecture, generating voltage and current signals through power amplifiers and transmitting these signals to the instrument under test using test leads.

[0003] In actual verification processes, long connection lines are often required between the power signal source and the instrument under test. Due to the inherent physical impedance of the test leads, a voltage drop occurs when transmitting large currents or high-frequency signals. This voltage drop causes the actual voltage applied to the input of the instrument under test to be lower than the set output value of the signal source. Although some traditional devices attempt to correct the error by pre-setting fixed compensation parameters in software, the uncertainties in the length of the wiring, contact resistance, and ambient temperature make it difficult for fixed compensation methods to eliminate dynamically changing voltage drops in real time, thus affecting the accuracy of power metering verification.

[0004] Traditional calibration devices typically employ a common ground design or a partially isolated architecture for their output channels, with the reference potentials of each channel coupled together via ground or a common base plate. When performing calibration in complex industrial environments with varying electromagnetic conditions, this architecture is prone to creating ground loops, introducing common-mode interference signals and distorting the measured signal. Furthermore, when multiple instruments are tested concurrently at different reference points, the lack of an independent floating ground isolation potential domain can easily lead to electrical short circuits between channels, affecting not only the reliability of the test data but also potentially causing hardware damage to the calibration equipment and the instruments under test.

[0005] When dealing with calibration tasks involving different wiring systems such as three-phase four-wire and three-phase three-wire, existing devices often have relatively fixed hardware topologies. Operators typically need to adjust phase relationships through complex relay matrix switching or manual wiring modifications, a cumbersome and inefficient process. Furthermore, traditional power sources often employ linear amplifier circuits, which, when driving nonlinear loads such as inductive or capacitive loads, cannot effectively recover the reactive power fed back from the load and can only dissipate as heat. This not only leads to high overall system power consumption and low energy utilization but also increases the heat dissipation burden and size of the equipment. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an efficient electrical instrument calibration system and method, which solves the technical problems of existing electrical instrument calibration devices in long-distance transmission, such as large line voltage drop loss, poor common-mode interference suppression capability, and insufficient flexibility in multi-phase topology configuration.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a high-efficiency electrical instrument calibration system, which mainly consists of a central control unit, a central low-power reference source, a virtual floating ground bus, and multiple distributed active servo nodes. In terms of system architecture, the central control unit and the central low-power reference source are located in the primary potential domain, which uses the earth's protective ground wire as a reference potential. The multiple distributed active servo nodes are physically independent, each forming an independent secondary floating ground potential domain. The virtual floating ground bus connects the primary and secondary floating ground potential domains and is used for transmitting electrical energy, interactive control signals, and transmitting analog standard reference signals.

[0008] In this system, the output of each distributed active servo node is directly connected to the input terminal of the instrument under test. The central control unit sends phase configuration commands and amplitude control commands to each distributed active servo node via a virtual floating ground bus to configure the operating parameters of the distributed active servo nodes. The distributed active servo nodes receive an analog standard reference signal from the central low-power reference source and use this as a reference to output a drive voltage to the instrument under test.

[0009] Each distributed active servo node integrates a four-quadrant power converter, a differential error amplifier, an embedded Kelvin sensing circuit, and a rectifier and voltage regulator circuit. The rectifier and voltage regulator circuit converts AC power from the virtual floating ground bus into DC power, and its output negative terminal is defined as the floating signal ground. This floating signal ground serves as the reference potential for the secondary floating ground potential domain and has no direct electrical connection with the earth's protective ground wire, thus blocking the path of ground loop interference current.

[0010] Furthermore, the system employs a differential closed-loop control architecture based on end-point sensing. An embedded Kelvin sensing circuit is connected to the input terminal of the instrument under test (AUT) to acquire the end-point voltage feedback signal. A differential error amplification unit receives the analog standard reference signal and the end-point voltage feedback signal, and generates a voltage correction command signal by comparing the instantaneous difference between the two. A four-quadrant power converter adjusts the output drive voltage according to this voltage correction command signal. This architecture sets the feedback sampling point of the control loop at the load end. By adjusting the amplitude of the drive voltage to compensate for the impedance voltage drop on the power transmission line, the system ensures that the actual potential at the input terminal of the AUT always follows the analog standard reference signal, achieving zero-dropout servo control.

[0011] To ensure the linearity of signal transmission across domains, the system is equipped with electrical isolation connection components. A high-frequency isolation transformer is responsible for coupling power transmission and blocking DC conduction paths. A fluxgate isolation interface connects the central low-power reference source and the differential error amplifier unit. Utilizing an internal closed-loop control circuit and secondary compensation winding, a zero-flux feedback mechanism transmits the analog standard reference signal from the primary potential domain to the secondary floating ground potential domain, avoiding the nonlinear temperature drift error inherent in traditional opto-isolators.

[0012] This invention also employs an energy feedback DC bus technology. The DC side of the four-quadrant power converter units within all distributed active servo nodes is connected in parallel to this bus. When a node is in source mode, it draws power from the bus; when a node is in load mode, it rectifies the energy fed back from the measured instrument and injects it into the bus. This mechanism enables energy sharing between different nodes, reducing the overall power consumption of the system.

[0013] In terms of adaptive control, the distributed active servo node has impedance characteristic adjustment capabilities. By injecting a linear frequency modulated pulse voltage signal into the electrical instrument under test, the node acquires the frequency domain response sequence of voltage and current and calculates the complex input impedance. Based on the complex input impedance, the phase margin of the control loop is calculated. When it is determined that the phase margin is insufficient due to capacitive load, the proportional and derivative coefficients inside the controller are adjusted to ensure the stability of the system under different load characteristics.

[0014] A second aspect of this invention provides a method for calibrating electrical measuring instruments based on the aforementioned system. This method first involves a central control unit configuring the phase relationships and operating modes of multiple distributed active servo nodes according to the wiring parameters of the electrical measuring instrument under test. For a three-phase four-wire system, three nodes are controlled to output voltages with a phase difference of a specific angle; for a three-phase three-wire system, one node is controlled to enter a zero-potential reference mode and clamped to a common reference point, while the remaining nodes output line voltages.

[0015] Subsequently, the central low-power reference source generates an analog standard reference signal, which is transmitted across the potential domain to the differential error amplification unit of the distributed active servo node through a fluxgate isolation interface.

[0016] During the verification process, the embedded Kelvin sensing circuit inside the distributed active servo node acquires the terminal voltage feedback signal at the input terminal of the tested electrical instrument through an independent voltage sensing line. Since the voltage sensing line does not carry load current, this signal characterizes the actual controlled state of the load.

[0017] The differential error amplification unit calculates the difference between the analog standard reference signal and the terminal voltage feedback signal in real time, and generates a voltage correction command signal using a proportional-integral-derivative (PID) control algorithm. The four-quadrant power converter unit responds to this command signal by outputting a drive voltage. This drive voltage compensates for the voltage drop generated by the power drive line during transmission, ensuring that the actual potential at the input terminal of the tested instrument tracks the analog standard reference signal in real time, thereby reducing the impact of transmission line loss on calibration accuracy.

[0018] This invention provides a highly efficient calibration system and method for electrical measuring instruments. It offers the following advantages: 1. This invention achieves zero-dropout high-precision transmission of the verification excitation signal. It adopts a differential feedback loop model integrated within a distributed active servo node. Through an embedded Kelvin sensing circuit, the terminal voltage feedback signal is directly acquired at the input terminal of the electrical instrument under test. The differential error amplification unit compares this feedback signal with the analog standard reference signal transmitted through the fluxgate isolation interface in real time, and controls the four-quadrant power converter to actively increase the amplitude of the drive voltage. This closed-loop control mechanism based on load end sampling can automatically compensate for the impedance voltage drop on the power drive line, ensuring that the actual controlled potential of the instrument under test port does not decrease with changes in load current and line length, thus solving the problem of decreased verification accuracy caused by long-distance transmission.

[0019] 2. This invention improves the system's anti-interference capability and security by constructing a virtual floating ground architecture that includes a primary potential domain and multiple secondary floating ground potential domains. Through an electrical isolation connection component consisting of a high-frequency isolation transformer and a fluxgate isolation interface, the DC conduction path between the central control unit and each distributed node is blocked. The negative output terminal of the rectifier and voltage regulator circuit is defined as the floating signal ground. This architecture cuts off the path of ground loop interference current, allowing the reference potential of the distributed nodes to fluctuate with the port potential of the instrument under test, effectively suppressing common-mode interference signals and preventing the risk of electrical short circuits between different channels, thus adapting to the field verification requirements in complex electromagnetic environments.

[0020] 3. This invention improves verification efficiency and system energy efficiency. By using a virtual floating ground bus to transmit phase configuration commands and cooperating with the dynamic topology reconfiguration logic of the central control unit, the phase relationship and operating mode of distributed nodes can be flexibly configured according to the wiring system of the instrument under test without the need for manual replacement of hardware wiring. At the same time, the system is equipped with an energy feedback DC bus, which connects the DC side of the four-quadrant power converter units of all nodes in parallel. When some nodes are in load mode, their feedback energy can be directly supplied to the nodes in source mode through the DC bus, realizing the internal recycling of the feedback power of the instrument under test and significantly reducing the overall heat loss and power consumption of the system. Attached Figure Description

[0021] Figure 1 This is a system architecture diagram of the present invention; Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please see the appendix Figure 1 -Appendix Figure 2 This invention provides an efficient electrical measuring instrument calibration system and method, comprising: a central control unit, a central low-power reference source, a virtual floating ground bus, multiple distributed active servo nodes, and a dynamic interconnection matrix.

[0024] The central control unit is the main control center of the system. It is connected to the virtual floating ground bus via digital communication lines. The central control unit is used to issue verification commands, timing synchronization signals, and impedance spectrum scanning parameters.

[0025] The central low-power reference source is connected to the virtual floating ground bus. The central low-power reference source is used to generate high-precision voltage and frequency reference signals. As a reference generator for signal potentials, the central low-power reference source does not directly provide the power required to drive loads to subsequent circuits.

[0026] The virtual floating ground bus establishes the system's data transmission and energy exchange channels. Specifically, the virtual floating ground bus includes a high-frequency magnetic isolation interface and an energy feedback DC bus. The high-frequency magnetic isolation interface transmits digital signals from the central control unit and analog reference signals from the central low-power reference source to each distributed active servo node, while simultaneously isolating the electrical connections between the distributed active servo nodes. The energy feedback DC bus is physically connected to the power input terminals of all distributed active servo nodes, enabling the convergence and bidirectional flow of DC power between the distributed active servo nodes.

[0027] Multiple distributed active servo nodes are connected in parallel on a virtual floating ground bus. Each distributed active servo node is independently connected to one electrical instrument under test. Each distributed active servo node is powered through an independent isolation transformer, so that the signal ground of the distributed active servo node is floating relative to the ground potential.

[0028] The distributed active servo node integrates a four-quadrant power converter unit. The DC terminal of the four-quadrant power converter unit is connected to the energy feedback DC bus. The AC terminal of the four-quadrant power converter unit is connected to the input terminal of the instrument under test. The four-quadrant power converter unit has source mode and load mode; the source mode is used for power output, and the load mode is used for power absorption.

[0029] The distributed active servo node also integrates a Kelvin sensing circuit. This circuit has a four-wire connection port, which is physically connected to the input terminal of the instrument under test. The Kelvin sensing circuit is used to acquire the actual voltage and current signals at the input terminal of the instrument under test.

[0030] The distributed active servo node further integrates a differential error amplifier unit. The first input of the differential error amplifier unit receives a reference signal from the central low-power reference source. The second input of the differential error amplifier unit receives a feedback signal from the Kelvin sensing circuit. The output of the differential error amplifier unit is connected to the control terminal of the four-quadrant power converter unit, thus forming a closed-loop negative feedback control circuit within the distributed active servo node.

[0031] A dynamic interconnect matrix is ​​positioned between the signal output terminals of multiple distributed active servo nodes. The dynamic interconnect matrix consists of a programmable precision switch array. It is used to switch the physical connection relationships between the distributed active servo nodes according to instructions from the central control unit, enabling each distributed active servo node to operate independently or in a series-parallel interconnected state.

[0032] This invention provides a high-efficiency electrical measuring instrument calibration system and method. The method is based on the aforementioned high-efficiency electrical measuring instrument calibration system, and its main workflow includes: Step S100: Perform system power-on and communication establishment. The central control unit sends communication connection commands to each distributed active servo node via the virtual floating ground bus. Each distributed active servo node obtains power through the isolation transformer and starts up. Each distributed active servo node performs self-tests on its internal four-quadrant power converter unit and Kelvin sensing circuit, and feeds back the self-test status to the central control unit.

[0033] Step S200: Perform dynamic impedance spectrum adaptive matching. Before the distributed active servo node outputs its rated verification power, the central control unit instructs the distributed active servo node to enter impedance detection mode. The four-quadrant power converter unit injects a swept-frequency test signal into the input port of the instrument under test. The Kelvin sensing circuit collects the voltage and current response data of the input port of the instrument under test to the swept-frequency test signal. The distributed active servo node calculates the input impedance parameters of the instrument under test based on the voltage and current response data. The distributed active servo node adjusts the gain coefficient and time constant of the internal control loop of the differential error amplifier unit according to the input impedance parameters.

[0034] Step S300: Perform distributed differential servo calibration. The central control unit sends calibration waveform parameters to the central low-power reference source. The central low-power reference source sends an analog standard reference signal to all distributed active servo nodes via a high-frequency magnetic isolation interface. The differential error amplifier unit receives the analog standard reference signal. Simultaneously, the Kelvin sensing circuit acquires the actual terminal voltage signal at the input terminal of the instrument under test in real time and transmits it to the differential error amplifier unit. The differential error amplifier unit compares the analog standard reference signal with the actual terminal voltage signal and generates an error compensation signal. The four-quadrant power converter unit adjusts the output voltage according to the error compensation signal to ensure that the actual terminal voltage signal at the input terminal of the instrument under test is consistent with the analog standard reference signal.

[0035] Step S400: Implement energy balance management. During the execution of step S300, the central control unit calculates the phase offset of each four-quadrant power converter unit based on the real-time operating status of all distributed active servo nodes. The central control unit controls each four-quadrant power converter unit to perform interleaved conduction according to the phase offset. The feedback energy generated and the consumed energy of each distributed active servo node are vector-superimposed on the energy feedback DC bus.

[0036] Step S500: Perform source table mirror polling self-calibration. During the interval following the verification process defined in step S300, the central control unit controls the dynamic interconnect matrix to close, physically connecting the outputs of the first distributed active servo node and the second distributed active servo node. The first distributed active servo node operates in source mode and outputs calibration signals, while the second distributed active servo node operates in measurement mode and acquires calibration signals, obtaining the first set of calibration data. Subsequently, the first distributed active servo node switches to measurement mode, and the second distributed active servo node switches to source mode, obtaining the second set of calibration data. The central control unit calculates the drift error values ​​of the first and second distributed active servo nodes based on the first and second sets of calibration data and updates the compensation parameters of the distributed active servo nodes.

[0037] The four-quadrant power converter unit provided by this invention is the power execution stage of a distributed active servo node. The four-quadrant power converter unit mainly includes: a full-bridge inverter circuit, a local energy storage capacitor, an output filter circuit, and a gate drive circuit.

[0038] The DC input terminal of the four-quadrant power converter is physically connected to the energy feedback DC bus. A local energy storage capacitor is connected in parallel between the positive and negative terminals of the energy feedback DC bus. The local energy storage capacitor is used to reduce voltage fluctuations on the energy feedback DC bus and to provide instantaneous pulse current to the full-bridge inverter circuit.

[0039] The full-bridge inverter circuit consists of four power switches: the first power switch, the second power switch, the third power switch, and the fourth power switch. The first power switch, the second power switch, the third power switch, and the fourth power switch are either insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0040] The first and second power switches are connected in series to form the first bridge arm. The first end of the first bridge arm is connected to the positive terminal of the local energy storage capacitor, and the second end is connected to the negative terminal of the local energy storage capacitor. The third and fourth power switches are connected in series to form the second bridge arm. The first end of the second bridge arm is connected to the positive terminal of the local energy storage capacitor, and the second end is connected to the negative terminal of the local energy storage capacitor. Each power switch is connected in reverse parallel with a freewheeling diode.

[0041] The input terminal of the output filter circuit is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm. The midpoint of the first bridge arm is located at the connection point of the first and second power switches. The midpoint of the second bridge arm is located at the connection point of the third and fourth power switches. The output terminal of the output filter circuit is connected to the input port of the instrument under test. The output filter circuit includes a filter inductor and a filter capacitor. The output filter circuit is used to filter out the high-frequency switching ripple generated by the full-bridge inverter circuit and restore the pulse width modulation waveform to a sinusoidal waveform signal.

[0042] The signal input terminal of the gate drive circuit is connected to the output terminal of the differential error amplifier unit. The four drive output terminals of the gate drive circuit are respectively connected to the control gates of the first power switch, the second power switch, the third power switch, and the fourth power switch.

[0043] The gate drive circuit receives the error compensation signal from the differential error amplifier unit. Based on the error compensation signal, the gate drive circuit generates a pulse width modulation (PWM) signal. The gate drive circuit uses the PWM signal to control the on and off states of the first, second, third, and fourth power switches, thereby adjusting the amplitude and phase parameters of the full-bridge inverter circuit's output voltage.

[0044] When the four-quadrant power converter unit operates in source mode, electrical energy flows from the energy feedback DC bus through the full-bridge inverter circuit to the electrical instrument under test. At this time, the absolute value of the angle between the phase of the output voltage and the phase of the output current of the full-bridge inverter circuit is less than 90 degrees.

[0045] When the four-quadrant power converter operates in load mode, electrical energy flows from the measured instrument to the energy feedback DC bus. At this time, the feedback current from the measured instrument is rectified by the freewheeling diode and stored in the local energy storage capacitor, and then flows into the energy feedback DC bus.

[0046] The floating ground power supply and fluxgate isolation interface provided by this invention is integrated into the input front end of a distributed active servo node. The floating ground power supply and fluxgate isolation interface mainly includes: a high-frequency isolation transformer, a rectifier and voltage regulator circuit, and a fluxgate isolation interface.

[0047] The primary winding of the high-frequency isolation transformer is connected to the power transmission line in the virtual floating ground bus. The secondary winding of the high-frequency isolation transformer is connected to the AC input terminal of the rectifier and voltage regulator circuit. An electrostatic shielding layer is provided between the primary and secondary windings of the high-frequency isolation transformer. The high-frequency isolation transformer is used to couple the AC power transmitted by the virtual floating ground bus to the interior of the distributed active servo node.

[0048] The positive DC output of the rectifier and voltage regulator circuit is connected to the power input of the four-quadrant power converter unit, the differential error amplifier unit, and the Kelvin sensing circuit. The negative DC output of the rectifier and voltage regulator circuit is defined as the floating signal ground. There is no direct electrical connection between the floating signal ground and the earth's potential.

[0049] The signal input terminal of the fluxgate isolation interface is connected to the central low-power reference source. The signal output terminal of the fluxgate isolation interface is connected to the first input terminal of the differential error amplifier unit. The fluxgate isolation interface includes: a primary signal winding, a secondary compensation winding, a flux detection probe, a high-permeability toroidal core, a closed-loop control circuit, and a precision sampling resistor.

[0050] The primary signal winding is wound on a high-permeability toroidal core. The secondary compensation winding is wound on a high-permeability toroidal core. The primary signal winding receives an analog standard reference signal from a central low-power reference source. The analog standard reference signal generates primary magnetic flux in the primary signal winding.

[0051] A flux detection probe is positioned within the air gap of a high-permeability toroidal core. The output of the flux detection probe is connected to the input of a closed-loop control circuit. The output of the closed-loop control circuit is connected to the first terminal of the secondary compensation winding. The second terminal of the secondary compensation winding is connected to the first terminal of a precision sampling resistor. The second terminal of the precision sampling resistor is connected to the floating signal ground.

[0052] A flux detection probe detects the residual magnetic flux within a high-permeability toroidal core and outputs a flux error signal. A closed-loop control circuit outputs a compensation current based on this error signal. This compensation current flows through a secondary compensation winding. The compensation current generates a secondary magnetic flux in the secondary compensation winding. The direction of the secondary magnetic flux is opposite to that of the primary magnetic flux.

[0053] The first terminal of the precision sampling resistor is connected to the first input terminal of the differential error amplifier unit. The precision sampling resistor converts the compensation current flowing through the secondary compensation winding into a feedback voltage signal. The feedback voltage signal serves as a reference within the distributed active servo node.

[0054] The embedded Kelvin sensing circuit provided by this invention is integrated into the output end of a distributed active servo node. The embedded Kelvin sensing circuit mainly includes: a four-wire connection port, a high input impedance instrumentation amplifier, a precision shunt resistor, and a current sensing amplifier.

[0055] The four-wire connection port includes: a first power drive line, a second power drive line, a first voltage sensing line, and a second voltage sensing line.

[0056] One end of the first power drive circuit is connected to the first AC output terminal of the four-quadrant power converter unit. The other end of the first power drive circuit is connected to the first input terminal of the instrument under test. One end of the second power drive circuit is connected to the second AC output terminal of the four-quadrant power converter unit. The other end of the second power drive circuit is connected to the second input terminal of the instrument under test. The first and second power drive circuits are used to transmit the load current required to drive the instrument under test.

[0057] One end of the first voltage sensing line is connected to the first input terminal of the instrument under test. The connection point of the first voltage sensing line is located outside the contact point between the first power drive line and the instrument under test. One end of the second voltage sensing line is connected to the second input terminal of the instrument under test. The connection point of the second voltage sensing line is located outside the contact point between the second power drive line and the instrument under test. Both the first and second voltage sensing lines are in a high-impedance state and do not transmit load current.

[0058] The non-inverting input of the high input impedance instrumentation amplifier is connected to the other end of the first voltage sensing circuit. The inverting input of the high input impedance instrumentation amplifier is connected to the other end of the second voltage sensing circuit.

[0059] The output of the high input impedance instrumentation amplifier is divided into a first signal branch and a second signal branch. The first signal branch is connected to the second input terminal of the differential error amplifier unit. The high input impedance instrumentation amplifier transmits the acquired terminal voltage feedback signal to the differential error amplifier unit through the first signal branch. The second signal branch is connected to the analog-to-digital converter inside the distributed active servo node.

[0060] A precision shunt resistor is connected in series in the second power drive circuit. The first terminal of the precision shunt resistor is connected to the second AC output terminal of the four-quadrant power converter unit. The second terminal of the precision shunt resistor is connected to the second input terminal of the instrument under test.

[0061] The first input terminal of the current-sensing amplifier is connected to the first terminal of the precision shunt resistor. The second input terminal of the current-sensing amplifier is connected to the second terminal of the precision shunt resistor. The output terminal of the current-sensing amplifier is connected to the analog-to-digital converter inside the distributed active servo node.

[0062] The virtual floating ground architecture provided by this invention is used to construct the electrical operating environment for distributed active servo nodes. The virtual floating ground architecture mainly includes: a primary potential domain, electrically isolated connection components, and multiple secondary floating ground potential domains.

[0063] The primary potential domain physically encompasses the signal input ports of the central control unit, the central low-power reference source, and the virtual floating ground bus. A primary reference ground is provided within the primary potential domain. This primary reference ground is physically connected to the protective earth (PE) of the external power supply system. All logic level signals within the primary potential domain use the primary reference ground as their zero-potential reference.

[0064] An electrical isolation connection assembly is positioned between the primary potential domain and multiple secondary floating ground potential domains. The assembly consists of a high-frequency isolation transformer and a high-frequency magnetic isolation interface. The high-frequency isolation transformer transmits power energy. The high-frequency magnetic isolation interface transmits control signals and analog reference signals. The electrical isolation connection assembly blocks the DC conductive path between the primary potential domain and the secondary floating ground potential domains.

[0065] Multiple secondary floating ground potential domains correspond to each independent distributed active servo node. The internal circuitry of each distributed active servo node constitutes an independent secondary floating ground potential domain. Each secondary floating ground potential domain is equipped with a secondary floating ground wire. The secondary floating ground wire is connected to the negative output terminal of the internal rectifier and voltage regulator circuit of the distributed active servo node. There is insulation resistance between the secondary floating ground wire and the primary reference ground wire.

[0066] The secondary floating ground potential domain of the first distributed active servo node is independent of the secondary floating ground potential domain of the second distributed active servo node. There is no direct electrical connection between the secondary floating ground wire of the first distributed active servo node and the secondary floating ground wire of the second distributed active servo node.

[0067] The high-frequency magnetic isolation interface integrates a multi-channel digital isolator. The primary-side signal pins of the multi-channel digital isolator are connected to the central control unit. The secondary-side signal pins of the multi-channel digital isolator are connected to the controller inside the distributed active servo node. The primary-side power supply pins of the multi-channel digital isolator are connected to the positive power supply of the primary potential domain. The secondary-side power supply pins of the multi-channel digital isolator are connected to the positive power supply of the secondary floating ground potential domain.

[0068] The input terminals of the electrical instrument under test (DUT) are connected to the output terminals of the distributed active servo node. After the DUT is connected to the system, the internal circuit potential reference point of the DUT establishes an equipotential connection with the corresponding secondary floating ground wire. Because the secondary floating ground wire is insulated relative to the earth's protective ground wire, the leakage current path to ground of the DUT is blocked.

[0069] The energy feedback DC bus is configured as a floating transmission line. Both the positive and negative conductors of the energy feedback DC bus are insulated from the primary reference ground. The four-quadrant power converter units of all distributed active servo nodes are connected in parallel to the energy feedback DC bus. The energy feedback DC bus serves as a differential-mode energy exchange channel between the secondary floating ground potential domains.

[0070] This invention provides a DC-Link-based energy feedback mechanism based on a topology consisting of an energy feedback DC bus and multiple distributed active servo nodes connected in parallel. The DC-Link-based energy feedback mechanism includes: physical connection of the DC bus, bidirectional power flow paths, and a multi-channel phase-interleaved scheduling strategy.

[0071] The energy feedback DC bus comprises a positive DC bus and a negative DC bus. The energy feedback DC bus runs through the virtual floating ground bus. The DC input terminal of the four-quadrant power converter unit within each distributed active servo node is connected in parallel to the energy feedback DC bus. The local energy storage capacitor within each distributed active servo node is connected in parallel to the DC input terminal of the four-quadrant power converter unit. The local energy storage capacitor serves as the local energy storage element of the energy feedback DC bus at each distributed active servo node.

[0072] When the first distributed active servo node is running in source mode, its internal four-quadrant power converter unit obtains DC power from the energy feedback DC bus. The four-quadrant power converter unit inverts the DC power into AC power and drives the corresponding measured electrical instrument. At this time, current flows into the first distributed active servo node from the energy feedback DC bus.

[0073] When the second distributed active servo node is operating in load mode, or within the energy feedback range of the AC output cycle, the measured electrical instrument outputs electrical energy to the second distributed active servo node. The electrical energy is rectified by the freewheeling diodes of the four-quadrant power converter unit inside the second distributed active servo node and then flows in reverse into the local energy storage capacitor. The terminal voltage of the local energy storage capacitor increases. When the terminal voltage of the local energy storage capacitor is higher than the voltage of the energy feedback DC bus, electrical energy is injected into the energy feedback DC bus.

[0074] The energy feedback DC bus provides the energy flow path between the distributed active servo nodes. The feedback energy generated by the second distributed active servo node in load mode is transferred to the first distributed active servo node in source mode via the energy feedback DC bus. The external main power supply is connected to the energy feedback DC bus. The external main power supply only supplies the energy feedback DC bus with the net difference of the algebraic sum of the instantaneous power of all distributed active servo nodes and the system heat loss.

[0075] The central control unit performs multi-channel phase-interleaved scheduling. The central control unit obtains the total number N of distributed active servo nodes connected to the system. The central control unit calculates the phase offset, which is equal to 360 degrees divided by the total number N. The central control unit controls the carrier phase of the four-quadrant power converter units within each distributed active servo node to be distributed according to the phase offset.

[0076] Under multi-channel phase-interleaved scheduling, the moment when the first distributed active servo node absorbs the peak power from the energy feedback DC bus corresponds to the moment when the second distributed active servo node feeds back the peak power to the energy feedback DC bus. The ripple currents generated by different channels superimpose and cancel each other on the energy feedback DC bus, reducing the total ripple current amplitude on the energy feedback DC bus.

[0077] The impedance calculation and parameter tuning process provided by this invention is executed by the digital signal processor inside the distributed active servo node. The impedance calculation and parameter tuning process includes: frequency domain transformation, complex impedance calculation, and controller parameter update.

[0078] The distributed active servo node reads the instantaneous terminal voltage response signal sequence and the instantaneous loop current response signal sequence from its local buffer memory. The distributed active servo node performs a Fast Fourier Transform on the instantaneous terminal voltage response signal sequence to obtain the frequency domain voltage sequence. Distributed active servo nodes perform Fast Fourier Transform on the instantaneous loop current response signal sequence to obtain the frequency domain current sequence. .

[0079] Distributed active servo nodes based on frequency domain voltage sequences With frequency domain current sequence Calculate the complex input impedance of the electrical measuring instrument under test. Complex input impedance The calculation follows the frequency domain ratio relationship as follows: in, Represents frequency variables; This indicates that the electrical measuring instrument under test is at a certain frequency. The equivalent resistance component at the location; This indicates that the electrical measuring instrument under test is at a certain frequency. The equivalent reactance component at the point; It represents the imaginary unit.

[0080] Distributed active servo nodes based on equivalent reactance components The polarity of the measured electrical component determines the load characteristics of the instrument under test. When the value is negative, the measured electrical instrument is determined to exhibit capacitive load characteristics. When the equivalent reactance component... When the value is positive, it is determined that the electrical measuring instrument under test exhibits inductive load characteristics.

[0081] Distributed active servo nodes based on complex input impedance Calculate the closed-loop control phase margin required for the differential error amplifier unit. Phase margin The calculation formula is as follows: in, Indicates the crossover frequency of the control loop; This represents the complex open-loop gain of the differential error amplifier unit at the crossover frequency; This represents the inherent output impedance of the four-quadrant power converter unit; This indicates the phase angle operation for taking complex numbers.

[0082] The distributed active servo nodes will calculate the phase margin. Compare with a preset stability threshold. When the phase margin... When the angle is less than 45 degrees, the distributed active servo node adjusts the proportional coefficient of the PID controller inside the differential error amplification unit. Integral coefficient and differential coefficients .

[0083] When the measured electrical instrument exhibits capacitive load characteristics and phase margin When insufficient, the distributed active servo nodes reduce the scaling factor. And increase the differential coefficient This is to increase the damping ratio of the control loop. The distributed active servo node will adjust the proportional coefficient. Integral coefficient and differential coefficients Write the parameters to the register of the differential error amplifier unit to complete the parameter tuning of the control loop.

[0084] The impedance calculation and parameter tuning process provided by this invention is executed by the digital signal processor inside the distributed active servo node. The impedance calculation and parameter tuning process includes: frequency domain transformation processing, complex impedance data calculation, and controller parameter updating.

[0085] The distributed active servo node reads the instantaneous terminal voltage response signal sequence and the instantaneous loop current response signal sequence from its local buffer memory. The distributed active servo node performs a Discrete Fourier Transform on the instantaneous terminal voltage response signal sequence to obtain the frequency domain voltage sequence. Distributed active servo nodes perform discrete Fourier transform on the instantaneous loop current response signal sequence to obtain the frequency domain current sequence. .

[0086] Distributed active servo nodes based on frequency domain voltage sequences With frequency domain current sequence Calculate the complex input impedance of the electrical measuring instrument under test. Complex input impedance The calculation follows the following mathematical relationship: In the above relation, Represents frequency variables; This indicates that the electrical measuring instrument under test is at a certain frequency. The equivalent resistance component at the location; This indicates that the electrical measuring instrument under test is at a certain frequency. The equivalent reactance component at the point; It represents the imaginary unit.

[0087] Distributed active servo nodes based on equivalent reactance components The numerical polarity determines the load reactance property of the electrical measuring instrument under test. When the equivalent reactance component... When the value is negative, the measured electrical instrument is a capacitive load. When the equivalent reactance component... When the value is positive, the electrical measuring instrument under test is an inductive load.

[0088] Distributed active servo nodes based on complex input impedance Calculate the phase margin of the differential error amplifier unit. Phase margin The calculation formula is as follows: In the above formula, Indicates the crossover frequency of the control loop; This represents the open-loop gain of the differential error amplifier unit at the crossover frequency; This indicates the output impedance of the four-quadrant power converter unit; This indicates phase angle calculation.

[0089] Distributed active servo nodes will phase margin The value is compared with the system's preset stability threshold. When the phase margin... When the value is less than the preset stability threshold, the distributed active servo node adjusts the proportional coefficient of the internal controller of the differential error amplification unit. Integral coefficient and differential coefficients .

[0090] When the measured electrical instrument is a capacitive load and has a phase margin When the value is less than the preset stability threshold, the distributed active servo node reduces the scaling factor. And increase the differential coefficient The distributed active servo nodes will adjust the scaling factor. Integral coefficient and differential coefficients Write to the control register of the differential error amplifier unit.

[0091] The differential feedback loop model provided by this invention is integrated within a distributed active servo node. The differential feedback loop model consists of a central low-power reference source, a fluxgate isolation interface, a differential error amplification unit, a four-quadrant power converter unit, a Kelvin sensing circuit, and the connected electrical instruments under test.

[0092] The central low-power reference source is connected to the input of the fluxgate isolated interface. The central low-power reference source outputs an analog standard reference signal. The output of the fluxgate isolation interface is connected to the non-inverting input of the differential error amplifier unit. The fluxgate isolation interface will simulate a standard reference signal. Transmission occurs from the primary potential domain to the secondary floating ground potential domain.

[0093] The Kelvin sensing circuit is connected to the input terminal of the electrical instrument under test. The Kelvin sensing circuit uses a first voltage sensing line and a second voltage sensing line to acquire the terminal voltage feedback signal at the input terminal of the electrical instrument under test. The first voltage sensing circuit and the second voltage sensing circuit are in a high-impedance state. Terminal voltage feedback signal. It represents the actual potential at the input terminal of the electrical measuring instrument under test.

[0094] The output of the Kelvin sensing circuit is connected to the inverting input of the differential error amplifier unit. The differential error amplifier unit receives the analog standard reference signal. With terminal voltage feedback signal The differential error amplification unit performs a subtraction operation and generates an instantaneous error signal. Instantaneous error signal Satisfy the following definition: The differential error amplifier unit integrates a proportional-integral-derivative (PID) controller. The PID controller reads the pre-tuned proportional coefficient. Integral coefficient and differential coefficients The differential error amplification unit is based on the scaling factor. Integral coefficient and differential coefficients For instantaneous error signals The differential error amplifier unit outputs a voltage correction command signal. .

[0095] The output of the differential error amplifier unit is connected to the gate drive circuit inside the four-quadrant power converter unit. The gate drive circuit receives the voltage correction command signal. The four-quadrant power converter unit corrects the voltage command signal. Adjust the duty cycle parameters of the internal power switching transistors. Output drive voltage of the four-quadrant power converter unit. .

[0096] The output of the four-quadrant power converter unit is connected to the input terminal of the electrical instrument under test via the first power drive line and the second power drive line. Drive voltage During transmission, the impedance voltage drop between the first and second power drive lines is overcome. The differential feedback loop model maintains the voltage feedback signal at the sustaining terminal. Analog standard reference signal Consistency.

[0097] The zero-dropout servo execution process provided by this invention is executed by distributed active servo nodes during the calibration operation phase. The zero-dropout servo execution process is used to compensate for the line impedance voltage drop between the first power drive line and the second power drive line.

[0098] The central low-power reference source generates an analog standard reference signal. Analog standard reference signal The signal is transmitted through a fluxgate isolation interface to the distributed active servo node. The differential error amplifier unit receives the analog standard reference signal. The differential error amplifier unit will simulate the standard reference signal. Set as the target reference value for the servo control loop.

[0099] Four-quadrant power converter unit output drive voltage Drive voltage The power is applied to the electrical instrument under test via the first power drive circuit and the second power drive circuit. When the electrical instrument under test is operating, load current flows through the first power drive circuit and the second power drive circuit. Due to the inherent line impedance between the first power drive circuit and the second power drive circuit. The actual load voltage at the input terminal of the electrical measuring instrument under test With driving voltage There is a deviation. Actual load voltage The following physical relationship must be satisfied: The Kelvin sensing circuit uses a first voltage sensing line and a second voltage sensing line to acquire the potential at the input terminals of the instrument under test. The first and second voltage sensing lines are connected to a high-input-impedance instrumentation amplifier, making the current in the first and second voltage sensing lines negligible. No transmission voltage drop occurs in the first and second voltage sensing lines. The terminal voltage feedback signal output by the Kelvin sensing circuit... equal to actual load voltage .

[0100] Differential error amplifier unit receiver voltage feedback signal Analog standard reference signal Differential error amplifier unit calculation terminal voltage feedback signal Analog standard reference signal The difference. The differential error amplification unit amplifies the difference based on the scaling factor. Integral coefficient With differential coefficients Generate voltage correction command signal .

[0101] The four-quadrant power converter unit receives voltage correction command signals. The four-quadrant power converter unit corrects the voltage command signal. Adjust the duty cycle of the internal power switch transistors. Increase the drive voltage of the four-quadrant power converter unit. The amplitude.

[0102] The drive voltage output of the four-quadrant power converter unit Higher than the analog standard reference signal Drive voltage The excess amplitude partially offset the load current. In inherent line impedance The voltage drop generated on the terminal. The closed-loop negative feedback mechanism enables the terminal voltage feedback signal. Analog standard reference signal Maintain consistency. The actual load voltage at the input terminal of the electrical measuring instrument under test. Unaffected by load current The impact of change.

[0103] The dynamic topology reconfiguration logic provided by this invention is executed by a central control unit. This logic is used to configure the phase relationships and operating modes of distributed active servo nodes according to the wiring configuration of the electrical measuring instrument under test.

[0104] The central control unit's memory contains a pre-installed topology configuration table. This table includes node allocation rules for single-phase, three-phase three-wire, and three-phase four-wire wiring modes. The central control unit receives verification task instructions. These instructions contain the wiring parameters of the electrical measuring instrument under test.

[0105] The central control unit parses the wiring parameters. It selects an execution node from the idle distributed active servo nodes in the system. The central control unit defines the selected distributed active servo nodes as the first logical node, the second logical node, and the third logical node. The central control unit establishes a mapping relationship between the physical addresses of the distributed active servo nodes and the logical nodes.

[0106] When the wiring configuration is a three-phase four-wire connection, the central control unit sends an A-phase configuration command to the first logic node via the virtual floating ground bus. The first logic node sets its internal reference phase angle to 0 degrees according to the A-phase configuration command. The central control unit then sends a B-phase configuration command to the second logic node. The second logic node sets its internal reference phase angle to 240 degrees according to the B-phase configuration command. Finally, the central control unit sends a C-phase configuration command to the third logic node. The third logic node sets its internal reference phase angle to 120 degrees according to the C-phase configuration command.

[0107] When the wiring configuration is a three-phase three-wire connection, the central control unit performs a V-type wiring reconfiguration. The central control unit controls the second logic node to enter zero-potential reference mode. The second logic node clamps the output potential of the four-quadrant power converter unit to the secondary floating ground potential. The output of the second logic node serves as the system's common reference point. The central control unit controls the first logic node to output a first line voltage signal relative to the common reference point. The central control unit controls the third logic node to output a second line voltage signal relative to the common reference point.

[0108] The central control unit monitors the operating status of the first, second, and third logical nodes in real time. When the central control unit detects a fault in the first logical node, it searches for the fourth logical node among the remaining distributed active servo nodes. The central control unit disconnects the communication connection with the first logical node. The central control unit transmits the phase and amplitude parameters originally set for the first logical node to the fourth logical node. The fourth logical node starts up and takes over the output power signal from the first logical node.

[0109] After completing node allocation and parameter configuration, the central control unit broadcasts a synchronization trigger frame via the virtual floating ground bus. All participating distributed active servo nodes reset their internal waveform generators upon receiving the synchronization trigger frame. The synchronization trigger frame ensures that the phase difference between the output waveforms of different distributed active servo nodes conforms to the definition in the topology configuration table.

[0110] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency electrical measuring instrument calibration system, characterized in that, include: Central control unit, central low-power reference source, virtual floating ground bus and multiple distributed active servo nodes; The central control unit and the central low-power reference source are located in the primary potential domain, with the earth protection ground wire as the reference potential. The multiple distributed active servo nodes each constitute an independent secondary floating ground potential domain, and the output terminal of each distributed active servo node is connected to the input terminal of the electrical measuring instrument under test. The virtual floating ground bus is connected between the primary potential domain and the secondary floating ground potential domain, and is used to transmit electrical energy, control signals, and analog standard reference signals. The central control unit sends phase configuration commands and amplitude control commands to the multiple distributed active servo nodes through the virtual floating bus. The plurality of distributed active servo nodes output driving voltage to the electrical measuring instrument under test according to the analog standard reference signal.

2. The efficient electrical measuring instrument calibration system according to claim 1, characterized in that, Each of the distributed active servo nodes integrates: a four-quadrant power converter unit, a differential error amplifier unit, an embedded Kelvin sensing circuit, and a rectifier and voltage regulator circuit. The rectifier and voltage regulator circuit receives AC power from the virtual floating ground bus and generates DC power. The negative terminal of the DC output of the rectifier and voltage regulator circuit is defined as the floating signal ground, and the secondary floating ground potential domain takes the floating signal ground as the reference potential. The embedded Kelvin sensing circuit is connected to the input terminal of the electrical measuring instrument under test and is used to collect the terminal voltage feedback signal. The first input terminal of the differential error amplifier unit receives the analog standard reference signal, the second input terminal of the differential error amplifier unit receives the terminal voltage feedback signal, and the differential error amplifier unit outputs a voltage correction command signal according to the difference between the analog standard reference signal and the terminal voltage feedback signal. The four-quadrant power converter unit adjusts the amplitude and phase of the driving voltage according to the voltage correction command signal.

3. The efficient electrical measuring instrument calibration system according to claim 2, characterized in that, The system also includes an electrical isolation connection component disposed between the primary potential domain and the secondary floating ground potential domain; The electrical isolation connection assembly includes a high-frequency isolation transformer and a fluxgate isolation interface; The high-frequency isolation transformer is used to couple the power energy on the virtual floating ground bus to the rectifier and voltage regulator circuit, and to block the DC conduction path between the primary potential domain and the secondary floating ground potential domain. The fluxgate isolation interface is connected between the central low-power reference source and the differential error amplifier unit, and is used to linearly transmit the analog standard reference signal from the primary potential domain to the secondary floating ground potential domain. The fluxgate isolation interface contains a closed-loop control circuit and a secondary compensation winding, and maintains transmission accuracy through a zero flux feedback mechanism.

4. The efficient electrical measuring instrument calibration system according to claim 2, characterized in that, The virtual floating ground bus includes an energy feedback DC bus; The DC input terminals of the four-quadrant power converter units inside all the distributed active servo nodes are connected in parallel to the energy feedback DC bus. Each of the four-quadrant power converter units has a local energy storage capacitor connected in parallel to its DC input terminal; The four-quadrant power converter unit includes a full-bridge inverter circuit composed of power switching transistors; when the distributed active servo node is running in source mode, the full-bridge inverter circuit obtains power from the energy feedback DC bus. When the distributed active servo node is running in load mode, the full-bridge inverter circuit rectifies the electrical energy fed back by the measured electrical instrument and injects it into the energy feedback DC bus for use by other distributed active servo nodes running in source mode.

5. The efficient electrical measuring instrument calibration system according to claim 2, characterized in that, The embedded Kelvin sensing circuit includes a four-wire connection port and a high input impedance instrumentation amplifier. The four-wire connection port includes two power drive lines and two voltage sensing lines. The two power drive lines are connected between the AC output terminal of the four-quadrant power converter unit and the input terminal of the electrical measuring instrument under test, and are used to transmit load current. The two voltage sensing lines are connected between the input terminal of the electrical measuring instrument under test and the input terminal of the high input impedance instrumentation amplifier. The two voltage sensing lines do not carry load current. The high input impedance instrumentation amplifier outputs the terminal voltage feedback signal to the differential error amplifier unit.

6. The efficient electrical measuring instrument calibration system according to claim 5, characterized in that, The distributed active servo nodes are configured to perform zero-dropout servo control; The differential error amplification unit integrates a proportional-integral-derivative controller. The differential error amplification unit calculates the instantaneous error signal between the analog standard reference signal and the terminal voltage feedback signal; The proportional-integral-derivative controller adjusts the voltage correction command signal according to the instantaneous error signal, and controls the four-quadrant power converter unit to increase the amplitude of the drive voltage; The magnitude of the drive voltage increase is equal to the voltage drop generated by the load current across the line impedance of the two power drive lines, so that the actual potential at the input terminal of the electrical measuring instrument under test is consistent with the analog standard reference signal.

7. The efficient electrical measuring instrument calibration system according to claim 2, characterized in that, The distributed active servo node is also configured to perform impedance calculation and parameter tuning procedures before the verification operation. The four-quadrant power converter unit injects a linear frequency modulated pulse voltage signal into the electrical measuring instrument under test; The distributed active servo node acquires the instantaneous terminal voltage response signal sequence and instantaneous loop current response signal sequence of the electrical measuring instrument under test, and converts them into frequency domain voltage sequence and frequency domain current sequence. The distributed active servo node calculates the complex input impedance based on the ratio of the frequency domain voltage sequence to the frequency domain current sequence, and calculates the phase margin of the control loop of the differential error amplifier unit based on the complex input impedance. When the phase margin is less than the preset stability threshold and the complex input impedance exhibits capacitive load characteristics, the distributed active servo node reduces the proportional coefficient of the internal controller of the differential error amplifier unit and increases the differential coefficient.

8. The efficient electrical measuring instrument calibration system according to claim 1, characterized in that, The central control unit stores a topology configuration table and is configured to execute dynamic topology reconfiguration logic. The central control unit establishes a mapping relationship between the physical address and logical node of the distributed active servo node based on the wiring parameters of the electrical measuring instrument under test. When the wiring system parameters are in the three-phase four-wire wiring mode, the central control unit controls the three distributed active servo nodes to output voltage signals with a phase difference of 120 degrees respectively. When the wiring system parameters are in the three-phase three-wire wiring mode, the central control unit controls one of the distributed active servo nodes to enter the zero-potential reference mode, clamps its output potential to the reference potential of the secondary floating ground potential domain as a common reference point, and controls the other two distributed active servo nodes to output line voltage signals relative to the common reference point.

9. The efficient electrical measuring instrument calibration system according to claim 2, characterized in that, There is no direct electrical connection between the suspended signal ground and the earth protection ground wire; The positive DC output of the rectifier and voltage regulator circuit is connected to the power input of the four-quadrant power converter unit, the differential error amplifier unit, and the embedded Kelvin sensing circuit. One end of the precision sampling resistor in the embedded Kelvin sensing circuit is connected to the floating signal ground, and the signal reference terminal of the differential error amplification unit is connected to the floating signal ground.

10. A calibration method for an efficient electrical measuring instrument calibration system according to any one of claims 1-9, characterized in that, The method includes the following steps: S100, the central control unit configures the phase relationship and operating mode of multiple distributed active servo nodes according to the wiring system parameters of the electrical measuring instrument under test; S200: The central low-power reference source generates an analog standard reference signal and transmits the analog standard reference signal to the differential error amplification unit of the distributed active servo node through the fluxgate isolation interface. The embedded Kelvin sensing circuit inside the S300 distributed active servo node acquires the terminal voltage feedback signal at the input terminal of the electrical measuring instrument under test through the voltage sensing line. S400, The differential error amplification unit calculates the difference between the analog standard reference signal and the terminal voltage feedback signal, and uses a proportional-integral-derivative controller to generate a voltage correction command signal; The S500 four-quadrant power converter unit outputs a drive voltage according to the voltage correction command signal. The voltage drop generated by the power drive line during the transmission of the drive voltage to the electrical instrument under test is automatically compensated, so that the actual potential at the input terminal of the electrical instrument under test tracks the analog standard reference signal.

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