Online Impedance Measurement System and Method for Battery Modules Based on Reactive Current Injection

Abstract

This invention relates to an online impedance measurement system and method for battery modules based on reactive current injection, belonging to the fields of battery management, battery thermal runaway prediction, and battery health estimation. This invention solves the problems of severe overheating in traditional AC signal injection methods for online impedance measurement, making them unsuitable for high-voltage battery modules, and incomplete impedance information measurement. The control unit controls the charging and discharging of capacitor C in the reactive current generation circuit, generating reactive current, which is then injected into the battery pack. This causes voltage fluctuations across the battery pack, which are then filtered by a high-pass filter. The control unit extracts impedance based on the received reactive current and the filtered voltage fluctuations, thereby measuring the complex impedance amplitude, real axis value, imaginary axis value, and angle. This invention is primarily used in the field of battery impedance measurement.

Description

Technical Field

[0001] This invention belongs to the fields of battery management, battery thermal runaway prediction, and battery health estimation. Background Technology

[0002] Lithium-ion batteries are playing an increasingly important role in electric vehicles, energy storage power stations, and UPS backup power supplies. Battery impedance can not only estimate the state of charge (SOC) and predict safety risks, but also assess battery health, making it a crucial parameter for lithium-ion battery management systems. Therefore, online impedance measurement of lithium-ion batteries and their modules is of great significance.

[0003] The AC signal injection method is a classic method for measuring battery internal resistance. The literature (Jiang Li. Research on Online Monitoring System of Valve-Regulated Sealed Lead-Acid Battery. Wuhan University of Technology) introduces the principle of measuring battery internal resistance using the AC signal injection method. Traditional AC impedance injection methods suffer from susceptibility to interference, inability to measure at multiple frequency points, and low accuracy. The literature (Fan Shaogui, You Jiang, Gong Bing, et al., An Online Measurement Method for Battery Internal Resistance Using SOGI, ZL202010606877.0) proposes a battery internal resistance detection method based on SOCI, overcoming the shortcomings of the traditional AC current injection method. However, current methods for detecting battery internal resistance based on AC signal injection rely on resistors or power switches for AC current injection. The injected AC current generates significant heat on the discharge resistor or power switch, increasing the heat dissipation burden on the measurement system and making it unsuitable for measuring high-voltage battery modules. Furthermore, current methods for detecting battery internal resistance based on AC signal injection often measure the equivalent series internal resistance while neglecting information such as equivalent capacitive reactance and inductive reactance, resulting in incomplete measurement information. Therefore, it is necessary to design a battery module impedance measurement method to reduce system losses and heat generation, enabling the impedance measurement system to be applied to high-voltage battery modules, and providing equivalent series internal resistance, capacitive reactance, inductive reactance, etc., enriching the measurement information. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of severe heat generation in the measurement system, which makes it unsuitable for measuring high-voltage battery modules, and incomplete impedance information in traditional online impedance measurement methods. This invention provides an online impedance measurement method for battery modules based on reactive current injection.

[0005] The battery module impedance online measurement system based on reactive current injection includes a reactive current generation circuit, a low-pass filter, a high-pass filter, and a control unit.

[0006] The reactive current generation circuit is used to generate reactive current i L ;

[0007] A low-pass filter is used to filter the voltage u across capacitor C in a reactive current generation circuit.C After low-pass filtering, the signal is sent to the control unit;

[0008] A high-pass filter is used to filter reactive current i L The voltage fluctuation u across the battery pack caused by the action on the battery pack. BE Perform high-pass filtering and convert the voltage fluctuation u after high-pass filtering. BE Sent to the control unit;

[0009] The control unit is used to control the reactive current generation circuit to generate reactive current i L It is also used to determine the voltage u across capacitor C after low-pass filtering received at the current moment. C and reactive current i L The voltage u across capacitor C at the next moment is controlled by a dual-loop voltage and current control method. C and reactive current i L It is used for control; it is also used to control the reactive current i received at the current moment. L and the voltage fluctuation after high-pass filtering u BE Impedance extraction is performed to measure the complex impedance amplitude, the complex impedance real axis value, the complex impedance imaginary axis value, and the complex impedance angle.

[0010] Among them, the control unit controls the voltage u across capacitor C. C The control performed is a voltage loop control; the control unit controls the reactive current i L The magnitude of the reactive current i is controlled as current loop control; L The current is alternating current. During the first half of the cycle, capacitor C is in a charging state, and during the second half of the cycle, capacitor C is in a discharging state.

[0011] Preferably, the reactive current generating circuit includes an inductor L, a switching transistor S1, a switching transistor S2, and a capacitor C; the positive terminal of the switching transistor S1 is connected to one end of the capacitor C, and the negative terminal of the switching transistor S2 is connected to the other end of the capacitor C; the negative terminal of the switching transistor S1, the positive terminal of the switching transistor S2, and one end of the inductor L are connected, and the other end of the inductor L serves as the output terminal of the reactive current generating circuit.

[0012] The control terminals of switching transistors S1 and S2 are respectively used to receive the first drive signal G output by the control unit. S1 Second drive signal G S2 ;

[0013] The reactive current i generated by the reactive current generation circuit L The current flowing through inductor L is denoted as .

[0014] Preferably, based on the voltage u across capacitor C after low-pass filtering received at the current moment... C and reactive current i LThe voltage u across capacitor C at the next moment is controlled by a dual-loop voltage and current control method. C and reactive current i L The method for controlling the size is as follows:

[0015] The control unit receives the voltage u across capacitor C after low-pass filtering at the current moment. C and reactive current i L Generate the first driving signal G S1 Second drive signal G S2 And using the first driving signal G S1 Second drive signal G S2 The switching states of transistors S1 and S2 are controlled to regulate the charging and discharging of capacitor C, thereby controlling the voltage across capacitor C and the reactive current i at the next moment. L Control.

[0016] Preferably, the control unit includes four analog-to-digital converters (ADCs), a capacitor voltage setting module, two subtractors, a voltage loop controller, a current loop controller, a PWM generation module, and an impedance extraction module.

[0017] The first analog-to-digital converter (ADC) receives the high-pass filtered voltage u across the battery pack. B After analog-to-digital conversion, the signal is sent to the capacitor voltage setting module. The capacitor voltage setting module then adjusts the voltage based on the received analog-to-digital converted voltage u. B Generate capacitor voltage setpoint u Cref and its capacitor voltage given value u Cref The result is sent to the minuend input of the first subtractor.

[0018] The second analog-to-digital converter (ADC) measures the voltage u across the capacitor C after receiving the low-pass filter. C After analog-to-digital conversion, the converted voltage u C The input is sent to the subtrahend input of the first subtractor.

[0019] The difference output from the first subtractor is sent to the voltage loop controller. The voltage loop controller generates a DC bias signal for a given sinusoidal current signal based on the received difference and sends the DC bias signal to the first minuend input of the second subtractor. The DC bias signal serves as the voltage loop control command.

[0020] The second subtractor's input terminal 2 is used to receive a given sinusoidal current signal;

[0021] The third analog-to-digital converter (ADC) processes the received reactive current i L Perform analog-to-digital conversion, and convert the reactive current i after analog-to-digital conversion. LSimultaneously, the signal is sent to the subtrahend input of the second subtractor and the impedance extraction module;

[0022] The difference output from the second subtractor is sent to the current loop controller, which generates a current loop control command based on the received difference and sends it to the PWM generation module.

[0023] The PWM generation module generates two complementary PWM signals based on the received current loop control command, and the two complementary PWM signals are used as the first drive signal G. S1 Second drive signal G S2 Control the switching transistors S1 and S2;

[0024] The fourth analog-to-digital converter (ADC) receives the high-pass filtered voltage fluctuation u. BE Perform analog-to-digital conversion and convert the voltage fluctuation u after the analog-to-digital conversion. BE Send to the impedance extraction module;

[0025] The impedance extraction module is used to extract the reactive current i after analog-to-digital conversion. L Voltage fluctuation u after analog-to-digital conversion BE Impedance extraction is performed to measure the complex impedance amplitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle.

[0026] Preferably, the PWM generation module includes a comparator and an inverter;

[0027] The positive input of the comparator is used to receive the current loop control command output by the current loop controller;

[0028] The negative input of the comparator is used to receive high-frequency carrier signals;

[0029] The PWM signal output from the comparator is used as the first drive signal G. S1 ;

[0030] The inverter is used to invert the PWM signal output from the comparator to obtain the first drive signal G. S2 .

[0031] Preferably, the implementation methods for the complex impedance magnitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle include:

[0032] First, the SOGI algorithm is used to calculate the reactive current i at a given frequency ω. L and voltage fluctuation u BE Filter and extract i at a given frequency ω. LF u BEF qi LF and qu BEF ;

[0033] Where ω is the given frequency of the given sinusoidal current signal; i LF For the reactive current i at a given frequency ω L The extracted current signal, u BEF The voltage fluctuation u at a given frequency ω BE The extracted voltage signal, qi LF For i LF orthogonal signals, qu BEF For u BEF The orthogonal signals, where q is the orthogonal sign;

[0034] Secondly, according to i LF and qi LF , get i L Amplitude I L At the same time, also according to u BEF and qu BEF , get u BE amplitude U BE Specifically:

[0035]

[0036]

[0037] Finally, according to I L U BE i LF u BEF Based on the principle of battery internal resistance detection, the complex impedance amplitude Z and the complex impedance real axis value Z are obtained. RE The imaginary axis value of the complex impedance Z IM and complex impedance angle Specifically:

[0038]

[0039]

[0040]

[0041]

[0042] LPF(·) is a low-pass filter operation.

[0043] As a preferred option, u Cref =1.2u B .

[0044] Preferably, both the voltage loop controller and the current loop controller are implemented using PI controllers.

[0045] Preferably, the control unit is implemented using an MCU.

[0046] The measurement method implemented by the online battery module impedance measurement system based on reactive current injection includes the following steps:

[0047] Step 1: The control unit controls the charging and discharging of capacitor C in the reactive current generation circuit, causing the reactive current generation circuit to generate reactive current i. L and the reactive current i L After being injected into the battery pack, causing voltage fluctuations across the battery pack terminals, the voltage fluctuation amount u across the battery pack terminals is then... BE After being high-pass filtered, the signal is sent to the control unit.

[0048] Step 2: The control unit calculates the reactive current i received at the current moment. L and the voltage fluctuation after high-pass filtering u BE Impedance extraction is performed to measure the complex impedance amplitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle.

[0049] This invention proposes a method for measuring battery pack impedance by injecting reactive current into the battery pack, and presents a circuit for generating the reactive current and a reactive current control strategy. The reactive current flows between the capacitor and the battery pack, theoretically without generating losses. Traditional AC injection methods use resistors and power transistor discharge to inject AC signals, resulting in minimal losses when the battery voltage is low. However, as the battery pack voltage increases, the losses increase dramatically. Therefore, traditional AC current injection methods are suitable for testing low-voltage individual battery cells but not for testing high-voltage battery modules. This invention, by processing the voltage and current signals, can calculate the complex impedance amplitude, real-axis impedance value, imaginary-axis impedance value, and impedance angle, obtaining more comprehensive impedance information.

[0050] Advantages of this invention:

[0051] 1. Due to the use of reactive current injection during the measurement process, the losses are relatively small, which reduces the heat dissipation burden of the measurement system and allows for a smaller size.

[0052] 2. The tested battery pack has a wide voltage range, applicable to both low-voltage and high-voltage battery modules for impedance measurement. Due to the reactive current injection method, losses during high-voltage module measurement are also minimal. This method is suitable for impedance strategies in high-voltage battery packs, providing accurate battery impedance information for online thermal runaway fault monitoring, lifetime estimation, and state-of-charge estimation of battery modules.

[0053] 3. It can measure impedance information such as the complex impedance amplitude, real axis value, imaginary axis value, and complex impedance angle of the battery module, enriching the measurement information. Traditional methods can only measure the equivalent series internal resistance. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the principle of an online battery module impedance measurement system based on reactive current injection;

[0055] Figure 2 This is a schematic diagram of the PWM generation module.

[0056] Figure 3 This is a schematic diagram illustrating the principle of impedance extraction.

[0057] Figure 4 This is a diagram illustrating the structure of a complex impedance.

[0058] Figure 5 This is a schematic diagram of the control unit 4. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0061] Example 1:

[0062] See Figure 1 This embodiment 1 describes the online battery module impedance measurement system based on reactive current injection, which includes a reactive current generation circuit 1, a low-pass filter 2, a high-pass filter 3, and a control unit 4.

[0063] Reactive current generation circuit 1 is used to generate reactive current i L ;

[0064] Low-pass filter 2 is used to filter the voltage u across capacitor C in reactive current generation circuit 1. C After low-pass filtering, the signal is sent to control unit 4;

[0065] High-pass filter 3 is used for reactive current i L The voltage fluctuation u across the battery pack caused by the action on the battery pack. BE Perform high-pass filtering and convert the voltage fluctuation u after high-pass filtering. BE Sent to control unit 4;

[0066] Control unit 4 is used to control the reactive current generation circuit 1 to generate reactive current iL It is also used to determine the voltage u across capacitor C after low-pass filtering received at the current moment. C and reactive current i L The voltage u across capacitor C at the next moment is controlled by a dual-loop voltage and current control method. C and reactive current i L The magnitude is controlled; it is also used to control the reactive current i received at the current moment. L and the voltage fluctuation after high-pass filtering u BE Impedance extraction is performed to measure the complex impedance amplitude, the complex impedance real axis value, the complex impedance imaginary axis value, and the complex impedance angle.

[0067] Among them, the control unit 4 controls the voltage u across capacitor C. C The magnitude is controlled as voltage loop control; control unit 4 controls the reactive current i L The magnitude of the voltage loop is controlled as the current loop control; and the voltage loop is the outer loop, while the current loop is the inner loop.

[0068] reactive current i L The current is alternating current. During the first half of the cycle, capacitor C is in a charging state, and during the second half of the cycle, capacitor C is in a discharging state. Energy flows between capacitor C and the battery pack, and theoretically, no loss occurs.

[0069] Considering the reactive current i in the actual system L There may be a DC bias, which will cause the voltage of capacitor C to continuously rise or fall. Therefore, a voltage loop is implemented. The goal of the voltage loop control is to ensure that the voltage of capacitor C remains within a reasonable range.

[0070] Considering the capacitor voltage u C The existence and injection of reactive current i L Fluctuations at the same frequency, therefore, before entering the sampling of control unit 4, the capacitor voltage u C It needs to pass through a low-pass filter, and the cutoff frequency of the low-pass filter can be set to 0.1 times the sinusoidal current frequency.

[0071] Figure 1 and Figure 5 The specific structure of reactive current generation circuit 1 is given in both sections, which uses a complementary first drive signal G. S1 Second drive signal G S2 To achieve reactive current i L The reactive current generating circuit 1 includes an inductor L, a switching transistor S1, a switching transistor S2, and a capacitor C; the positive terminal of the switching transistor S1 is connected to one end of the capacitor C, and the negative terminal of the switching transistor S2 is connected to the other end of the capacitor C; the negative terminal of the switching transistor S1, the positive terminal of the switching transistor S2, and one end of the inductor L are connected, and the other end of the inductor L serves as the output terminal of the reactive current generating circuit 1.

[0072] The control terminals of switching transistors S1 and S2 are respectively used to receive the first drive signal G output by control unit 4. S1 Second drive signal G S2 ;

[0073] The reactive current i generated by reactive current generation circuit 1 L The current flowing through inductor L is denoted as .

[0074] In specific applications, switching transistors S1 and S2 can be either MOSFETs or IGBTs.

[0075] The online impedance measurement system for battery modules based on reactive current injection described in this invention mainly includes two aspects: first, reactive current i L The control process includes, firstly, the process of obtaining the complex impedance amplitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle.

[0076] See Figure 1 Furthermore, the control unit 4 determines the voltage u across the low-pass filtered capacitor C received at the current moment. C and reactive current i L The voltage u across capacitor C at the next moment is controlled by a dual-loop voltage and current control method. C and reactive current i L The method for controlling the size is as follows:

[0077] Control unit 4 receives the voltage u across capacitor C after low-pass filtering at the current moment. C and reactive current i L Generate the first driving signal G S1 Second drive signal G S2 And using the first driving signal G S1 Second drive signal G S2 The switching states of transistors S1 and S2 are controlled to regulate the charging and discharging of capacitor C, thereby controlling the voltage across capacitor C and the reactive current i at the next moment. L Control.

[0078] Figure 5 The specific internal structure of control unit 4 is given in the figure. Control unit 4 generates the first drive signal G. S1 Second drive signal G S2 For the principle, see Figure 5 Control unit 4 includes four analog-to-digital converters (ADCs), a capacitor voltage setting module, two subtractors, a voltage loop controller, a current loop controller, a PWM generation module, and an impedance extraction module.

[0079] The first analog-to-digital converter (ADC) receives the high-pass filtered voltage u across the battery pack. B After analog-to-digital conversion, the signal is sent to the capacitor voltage setting module. The capacitor voltage setting module then adjusts the voltage based on the received analog-to-digital converted voltage u. B Generate capacitor voltage setpoint u Cref and its capacitor voltage given value u Cref The result is sent to the minuend input of the first subtractor.

[0080] The second analog-to-digital converter (ADC) measures the voltage u across the capacitor C after receiving the low-pass filter. C After analog-to-digital conversion, the converted voltage u C The input is sent to the subtrahend input of the first subtractor.

[0081] The difference output from the first subtractor is sent to the voltage loop controller. The voltage loop controller generates a DC bias signal for a given sinusoidal current signal based on the received difference and sends the DC bias signal to the first minuend input of the second subtractor. The DC bias signal serves as the voltage loop control command.

[0082] The second subtractor's input terminal 2 is used to receive a given sinusoidal current signal;

[0083] The third analog-to-digital converter (ADC) processes the received reactive current i L Perform analog-to-digital conversion, and convert the reactive current i after analog-to-digital conversion. L Simultaneously, the signal is sent to the subtrahend input of the second subtractor and the impedance extraction module;

[0084] The difference output from the second subtractor is sent to the current loop controller, which generates a current loop control command based on the received difference and sends it to the PWM generation module.

[0085] The PWM generation module generates two complementary PWM signals based on the received current loop control command, and the two complementary PWM signals are used as the first drive signal G. S1 Second drive signal G S2 Control the switching transistors S1 and S2;

[0086] The fourth analog-to-digital converter (ADC) receives the high-pass filtered voltage fluctuation u. BE Perform analog-to-digital conversion and convert the voltage fluctuation u after the analog-to-digital conversion. BE Send to the impedance extraction module;

[0087] The impedance extraction module is used to extract the reactive current i after analog-to-digital conversion. L Voltage fluctuation u after analog-to-digital conversion BEImpedance extraction is performed to measure the complex impedance amplitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle.

[0088] The given sinusoidal current signal is preset and generated by control unit 4. Its amplitude is typically set to around 2A, and the frequency can be set according to the characteristics of the battery pack being tested. The given sinusoidal current signal is added to the output of the voltage closed-loop controller, serving as the current reference for the current loop controller. Both the voltage and current loop controllers are PI controllers.

[0089] Figure 2 The specific structure of the PWM generation module is given, which includes a comparator and an inverter.

[0090] The positive input of the comparator is used to receive the current loop control command output by the current loop controller;

[0091] The negative input of the comparator is used to receive high-frequency carrier signals;

[0092] The PWM signal output from the comparator is used as the first drive signal G. S1 ;

[0093] The inverter is used to invert the PWM signal output from the comparator to obtain the first drive signal G. S2 .

[0094] Figure 3 A schematic diagram illustrating the principle of impedance extraction is provided. Figure 4 A diagram illustrating the construction of complex impedances is provided; for details, see [link to diagram]. Figure 3 and 4 The methods for realizing the complex impedance magnitude, the real axis value, the imaginary axis value, and the complex impedance angle include:

[0095] First, the SOGI algorithm is used to calculate the reactive current i at a given frequency ω. L and voltage fluctuation u BE Filter and extract i at a given frequency ω. LF u BEF qi LF and qu BEF ;

[0096] Where ω is the given frequency of the given sinusoidal current signal; i LF For the reactive current i at a given frequency ω L The extracted current signal, u BEF The voltage fluctuation u at a given frequency ω BE The extracted voltage signal, qi LF For i LF orthogonal signals, qu BEF For u BEFThe orthogonal signals, where q is the orthogonal sign;

[0097] Secondly, according to i LF and qi LF , get i L Amplitude I L At the same time, also according to u BEF and qu BEF , get u BE amplitude U BE Specifically:

[0098]

[0099]

[0100] Finally, according to I L U BE i LF u BEF Based on the principle of battery internal resistance detection, the complex impedance amplitude Z and the complex impedance real axis value Z are obtained. RE The imaginary axis value of the complex impedance Z IM and complex impedance angle Specifically:

[0101]

[0102]

[0103]

[0104]

[0105] LPF(·) is a low-pass filter operation.

[0106] Figure 3 The document provides a detailed implementation of the SOGI algorithm. The SOGI algorithm uses an orthogonal signal generator to extract the signal at a given frequency, exhibits strong attenuation of signals at other frequencies, and can output orthogonal signals at the given frequency, such as... Figure 3 As shown, given a frequency of ω, the current signal extracted by the SOGI quadrature signal generator is i. LF The voltage signal is u BEF The generated current and voltage orthogonal signals are qi, respectively. LF and qu BEF Based on the orthogonal signals, the current and voltage amplitudes can be calculated separately, which are I0 and I0, respectively. L and U BE Based on the principle of battery internal resistance detection using the AC injection method, the complex impedance amplitude Z and the complex impedance real axis value Z0 are obtained according to formulas 3 to 6.RE The imaginary axis value of the complex impedance Z IM and complex impedance angle

[0107] Furthermore, u Cref =1.2u B .

[0108] In practice, both the voltage loop controller and the current loop controller are implemented using PI controllers.

[0109] Control unit 4 can also be implemented using an MCU.

[0110] Example 2:

[0111] See Figure 1 This embodiment 2 describes the measurement method implemented by the online battery module impedance measurement system based on reactive current injection. The measurement method includes the following steps:

[0112] Step 1: Control unit 4 controls the charging and discharging of capacitor C in reactive current generation circuit 1, causing reactive current generation circuit 1 to generate reactive current i. L and the reactive current i L After being injected into the battery pack, causing voltage fluctuations across the battery pack terminals, the voltage fluctuation amount u across the battery pack terminals is then... BE After high-pass filtering by high-pass filter 3, the signal is sent to control unit 4;

[0113] Step 2: Control unit 4 calculates the reactive current i received at the current moment. L and the voltage fluctuation after high-pass filtering u BE Impedance extraction is performed to measure the complex impedance amplitude, real axis value, imaginary axis value, and complex impedance angle; for details, see [link to documentation]. Figure 3 and Figure 4 The methods for obtaining the complex impedance magnitude, complex impedance real axis value, complex impedance imaginary axis value, and complex impedance angle include:

[0114] First, the SOGI algorithm is used to calculate the reactive current i at a given frequency ω. L and voltage fluctuation u BE Filter and extract i at a given frequency ω. LF u BEF qi LF and qu BEF ;

[0115] Where ω is the given frequency of the given sinusoidal current signal; i LF For the reactive current i at a given frequency ω L The extracted current signal, u BEF The voltage fluctuation u at a given frequency ωBE The extracted voltage signal, qi LF For i LF orthogonal signals, qu BEF For u BEF The orthogonal signals, where q is the orthogonal sign;

[0116] Secondly, according to i LF and qi LF , get i L Amplitude I L At the same time, also according to u BEF and qu BEF , get u BE amplitude U BE Specifically:

[0117]

[0118]

[0119] Finally, according to I L U BE i LF u BEF Based on the principle of battery internal resistance detection, the complex impedance amplitude Z and the complex impedance real axis value Z are obtained. RE The imaginary axis value of the complex impedance Z IM and complex impedance angle Specifically:

[0120]

[0121]

[0122]

[0123]

[0124] LPF(·) is a low-pass filter operation.

[0125] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A battery module impedance online measurement system based on reactive current injection, characterized in that, It includes a reactive current generation circuit (1), a low-pass filter (2), a high-pass filter (3), and a control unit (4). The reactive current generation circuit (1) is used to generate reactive current. ; The low-pass filter (2) is used to filter the voltage across capacitor C in the reactive current generation circuit (1). After low-pass filtering, the signal is sent to the control unit (4). A high-pass filter (3) is used to filter reactive current. The voltage fluctuation across the battery pack caused by the action on the battery pack. Perform high-pass filtering and then filter the voltage fluctuation after high-pass filtering. Send to the control unit (4); The control unit (4) is used to control the reactive current generation circuit (1) to generate reactive current. It is also used to determine the voltage across capacitor C after low-pass filtering received at the current moment. and reactive current The voltage and current dual-loop control method is used to control the voltage across capacitor C at the next moment. and reactive current It is used for control; it is also used to determine the reactive current received at the current moment. Voltage fluctuation after high-pass filtering Impedance extraction is performed to measure the complex impedance amplitude, the complex impedance real axis value, the complex impedance imaginary axis value, and the complex impedance angle. Among them, the control unit (4) controls the voltage across capacitor C. The control performed is a voltage loop control; the control unit (4) controls the reactive current. The magnitude of reactive current is controlled as current loop control; The current is alternating current. During the first half of the cycle, capacitor C is in a charging state, and during the second half of the cycle, capacitor C is in a discharging state.

2. The online battery module impedance measurement system based on reactive current injection according to claim 1, characterized in that, The reactive current generating circuit (1) includes an inductor L, a switch S1, a switch S2 and a capacitor C; the positive terminal of the switch S1 is connected to one end of the capacitor C, and the negative terminal of the switch S2 is connected to the other end of the capacitor C; the negative terminal of the switch S1, the positive terminal of the switch S2 and one end of the inductor L are connected, and the other end of the inductor L serves as the output terminal of the reactive current generating circuit (1). The control terminals of switching transistors S1 and S2 are respectively used to receive the first drive signal output by the control unit (4). Second drive signal ; The reactive current generated by the reactive current generation circuit (1) The current flowing through inductor L is denoted as .

3. The measurement method implemented by the online battery module impedance measurement system based on reactive current injection according to claim 2, characterized in that, Based on the voltage across capacitor C after low-pass filtering received at the current moment and reactive current The voltage and current dual-loop control method is used to control the voltage across capacitor C at the next moment. and reactive current The method for controlling the size is as follows: The control unit (4) determines the voltage across capacitor C after low-pass filtering based on the current received voltage. and reactive current Generate the first driving signal Second drive signal and using the first drive signal Second drive signal The switching states of transistors S1 and S2 are controlled to regulate the charging and discharging of capacitor C, thereby controlling the voltage and reactive current across capacitor C at the next moment. Control.

4. The online battery module impedance measurement system based on reactive current injection according to claim 1, characterized in that, The control unit (4) includes four analog-to-digital converters (ADCs), a capacitor voltage setting module, two subtractors, a voltage loop controller, a current loop controller, a PWM generation module, and an impedance extraction module. The first analog-to-digital converter (ADC) receives the high-pass filtered voltage across the battery pack. After analog-to-digital conversion, the signal is sent to the capacitor voltage setting module, which then determines the voltage based on the received analog-to-digital converted signal. Generate capacitor voltage setpoint and its capacitor voltage given value The result is sent to the minuend input of the first subtractor. The second analog-to-digital converter (ADC) measures the voltage across capacitor C after receiving the low-pass filtered signal. After analog-to-digital conversion, the voltage after analog-to-digital conversion is... The input is sent to the subtrahend input of the first subtractor. The difference output from the first subtractor is sent to the voltage loop controller. The voltage loop controller generates a DC bias signal for a given sinusoidal current signal based on the received difference and sends the DC bias signal to the first minuend input of the second subtractor. The DC bias signal serves as the voltage loop control command. The second subtractor's input terminal 2 is used to receive a given sinusoidal current signal; The third analog-to-digital converter (ADC) receives the reactive current. Perform analog-to-digital conversion and convert the reactive current after analog-to-digital conversion. Simultaneously, the signal is sent to the subtrahend input of the second subtractor and the impedance extraction module; The difference output from the second subtractor is sent to the current loop controller, which generates a current loop control command based on the received difference and sends it to the PWM generation module. The PWM generation module generates two complementary PWM signals based on the received current loop control command, and the two complementary PWM signals are used as the first drive signals. Second drive signal Control the switching transistors S1 and S2; The fourth analog-to-digital converter (ADC) receives the high-pass filtered voltage fluctuation u. BE Perform analog-to-digital conversion and convert the voltage fluctuation u after the analog-to-digital conversion. BE Send to the impedance extraction module; Impedance extraction module, used to extract reactive current after analog-to-digital conversion. Voltage fluctuation u after analog-to-digital conversion BE Impedance extraction is performed to measure the complex impedance amplitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle.

5. The online battery module impedance measurement system based on reactive current injection according to claim 4, characterized in that, The PWM generation module includes a comparator and an inverter; The positive input of the comparator is used to receive the current loop control command output by the current loop controller; The negative input of the comparator is used to receive high-frequency carrier signals; The PWM signal output from the comparator is used as the first drive signal. ; The inverter is used to invert the PWM signal output from the comparator to obtain the first drive signal. .

6. The online battery module impedance measurement system based on reactive current injection according to any one of claims 1 to 5, characterized in that, The methods for realizing the complex impedance magnitude, the real axis value, the imaginary axis value, and the complex impedance angle include: First, the SOGI algorithm is used to determine the given frequency. reactive current at the location and voltage fluctuation Filter and extract the given frequency place , , and ; in, The given frequency is a given sinusoidal current signal; For a given frequency From reactive current at the location The extracted current signal For a given frequency Voltage fluctuation at the location The voltage signal extracted from it. for orthogonal signals, for orthogonal signals, Orthogonal symbol; Secondly, according to and ,get amplitude At the same time, also according to and ,get amplitude Specifically: Formula 1: Formula 2: Finally, according to , , , By combining the battery internal resistance detection principle, the complex impedance amplitude is obtained. Real axis value of complex impedance Complex impedance imaginary axis value and complex impedance angle Specifically: Formula 3: Formula 4: Formula 5: Formula 6: in, This is a low-pass filter operation.

7. The online battery module impedance measurement system based on reactive current injection according to claim 4, characterized in that, 。 8. The online battery module impedance measurement system based on reactive current injection according to claim 4, characterized in that, Both the voltage loop controller and the current loop controller are implemented using PI controllers.

9. The online battery module impedance measurement system based on reactive current injection according to claim 1, characterized in that, The control unit (4) is implemented using an MCU.

10. The measurement method implemented by the online battery module impedance measurement system based on reactive current injection according to claim 1, characterized in that, The measurement method includes the following steps: Step 1: The control unit (4) controls the charging and discharging of capacitor C in the reactive current generation circuit (1) to generate reactive current. and the reactive current After being injected into the battery pack, causing voltage fluctuations across the battery pack terminals, the amount of voltage fluctuation across the battery pack terminals is then... After high-pass filtering by high-pass filter (3), the signal is sent to control unit (4). Step 2: Control unit (4) determines the reactive current received at the current moment. Voltage fluctuation after high-pass filtering Impedance extraction is performed to measure the complex impedance amplitude, the real axis value of the complex impedance, the imaginary axis value of the complex impedance, and the complex impedance angle.

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