High-voltage battery micro internal resistance measuring device based on resonant coupling

Abstract

The invention discloses a high-voltage battery micro internal resistance measuring device based on resonant coupling, which is characterized in that a main controller is connected with an excitation conditioning circuit through an analog output port and is connected with a switch phase detection circuit through an analog input port and a digital output port, and the excitation conditioning circuit is directly connected with an alternating current source circuit; the alternating current source circuit is directly connected with the coupling circuit, a battery interface in the coupling circuit is connected with the sampling amplification circuit after being isolated by a capacitor, and the sampling amplification circuit is directly connected with the switch phase detection circuit. The device can be compatible with impedance measurement of 0V-2500V passive and active devices, can measure internal resistance of 400V and 800V platform automobile batteries, is compatible with internal resistance test of a whole station and a whole group of 750V, 1500V and 2500V energy storage power stations, and supports measurement in charging and discharging processes.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-voltage battery impedance measurement, and in particular relates to a high-voltage battery micro-internal resistance measurement device based on resonant coupling. Background Art

[0002] With the large-scale development of electric vehicles and energy storage power stations, the number of batteries that need to be monitored and managed is extremely large. Given the strong correlation between battery internal resistance and battery thermal runaway, it can play a key role in early warning and diagnosis of thermal runaway. With the help of battery internal resistance, the battery's state of charge and health status can be estimated relatively accurately, and then corresponding maintenance and management strategies and measures can be formulated, ultimately achieving the goal of extending the battery's service life.

[0003] In the field of battery internal resistance measurement, traditional measurement equipment is often limited to the measurement function of a single battery. Although high-voltage measuring instruments can meet the needs of high-voltage measurement, they are expensive and bulky, which seriously hinders their deployment and application in large-scale scenarios. From the current application platform of automotive batteries, they are mainly concentrated in the 400V and 800V range. At the same time, energy storage power stations have shown a high-voltage development trend of 1500V, and even 2500V power stations will be planned and built in the future. Considering the dimension of commercial operation, the price factor is undoubtedly an extremely critical and decisive indicator. Based on this, the development of a low-cost, small-volume high-voltage battery internal resistance measurement method has become a core problem that needs to be solved in the current high-voltage battery field. Summary of the invention

[0004] In view of the above problems, the present invention proposes a high-voltage battery micro-internal resistance measurement device based on resonant coupling, which aims to achieve safe and efficient measurement of the internal resistance of a whole pack of automotive batteries and a whole cluster of high-voltage batteries in an energy storage power station, and can quickly measure the battery internal resistance of up to 2500V at low cost and without damaging the battery.

[0005] A high-voltage battery micro-internal resistance measuring device based on resonant coupling comprises a main controller, an excitation conditioning circuit, an AC current source circuit, a resonant coupling circuit, a sampling amplifier circuit and a switch phase detection circuit.

[0006] The main controller is connected to the excitation conditioning circuit through an analog output port, and is connected to the switch phase detection circuit through an analog input port and a digital output port. The excitation conditioning circuit is directly connected to the AC current source circuit, and the AC current source circuit is directly connected to the coupling circuit. The battery interface in the coupling circuit is connected to the sampling amplifier circuit after being isolated by a high-voltage capacitor, and the sampling amplifier circuit is directly connected to the switch phase detection circuit.

[0007] The main controller uses a single-chip microcomputer as a logic controller. The controller has a built-in analog output port, which outputs an excitation analog signal with adjustable amplitude, phase, frequency, and sampling rate, and transmits it to the excitation conditioning circuit. The main controller has a built-in analog input port, and the switch phase detection circuit inputs the analog signal to the analog input port. The digital output port of the main controller controls the on-off of the analog switch of the switch phase detection circuit. The main controller uses interrupts to trigger analog input sampling and internal resistance calculation, and finally transmits the internal resistance data through the communication interface.

[0008] The excitation conditioning circuit is connected to the excitation analog signal output by the main controller, performs driving capability amplification, filtering and amplitude conditioning on the excitation analog signal, and then transmits the excitation analog signal to the AC current source circuit.

[0009] After receiving the excitation analog signal input, the AC current source circuit outputs the corresponding current through the high-power operational amplifier, and uses high-end differential current feedback to feed back the voltage through the sampling resistor to the positive and negative pins of the operational amplifier, outputting positive and negative AC currents into the resonant coupling circuit.

[0010] The resonant coupling circuit is responsible for connecting the high-voltage battery and the low-voltage measuring equipment. The positive and negative AC circuits output by the low-voltage AC current source can be transmitted to the high-voltage battery through the resonant coupling circuit, and then the high-voltage response signal is transmitted to the sampling and amplifying circuit through the resonant coupling circuit. In the resonant coupling circuit, the input end of the planar inductor is connected to the AC current source circuit and the transient voltage suppression tube, and the output end is connected to the polypropylene capacitor; the input end of the polypropylene capacitor is connected to the planar inductor, and the output end is connected to the fuse; the input end of the fuse is connected to the polypropylene capacitor, and the output end is connected to the high-voltage battery of the car / energy storage power station; the output end of the high-voltage battery of the car / energy storage power station is connected to the transient voltage suppression tube, the AC current source and the high-voltage capacitor 1; the output of the high-voltage capacitor 1 is connected to the glass glaze resistor 1, and the output of the glass glaze resistor 1 is connected to the sampling and amplifying circuit; the output of the high-voltage capacitor 2 is connected to the high-voltage battery of the car / energy storage power station; the output of the glass glaze resistor 2 is connected to the high-voltage capacitor 2, and the output of the sampling and amplifying resistor is connected to the glass glaze resistor 2.

[0011] The positive and negative AC current outputs of the AC current source circuit flow through the planar inductor, polypropylene capacitor and fuse, and then are transmitted to the positive electrode of the high-voltage battery, and then are transmitted back to the AC current source circuit through the negative electrode of the high-voltage battery; the high-voltage battery charges the high-voltage capacitor 1 and the high-voltage capacitor 2, and the charging current flows from the high-voltage battery in sequence through the high-voltage capacitor 1, the glass glaze resistor 1, the sampling amplifier circuit, the glass glaze resistor 2 and the high-voltage capacitor 2, and then flows back to the high-voltage battery.

[0012] The sampling amplifier circuit has high common-mode rejection ratio and high input impedance input characteristics. The resonant coupling circuit transmits the voltage signal responded by the excitation current flowing through the high-voltage battery of the automobile / energy storage power station to the sampling amplifier circuit for signal acquisition, amplification and bias application, and then transmits it to the switching phase detection circuit.

[0013] The switch phase detection circuit passes the battery AC voltage amplified by the sampling amplifier circuit through an analog switch to generate an AC chopping signal. The signal is transmitted to the main controller through a low-pass filter. The analog switch control signal is generated by the main controller, and the switch phase detection circuit outputs the amplitude corresponding to the set phase.

[0014] Advantages or beneficial effects of this application:

[0015] The beneficial effects of the present invention are as follows: the resonant coupling measurement device proposed in the present invention is compatible with the impedance measurement of passive and active devices of 0V-2400V, can measure the internal resistance of 400V and 800V platform automobile batteries, is compatible with the internal resistance test of the entire station and the entire group of 750V, 1500V and 2500V energy storage power stations, and supports measurement during the charging and discharging process. The impedance tracking and extraction method proposed in this application obtains the impedance amplitude by adjusting the output current phase, and reversely deduces the real and imaginary part information of the impedance based on this, which greatly improves the measurement accuracy and expands the application scope of the present invention in related fields. Through the resonantly coupled high-voltage battery internal resistance measurement method, according to the actual application requirements, the phase, amplitude, frequency and sampling rate are controlled, and the adjustable current is delivered to the high-voltage battery internal resistance through the resonant coupling circuit. In this process, the resonant coupling circuit can resonate for a specific measurement frequency and filter out noise at other frequencies, thereby effectively ensuring the measurement accuracy. The use of planar inductor design significantly reduces the height of the equipment; by realizing the inductor coil on the PCB (printed circuit board), it not only improves the processing consistency, but also reduces the winding cost and manual error, reduces the assembly steps, reduces the production error, and further ensures the stability of the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall flow chart of the embodiment;

[0017] Figure 2 This is a schematic diagram of impedance calculation interruption;

[0018] Figure 3 It is the schematic diagram of impedance tracking algorithm;

[0019] Figure 4 is a schematic diagram of a resonant coupling circuit;

[0020] Figure 5 is a schematic diagram of a switch phase detection circuit;

[0021] Figure 6 It is a schematic diagram of the measurement results fitting;

[0022] Figure 7 This is a physical picture of the device. DETAILED DESCRIPTION

[0023] Example:

[0024] refer to Figure 1 This patent provides the technical solution shown in the figure below, which is a high-voltage battery micro-internal resistance measurement device based on resonant coupling, including a main controller, an excitation conditioning circuit, an AC current source circuit, a resonant coupling circuit, a sampling and amplification circuit, and a switch phase detection circuit.

[0025] The main controller uses a single-chip microcomputer as a logic controller, sets the controller's built-in analog output port, and sets the analog output resolution to 12 bits. Through the analog output sampling rate of 100ksps to 10Msps, the preset or calculated built-in sine table is used to use a timer to trigger DMA (direct memory access) to access the analog output peripherals, and output an excitation sinusoidal AC current with adjustable amplitude, phase, frequency, and sampling rate, which is then transmitted to the excitation conditioning circuit. The main controller has a built-in analog input port, which is directly connected to the switch phase detection circuit. The analog input resolution is 12 bits, which can be increased to 16 bits through sampling. The controller uses interrupts to trigger analog input sampling and internal resistance calculation, and finally transmits the internal resistance data through the digital output port of the communication interface.

[0026] refer to Figure 2 The acquisition logic of the main controller is as follows. Wait for the timer to trigger the impedance calculation interrupt, obtain the impedance value from the analog input port, wait for the hardware to oversample and collect 256 times, and then shift the data right by 4 bits; judge the gear according to the data, set the gear switch when it is greater than the threshold, and wait for the next trigger interrupt; continue to calculate and filter the data if it meets the gear range, and then wait for data upload through CAN (Controller Area Network Bus) and the serial port.

[0027] refer to Figure 3 , the main controller uses the impedance tracking algorithm when it finds that the phase difference between the battery impedance and 0° is greater than the set angle threshold. The impedance tracking method is: initialize the phase detection signal to be in phase with the output current, call the impedance calculation interrupt to obtain the real part data of the phase detection signal, and then call the impedance calculation interrupt to obtain the imaginary part data under the phase detection signal, and use the real part and imaginary part to estimate the impedance angle. When the angle is greater than the set angle threshold, the phase detection signal is phase-shifted. At this time, the phase detection signal and the current signal are out of phase, until the impedance angle is less than the set angle threshold, at which time the phase detection signal and the input impedance are in phase; the impedance tracking calculation tracks the phase at the maximum impedance in phase, rotates and maps the impedance coordinate system, and performs inverse transformation calculation on the impedance in the current coordinate system to obtain the original impedance size, that is, the internal resistance size, and finally uploads the data. The existing battery impedance measurement technology only uses fixed phase detection impedance, and a large error will be obtained when extracting low-proportion signals in the impedance. The set impedance can be rotated by moving the phase signal, and all information in the impedance can be extracted. Then, the original impedance is inferred by digital calculation, which makes full use of the reliability of analog circuits and the accuracy of digital calculations.

[0028] The excitation conditioning circuit sequentially drives, enhances, divides, and filters the analog sinusoidal signal generated by the main controller, and then transmits it to the AC current source circuit.

[0029] The AC current source circuit uses a high-power operational amplifier as the current output device for the excitation conditioning circuit signal, and adopts high-end differential current feedback to feed back the voltage through the sampling resistor to the positive and negative pins of the operational amplifier to close the output current loop. The circuit isolates the DC component and only passes the AC signal, and finally outputs the set positive and negative AC currents to the resonant coupling circuit.

[0030] refer to Figure 4 The existing technology for measuring battery internal resistance only supports single-cell battery voltage measurement, and low-voltage circuits cannot directly excite and measure 2500V batteries. The present invention proposes a resonant coupling circuit to expand the excitation and measurement range to high-voltage automotive battery packs and energy storage power station battery clusters, and supports internal resistance measurement during battery charging and discharging, which greatly improves the measurement range and has universal applicability. Planar magnetic cores and PCB coils are used as resonant inductors in the resonant coupling circuit, which improves processing consistency and measurement accuracy, and is conducive to large-scale production.

[0031] In the resonant coupling circuit, the current output by the AC current source circuit flows through the planar inductor, high-voltage large capacitor (polypropylene capacitor), fuse, and high-voltage battery of the car / energy storage power station in turn, and then flows back to the AC current source circuit to form a current loop. When the voltage of the high-voltage large capacitor is 0, a 2500V step voltage signal will be generated when the battery is connected. The high-frequency impedance of the capacitor is small and close to a short circuit. The high-frequency filtering characteristics of the inductor and the voltage clamping effect of the transient voltage suppression tube are used to limit the charging loop to the resonant coupling circuit. The inductor and the transient voltage suppression tube protect the AC current source circuit from the impact of high voltage and large current. After the capacitor is charged, the potential of the high-voltage large capacitor and the high-voltage battery is combined to 0V, and the AC current source circuit outputs AC current and can normally output excitation current to drive the high-voltage battery. The output range of the AC current source circuit is only 0-5V. The resonant coupling circuit can drive the low-voltage current to the high-voltage battery, solving the problem of complex acquisition and low precision of the circuit without high-voltage driving capability. The device uses the Kelvin four-wire method to avoid the influence of line resistance on the measurement results. The high-voltage battery is connected to two high-voltage capacitors to isolate the sampling and amplifier circuit on the low-voltage side from the battery DC voltage and only pass the AC signal. The high-voltage glass glaze resistor is responsible for limiting the charging current of the high-voltage capacitor to protect the sampling and amplifier circuit. The glass glaze resistor is connected to the sampling and amplifier circuit. Since the input impedance of the sampling and amplifier circuit is relatively high, a high-resistance glass glaze resistor is selected, resulting in the detection loop current being negligible.

[0032] Since high-voltage capacitors are used to connect both sides of the high-voltage battery, the current fluctuations during the battery charging and discharging process will be cut off by the high impedance composed of the planar inductor and the high-voltage large capacitor in the resonant coupling circuit. The voltage fluctuations during the charging and discharging process can be filtered out by the analog switch and the low-pass filter in the subsequent switching phase detection circuit. Therefore, this device can normally measure the battery internal resistance when the battery is in the charging and discharging state.

[0033] The sampling amplifier circuit uses the high common mode rejection ratio and high input impedance input characteristics to amplify the small AC signal. The response voltage generated by the high voltage battery under the excitation current is collected and amplified through the instrument amplifier. C6 is used to isolate the DC bias and only amplify the AC signal. The port protection circuit provides a charging loop when the high voltage capacitor is charged to protect the low voltage of the subsequent stage from being affected. The bias setting facilitates the output of positive signals in the subsequent stage to avoid negative cutoff distortion. Finally, the amplified battery AC voltage is input into the switch phase detection circuit.

[0034] refer to Figure 5 The amplified signal enters the switch phase detection circuit, passes through the gear switch, analog switch, low-pass filter, and finally enters the main controller. Suppose the gear switch output signal u in (t) is:

[0035]

[0036] Assume that the main controller outputs a square wave signal u ref (t) is:

[0037]

[0038] Analog switch equivalent multiplication operation u mul (t) = u in (t)×u ref (t), calculated as:

[0039]

[0040] u mul (t) is passed into the low-pass filter to obtain the approximate u out :

[0041]

[0042] Among them U m is the impedance amplitude of the battery under the response voltage, The phase difference between the response voltage and the output signal of the main controller. The analog switch device is used to simulate the multiplication operation, replacing the analog multiplier, which greatly reduces the design cost and the difficulty of reference signal generation, improves the design accuracy, and the principle is simple and practical, with a wide range of applications. After the analog switch output, it passes through a low-pass filter to filter out the high-order harmonics generated by the analog switch, and finally transmits the calculated impedance signal back to the main controller for subsequent digital operations.

[0043] Figure 6 This is the fitting diagram of the standard resistance measurement result of this device. The root mean square error (RMSE) reaches 0.1827 and the determination coefficient (R 2 ) is 0.99992, and the battery internal resistance measurement results are compared with those of 3.5V 18650 battery and 400V automobile battery measured by Hioki battery tester BT3564. The measurement accuracy of the present invention reaches ±1%rdg.±1dgt. Figure 7 This is a physical diagram of the present invention.

Claims

1. A high-voltage battery micro-internal resistance measurement device based on resonant coupling, characterized in that: It includes a main controller, an excitation conditioning circuit, an AC current source circuit, a resonant coupling circuit, a sampling amplifier circuit and a switch phase detection circuit; The main controller is connected to the excitation conditioning circuit through an analog output port, and is connected to the switch phase detection circuit through an analog input port and a digital output port. The excitation conditioning circuit is directly connected to the AC current source circuit, and the AC current source circuit is directly connected to the coupling circuit. The battery interface in the coupling circuit is connected to the sampling amplifier circuit after being isolated by a capacitor, and the sampling amplifier circuit is directly connected to the switch phase detection circuit.

2. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 1 is characterized in that: The main controller uses a single-chip microcomputer as a logic controller, and the controller has a built-in analog output port, which outputs an excitation analog signal with adjustable amplitude, phase, frequency and sampling rate, and transmits it to the excitation conditioning circuit; The main controller has a built-in analog input port. The switch phase detection circuit inputs the analog signal to the analog input port. The digital output port of the main controller controls the on and off of the analog switch of the switch phase detection circuit. The main controller uses interrupts to trigger analog input sampling and internal resistance calculation, and finally transmits the internal resistance data through the communication interface.

3. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 2 is characterized in that: The excitation conditioning circuit is connected to the excitation analog signal output by the main controller, performs driving capability amplification, filtering and amplitude conditioning on the excitation analog signal, and then transmits the excitation analog signal to the AC current source circuit.

4. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 3 is characterized in that: After receiving the excitation analog signal input, the AC current source circuit outputs the corresponding current through the power operational amplifier, uses differential current feedback to feed back the voltage through the sampling resistor to the positive and negative pins of the operational amplifier, and outputs positive and negative AC currents to the resonant coupling circuit.

5. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 4 is characterized in that: The resonant coupling circuit is responsible for connecting the battery and the measuring device, transmitting the positive and negative AC circuits output by the AC current source to the battery through the resonant coupling circuit, and then transmitting the response signal to the sampling and amplification circuit through the resonant coupling circuit; the input end of the planar inductor in the resonant coupling circuit is respectively connected to the AC current source circuit and the transient voltage suppression tube, and the output end is connected to the polypropylene capacitor; the input end of the polypropylene capacitor is connected to the planar inductor, and the output end is connected to the fuse; the input end of the fuse is connected to the polypropylene capacitor, and the output end is connected to the battery of the car / energy storage power station; The output end of the battery of the automobile / energy storage power station is respectively connected to the transient voltage suppression tube, the AC current source and the capacitor 1; the output of the capacitor 1 is connected to the glass glaze resistor 1, and the output of the glass glaze resistor 1 is connected to the sampling amplifier circuit; the output of the capacitor 2 is connected to the battery of the automobile / energy storage power station; the output of the glass glaze resistor 2 is connected to the capacitor 2, and the output of the sampling amplifier resistor is connected to the glass glaze resistor 2.

6. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 5 is characterized in that: In the sampling and amplifying circuit, the resonant coupling circuit transmits the voltage signal generated after the excitation current flows through the battery of the automobile / energy storage power station to the sampling and amplifying circuit for signal acquisition, amplification and biasing, and then transmits it to the switching phase detection circuit.

7. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 6 is characterized in that: The switch phase detection circuit generates an AC chopping signal by passing the battery AC voltage amplified by the sampling amplifier circuit through an analog switch. The signal is transmitted to the main controller through a low-pass filter. The analog switch control signal is generated by the main controller, and the switch phase detection circuit outputs the amplitude corresponding to the set phase.

8. The high-voltage battery micro-internal resistance measurement device based on resonant coupling according to claim 7 is characterized in that: The specific process of the main controller using interrupt triggering to calculate the internal resistance is as follows: When the main controller finds that the phase difference between the battery impedance and 0° is greater than the set angle threshold, the impedance tracking algorithm is used. The impedance tracking method is: initialize the phase detection signal to be in phase with the output current, call the impedance calculation interrupt to obtain the real part data of the phase detection signal, and then call the impedance calculation interrupt to obtain the imaginary part data under the phase detection signal, and use the real part and the imaginary part to estimate the impedance angle. When the angle is greater than the set angle threshold, the phase detection signal is phase-shifted. At this time, the phase detection signal is out of phase with the current signal until the impedance angle is less than the set angle threshold, at which time the phase detection signal is in phase with the input impedance; The impedance tracking calculation tracks the phase at the maximum value of the impedance in phase, rotates and maps the impedance coordinate system, and performs an inverse transformation calculation on the impedance in the current coordinate system to obtain the original impedance size, that is, the internal resistance size.

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