Voltage waveform generating circuit

Abstract

The invention provides a voltage waveform generating circuit. The voltage waveform generating circuit comprises a harmonic voltage generating unit and a power frequency voltage generating unit which are connected in parallel. The mutual interference between the second harmonic voltage of the harmonic voltage generation unit and the second power frequency voltage output by the power frequency voltage generation unit can be greatly reduced, and then the voltage (namely the second power frequency voltage and the second harmonic voltage) output by the voltage waveform generation circuit can meet the scene requirement. Meanwhile, the superposition of the second power frequency voltage and the second harmonic voltage of various frequencies can be realized, so that the tedious process of replacing or adjusting settings for multiple times when a single harmonic generator is used is avoided, the working efficiency of the voltage waveform generation circuit is improved, and the performance of the power equipment can be evaluated more comprehensively.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a voltage waveform generating circuit. Background Art

[0002] With the development of new energy power generation technology and the construction of new smart grids, the complexity of equipment in each link of the power grid has increased, especially the large-scale investment of some large-capacity and nonlinear loads, which has led to the prominent harmonic problem in the power grid. Harmonics contain many high-frequency components, which are often accompanied by related insulation problems of power equipment, and may cause accidents such as premature damage to power equipment. Therefore, studying the impact of power frequency voltage superimposed on the insulation of power equipment, especially the insulation life and reliability of medium-voltage power cables, is of great significance for timely judging the insulation status of cables, preventing accidents, and ensuring the safe and reliable operation of power grids.

[0003] In the voltage waveform generating circuit provided by the related technology, the generator for generating harmonic voltage is connected in series with the generator for generating industrial frequency voltage. The harmonic voltage and the industrial frequency voltage will interfere with each other, resulting in the voltage output by the voltage waveform generating circuit (that is, the industrial frequency voltage superimposed on the harmonic voltage) not meeting the scenario requirements. In other words, the voltage waveform generating circuit provided by the related technology has low reliability. Summary of the invention

[0004] In order to solve the problem of low reliability in the prior art, the present application provides a voltage waveform generating circuit, which may include a harmonic voltage generating unit and an industrial frequency voltage generating unit connected in parallel.

[0005] The harmonic voltage generating unit is used to generate a first harmonic voltage, transform the voltage level of the first harmonic voltage, and output a second harmonic voltage. The second harmonic voltage is used to indicate the first harmonic voltage after the voltage level transformation.

[0006] The power frequency voltage generating unit is used to generate a first power frequency voltage, transform the voltage level of the first power frequency voltage and output a second power frequency voltage. The second power frequency voltage is used to indicate the first power frequency voltage after the voltage level transformation.

[0007] In some possible implementations, the harmonic voltage generating unit includes a first signal generator, a power amplifier, and a high-frequency transformer.

[0008] The first end of the first signal generator is connected to the first end of the power amplifier, the second end of the power amplifier is used to connect to the first end of the primary winding in the high-frequency transformer, and the second end of the primary winding in the high-frequency transformer is connected to the second end of the first signal generator; the first end of the secondary winding in the high-frequency transformer serves as the output end of the harmonic voltage generating unit, and the second end of the secondary winding in the high-frequency transformer is connected to the ground end.

[0009] Optionally, the first signal generator is used to: generate a first harmonic voltage and transmit it to a power amplifier;

[0010] The power amplifier is used to: amplify the first harmonic voltage and transmit it to the high-frequency transformer;

[0011] The high frequency transformer is used to transform the voltage level of the amplified first harmonic voltage and output the second harmonic voltage.

[0012] Optionally, the harmonic voltage generating unit further includes a first filter capacitor; a first end of the first filter capacitor is connected to a first end of a secondary winding in the high-frequency transformer, and a second end of the first filter capacitor serves as an output end of the harmonic voltage generating unit.

[0013] The first filter capacitor is used to output the second harmonic voltage and prevent the second power frequency voltage from entering the first signal generator through the high frequency transformer.

[0014] Exemplarily, the harmonic voltage generating unit further includes a second filter capacitor; a first end of the second filter capacitor is connected to the power amplifier, and a second end of the second filter capacitor is connected to a first end of a primary winding in a high-frequency transformer;

[0015] The second filter capacitor is used to adjust the phase of the first harmonic voltage.

[0016] The capacitance of the first filter capacitor is in the range of 0.58nF to 0.7nF, and the capacitance of the second filter capacitor is less than or equal to 1.13mF.

[0017] In another possible implementation, the power frequency voltage generating unit includes a second signal generator, a power frequency transformer and a filtering unit.

[0018] The first end of the second signal generator is connected to the first end of the primary winding in the industrial frequency transformer, the second end of the second signal generator is connected to the second end of the primary winding in the industrial frequency transformer, the first end of the secondary winding in the industrial frequency transformer is connected to the first end of the filter unit, the second end of the secondary winding in the industrial frequency transformer is connected to the ground end, and the second end of the filter unit serves as the output end of the industrial frequency voltage generating unit.

[0019] Optionally, the second signal generator is used to generate a first power frequency voltage and transmit it to a power frequency transformer.

[0020] The power frequency transformer is used to transform the voltage level of the first power frequency voltage and output the second power frequency voltage to the filter unit.

[0021] The filtering unit is used to filter and output the second power frequency voltage.

[0022] Optionally, the filtering unit includes a third filter capacitor and a filter inductor; the first end of the third filter capacitor and the filter inductor are respectively connected to the first end of the secondary winding in the industrial frequency transformer, the second end of the third filter capacitor is connected to the ground end, and the second end of the filter inductor serves as the output end of the industrial frequency voltage generating unit.

[0023] The capacitance of the third filter capacitor is less than or equal to 12.7 mF. The inductance range of the filter inductor is 1.6 H to 13.8 H.

[0024] Compared with the prior art, the beneficial effects of this application are:

[0025] The voltage waveform generating circuit provided in the present application connects the harmonic voltage generating unit and the industrial frequency voltage generating unit in parallel, so that the mutual interference between the second harmonic voltage of the harmonic voltage generating unit and the second industrial frequency voltage output by the industrial frequency voltage generating unit is greatly reduced, thereby ensuring that the voltage output by the voltage waveform generating circuit (i.e., the second industrial frequency voltage superimposed on the second harmonic voltage) does not meet the scenario requirements, that is, the voltage waveform generating circuit provided in the present application has low reliability.

[0026] The voltage waveform generating circuit provided in the present application can realize the superposition of the second industrial frequency voltage and the second harmonic voltage of multiple frequencies, which not only avoids the tedious process of multiple replacement or adjustment of settings when using a single harmonic generator, thereby improving the working efficiency of the voltage waveform generating circuit, but also helps to more comprehensively evaluate the performance of power equipment.

[0027] The third filter capacitor and the filter inductor are provided in the present application, which can further reduce the mutual interference between the second power frequency voltage and the second harmonic voltage, protect the safe operation of the second signal generator and the power amplifier, and avoid damage to the second signal generator and the power amplifier as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 A schematic structural diagram of a voltage waveform generating circuit in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the distortion rate of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed and the distortion rate of the first harmonic voltage output by the first signal generator in an embodiment of the present application as the capacitance of the first filter capacitor changes;

[0031] Figure 3 A schematic diagram of the second harmonic voltage when the capacitance of the first filter capacitor is reasonable and the capacitance is too large in the embodiment of the present application;

[0032] Figure 4 It is a schematic diagram of the distortion rate of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed and the distortion rate of the first harmonic voltage output by the first signal generator as the inductance value of the filter inductor changes in the embodiment of the present application;

[0033] Figure 5 A schematic diagram of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed when the filter inductance has a reasonable inductance value and an inductance value that is too small in the embodiment of the present application;

[0034] Figure 6 It is a schematic diagram of the distortion rate of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed and the distortion rate of the first harmonic voltage output by the first signal generator as the capacitance of the third filter capacitor changes in the embodiment of the present application;

[0035] Figure 7 A schematic diagram of the second power frequency voltage when the third filter capacitor has a reasonable capacitance and a capacitance that is too small in the embodiment of the present application;

[0036] Figure 8 It is a schematic diagram of the second power frequency voltage, the second harmonic voltage and the superimposed voltage in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0038] The terms "first", "second", etc. in the specification embodiments, claims, and drawings of the present application are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, including a series of steps or units. The method, system, product, or device is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0039] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0040] The present application provides a voltage waveform generating circuit, such as Figure 1 As shown, the voltage waveform generating circuit 10 comprises a harmonic voltage generating unit 1 and a power frequency voltage generating unit 2. The harmonic voltage generating unit 1 and the power frequency voltage generating unit 2 are connected in parallel.

[0041] Optionally, the harmonic voltage generating unit 1 is used to: generate a first harmonic voltage, transform the voltage level of the first harmonic voltage, and output a second harmonic voltage. The second harmonic voltage is used to indicate the first harmonic voltage after the voltage level transformation.

[0042] The power frequency voltage generating unit 2 is used to generate a first power frequency voltage, transform the voltage level of the first power frequency voltage and output a second power frequency voltage. The second power frequency voltage is used to indicate the first power frequency voltage after the voltage level transformation.

[0043] In some possible implementations, such as Figure 1 , the harmonic voltage generating unit 1 includes a first signal generator 11, a power amplifier 12 and a high frequency transformer T1.

[0044] The first end of the first signal generator 11 is connected to the first end of the power amplifier 12, the second end of the power amplifier 12 is used to connect to the first end of the primary winding T11 in the high-frequency transformer T1, and the second end of the primary winding T11 in the high-frequency transformer T1 is connected to the second end of the first signal generator 11; the first end of the secondary winding T12 in the high-frequency transformer T1 serves as the output end of the harmonic voltage generating unit 1, and the second end of the secondary winding T12 in the high-frequency transformer T1 is connected to the ground end.

[0045] Optionally, the first signal generator 11 is used to generate a first harmonic voltage and transmit it to the power amplifier 12 .

[0046] The power amplifier 12 is used to amplify the first harmonic voltage and transmit it to the high-frequency transformer T1.

[0047] The high-frequency transformer T1 is used to transform the voltage level of the amplified first harmonic voltage and output the second harmonic voltage.

[0048] Optionally, the harmonic voltage generating unit 1 further includes a first filter capacitor C1 . A first end of the first filter capacitor C1 is connected to a first end of a secondary winding T12 in the high-frequency transformer T1 , and a second end of the first filter capacitor C1 serves as an output end of the harmonic voltage generating unit 1 .

[0049] The first filter capacitor C1 is used to output the second harmonic voltage and prevent the second power frequency voltage from entering the first signal generator 11 through the high frequency transformer T1.

[0050] The first filter capacitor C1 effectively prevents the second power frequency voltage from entering the high-frequency transformer T1. If the capacitance of the first filter capacitor C1 is too large, more power frequency voltage will enter the high-frequency transformer T1, affecting the normal operation of the high-frequency transformer T1 and the first signal generator 11. If the capacitance of the first filter capacitor C1 is too small, it will affect the content of the second harmonic voltage in the output superimposed voltage. In the embodiment of the present application, the capacitance range of the first filter capacitor C1 is 0.58nF to 0.7nF.

[0051] Exemplarily, the harmonic voltage generating unit 1 further includes a second filter capacitor C2. A first end of the second filter capacitor C2 is connected to the power amplifier 12, and a second end of the second filter capacitor C2 is connected to a first end of the primary winding T11 in the high-frequency transformer T1.

[0052] The second filter capacitor C2 is used to adjust the phase of the first harmonic voltage. Of course, the second filter capacitor C2 can also be used to prevent the second power frequency voltage from entering the first signal generator 11 through the power amplifier 12.

[0053] The capacitance of the second filter capacitor C2 cannot be too low, otherwise the proportion of the second harmonic voltage in the superimposed second power frequency voltage will be too small. At a frequency of 2kHz, the capacitance of the second filter capacitor C2 is less than or equal to 1.13mF.

[0054] In another possible implementation, Figure 1 The power frequency voltage generating unit 2 includes a second signal generator 21 , a power frequency transformer T2 and a filtering unit 22 .

[0055] The first end of the second signal generator 21 is connected to the first end of the primary winding T21 in the industrial frequency transformer T2, the second end of the second signal generator 21 is connected to the second end of the primary winding T21 in the industrial frequency transformer T2, the first end of the secondary winding T22 in the industrial frequency transformer T2 is connected to the first end of the filter unit 22, the second end of the secondary winding T22 in the industrial frequency transformer T2 is connected to the ground end, and the second end of the filter unit 22 serves as the output end of the industrial frequency voltage generating unit 2.

[0056] Optionally, the second signal generator 21 is used to generate a first power frequency voltage and transmit it to the power frequency transformer T2.

[0057] The power frequency transformer T2 is used to transform the voltage level of the first power frequency voltage and output a second power frequency voltage to the filter unit 22 .

[0058] The filtering unit 22 is used to filter and output the second power frequency voltage.

[0059] Optionally, the filtering unit 22 includes a third filtering capacitor C3 and a filtering inductor L. The first ends of the third filtering capacitor C3 and the filtering inductor L are respectively connected to the first end of the secondary winding T22 in the power frequency transformer T2, the second end of the third filtering capacitor C3 is connected to the ground end, and the second end of the filtering inductor L serves as the output end of the power frequency voltage generating unit 2.

[0060] If the capacitance of the third filter capacitor C3 is too large, more second harmonic voltage will be injected into the power frequency transformer T2, affecting the normal operation of the second signal generator 21, and even an over-high voltage may appear at the output end of the power frequency transformer T2. The capacitance of the third filter capacitor C3 is less than or equal to 12.7mF.

[0061] If the inductance of the filter inductor L is too small, the proportion of the second harmonic voltage in the output voltage is small. The inductance range of the filter inductor L is 1.6H to 13.8H.

[0062] As the capacitance of the first filter capacitor C1 changes, the distortion rate THD1 of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed on each other output by the voltage waveform generating circuit 10 and the distortion rate THD2 of the first harmonic voltage output by the first signal generator 11 after being affected by the second power frequency voltage are as follows: Figure 2 The capacitance of the first filter capacitor C1 can be 0.1nF, 0.2nF, 0.3nF, 0.4nF, 0.5nF, 0.6nF, 0.64nF, 0.7nF, 0.8nF and 0.9nF, etc., and we can get Figure 2 .

[0063] from Figure 2 It can be seen that both THD1 and THD2 will change with the change of the capacitance of the first filter capacitor C1. THD1 is greatly affected by the capacitance of the first filter capacitor C1, while THD2 is less affected by the capacitance of the first filter capacitor C1. The second harmonic voltage when the capacitance of the first filter capacitor C1 is too large is as follows: Figure 3 shown. Figure 3 In the figure, U1 represents the second harmonic voltage when the capacitance of the first filter capacitor C1 is reasonable, and U2 represents the second harmonic voltage when the capacitance of the first filter capacitor C1 is too large.

[0064] from Figure 3 It can be seen that if the capacitance of the first filter capacitor C1 is too large, it will have a relatively large impact on the second harmonic voltage. Therefore, it is necessary to select a suitable capacitance for the first filter capacitor C1. In the embodiment of the present application, the capacitance of the first filter capacitor C1 can be 0.64nF.

[0065] Similarly, as the inductance value of the filter inductor L changes, the distortion rate THD1 of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed on each other output by the voltage waveform generating circuit 10 and the distortion rate THD2 of the first harmonic voltage output by the first signal generator 11 after being affected by the second power frequency voltage are as follows: Figure 4 shown.

[0066] from Figure 4 It can be seen that both THD1 and THD2 will increase with the increase of the inductance of the filter inductor L. Compared with THD2, THD1 is more affected by the inductance of the filter inductor L. The filter inductor L can be 0.1H, 0.5H, 0.8H, 1.0H, 1.6H, 2.0H, 3.0H, 5.0H, 10.0H, 13.8H and 15.0H, etc., and we can get Figure 4 .

[0067] The reasonable inductance value of the filter inductor L and the voltage after the second power frequency voltage and the second harmonic voltage are superimposed when the inductance value is too small are as follows: Figure 5 shown. Figure 5 In the figure, U1 represents the voltage obtained by superimposing the second power frequency voltage and the second harmonic voltage when the filter inductance L has a reasonable inductance value, and U2 represents the voltage obtained by superimposing the second power frequency voltage and the second harmonic voltage when the filter inductance L has a too small inductance value.

[0068] from Figure 5 It can be seen that if the inductance of the filter inductor L is too small, the second harmonic voltage will be blocked, and the output voltage is only the second power frequency voltage. Therefore, it is necessary to select a suitable inductance for the filter inductor L. In the embodiment of the present application, the inductance of the filter inductor L can be 10.0H.

[0069] As the capacitance of the third filter capacitor C3 changes, the distortion rate of the voltage after the second power frequency voltage and the second harmonic voltage are superimposed and the distortion rate of the first harmonic voltage output by the first signal generator are as follows: Figure 6 shown.

[0070] The capacitance of the third filter capacitor C3 can be 0.1H, 0.5H, 0.8H, 1.0H, 1.6H, 2.0H, 3.0H, 5.0H, 10.0H, 13.8H and 15.0H, etc., Figure 6 .

[0071] from Figure 6It can be seen that both THD1 and THD2 will change with the change of the capacitance of the third filter capacitor C3. The reasonable capacitance of the third filter capacitor C3 and the second power frequency voltage when the capacitance is too small are as follows: Figure 7 shown. Figure 7 In the figure, U1 represents the second power frequency voltage when the third filter capacitor C3 has a reasonable capacitance, and U1 represents the second power frequency voltage when the third filter capacitor C3 is too small. It is necessary to select a suitable capacitance for the third filter capacitor C3. In the embodiment of the present application, the capacitance of the third filter capacitor C3 can be 12.7 mF.

[0072] Furthermore, according to the respective values ​​of the first filter capacitor C1, the second filter capacitor C2, the third filter capacitor C3 and the filter inductor L, the following can be obtained: Figure 8 The second power frequency voltage U1, the second harmonic voltage U2 and the superimposed voltage U3 are shown. Figure 8 It can be seen that the voltage waveform generating circuit 10 provided in the embodiment of the present application can output a voltage in which the second industrial frequency voltage is superimposed on the second harmonic voltage, which can meet the scenario requirements.

[0073] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A voltage waveform generating circuit, characterized in that: It includes a harmonic voltage generating unit and a power frequency voltage generating unit connected in parallel; The harmonic voltage generating unit is used to: generate a first harmonic voltage, transform the voltage level of the first harmonic voltage, and output a second harmonic voltage; the second harmonic voltage is used to indicate the first harmonic voltage after the voltage level transformation; The power frequency voltage generating unit is used to generate a first power frequency voltage, transform the voltage level of the first power frequency voltage and output a second power frequency voltage; the second power frequency voltage is used to indicate the first power frequency voltage after the voltage level transformation.

2. The voltage waveform generating circuit according to claim 1, characterized in that: The harmonic voltage generating unit includes a first signal generator, a power amplifier and a high-frequency transformer; The first end of the first signal generator is connected to the first end of the power amplifier, the second end of the power amplifier is used to connect to the first end of the primary winding in the high-frequency transformer, and the second end of the primary winding in the high-frequency transformer is connected to the second end of the first signal generator; the first end of the secondary winding in the high-frequency transformer serves as the output end of the harmonic voltage generating unit, and the second end of the secondary winding in the high-frequency transformer is connected to the ground end.

3. The voltage waveform generating circuit according to claim 2, characterized in that: The first signal generator is used to: generate the first harmonic voltage and transmit it to the power amplifier; The power amplifier is used to: amplify the first harmonic voltage and transmit it to the high-frequency transformer; The high-frequency transformer is used to transform the voltage level of the amplified first harmonic voltage and output the second harmonic voltage.

4. The voltage waveform generating circuit according to claim 2 or 3, characterized in that: The harmonic voltage generating unit further includes a first filter capacitor; a first end of the first filter capacitor is connected to a first end of a secondary winding in the high-frequency transformer, and a second end of the first filter capacitor serves as an output end of the harmonic voltage generating unit; The first filter capacitor is used to output the second harmonic voltage and prevent the second power frequency voltage from entering the first signal generator through the high-frequency transformer.

5. The voltage waveform generating circuit according to claim 4, characterized in that: The harmonic voltage generating unit further includes a second filter capacitor; a first end of the second filter capacitor is connected to the power amplifier, and a second end of the second filter capacitor is connected to a first end of a primary winding in the high-frequency transformer; The second filter capacitor is used to adjust the phase of the first harmonic voltage.

6. The voltage waveform generating circuit according to claim 5, characterized in that: The capacitance range of the first filter capacitor is 0.58nF to 0.7nF; The capacitance of the second filter capacitor is less than or equal to 1.13 mF.

7. The voltage waveform generating circuit according to claim 1, characterized in that: The power frequency voltage generating unit includes a second signal generator, a power frequency transformer and a filtering unit; The first end of the second signal generator is connected to the first end of the primary winding in the power frequency transformer, the second end of the second signal generator is connected to the second end of the primary winding in the power frequency transformer, the first end of the secondary winding in the power frequency transformer is connected to the first end of the filter unit, the second end of the secondary winding in the power frequency transformer is connected to the ground end, and the second end of the filter unit serves as the output end of the power frequency voltage generating unit.

8. The voltage waveform generating circuit according to claim 7, characterized in that: The second signal generator is used to: generate the first power frequency voltage and transmit it to the power frequency transformer; The power frequency transformer is used to: transform the voltage level of the first power frequency voltage and output the second power frequency voltage to the filtering unit; The filtering unit is used to filter and output the second power frequency voltage.

9. The voltage waveform generating circuit according to claim 7 or 8, characterized in that: The filtering unit includes a third filter capacitor and a filter inductor; the first ends of the third filter capacitor and the filter inductor are respectively connected to the first end of the secondary winding in the industrial frequency transformer, the second end of the third filter capacitor is connected to the ground end, and the second end of the filter inductor serves as the output end of the industrial frequency voltage generating unit.

10. The voltage waveform generating circuit according to claim 9, characterized in that: The third filter capacitor is used to: prevent the second power frequency voltage from being transmitted to the ground terminal, and transmit the second harmonic voltage from the filter inductor to the ground terminal; The filter inductor is used to output the second power frequency voltage and prevent the second harmonic voltage from entering the second signal generator through the power frequency transformer.

11. The voltage waveform generating circuit according to claim 9, characterized in that: The capacitance of the third filter capacitor is less than or equal to 12.7 mF; The inductance value of the filter inductor ranges from 1.6H to 13.8H.

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