A stimulus current generating circuit and control method for battery impedance spectroscopy measurement

Abstract

The application discloses an excitation current generating circuit and a control method for battery impedance spectrum measurement, and belongs to the field of battery impedance spectrum detection. The excitation current generating circuit generates an excitation current with a set frequency and amplitude on the connected battery system to perform battery impedance spectrum measurement. The excitation current generating circuit is connected in parallel with the battery system, an energy storage converter or a load. A mathematical model, an equivalent circuit model and a control method of the excitation current generating circuit are provided. Through closed-loop control of the port current of the excitation current generating circuit and the DC side capacitor voltage, the excitation current with controllable frequency and amplitude is generated by periodic energy exchange with the battery system. Compared with the prior art, the excitation current generating circuit provided by the application does not need to make any adjustment to the existing equipment in the energy storage system, adopts a battery system self-energy supply mode, and generates an excitation current for impedance spectrum measurement under low power consumption.

Description

An excitation current generation circuit and control method for battery impedance spectrum measurement Technical Field

[0001] This invention belongs to the field of battery impedance spectroscopy, and more specifically, relates to an excitation current generation circuit and control method for battery impedance spectroscopy measurement. Background Technology

[0002] In recent years, frequent safety incidents involving energy storage battery systems caused by malfunctions such as thermal runaway have posed significant safety risks to the application of energy storage systems. To ensure the safe and stable operation of energy storage systems, it is necessary to monitor the battery's operating status and provide early warning of potential faults.

[0003] Battery Management Systems (BMS) play a crucial role in ensuring the safe and stable operation of batteries, enabling real-time monitoring and control of the operating status of each energy storage battery. The real-time monitoring parameters of the battery system by the BMS mainly include battery terminal voltage, battery current, surface temperature, and estimated state of charge (SOC). However, in most current applications, BMS only monitors external battery information such as voltage and current, failing to obtain internal battery characteristic parameters, especially impedance characteristics, and thus cannot identify potential battery defects. This leads to ongoing battery failures and safety incidents.

[0004] Electrochemical impedance spectroscopy (EIS) is a non-destructive method for parameter determination and effective measurement of battery kinetics. By applying AC excitation currents of different frequencies to a battery system, a corresponding AC voltage response is generated at the terminal voltage of each cell. The calculated impedance of the excitation current and response voltage at different frequencies constitutes the battery's impedance spectrum. EIS has wide applications in the analysis of positive and negative electrode materials, the study of ion insertion / extraction kinetics, solid electrolytes, interfacial reactions, SOC prediction, and internal temperature estimation. It can describe and fit the internal parameter characteristics of the battery, thereby regulating the operating mode of the battery management system to further ensure the safe and stable operation of the battery system and prevent malfunctions.

[0005] In laboratory research and analysis, dedicated impedance measurement equipment such as electrochemical workstations can be used to collect impedance spectrum data of batteries across the entire frequency range. However, in actual engineering environments, such equipment is not suitable, necessitating the design of excitation current sources and impedance spectrum detection equipment tailored to specific engineering conditions.

[0006] Existing excitation current sources designed for measuring battery impedance spectra in engineering scenarios are mostly modified designs based on specific energy storage converter circuits and control structures. This increases development time and cost, and cannot be compatible with various energy storage converter models and energy storage system structures in different engineering scenarios, making widespread use inconvenient. Furthermore, some existing excitation current source designs can only operate under specific conditions such as battery charging, lacking versatility, or they use external input energy to generate the excitation current, increasing system complexity. Summary of the Invention

[0007] To address the shortcomings and improvement needs of existing technologies, this invention provides an excitation current generation circuit and control method for battery impedance spectrum measurement. It aims to solve the technical problem that the excitation current source for impedance spectrum measurement lacks versatility and can only generate excitation current by modifying the original equipment of the battery system or using external input energy.

[0008] To achieve the above objectives, according to a first aspect of the present invention, an excitation current generating circuit for battery impedance spectrum measurement is provided, comprising: a voltage sensor, and a DC-side capacitor C. d The full-bridge circuit consists of switching transistors Q1, Q2, Q3, and Q4, their anti-parallel diodes, current sensor b, filter inductor L1, filter inductor L2, and filter capacitor C. A Current sensor a, switches K1 and K2 forming the pre-charge circuit, and current-limiting resistor R y Switch K0;

[0009] The excitation current generating circuit is connected in parallel to the battery system via switch K0; wherein, the DC side capacitor C d The following components are connected in sequence: a full-bridge circuit, current sensor b, filter inductor L1, filter inductor L2, current sensor a, and pre-charge circuit. The other end of the pre-charge circuit is connected to the positive DC bus of the battery system via K0. Switches Q1 and Q3 are connected in series, and switches Q2 and Q4 are connected in series. One end of current sensor b is connected to filter inductor L1, and the other end is connected to the node between Q1 and Q3. Filter capacitor C... A One end is connected to the node between L1 and L2, and the other end is connected to the node between Q2 and Q4. The node between Q2 and Q4 is connected to the negative terminal of the DC bus of the battery system through K0; the voltage sensor is connected in parallel to the DC-side capacitor C. d Both ends;

[0010] The voltage sensor is used to sample the DC-side capacitance C. d Voltage U across the terminals dc Current sensor a is used to sample the current i at the port of the excitation current generation circuit. dis Current sensor b is used to sample the output current i of the full-bridge circuit. oExcitation current generating circuit port current i dis The positive direction is defined as the flow from the battery system to the excitation current generating circuit, i o The positive direction is defined as the current flowing from current sensor b to the full-bridge circuit.

[0011] Furthermore, the mathematical model of the excitation current generating circuit is as follows:

[0012] i ref (s) minus i C (s) Subtract the feedback quantity H dis i dis The error signal after (s) is input to the current regulator G. i (s) Perform conditioning calculations, current regulator G i The opposite of the output quantity of (s) minus the feedback quantity H CA i CA The error signal input after (s) characterizes the delay G of the digital control system. d (s) stage, G d (s) Output of the stage, input to the single-pole frequency multiplication SPWM modulation stage K SPWM K SPWM The opposite of the output of the component plus Z CA After the feedback quantity of the output quantity of the (s) stage, input 1 / Z L1 (s) stage, 1 / Z L1 The opposite of the output of the (s) stage plus i dis i is obtained after the feedback quantity of (s). CA (s), i CA (s) Input Z CA (s) stage, Z CA The opposite of the output of the (s) stage plus U b (s) followed by 1 / Z L2 (s) stage, 1 / Z L2 The output of the (s) stage is the port current i of the excitation current generating circuit. dis (s);

[0013] Among them, i ref (s) is the AC reference signal for the excitation current, i C (s) characterize i dis The energy exchange current in (s) excluding the AC excitation current component, H dis For i dis The sampling feedback coefficients of (s), i CA (s) represents the filter capacitor current, derived from i dis (s) sampled signal minus i o The sampled signal (s) is obtained, H CA For i CAThe sampling feedback coefficients of (s), K SPWM Z is the transfer function of the SPWM modulator. L1 (s), Z L2 (s), Z CA (s) represent the filter inductor L1, filter inductor L2, and filter capacitor C, respectively. A The impedance, U b (s) is the DC bus voltage connected after the excitation current generating circuit is turned on by the battery system.

[0014] Furthermore, the simplified mathematical model of the excitation current generating circuit is as follows:

[0015] i ref (s) minus i C (s) Subtract the feedback quantity H dis i dis The error signal after (s) is input to G. x1 (s) stage, G x1 The output of the (s) stage plus U b (s) followed by G x2 (s) stage, G x2 The output of the (s) stage is the port current i of the excitation current generating circuit. dis (s);

[0016] Among them, G x1 (s) and G x2 The expression for (s) is:

[0017]

[0018]

[0019] Furthermore, the port current i of the excitation current generating circuit dis (s) is represented as:

[0020]

[0021] in:

[0022]

[0023]

[0024]

[0025] T(s) = G x1 (s)Gx2 (s)H dis .

[0026] To achieve the above objectives, according to a second aspect of the present invention, a control method for an excitation current generating circuit as described in the first aspect is provided, comprising the following steps:

[0027] In the initial stage of operation of the excitation current generating circuit, K0 and K2 in the pre-charge circuit are closed first, while K1 is opened. At this time, the battery system supplies power to the DC-side capacitor C through the anti-parallel diode in the full-bridge circuit. d Charge;

[0028] At the instant the excitation current generating circuit is initially connected to the battery system, the DC side capacitor C d The two ends are equivalent to a short circuit, and the current-limiting resistor R in the pre-charge circuit y It serves to limit current and prevent C d Excessive initial charging current can burn out the battery or switching devices.

[0029] DC side capacitor voltage U dc Once the set reference value is reached, K1 is closed and K2 is opened, and the excitation current generating circuit enters a stable working state, generating the set excitation current.

[0030] Furthermore, during the process of generating the excitation current, the excitation current generating circuit, in order to ensure that the DC side capacitor voltage U... dc Stable, U is adjusted through the DC voltage outer loop. dc The specific implementation method is as follows:

[0031] Set the DC-side capacitor voltage reference value U ref Subtract the DC side capacitor voltage sampling signal U dc The error signal is sent to the voltage regulator G. v (s), G v The output of (s) is used as i dis The reference signal i of the energy exchange current excluding the AC excitation current component in (s) C ;

[0032] Excitation current AC reference signal i ref Subtract i C Subtract the feedback quantity H dis i dis The error signal is then input to G. i (s) stage, G i The opposite of the output of the (s) stage minus H CA i CA The modulated wave signal v is then obtained. MA v MA The drive signals for switching transistors Q1 to Q4 are obtained by unipolar frequency doubling SPWM modulation.

[0033] Furthermore, after the excitation current generating circuit enters the steady-state operating mode, the control parameters are modified according to the impedance spectrum measurement requirements to ensure that the excitation current generating circuit stably generates an excitation current with the set frequency and amplitude on the battery system; wherein, the control parameters include the DC-side capacitor voltage reference value U. ref and excitation current AC reference signal i ref .

[0034] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0035] This invention involves a parallel excitation current generating circuit bypassing the battery system. Through closed-loop control of the excitation current generating circuit port current and the DC-side capacitor voltage, a frequency- and amplitude-controllable excitation current is generated by the periodic energy exchange between the DC-side capacitor and the battery system. Compared to existing technologies, the excitation current generating circuit proposed in this invention requires no adjustments to existing equipment in the energy storage system, utilizes the battery system's self-powered operation, and generates an excitation current for impedance spectral measurement with low power consumption. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the circuit connection structure between the excitation current generating circuit and the energy storage system in this invention.

[0037] Figure 2 is a mathematical model of the excitation current generating circuit in this invention.

[0038] Figure 3 is a simplified mathematical model of the excitation current generating circuit in this invention.

[0039] Figure 4 is the equivalent circuit model of the excitation current generating circuit in this invention.

[0040] Figure 5 is a control block diagram of the excitation current generating circuit in this invention.

[0041] Figure 6 is a flowchart of the excitation current generating circuit in this invention.

[0042] Figure 7 is a waveform diagram showing the frequency amplitude variation of the excitation current generated by the excitation current generating circuit on the battery system in a specific embodiment of the present invention.

[0043] Figure 8 is a waveform diagram of the excitation current and active power generated by the excitation current generating circuit on the battery system in a specific embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0045] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0046] As shown in Figure 1, this invention generates an AC excitation current with controllable frequency and amplitude on the battery system by bypassing and paralleling the excitation current generation circuit. This, in turn, generates an excitation current in each individual cell within the battery system, which can be used to measure the battery impedance spectrum. The excitation current generation circuit is connected in parallel with the battery system, energy storage converter, or other loads, facilitating modular design and good engineering versatility. The excitation current generation circuit consists of two parts: a circuit topology and a software control method. By controlling the periodic energy exchange between the DC-side capacitor of the excitation current generation circuit and the battery system, the excitation current is generated using the battery system's own energy, achieving a self-powered, low-power excitation current effect.

[0047] The topology of the excitation current generating circuit and its connection structure with the battery system are shown in Figure 1, including: a voltage sensor, and a DC-side capacitor C. d The full-bridge circuit consists of switching transistors Q1, Q2, Q3, and Q4, their anti-parallel diodes, current sensor b, filter inductor L1, filter inductor L2, and filter capacitor C. A Current sensor a, switches K1 and K2 forming the pre-charge circuit, and current-limiting resistor R y Switch K0. The excitation current generating circuit, battery system, energy storage converter, or other loads are connected in parallel to the DC bus of the energy storage system via the switch. The DC-side capacitor, full-bridge circuit, current sensor b, filter inductor L1, filter inductor L2, current sensor a, and pre-charge circuit are connected in sequence, with filter capacitor C. A One end is connected to the node between L1 and L2, and the other end is connected to the node between Q2 and Q4. The voltage sensor is connected in parallel to the DC-side capacitor C. d Both ends. DC side capacitor voltage U dc The current i at the port of the excitation current generation circuit is sampled by a voltage sensor. dis The full-bridge circuit output current i o Sampled via a current sensor. Current i at the port of the excitation current generation circuit. dis The positive direction is defined as the flow from the battery system to the excitation current generating circuit.

[0048] In the initial stage of operation of the excitation current generating circuit, K0 and K2 in the pre-charge circuit are closed first, while K1 is opened. At this time, the battery system supplies power to the DC-side capacitor C through the anti-parallel diode in the full-bridge circuit. d Charging. At the initial connection between the excitation current generating circuit and the battery system, the DC-side capacitor C... d The two ends are equivalent to a short circuit, and the current-limiting resistor R in the pre-charge circuit y This serves to limit the flow and prevent C d Excessive initial charging current can burn out the battery or switching devices. Wait for the DC side capacitor voltage U... dc Once the set reference value is approached, K1 is closed and K2 is opened, and the excitation current generating circuit enters a stable working state, generating the set excitation current.

[0049] Next, a mathematical model of the excitation current generating circuit is constructed based on the designed circuit structure.

[0050] The excitation current generating circuit generates an excitation current in the battery system by implementing closed-loop control of its port current. Therefore, it is necessary to analyze the port impedance characteristics of the excitation current generating circuit and the expression for the excitation current, and to study how to rationally design a controller to ensure that the excitation current generating circuit accurately generates an excitation current with controllable frequency and amplitude in the battery system within the frequency range required for measuring the battery impedance spectrum, while simultaneously reducing the power loss of the excitation current generating circuit. To this end, a mathematical model of the excitation current generating circuit is constructed.

[0051] Figure 2 shows the mathematical model of the excitation current generating circuit. Where, i dis (s) is the port current of the excitation current generating circuit, H dis is i dis The sampling feedback coefficients of (s), G i (s) is the current regulator, i CA (s) is the filter capacitor current, H CA is i CA The sampling feedback coefficients of (s), i CA The sampled signal of (s) is i dis (s) sampled signal minus i o The sampled signal (s) is obtained. U b (s) is the DC bus voltage connected after the excitation current generating circuit is turned on by the battery system, G d (s) is the delay introduced by digital control, K SPWM It is the transfer function of the SPWM modulator, Z L1 (s) = sL1 is the impedance of L1, Z L2 (s) = sL2 is the impedance of L2, Z CA (s)=1 / (sC A ) is CA The impedance.

[0052] i ref (s) is the set AC reference signal for the excitation current, containing the frequency and amplitude information of the AC excitation current required for measuring the battery impedance spectrum, and is calculated as a positive correlation quantity in the mathematical model. Considering that the energy generated by the excitation current generation circuit and the energy lost both originate from the battery system, the DC-side capacitor of the excitation current generation circuit needs to absorb and store energy in the initial stage, and then generate the excitation current through periodic energy exchange with the battery system via the DC-side capacitor. Therefore, i is used. C (s) characterize i dis In (s), the energy exchange current, excluding the AC excitation current component, is calculated as a negative correlation quantity in the mathematical model. C (s), i ref (s) and i dis (s) After comparing the feedback quantity, the input current regulator G i (s) performs conditioning calculations. Then, a filter capacitor current feedback damping method is adopted, and the current regulator G... i (s) Output quantity and i CA (s) The feedback quantity is compared, and then passed through G, which characterizes the delay of the digital control system. d (s) stage, the obtained modulation signal is input to the single-pole frequency multiplication SPWM modulation stage K SPWM Finally, based on the filter circuit topology, K is completed. SPWM The subsequent construction of the circuit yields the port current i of the excitation current generation circuit. dis (s).

[0053] Figure 3 shows a simplified mathematical model of the excitation current generating circuit. The design of multiple control loops in the aforementioned mathematical model of the excitation current generating circuit is quite complex. Therefore, a simplified mathematical model equivalent to the aforementioned mathematical model of the excitation current generating circuit is obtained through equivalent transformation, wherein:

[0054]

[0055]

[0056] Based on the simplified mathematical model, the loop gain of the current loop in the excitation current generating circuit can be obtained as follows:

[0057]

[0058] Based on the simplified mathematical model, the port current i of the excitation current generating circuit can be written. dis The expression for (s), idis The positive direction of (s) is defined as the flow from the battery system to the excitation current generating circuit:

[0059]

[0060] in:

[0061]

[0062]

[0063]

[0064] i dis In the expression of (s), G x3 (s)i ref (s) is the AC component of the excitation current required for measuring the battery impedance spectrum, G x4 (s)i C (s) is the DC-side capacitor C for establishing the excitation current generating circuit. d The feedback current component for dynamic energy balance between the battery system, Z p (s) represents the equivalent impedance characterizing the power loss of the excitation current generating circuit, U b (s) / Z p (s) characterize i dis The current component in (s) is used to compensate for the power loss of the excitation current generating circuit.

[0065] Based on the port current i of the excitation current generating circuit dis The expression for (s) allows us to draw the equivalent circuit diagram of the excitation current generating circuit, as shown in Figure 4. Here, the equivalent AC excitation current source G... x3 (s)i ref (s) Generates the AC excitation current required for impedance spectrum measurement, equivalent energy feedback current source G x4 (s)i C (s) is used to feed the energy absorbed by the DC-side capacitor back to the battery system, establish dynamic energy balance, and maintain stable DC-side capacitor voltage. The equivalent energy loss impedance Z of the excitation current generation circuit. p (s) is used to characterize the energy loss generated by the excitation current generating circuit during operation.

[0066] Under steady-state operation, the DC-side capacitor of the excitation current generating circuit absorbs energy from the battery system for a portion of the AC excitation current cycle, and releases capacitive energy back to the battery for the other portion of the cycle. Energy is continuously exchanged between the battery system and the DC-side capacitor. Port current i disOnly a small current component in (s) is used to compensate for energy losses caused by stray resistance heating in the excitation current generating circuit, device heating, and internal resistance heating of the battery system itself. Therefore, the overall power loss of the excitation current generating circuit can be controlled at a low level.

[0067] The control block diagram of the excitation current generating circuit is shown in Figure 5. This corresponds to the equivalent AC excitation current source G in the aforementioned equivalent circuit model. x3 (s)i ref (s), Equivalent energy feedback current source G x4 (s)i C (s) When designing the controller, it is necessary to consider the AC component of the excitation current and the DC-side capacitor C. d The energy feedback current component is used for control. The AC component of the excitation current is controlled by the excitation current reference signal i. ref Together with the excitation current sampling feedback signal, they form feedback control, i ref The amplitude and frequency are given by a host computer or remote control, and can be calculated and updated in real time according to the real-time operating conditions of the battery system and the impedance spectrum detection requirements. DC side capacitor C d The energy feedback current component is controlled through a feedback loop of the DC-side capacitor voltage. The aforementioned mathematical model requires the DC bus voltage U of the battery system connected to the excitation current generating circuit. b (s), but this detection quantity is not required when designing the controller, DC bus voltage U b (s) Only for energy loss and DC side capacitor voltage reference value U ref The value of has an impact.

[0068] The excitation current generating circuit absorbs energy from the battery during the generation of the excitation current. Part of this energy is used to compensate for power losses, and another part is used to power the DC-side capacitor C in the initial stage. d Charging, and under normal operating conditions, as the energy exchanged between the DC-side capacitor and the battery, will cause the DC-side capacitor voltage U to... dc Rise. To make U dc Stability requires adjustment of U via the DC voltage outer loop. dc The excess energy is converted into port current i dis The current component is fed back to the battery to establish a dynamic balance. The specific implementation method is as follows: U... dc The sampling feedback signal and the set DC-side capacitor voltage reference value U ref The comparison is performed, and the error value is sent to the voltage regulator G. v (s), G v The output of (s) serves as the reference value i for the energy feedback component of the excitation current generator circuit port current. C .

[0069] Excitation current i dis The sampling feedback signal and the set excitation current reference signal i ref and i C Comparison, i ref Includes the excitation current frequency and amplitude information required for measuring the battery impedance spectrum, H dis For i dis The sampling feedback coefficients are used. The resulting error signal is then fed into the current regulator G. i (s). Using a filter capacitor current feedback active damping method, H CA For i CA The sampling feedback coefficient, the filter capacitor current i CA From the sampled signal i dis Subtract the sampled signal i o Received. G i The output of (s) is inverted and then subtracted from the current feedback signal of the filter capacitor to obtain the modulated wave signal v. MA Finally, the drive signals for the switching transistors Q1 to Q4 are obtained through single-pole frequency doubling SPWM modulation.

[0070] The excitation current generating circuit is connected in parallel with the battery system at the DC bus, and can be turned on at any time to provide excitation current for battery impedance spectrum testing. The control parameters can be updated and adjusted according to different battery system specifications or operating conditions to generate an excitation current that matches the actual operating conditions, thus having good engineering versatility.

[0071] Figure 6 shows the workflow of the excitation current generating circuit. The process of using the excitation current generating circuit to assist the battery system in performing a complete impedance spectrum measurement is as follows:

[0072] (1) In the initial stage of operation of the excitation current generating circuit, the reference value U of the DC side capacitor voltage is first determined according to the battery system operating conditions. ref Excitation current AC reference signal i ref Control parameters, etc.

[0073] (2) Disconnect K1, then close K0 and K2 of the pre-charge circuit to connect the DC bus.

[0074] (3) The control system enters the start-up working mode.

[0075] (4) Wait for the DC side capacitor voltage U dc The set value has been reached.

[0076] (5) Wait for the excitation current generating circuit to enter a stable working state.

[0077] (6) Close K1 and disconnect K2 of the precharge circuit.

[0078] (7) The excitation current generating circuit enters the steady-state working mode.

[0079] (8) Modify the control parameters according to the impedance spectrum measurement requirements so that the excitation current generating circuit can stably generate the excitation current with the set frequency and amplitude on the battery system.

[0080] (9) Measurement of battery system impedance spectrum: Whether measuring the system impedance or the impedance spectrum of the battery pack or cell, it is necessary to measure the impedance at multiple characteristic frequencies. Therefore, according to the impedance spectrum measurement requirements, the excitation current generating circuit needs to be controlled to sequentially change the excitation current at different characteristic frequencies. In this working step, the host computer control system controls the excitation current generating circuit to sequentially generate excitation currents at each characteristic frequency until the battery impedance spectrum measurement is completed. This excitation current acts on the entire battery system, and any cell in the battery system will be subjected to the excitation current. At this time, according to the impedance spectrum measurement requirements, the impedance spectrum of any cell in the battery system can be accurately measured through the impedance spectrum measurement circuit combined with the BMS system.

[0081] (10) Disconnect K1 and K0. The impedance spectrum measurement process is now complete.

[0082] By connecting an excitation current generating circuit in parallel to the DC bus of the energy storage system, an excitation current suitable for impedance spectrum measurement is generated on each parallel battery cluster of the battery system. This requires no adjustments to existing equipment in the energy storage system and allows it to operate in parallel with the existing equipment without interfering with it. Before operation, the excitation current generating circuit needs to receive control parameters from the host computer control system, including the DC-side capacitor voltage reference value U. ref The values ​​are set according to the DC-side capacitor type and DC bus voltage, and the excitation current AC reference signal i is used. ref The frequency and amplitude are determined based on the impedance spectrum measurement requirements. According to the parallel current shunting principle, the more parallel battery clusters there are, the higher the excitation current i needs to be to ensure that the amplitude of the excitation current shunted to each battery cluster meets the impedance spectrum measurement requirements. dis The amplitude should also be larger.

[0083] The excitation current generating circuit can be modularly designed and used as a general excitation current source.

[0084] The following is an application example of the present invention.

[0085] Referring to the structures and specifications widely used in current energy storage power station construction, the battery cells in the energy storage power station battery container are 3.2V / 280Ah, arranged in a 16×1P400S configuration. Specifically, 20 cells are first connected in series to form a battery box, then 20 battery boxes are connected in series to form a battery cluster, and finally 16 battery clusters are connected in parallel to form a battery container. The nominal voltage of the battery container is 1280V, and the operating voltage is 1000~1460V. This embodiment refers to the actual energy storage power station system structure, setting the excitation current generation circuit and battery system parameters as shown in Table 1.

[0086] Table 1. Setting parameters of the excitation current generating circuit and battery system in this embodiment.

[0087]

[0088] This embodiment addresses the excitation current requirement for measuring the cell impedance spectrum of a single parallel battery cluster. If it is necessary to simultaneously measure the impedance spectrum of each cell in multiple parallel battery clusters, the excitation current and the excitation current generation circuit can be expanded.

[0089] The waveforms of this specific embodiment are shown in Figures 7 and 8. Figure 7 illustrates the functional effect of freely setting the amplitude and frequency of the current at the port of the excitation current generation circuit. After each change in the current frequency or amplitude, the current waveform can quickly enter a stable state, providing the excitation current conditions for impedance spectrum measurement. The specific values ​​and changes in frequency and amplitude can be determined by the impedance spectrum measurement requirements and adjusted in real time.

[0090] Figure 8 illustrates the sinusoidal waveform of the excitation current generation circuit port current and its power loss. As shown in Table 1, the equivalent internal resistance of the battery system is set to 1.6Ω, simulating the total internal resistance of 400 cells with a resistance of 4mΩ connected in series. This equivalent internal resistance of the battery system will generate energy loss under the action of the excitation current. Simultaneously, in the loop formed by the excitation current generation circuit and the battery system, non-ideal line resistances and device resistances will also generate energy loss under the action of the excitation current. Figure 8 shows that generating an excitation current of 5A amplitude required for measuring the cell impedance spectrum on a cluster of batteries with a nominal voltage of 1280V results in an active power loss of only 83W. Furthermore, this energy loss is provided by the battery system itself, requiring no additional energy source input.

[0091] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An excitation current generating circuit for battery impedance spectrum measurement, characterized in that, include: Voltage sensor, DC side capacitor C d The full-bridge circuit consists of switching transistors Q1, Q2, Q3, and Q4, their anti-parallel diodes, current sensor b, filter inductor L1, filter inductor L2, and filter capacitor C. A Current sensor a, switches K1 and K2 forming the pre-charge circuit, and current-limiting resistor R y Switch K0; the excitation current generating circuit is connected in parallel to the battery system via switch K0; wherein, the DC side capacitor C d The following components are connected in sequence: a full-bridge circuit, current sensor b, filter inductor L1, filter inductor L2, current sensor a, and pre-charge circuit. The other end of the pre-charge circuit is connected to the positive DC bus of the battery system via K0. Switches Q1 and Q3 are connected in series, and switches Q2 and Q4 are connected in series. One end of current sensor b is connected to filter inductor L1, and the other end is connected to the node between Q1 and Q3. Filter capacitor C... A One end is connected to the node between L1 and L2, and the other end is connected to the node between Q2 and Q4. The node between Q2 and Q4 is connected to the negative terminal of the DC bus of the battery system through K0; the voltage sensor is connected in parallel to the DC-side capacitor C. d Both ends; a voltage sensor is used to sample the DC-side capacitance C. d Voltage U across the terminals dc Current sensor a is used to sample the current i at the port of the excitation current generation circuit. dis Current sensor b is used to sample the output current i of the full-bridge circuit. o Excitation current generating circuit port current i dis The positive direction is defined as the flow from the battery system to the excitation current generating circuit, i o The positive direction is defined as the current flowing from current sensor b to the full-bridge circuit; the mathematical model of the excitation current generating circuit is: i ref (s) minus i C (s) Subtract the feedback quantity H dis i dis The error signal after (s) is input to the current regulator G. i (s) Perform conditioning calculations, current regulator G i The opposite of the output quantity of (s) minus the feedback quantity H CA i CA The error signal input after (s) characterizes the delay G of the digital control system. d (s) stage, G d (s) Output of the stage, input to the single-pole frequency multiplication SPWM modulation stage K SPWM K SPWM The opposite of the output of the component plus Z CA After the feedback quantity of the output quantity of the (s) stage, input 1 / Z L1 (s) stage, 1 / Z L1 The opposite of the output of the (s) stage plus i dis i is obtained after the feedback quantity of (s). CA (s), i CA (s) Input Z CA (s) stage, Z CA The opposite of the output of the (s) stage plus U b After (s), enter 1 / Z L2 (s) stage, 1 / Z L2 The output of the (s) stage is the port current i of the excitation current generating circuit. dis (s); where i ref (s) is the AC reference signal for the excitation current, i C (s) characterize i dis The energy exchange current in (s) excluding the AC excitation current component, H dis For i dis The sampling feedback coefficients of (s), i CA (s) represents the filter capacitor current, derived from i dis (s) sampled signal minus i o The sampled signal (s) is obtained, H CA For i CA The sampling feedback coefficients of (s), K SPWM Z is the transfer function of the SPWM modulator. L1 (s), Z L2 (s), Z CA (s) represent the filter inductor L1, filter inductor L2, and filter capacitor C, respectively. A The impedance, U b (s) is the DC bus voltage connected after the excitation current generating circuit is turned on by the battery system.

2. The excitation current generating circuit according to claim 1, characterized in that, The simplified mathematical model of the excitation current generating circuit is: i ref (s) minus i C (s) Subtract the feedback quantity H dis i dis The error signal after (s) is input to G. x1 (s) stage, G x1 The output of the (s) stage plus U b (s) followed by G x2 (s) stage, G x2 The output of the (s) stage is the port current i of the excitation current generating circuit. dis (s); where G x1 (s) and G x2 The expression for (s) is: 。 3. The excitation current generating circuit according to claim 2, characterized in that, Port current i of the excitation current generating circuit dis (s) is represented as: in: Z p (s) represents the equivalent impedance that characterizes the power loss of the excitation current generating circuit.

4. A control method for an excitation current generating circuit as described in any one of claims 1 to 3, characterized in that, Includes the following steps: In the initial stage of operation of the excitation current generating circuit, K0 and K2 in the pre-charge circuit are closed first, while K1 is opened. At this time, the battery system supplies power to the DC-side capacitor C through the anti-parallel diode in the full-bridge circuit. d Charging; at the initial connection between the excitation current generating circuit and the battery system, the DC side capacitor C... d The two ends are equivalent to a short circuit, and the current-limiting resistor R in the pre-charge circuit y It serves to limit current and prevent C d Excessive initial charging current can burn out the battery or switching devices; wait for the DC side capacitor voltage U dc Once the set reference value is reached, K1 is closed and K2 is opened, and the excitation current generating circuit enters a stable working state, generating the set excitation current.

5. The control method according to claim 4, characterized in that, During the generation of the excitation current, the excitation current generating circuit, in order to ensure that the DC side capacitor voltage U... dc Stable, U is adjusted through the DC voltage outer loop. dc The specific implementation method is as follows: set the DC-side capacitor voltage reference value U ref Subtract the DC side capacitor voltage sampling signal U dc The error signal is sent to the voltage regulator G. v (s), G v The output of (s) is used as i dis The reference signal i of the energy exchange current excluding the AC excitation current component in (s) C (s); excitation current AC reference signal i ref (s) minus i C (s) Subtract the feedback quantity H dis i dis The error signal after (s) is input to G. i (s) stage, G i The opposite of the output of the (s) stage minus H CA i CA (s) then the modulated wave signal v is obtained. MA v MA The drive signals for the switching transistors Q1 to Q4 are obtained by unipolar frequency doubling SPWM modulation.

6. The control method according to claim 4, characterized in that, After the excitation current generating circuit enters steady-state operating mode, the control parameters are modified according to the impedance spectrum measurement requirements to ensure that the excitation current generating circuit stably generates an excitation current of the set frequency and amplitude on the battery system; wherein, the control parameters include the DC side capacitor voltage reference value U. ref and excitation current AC reference signal i ref (s).

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