Method, device and equipment for monitoring insulation resistance of energy storage system

Abstract

The present invention provides a method, device and equipment for monitoring the insulation resistance of an energy storage system, and relates to the field of energy technology. The method comprises: obtaining current data in the energy storage system collected by a current transformer; injecting a bipolar square wave signal into a single DC bus of the energy storage system; and determining the insulation resistance of the energy storage system based on the current data. The method of the embodiment of the present application effectively takes into account the advantages of both AC injection and DC injection methods, effectively controls cost and complexity while improving insulation monitoring performance, and realizes efficient and accurate monitoring of the insulation resistance of the energy storage system.

Description

Technical Field

[0001] The present invention relates to the field of energy technology, and in particular to a method, device and equipment for monitoring the insulation resistance of an energy storage system. Background Art

[0002] The consequences of a battery pack short circuit are very serious. To avoid the occurrence of a vicious short circuit accident, the DC bus of the energy storage system adopts a floating design, that is, both the positive and negative busbars are insulated from the ground. In order to warn of short circuit faults in advance, the insulation resistance of the positive and negative busbars to the ground can be monitored. When the insulation resistance drops to a certain level, the battery pack will stop running.

[0003] In the related technology, insulation monitoring of energy storage systems includes DC injection and AC injection. Among them, the DC injection method requires the use of a DC sensor to measure the response current. The DC sensor is relatively expensive. When the insulation resistance is large, the DC response current is very small, and the requirements for the DC transformer are further increased. The AC injection method requires measuring the phase of the current relative to the voltage, and obtaining the resistive component in the current by decomposing the virtual and real parts. The synchronization signal generally needs to be transmitted through a dedicated channel, such as a synchronous bus or wireless method. The introduction of the synchronization signal not only increases the system cost and complexity, but also reduces the reliability of the system. Summary of the invention

[0004] The present invention provides a method, device and equipment for monitoring the insulation resistance of an energy storage system, which effectively take into account the advantages of both AC injection and DC injection methods, effectively control the cost and complexity while improving the insulation monitoring performance, and realize efficient and accurate monitoring of the insulation resistance of the energy storage system.

[0005] The present invention provides a method for monitoring the insulation resistance of an energy storage system, comprising the following steps.

[0006] Acquiring current data in the energy storage system collected by a current transformer; injecting a bipolar square wave signal into a single DC bus of the energy storage system;

[0007] The insulation resistance of the energy storage system is determined according to the current data.

[0008] According to a method for monitoring the insulation resistance of an energy storage system provided by the present invention, determining the insulation resistance of the energy storage system according to the current data includes:

[0009] Determine, according to the current data, a current steady-state value of a positive half-wave and a current steady-state value of a negative half-wave corresponding to the energy storage system;

[0010] The insulation resistance of the energy storage system is determined according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave.

[0011] According to a method for monitoring the insulation resistance of an energy storage system provided by the present invention, determining the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system according to the current data includes:

[0012] The current steady-state value of the positive half-wave is determined based on the following method:

[0013] ;

[0014] in, Represents the steady-state value of the current in the positive half-wave; Represents the current data of the positive half wave collected at time a; Represents the current data of the positive half wave collected at time b; Indicates the current change rate corresponding to the positive half-wave;

[0015] The current steady-state value of the negative half-wave is determined based on the following method:

[0016] ;

[0017] in, Indicates the steady-state value of the current in the negative half-wave; Represents the current data of the negative half-wave collected at time a; Represents the current data of the negative half wave collected at time b; Indicates the current change rate corresponding to the negative half-wave.

[0018] According to a method for monitoring the insulation resistance of an energy storage system provided by the present invention, the insulation resistance of the energy storage system is determined according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave, comprising:

[0019] The insulation resistance of the energy storage system is determined as follows:

[0020] ;

[0021] in, Indicates the insulation resistance of the energy storage system; Indicates the voltage value corresponding to the positive half-wave; Indicates the voltage value corresponding to the negative half-wave; Represents the steady-state value of the current in the positive half-wave; Indicates the steady-state value of the current in the negative half-wave.

[0022] According to a method for monitoring the insulation resistance of an energy storage system provided by the present invention, after determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave, the method further comprises:

[0023] When the insulation resistance of the energy storage system is less than a preset value, the injection source device is instructed to perform a target operation; the target operation includes shortening the period of the bipolar square wave signal and / or reducing the injection resistance.

[0024] According to a method for monitoring insulation resistance of an energy storage system provided by the present invention, the current collected by the current transformer is the current in a battery cluster in the energy storage system or the current of a PCS.

[0025] The present invention also provides a monitoring device for insulation resistance of an energy storage system, comprising the following modules:

[0026] An acquisition module is used to acquire current data in the energy storage system collected by a current transformer; a bipolar square wave signal is injected into a single DC bus of the energy storage system;

[0027] A monitoring module is used to determine the insulation resistance of the energy storage system according to the current data.

[0028] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, a method for monitoring the insulation resistance of an energy storage system as described in any one of the above is implemented.

[0029] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method for monitoring the insulation resistance of an energy storage system as described in any one of the above is implemented.

[0030] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the method for monitoring the insulation resistance of an energy storage system as described in any one of the above is implemented.

[0031] The method, device and equipment for monitoring the insulation resistance of the energy storage system provided by the present invention effectively take into account the advantages of both AC injection and DC injection methods by injecting a bipolar square wave signal into a single DC bus of the energy storage system and using an AC transformer to measure the current data in the energy storage system, thereby effectively controlling the cost and complexity while improving the insulation monitoring performance, and realizing efficient and accurate monitoring of the insulation resistance of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a schematic diagram of the method for monitoring the insulation resistance of the energy storage system provided by the present invention.

[0034] Figure 2 It is a schematic diagram of the distributed insulation monitoring system provided by the present invention.

[0035] Figure 3 It is a schematic diagram of voltage and current waveforms of the injection principle provided by the present invention.

[0036] Figure 4 It is an analysis diagram of the sampling and calculation principle of the current waveform provided by the present invention.

[0037] Figure 5 The present invention provides a logic diagram for adapting to different capacitances to ground and their time constants.

[0038] Figure 6 It is a schematic diagram of the insulation resistance monitoring device of the energy storage system provided by the present invention.

[0039] Figure 7 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Combine the following Figure 1-Figure 7 The present invention describes a method, a device and an apparatus for monitoring the insulation resistance of an energy storage system.

[0042] In order to facilitate a clearer understanding of the technical solutions of the embodiments of the present application, some technical contents related to the embodiments of the present application are first introduced.

[0043] Locating insulation faults is of great significance for operation management, which can shorten the maintenance cycle and improve the utilization rate of the system. A large number of battery clusters and energy storage converters (Power Conversion System, PCS) are connected to the DC bus of large energy storage systems. The more common insulation monitoring methods for energy storage systems include balanced bridge principle, unbalanced bridge principle, DC injection method and AC injection method. The insulation monitoring system based on the bridge principle has a simple structure and low cost, and is suitable for cost-sensitive fields. The bridge principle cannot locate faults, and the measurement results are easily affected by the capacitance to the ground.

[0044] Injection monitoring applies a specific excitation to the earth, measures the response generated by the injected excitation at different locations in the system, and obtains the insulation resistance and fault branch by calculating and analyzing the response. The injection principle is divided into two modes: DC injection and AC injection.

[0045] DC injection uses a DC power supply as an excitation source to measure the DC response current of different branches. The DC injection method is not affected by the system's capacitance to ground. The principle is simple and reliable, the injection source is simple, and the distributed acquisition system does not require a dedicated synchronization signal, reducing wiring costs and workload. DC injection requires the use of a DC sensor to measure the response current. The cost of a DC sensor is relatively high. When the insulation resistance is large, the DC response current is very small, and the requirements for the DC transformer are further increased. The AD sampling system of DC injection needs to measure the DC quantity. The DC offset of the ADC chip and the operational amplifier chip has a greater impact on the measurement accuracy. The measurement accuracy of the monitoring system is easily affected by environmental factors such as temperature.

[0046] The AC injection method uses a sinusoidal signal of a specific frequency as the injection source to measure the sinusoidal response current of different branches. Since the response signal is a sinusoidal AC signal, an electromagnetic transformer can be used to measure the current. The electromagnetic transformer has the advantages of low cost, reliable performance, and mature products. The measurement of AC signals has a low dependence on the zero drift of the acquisition system, and the Fourier algorithm can remove the DC interference component. The AC injection method also has weaknesses relative to the DC injection method. The AC injection method needs to measure the phase of the current relative to the voltage, and obtain the resistive component in the current through the virtual and real part decomposition. The synchronization signal generally needs to be transmitted through a dedicated channel, such as a synchronous bus or wireless method. The introduction of the synchronization signal not only increases the system cost and complexity, but also reduces the reliability of the system. The collected data is only meaningful under the condition that the synchronization is completed, and the data in the out-of-step state cannot be used for insulation calculation.

[0047] Figure 1 This is one of the flow charts of the method for monitoring the insulation resistance of the energy storage system provided by the present invention, such as Figure 1 As shown, the method includes the following:

[0048] Step 101: Acquire current data in an energy storage system collected by a current transformer; and inject a bipolar square wave signal into a single DC bus of the energy storage system.

[0049] Specifically, the insulation monitoring of energy storage systems includes DC injection and AC injection. Among them, the DC injection method requires the use of a DC sensor to measure the response current. The DC sensor is relatively expensive. When the insulation resistance is large, the DC response current is very small, and the requirements for the DC transformer are further increased. The AC injection method requires measuring the phase of the current relative to the voltage, and obtaining the resistive component in the current by decomposing the virtual and real parts. The synchronization signal generally needs to be transmitted through a dedicated channel, such as a synchronous bus or wireless method. The introduction of the synchronization signal not only increases the system cost and complexity, but also reduces the reliability of the system.

[0050] In order to solve the above problems, in an embodiment of the present application, a bipolar square wave signal is injected into a single DC bus of the energy storage system, and the current data in the energy storage system collected by the current transformer is obtained. Optionally, a bipolar square wave signal is injected into a single DC bus of the energy storage system, that is, the positive and negative half-waves of the injected signal are symmetrical, and there is no DC component, so a through-type electromagnetic transformer can be used to collect current, avoiding the cost problem caused by the use of high-precision DC transformers. Optionally, a large number of battery clusters and PCSs are connected to the DC bus of a large energy storage system, and the current transformer can collect the ground current in the battery cluster and / or the ground current of the PCS. Furthermore, synchronous sampling of the distributed acquisition system can also be achieved with the help of the injected current step waveform, overcoming the disadvantage that the AC injection mode requires an independent sampling synchronization signal. That is, the embodiments of the present application take into account the advantages of both AC injection and DC injection methods. When a bipolar square wave signal is injected into a single DC bus of the energy storage system, the measured current is a sudden exponential decay current without a DC component. Therefore, an AC transformer can be used for measurement. Compared with the DC transformers based on the Hall principle and fluxgate principle used in the DC injection method, the system reliability can be effectively improved and the overall cost can be reduced. Compared with the AC injection method, current mutations can be used as synchronization signals, which saves dedicated synchronization channels, reduces costs and improves reliability.

[0051] Step 102: Determine the insulation resistance of the energy storage system according to the current data.

[0052] Specifically, after obtaining the current data in the energy storage system collected by the current transformer, such as obtaining the ground current in the battery cluster and / or the ground current of the PCS collected by the current transformer, the insulation resistance of the energy storage system can be determined by Ohm's theorem based on the voltage of the injected bipolar square wave signal and the current collected by the obtained transformer, thereby realizing efficient and accurate monitoring of the insulation resistance of the energy storage system. Compared with the monitoring method based on the bridge principle, the present application uses BCU as a distributed acquisition unit. The data acquisition unit divides the DC system into several sections through the current transformer, and can calculate the insulation resistance behind each section separately, thereby realizing fault location. In large-scale energy storage systems, the faults of each battery cluster and the PCS can be distinguished, which provides a technical basis for fault handling and improves the utilization rate of the energy storage system.

[0053] For example, Figure 2 In the architecture diagram of the insulation monitoring system shown, BCU is a distributed acquisition unit. Each BCU is equipped with a current transformer. The BCU collects data from the current transformer and sends the preliminary calculation results to the BAU (Battery Assembly Unit). The current transformer configured by the BCU (Battery Control Unit) is used to distinguish insulation faults of different battery clusters. BAU is a data aggregation and analysis control unit. The current transformer configured by BAU is used to distinguish insulation faults of energy storage systems and PCS systems. The injection power supply includes a controllable square wave generator, which adapts to different insulation resistances by switching different injection resistors r1. The injection power supply is connected to the DC positive bus. To avoid the risk of overcurrent, a high-voltage fuse is connected in series in the injection circuit. According to the circuit equivalent principle, after the injection resistor r1 is connected in parallel with the total insulation resistance, it works together with the total capacitance to ground to generate the time constant of the injection process. After BAU calculates the total insulation resistance, it adjusts the injected resistance r1 to be close to 1 / 10 of the total insulation resistance to ensure the accuracy of the algorithm. In order to effectively measure the decay process of the current, the period of the injected square wave can be equal to 14 times , BAU can dynamically adjust the cycle of the injection signal according to different capacitances to ground. Each battery cluster has capacitance to ground and insulation resistance on the positive bus and negative bus, respectively. Since the internal resistance of the battery pack is close to 0, it can be seen from the independent action principle of the circuit that each battery cluster can be equivalent to a total insulation resistance r2 and a total capacitance to ground C. Each BCU measures the current on r2 and C within the cluster, and the BAU measures the insulation resistance and the current on the capacitance to ground within the PCS. A large number of battery clusters and PCSs are connected to the DC bus of a large energy storage system, and the current transformer can collect the current to ground within the battery cluster and / or the current to ground of the PCS. That is, the present application can use BAU as a comprehensive analysis control unit and BCU as a distributed acquisition unit. Under the condition of optimizing only the injection source and the through-type current transformer, the distributed acquisition and insulation fault location functions are realized with the help of the BMS system architecture, which improves the insulation monitoring performance while effectively controlling the cost and complexity.

[0054] The method of the above embodiment, in the process of determining the insulation resistance of the energy storage system, injects a bipolar square wave signal into a single DC bus of the energy storage system, so that a through-type electromagnetic mutual inductor can be used to collect current, avoiding the cost problem caused by the use of high-precision DC mutual inductors. Moreover, synchronous sampling of the distributed acquisition system can also be achieved with the help of injected current step waveforms, overcoming the disadvantage that the AC injection mode requires an independent sampling synchronization signal. That is, the present application effectively takes into account the advantages of AC injection and DC injection methods by injecting a bipolar square wave signal into a single DC bus of the energy storage system and using an AC mutual inductor to measure the current data in the energy storage system, effectively controlling the cost and complexity while improving the insulation monitoring performance, and realizing efficient and accurate monitoring of the insulation resistance of the energy storage system.

[0055] In one embodiment, determining the insulation resistance of the energy storage system according to the current data includes:

[0056] According to the current data, determine the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system;

[0057] The insulation resistance of the energy storage system is determined based on the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave.

[0058] Specifically, in the embodiment of the present application, the current is sampled at continuous and equal intervals to determine the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system. Then, according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave and the voltage value of the injected bipolar square wave signal, the insulation resistance of the energy storage system is determined by Ohm's theorem, and efficient and accurate monitoring of the insulation resistance of the energy storage system can be achieved. It should be noted that in the embodiment of the present application, the insulation resistance of the energy storage system is determined based on the steady-state current, which improves the speed of insulation resistance calculation and enhances the adaptability to different ground capacitances. Moreover, the data sent by each distributed collector does not need to be aligned, and the conditions for averaging to improve accuracy are met, which can greatly improve the monitoring accuracy under the condition that time permits.

[0059] Optionally, determining the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system according to the current data includes:

[0060] The current steady-state value of the positive half-wave is determined as follows:

[0061] ;

[0062] in, Represents the steady-state value of the current in the positive half-wave; Represents the current data of the positive half wave collected at time a; Represents the current data of the positive half wave collected at time b; Indicates the current change rate corresponding to the positive half-wave;

[0063] The steady-state value of the current in the negative half-wave is determined as follows:

[0064] ;

[0065] in, Indicates the steady-state value of the current in the negative half-wave; Represents the current data of the negative half-wave collected at time a; Represents the current data of the negative half wave collected at time b; Indicates the current change rate corresponding to the negative half-wave.

[0066] Specifically, Figure 3 The voltage and current waveform diagram of the injection principle shown in FIG. Wherein, the injection power source is a voltage source, and the output waveform is a positive and negative symmetrical square wave with a period of T. Optionally, from time 0 to At this moment, the output is ;from Time has come At this moment, the output is , satisfying the following constraints:

[0067]

[0068]

[0069] At time 0, the output voltage jumps from 0 to At this time, the current of each current transformer jumps upward, and the peak value of the jump is Proportional to .

[0070] From 0 to At this moment, the current of each current transformer follows the same time constant Attenuation, the current satisfies the following formula:

[0071] (1)

[0072] in, is the steady-state value of the positive half-wave current, is the time constant of the injection process, and t is the time value.

[0073] exist At this moment, the output voltage jumps back to 0, and the current on each transformer jumps down. Time has come At this moment, the current gradually decays to 0. In order to measure the obvious decay process, it is advisable to , to ensure At this moment, the current has decayed to nearly 0, so Taking all factors into consideration, the period T of the injected signal can be 14 .

[0074] The negative half-wave output is similar to the positive half-wave, and the current satisfies the following formula:

[0075] (2)

[0076] in, is the steady-state value of the negative half-wave current. Due to the zero drift of the acquisition system, it does not meet and .

[0077] The injection process is divided into 4 sections: Section 1 is the positive half-wave current decay section, Section 2 is the positive voltage discharge section of the ground capacitor, Section 3 is the negative half-wave current decay section, and Section 4 is the negative voltage discharge section of the ground capacitor. As can be seen from the figure, the second of two consecutive positive current jumps is the starting time of Section 1, and the second of two consecutive negative current jumps is the starting time of Section 3. Each distributed acquisition unit can determine the starting time of Section 1 and Section 3 according to the current jump time, thereby achieving sampling synchronization.

[0078] For example, Figure 4The following is an analysis diagram of the sampling and calculation principle of the current waveform. The steady-state output of each current transformer can be obtained by sampling and calculating the 1st and 3rd segments. Optionally, to simplify the description of the algorithm principle, the current waveforms of the 1st and 3rd segments are plotted in an independent coordinate system, and the moment of the current mutation is taken as the coordinate zero moment.

[0079] Sampling starts at the time Δt after the current mutation. The value of Δt is mainly considered to avoid the spurious transition process of the current mutation, ensuring that the current at the sampling time satisfies Formula 1 or Formula 2. Possible causes of the spurious process include parasitic inductance of the loop, non-ideal jump of the voltage output waveform, etc. The Δt value of each distributed acquisition terminal can be different.

[0080] At consecutive equal intervals , , , The current is sampled at all times, and the sampling time satisfies:

[0081] (3)

[0082] From formula 1, we can know The expression of the current at this moment is:

[0083] (4)

[0084] use Current minus The current at this moment can be obtained:

[0085] (5)

[0086] Extracting the common factor of the exponential decay part in Formula 4 yields:

[0087] (6)

[0088] Subtract the current at Tb from the current at Tc and divide by Formula 5 to get:

[0089] (7)

[0090] To simplify the explanation, the above result is The above formula shows that under the condition of equal interval sampling, the ratio of the current amplitude difference is only related to the time constant of the system. Substituting formula 7 into formula 6 and combining it with formula 4, we can get:

[0091] (8)

[0092] The sampling interval of the negative half-wave is also ΔT. Similarly, the following relationship can be obtained, where: May not be equal to :

[0093] (9)

[0094] The method of the above embodiment uses the difference between positive and negative half-wave currents to obtain the steady-state value of the response current, eliminating the influence of the zero drift of the acquisition system on the DC algorithm, reducing the requirements for the ADC chip and the operational amplifier chip, and especially solving the influence of temperature on the acquisition accuracy, thereby improving the measurement accuracy and stability of the large-resistance insulation resistance. The present application solves the influence of zero drift on the measurement accuracy in the ordinary DC injection mode, eliminates the influence of zero drift by calculating the difference between the positive and negative sampling values, possesses the advantages of the AC injection method, and realizes efficient and accurate monitoring of the insulation resistance of the energy storage system.

[0095] Optionally, determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave includes:

[0096] Determine the insulation resistance of the energy storage system as follows:

[0097] ;

[0098] in, Indicates the insulation resistance of the energy storage system; Indicates the voltage value corresponding to the positive half-wave; Indicates the voltage value corresponding to the negative half-wave; Represents the steady-state value of the current in the positive half-wave; Indicates the steady-state value of the current in the negative half-wave.

[0099] Specifically, after determining the steady-state current values ​​of the positive and negative half-waves, the grounding resistance can be calculated according to Ohm's law:

[0100] (10)

[0101] The grounding resistance calculated by the above formula is the result of the combined effect of the injection resistance r1 and the insulation resistance r2 within the cluster. When the value of r1 is close to 1 / 10 of the total insulation resistance, the grounding resistance calculated within the cluster is mainly determined by r2, and the calculation accuracy of formula 10 is acceptable.

[0102] Through simple analysis, we can know that the average current value between Ia+ and Ib+ is used to replace Ia+, the average current value between Ib+ and Ic+ is used to replace Ib+, and so on. Formula 10 still holds true, which shows that the average value filtering can improve the anti-interference ability of each monitoring point, so that the DC algorithm has the advantages of the AC algorithm. After the attenuated current waveform is segmented and integrated or filtered, the algorithm has an anti-interference performance similar to that of the Fourier filter, and the insulation monitoring results are stable and reliable. Further promotion, not only the average value filtering is suitable for anti-interference, but other FIR filtering methods can also be used to improve accuracy, which further improves the performance of the system. It can be seen from Formula 10 that both voltage and current are reflected in the formula as the difference between two measured values, so the measurement zero drift of the system is eliminated, and the accuracy of the algorithm is greatly improved compared with the traditional DC injection method. For the insulation resistance of the PCS, the calculation principle is the same as the insulation resistance of each cluster. Since the system can calculate the insulation resistance of different parts separately, the insulation fault is located.

[0103] The method of the above embodiment eliminates the influence of hardware measurement zero drift on measurement accuracy by interpolating the positive and negative half-wave currents. The measurement speed is improved by calculating the steady-state value of the exponential curve. The synchronization of distributed acquisition is achieved by using current mutations without the need for a dedicated synchronization signal. The DC algorithm does not require alignment of distributed calculation results, and the system has good stability. The system measurement accuracy can be improved by long delays. Using a positive and negative symmetrical excitation source, the current transformer is low in cost, and the system cost is better than the DC injection method.

[0104] Optionally, after determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave, the method further includes:

[0105] When the insulation resistance of the energy storage system is less than a preset value, the injection source device is instructed to perform a target operation; the target operation includes shortening the period of the bipolar square wave signal and / or reducing the injection resistance.

[0106] Specifically, this application is based on sampling of the current transition process. When the system time constant is large, the current has no obvious attenuation, and the numerator and denominator of Formula 8 and Formula 9 are close to 0, and the calculation accuracy cannot be guaranteed. In the embodiment of this application, by increasing the injection signal period and the sampling interval ΔT, a significant current attenuation can be obtained, thereby improving the calculation accuracy. That is, the resistance calculated by Formula 10 is the result of the combined effect of the injection resistance r1 and the insulation resistance r2 within the cluster. When r1 is too small, the system time constant is When r1 is too large, r1 will have a greater impact on the calculation result of formula 10, which is not conducive to the calculation and evaluation of r2. The value of r1 needs to be corrected in real time with the insulation resistance to ground in the system. Different injection resistance r1 can be achieved through the switching combination of the switch. Figure 5 As shown in the figure, when the energy storage system is just put into operation, the insulation resistance to the ground is generally large. After the BAU calculates the insulation resistance of each cluster, it adjusts the injection resistance and the length of the injection cycle according to the calculation results to ensure that the calculation results are highly accurate. That is, for different insulation resistances and capacitances to the ground, the time constant of the response current decay is different. By adjusting the cycle and duty cycle of the injection signal, it can adapt to the combination of different insulation resistances and capacitances to the ground, and improve the measurement accuracy of the system.

[0107] The method of the above embodiment can adapt to different combinations of insulation resistance and ground capacitance by adjusting the period of the injection signal and the injection resistance, thereby improving the measurement accuracy of the system.

[0108] Exemplarily, a method for monitoring the insulation resistance of an energy storage system is provided in an embodiment of the present application, and the specific process is as follows:

[0109] 1. Connect the DC injection source between the positive bus and the ground to inject a symmetrical square wave voltage into the energy storage system. The injection resistance and injection cycle are controlled by the BAU.

[0110] 2. The positive and negative busbars in the cluster pass through the current transformer, and the BCU is used to measure the ground current in the cluster and send it to the BAU to monitor the insulation status of the cluster.

[0111] 3. Pass the current transformer through the positive and negative busbars of the PCS, and use BAU to measure the PCS ground current to monitor the insulation status of the PCS.

[0112] 4. BAU collects all voltage and current sampling data, calculates the insulation resistance of each cluster or PCS through formula 10, and dynamically adjusts the injection resistance and injection cycle length according to the calculation results to ensure the optimal monitoring accuracy.

[0113] The method of the embodiment of the present application measures the capacitance to ground and insulation resistance of each battery cluster by injecting a bipolar square wave into a single DC bus, which can achieve measurement and fault location under different insulation resistance and capacitance to ground conditions, and distinguish the insulation fault of each battery cluster or PCS. The present application itself is based on the DC principle, and has low requirements for synchronization accuracy, and the calculation results of the distributed acquisition units do not need to be aligned, and the accuracy can be improved through long-delay measurement. The method of the embodiment of the present application combines the advantages of DC injection and AC injection. Compared with other injection principles, it has the advantages of small influence of zero drift on accuracy, fast calculation speed, no need for separate synchronous acquisition signals, no need to align acquisition results, long-delay measurement to improve accuracy, and low cost of mutual inductors.

[0114] The following is a description of the insulation resistance monitoring device of the energy storage system provided by the present invention. The insulation resistance monitoring device of the energy storage system described below and the insulation resistance monitoring method of the energy storage system described above can be referred to each other. Figure 6 As shown, including:

[0115] The acquisition module 610 is used to acquire the current data in the energy storage system collected by the current transformer; inject a bipolar square wave signal into a single DC bus of the energy storage system;

[0116] The monitoring module 620 is used to determine the insulation resistance of the energy storage system according to the current data.

[0117] Optionally, the monitoring module 620 is specifically used for:

[0118] According to the current data, determine the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system;

[0119] The insulation resistance of the energy storage system is determined based on the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave.

[0120] Optionally, the monitoring module 620 is specifically used for:

[0121] The current steady-state value of the positive half-wave is determined as follows:

[0122] ;

[0123] in, Represents the steady-state value of the current in the positive half-wave; Represents the current data of the positive half wave collected at time a; Represents the current data of the positive half wave collected at time b; Indicates the current change rate corresponding to the positive half-wave;

[0124] The steady-state value of the current in the negative half-wave is determined as follows:

[0125] ;

[0126] in, Indicates the steady-state value of the current in the negative half-wave; Represents the current data of the negative half-wave collected at time a; Represents the current data of the negative half wave collected at time b; Indicates the current change rate corresponding to the negative half-wave.

[0127] Optionally, the monitoring module 620 is specifically used for:

[0128] Determine the insulation resistance of the energy storage system as follows:

[0129] ;

[0130] in, Indicates the insulation resistance of the energy storage system; Indicates the voltage value corresponding to the positive half-wave; Indicates the voltage value corresponding to the negative half-wave; Represents the steady-state value of the current in the positive half-wave; Indicates the steady-state value of the current in the negative half-wave.

[0131] Optionally, the monitoring module 620 is further configured to:

[0132] When the insulation resistance of the energy storage system is less than a preset value, the injection source device is instructed to perform a target operation; the target operation includes shortening the period of the bipolar square wave signal and / or reducing the injection resistance.

[0133] Figure 7 An example of a physical structure diagram of an electronic device is provided, and the electronic device may include: a processor 710, a communication interface 720, a memory 730, and a communication bus 740, wherein the processor 710, the communication interface 720, and the memory 730 communicate with each other through the communication bus 740. The processor 710 may call the logic instructions in the memory 730 to execute a method for monitoring the insulation resistance of an energy storage system, and the method includes: obtaining current data in the energy storage system collected by a current transformer; injecting a bipolar square wave signal into a single DC bus of the energy storage system; and determining the insulation resistance of the energy storage system according to the current data.

[0134] In addition, the logic instructions in the above-mentioned memory 730 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0135] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the insulation resistance monitoring method of the energy storage system provided by the above methods. The method includes: obtaining current data in the energy storage system collected by a current transformer; injecting a bipolar square wave signal into a single DC bus of the energy storage system; and determining the insulation resistance of the energy storage system based on the current data.

[0136] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for monitoring the insulation resistance of the energy storage system provided by the above methods is implemented. The method includes: obtaining current data in the energy storage system collected by a current transformer; injecting a bipolar square wave signal into a single DC bus of the energy storage system; and determining the insulation resistance of the energy storage system based on the current data.

[0137] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0138] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for monitoring insulation resistance of an energy storage system, characterized in that: include: Obtaining current data in the energy storage system collected by a current transformer; A bipolar square wave signal is injected into a single DC bus of the energy storage system; determining the insulation resistance of the energy storage system according to the current data; Determining the insulation resistance of the energy storage system according to the current data includes: Determine, according to the current data, a current steady-state value of a positive half-wave and a current steady-state value of a negative half-wave corresponding to the energy storage system; Determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave; Determining the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system according to the current data includes: The current steady-state value of the positive half-wave is determined based on the following method: ； in, Represents the steady-state value of the current in the positive half-wave; Represents the current data of the positive half wave collected at time a; Represents the positive half-wave current data collected at time b; Indicates the current change rate corresponding to the positive half-wave; The current steady-state value of the negative half-wave is determined based on the following method: ； in, Indicates the steady-state value of the current in the negative half-wave; Represents the current data of the negative half-wave collected at time a; Represents the current data of the negative half wave collected at time b; Indicates the current change rate corresponding to the negative half-wave.

2. The method for monitoring the insulation resistance of an energy storage system according to claim 1, characterized in that: Determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave includes: The insulation resistance of the energy storage system is determined as follows: ； in, Indicates the insulation resistance of the energy storage system; Indicates the voltage value corresponding to the positive half-wave; Indicates the voltage value corresponding to the negative half-wave; Represents the steady-state value of the current in the positive half-wave; Indicates the steady-state value of the current in the negative half-wave.

3. The method for monitoring the insulation resistance of an energy storage system according to claim 1, characterized in that: After determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave, the method further includes: When the insulation resistance of the energy storage system is less than a preset value, the injection source device is instructed to perform a target operation; the target operation includes shortening the period of the bipolar square wave signal and / or reducing the injection resistance.

4. The method for monitoring insulation resistance of an energy storage system according to claim 1, characterized in that: The current collected by the current transformer is the current in the battery cluster in the energy storage system or the current of the energy storage converter PCS.

5. A monitoring device for insulation resistance of an energy storage system, characterized in that: include: An acquisition module, used to acquire current data in the energy storage system collected by a current transformer; A bipolar square wave signal is injected into a single DC bus of the energy storage system; A monitoring module is used to determine the insulation resistance of the energy storage system according to the current data; the determining the insulation resistance of the energy storage system according to the current data includes: Determine, according to the current data, a current steady-state value of a positive half-wave and a current steady-state value of a negative half-wave corresponding to the energy storage system; Determining the insulation resistance of the energy storage system according to the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave; Determining the current steady-state value of the positive half-wave and the current steady-state value of the negative half-wave corresponding to the energy storage system according to the current data includes: The current steady-state value of the positive half-wave is determined based on the following method: ； in, Represents the steady-state value of the current in the positive half-wave; Represents the current data of the positive half wave collected at time a; Represents the positive half-wave current data collected at time b; Indicates the current change rate corresponding to the positive half-wave; The current steady-state value of the negative half-wave is determined based on the following method: ； in, Indicates the steady-state value of the current in the negative half-wave; Represents the current data of the negative half-wave collected at time a; Represents the current data of the negative half wave collected at time b; Indicates the current change rate corresponding to the negative half-wave.

6. An electronic device 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, the method for monitoring the insulation resistance of the energy storage system according to any one of claims 1 to 4 is implemented.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for monitoring the insulation resistance of the energy storage system according to any one of claims 1 to 4 is implemented.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method for monitoring the insulation resistance of the energy storage system according to any one of claims 1 to 4 is implemented.

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