A lithium battery simulation system based on power operational amplifier

Abstract

This invention discloses a lithium battery simulation system and method based on a power operational amplifier. The system includes a digital control unit, a signal conversion unit, a power operational amplifier unit, and a current feedback unit. The digital control unit generates a control signal based on the target lithium battery model parameters and the real-time feedback load current, which is then converted into a voltage reference signal by the signal conversion unit. The power operational amplifier unit amplifies this signal and outputs a simulated lithium battery port voltage. The current feedback unit samples the actual load current and feeds it back, forming a closed loop. This invention uses a power operational amplifier as its core, combined with digital closed-loop control, to accurately and dynamically reproduce the nonlinear external characteristics and dynamic response of lithium batteries. It has the advantages of high flexibility, programmability, safety, reliability, and scalability with multiple channels, making it suitable for the research and development and testing of battery-related equipment.

Description

Technical Field

[0001] This invention relates to the field of battery testing and power electronics simulation technology, specifically to a lithium battery simulation system based on a power operational amplifier. Background Technology

[0002] In the research and testing of new energy, electric vehicles, energy storage systems, and portable electronic devices, lithium batteries are frequently used for functional verification, performance evaluation, and aging tests. However, directly using real lithium batteries has many limitations: high cost, safety risks (such as overcharging, over-discharging, and short circuits), difficulty in accurately repeating test conditions, uncontrollable battery states (such as SOC and SOH), and inability to simulate extreme or fault conditions.

[0003] To address these issues, battery simulators have emerged. Traditional battery simulators or DC power supplies typically use simple voltage sources or resistor networks for simulation, which struggle to accurately reproduce the complex external characteristics of lithium batteries, such as nonlinearity, time-varying nature, and state-of-charge (SOC) dependence. Especially under dynamic load conditions (such as electric vehicle acceleration and regenerative braking), their output response differs significantly from that of a real battery.

[0004] Power operational amplifiers (OPAs) possess high bandwidth, high output current capability, low output impedance, and good linearity, making them suitable as fast-adjustable power voltage sources. Combined with digital control technology, battery models can be solved in real time, and the output voltage can be dynamically adjusted, thereby simulating the electrical behavior of real batteries with high precision. Therefore, developing a programmable, high-dynamic-response, and high-precision lithium battery simulation system based on power OPAs has significant practical value. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a lithium battery simulation system based on a power operational amplifier.

[0006] To achieve the objective, the technical solution of the present invention is implemented as follows: a lithium battery simulation system based on a power operational amplifier, characterized in that it includes: a digital control unit, a signal conversion unit, a power operational amplifier unit, and a current feedback unit.

[0007] The digital control unit (DCU) is the core computing and control hub of the system. It has built-in or can receive mathematical model parameters of the target lithium battery (such as open-circuit voltage-state-of-charge curve, internal resistance-state-of-charge curve, capacity, etc.) and initial state. In real time, it receives the load current sampling value from the current feedback unit, performs calculations based on the battery model (e.g., equivalent circuit model), dynamically determines the theoretical port voltage value that should be output under the current simulated state and load conditions, and generates the corresponding digital control signal.

[0008] The signal conversion unit, connected to the digital control unit, is used to convert digital control signals into high-precision analog voltage reference signals. This unit is typically a digital-to-analog converter, and its resolution, linearity, and settling time directly affect the system's output accuracy and dynamic response speed.

[0009] The power operational amplifier unit, connected to the signal conversion unit, is used to perform voltage following, proportional amplification, and power amplification on the voltage reference signal to drive the load. It has extremely low output impedance, providing the required current and supplying a precisely controlled, analog lithium battery port voltage at its output. This unit typically includes a power operational amplifier chip and necessary peripheral circuitry (such as feedback networks, compensation networks, and heat dissipation devices).

[0010] The current feedback unit, connected between the output circuit of the power operational amplifier unit and the digital control unit, is used to sample the actual current flowing through the load with high precision. This sampled value is sent back to the digital control unit as a critical feedback quantity, forming a closed-loop control. Based on this real-time load current and the built-in battery model, the digital control unit updates the internally simulated battery state (such as SOC) and dynamically updates the control signal accordingly, thereby ensuring that the output voltage-current relationship of the entire system closely tracks the electrical characteristics of the target lithium battery.

[0011] Furthermore, the digital control unit is one of a microcontroller, digital signal processor, or field-programmable gate array, possessing sufficient computing power to run the battery model algorithm in real time.

[0012] Furthermore, the power operational amplifier unit includes one or more cascaded power operational amplifier circuits. Its feedback network is a resistor network connected between the output terminal and the inverting input terminal of the power operational amplifier, forming a voltage follower or non-inverting proportional amplifier topology to ensure that the output voltage accurately follows or proportionally amplifies the input reference voltage.

[0013] Furthermore, the feedback network may optionally include a digital potentiometer or an array of analog switches controlled by a digital control unit. The digital control unit can dynamically adjust the coefficients (i.e., amplification factor) of the feedback network based on the simulated changes in the battery's internal resistance, thereby enabling a rapid hardware-level response to changes in internal resistance and achieving a more precise simulation of the dynamic changes in the lithium battery's internal resistance.

[0014] Furthermore, the current feedback unit includes: a sampling resistor connected in series in the main circuit; a high-precision differential amplifier connected across the sampling resistor to amplify the small differential voltage signal across the sampling resistor; and an analog-to-digital converter to convert the amplified differential voltage signal into a digital current feedback signal and send it to the digital control unit.

[0015] Furthermore, the digital control unit incorporates preset protection logic. When the load current indicated by the feedback signal exceeds the preset overcurrent threshold, or the output port voltage exceeds the preset overvoltage / undervoltage threshold, the digital control unit immediately adjusts the digital control signal to a safe value (such as zero voltage), or cuts off the output by controlling the enable terminal of the power operational amplifier unit, thereby achieving overcurrent, overvoltage, and undervoltage protection functions to ensure the safety of the system and the device under test.

[0016] Furthermore, the system also includes a communication interface module, which connects to the digital control unit to receive battery simulation parameter commands from the host computer. These commands include, but are not limited to: the nominal voltage, capacity, initial state of charge (SOC), open-circuit voltage-SOC curve parameters, internal resistance-SOC curve parameters, and dynamic operating condition commands of the simulated battery. This allows the system to be flexibly configured to simulate virtual batteries of different models, states, and even custom characteristics.

[0017] Furthermore, the communication interface module can be one or more of Ethernet, CAN bus, USB or RS-485 interfaces to adapt to different application scenarios and communication needs.

[0018] Furthermore, the system can be expanded into a multi-channel architecture. It includes multiple output channels consisting of independent signal conversion units, power operational amplifier units, and current feedback units, all of which share the same digital control unit. The digital control unit can coordinate and control the various channels to simulate the series (output voltage superposition), parallel (output current superposition), or more complex array characteristics of individual cells in a lithium battery pack, supporting the testing of battery packs or battery systems.

[0019] The lithium battery simulation method based on the above system is characterized by the following steps: S1: System initialization, the digital control unit loads the default or received target lithium battery model parameters and initial state parameters (such as initial SOC) through the communication interface. S2: The digital control unit calculates the theoretical open-circuit voltage and internal resistance at the current moment according to the simulated lithium battery state and model, and combines the real-time received load current feedback signal to generate the target port voltage value to be output using the model formula (such as V_out = V_oc(SOC) - I_load * R_internal(SOC)). S3: The digital control unit converts the target port voltage value into a corresponding digital control signal, and generates an analog voltage reference signal through the signal conversion unit. S4: The power operational amplifier unit amplifies and tracks the analog voltage reference signal, and outputs the simulated lithium battery port voltage to the load. S5: The current feedback unit collects the actual load current in real time and converts it into a digital signal to feed back to the digital control unit. S6: The digital control unit updates the simulated internal state of the lithium battery (mainly SOC) based on the actual load current and the lithium battery model (e.g., through the ampere-hour integration method or more complex algorithms), and returns to step S2 to achieve closed-loop dynamic simulation. This loop runs at a very high frequency, thereby achieving rapid response to dynamic loads.

[0020] The beneficial effects of this invention are reflected in: High precision and high dynamic response: By using a power operational amplifier as the power output stage and combining it with high-speed digital closed-loop control, it can quickly and accurately track the output of the battery model and reproduce the real external characteristics of lithium batteries under static and dynamic loads.

[0021] Highly flexible and programmable: Through the digital control unit and communication interface, different battery models, parameters and initial states can be easily configured, and even non-standard or faulty batteries can be simulated to meet diverse testing needs.

[0022] Safe and reliable: It avoids the safety risks associated with using real batteries, and the system has multiple built-in software and hardware protection mechanisms to ensure the safety of the testing process.

[0023] Repeatability and economy: The test conditions can be accurately repeated and are not affected by factors such as battery aging and ambient temperature; the long-term use cost is far lower than that of consuming a large number of real batteries for testing.

[0024] Highly scalable: Supports multi-channel architecture, easy to expand for simulating battery packs, suitable for testing equipment such as BMS (Battery Management System) and energy storage converters. Attached Figure Description

[0025] In the attached diagram: Figure 1This is a block diagram of the overall structure of the lithium battery simulation system described in this invention.

[0026] Figure 2 This is a schematic diagram of a specific circuit for the power operational amplifier unit and adjustable feedback network in this invention.

[0027] Figure 3 This is a specific circuit diagram of the high-precision current sampling and feedback module in this invention.

[0028] Figure 4 This is a flowchart of the lithium battery simulation method described in this invention.

[0029] Figure 5 This is a schematic diagram of the multi-channel system architecture of the present invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, and not all of them. Unless otherwise specified, the embodiments and features described in this application can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0031] It should be noted that if the embodiments of the invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0032] Furthermore, "multiple" refers to two or more. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the invention.

[0033] See Figure 1 The lithium battery simulation system of the present invention mainly includes a digital control unit, a signal conversion unit, a power operational amplifier unit, and a current feedback unit.

[0034] The digital control unit can employ a high-performance STM32 series MCU or a TI DSP. It receives and stores battery model parameters (OCV-SOC lookup table, internal resistance parameters, rated capacity, etc.) from the host computer via a communication interface (such as USB). After the system powers on, the digital control unit loads the model and initial SOC from memory.

[0035] The signal conversion unit can use a 16-bit or higher precision DAC chip with a stable reference voltage. The digital control unit sends the calculated target voltage value (digital quantity) to the DAC via SPI or parallel bus, and the DAC outputs the corresponding analog voltage V_ref.

[0036] See Figure 2 The core of the power operational amplifier unit is a power operational amplifier chip, such as the PA107DP. The DAC output V_ref is connected to the non-inverting input of the op-amp. Resistors R1 and R2 form a basic non-inverting proportional amplifier feedback network, with a gain A_v = 1 + R2 / R1. The output voltage V_out = V_ref * A_v. To simulate internal resistance changes, R2 can be replaced with a digital potentiometer (such as the AD5270) controlled by the digital control unit via the I2C bus. The digital control unit adjusts the value of the digital potentiometer in real time based on the calculated current analog internal resistance, thereby fine-tuning the gain and making the system output characteristics more closely match the model. This unit requires sufficient heatsinking to handle power consumption during high current output.

[0037] See Figure 3 The current feedback unit uses a high-precision sampling resistor R_sense (such as a milliohm-level low-inductance resistor) connected in series between the negative output terminal of the power operational amplifier unit and the load ground. The voltage difference V_sense across the sampling resistor is equal to I_load * R_sense. This tiny voltage signal is amplified by a high-precision differential amplifier (such as INA188), and the amplified signal V_out_diff is sent to an ADC chip for analog-to-digital conversion. The converted digital current value is fed back to the digital control unit through an isolation device (such as a digital isolator), forming a current closed loop.

[0038] The operation flow of the digital control unit is as follows: Figure 4 As shown. After system initialization, the system enters the main loop. Within each control cycle (e.g., 100 microseconds): Read the current feedback value I_load.

[0039] Update the current SOC based on the SOC and I_load of the previous cycle (e.g., SOC(k) = SOC(k-1) - I_load * Δt / Capacity).

[0040] The current open-circuit voltage V_oc(SOC) and internal resistance R_int(SOC) can be obtained by looking up a table or by calculation based on SOC.

[0041] Calculate the target output voltage: V_target = V_oc(SOC) - I_load * R_int(SOC). Simultaneously, this V_target value is also used to compare with the actual output voltage sampled by the ADC, forming a voltage closed loop to eliminate power stage errors.

[0042] V_target is converted into DAC code and output to drive the power operational amplifier unit.

[0043] Check the protection conditions (e.g., |I_load|>I_max or V_out>V_max). If protection is triggered, immediately reset the DAC output to zero or disable the power op-amp.

[0044] For applications requiring simulated battery packs, the following can be used: Figure 5 The multi-channel architecture is shown. A master digital control unit manages multiple identical channels (each channel contains its own DAC, power op-amp, and current sampler). The control unit coordinates the output of each channel according to configurations such as series (each channel's voltage is independently controlled, but the current is the same) and parallel (each channel's voltage is the same, but the current is independently controlled and summed). This simulates the voltage superposition effect of a series battery pack or the current superposition effect of a parallel battery pack.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0047] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A lithium battery simulation system based on a power operational amplifier, characterized in that, include: Digital control unit, signal conversion unit, power operational amplifier unit, and current feedback unit; The digital control unit is used to generate control signals based on the model parameters of the target lithium battery and the real-time load current. The signal conversion unit is connected to the digital control unit and is used to convert the control signal into a voltage reference signal; The power operational amplifier unit is connected to the signal conversion unit and is used to amplify the voltage reference signal and provide an analog lithium battery port voltage at its output. The current feedback unit is connected between the output circuit of the power operational amplifier unit and the digital control unit, and is used to sample the load current of the output circuit and feed it back to the digital control unit. The digital control unit dynamically updates the control signal based on the feedback load current and the lithium battery model, so that the output voltage and current relationship of the power operational amplifier unit simulates the electrical characteristics of the target lithium battery.

2. The lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The digital controller is one of a microcontroller, a digital signal processor, or a field-programmable gate array.

3. The lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The power operational amplifier module includes one or more cascaded power operational amplifier circuits, and the feedback network is a resistor network connected between the output terminal and the inverting input terminal of the power operational amplifier, forming a voltage follower or non-inverting proportional amplifier topology.

4. A lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The feedback network includes a digital potentiometer or analog switch array controlled by the digital controller, which is used to dynamically adjust the feedback coefficient under the control of the digital controller to simulate the dynamic change of the internal resistance of the lithium battery.

5. A lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The high-precision current sampling and feedback module includes: The sampling resistor is connected in series in the main circuit; A high-precision differential amplifier connected across the sampling resistor is used to amplify the voltage difference signal across the sampling resistor. An analog-to-digital converter is used to convert the amplified differential pressure signal into a digital current feedback signal and send it to the digital controller.

6. A lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The digital controller has a preset protection logic. When the load current indicated by the feedback signal exceeds a preset overcurrent threshold or the output port voltage exceeds a preset overvoltage / undervoltage threshold, the digital controller immediately adjusts the digital control signal to a safe value, or cuts off the output by controlling the enable terminal of the power operational amplifier module, so as to realize the overcurrent, overvoltage and undervoltage protection functions.

7. A lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, It also includes a communication interface module, which is connected to the digital controller and is used to receive battery simulation parameter instructions from the host computer. The battery simulation parameter instructions include, but are not limited to: the nominal voltage, capacity, initial state of charge, open circuit voltage-state of charge curve parameters, internal resistance-state of charge curve parameters, and dynamic operating condition instructions of the simulated battery.

8. A lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The communication interface module is one or more of Ethernet, CAN bus, USB or RS-485 interface.

9. A lithium battery simulation system based on a power operational amplifier according to claim 1, characterized in that, The system is a multi-channel architecture, including multiple output channels consisting of independent digital-to-analog conversion modules, power operational amplifier modules, and current sampling and feedback modules. All channels share the same digital controller, which is used to simulate the series, parallel, or array characteristics of individual cells in a lithium battery pack.

10. A lithium battery simulation method based on the system according to any one of claims 1-9, characterized in that, Includes the following steps: S1: System initialization, the digital controller loads or receives the model parameters and initial state parameters of the target lithium battery through the communication interface; S2: The digital controller calculates the theoretical open-circuit voltage and internal resistance at the current moment based on the current simulated lithium battery state and model, and generates the target value of the port voltage to be output based on the received load current feedback signal. S3: The digital controller converts the target value of the port voltage into a digital control signal, and generates an analog voltage reference signal through the digital-to-analog converter module; S4: The power operational amplifier module amplifies and follows the analog voltage reference signal, and outputs an analog lithium battery port voltage to the load; S5: The high-precision current sampling and feedback module collects the actual load current in real time and feeds it back to the digital controller; S6: The digital controller updates the simulated internal state of the lithium battery based on the actual load current and the lithium battery model, and returns to step S2 to achieve closed-loop dynamic simulation.

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