Common-mode interference detection method and system for high-voltage battery energy storage system

Abstract

The application belongs to the field of energy storage systems, and discloses a common-mode interference detection method and system for a high-voltage battery energy storage system, which comprises the following steps: obtaining the positive electrode-to-ground equivalent stray capacitance value and the negative electrode-to-ground equivalent stray capacitance value of a battery unit in the high-voltage battery energy storage system; according to the positive electrode-to-ground equivalent stray capacitance value and the negative electrode-to-ground equivalent stray capacitance value of the battery unit, a positive electrode stray capacitor is installed between the positive electrode of the battery unit and the ground wire, and the voltage value of the positive electrode stray capacitor is detected to obtain the actual measurement value of the positive electrode common-mode interference voltage of the battery unit; a negative electrode stray capacitor is installed between the negative electrode of the battery unit and the ground wire, and the voltage value of the negative electrode stray capacitor is detected to obtain the actual measurement value of the negative electrode common-mode interference voltage of the battery unit. The voltage value of the stray capacitor is used to quantify the common-mode voltage value of the battery unit, so that the quantitative detection of the common-mode interference of the high-voltage battery energy storage system is realized.

Description

Technical Field

[0001] This invention belongs to the field of energy storage systems and relates to a common-mode interference detection method and system for high-voltage battery energy storage systems. Background Technology

[0002] Energy storage plays a crucial role in energy system transformation and the construction of the energy internet. It is an important means to improve the flexibility, economy, and security of the power system, solve the problem of renewable energy consumption, and is also a core element in promoting open sharing and flexible trading of energy production and consumption, and achieving multi-energy synergy. Larger capacity energy storage units are necessary for improving the efficiency of energy storage systems and reducing manufacturing costs, and also significantly reduce the difficulty of large-scale integration of energy storage power stations. Higher voltage battery energy storage systems are a necessary path to achieving larger capacity energy storage units. Higher voltage battery systems refer to increasing the upper limit of the operating voltage of battery energy storage systems to over 900V. While high-voltage battery energy storage systems are an effective means to reduce costs and increase efficiency, the failure mechanisms of high-voltage battery systems are still unclear, and the protection mechanisms are not yet perfect. It is necessary to balance the coordinated development of high safety, high efficiency, and low cost, and to conduct targeted research and experimental verification of relevant mechanisms to lay the foundation for the widespread application of high-voltage battery systems.

[0003] Common-mode interference refers to common signal interference simultaneously applied to multiple input signal interfaces. The interference voltage has the same amplitude on both the signal line and its return line, with the ground or equipment casing as the reference unit. The interference current loop flows in the loop formed by the conductor and the reference object. In energy storage systems, parasitic capacitances exist between the battery and the casing, between the battery and the rack, between the DC bus and the rack, between the power module and the casing, and between long cables and ground. During the converter modulation process, common-mode voltage and current interference are generated on the DC side, consistent with the switching frequency of the power module.

[0004] With the gradual increase in voltage levels of high-voltage battery energy storage systems, common-mode interference has become increasingly severe. Voltage spikes from common-mode interference can cause aging of the battery insulation layer and even dielectric breakdown, leading to battery safety accidents. Furthermore, they exacerbate the uneven distribution of the electric field within the battery energy storage system, increasing the risk of arcing. In addition, after a local fault arc occurs in the battery energy storage system, crosstalk interference can also generate common-mode signals, which couple to normal lines through conduction and electromagnetic induction, causing similar characteristics to fault arcs in normal lines, increasing the difficulty of fault arc identification and ultimately exacerbating arcing faults in the system. Simultaneously, common-mode current flowing through the ground leakage capacitance of electronic circuits such as the battery management system can also cause battery management system failure or detection errors. Therefore, accurately measuring the intensity of common-mode interference has become a major factor affecting the safe and reliable operation of battery energy storage systems. However, there is currently no precise measurement method for common-mode interference in high-voltage battery energy storage systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a common-mode interference detection method and system for high-voltage battery energy storage systems.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a common-mode interference detection method for a high-voltage battery energy storage system, comprising: acquiring the equivalent parasitic capacitance value of the positive electrode to ground and the equivalent parasitic capacitance value of the negative electrode to ground of a battery cell within the high-voltage battery energy storage system; based on the equivalent parasitic capacitance value of the positive electrode to ground and the equivalent parasitic capacitance value of the negative electrode to ground of the battery cell, installing a positive parasitic capacitor between the positive electrode and the grounding wire of the battery cell, and detecting the voltage value of the positive parasitic capacitor to obtain a measured value of the common-mode interference voltage of the positive electrode of the battery cell; installing a negative parasitic capacitor between the negative electrode and the grounding wire of the battery cell, and detecting the voltage value of the negative parasitic capacitor to obtain a measured value of the common-mode interference voltage of the negative electrode of the battery cell.

[0008] Optionally, it also includes: obtaining the converter common-mode voltage of the battery cell in the high-voltage battery energy storage system; and obtaining the theoretical value of the common-mode interference voltage of the battery cell based on the converter common-mode voltage of the battery cell using the following formula:

[0009] u cm H1(s)=u cmv

[0010]

[0011] Among them, u cm u is the common-mode voltage of the inverter for the battery cell. cmvH1(s) is the theoretical value of the common-mode interference voltage of the battery cell; H1(s) is the transfer function of the theoretical value of the common-mode interference voltage of the battery cell to the common-mode voltage of the converter; s is the mathematical operation symbol when the circuit is transformed from the time domain to the complex frequency domain; R = R g +R0 / 3, R g R is the resistance value of the grounding grid, R0 is the resistance value of the grid-side resistance, and L is the resistance value of the grid-side resistance. f C is the filter inductance value of the converter's filter. v1 C is the equivalent parasitic capacitance of the positive terminal to ground. v2 This is the equivalent parasitic capacitance of the negative electrode to ground.

[0012] Based on the theoretical value of the common-mode interference voltage of the battery cell, the theoretical values ​​of the positive electrode common-mode interference voltage and the negative electrode common-mode interference voltage of the battery cell are obtained.

[0013] Optionally, obtaining the theoretical values ​​of the positive and negative common-mode interference voltages of the battery cell based on the theoretical value of the common-mode interference voltage of the battery cell includes: obtaining the theoretical values ​​of the positive and negative common-mode interference voltages of the battery cell using the following formula based on the theoretical value of the common-mode interference voltage of the battery cell:

[0014]

[0015] Among them, u cv1 u is the theoretical value of the positive common-mode interference voltage of the battery cell. cv2 This is the theoretical value of the negative electrode common-mode interference voltage of the battery cell.

[0016] Optionally, it also includes: when the error between the theoretical value of the positive common-mode interference voltage of the battery cell and the measured value of the positive common-mode interference voltage of the battery cell is within a preset error range, the measured value of the current positive common-mode interference voltage of the battery cell is taken as the positive common-mode interference voltage value of the battery cell; otherwise, the equivalent parasitic capacitance value of the positive terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the positive terminal to ground of the battery cell, a positive parasitic capacitor is added between the positive terminal of the battery cell and the grounding wire, and the voltage value of the positive parasitic capacitor is detected to update the positive common-mode interference voltage of the battery cell. Measured value; when the error between the theoretical value of the negative common-mode interference voltage of the battery cell and the measured value of the negative common-mode interference voltage of the battery cell is within the preset error range, the measured value of the current negative common-mode interference voltage of the battery cell is taken as the negative common-mode interference voltage value of the battery cell; otherwise, the equivalent parasitic capacitance value of the negative terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the negative terminal to ground of the battery cell, a negative parasitic capacitor is added between the negative terminal of the battery cell and the grounding wire, and the voltage value of the negative parasitic capacitor is detected to update the measured value of the negative common-mode interference voltage of the battery cell.

[0017] Optionally, it also includes: detecting the current value of the positive electrode parasitic capacitance to obtain the measured value of the positive electrode common-mode interference current of the battery cell; detecting the current value of the negative electrode parasitic capacitance to obtain the measured value of the negative electrode common-mode interference current of the battery cell.

[0018] Optionally, it also includes: obtaining the common-mode voltage of the inverter for the battery cell within the high-voltage battery energy storage system; and obtaining the theoretical value of the common-mode interference current of the battery cell using the following formula based on the common-mode voltage of the inverter for the battery cell:

[0019] u cm H2(s)=i cm

[0020]

[0021] Among them, u cm i is the common-mode voltage of the inverter for the battery cell. cm H2(s) is the theoretical value of the common-mode interference current of the battery cell; H2(s) is the transfer function of the theoretical value of the common-mode interference current of the battery cell to the common-mode voltage of the converter; s is the mathematical operation symbol when the circuit is transformed from the time domain to the complex frequency domain; R = R g +R0 / 3, R g R is the resistance value of the grounding grid, R0 is the resistance value of the grid-side resistance, and L is the resistance value of the grid-side resistance. f C is the filter inductance value of the filter in the inverter of the battery cell. v1 C is the equivalent parasitic capacitance of the positive terminal to ground. v2 This is the equivalent parasitic capacitance of the negative electrode to ground.

[0022] Based on the theoretical values ​​of the common-mode interference current of the battery cell, the equivalent parasitic capacitance of the positive electrode to ground, and the equivalent parasitic capacitance of the negative electrode to ground, the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell are obtained.

[0023] Optionally, obtaining the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell based on the theoretical values ​​of the common-mode interference current of the battery cell and the equivalent parasitic capacitance values ​​of the positive and negative electrodes to ground includes: obtaining the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell using the following formula:

[0024]

[0025]

[0026] Among them, i cm1 i is the theoretical value of the positive common-mode interference current of the battery cell.cm2 This is the theoretical value of the negative electrode common-mode interference current of the battery cell.

[0027] Optionally, it also includes: when the error between the theoretical value of the positive common-mode interference current of the battery cell and the measured value of the positive common-mode interference current of the battery cell is within a preset error range, the measured value of the current positive common-mode interference current of the battery cell is used as the positive common-mode interference current value of the battery cell; otherwise, the equivalent parasitic capacitance value of the positive terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the positive terminal to ground of the battery cell, a positive parasitic capacitor is added between the positive terminal of the battery cell and the grounding wire, and the current value of the positive parasitic capacitor is detected to update the positive common-mode interference current of the battery cell. Measured value; when the error between the theoretical value of the negative common-mode interference current of the battery cell and the measured value of the negative common-mode interference current of the battery cell is within the preset error range, the current measured value of the negative common-mode interference current of the battery cell is taken as the negative common-mode interference current value of the battery cell; otherwise, the equivalent parasitic capacitance value of the negative terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the negative terminal to ground of the battery cell, a negative parasitic capacitor is added between the negative terminal of the battery cell and the grounding wire, and the current value of the negative parasitic capacitor is detected to update the measured value of the negative common-mode interference current of the battery cell.

[0028] In a second aspect, the present invention provides a common-mode interference detection system for a high-voltage battery energy storage system, comprising a positive parasitic capacitor, a negative parasitic capacitor, and a voltage detection device; one end of the positive parasitic capacitor is connected to the positive terminal of a battery cell within the high-voltage battery energy storage system, and the other end is connected to the grounding wire of the battery cell within the high-voltage battery energy storage system; one end of the negative parasitic capacitor is connected to the negative terminal of a battery cell within the high-voltage battery energy storage system, and the other end is connected to the grounding wire of the battery cell within the high-voltage battery energy storage system; the voltage detection device is connected to both the positive and negative parasitic capacitors; wherein the capacitance value of the positive parasitic capacitor is the equivalent parasitic capacitance value of the positive terminal of the battery cell to ground, and the capacitance value of the negative parasitic capacitor is the equivalent parasitic capacitance value of the negative terminal of the battery cell to ground.

[0029] Optionally, a current detection device is also included; the current detection device is connected to both the positive and negative parasitic capacitances.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention discloses a common-mode interference detection method for high-voltage battery energy storage systems. It involves installing a positive parasitic capacitor between the positive terminal of the battery cell and the grounding wire, then detecting the voltage value of the positive parasitic capacitor, and using this detected voltage value as the measured value of the common-mode interference voltage at the positive terminal of the battery cell. Simultaneously, a negative parasitic capacitor is installed between the negative terminal of the battery cell and the grounding wire, and the voltage value of this negative parasitic capacitor is also detected. This detected voltage value is used as the measured value of the common-mode interference voltage at the negative terminal of the battery cell. The principle of the entire detection method is to quantify the common-mode voltage value of the battery cell using the voltage value of the parasitic capacitor, thereby achieving quantitative detection of common-mode interference in the high-voltage battery energy storage system. Furthermore, the quantified common-mode voltage value is used to measure the common-mode impact experienced by the high-voltage battery energy storage system and to quantify the impact of the energy storage battery system on the ground insulation material. It can also serve as a reference standard to measure the reliability of the high-voltage battery energy storage system under the influence of common-mode voltage.

[0032] Furthermore, theoretical values ​​of common-mode interference in high-voltage battery energy storage systems are obtained through theoretical derivation. This can be used to assist in the design of high-voltage battery energy storage systems and to verify the accuracy of measured values. Attached Figure Description

[0033] Figure 1 This is a flowchart of the common-mode interference detection method for a high-voltage battery energy storage system according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of the PCS circuit model according to an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a common-mode loop circuit model according to an embodiment of the present invention.

[0036] Figure 4 This is a simplified common-mode loop circuit model diagram according to an embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of a second-order RLC circuit model according to an embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of the common-mode interference detection system of the high-voltage battery energy storage system according to an embodiment of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] As described in the background section, in high-voltage battery energy storage systems, the system casing or rack is directly grounded and has parasitic capacitance, resulting in common-mode voltage and current effects between the positive and negative terminals and ground. These common-mode voltage and current issues become the main factors affecting the insulation of the battery system. For high-voltage battery energy storage systems, the PCS (Power Conversion System) primarily uses PWM (Pulse Width Modulation) technology to convert DC voltage to AC voltage, completing the energy exchange between the energy storage system and the grid. During the rapid switching of the switching transistors in the PCS, a pulse voltage with fast rise and fall edges, high repetition rate, and high amplitude is generated, i.e., the common-mode voltage.

[0042] Taking a three-level topology employing sinusoidal pulse width modulation (PWM) as an example, without loss of generality, the common-mode voltage generation mechanism in a PCS is explained. The basic idea behind different PWM modulation strategies in a PCS is to utilize the principle of equal area to convert a sinusoidal signal into a series of rectangular pulse signals to control the switching transistors' on / off states. Different modulation strategies result in slightly different on / off sequences for the switching transistors in each bridge arm within each switching cycle, but due to the same basic idea, the common-mode voltage generation mechanism is largely consistent. Specifically, within each switching cycle, three-phase modulation waves with a 120° phase difference are compared with the upper and lower triangular carrier waves. When the modulation wave is greater than the upper carrier wave, that phase of the bridge arm outputs a P-level; when it is less than the lower carrier wave, it outputs an N-level; otherwise, it outputs an O-level. According to the definition of common-mode voltage, the arithmetic mean of the voltages output by the three-phase bridge arms of the PCS is the common-mode voltage. The rectangular pulses of the three-phase output voltages are superimposed to form a stepped common-mode voltage pulse.

[0043] Common-mode voltage can enter the energy storage system through the common-mode loop composed of parasitic capacitance, grounding frame and grounding grid. On the one hand, it will deteriorate the electromagnetic environment of the battery cell, change the electric field distribution inside the battery module, cause the local field strength to increase, and exacerbate the risk of insulation breakdown of the battery cell. On the other hand, the rise time of common-mode voltage and common-mode current is extremely steep and the frequency is extremely high, which will cause an increase in the dielectric loss inside the insulation and accelerate the insulation aging process.

[0044] Based on this, the present invention provides a common-mode interference detection method and system for high-voltage battery energy storage systems, which can quantify the common-mode interference of high-voltage battery energy storage systems, thereby measuring the common-mode impact on high-voltage battery energy storage systems and the reliability of high-voltage battery energy storage systems under the influence of common-mode voltage, thus providing a reference for optimizing the design of high-voltage battery energy storage systems and improving the operational reliability of systems.

[0045] The present invention will now be described in further detail with reference to the accompanying drawings:

[0046] See Figure 1 In one embodiment of the present invention, a common-mode interference detection method for a high-voltage battery energy storage system is provided, which can be used to accurately quantify the common-mode voltage of the high-voltage battery energy storage system. Specifically, the common-mode interference detection method for the high-voltage battery energy storage system includes the following steps:

[0047] S1: Obtain the equivalent parasitic capacitance value of the positive electrode to ground and the equivalent parasitic capacitance value of the negative electrode to ground of the battery cell in the high-voltage battery energy storage system.

[0048] S2: Based on the equivalent parasitic capacitance value of the positive electrode to ground and the equivalent parasitic capacitance value of the negative electrode to ground of the battery cell, a positive parasitic capacitor is installed between the positive electrode of the battery cell and the grounding wire, and the voltage value of the positive parasitic capacitor is detected to obtain the measured value of the common-mode interference voltage of the positive electrode of the battery cell.

[0049] S3: Install a negative parasitic capacitor between the negative terminal of the battery cell and the grounding wire, and detect the voltage value of the negative parasitic capacitor to obtain the measured value of the negative common-mode interference voltage of the battery cell.

[0050] The battery cell is a combination of individual battery cells connected to the same PCS. A high-voltage battery energy storage system may contain only one battery cell or multiple battery cells. In the case of multiple battery cells, common-mode interference detection can be performed on each battery cell separately.

[0051] In summary, the common-mode interference detection method for high-voltage battery energy storage systems of this invention involves installing a positive parasitic capacitor between the positive terminal and the grounding wire of the battery cell, then detecting the voltage value of the positive parasitic capacitor, and using the detected voltage value of the positive parasitic capacitor as the measured value of the common-mode interference voltage of the battery cell. Simultaneously, a negative parasitic capacitor is installed between the negative terminal and the grounding wire of the battery cell, and the voltage value of the negative parasitic capacitor is detected, using the detected voltage value of the positive parasitic capacitor as the measured value of the common-mode interference voltage of the battery cell. The principle of the entire detection method is to quantify the common-mode voltage value of the battery cell using the voltage value of the parasitic capacitor, thereby achieving quantitative detection of common-mode interference in the high-voltage battery energy storage system. Furthermore, the quantified common-mode voltage value is used to measure the common-mode impact experienced by the high-voltage battery energy storage system and to quantify the impact of the energy storage battery system on the ground insulation material. It can also serve as a reference standard to measure the reliability of the high-voltage battery energy storage system under the influence of common-mode voltage.

[0052] In one possible implementation, the equivalent parasitic capacitance values ​​of the positive electrode to ground and the negative electrode to ground of the battery cell can both be obtained through actual measurement. Generally, an LCR meter, digital multimeter, withstand voltage tester, and discharge resistor method can be used for on-site measurement.

[0053] In one possible implementation, the common-mode interference detection method for the high-voltage battery energy storage system further includes: detecting the current value of the positive electrode parasitic capacitance to obtain the measured value of the positive electrode common-mode interference current of the battery cell; and detecting the current value of the negative electrode parasitic capacitance to obtain the measured value of the negative electrode common-mode interference current of the battery cell.

[0054] Specifically, the current values ​​of the positive and negative parasitic capacitances are used as the measured values ​​of the common-mode interference current of the positive and negative electrodes of the battery cell, respectively. This enables the accurate quantification of the common-mode interference current of the high-voltage battery energy storage system, providing a reference basis for further clarifying the impact of the common-mode current on the high-voltage battery energy storage system, and also promoting the improvement of the reliability of the high-voltage battery energy storage system.

[0055] In one possible implementation, the common-mode interference detection method for high-voltage battery energy storage systems of the present invention also provides a method for calculating the theoretical value of the common-mode interference voltage of a battery cell, specifically including the following steps:

[0056] First, obtain the common-mode voltage of the inverter for each battery cell in the high-voltage battery energy storage system. Based on the common-mode voltage of the inverter for each battery cell, obtain the theoretical value of the common-mode interference voltage for the battery cell using the following formula:

[0057] u cm H1(s)=u cmv

[0058]

[0059] Among them, u cm u is the common-mode voltage of the inverter for the battery cell. cmv H1(s) is the theoretical value of the common-mode interference voltage of the battery cell; H1(s) is the transfer function of the theoretical value of the common-mode interference voltage of the battery cell to the common-mode voltage of the converter; s is the mathematical operation symbol when the circuit is transformed from the time domain to the complex frequency domain; R = R g +R0 / 3, R g R is the resistance value of the grounding grid, R0 is the resistance value of the grid-side resistance, and L is the resistance value of the grid-side resistance. f C is the filter inductance value of the converter's filter. v1 C is the equivalent parasitic capacitance of the positive terminal to ground. v2 This is the equivalent parasitic capacitance of the negative electrode to ground.

[0060] Then, based on the theoretical value of the common-mode interference voltage of the battery cell, the theoretical values ​​of the positive electrode common-mode interference voltage and the negative electrode common-mode interference voltage of the battery cell are obtained.

[0061] Optionally, a method for calculating the theoretical value of the common-mode interference current of the battery cell is also provided, specifically including the following steps:

[0062] First, obtain the common-mode voltage of the inverter for each battery cell in the high-voltage battery energy storage system. Based on the common-mode voltage of the inverter for each battery cell, obtain the theoretical value of the common-mode interference current for the battery cell using the following formula:

[0063] u cm H2(s)=i cm

[0064]

[0065] Among them, i cm H2(s) is the theoretical value of the common-mode interference current of the battery cell; H2(s) is the transfer function of the theoretical value of the common-mode interference current of the battery cell to the common-mode voltage of the converter.

[0066] Then, based on the theoretical value of the common-mode interference current of the battery cell, the equivalent parasitic capacitance of the positive electrode to ground and the equivalent parasitic capacitance of the negative electrode to ground of the battery cell, the theoretical values ​​of the positive electrode common-mode interference current and the negative electrode common-mode interference current of the battery cell are obtained.

[0067] For details, see Figure 2 The circuit model of the energy storage system PCS considering the parasitic capacitance parameters of the battery cells to ground is shown. Wherein, C... v1 and C v2 These are the equivalent positive and negative parasitic capacitances, respectively; u cv1 and u cv2These are the positive and negative parasitic capacitance voltage values, respectively, which are also the common-mode voltages conducted to the positive and negative busbars; i cm1 and i cm2 These are the positive common-mode current value and the negative common-mode current value, respectively; L f C is the filter inductor in an LCL filter. f L1 is the filter capacitor in the LCL filter, L0 is the grid-side filter inductor in the LCL filter; p is the DC-side positive bus, o is the DC-side neutral point, n is the DC-side negative bus, N is the grid neutral point, and N' is the LCL filter-side neutral point.

[0068] Based on Kirchhoff's voltage law, the three-phase circuit equation is as follows:

[0069]

[0070] Among them, u jo The output voltage of phase j; i j i is the output current of phase j of the converter; k For k-phase grid-side current; u k0 e is the voltage across the k-phase transmission line resistance. k Let be the voltage of the k-phase power grid; j = A, B, C; k = a, b, c.

[0071] Considering the three-phase symmetry of the power grid system, then Adding the three phases in equation (1) together, we get:

[0072]

[0073] Furthermore, since there is no direct electrical connection between point N' and point O, the zero-sequence current will not flow through the filter capacitor C. f The theoretical value of the common-mode interference current i can be obtained. cm The expression:

[0074]

[0075] Theoretical value of common-mode interference current i cm It can also be viewed as flowing through the parasitic capacitance C at the positive terminal. v1 Positive common-mode interference current i cm1 With the parasitic capacitance C flowing through the negative electrode v2 The theoretical value of negative common-mode interference current i cm2 The sum of

[0076]

[0077] Since the AC system grounding point and the DC system grounding point are not the same point, let's assume the impedance between the two points is Z. gTherefore, the voltage difference u between the neutral point N of the power grid and the DC side midpoint o is... No The expression is:

[0078]

[0079] From equation (5), we can obtain:

[0080]

[0081] Define the DC voltage differential component U of the converter. dm :

[0082] u dm =u po -u on (7)

[0083] The common-mode voltage u of the inverter for the battery cell cm It is the arithmetic mean of the output voltages of the three-phase bridge arms of the converter:

[0084]

[0085] Substituting equations (3) to (8) into equation (2) and rearranging, we get:

[0086]

[0087] Based on the mathematical expression derived from equation (9), the common-mode loop circuit model is obtained, as follows: Figure 3 As shown.

[0088] Meanwhile, considering the consistency of the parasitic capacitance of the positive and negative electrodes of the battery cell, assuming C v1 =C v2 =C v Equation (9) is further rearranged into Equation (10):

[0089]

[0090] Based on equation (10), the common-mode loop circuit model is further simplified to obtain the simplified common-mode loop circuit model, as follows: Figure 4 As shown, it can be seen that there are two excitation sources in the simplified common-mode loop circuit model:

[0091] 1. The differential-mode component of the DC voltage generated by the three-level PCS is 0.5µA. dm This is caused by the uneven voltage distribution between the positive and negative bus capacitors, which can be reduced to a very small value through a midpoint balancing strategy. Therefore, the 0.5u value will not be considered in subsequent analyses. dm 2. The common-mode voltage u of the converter generated by the three-level PCS cm The source of this is the superposition of zero-sequence voltage components generated by the three-phase bridge arms.

[0092] Therefore, the simplified common-mode loop circuit model can be further simplified to a second-order RLC circuit model, such as... Figure 5 As shown. And in general, C can be considered... v >>C g L f >>L0, L f >>L g Therefore, the model parameters of the second-order RLC circuit are obtained as C = 2C. v L = L f / 3, R = R g +R0 / 3.

[0093] Based on the second-order RLC circuit model, the transfer function of the theoretical value of the common-mode interference voltage of the battery cell to the common-mode voltage of the converter can be obtained:

[0094]

[0095] And the transfer function of the theoretical value of the common-mode interference current of the battery cell to the common-mode voltage of the converter:

[0096]

[0097] Based on this, the theoretical value of the common-mode interference voltage of the battery cell can be obtained by equation (11) above, and the theoretical value of the common-mode interference current of the battery cell can be obtained by equation (12).

[0098] Assuming the parasitic capacitances at the positive and negative terminals are not the same, C = C v1 +C v2 Then equation (11) can be modified as follows:

[0099]

[0100] Equation (12) can be modified as follows:

[0101]

[0102] In one possible implementation, obtaining the theoretical values ​​of the positive and negative common-mode interference voltages of the battery cell based on the theoretical values ​​of the common-mode interference voltage of the battery cell includes:

[0103] Based on the theoretical value of the common-mode interference voltage of the battery cell, the theoretical values ​​of the positive and negative common-mode interference voltages of the battery cell are obtained using the following formula:

[0104]

[0105] Among them, u cv1u is the theoretical value of the positive common-mode interference voltage of the battery cell. cv2 This is the theoretical value of the negative electrode common-mode interference voltage of the battery cell.

[0106] The process of obtaining the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell based on the theoretical values ​​of the common-mode interference current of the battery cell, the equivalent parasitic capacitance values ​​of the positive and negative electrodes to ground, and the equivalent parasitic capacitance values ​​of the negative electrode to ground includes:

[0107] Based on the theoretical values ​​of the common-mode interference current of the battery cell and the equivalent parasitic capacitances of the positive and negative terminals to ground, the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell are obtained using the following formulas:

[0108]

[0109]

[0110] Among them, i cm1 i is the theoretical value of the positive common-mode interference current of the battery cell. cm2 This is the theoretical value of the negative electrode common-mode interference current of the battery cell.

[0111] In one possible implementation, the common-mode interference detection method for the high-voltage battery energy storage system further includes:

[0112] When the error between the theoretical value of the positive common-mode interference voltage of the battery cell and the measured value of the positive common-mode interference voltage of the battery cell is within the preset error range, the measured value of the current positive common-mode interference voltage of the battery cell is taken as the positive common-mode interference voltage value of the battery cell; otherwise, the equivalent parasitic capacitance value of the positive terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the positive terminal to ground of the battery cell, a positive parasitic capacitor is added between the positive terminal of the battery cell and the grounding wire, and the voltage value of the positive parasitic capacitor is detected to update the measured value of the positive common-mode interference voltage of the battery cell. When the error between the theoretical value of the negative common-mode interference voltage of the battery cell and the measured value of the negative common-mode interference voltage of the battery cell is within the preset error range, the measured value of the current negative common-mode interference voltage of the battery cell is taken as the negative common-mode interference voltage value of the battery cell; otherwise, the equivalent parasitic capacitance value of the negative terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the negative terminal to ground of the battery cell, a negative parasitic capacitor is added between the negative terminal of the battery cell and the grounding wire, and the voltage value of the negative parasitic capacitor is detected to update the measured value of the negative common-mode interference voltage of the battery cell.

[0113] Optionally, the common-mode interference detection method for the high-voltage battery energy storage system further includes:

[0114] When the error between the theoretical value of the positive common-mode interference current of the battery cell and the measured value of the positive common-mode interference current of the battery cell is within the preset error range, the measured value of the positive common-mode interference current of the current battery cell is taken as the value of the positive common-mode interference current of the battery cell; otherwise, the equivalent parasitic capacitance value of the positive terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the positive terminal to ground of the battery cell, a positive parasitic capacitor is added between the positive terminal of the battery cell and the grounding wire, and the current value of the positive parasitic capacitor is detected to update the measured value of the positive common-mode interference current of the battery cell. When the error between the theoretical value of the negative common-mode interference current of the battery cell and the measured value of the negative common-mode interference current of the battery cell is within the preset error range, the measured value of the current negative common-mode interference current of the battery cell is taken as the negative common-mode interference current value of the battery cell; otherwise, the equivalent parasitic capacitance value of the negative terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the negative terminal to ground of the battery cell, a negative parasitic capacitor is added between the negative terminal of the battery cell and the grounding wire, and the current value of the negative parasitic capacitor is detected to update the measured value of the negative common-mode interference current of the battery cell.

[0115] Specifically, based on the theoretical values ​​of the positive common-mode interference voltage, negative common-mode interference voltage, positive common-mode interference current, and negative common-mode interference current of the battery cell, the measured values ​​of the positive and negative common-mode interference voltages of the battery cell are verified. This avoids inaccurate measured values ​​due to improper operation during the measurement process. Furthermore, when the error between the measured value and the theoretical value is large, the accuracy of the measurement can be ensured by repeating the measurement.

[0116] See Figure 6 In another embodiment of the present invention, a common-mode interference detection system for a high-voltage battery energy storage system is provided, which can be used to implement the common-mode interference detection method for a high-voltage battery energy storage system in the above embodiments. Specifically, the common-mode interference detection system for a high-voltage battery energy storage system includes: a positive parasitic capacitor, a negative parasitic capacitor, and a voltage detection device; one end of the positive parasitic capacitor is connected to the positive terminal of the battery cell in the high-voltage battery energy storage system, and the other end is connected to the grounding wire of the battery cell in the high-voltage battery energy storage system; one end of the negative parasitic capacitor is connected to the negative terminal of the battery cell in the high-voltage battery energy storage system, and the other end is connected to the grounding wire of the battery cell in the high-voltage battery energy storage system; the voltage detection device is connected to both the positive and negative parasitic capacitors; wherein, the capacitance value of the positive parasitic capacitor is the equivalent parasitic capacitance value of the positive terminal of the battery cell to ground, and the capacitance value of the negative parasitic capacitor is the equivalent parasitic capacitance value of the negative terminal of the battery cell to ground.

[0117] Specifically, in the actual testing process, positive and negative parasitic capacitors are first installed in the high-voltage battery energy storage system. Then, the voltage on the positive and negative parasitic capacitors is detected by a voltage detection device, and used as the measured values ​​of the positive and negative common-mode interference voltages of the battery cells in the high-voltage battery energy storage system, thus completing the common-mode voltage detection in the common-mode interference of the high-voltage battery energy storage system.

[0118] In one possible implementation, the common-mode interference detection system of the high-voltage battery energy storage system further includes a current detection device; the current detection device is connected to both the positive and negative parasitic capacitances.

[0119] Specifically, the current on the parasitic capacitance of the positive electrode and the parasitic capacitance of the negative electrode is detected by a current detection device, and used as the measured value of the common-mode interference current of the positive electrode and the common-mode interference current of the battery cell in the high-voltage battery energy storage system, thus completing the common-mode current detection in the common-mode interference of the high-voltage battery energy storage system.

[0120] Furthermore, for individual battery cells within a battery unit that are difficult to test directly, the measured values ​​of the positive electrode common-mode interference voltage, negative electrode common-mode interference voltage, positive electrode common-mode interference current, and negative electrode common-mode interference current for each battery cell can be obtained through calculation. Specifically, the measured value u of the positive electrode common-mode interference voltage of the nth battery cell... n1 =u c1 The measured value of the negative common-mode interference voltage u of the nth battery cell n2 =u c2 Measured value of the positive common-mode interference current of the nth battery cell Measured value of the negative common-mode interference current of the nth battery cell Where n = 1, 2, ..., N, N is the number of individual battery cells in the battery unit, u c1 The measured value of the positive common-mode interference voltage of the battery cell is u. c2 i represents the measured value of the negative common-mode interference voltage of the battery cell. cv1 i represents the measured value of the positive common-mode interference current of the battery cell. cv2 C represents the measured value of the negative common-mode interference current of the battery cell. n1 C is the equivalent parasitic capacitance of the positive electrode to ground of the nth battery cell. n2 Let be the equivalent parasitic capacitance of the negative electrode of the nth battery cell to ground.

[0121] This invention relates to a common-mode interference detection method and system for high-voltage battery energy storage systems. Based on the principle of common-mode voltage generation and conduction in high-voltage battery energy storage systems, it achieves quantitative detection of common-mode interference in high-voltage battery energy storage systems. It is highly operable, and based on the detection results, the impact of common-mode interference on high-voltage battery energy storage systems can be further quantified, providing a reference for further optimization of high-voltage battery energy storage systems.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A common-mode interference detection method for a high-voltage battery energy storage system, characterized in that, include: Obtain the equivalent parasitic capacitance values ​​of the positive electrode to ground and the equivalent parasitic capacitance values ​​of the negative electrode to ground of the battery cells in the high-voltage battery energy storage system; Based on the equivalent parasitic capacitance values ​​of the positive electrode to ground and the equivalent parasitic capacitance values ​​of the negative electrode to ground of the battery cell, a positive parasitic capacitor is installed between the positive electrode of the battery cell and the grounding wire, and the voltage value of the positive parasitic capacitor is detected to obtain the measured value of the common-mode interference voltage of the positive electrode of the battery cell. A parasitic capacitor is installed between the negative terminal of the battery cell and the grounding wire, and the voltage value of the parasitic capacitor is measured to obtain the measured value of the common-mode interference voltage of the negative terminal of the battery cell.

2. The common-mode interference detection method for high-voltage battery energy storage systems according to claim 1, characterized in that, Also includes: Obtain the common-mode voltage of the converter in the battery cell of the high-voltage battery energy storage system; Based on the common-mode voltage of the inverter of the battery cell, the theoretical value of the common-mode interference voltage of the battery cell is obtained by the following formula: in cm H1(s)=u cmv Among them, u cm u is the common-mode voltage of the inverter for the battery cell. cmv H1(s) is the theoretical value of the common-mode interference voltage of the battery cell; H1(s) is the transfer function of the theoretical value of the common-mode interference voltage of the battery cell to the common-mode voltage of the converter; s is the mathematical operation symbol when the circuit is transformed from the time domain to the complex frequency domain; R = R g +R0 / 3, R g R is the resistance value of the grounding grid, R0 is the resistance value of the grid-side resistance, and L is the resistance value of the grid-side resistance. f C is the filter inductance value of the converter's filter. v1 C is the equivalent parasitic capacitance of the positive terminal to ground. v2 This is the equivalent parasitic capacitance of the negative electrode to ground. Based on the theoretical value of the common-mode interference voltage of the battery cell, the theoretical values ​​of the positive electrode common-mode interference voltage and the negative electrode common-mode interference voltage of the battery cell are obtained.

3. The common-mode interference detection method for high-voltage battery energy storage systems according to claim 2, characterized in that, The process of obtaining the theoretical values ​​of the positive and negative common-mode interference voltages of the battery cell based on the theoretical values ​​of the common-mode interference voltage of the battery cell includes: Based on the theoretical value of the common-mode interference voltage of the battery cell, the theoretical values ​​of the positive and negative common-mode interference voltages of the battery cell are obtained using the following formula: Among them, u cv1 u is the theoretical value of the positive common-mode interference voltage of the battery cell. cv2 This is the theoretical value of the negative electrode common-mode interference voltage of the battery cell.

4. The common-mode interference detection method for high-voltage battery energy storage systems according to claim 2, characterized in that, Also includes: When the error between the theoretical value of the positive common-mode interference voltage of the battery cell and the measured value of the positive common-mode interference voltage of the battery cell is within the preset error range, the measured value of the current positive common-mode interference voltage of the battery cell is taken as the positive common-mode interference voltage value of the battery cell; otherwise, the equivalent parasitic capacitance value of the positive terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the positive terminal to ground of the battery cell, a positive parasitic capacitor is added between the positive terminal of the battery cell and the grounding wire, and the voltage value of the positive parasitic capacitor is detected to update the measured value of the positive common-mode interference voltage of the battery cell. When the error between the theoretical value of the negative common-mode interference voltage of the battery cell and the measured value of the negative common-mode interference voltage of the battery cell is within the preset error range, the measured value of the current negative common-mode interference voltage of the battery cell is taken as the negative common-mode interference voltage value of the battery cell; otherwise, the equivalent parasitic capacitance value of the negative terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the negative terminal to ground of the battery cell, a negative parasitic capacitor is added between the negative terminal of the battery cell and the grounding wire, and the voltage value of the negative parasitic capacitor is detected to update the measured value of the negative common-mode interference voltage of the battery cell.

5. The common-mode interference detection method for a high-voltage battery energy storage system according to claim 1, characterized in that, Also includes: The measured value of the common-mode interference current of the positive electrode is obtained by detecting the current value of the parasitic capacitance of the positive electrode; The measured value of the common-mode interference current of the negative electrode is obtained by detecting the current value of the parasitic capacitance of the negative electrode.

6. The common-mode interference detection method for a high-voltage battery energy storage system according to claim 5, characterized in that, Also includes: Obtain the common-mode voltage of the converter in the battery cell of the high-voltage battery energy storage system; Based on the common-mode voltage of the battery cell's converter, the theoretical value of the common-mode interference current of the battery cell can be obtained using the following formula: u cm H2(s)=i cm Among them, u cm i is the common-mode voltage of the inverter for the battery cell. cm H2(s) is the theoretical value of the common-mode interference current of the battery cell; H2(s) is the transfer function of the theoretical value of the common-mode interference current of the battery cell to the common-mode voltage of the converter; s is the mathematical operation symbol when the circuit is transformed from the time domain to the complex frequency domain; R = R g +R0 / 3, R g R is the resistance value of the grounding grid, R0 is the resistance value of the grid-side resistance, and L is the resistance value of the grid-side resistance. f C is the filter inductance value of the filter in the inverter of the battery cell. v1 C is the equivalent parasitic capacitance of the positive terminal to ground. v2 This is the equivalent parasitic capacitance of the negative electrode to ground. Based on the theoretical values ​​of the common-mode interference current of the battery cell, the equivalent parasitic capacitance of the positive electrode to ground, and the equivalent parasitic capacitance of the negative electrode to ground, the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell are obtained.

7. The common-mode interference detection method for a high-voltage battery energy storage system according to claim 6, characterized in that, The process of obtaining the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell based on the theoretical values ​​of the common-mode interference current of the battery cell, the equivalent parasitic capacitance values ​​of the positive and negative electrodes to ground, and the equivalent parasitic capacitance values ​​of the negative electrode to ground includes: Based on the theoretical values ​​of the common-mode interference current of the battery cell and the equivalent parasitic capacitances of the positive and negative terminals to ground, the theoretical values ​​of the positive and negative common-mode interference currents of the battery cell are obtained using the following formulas: Among them, i cm1 i is the theoretical value of the positive common-mode interference current of the battery cell. cm2 This is the theoretical value of the negative electrode common-mode interference current of the battery cell.

8. The common-mode interference detection method for a high-voltage battery energy storage system according to claim 6, characterized in that, Also includes: When the error between the theoretical value of the positive common-mode interference current of the battery cell and the measured value of the positive common-mode interference current of the battery cell is within the preset error range, the measured value of the positive common-mode interference current of the current battery cell is taken as the value of the positive common-mode interference current of the battery cell; otherwise, the equivalent parasitic capacitance value of the positive terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the positive terminal to ground of the battery cell, a positive parasitic capacitor is added between the positive terminal of the battery cell and the grounding wire, and the current value of the positive parasitic capacitor is detected to update the measured value of the positive common-mode interference current of the battery cell. When the error between the theoretical value of the negative common-mode interference current of the battery cell and the measured value of the negative common-mode interference current of the battery cell is within the preset error range, the measured value of the current negative common-mode interference current of the battery cell is taken as the negative common-mode interference current value of the battery cell; otherwise, the equivalent parasitic capacitance value of the negative terminal to ground of the battery cell is remeasured, and based on the remeasured equivalent parasitic capacitance value of the negative terminal to ground of the battery cell, a negative parasitic capacitor is added between the negative terminal of the battery cell and the grounding wire, and the current value of the negative parasitic capacitor is detected to update the measured value of the negative common-mode interference current of the battery cell.

9. A common-mode interference detection system for a high-voltage battery energy storage system, characterized in that, It includes positive parasitic capacitance, negative parasitic capacitance, and voltage detection device; One end of the positive parasitic capacitor is connected to the positive terminal of the battery cell in the high-voltage battery energy storage system, and the other end is connected to the grounding wire of the battery cell in the high-voltage battery energy storage system. One end of the negative parasitic capacitor is connected to the negative terminal of the battery cell in the high-voltage battery energy storage system, and the other end is connected to the grounding wire of the battery cell in the high-voltage battery energy storage system. The voltage detection device is connected to both the positive and negative parasitic capacitances; Among them, the capacitance value of the positive electrode parasitic capacitance is the equivalent parasitic capacitance value of the positive electrode of the battery cell to ground, and the capacitance value of the negative electrode parasitic capacitance is the equivalent parasitic capacitance value of the negative electrode of the battery cell to ground.

10. The common-mode interference detection system for a high-voltage battery energy storage system according to claim 9, characterized in that, It also includes a current detection device; The current detection device is connected to both the positive and negative parasitic capacitances.

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