CN104181490A - Large-current transient state characteristic detection device of electronic current transformer - Google Patents
Large-current transient state characteristic detection device of electronic current transformer Download PDFInfo
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- 238000004146 energy storage Methods 0.000 claims description 31
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Abstract
The invention provides a large-current transient state characteristic detection device of an electronic current transformer. The large-current transient state characteristic detection device comprises a controller unit, a transformer, a direct-current charging power supply and waveform output units connected with an ECT test product. The waveform output units include a steady state waveform output unit and a transient state waveform output unit, the controller unit comprises a charging control module, a phase-selection switching-on control module, a waveform monitoring module and a waveform adjustment module, and the controller unit outputs signals for adjusting work states to electronic devices in the waveform output units so as to control the waveform output units to output steady state waveforms and transient state waveforms to the ECT test product. Compared with the prior art, the large-current transient state characteristic detection device of the electronic current transformer can accurately adjust current peak values and attenuation time constants of output transient state voltage waveforms and output transient state current waveforms, and accordingly detection requirements of electronic current transformer test products of different models are met.
Description
Technical Field
The invention relates to a detection device for an electronic current transformer, in particular to a detection device for the large current transient characteristic of the electronic current transformer.
Background
Transient tests of the electronic current transformer comprise a direct method and an equal ampere-turn method. The direct method is used for testing through a high-capacity current source with a phase selection and closing function, and meanwhile, the requirement of a primary loop on a time constant is required to be met in the testing process. However, at present, no facility for carrying out long-time large-current transient test on the current transformer is provided; if the transient test cannot be carried out when the rated current is 2kA and the symmetrical short-circuit current is 40kA, the inventor of the invention finds that the prior art which can meet the transient error test requirement of the extra-high voltage power grid current transformer does not exist at present through long-term and large-scale observation and research.
In the transient test process of the electronic current transformer, because the primary current is too large, the stable primary rated test current is difficult to directly generate in the product delivery inspection, the laboratory inspection and the inspection under the field connection environment. Therefore, the method of uniformly winding equal ampere turns on a primary conductor is adopted, a plurality of turns of coils are uniformly wound on the test coil along the circumferential direction by using a flexible lead to serve as a primary equal ampere turn coil, and a single turn of small current can generate equivalent primary large current to serve as a test power supply through the equal ampere turns. The equal ampere-turn method is suitable for factory tests of large-current transformers, field handover tests of large-capacity GIS (gas insulated switchgear) matched current transformers and field verification of GTAs (gas insulated switchgear), but measurement errors of the equal ampere-turn method and measurement errors of a direct method deviate in the process of carrying out error tests on the current transformers.
The direct analysis method and the equal ampere-turn method show that the test deviation is caused by the current transformers at the metering level and the measuring level; the magnetic density value of the iron core of the metering level current transformer and the magnetic density value of the iron core of the measuring level current transformer are higher than that of the iron core of the protection level current transformer, and the sectional area of the iron core is smaller. When the electronic current transformer actually operates, the primary bus is arranged at the central position of the current transformer, the magnetic field generated by primary current is uniformly distributed in the iron core, and the error performance meets the design requirement. When an equivalent error test is carried out by adopting an equal ampere-turn method, although a plurality of turns of primary leads are distributed on the circumference of a winding equally, the generated magnetic field is uniform in segmentation on the whole, the magnetic field near the plane of each turn of coil is strongest, so that the local magnetic density of the corresponding iron core is increased, even local magnetic saturation occurs, the iron loss is increased, the primary exciting current is increased, and finally the error of the current transformer also correspondingly generates deviation. Therefore, the ineffectiveness problem of the direct method and the equal ampere-turn method is improved by properly increasing the iron core section of the current transformer, reducing the magnetic density value, increasing the shielding winding, optimizing the arrangement of the primary lead and the like.
In the synthesis test of the electronic current transformer, besides the equal ampere-turn method is adopted to realize the output of primary large current, the synthesis of steady-state power frequency current and direct current transient current is carried out, and fault current meeting the standard requirement is output; therefore, it is important to provide a transient characteristic detection device capable of accurately adjusting important parameters of the electronic current transformer, such as a transient current peak value, a decay time constant, and the like.
Disclosure of Invention
In order to meet the needs of the prior art, the invention provides a high-current transient characteristic detection device of an electronic current transformer, which comprises a controller unit, a voltage detection unit and a voltage detection unit, wherein the controller unit comprises a transformer, a direct-current charging power supply and a waveform output unit connected with an ECT (emission computed tomography) test article; the waveform output unit comprises a steady-state waveform output unit and a transient-state waveform output unit;
the controller unit comprises a charging control module, a phase selection and closing control module, a waveform monitoring module and a waveform adjusting module;
the controller unit outputs a signal for adjusting the working state to the electronic device in the waveform output unit so as to control the waveform output unit to output a steady-state waveform and a transient-state waveform to the ECT test sample.
Preferably, the steady-state waveform output unit is connected to a power frequency component loop of the ECT test sample and outputs an alternating current waveform and an alternating current waveform to the power frequency component loop;
the transient waveform output unit is connected to a transient component loop of the ECT test article and outputs a transient voltage waveform and a transient current waveform to the transient component loop;
preferably, the steady-state waveform output unit comprises a current booster unit connected with the transformer; one output end of the current booster unit is directly connected to a power frequency component loop of the ECT test sample, and the other end of the current booster unit is connected to the power frequency component loop through the bidirectional thyristor, the current sensor and the low-inductance current divider in sequence;
the current rising device unit comprises a voltage regulator connected with the transformer and a compensation capacitor connected between the voltage regulator and the current rising device;
preferably, the transient waveform output unit includes a charging thyristor, a double-throw switch, a discharging thyristor, an adjustable resistor and an adjustable inductor connected to the positive terminal of the dc charging power supply; the low-inductance shunt is connected with the negative end of the direct current charging power supply;
preferably, the freewheeling diode is reversely connected in parallel at two ends of the direct current charging power supply; one end of the freewheeling diode is connected between the discharge thyristor and the adjustable resistor, and the other end of the freewheeling diode is connected between the negative pole end of the direct-current charging power supply and the low-inductance current divider;
preferably, the number of the charging thyristors, the double-throw switches and the discharging thyristors is 2; a series branch of the charging thyristor, the double-throw switch and the discharging thyristor is connected between the positive terminal of the direct-current charging power supply and the adjustable resistor; the other series branch of the charging thyristor, the double-throw switch and the discharging thyristor is also connected between the positive terminal of the direct-current charging power supply and the adjustable resistor;
preferably, the double-throw switch is respectively connected between the negative electrode end of the direct-current charging power supply and the low-inductance shunt through an energy storage capacitor;
when the charging thyristor is connected with the energy storage capacitor through the double-throw switch, the direct-current charging power supply, the charging thyristor and the energy storage capacitor form a charging current loop to charge the energy storage capacitor;
when the discharge thyristor is connected with the energy storage capacitor through the double-throw switch, the discharge thyristor, the energy storage capacitor and the fly-wheel diode form a discharge current loop, and the energy storage capacitor discharges;
preferably, the freewheeling diode is in forward conduction when the voltage zero-crossing polarity of the transient voltage waveform is reversed, so that resonance is stopped when the voltage zero-crossing point is reached, the discharge current is exponentially attenuated, and the output requirement of the transient voltage waveform is met;
preferably, the charging control module is configured to control the double-throw switch to operate so that the charging current loop charges or discharges the energy storage capacitor;
the phase selection switch-on control module is used for controlling the waveform output unit to output a synthesized waveform meeting different phase requirements;
the waveform monitoring module collects the current of the low-inductance current divider of the steady-state waveform output unit and the transient-state waveform output unit so as to monitor the steady-state waveform and the transient-state waveform;
the waveform adjusting module is used for adjusting the adjustable resistance and the adjustable inductance of the transient waveform output unit so as to adjust the transient voltage waveform and the transient current waveform;
preferably, the phase selection switch-on control module comprises a current loop and a digital signal processor; the current loop acquires a current value digital signal sent by a current sensor of the steady-state waveform output unit, a current signal and a voltage signal of the transient-state waveform output unit and a phase set value sent by an upper computer;
the digital signal processor calculates and obtains a power frequency voltage zero point and a current zero point of the waveform output by the steady-state waveform output unit according to the current value digital signal;
and the digital signal processor calculates delay time required by the synthesized waveform meeting the requirement of the phase set value by taking the power frequency voltage zero point and the current zero point as reference points, and the current loop sends action instructions to the double-throw switch and the bidirectional triode thyristor respectively after the delay is finished, so that the synthesized waveform meeting the requirement of the phase set value is output.
Compared with the closest prior art, the excellent effects of the invention are as follows:
1. in the technical scheme of the invention, a direct current charging power supply is adopted to charge an energy storage capacitor, and the magnitude of the transient current output by a transient waveform output unit is controlled by controlling the magnitude of the direct current power supply;
2. according to the technical scheme, the two ends of the direct-current charging power supply are reversely connected with the freewheeling diode in parallel, so that when the voltage zero-crossing polarity in the transient voltage waveform is reversed, the freewheeling diode is conducted in the forward direction, resonance stops at the voltage zero-crossing point, and the transient current waveform and the transient voltage waveform both meet the test requirements;
3. in the technical scheme of the invention, a double-throw switch is adopted to control the conduction or the disconnection of a charging thyristor and a discharging thyristor, thereby realizing the synthesis control of transient current waveform and transient voltage waveform;
4. in the technical scheme of the invention, two charging and discharging thyristors are respectively adopted, so that reclosing control of a large-current synthesis test of the electronic current transformer can be realized;
5. in the technical scheme of the invention, the stable voltage waveform, the stable current waveform, the transient current waveform and the transient voltage waveform are accurately adjusted by adopting the adjustable resistor and the adjustable inductor;
6. in the technical scheme of the invention, the current obtained from the transformer can be boosted by the current boosters, each current booster can independently output current of hundreds of amperes, and a plurality of current boosters are combined to output large current to meet the requirement of a monitoring device;
7. in the technical scheme of the invention, the conduction of alternating current in a stable waveform can be realized by adopting the bidirectional thyristor.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of: the invention discloses a structure diagram of a large-current transient characteristic detection device of an electronic current transformer;
FIG. 2 is a diagram of: the operating principle of the freewheeling diode D5 in fig. 1;
FIG. 3 is a diagram of: fig. 1 is a diagram of a transient waveform output unit;
FIG. 4 is a diagram of: the resonant waveform of fig. 1 with the storage capacitor discharged when freewheeling diode D5 is latched;
FIG. 5 is a diagram of: FIG. 4 is a partial enlarged view of the resonant waveform plot;
FIG. 6 is a diagram of: the resonant waveform of fig. 1 with the storage capacitor discharged when freewheeling diode D5 is conducting;
FIG. 7 is a diagram of: the phase selection closing control module in the embodiment of the invention works in a schematic diagram.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The structure of the large-current transient characteristic detection device of the electronic current transformer provided in the embodiment is shown in fig. 1, and the detection device comprises a controller unit, a transformer, a direct-current charging power supply and a waveform output unit;
1. as shown in fig. 1, the waveform output unit includes a steady-state waveform output unit and a transient-state waveform output unit; the steady-state waveform output unit is connected with the transformer and a power frequency component loop of the ECT test article and outputs AC voltage waveform and AC current waveform to the power frequency component loop; the transient waveform output unit is connected with the direct-current charging power supply and a transient component loop of the ECT test product, and outputs a transient voltage waveform and a transient current waveform to the transient component loop;
(1) a steady-state waveform output unit;
as shown, the steady state waveform output unit comprises a current booster unit, a bidirectional thyristor, a current sensor CT and a low-inductance shunt L2; a voltage regulator of the current rising device unit is connected with a secondary side winding of the transformer, and a compensation capacitor is connected between the voltage regulator and the current rising device;
(2) a transient waveform output unit;
the method comprises the following steps: as shown in fig. 2, the transient waveform output unit is connected between the dc charging power supply and the ECT test product, and includes: charging thyristors D1 and D2, discharging thyristors D3 and D4, a freewheeling diode D5, double-throw switches K1 and K2, adjustable resistors of energy storage capacitors C1 and C2, an adjustable inductor and a low-inductance current divider;
the charging thyristor D1, the double-throw switch K1, the discharging thyristor D3, the adjustable resistor and the adjustable inductor are sequentially connected between the positive end of the direct-current charging power supply and the ECT test sample; the charging thyristor D2, the double-throw switch K2, the discharging thyristor D4, the adjustable resistor and the adjustable inductor are also sequentially connected between the positive end of the direct-current charging power supply and the ECT test sample;
the fly-wheel diode D5 is reversely connected in parallel at two ends of the direct current charging power supply, the reverse end of the fly-wheel diode D5 is respectively connected with the reverse end of the discharge thyristor, and the forward end of the fly-wheel diode D5 is connected with the negative end of the direct current charging power supply;
double-throw switches K1 and K2 are connected between the DC charging power supply and the low-inductance shunt through energy storage capacitors C1 and C2, respectively.
Secondly, the step of: the transient waveform output unit comprises a charging current loop and a discharging current loop, and specifically comprises:
when the double-throw switch K1 is connected with the charging thyristor D1 and the double-throw switch K2 is connected with the charging thyristor D2, the direct-current charging power supply, the charging thyristor, the double-throw switch and the energy storage capacitor form a charging current loop to charge the energy storage capacitor;
when the double-throw switch K1 is connected with the discharge thyristor D3 and the double-throw switch K2 is connected with the discharge thyristor D4, the discharge thyristor, the double-throw switch, the energy storage capacitor and the fly-wheel diode form a charging current loop at the moment, and the energy storage capacitor discharges;
fig. 3 shows the operating principle of the freewheeling diode D5 in the discharging current loop, wherein the freewheeling diode D5 functions as:
(1) when the transient waveform output unit is in a discharge current loop state, current flows into the circuit to protect electronic devices in the circuit.
(2) When the transient waveform output unit is in a discharge current loop state, the freewheeling diode D5 is conducted in the forward direction when the voltage zero-crossing polarity of the transient voltage waveform is reversed, so that resonance is stopped when the voltage zero-crossing point is reached, the discharge current is exponentially attenuated, and the output requirement of the transient voltage waveform is met;
firstly, the double-throw switch K in FIG. 2 comprises double-throw switches K1 and K2, and the energy storage capacitor C comprises energy storage capacitors C1 and C2; when the double-throw switch K is connected with the discharge thyristor, the energy storage capacitor, the adjustable resistor R1 and the adjustable inductor L form a typical RLC second-order circuit, and the RLC second-order circuit is an underdamped second-order circuit because the adjustable resistor is a milliohm-level resistor; fig. 4 shows the transient voltage waveform and the transient current waveform output by the waveform output unit when the energy storage capacitor discharges to the adjustable resistor and the adjustable inductor, wherein the two waveforms are gradually attenuated because the RLC second-order circuit is an underdamped second-order circuit;
secondly, the transient voltage waveform and the transient current waveform shown in fig. 4 do not meet the waveform output requirements of the test of the embodiment, and the waveforms after the first peak of the transient voltage waveform and the transient current waveform have long oscillation time and poor stability; in an actual large-current synthesis test of the electronic current transformer, the size of a first peak value and the waveform time length after the first peak value are set according to the electronic current transformers with different voltage levels. Through the graph 5, it can be determined that when the voltage of the transient voltage waveform crosses zero, the resonance current of the transient current waveform reaches the maximum value, and if the resonance is stopped at this time, the discharge current exponentially decays with a certain time constant, so that the transient current waveform meets the test requirements;
when the voltage zero-crossing polarity of the transient voltage waveform is reversed, the freewheeling diode D5 is conducted in the forward direction, the energy storage capacitor is short-circuited, the resonance condition is damaged, the resonance stops at the voltage zero-crossing point, the RLC second-order circuit is converted into the RL first-order circuit at the moment, as shown in FIG. 6, the transient current waveform is attenuated according to the zero input response of the RL first-order circuit after the current reaches the maximum value, and the transient current waveform meets the test requirement;
wherein, the resonance current refers to the discharge current released by the energy storage capacitor.
(3) A controller unit;
the controller unit outputs a signal for adjusting the working state to the electronic device in the waveform output unit so as to control the waveform output unit to output a steady-state waveform and a transient-state waveform to the ECT test sample; as shown in fig. 1, the system comprises a charging control module, a phase selection and closing control module, a waveform monitoring module and a waveform adjusting module, and specifically comprises:
the method comprises the following steps: the charging control module controls the double-throw switches K1 and K2 to act simultaneously, the double-throw switch K1 is connected with the charging thyristor D1, the double-throw switch K2 is connected with the charging thyristor D2, and the direct-current charging power supply charges the energy storage capacitors C1 and C2 respectively; the charging control module collects charging voltage and charging current in real time through the collecting board and sends the charging voltage and the charging current to the upper computer, the upper computer compares the charging voltage with a voltage set value and compares the charging current with a current set value, and if the charging voltage and the charging current meet the requirements of the set values, the upper computer controls and sends a discharging instruction to the charging control module; the control module that charges controls double-throw switch and carries out reclosing includes:
a. after the double-throw switch K1 is connected with the discharge thyristor D3, the double-throw switch K2 is connected with the discharge thyristor D4;
b. after the double-throw switch K2 is connected with the discharge thyristor D4, the double-throw switch K1 is connected with the discharge thyristor D3.
Secondly, the step of: as shown in fig. 7, the phase selection and closing control module is configured to control the waveform output unit to output a synthesized waveform meeting requirements of different phases; the device comprises a current loop and a digital signal processor;
the current loop is used for a, acquiring a current value digital signal sent by a current sensor CT of the steady-state waveform output unit;
b. collecting a current signal and a voltage signal of a waveform output by a transient waveform output unit; the current signal comprises a current instantaneous value and a current zero point, and the voltage signal comprises a current instantaneous value and a voltage zero point;
c. and receiving a phase set value sent by an upper computer, wherein the phase set value is set by technicians according to actual working condition requirements of different electronic current transformers.
The digital signal processor calculates and obtains a power frequency voltage zero point and a current zero point of the waveform output by the steady-state waveform output unit according to the current value digital signal; meanwhile, the digital signal processor calculates the delay time of the double-throw switch action and the bidirectional thyristor action required by the synthesized waveform meeting the phase set value requirement by taking the power frequency voltage zero point and the current zero point as reference points, and the current ring sends action instructions to the double-throw switch and the bidirectional thyristor respectively after the time delay is finished, so that the synthesized waveform meeting the phase set value requirement is output. And finally, the current loop collects the voltage signal and the current signal of the synthesized waveform and sends the voltage signal and the current signal to an upper computer, so that technicians can conveniently perform fault analysis on the high-current transient characteristic detection device.
③: the waveform monitoring module is used for acquiring the voltage and the current of the low-inductance shunt of the waveform output unit through the DSP circuit and sending the voltage and the current to the upper computer so as to monitor a transient voltage waveform, a transient current waveform, a steady voltage waveform and a steady current waveform; if the waveform output unit generates overvoltage or overcurrent, the detection device stops working;
③: the waveform adjusting module is used for adjusting the adjustable resistance and the adjustable inductance of the transient waveform output unit so as to adjust the transient voltage waveform and the transient current waveform; an operator sends a parameter adjusting instruction to the transient waveform adjusting module according to the voltage signal and the current signal acquired by the upper computer, so that the resistance value of the adjustable resistor and the inductance value of the adjustable inductor are adjusted, circuit parameters are changed remotely, and the peak value and the decay time constant of the transient current are controlled to meet the test requirements.
The zero-input response parameter calculation formula of the RLC underdamped second-order circuit shown in fig. 3 is as follows:
the method comprises the following steps: the transient current calculation formula is as follows: <math>
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secondly, the step of: the time constant calculation formula of the transient current waveform attenuation is as follows:
③: the instantaneous value of the current is calculated by the formula:wherein, I0The peak value of the first peak;
fourthly, the method comprises the following steps: the adjustable inductance voltage has a calculation formula of <math>
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by selecting an appropriate charging voltage UcThe capacity C of the energy storage capacitor, the adjustable inductor L, the adjustable resistor R1 and the discharging closing angle of the direct current loop can accurately adjust the peak value and the attenuation time constant parameter of the transient current so as to meet the requirements of transient detection of electronic current transformers of different models.
Finally, it should be noted that: the described embodiments are only some embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Claims (10)
1. A high-current transient characteristic detection device of an electronic current transformer comprises a controller unit, and is characterized by comprising a transformer, a direct-current charging power supply and a waveform output unit connected with an ECT (emission computed tomography) test article; the waveform output unit comprises a steady-state waveform output unit and a transient-state waveform output unit;
the controller unit comprises a charging control module, a phase selection and closing control module, a waveform monitoring module and a waveform adjusting module;
the controller unit outputs a signal for adjusting the working state to the electronic device in the waveform output unit so as to control the waveform output unit to output a steady-state waveform and a transient-state waveform to the ECT test sample.
2. The detection device according to claim 1, wherein the steady-state waveform output unit is connected to a power frequency component loop of the ECT sample, and outputs an alternating current waveform and an alternating current waveform to the power frequency component loop;
and the transient waveform output unit is connected to the transient component loop of the ECT test article and outputs a transient voltage waveform and a transient current waveform to the transient component loop.
3. The detection apparatus of claim 1, wherein the steady state waveform output unit comprises a current booster unit connected to the transformer; one output end of the current booster unit is directly connected to a power frequency component loop of the ECT test sample, and the other end of the current booster unit is connected to the power frequency component loop through the bidirectional thyristor, the current sensor and the low-inductance current divider in sequence;
the current rising unit comprises a voltage regulator connected with the transformer and a compensation capacitor connected between the voltage regulator and the current rising unit.
4. The detection device according to claim 1, wherein the transient waveform output unit includes a charging thyristor, a double throw switch, a discharging thyristor, an adjustable resistor and an adjustable inductor connected to a positive terminal of the dc charging power supply; and the low-inductance shunt is connected with the negative electrode end of the direct current charging power supply.
5. The detection device according to claim 4, wherein a freewheeling diode is connected in anti-parallel across the DC charging power supply; one end of the freewheeling diode is connected between the discharge thyristor and the adjustable resistor, and the other end of the freewheeling diode is connected between the negative pole end of the direct-current charging power supply and the low-inductance current divider.
6. The detection apparatus according to claim 4, wherein the number of the charging thyristors, the double throw switches, and the discharging thyristors is 2; a series branch of the charging thyristor, the double-throw switch and the discharging thyristor is connected between the positive terminal of the direct-current charging power supply and the adjustable resistor; and the other series branch of the charging thyristor, the double-throw switch and the discharging thyristor is also connected between the positive terminal of the direct-current charging power supply and the adjustable resistor.
7. The detection device as claimed in claim 6, wherein the double-throw switches are respectively connected between the negative terminal of the DC charging power supply and the low-inductance current divider through energy storage capacitors;
when the charging thyristor is connected with the energy storage capacitor through the double-throw switch, the direct-current charging power supply, the charging thyristor and the energy storage capacitor form a charging current loop to charge the energy storage capacitor;
when the discharging thyristor is connected with the energy storage capacitor through the double-throw switch, the discharging thyristor, the energy storage capacitor and the fly-wheel diode form a discharging current loop, and the energy storage capacitor discharges.
8. The detector according to claim 7, wherein the freewheeling diode is forward-conducting when the voltage zero-crossing polarity of the transient voltage waveform is reversed, so that the resonance stops at the voltage zero-crossing point, and the discharge current exponentially decays to meet the output requirement of the transient voltage waveform.
9. The detection device as claimed in claim 1 or 7, wherein the charging control module is configured to control the double-throw switch to operate such that the charging current loop charges or discharges the energy storage capacitor;
the phase selection switch-on control module is used for controlling the waveform output unit to output a synthesized waveform meeting different phase requirements;
the waveform monitoring module collects the current of the low-inductance current divider of the steady-state waveform output unit and the transient-state waveform output unit so as to monitor the steady-state waveform and the transient-state waveform;
and the waveform adjusting module is used for adjusting the adjustable resistance and the adjustable inductance of the transient waveform output unit so as to adjust the transient voltage waveform and the transient current waveform.
10. The detection device of claim 9, wherein the phase selection switch-on control module comprises a current loop and a digital signal processor; the current loop acquires a current value digital signal sent by a current sensor of the steady-state waveform output unit, a current signal and a voltage signal of the transient-state waveform output unit and a phase set value sent by an upper computer;
the digital signal processor calculates and obtains a power frequency voltage zero point and a current zero point of the waveform output by the steady-state waveform output unit according to the current value digital signal;
and the digital signal processor calculates delay time required by the synthesized waveform meeting the requirement of the phase set value by taking the power frequency voltage zero point and the current zero point as reference points, and the current loop sends action instructions to the double-throw switch and the bidirectional triode thyristor respectively after the delay is finished, so that the synthesized waveform meeting the requirement of the phase set value is output.
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