Voltage transformer DC bias test device for photovoltaic power generation and control method thereof

Abstract

The invention discloses a voltage transformer direct current bias test device for photovoltaic power generation and a control method thereof in the field of electrical measurement. The device and the control method thereof comprise a first voltage regulator, an alternating current booster, a direct current voltage source and a voltage divider for monitoring. The components form a direct current bias voltage source which is connected with a primary coil of a voltage transformer for photovoltaic power generation in parallel and applies direct current bias power frequency test voltage, a second alternating current voltage source is connected with a standard voltage transformer in parallel and applies processing frequency alternating current test voltage, and a voltage divider for monitoring monitors voltage output by the direct current bias voltage source. Secondary coil output voltages of a tested mutual inductor and a standard mutual inductor, a voltage of a primary current flowing through a sampling resistor and an output voltage of a voltage divider are measured and input to a voltage transformer direct current bias performance measurement unit; and obtaining an error of the tested voltage transformer for photovoltaic power generation under a direct current bias condition, a primary current waveform, and a power frequency alternating current component and a direct current bias component of output voltage of a direct current bias voltage source.

Description

Technical Field

[0001] The invention relates to a direct current bias test device of a voltage transformer for photovoltaic power generation and a control method thereof, belonging to the technical field of electrical measurement. Background Art

[0002] The photovoltaic grid-connected power generation system is mainly composed of a photovoltaic cell array, a photovoltaic inverter, an AC filter, a photovoltaic transformer and a power grid. In this system, the photovoltaic inverter is responsible for converting the DC power generated by the photovoltaic cell array into AC power, and connecting it to the power grid through the photovoltaic transformer to generate electricity. In order to monitor the voltage at the input port of the photovoltaic transformer, that is, the output voltage of the photovoltaic inverter, a voltage transformer is usually used. The voltage level of the photovoltaic inverter is generally between 220V and 800V, and the traditional resistor divider and the voltage sensor based on the Hall sensor are limited in their application due to the problems of low output signal power, low accuracy, and temperature drift. In contrast, the voltage transformer is widely used due to its advantages such as stable performance, high accuracy and large output signal power, especially in the line voltage measurement of the three-phase line. One end of its secondary output is grounded, which increases the safety of people and instruments.

[0003] However, the output voltage of the photovoltaic inverter may have a DC component due to the asymmetry of the on and off time of the power switch tube, the imbalance of the pulse width during the PWM modulation process, the mismatch of the drive signal, and the grid-connected detection error. This phenomenon is called DC bias. Since the voltage transformer can only convert AC voltage signals, the DC bias voltage will act on the primary coil of the voltage transformer, which may cause DC bias excitation, affect the performance of the transformer, and in extreme cases cause the core to saturate, heat up, or even burn out. At present, the design and accuracy verification of the voltage transformer are carried out under sinusoidal working conditions, which is different from the actual voltage output of the photovoltaic inverter. As a result, the traditional voltage transformer test device cannot effectively verify the accuracy and saturation state of the voltage transformer under DC bias conditions. Summary of the invention

[0004] The purpose of the present invention is to provide a DC bias test device for a voltage transformer for photovoltaic power generation and a control method thereof. The device can provide a DC bias test voltage that simultaneously includes an adjustable DC voltage and an adjustable industrial frequency AC voltage, thereby realizing an error calibration test of a voltage transformer for photovoltaic power generation under a DC bias condition, and can detect the primary current of the voltage transformer for photovoltaic power generation under a DC bias condition, thereby detecting the saturation state of the voltage transformer for photovoltaic power generation.

[0005] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions.

[0006] In a first aspect, the present invention provides a photovoltaic power generation voltage transformer DC bias test device, characterized in that it comprises: a first voltage regulator , AC booster , a DC voltage source and a monitoring voltage divider, wherein the first voltage regulator and AC booster The two secondary coils constitute a first AC voltage source and a second AC voltage source respectively. The first AC voltage source, the DC voltage source and the sampling resistor The DC bias voltage source is connected in series to form a DC bias voltage source, and the output of the DC bias voltage source is connected to the voltage transformer for the photovoltaic power generation under test. The primary coil of the tested photovoltaic power generation voltage transformer is connected in parallel. Applying a DC bias voltage, the output of the second AC voltage source is connected to a standard voltage transformer parallel, and the standard voltage transformer The primary coil of the photovoltaic power generation device is applied with a power frequency AC test voltage, and the monitoring voltage divider is used to monitor the power frequency AC test voltage and the DC bias voltage output by the DC bias voltage source; the tested photovoltaic power generation voltage transformer Secondary coil, standard voltage transformer The output ports of the secondary coil are connected to the first load and the second load respectively, and the photovoltaic power generation voltage transformer under test The output end of the secondary coil, standard voltage transformer The output end of the secondary coil and the output end of the monitoring voltage divider are connected to the voltage transformer DC bias performance measurement unit The input terminal connection of

[0007] In combination with the first aspect, further comprising a second voltage regulator , Isolation transformer , rectifier bridge UR, polarized capacitor , non-polar capacitor , discharge resistor , the first resistor and the second resistor ; The second voltage regulator , Isolation transformer , rectifier bridge UR, polarized capacitor , non-polar capacitor , discharge resistor constituting the DC voltage source; The first resistor and the second resistor The monitoring voltage divider is formed.

[0008] In combination with the first aspect, further, the AC booster The non-same-name ends of the primary coil and the two secondary coils are grounded, and the isolation transformer The non-same-name ends of the primary coil of the standard voltage regulator are grounded, the non-same-name ends of the primary coil and the secondary coil of the standard voltage regulator are grounded, and one end of the monitoring voltage divider is grounded.

[0009] In combination with the first aspect, further, the second voltage regulator Controlling the output voltage of the DC voltage source , the first voltage regulator Controlling the output voltage of the first AC voltage source , the output voltage of the DC voltage source The output voltage of the first AC voltage source The sum of constitutes the DC bias voltage.

[0010] In combination with the first aspect, further, the AC booster The DC bias current generated by the DC bias voltage source flows through the voltage transformer for photovoltaic power generation under test. The primary coil and sampling resistor And the AC booster A secondary coil constitutes a circuit, making the AC booster The iron core is in a DC bias state, and the magnetic flux density of the iron core is controlled within a preset range.

[0011] In combination with the first aspect, further, the AC booster There are two identical secondary coils, and the resistance range of the two secondary coils is between 0.01 and 1 ohm.

[0012] In combination with the first aspect, further, the sampling resistor The range is between 0.05 and 1 ohm.

[0013] In a second aspect, a control method for a voltage transformer DC bias test device for base voltage power generation is provided, characterized in that it comprises: Using the first regulator The first AC voltage source is adjusted to generate the required power frequency AC test voltage; the second voltage regulator is used Adjusting the DC voltage source to generate a desired DC bias voltage; Apply the DC bias voltage and the industrial frequency AC test voltage to the tested photovoltaic power generation voltage transformer. The DC bias power frequency test voltage is converted into a voltage on the secondary coil. ; Apply the power frequency AC test voltage to the standard voltage transformer The primary coil is converted into a voltage on the secondary coil ; The primary current of the voltage transformer for photovoltaic power generation under test flows through the sampling resistor The voltage generated when And monitor the voltage output of the voltage divider ; The photovoltaic power generation voltage transformer under test The output voltage of the secondary coil , Standard voltage transformer The output voltage of the secondary coil 、Tested photovoltaic power generation voltage transformer The primary current flows through the sampling resistor The voltage generated when And monitor the voltage output of the voltage divider Perform signal conditioning and analog-to-digital conversion in sequence to obtain a conditioned and converted voltage signal; The conditioned and converted voltage signal is input into the voltage transformer DC bias performance measurement unit The voltage transformer for photovoltaic power generation under test is obtained Error under DC bias conditions, tested photovoltaic power generation voltage transformer The primary current waveform, the industrial frequency AC component of the DC bias voltage source output voltage, and the DC bias voltage component.

[0014] In combination with the second aspect, further, obtaining the error of the tested photovoltaic power generation voltage transformer under a DC bias condition includes: According to the conversion amount of the industrial frequency AC component output by the secondary coil of the tested photovoltaic power generation voltage transformer (6) With standard voltage transformer The secondary coil output voltage The difference between the voltage transformer and the tested photovoltaic power generation voltage transformer is obtained. and standard voltage The AC output voltage difference ; The voltage transformer DC bias performance measurement unit The error under the DC bias condition is calculated in With standard voltage transformer The secondary coil output voltage The ratio of the tested photovoltaic power generation voltage transformer is obtained. Error under DC bias conditions; The tested photovoltaic power generation voltage transformer The error under DC bias conditions is expressed as: ; ; in, It indicates the AC output voltage difference between the tested photovoltaic power generation voltage transformer and the standard voltage transformer under DC bias conditions; Indicates the conversion amount of the power frequency AC component output by the secondary coil of the tested photovoltaic power generation voltage transformer; Indicates the secondary coil output voltage of a standard voltage transformer; It represents the complex error of the tested photovoltaic power generation voltage transformer under DC bias conditions.

[0015] In combination with the second aspect, further, the primary current waveform of the tested photovoltaic power generation voltage transformer includes: By calculating the sampling resistance Output voltage , the voltage transformer for photovoltaic power generation under the DC bias test voltage condition is obtained The primary current waveform; If the primary current waveform is distorted, the voltage transformer for photovoltaic power generation under test Enter the saturation state; if the primary current waveform is not distorted, the voltage transformer for photovoltaic power generation under test In unsaturated state.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The DC bias test device for a voltage transformer for photovoltaic power generation of the present invention can provide a DC bias test voltage that includes both an adjustable DC voltage and an adjustable industrial frequency AC voltage, and realizes error verification of the voltage transformer for photovoltaic power generation under DC bias conditions by measuring and calculating the output voltage of the tested photovoltaic power generation voltage transformer and the output voltage of the standard voltage transformer, thereby solving the limitation problem that the traditional voltage transformer error test device can only perform error verification under pure sine wave conditions, and meeting the verification requirements of simulating actual field operation conditions. At the same time, the saturation state of the tested photovoltaic power generation voltage transformer is monitored by monitoring the primary current waveform. The DC bias test device for a voltage transformer for photovoltaic power generation of the present invention provides a guarantee for the development and safe use of photovoltaic power generation voltage transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. 1 is a schematic diagram of a DC bias test device for a voltage transformer for photovoltaic power generation provided by an embodiment of the present invention; In the figure: 1. first voltage regulator; 2. AC booster; 3. DC voltage source; 4. voltage divider for monitoring; 5. sampling resistor; 6. voltage transformer for tested photovoltaic power generation; 7. standard voltage transformer; 8. second voltage regulator; 9. voltage transformer DC bias performance measurement unit; 10. isolation transformer; 11. rectifier bridge; 12. polarized capacitor; 13. non-polarized capacitor; 14. discharge resistor; 15. first resistor; 16. second resistor; 17. first load; 18. second load. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0019] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship. Example 1

[0020] This embodiment introduces a DC bias test device for a voltage transformer for photovoltaic power generation. The device can generate a special test voltage, which includes an adjustable DC voltage and an adjustable industrial frequency AC voltage. This combined voltage simulates the actual voltage output by a photovoltaic inverter.

[0021] See also Figure 1 The test device includes a first voltage regulator 1, an AC booster 2, a sampling resistor 5, a voltage transformer for tested photovoltaic power generation 6, a standard voltage transformer 7, a second voltage regulator 8, a voltage transformer DC bias performance measurement unit 9, an isolation transformer 10, a rectifier bridge 11, a polarized capacitor 12, a non-polarized capacitor 13, a discharge resistor 14, a first resistor 15 and a second resistor 16.

[0022] The two secondary coils of the first voltage regulator 1 and the AC booster 2 respectively constitute a linked first AC voltage source and a second AC voltage source for providing an adjustable AC voltage; the second voltage regulator 8, the isolation transformer 10, the rectifier bridge 11, the polarized capacitor 12, the non-polarized capacitor 13, and the discharge resistor 14 constitute a DC voltage source 3 for providing an adjustable DC voltage source; the first AC voltage source, the DC voltage source 3 and the sampling resistor 5 are connected in series to form a DC bias voltage source; the first resistor 15 and the second resistor 16 constitute a monitoring voltage divider 4 for monitoring the industrial frequency AC voltage component and the DC bias voltage component of the output voltage of the DC bias voltage source.

[0023] The non-same-named ends of the primary coil and the secondary coil of the AC booster 2 are grounded, the non-same-named ends of the primary coil of the isolation transformer 10 are grounded, the non-same-named ends of the primary coil and the secondary coil of the standard voltage device 7 are grounded, and one end of the monitoring voltage divider 4 is grounded, thereby protecting personal safety and equipment safety.

[0024] In an embodiment of the present invention, the AC booster 2 is an anti-DC AC booster and has two identical secondary coils, and the resistance range of the two secondary coils is less than 1 ohm. At the same time, the range of the sampling resistor 5 is set between 0.05 and 1 ohm to reduce the influence of the resistance voltage drop in the power supply line on the measurement result. By using a low-resistance coil and a sampling resistor 5, this influence can be minimized to ensure the accuracy of the measurement.

[0025] It should be noted that under the condition of the maximum bias DC current of the device, the booster operates in the non-saturated zone and is powered by two identical secondary coils respectively, which avoids the primary coil of the tested photovoltaic power generation voltage transformer and the primary coil of the standard voltage transformer being in the same loop, so that the standard voltage transformer is not affected by the DC bias. Therefore, the traditional standard voltage transformer can be used for error verification, ensuring the accuracy of the value transfer.

[0026] Furthermore, the DC bias current generated by the DC bias voltage source flows through a circuit composed of the primary coil of the tested photovoltaic power generation voltage transformer 6, the sampling resistor 5 and a secondary coil of the AC booster 2, so that the iron core in the AC booster 2 is in a DC bias state, and the design of the AC booster 2 controls the magnetic flux density of the iron core within a preset range to prevent the iron core from entering a saturation state, thereby ensuring the linear response and accuracy of the AC booster 2, that is, under the condition of the maximum biasable DC current of the device, the AC booster 2 operates in a non-saturated region.

[0027] Furthermore, the output of the DC bias voltage source is connected in parallel with the primary coil of the tested photovoltaic power generation voltage transformer 6, and a DC bias power frequency test voltage is applied to the tested photovoltaic power generation voltage transformer 6. The output of the second AC voltage source is connected in parallel with the standard voltage transformer 7, and a power frequency AC test voltage is applied to the primary coil of the standard voltage transformer 7. The secondary coil of the tested photovoltaic power generation voltage transformer 6 and the secondary coil of the standard voltage transformer 7 are respectively connected to the first load 17 and the second load 18 to simulate the actual load conditions and obtain the voltage output. The obtained secondary coil voltage output is marked as and . Example 2

[0028] A control method for a DC bias test device of a voltage transformer for base-voltage power generation, comprising: Using the first voltage regulator 1 to adjust the first AC voltage source to generate the required power frequency AC test voltage; using the second voltage regulator 8 to adjust the DC voltage source to generate the required DC bias voltage; Apply the DC bias voltage and the power frequency AC test voltage to the primary coil of the tested photovoltaic power generation voltage transformer 6 to obtain the DC bias power frequency test voltage, and convert the DC bias power frequency test voltage into a voltage on the secondary coil. ; The power frequency AC test voltage is applied to the primary coil of the standard voltage transformer 7 and converted into a voltage on the secondary coil ; Collect the voltage generated when the primary current of the tested photovoltaic power generation voltage transformer 6 flows through the sampling resistor 5 And monitor the voltage output by voltage divider 4 ; The output voltage of the secondary coil of the tested photovoltaic power generation voltage transformer 6 , Output voltage of the secondary coil of standard voltage transformer 7 , the voltage generated when the primary current of the tested photovoltaic power generation voltage transformer 6 flows through the sampling resistor 5 And monitor the voltage output by voltage divider 4 Perform signal conditioning and analog-to-digital conversion in sequence to obtain a conditioned and converted voltage signal; The conditioned and converted voltage signal is input into the voltage transformer DC bias performance measurement unit 9 to obtain the error of the tested photovoltaic power generation voltage transformer 6 under DC bias conditions, the primary current waveform of the tested photovoltaic power generation voltage transformer 6, the industrial frequency AC component of the output voltage of the DC bias voltage source, and the DC bias voltage component.

[0029] Specifically, the performance of the photovoltaic power generation voltage transformer 6 under DC bias conditions is evaluated and analyzed, including the following situations: a. The conversion amount of the industrial frequency AC voltage component output by the secondary coil of the tested photovoltaic power generation voltage transformer 6 , the secondary coil output voltage of the standard voltage transformer 7 Input into the pre-built voltage transformer DC bias performance measurement unit 9 to obtain the error of the tested photovoltaic power generation voltage transformer 6 under DC bias conditions; like Figure 1 As shown, the voltage at terminal A is the output voltage of the first secondary coil of AC booster 2. , that is, the output voltage of the first AC voltage source, the output voltage The size of is adjusted by the first voltage regulator 1, and the voltage difference between the A terminal and the B terminal is the output voltage of the DC voltage source , the output voltage The size of is adjusted by the second voltage regulator 8, and the voltage at the B terminal is , that is, the output voltage of the DC voltage source 3 The output voltage of the first AC voltage source The sum of constitutes a DC bias power frequency test voltage, and its DC voltage component and AC voltage component can be adjusted independently. This independent adjustment capability allows the test device to simulate voltage conditions under different conditions to test the performance of the photovoltaic power generation voltage transformer 6 under various DC bias conditions.

[0030] The voltage at the C terminal is the output voltage of the second secondary coil of AC booster 2 , that is, the output voltage of the second AC voltage source, which is directly applied to both ends of the primary coil of the standard voltage transformer 7. Since the two secondary coils of the AC booster 2 are exactly the same, the induced voltages of the two secondary coils on the iron core are the same, and there are the same internal impedances, but the currents flowing through the two secondary coils are different. ,in, Represents the internal impedance voltage drop difference of the two secondary coils. When the resistance of the two secondary coils is very small, the primary current of the standard voltage transformer 7 is also very small. To speak Very small, at this time , and since the output voltage There is no DC bias, and the DC characteristics of the standard voltage transformer 7 are not considered, so a traditional standard voltage transformer can be used.

[0031] In a further embodiment of the present invention, since the voltage transformer can only convert AC signals, the secondary output of the tested photovoltaic power generation voltage transformer 6 is a DC bias power frequency test voltage. AC component in (voltage at terminal B) Conversion volume , according to the conversion amount The secondary coil output voltage of the standard voltage transformer 7 The difference between the AC output voltage of the tested photovoltaic power generation voltage transformer 6 and the standard voltage transformer 7 is obtained. , that is, the error under DC bias conditions ; Calculate the error under DC bias conditions in the voltage transformer DC bias performance measurement unit 9 Ratio to the secondary coil output voltage of standard voltage transformer 7 , the error of the tested photovoltaic power generation voltage transformer 6 under DC bias conditions is obtained , so we get the ratio difference and the angle difference.

[0032] The error expression of the tested photovoltaic power generation voltage transformer 6 under DC bias conditions is: ; ; in, It indicates the AC output voltage difference between the tested photovoltaic power generation voltage transformer and the standard voltage transformer under DC bias conditions; Indicates the conversion amount of the power frequency AC component output by the secondary coil of the tested photovoltaic power generation voltage transformer; Indicates the secondary coil output voltage of a standard voltage transformer; It represents the complex error of the tested photovoltaic power generation voltage transformer under DC bias conditions.

[0033] b. The voltage generated when the primary current of the tested photovoltaic power generation voltage transformer 6 flows through the sampling resistor 5 The voltage is input into the pre-built voltage transformer DC bias performance measurement unit 9 to obtain the primary current waveform of the tested photovoltaic power generation voltage transformer 6.

[0034] Specifically, by calculating the output voltage of the sampling resistor 5, the primary current waveform of the tested photovoltaic power generation voltage transformer 6 under the DC bias test voltage condition is obtained; If the primary current waveform is distorted, the tested photovoltaic power generation voltage transformer 6 enters a saturated state; if the primary current waveform is not distorted, the tested photovoltaic power generation voltage transformer 6 enters a non-saturated state.

[0035] c. Monitor the voltage output by voltage divider 4 The voltage is input into the pre-built voltage transformer DC bias performance measurement unit 9 to obtain the industrial frequency AC component and the DC bias component of the output voltage of the DC bias voltage source.

[0036] The photovoltaic power generation voltage transformer DC bias test device of the present invention can be used for 0.5 and 0.2 level voltage transformers with a primary rated voltage range of 220V to 800V. The test device comprises two AC voltage sources, namely a first AC voltage source and a second AC voltage source, and the maximum output voltage is 1200VAC / 50Hz, and the maximum output capacity is 2kVA. The maximum output DC bias voltage of the DC voltage source 3 is 40VDC, and the maximum output DC bias current is 0.5A. The accuracy of the standard voltage transformer 7 is 0.05 level, the maximum primary rated voltage is 800V, the maximum secondary rated voltage is 100V, the accuracy of the monitoring voltage divider is 0.5 level, the maximum detection voltage is 1200VAC / 50Hz+40VDC, the maximum resistance of the sampling resistor 5 is 1 ohm, the temperature drift is no more than 10ppm / °C, and the maximum effective current that can flow is 1A. Example 3

[0037] The DC bias test device for the voltage transformer for photovoltaic power generation of the present invention is used to verify the rated primary voltage of level 0.2 , Rated secondary voltage , 50Hz, rated load 5VA photovoltaic power generation voltage transformer, the maximum output voltage of the first AC voltage source and the second AC voltage source of the device are 300VAC / 50Hz, which can meet the power frequency voltage output verification voltage requirement of up to 1.2 times the rated primary voltage, the output of the DC voltage source 3 can bias the DC current up to 0.5A, the maximum output voltage is 25VDC, which can meet the DC voltage bias of 10% relative to the rated primary voltage, the standard voltage transformer 7 has an accuracy of 0.05, and the rated primary voltage , Rated secondary voltage , 50Hz, rated load 5VA, the accuracy of the monitoring voltage divider 4 is 0.5 level, the voltage divider ratio is 500:1, the first resistor 15 is 1M ohm, the maximum monitoring voltage is 500V, the sampling resistor 5 has a resistance of 1 ohm, the temperature drift is 10ppm / °C, the resistance power is 1W, the input voltage of the AC booster 2 is 0~220VAC, the output voltage is 0~350V, and the capacity is 2kVA, the input voltage of the isolation transformer 10 is 0~100VAC, the output voltage is 0~100V, and the capacity is 1kVA, the rectifier bridge 11 adopts KPBC2510 bridge rectifier bridge stack, and the polarized capacitor 12 adopts two parallel 1000 / 500V Electrolytic capacitor, non-polar capacitor 13 is The discharge resistor 14 is 1k ohm. The voltage transformer DC bias performance measurement unit 9 is composed of a traditional transformer tester, an oscilloscope and a digital multimeter. The tested voltage transformer signal input port and the standard voltage transformer signal input port of the traditional transformer tester are respectively connected to the secondary output of the tested photovoltaic power generation voltage transformer 6 and the secondary output of the standard voltage transformer 7. The voltage output on the sampling resistor 5 and monitor the 4 outputs using a voltage divider An oscilloscope and a digital multimeter were used for monitoring.

[0038] The above-mentioned voltage transformer DC bias test device for photovoltaic power generation can achieve the goal of simple circuit and economical implementation. It only needs to be modified on the basis of the traditional voltage transformer error test device to realize error verification and performance monitoring under DC bias conditions.

[0039] Specifically, a DC voltage source 3 composed of common components such as a voltage regulator, an isolation transformer 10, a rectifier bridge 11, and a capacitor is added, and a conventional booster is replaced with an easily implementable DC-resistant booster composed of an iron core and a coil, so that a DC bias voltage source can be formed, and a standard voltage transformer 7 and a voltage regulator of a conventional voltage transformer error test device can be used, and the voltage regulator is the first voltage regulator 1; if the voltage transformer DC bias performance measurement unit 9 is to be designed as a whole, the voltage transformer error test and calculation part is the same as that of the conventional transformer tester, and the voltage output on the sampling resistor 5 is and monitor the 4 outputs using a voltage divider , the time series sampling data can be subjected to Fourier transform to obtain the DC component, power frequency component and harmonic component, thereby obtaining the DC current component, power frequency current component, harmonic current component and current distortion rate flowing through the primary coil of the tested photovoltaic power generation voltage transformer 6, and at the same time obtaining the DC voltage component and power frequency voltage component of the DC bias voltage; if the specially designed voltage transformer DC bias performance measurement unit 9 is not considered, a traditional transformer tester can be used, and the line connection method of the transformer tester and the secondary output of the tested photovoltaic power generation voltage transformer 6 and the secondary output of the standard voltage transformer 7 is consistent with the traditional connection method, and the usage is also the same. At this time, the voltage output on the sampling resistor 5 is and monitor the 4 outputs using a voltage divider An oscilloscope and a digital multimeter can be used for monitoring.

[0040] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A DC bias test device for a voltage transformer for photovoltaic power generation, characterized in that: include: A first voltage regulator (1), an AC booster (2), a DC voltage source (3), and a monitoring voltage divider (4); the two secondary coils of the first voltage regulator (1) and the AC booster (2) respectively constitute a first AC voltage source and a second AC voltage source; the first AC voltage source, the DC voltage source (3), and a sampling resistor (5) are connected in series to constitute a DC bias voltage source; the output of the DC bias voltage source is connected in parallel to the primary coil of a tested photovoltaic power generation voltage transformer (6), and a DC bias voltage is applied to the tested photovoltaic power generation voltage transformer (6); the output of the second AC voltage source is connected in parallel to a standard voltage transformer (7), and the standard A power frequency AC test voltage is applied to the primary coil of the voltage transformer (7), and the monitoring voltage divider (4) is used to monitor the power frequency AC test voltage and the DC bias voltage output by the DC bias voltage source; the output ends of the secondary coil of the tested photovoltaic power generation voltage transformer (6) and the secondary coil of the standard voltage transformer (7) are respectively connected to a first load (17) and a second load (18), and the output end of the secondary coil of the tested photovoltaic power generation voltage transformer (6), the output end of the secondary coil of the standard voltage transformer (7) and the output end of the monitoring voltage divider (4) are connected to the input end of the voltage transformer DC bias performance measurement unit (9).

2. The photovoltaic power generation voltage transformer DC bias test device according to claim 1, characterized in that: It also includes a second voltage regulator (8), an isolation transformer (10), a rectifier bridge (11), a polarized capacitor (12), a non-polarized capacitor (13), a discharge resistor (14), a first resistor (15) and a second resistor (16); The second voltage regulator (8), the isolation transformer (10), the rectifier bridge (11), the polarized capacitor (12), the non-polarized capacitor (13), and the discharge resistor (14) constitute the DC voltage source (3); The first resistor (15) and the second resistor (16) constitute the monitoring voltage divider (4).

3. The photovoltaic power generation voltage transformer DC bias test device according to claim 2, characterized in that: The non-same-named ends of the primary coil and two secondary coils of the AC booster (2) are grounded, the non-same-named ends of the primary coil of the isolation transformer (10) are grounded, the non-same-named ends of the primary coil and secondary coil of the standard voltage device (7) are grounded, and one end of the monitoring voltage divider (4) is grounded.

4. The photovoltaic power generation voltage transformer DC bias test device according to claim 2, characterized in that: The second voltage regulator (8) controls the output voltage of the DC voltage source (3) The first voltage regulator (7) controls the output voltage of the first AC voltage source , the output voltage of the DC voltage source (3) The output voltage of the first AC voltage source The sum of constitutes the DC bias voltage.

5. The photovoltaic power generation voltage transformer DC bias test device according to claim 1, characterized in that: The AC booster (2) is a DC-resistance AC booster, and the DC bias current generated by the DC bias voltage source flows through a circuit consisting of a primary coil of a tested photovoltaic power generation voltage transformer (6), a sampling resistor (5), and a secondary coil of the AC booster (2), so that the iron core in the AC booster (2) is in a DC bias state, and the magnetic flux density of the iron core is controlled within a preset range.

6. The photovoltaic power generation voltage transformer DC bias test device according to claim 5, characterized in that: The AC booster (2) has two identical secondary coils, and the resistance of the secondary coils is in the range of 0.01 to 1 ohm.

7. The photovoltaic power generation voltage transformer DC bias test device according to claim 6, characterized in that: The sampling resistor (5) is in the range of 0.05 to 1 ohm.

8. A control method for a photovoltaic power generation voltage transformer DC bias test device according to any one of claims 1 to 7, characterized in that: include: Using the first voltage regulator (1) to adjust the first AC voltage source to generate a required power frequency AC test voltage; Using the second voltage regulator (8) to adjust the DC voltage source to generate a required DC bias voltage; The DC bias voltage and the industrial frequency AC test voltage are applied to the primary coil of the tested photovoltaic power generation voltage transformer (6) to obtain the DC bias industrial frequency test voltage, and the DC bias industrial frequency test voltage is converted into a voltage on the secondary coil. ; The power frequency AC test voltage is applied to the primary coil of the standard voltage transformer (7) and converted into a voltage on the secondary coil. ; Collect the voltage generated when the primary current of the tested photovoltaic power generation voltage transformer (6) flows through the sampling resistor (5) And the voltage output by the monitoring voltage divider (4) ; The output voltage of the secondary coil of the tested photovoltaic power generation voltage transformer (6) is , Standard voltage transformer (7) secondary coil output voltage , the voltage generated when the primary current of the tested photovoltaic power generation voltage transformer (6) flows through the sampling resistor (5) And the voltage output by the monitoring voltage divider (4) Perform signal conditioning and analog-to-digital conversion in sequence to obtain a conditioned and converted voltage signal; The conditioned and converted voltage signal is input into the voltage transformer DC bias performance measurement unit (9) to obtain the error of the tested photovoltaic power generation voltage transformer (6) under DC bias conditions, the primary current waveform of the tested photovoltaic power generation voltage transformer (6), the industrial frequency AC component of the DC bias voltage source output voltage, and the DC bias voltage component.

9. The control method of the photovoltaic power generation voltage transformer DC bias test device according to claim 8, characterized in that: The step of obtaining the error of the tested photovoltaic power generation voltage transformer (6) under a DC bias condition comprises: According to the conversion amount of the industrial frequency AC component output by the secondary coil of the tested photovoltaic power generation voltage transformer (6) The secondary coil output voltage of the standard voltage transformer (7) The difference between the AC output voltage of the tested photovoltaic power generation voltage transformer 6 and the standard voltage transformer 7 is obtained. ; The error under the DC bias condition is calculated in the voltage transformer DC bias performance measurement unit (9). The secondary coil output voltage of the standard voltage transformer (7) The ratio of is obtained to obtain the error of the tested photovoltaic power generation voltage transformer (6) under DC bias conditions; The error expression of the tested photovoltaic power generation voltage transformer (6) under DC bias conditions is: ； ； in, It indicates the AC output voltage difference between the tested photovoltaic power generation voltage transformer and the standard voltage transformer under DC bias conditions; Indicates the conversion amount of the power frequency AC component output by the secondary coil of the tested photovoltaic power generation voltage transformer; Indicates the secondary coil output voltage of a standard voltage transformer; It represents the complex error of the tested photovoltaic power generation voltage transformer under DC bias conditions.

10. The control method of the photovoltaic power generation voltage transformer DC bias test device according to claim 8, characterized in that: The primary current waveform of the tested photovoltaic power generation voltage transformer (6) includes: By calculating the output voltage of the sampling resistor (5) , obtaining the primary current waveform of the tested photovoltaic power generation voltage transformer (6) under the DC bias test voltage condition; If the primary current waveform is distorted, the tested photovoltaic power generation voltage transformer (6) enters a saturated state; if the primary current waveform is not distorted, the tested photovoltaic power generation voltage transformer (6) is in a non-saturated state.

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