A method and terminal for detecting the insulation of DC busbars in an energy storage system

Abstract

This invention discloses a method and terminal for detecting the insulation of a DC bus in an energy storage system. A composite pulse current source containing first and second frequency pulses is injected between the DC bus and ground. The voltage response of the DC bus corresponding to the composite pulse current source is collected. Based on the voltage response, the first and second admittances corresponding to different frequencies are calculated. Based on the first and second admittances, the Y-capacitance and insulation resistance values ​​of the DC bus to ground are obtained. This invention obtains the voltage response of the DC bus by injecting a composite pulse current source containing different first and second frequency pulses, and then performs admittance analysis calculation based on the voltage response to obtain the Y-capacitance and insulation resistance values ​​to ground. This method, using pulse response and admittance analysis calculation, has a short detection time and is not limited by the installation location.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a method and terminal for detecting the insulation of a DC bus in an energy storage system. Background Technology

[0002] As a voltage support bus, the insulation performance of the DC bus directly affects not only the personal safety of users but is also a key factor in safety and property damage issues such as fire hazards. Therefore, the testing of the insulation resistance of the DC bus is particularly important. Currently, there are three main technologies for testing insulation resistance:

[0003] 1. Bridge-type testing, such as balanced and unbalanced bridge testing, mainly utilizes the principle of unbalanced bridge for detection. Its disadvantages include the inability to detect situations where the insulation of the positive and negative terminals of a DC system decreases equally, and for systems with large Y capacitance (greater than 10uF), the detection time will be very long and the error will be large.

[0004] 2. Low-frequency signal injection method: This method generates a square wave signal with positive and negative symmetry and injects it between the DC high-voltage system and the ground. Calculations are performed by sampling the voltage division across the resistor. The disadvantage is that it uses voltage division calculations, making it highly susceptible to voltage interference from the system.

[0005] 3. Low-frequency superposition method: In IT systems, a low-frequency excitation source of a specific frequency is added to the neutral point on the low-voltage side of the isolation transformer, taking advantage of the characteristic that the insulation resistance is much greater than the load resistance. The disadvantage is that it can only be installed and injected in a specific location (near the neutral point of the isolation transformer).

[0006] It is evident that the above-mentioned methods are not comprehensive enough and cannot efficiently and accurately detect the Y capacitor of the DC bus. Furthermore, the installation location of the detection device in some methods is easily affected, resulting in long detection times and large errors. Summary of the Invention

[0007] The technical problem to be solved by this invention is to propose a method and terminal for detecting the insulation of a DC bus in an energy storage system, which can simultaneously detect the capacitance to ground and the insulation resistance value, with a short detection time and no limitation on the installation location.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for detecting the insulation of a DC bus in an energy storage system includes the following steps:

[0010] S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source.

[0011] The expression for the composite pulse current source is as follows:

[0012] I=k1*sin(ω1*t)+k2*sin(ω2*t);

[0013] Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency;

[0014] S2. Based on the voltage response, calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively;

[0015] S3. Based on the first admittance and the second admittance, the Y-capacitance to ground and the insulation resistance value of the DC bus are obtained.

[0016] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows:

[0017] An insulation detection terminal for a DC bus in an energy storage system includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it performs the following steps:

[0018] S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source.

[0019] The expression for the composite pulse current source is as follows:

[0020] I=k1*sin(ω1*t)+k2*sin(ω2*t);

[0021] Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency;

[0022] S2. Based on the voltage response, calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively;

[0023] S3. Based on the first admittance and the second admittance, the Y-capacitance to ground and the insulation resistance value of the DC bus are obtained.

[0024] The beneficial effects of this invention are as follows: It proposes a method and terminal for detecting the insulation of a DC bus in an energy storage system. On the DC bus, a composite pulse current source containing different first and second frequency pulses is injected to obtain the voltage response of the DC bus. Then, admittance analysis is performed on the voltage response to obtain the Y capacitance to ground and the insulation resistance value. The method of pulse response and admittance analysis calculation has a short detection time and is not limited by the installation location. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the steps of a DC bus insulation detection method for an energy storage system according to the present invention;

[0026] Figure 2 This is a basic application topology diagram of an existing DC microgrid;

[0027] Figure 3 This is a schematic diagram of the equivalent insulation to ground of the DC bus in a DC bus insulation testing method for an energy storage system.

[0028] Figure 4 This is a system block diagram of a DC bus insulation detection terminal for an energy storage system according to the present invention.

[0029] Label Explanation:

[0030] 1. An insulation detection terminal for a DC bus in an energy storage system; 2. A memory; 3. A processor. Detailed Implementation

[0031] Please refer to Figures 1 to 3 A method for detecting the insulation of a DC bus in an energy storage system, comprising the following steps:

[0032] S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source.

[0033] The expression for the composite pulse current source is as follows:

[0034] I=k1*sin(ω1*t)+k2*sin(ω2*t);

[0035] Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency;

[0036] S2. Based on the voltage response, calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively;

[0037] S3. Based on the first admittance and the second admittance, the Y-capacitance to ground and the insulation resistance value of the DC bus are obtained.

[0038] As can be seen from the above description, the beneficial effects of the present invention are as follows: by injecting a composite pulse current source containing different first frequency pulses and second frequency pulses, the voltage response corresponding to the DC bus is obtained, and then the admittance analysis is performed on the voltage response to obtain the Y capacitance to ground and the insulation resistance value. The pulse response and admittance analysis calculation method has a short detection time and is not limited by the installation position.

[0039] Further, step S2 specifically includes:

[0040] By combining the admittance transfer function, the first admittance is obtained by performing FFT calculation on the portion of the voltage response corresponding to the first frequency pulse;

[0041] By combining the admittance transfer function, an FFT is performed on the portion of the voltage response corresponding to the second frequency pulse to obtain the second admittance.

[0042] As can be seen from the above description, by establishing the admittance transfer function and using FFT to decompose the response for different frequency bands, the first and second admittances for the corresponding frequency bands can be obtained quickly.

[0043] Furthermore, the procedure before step S1 includes:

[0044] S0. Perform equivalent insulation calculations on the DC bus to ground to obtain the total equivalent Y-capacitance of the DC bus to ground, as expressed below:

[0045]

[0046] Where Yn represents a single Y-capacitor to ground, and N represents an integer;

[0047] The equivalent total insulation resistance value of the DC bus is also obtained, and its expression is as follows:

[0048]

[0049] Wherein, Rn represents the value of a single insulation resistance.

[0050] As can be seen from the above description, treating the DC bus as equivalent to ground insulation simplifies its circuit connection relationship, thus providing a theoretical basis and convenience for subsequent analysis and calculation.

[0051] Further, step S1 includes:

[0052] Based on step S0, the expression for the voltage response is obtained as follows:

[0053]

[0054] Where ω represents the current frequency.

[0055] Further, step S3 includes:

[0056] S31. Calculate the Y-capacitor admittance to ground based on the first admittance and the second admittance, as expressed below:

[0057] G c =Gω1 -G ω2 ;

[0058] Wherein, Gω1 represents the first admittance, and Gω2 represents the second admittance;

[0059] S32. Based on the admittance of the Y-capacitor to ground, the Y-capacitor to ground is obtained, and its expression is:

[0060]

[0061] The insulation resistance value is obtained by the following expression:

[0062] G c1 =ω1*CY,G c2 =ω2*CY;

[0063] Where ω1 represents the first frequency and ω2 represents the second frequency.

[0064] As can be seen from the above description, after equivalent processing, the expressions for voltage with respect to current, insulation resistance value, and Y capacitance to ground are obtained. Based on the composite pulse current source, test analysis is performed to derive the insulation resistance value and Y capacitance to ground.

[0065] Please refer to Figure 4 A DC bus insulation detection terminal 1 for an energy storage system includes a memory 2, a processor 3, and a computer program stored in the memory 2 and executable on the processor 3. When the processor 3 executes the computer program, it performs the following steps:

[0066] S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source.

[0067] The expression for the composite pulse current source is as follows:

[0068] I=k1*sin(ω1*t)+k2*sin(ω2*t);

[0069] Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency;

[0070] S2. Based on the voltage response, calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively;

[0071] S3. Based on the first admittance and the second admittance, obtain the Y capacitance to ground and the insulation resistance value of the DC bus.

[0072] As can be seen from the above description, the beneficial effects of the present invention are as follows: by injecting a composite pulse current source containing different first frequency pulses and second frequency pulses, the voltage response corresponding to the DC bus is obtained, and then the admittance analysis is performed on the voltage response to obtain the Y capacitance to ground and the insulation resistance value. The pulse response and admittance analysis calculation method has a short detection time and is not limited by the installation position.

[0073] Further, step S2 specifically includes:

[0074] By combining the admittance transfer function, the first admittance is obtained by performing FFT calculation on the portion of the voltage response corresponding to the first frequency pulse;

[0075] By combining the admittance transfer function, an FFT is performed on the portion of the voltage response corresponding to the second frequency pulse to obtain the second admittance.

[0076] As can be seen from the above description, by establishing the admittance transfer function and using FFT to decompose the response for different frequency bands, the first and second admittances for the corresponding frequency bands can be obtained quickly.

[0077] Furthermore, the procedure before step S1 includes:

[0078] S0. Perform equivalent insulation calculations on the DC bus to ground to obtain the total equivalent Y-capacitance of the DC bus to ground, as expressed below:

[0079]

[0080] Where Yn represents a single Y-capacitor to ground, and N represents an integer;

[0081] The equivalent total insulation resistance value of the DC bus is also obtained, and its expression is as follows:

[0082]

[0083] Wherein, Rn represents the value of a single insulation resistance.

[0084] As can be seen from the above description, treating the DC bus as equivalent to ground insulation simplifies its circuit connection relationship, thus providing a theoretical basis and convenience for subsequent analysis and calculation.

[0085] Further, step S1 includes:

[0086] Based on step S0, the expression for the voltage response is obtained as follows:

[0087]

[0088] Where ω represents the current frequency.

[0089] Further, step S3 includes:

[0090] S31. Calculate the Y-capacitor admittance to ground based on the first admittance and the second admittance, as expressed below:

[0091] G c =G ω1 -G ω2 ;

[0092] Wherein, Gω1 represents the first admittance, and Gω2 represents the second admittance;

[0093] S32. Based on the admittance of the Y-capacitor to ground, the Y-capacitor to ground is obtained, and its expression is:

[0094]

[0095] The insulation resistance value is obtained by the following expression:

[0096] G c1 =ω1*CY,G c2 =ω2*CY;

[0097] Where ω1 represents the first frequency and ω2 represents the second frequency.

[0098] As can be seen from the above description, after equivalent processing, the expressions for voltage with respect to current, insulation resistance value, and Y capacitance to ground are obtained. Based on the composite pulse current source, test analysis is performed to derive the insulation resistance value and Y capacitance to ground.

[0099] Please refer to Figures 1 to 3 Embodiment 1 of the present invention is as follows:

[0100] A method for testing the insulation of a DC bus in an energy storage system, such as Figure 1 As shown, it includes the following steps:

[0101] S0, Equivalent insulation to ground for DC bus;

[0102] like Figure 2 As shown, the 10kV public power grid is connected to the user's 380V / 690V low-voltage power grid via a transformer. The AC / DC converter is rectified into a DC bus, serving as the supporting bus for the microgrid. The bus is converted from DC / AC to AC power supply to the loads, and then supplied to the DC loads via a DC / DC converter. The AC / DC and DC / DC converters have a capacitance (Yn) and insulation resistance (Rn) to ground, while the bus also has a distributed capacitance (Yl) to ground. Therefore, the equivalent insulation of the DC bus to ground is calculated, and the resulting equivalent diagram is shown below. Figure 3As shown; furthermore, the total Y-capacitance to ground after the DC bus is equivalent is obtained, and its expression is as follows:

[0103]

[0104] The total insulation resistance value after the DC bus is equivalent is expressed as follows:

[0105]

[0106] S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source.

[0107] Referring to the figure, the expression for the composite pulse current source is:

[0108] I=k1*sin(ω1*t)+k2*sin(ω2*t);

[0109] Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency. In practical applications, ω1 = 314 rad / s and ω2 = 1520 rad / s. Furthermore, to improve testing accuracy, 10 pulse current signals and 10 excitation-induced pulse voltage signals are selected for analysis, with 20 sampling points for each pulse.

[0110] Based on this, the expression for the voltage response is as follows:

[0111]

[0112] S2. Based on the voltage response, calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively;

[0113] In this embodiment, the first admittance is obtained by performing FFT calculation on the portion of the voltage response corresponding to the first frequency pulse, in conjunction with the admittance transfer function;

[0114] By combining the admittance transfer function, the second admittance is obtained by performing FFT calculation on the part of the voltage response corresponding to the second frequency pulse.

[0115] The expression for the admittance transfer function is:

[0116]

[0117] The expression for the corresponding first admittance is:

[0118]

[0119] The expression for the corresponding second admittance is:

[0120]

[0121] S3. Based on the first admittance and the second admittance, obtain the Y capacitance and insulation resistance values ​​of the DC bus to ground.

[0122] Step S3 includes:

[0123] S31. Calculate the Y-capacitance admittance to ground based on the first admittance and the second admittance, as expressed below:

[0124] G c =G ω1 -G ω2 ;

[0125] Wherein, Gω1 represents the first admittance and Gω2 represents the second admittance.

[0126] S32. Based on the admittance of the Y-capacitance to ground, the expression for the Y-capacitance to ground is obtained:

[0127]

[0128] The insulation resistance value is obtained by the following expression:

[0129] G c1 =ω1*CY,G c2 =ω2*CY.

[0130] Please refer to Figure 4 Embodiment two of the present invention is as follows:

[0131] An insulation testing terminal 1 for a DC bus in an energy storage system includes a memory 2, a processor 3, and a computer program stored in the memory 2 and executable on the processor 3. When the processor 3 executes the computer program, it implements an insulation testing method for a DC bus in an energy storage system according to Embodiment 1.

[0132] In summary, the present invention provides a DC bus insulation detection method and terminal for an energy storage system. On the DC bus, a composite pulse current source containing different first frequency pulses and second frequency pulses is injected to obtain the voltage response of the DC bus. Then, admittance analysis is performed on the voltage response to obtain the Y capacitance to ground and insulation resistance values. The pulse response and admittance analysis calculation method has a short detection time and is not limited by the installation location.

[0133] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for detecting the insulation of a DC bus in an energy storage system, characterized in that, Includes the following steps: S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source. The expression for the composite pulse current source is as follows: ； Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency; S2. Calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively, based on the voltage response; S3. Calculate the Y-capacitance to ground and the insulation resistance of the DC bus based on the first admittance and the second admittance. The procedure preceding step S1 also includes: S0. Perform equivalent insulation verification on the DC bus to ground to obtain the total Y-capacitance CY of the DC bus to ground, which is expressed as follows: ； Where Yn represents a single Y-capacitor to ground, and N represents an integer; The equivalent total insulation resistance value of the DC bus is also obtained, and its expression is as follows: ； Wherein, Rn represents the value of a single insulation resistance; Step S3 includes: S31. Calculate the Y-capacitance admittance to ground Gc based on the first admittance and the second admittance, as expressed below: ； Wherein, Gω1 represents the first admittance, and Gω2 represents the second admittance; S32. Based on the admittance of the Y-capacitor to ground, the Y-capacitor to ground CY is obtained, and its expression is: ； The insulation resistance value is obtained by the following expression: ； Where ω1 represents the first frequency and ω2 represents the second frequency.

2. The method for detecting the insulation of a DC bus in an energy storage system according to claim 1, characterized in that, Step S2 specifically involves: By combining the admittance transfer function, the first admittance is obtained by performing FFT calculation on the portion of the voltage response corresponding to the first frequency pulse; By combining the admittance transfer function, an FFT is performed on the portion of the voltage response corresponding to the second frequency pulse to obtain the second admittance.

3. The method for detecting the insulation of a DC bus in an energy storage system according to claim 1, characterized in that, Step S1 includes: Based on step S0, the expression for the voltage response V is obtained as follows: ； Where ω represents the current frequency.

4. A DC bus insulation detection terminal for an energy storage system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it performs the following steps: S1. Inject a composite pulse current source containing a first frequency pulse and a second frequency pulse between the DC bus and ground, and collect the voltage response of the DC bus corresponding to the composite pulse current source. The expression for the composite pulse current source is as follows: ； Where k represents the peak value of the current amplitude at the corresponding frequency, ω1 represents the first frequency, and ω2 represents the second frequency; S2. Based on the voltage response, calculate the first admittance and the second admittance corresponding to the first frequency pulse and the second frequency pulse, respectively; S3. Based on the first admittance and the second admittance, obtain the Y capacitance to ground and the insulation resistance value of the DC bus; The procedure preceding step S1 also includes: S0. Perform equivalent insulation calculations on the DC bus to ground to obtain the total equivalent Y-capacitance of the DC bus to ground, as expressed below: ； Where Yn represents a single Y-capacitor to ground, and N represents an integer; The equivalent total insulation resistance value of the DC bus is also obtained, and its expression is as follows: ； Wherein, Rn represents the value of a single insulation resistance; Step S3 includes: S31. Calculate the Y-capacitor admittance to ground based on the first admittance and the second admittance, as expressed below: ； Wherein, Gω1 represents the first admittance, and Gω2 represents the second admittance; S32. Based on the admittance of the Y-capacitor to ground, the Y-capacitor to ground is obtained, and its expression is: ； The insulation resistance value is obtained by the following expression: ； Where ω1 represents the first frequency and ω2 represents the second frequency.

5. The DC bus insulation detection terminal for an energy storage system according to claim 4, characterized in that, Step S2 specifically involves: By combining the admittance transfer function, the first admittance is obtained by performing FFT calculation on the portion of the voltage response corresponding to the first frequency pulse; By combining the admittance transfer function, an FFT is performed on the portion of the voltage response corresponding to the second frequency pulse to obtain the second admittance.

6. The DC bus insulation detection terminal for an energy storage system according to claim 4, characterized in that, Step S1 includes: Based on step S0, the expression for the voltage response is obtained as follows: ； Where ω represents the current frequency.

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