CN213934043U - Power capacitor's test system - Google Patents

Abstract

Embodiments of the present disclosure relate to a test system of a power capacitor. The test system includes: an energy storage power supply configured to provide a large capacity required for measuring a power capacitor, including a plurality of parallel-connected branches, each branch including a power cell connected in series; an isolation unit configured to isolate the energy storage power supply from the power capacitor during a period when the test is not performed; a measurement unit configured to measure a voltage across the power capacitor and a current flowing through the power capacitor during the test; and an analysis unit configured to analyze the voltage and the current. The test system provided by the invention can provide large capacity required by the power capacitor test, and avoids the inconvenience of needing a compensation reactor when the existing large-capacity power capacitor is tested.

Description

Power capacitor's test system

Technical Field

Embodiments of the present invention generally relate to a test system for power capacitors, and more particularly, to a test system for high capacity power capacitors.

Background

The capacity measurement of the power capacitor is required to be carried out under rated voltage, and usually very high test capacity is required, and the test capacity is required to reach thousands of kVA by taking the power capacitor with the rated voltage of 10kV as an example. According to the traditional test method, after the voltage of a 380V power supply is regulated by a voltage regulator, the voltage is boosted to a tested capacitor by a small-capacity booster transformer. Because the test capacity exceeds the power supply capacity, reactors need to be connected in parallel at two ends of the capacitor to compensate the problem of insufficient capacity of the power supply. Due to the fact that the capacitor capacity and the voltage are various, the needed compensating reactor is very complicated, and the test process is very inconvenient.

Disclosure of Invention

Embodiments of the present disclosure provide a test system for a power capacitor, which can provide a large capacity required for a power capacitor test, thereby at least partially solving the above-mentioned problems in the prior art.

In a first aspect of the present disclosure, a test system for a power capacitor is provided. The test system includes: an energy storage power supply coupled to the three-phase input power supply, the energy storage power supply configured to be used for providing a large capacity required for measuring the power capacitor, the energy storage power supply comprising a plurality of parallel-connected branches, each branch comprising series-connected power units, each power unit being a high-power plug-in structure comprising a rectifying unit, an energy storage element and an inverting unit connected in sequence, and each power unit being coupled to the input unit, wherein: an input unit coupled to a three-phase input power source, configured to convert the three-phase input into an input suitable for an energy storage power source; a rectifying unit coupled to the input unit and configured to rectify the three-phase input into direct current; an energy storage element coupled to the rectifying unit and configured to store energy received from the rectifying unit; an inversion unit coupled to the energy storage element and configured to convert the direct current into an alternating current; an isolation unit disposed between an output of the energy storage power supply and the power capacitor, the isolation unit configured to isolate the energy storage power supply from the power capacitor during a period in which the test is not performed; the filtering unit is coupled to the isolation unit and configured to filter out higher harmonics in the output of the energy storage power supply; a measurement unit coupled to the power capacitor, the measurement unit configured to measure a voltage across the power capacitor and a current flowing through the power capacitor during the test; and an analysis unit coupled to the measurement unit, the analysis unit configured to analyze the voltage and the current, wherein the energy storage power supply, the isolation unit, the measurement unit, and the analysis unit are integrated in the case.

According to the embodiment of the disclosure, a large-capacity test system required by a power capacitor test is provided, and inconvenience that a compensation reactor is required when the existing large-capacity power capacitor is tested is avoided.

In one embodiment, the input unit is a three-phase transformer. In such an embodiment, a three-phase input may be converted to a single-phase output, increasing the output current.

In one embodiment, the rectifying unit comprises six diodes, an anode of the first diode is connected to a cathode of the fourth diode as the first input of the rectifying unit, an anode of the second diode is connected to a cathode of the fifth diode as the second input of the rectifying unit, an anode of the third diode is connected to a cathode of the sixth diode as the third input of the rectifying unit, cathodes of the first, second and third diodes are connected together as the first output of the rectifying unit, and cathodes of the fourth, fifth and sixth diodes are connected together as the second output of the rectifying unit. In such an embodiment, uncontrolled rectification of the three-phase power can be achieved, with the simplest circuitry to achieve conversion of three-phase ac power to dc power.

In one embodiment, the energy storage element is a capacitor. In such embodiments, the energy can be stored for later testing.

In one embodiment, the inverter unit comprises four switching tubes, a drain electrode of a first switching tube and a drain electrode of a second switching tube are connected together to serve as a first input of the inverter unit, a source electrode of a third switching tube and a source electrode of a fourth switching tube are connected together to serve as a second input of the inverter unit, a source electrode of the first switching tube and a drain electrode of the third switching tube are connected together to serve as a first output of the inverter unit, and a source electrode of the second switching tube and a drain electrode of the fourth switching tube are connected together to serve as a second output of the inverter unit. In such an embodiment, the dc power can be reliably inverted to the desired ac power output.

In one embodiment, the isolation unit is an isolation switch. In such an embodiment, the power supply may be isolated from the power capacitor under test to ensure the safety of the circuit.

In one embodiment, the filtering unit is an LC filter. In such an embodiment, higher harmonics of the power supply output voltage can be filtered, so that the output waveform is smoother, and the accurate measurement of the capacity of the power capacitor is facilitated.

In one embodiment, the measurement unit comprises a resistance network configured for measuring a voltage across the power capacitor during the test and a rogowski coil configured for measuring a current flowing through the power capacitor during the test. In such an embodiment, the voltage and current can be measured in a simple manner.

In one embodiment, the analysis unit is a power analyzer. In such an embodiment, the output capacitance current and capacitance voltage measuring device converts the data and sends the converted data to the power analyzer to obtain accurate capacitance capacity parameters.

In one embodiment, the alternating current is greater than or equal to 10 kV. In such an embodiment, testing may be provided for existing power capacitors.

Drawings

The above and other objects, features and advantages of the embodiments of the present disclosure will become more readily understood through the following detailed description with reference to the accompanying drawings. In the drawings, various embodiments of the present disclosure will be described by way of example and not limitation.

Fig. 1 shows a circuit block diagram of a test system for a power capacitor according to an embodiment of the present disclosure.

Fig. 2 shows a block circuit diagram of a power cell according to an embodiment of the present disclosure.

Fig. 3 shows a specific circuit diagram of a power cell according to an embodiment of the present disclosure.

Fig. 4 shows a specific circuit diagram of a storage power supply according to an embodiment of the present disclosure.

Fig. 5 shows a circuit diagram of a test system for a power capacitor according to an embodiment of the present disclosure.

Detailed Description

The principles of the present disclosure will now be described with reference to various exemplary embodiments shown in the drawings. It should be understood that these examples are described merely to enable those skilled in the art to better understand and further implement the present disclosure, and are not intended to limit the scope of the present disclosure in any way. It should be noted that where feasible, similar or identical reference numerals may be used in the figures and that similar or identical reference numerals may indicate similar or identical functions. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.

A circuit configuration of a test system of a power capacitor according to an example embodiment of the present disclosure will be described in detail below with reference to fig. 1 to 5. Referring first to fig. 1, fig. 1 shows a circuit block diagram of a test system for a power capacitor according to an embodiment of the present disclosure.

In the embodiment shown in fig. 1, the test system 1 for power capacitors is adapted to receive and store grid energy when not under test, to provide the voltage and current required for the test for a longer period of time when under test, and to measure and analyze the voltage and current of the power capacitor.

In general, a test system 1 for a power capacitor includes: the energy storage power supply 10, the isolation unit 20, the measurement unit 40 and the analysis unit 50. In some embodiments, the energy storage power supply 10, the isolation unit 20, the measurement unit 40 and the analysis unit 50 are integrated in a box. In some embodiments, the energy storage power source 10, the isolation unit 20, the measurement unit 40 and the analysis unit 50 may be connected to each other in a wired manner, for example, may be connected by a wire. Alternatively, in other embodiments, in order to ensure the safety of the circuit, the connection between the measurement unit 40 and other circuit units, and between the analysis unit 50 and other circuit units may be wireless, for example, may be through optical coupling devices.

The energy storage power supply 10 is configured to receive a three-phase ac input and convert the ac input to an ac output of a desired voltage, current level, and frequency, the magnitude of which may be determined based on experimental objectives. In the capacitance capacity test, the voltage of the power capacitor is up to 10kV, and the current is hundreds or even thousands of amperes. Such high voltage and high current put high demands on the voltage resistance and current carrying capability of the devices in the power supply. In the energy storage power supply 10 of the embodiment, a plurality of power modules 20 are connected in series to form a branch circuit and then connected in parallel, so that the voltage and current levels of devices in each power module are reduced. Each power unit 100 is a high-power plug-in structure and is plugged into the box body, so that the assembly is flexible and convenient. When the maintenance is needed, the plugging and pulling can be carried out, so that the maintenance is convenient for a user.

As shown in fig. 1, an isolation unit 20 is disposed between the output of the energy storage power supply 10 and the measured power capacitor, and the isolation unit 20 is configured to isolate the energy storage power supply 10 from the power capacitor during the period of non-testing, ensuring the safety of the power capacitor, so that the energy absorbed by the voltage unit 10 from the three-phase alternating current input can be stored for applying to the power capacitor in the subsequent testing process. In some embodiments, the isolation unit 20 may be, for example, an isolation switching element, such as a relay or the like. Alternatively, in other embodiments, the isolation unit 20 may be, for example, other types of isolation elements, which may be determined according to specific circuit design requirements and cost.

The measurement unit 40 is coupled to the power capacitor and is configured for measuring a voltage across the power capacitor and a current flowing through the power capacitor during the test. In some embodiments, the measurement unit 40 may detect the voltage across the power capacitor through a resistive voltage division network, and the current flowing through the power capacitor through the rogowski coil, for example, in consideration of cost and measurement accuracy. Alternatively, in other embodiments, the measurement unit 40 may employ other voltage detection circuits and current detection elements, which may be determined according to specific circuit design requirements and cost.

The analyzing unit 50 is connected to an output of the measuring unit 40, and is configured to analyze the voltage and current detected in the measuring unit 40 to find the capacity of the power capacitor. In certain embodiments, the analysis unit 50 may be, for example, a power analyzer. Alternatively, in other embodiments, the analysis unit 50 may be other types of analysis devices, which may be determined according to specific circuit design requirements and cost.

Fig. 2 shows a block circuit diagram of the power unit 100 in the energy storage power supply shown in fig. 1, wherein the power unit 100 is configured to employ an AC/DC/AC type frequency conversion circuit that first converts an alternating input voltage into an intermediate direct voltage and then converts the intermediate direct voltage into a desired alternating output voltage. The circuit topology can simultaneously adjust the amplitude and frequency of the alternating current output voltage and current.

In the embodiment shown in fig. 2, the power unit 100 includes a rectifying unit 102, an energy storage element 103, and an inverting unit 104. Wherein the rectifying unit 102 is configured to convert a three-phase alternating current input into an intermediate direct current, the energy storage element 103 is configured to store energy absorbed from the three-phase alternating current input, and the inverting unit 104 is configured to convert the intermediate direct current into a desired alternating current output.

In some embodiments, to simplify the circuit structure, the rectifying unit 102 may be constructed using an uncontrollable device, for example. Alternatively, in other embodiments, the rectifying unit 102 may also be constructed with fully-controlled devices or semi-controlled devices, or may be constructed with a combination of diodes and thyristors, which may be determined according to specific circuit design requirements and cost.

In some embodiments, the energy storage element 103 may be, for example, a capacitive element. Alternatively, in other embodiments, the energy storage element 103 may employ other energy storage elements, which may be determined based on the voltage level of the circuit and the specific design requirements and costs.

In some embodiments, in order to make the ac output voltage, the amplitude and the frequency of the current adjustable, the inverter unit 104 may be constructed using a fully controlled device, for example.

Fig. 3 shows an example circuit configuration diagram in the power cell 100 shown in fig. 2.

In the embodiment shown in fig. 3, the rectifying unit 102 is configured to uncontrollably full-wave rectify the three-phase ac input voltage. The rectifying unit 102 comprises six diodes D1-D6, wherein the anode of the first diode D1 and the cathode of the fourth diode D4 are connected with the first phase input of the three-phase alternating current input voltage, the cathode of the first diode D1 is connected with the positive output end of the rectifying unit 102, and the anode of the fourth diode D4 is connected with the negative output end of the rectifying unit 102; an anode of the second diode D2 and a cathode of the fifth diode D5 are connected to a second phase input of the three-phase ac input voltage, a cathode of the second diode D2 is connected to a positive output terminal of the rectifying unit 102, and an anode of the fifth diode D5 is connected to a negative output terminal of the rectifying unit 102; an anode of the third diode D3 and a cathode of the sixth diode D6 are connected to a third phase input of the three-phase ac input voltage, a cathode of the third diode D3 is connected to the positive output terminal of the rectifying unit 102, and an anode of the sixth diode D6 is connected to the negative output terminal of the rectifying unit 102.

In some embodiments, diodes D1-D6 may be selected to use the same type of diode, for example, in order to reduce design cost. Alternatively, in other embodiments, diodes D1-D6 may be selected to use different types of diodes, for example, as may be determined by specific circuit design requirements and cost.

In certain embodiments, diodes D1-D6 may be replaced with MOSFETs, for example, to provide controllable rectification of the three-phase AC input voltage. Alternatively, in other embodiments, the diodes D1-D6 may be replaced with other types of switching devices, for example, as may be determined by specific circuit design requirements and cost.

An energy storage element capacitor C1 is connected between the positive and negative output terminals of the rectifying unit 102 to store energy absorbed from the grid.

In some embodiments, the capacitor C1 may be replaced with a battery, for example, which may be determined based on specific circuit design requirements and cost.

The inverting unit 104 is configured to perform full-bridge inversion on the intermediate dc voltage. The inverter unit 104 comprises four IGBTs Q1-Q4, the drain of the first IGBT Q1 is connected with the positive output end of the rectifier unit 102, and the source of the first IGBT Q1 is connected with the first output end of the power unit 100; the drain of the second IGBT Q2 is connected to the positive output terminal of the rectifying unit 102, and the source of the second IGBT Q2 is connected to the second output terminal of the power unit 100; the source of the third IGBT Q3 is connected to the negative output terminal of the rectifying unit 102, and the drain of the third IGBT Q3 is connected to the first output terminal of the power unit 100; the source of the fourth IGBT Q4 is connected to the negative output terminal of the rectifying unit 102, and the drain of the fourth IGBT Q4 is connected to the second output terminal of the power unit 100.

In such an embodiment, the first IGBT Q1 and the fourth IGBT Q4 are turned on and off simultaneously, the second IGBT Q2 and the third IGBT Q3 are turned on and off simultaneously, and the first IGBT Q1 and the second IGBT Q2 are turned on and off complementarily, when an SPWM pulse signal is applied to the IGBT control electrode, a single-phase sine wave pulse width modulation output voltage can be obtained at the output terminal, a total output voltage obtained by multiplying the number of cells by the cell voltage can be obtained when a plurality of cells are cascaded, so that an intermediate dc voltage can be inverted into a desired ac output voltage, and by controlling the duty ratios of the IGBTs Q1-Q4, the amplitude and frequency of the ac output voltage and the amplitude of the output current can be adjusted to continuously supply the voltage and current required by the power capacitor.

In some embodiments, to reduce design cost, the IGBTs Q1-Q4 may choose to use the same type of IGBT, for example. Alternatively, in other embodiments, the IGBTs Q1-Q4 may choose to use different types of IGBTs, for example, which may be determined by specific circuit design requirements and cost.

In certain embodiments, the IGBTs Q1-Q4 may be replaced with MOSFETs, for example, for voltage class and power consumption considerations. Alternatively, in other embodiments, the IGBTs Q1-Q4 may be replaced with other types of switching devices, for example, as may be determined by specific circuit design requirements and cost.

In certain embodiments, the IGBTs Q1-Q4 may be reduced to 2, for example, to provide half-bridge inversion of the intermediate DC voltage, which may be determined by specific circuit design requirements and cost.

Fig. 4 shows an example circuit configuration diagram of the energy storage power supply 10 shown in fig. 1.

In the embodiment shown in fig. 4, the energy storage power supply 10 includes a plurality of branches formed by serially connecting the power cells 100, and the branches are connected in parallel to obtain the final energy storage power supply 10. By connecting the plurality of power units 100 in series, the withstand voltage level of the branch is improved, and by connecting the plurality of branches in parallel, the current carrying capacity of the energy storage power supply 10 is improved. The number of power cells 100 in each branch may be selected according to the required voltage class and the withstand voltage value of the power device, and the number of branches may be determined according to the required current class and the current class of the power device. Each power unit 100 is connected to the grid through an input unit 101.

As shown in fig. 4, a 380V three-phase ac power supply supplies power to a transformer T1 after passing through a power inlet switch K1, the transformer is a multi-winding step-up transformer, the stepped-up voltage is rectified and then charges an energy storage capacitor C1, the electric energy stored in the capacitor C1 is converted by an inverter and is superposed in series by multiple cells, and a multi-level SPWM voltage is output for the tested power capacitor.

In some embodiments, the energy storage power supply 10 is capable of continuously outputting the rated voltage and rated current of the power capacitor, for example, the output voltage is 10kV and the output current is 500 amperes. Alternatively, in other embodiments, other values of current may be output, which may be determined based on specific circuit design requirements and cost.

In some embodiments, the input unit 101 may be, for example, a three-phase transformer that converts a three-phase input voltage from the grid to be suitable for the input of the power unit 100.

According to the embodiment of the disclosure, through the series-parallel connection of the power units 100, the current and the voltage required by the capacity test of the capacitor can be obtained, and the impact of the capacity test of the power capacitor directly connected to the power grid on the power grid is avoided.

Fig. 5 shows a circuit diagram of a test system for a power capacitor according to an embodiment of the present disclosure.

In the embodiment shown in fig. 5, the power capacitor is connected at the output of the test system. When the test is not performed, the isolating switch is turned off, and the energy storage power supply receives energy from the three-phase alternating current input and stores the energy in an energy storage element in the energy storage power supply. This stage can be regarded as the charging process of energy storage component, can not produce the impact to the electric wire netting. When a capacitance capacity test is required, firstly, a switch K1 in an energy storage power supply is closed to charge an energy storage capacitor C1, after the charging is finished, K1 is disconnected, an isolating switch is closed, the driving waveform of each inversion unit is adjusted so as to obtain a proper output voltage, the phase angle and the frequency of a modulation signal are set, a high-voltage power supply meeting the frequency and phase requirements can be obtained, a period of time is continuously output, the voltages at two ends of a power capacitor are measured through a resistance network, the current flowing through the power capacitor is measured through a Rogowski coil, and a voltage value and a current value are analyzed through a power analyzer so as to obtain the capacitance value of the power capacitor, so that the primary power capacitor capacity test can be finished. Because the capacity test of the power capacitor is completed by the energy storage capacitor C1, the power capacitor can not generate any impact on the power grid. For a 10kV power capacitor, the capacity taken by the energy storage power supply from the power supply side is much smaller than the capacity taken directly from the power supply side. Because the power electronic conversion technology is adopted, the amplitude and the phase of the output voltage can be quickly adjusted, constant voltage power supply can be realized, and the capacity test experiment of the power capacitor can be conveniently realized. The equipment adopts automatic constant voltage output, and the power supply can adjust the phase of output voltage to any angle.

According to the embodiment of the disclosure, the power output of up to tens of thousands of kVA can be continuously provided to test the capacity of the power capacitor, and the impact of such test directly connected to the power grid on the power grid is avoided.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same aspect as presently claimed in any claim. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims (10)

1. A test system for a power capacitor, the test system comprising:

an energy storage power supply (10) coupled to a three-phase input power supply, the energy storage power supply (10) being configured for providing a capacity required for measuring the power capacitor, the energy storage power supply (10) comprising a plurality of parallel-connected branches, each branch comprising a series-connected power unit (100), each power unit (100) being a high-power plug-in structure comprising a rectifying unit (102), an energy storage element (103) and an inverting unit (104) connected in sequence, and each power unit being coupled to an input unit (101), wherein:

the input unit (101), coupled to the three-phase input power source, configured to convert a three-phase input into an input suitable for the energy storage power source (10);

the rectifying unit (102), coupled to the input unit (101), configured to rectify a three-phase input into a direct current;

the energy storage element (103) coupled to the rectifying unit (102) configured to store energy received from the rectifying unit (102);

the inverter unit (104), coupled to the energy storage element (103), configured to convert the direct current into an alternating current;

an isolation unit (20) arranged between an output of the energy storage power supply (10) and the power capacitor, the isolation unit (20) being configured for isolating the energy storage power supply (10) from the power capacitor during periods when no testing is performed;

a filtering unit (30), coupled to the isolation unit (20), configured to filter out higher harmonics in the output of the energy storage power supply (10);

a measurement unit (40) coupled to the power capacitor, the measurement unit (40) being configured for measuring a voltage across the power capacitor and a current flowing through the power capacitor during a test; and

an analyzing unit (50) coupled to the measuring unit (40), the analyzing unit (50) being configured for analyzing the voltage and the current,

wherein the energy storage power supply (10), the isolation unit (20), the measurement unit (40) and the analysis unit (50) are integrated in a housing.

2. The test system according to claim 1, wherein the input unit (101) is a phase shifting transformer (T1).

3. The test system according to claim 1, wherein the rectifying unit (102) comprises six diodes (D1-D6), an anode of a first diode (D1) being connected to a cathode of a fourth diode (D4) as a first input of the rectifying unit (102), an anode of a second diode (D2) being connected to a cathode of a fifth diode (D5) as a second input of the rectifying unit (102), an anode of a third diode (D3) being connected to a cathode of a sixth diode (D6) as a third input of the rectifying unit (102), cathodes of the first diode (D1), the second diode (D2) and the third diode (D3) being connected together as a first output of the rectifying unit (102), cathodes of the fourth diode (D4), the fifth diode (D5) and the sixth diode (D6) being connected together as a cathode of the rectifying unit (102) And (6) outputting.

4. The test system according to claim 1, wherein the energy storage element (103) is a capacitor (C1).

5. The test system of claim 1, wherein the inverter unit (104) comprises four switching tubes (Q1-Q4), a drain of a first switching tube (Q1) and a drain of a second switching tube (Q2) are connected together as a first input of the inverter unit (104), a source of a third switching tube (Q3) and a source of a fourth switching tube (Q4) are connected together as a second input of the inverter unit (104), a source of the first switching tube (Q1) and a drain of the third switching tube (Q3) are connected together as a first output of the inverter unit (104), and a source of the second switching tube (Q2) and a drain of the fourth switching tube (Q4) are connected together as a second output of the inverter unit (104).

6. The test system according to claim 1, wherein the isolation unit (20) is an isolation switch.

7. The test system according to claim 1, wherein the filter unit (30) is an LC filter.

8. The test system according to claim 1, wherein the measurement unit (40) comprises a resistance network and a rogowski coil, wherein the resistance network is configured for measuring the voltage across the power capacitor during testing and the rogowski coil is configured for measuring the current flowing through the power capacitor during testing.

9. The test system according to claim 1, wherein the analysis unit (50) is a power analyzer.

10. The test system of claim 1, wherein the alternating current is greater than or equal to 10 kV.

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