A hybrid power supply system power management method for a three-port converter

Abstract

The application belongs to the technical field of power electronics and new energy control, and particularly relates to a hybrid power supply system power control method for a three-port converter. The method comprises the following steps: S1, collecting a state of charge signal SOC of the battery unit in real time, and inputting the state of charge signal SOC into a low-power hysteresis comparator and a high-power hysteresis comparator respectively; S2, dynamically adjusting a battery charging power reference value and a bus voltage reference correction term according to a low-power interval identifier, a high-power interval identifier and a normal power interval identifier, and injecting the adjusted battery charging power reference value and the bus voltage reference correction term into a control loop in real time; and S3, constructing a first sub-control loop, a second sub-control loop and a third sub-control loop running in parallel in the control loop.

Description

Technical Field

[0001] This invention belongs to the field of power electronics and new energy control technology, specifically relating to a power management method for a hybrid power supply system using a three-port converter. Background Technology

[0002] Hybrid power supply systems (HPSS) consisting of fuel cells (FC) and batteries are a key solution for addressing the range and dynamic response issues in transportation electrification. HPSS based on three-port converters have attracted considerable attention due to their high integration and power density, but achieving reliable dynamic power distribution and coordinated control remains a significant technical challenge. Existing power distribution methods fail to adequately adapt to the significant differences in dynamic response time scales among different energy units. It is well known that fuel cells, constrained by complex chemical reaction mechanisms, exhibit significant high inertia and low-frequency response characteristics, making it difficult to match transient power surges on the load side. In contrast, lithium-ion batteries have higher power density and faster dynamic response capabilities, making them more suitable for handling high-frequency power components. However, existing distribution strategies generally lack effective frequency domain decoupling mechanisms. When faced with load step changes, they often force fuel cells and lithium batteries to respond synchronously across the entire frequency band, leading not only to fuel cell lifespan degradation risks but also to transient instability of the DC bus voltage due to dynamic source-load mismatch. Furthermore, when handling battery state of charge (SOC) exceeding limits, existing technologies typically employ hard-switching mode control based on logic judgments. This hard switching can cause the control loop to open, the integrator to saturate, and the bus voltage to oscillate transiently, which seriously affects the stability of the system and the power quality. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a power management method for a hybrid power supply system for a three-port converter, which solves the problems of source-end lifetime decay and bus voltage transient instability caused by the difference in dynamic response time scale between fuel cells and batteries in existing hybrid power supply systems.

[0004] The basic solution provided by this invention is a power control method for a hybrid power supply system using a three-port converter. The hybrid power supply system includes a fuel cell unit, a battery unit, a load unit, and a three-port converter connected between the fuel cell unit, the battery unit, and the load unit. The three-port converter includes a first switch, a second switch, a third switch, and a fourth switch. The power control method includes the following steps: S1. Real-time acquisition of the state of charge (SOC) signal of the battery unit, and inputting the SOC signal to the low charge hysteresis comparator and the high charge hysteresis comparator respectively to obtain the low charge range identifier, the high charge range identifier and the normal charge range identifier. S2. Based on the low power range indicator, high power range indicator, and normal power range indicator, dynamically adjust the battery charging power reference value and bus voltage reference correction item, and inject the adjusted battery charging power reference value and bus voltage reference correction item into the control loop in real time. S3. Construct a first sub-control loop, a second sub-control loop, and a third sub-control loop that operate in parallel within the control loop: The first sub-control loop is used to control the first switching transistor. Its voltage outer loop contains only an integral element so that the equivalent output impedance of the fuel cell unit is inductive, thereby responding only to the low-frequency components of the load. The second sub-control loop is used to control the second switching transistor. It adopts a constant power control strategy and adjusts the power of the fuel cell unit to charge the battery unit according to the battery charging power reference value. The third sub-control loop is used to control the third and fourth switching transistors, and introduces a first-order inertial element to simulate the parallel characteristics of resistors and capacitors, so that the battery unit can carry the high-frequency components of the load and maintain the stability of the bus voltage.

[0005] Furthermore, S1 includes the following steps: S11. The real-time acquired State of Charge (SOC) signal is input to a low-charge hysteresis comparator, which is set with a discharge cutoff threshold. and charging cutoff threshold And satisfy When the state of charge (SOC) signal drops below When the SOC rises to a level higher than the specified value, the output is high, indicating that the battery has entered a low-charge range. When the battery is low, the output level is low to indicate that the battery has exited the low battery range. S12. The real-time acquired State of Charge (SOC) signal is input to a high-charge hysteresis comparator, which is set with a forced discharge initiation threshold. and forced discharge exit threshold ,satisfy When the state of charge (SOC) signal rises above When the state of charge (SOC) signal drops below a certain level, the output is high, indicating that the battery has entered a high charge range. When the output is low and flat, it indicates that the high battery range has been exited. S13. Input the output results of S11 and S12 to the logic processing unit for AND, OR, and NOT operations. Only when the results are both low level is it marked as the normal power range.

[0006] Furthermore, S2 includes the following steps: S21. When the State of Charge (SOC) signal is detected to be within the normal charge range, the battery charging power reference value is set to zero. S22. When the State of Charge (SOC) signal is detected to be in the low charge range, the battery charging power reference value is set to a non-zero rated charging power value. S23. When the State of Charge (SOC) signal is detected to be in the high charge range, the battery charging power reference value is set to a negative value, and the battery-side reference voltage is increased to suppress the current reference value output by the fuel cell voltage loop.

[0007] Furthermore, the discharge cutoff threshold The charging cutoff threshold is set to 20%. The forced discharge initiation threshold is set to 50%. Set to 80%, forced discharge exit threshold Set to 50%.

[0008] Furthermore, in S3, the voltage outer loop transfer function of the first sub-control loop is: ,in The integral coefficient is used to make the equivalent output impedance of the fuel cell unit inductive in the frequency domain, so as to filter out the high-frequency components in the load current. The transfer function of the third sub-control loop includes a first-order inertial element. ,in This is the proportionality coefficient. The inertial time constant is used to simulate the impedance characteristics of a resistor and capacitor in parallel, so that the battery unit can actively absorb or release the high-frequency components in the load current.

[0009] Furthermore, the three-port converter also includes a first inductor, a first diode, a second diode, a second inductor, and a bus capacitor; The first inductor, the first switching transistor, the first diode, and the bus capacitor constitute the first boost circuit, which is connected between the fuel cell unit and the load unit. The first inductor, the first switch, the second switch, and the second diode constitute a second boost circuit, which is connected between the fuel cell unit and the battery unit. The first inductor and the first switch are multiplexed devices for the first boost circuit and the second boost circuit. The second inductor, the third switch, the fourth switch, and the bus capacitor form a bidirectional step-up / step-down circuit, which is connected between the battery unit and the load unit.

[0010] Furthermore, when the State of Charge (SOC) signal is detected to be in the low charge range, the first sub-control loop and the second sub-control loop work together to control the fuel cell unit to supply power to the load unit while charging the battery unit, and the third sub-control loop maintains the bus voltage stability.

[0011] Furthermore, when the State of Charge (SOC) signal is detected to be in the high charge range, the error signal in the first sub-control loop causes the duty cycle of the first switch to decrease naturally, and the system smoothly transitions to a mode where the battery unit supplies power to the load unit alone.

[0012] Furthermore, when the State of Charge (SOC) signal is detected to be within the normal charge range, the first sub-control loop and the third sub-control loop work together. The fuel cell unit bears the low-frequency component of the load current, and the battery unit bears the high-frequency component of the load current. The duty cycle of the second switching transistor naturally decreases to zero under closed-loop regulation.

[0013] The principles and advantages of this invention are as follows: This solution addresses the dynamic response mismatch and mode-switching oscillation issues in hybrid fuel cell and battery power supply systems by employing three parallel sub-control loops and a hysteresis comparator-based interval determination and parameter correction mechanism. In specific application scenarios, such as an electric bus equipped with both fuel cells and lithium batteries operating in urban areas, frequent starts, stops, accelerations, and decelerations cause significant fluctuations in load power. The solution first acquires the battery's state of charge (SOC) signal in real time and inputs it to low-charge and high-charge hysteresis comparators. By setting different cutoff and recovery thresholds, it identifies three charge intervals: low, high, and normal. When the battery charge is in the normal range, the system sets the battery charging power reference value to zero. Simultaneously, the first sub-loop in the control loop retains only the integral element, making the fuel cell's output impedance inductive in the frequency domain, and the fuel cell only responds to the slowly changing steady-state portion of the load current. The third sub-loop introduces a first-order inertial element to simulate the parallel characteristics of resistors and capacitors, making the battery port exhibit low impedance and actively absorbing or releasing high-frequency transient components in the load current. In this way, the initial impact power required for the vehicle to start at an intersection is quickly provided by the battery, while the fuel cell current rises steadily and slowly, avoiding gas shortages caused by delayed gas supply. When the battery charge drops to the low charge range, the system automatically adjusts the battery charging power reference value from zero to a non-zero rated charging power value. The first and second sub-loops work together, with the fuel cell charging the battery through the second switch while supplying power to the load, and the third sub-loop continuing to maintain stable bus voltage. When the battery charge rises to the high charge range, the battery charging power reference value is set to a negative value, raising the battery-side reference voltage. This reduces the voltage error signal in the first sub-loop, and the duty cycle of the first switch naturally decreases under closed-loop regulation. The fuel cell output power gradually decreases until it smoothly exits the range, and the system seamlessly transitions to a state where the battery supplies power to the load alone. The entire process does not involve any hard switching of control structures; all mode transitions are completed through parameter correction and closed-loop self-adjustment.

[0014] Compared with existing technologies, the advantages of this solution are reflected in three aspects.

[0015] 1. This solution effectively extends the lifespan of fuel cells. Existing distribution strategies lack a frequency domain decoupling mechanism, forcing the fuel cell and battery to respond synchronously to load changes across the entire frequency band. The fuel cell must withstand high-frequency dynamic overloads, leading to increased internal gas pressure fluctuations and alternating stress on the proton exchange membrane, resulting in significant performance degradation after long-term operation. This solution reshapes the output impedance of the fuel cell port through an integral stage, ensuring it tracks only the low-frequency components of the load. The rate of change in the fuel cell's output power is actively limited to a range that the chemical reaction can keep up with, fundamentally preventing gas shortage. The fuel cell's current waveform is smooth and glitch-free, significantly reducing the rate of lifespan degradation.

[0016] 2. This solution achieves seamless and smooth switching across the entire operating range. Existing technologies typically employ hard switching based on logic judgment when handling battery over-limit conditions. When an over-limit is detected, the control structure is directly altered or the drive pulse is blocked, causing the control loop to open instantaneously. The integrator enters saturation due to continuous error accumulation, inevitably leading to bus voltage overshoot and oscillation upon closing the loop. This solution maintains all sub-control loops in closed-loop operation at all times, adjusting the reference parameters of the injected loops only in real time based on the battery level range indicator. The control structure remains unchanged, the integrator always operates within the linear region, and the bus voltage fluctuation during mode transition is far less than that of the hard switching method, ensuring reliable power quality on the load side.

[0017] 3. This solution improves system integration at the hardware level through component reuse. In the three-port converter, the first inductor and the first switch simultaneously serve the boost circuit from the fuel cell to the load and the charging circuit from the fuel cell to the battery. The second inductor and the third and fourth switches form a bidirectional boost-buck circuit. Compared to the traditional solution using independent charging and boost modules, the number of power devices and the size of magnetic components are reduced, the system power density is improved, and the overall cost and size are more suitable for vehicle installation space requirements. In summary, this solution, through a control strategy combining frequency domain impedance reshaping and parameter adaptive soft switching, fundamentally solves the two major technical challenges of dynamic response mismatch and mode switching oscillation that have long existed in fuel cell hybrid power supply systems without increasing hardware complexity. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating the architecture and control block diagram of a hybrid power supply system based on a three-port converter, according to an embodiment of the present invention. Figure 2 This is a power distribution waveform diagram of the hybrid power supply system based on a three-port converter in an embodiment of the present invention, showing the load variation during the normal SOC power range. Figure 3 This is a power distribution waveform diagram of the hybrid power supply system based on a three-port converter in the low SOC range of this invention, showing the load variation. Figure 4 This is a power distribution waveform diagram of the hybrid power supply system based on a three-port converter in the high SOC range of this invention, showing the load variation. Figure 5 This is a power distribution waveform diagram of the load change when the hybrid power supply system based on a three-port converter switches between the normal and low power ranges of the SOC, according to an embodiment of the present invention. Figure 6 This is a power distribution waveform diagram of the load change when the hybrid power supply system based on a three-port converter switches between the normal and high power ranges of the SOC, according to an embodiment of the present invention. Detailed Implementation

[0019] The following detailed description illustrates the specific implementation method: The basic implementation examples are as follows: Figure 1 As shown: A hybrid power supply system architecture and power management method based on a three-port converter are disclosed. The system consists of a fuel cell unit, a battery unit, a load unit, and a three-port converter connecting the three. The fuel cell unit serves as the main power supply, the battery unit serves as an auxiliary energy storage unit, and the load unit represents the actual electrical equipment.

[0020] The hardware topology of the three-port converter is described below. The converter includes a first inductor L1, a first switch S1, a first diode D1, a second switch S2, a second diode D2, a second inductor L2, a third switch S3, a fourth switch S4, and a bus capacitor C2. The first terminal of the first inductor L1 is connected to the positive terminal of the fuel cell unit, and the second terminal of the first inductor L1 is connected to the drain of the first switch S1 and the anode of the first diode D1. The source of the first switch S1 is connected to the negative terminal of the fuel cell unit and system ground. The cathode of the first diode D1 is connected to the positive terminal of the bus capacitor C2 and the positive terminal of the load unit. The negative terminal of the bus capacitor C2 is connected to system ground. The first inductor L1, the first switch S1, the first diode D1, and the bus capacitor C2 together constitute a first boost circuit, which is connected between the fuel cell unit and the load unit to realize unidirectional boost power transmission from the fuel cell to the load.

[0021] Meanwhile, the second terminal of the first inductor L1 is also connected to the drain of the second switch S2, the source of the second switch S2 is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the positive terminal of the battery cell. The first inductor L1, the first switch S1, the second switch S2, and the second diode D2 together constitute the second boost circuit, which connects the fuel cell unit and the battery cell to achieve unidirectional charging power transfer from the fuel cell to the battery. It is important to note that the first inductor L1 and the first switch S1 appear simultaneously in both the first and second boost circuits; that is, these two devices are multiplexed by two power transmission paths. The first inductor L1 serves as both the energy storage inductor for boosting the fuel cell output to the load and the energy storage inductor for boosting the fuel cell to charge the battery. The first switch S1 serves as both the main control switch for regulating the load-side power and the main control switch for regulating the charging power. This device-multiplexed topology reduces the number of magnetic components and power semiconductor devices in the system, which helps to reduce the size of the converter and lower hardware costs.

[0022] Furthermore, the first terminal of the second inductor L2 is connected to the positive terminal of the battery cell, and the second terminal of the second inductor L2 is connected to the drain of the third switch S3 and the source of the fourth switch S4. The source of the third switch S3 is connected to system ground, and the drain of the fourth switch S4 is connected to the positive terminal of the bus capacitor C2. The second inductor L2, the third switch S3, the fourth switch S4, and the bus capacitor C2 together form a bidirectional buck-boost circuit, connected between the battery cell and the load cell. When power flows from the battery to the load, the third switch S3 acts as the main control switch, and the fourth switch S4 provides synchronous rectification; the circuit operates in boost mode. When power is fed back from the load side to the battery, for example, when the load motor is in regenerative braking mode, the fourth switch S4 acts as the main control switch, and the third switch S3 provides synchronous rectification; the circuit operates in buck mode. This bidirectional buck-boost circuit enables the battery to quickly absorb and dissipate high-frequency pulsating power from the load side while maintaining the stability of the DC bus voltage.

[0023] At the control architecture level, this embodiment constructs three parallel and complementary sub-control loops, namely the first sub-control loop, the second sub-control loop, and the third sub-control loop. Each sub-loop drives different switching transistors in the three-port converter.

[0024] The first sub-control loop is used to generate the drive pulse signal for the first switching transistor S1. This loop acquires the DC bus voltage signal and the fuel cell output current signal to form a voltage-current dual closed-loop structure, but its key feature is that the controller transfer function of the outer voltage loop only retains the integral element, specifically in the form of... ,in The integral coefficient is denoted as . When this transfer function is applied to the voltage regulation process at the fuel cell port, the equivalent output impedance of the fuel cell unit exhibits inductive characteristics, meaning the impedance amplitude increases with increasing frequency. For the slowly changing steady-state and low-frequency components of the load current, the inductive impedance is small, and the fuel cell can respond effectively and output the corresponding power. For the rapidly changing high-frequency transient components of the load current, the inductive impedance increases significantly, and the fuel cell output current hardly fluctuates.

[0025] The second sub-control loop generates the drive pulse signal for the second switch S2. This loop employs a constant power control strategy, with its input being the battery charging power reference value Pcharge. This reference value is not fixed but dynamically determined by the upper-level interval determination module based on the battery's real-time state of charge. The second sub-control loop divides the received charging power reference value by the current fuel cell output voltage to calculate the battery charging current reference value. It then adjusts the duty cycle of the second switch S2 through the current inner loop, thereby precisely controlling the charging power flowing from the fuel cell to the battery.

[0026] The third sub-control loop generates complementary drive pulse signals for the third switch S3 and the fourth switch S4. This loop acquires the DC bus voltage signal and the battery current signal to form a voltage-current dual closed-loop structure, but its voltage outer loop controller transfer function introduces a first-order inertial element, specifically in the form of… ,in This is the proportionality coefficient. The inertial time constant. Physically, this transfer function simulates the port impedance characteristics of a parallel resistor-capacitor network. When a positive step change occurs on the load side, causing a momentary drop in bus voltage, this inertial element causes the battery port to exhibit low impedance, allowing the battery to quickly release current to compensate for the power deficit. Similarly, when a negative step change occurs on the load side, causing a momentary rise in bus voltage, the battery port also exhibits low impedance.

[0027] Based on the three sub-control loops mentioned above, this embodiment introduces a hybrid power supply system architecture and power management method based on a three-port converter. The specific implementation process of the power control method is as follows: S1. Real-time acquisition of the state of charge (SOC) signal of the battery unit, and input of the SOC signal to the low charge hysteresis comparator and the high charge hysteresis comparator respectively to obtain the low charge range identifier, the high charge range identifier and the normal charge range identifier.

[0028] S11. Input the real-time acquired State of Charge (SOC) signal to the low-charge hysteresis comparator. The low-charge hysteresis comparator is set with a discharge cutoff threshold of 20% and a charge cutoff threshold of 50%, and satisfies the condition that the SOC discharge threshold is less than the SOC charge threshold. When the SOC signal drops below 20%, the low-charge hysteresis comparator outputs a high level, indicating that the low-charge range has been entered. When the SOC signal rises back above 50%, the low-charge hysteresis comparator outputs a low level, indicating that the low-charge range has been exited.

[0029] S12. Input the real-time acquired State of Charge (SOC) signal to the high-charge hysteresis comparator. The high-charge hysteresis comparator is set with a forced discharge start threshold of 80% SOC and a forced discharge exit threshold of 50% SOC, and the SOC exit threshold must be less than the SOC start threshold. When the SOC rises above 80%, the high-charge hysteresis comparator outputs a high level, indicating that the high-charge range has been entered. When the SOC falls below 50%, the high-charge hysteresis comparator outputs a low level, indicating that the high-charge range has been exited.

[0030] S13. Input the output results of steps S11 and S12 into the logic processing unit for AND, OR, and NOT operations. Only when the output results of the low-power hysteresis comparator and the high-power hysteresis comparator are both low, it is marked as the normal power range.

[0031] S2. Based on the low battery range indicator, high battery range indicator, and normal battery range indicator, dynamically adjust the battery charging power reference value and bus voltage reference correction item, and inject the adjusted battery charging power reference value and bus voltage reference correction item into the control loop in real time.

[0032] S21. When the State of Charge (SOC) signal is detected to be within the normal charge range, the battery charging power reference value is set to zero.

[0033] S22. When the State of Charge (SOC) signal is detected to be in the low charge range, the battery charging power reference value is set to a non-zero rated charging power value.

[0034] S23. When the State of Charge (SOC) signal is detected to be in the high charge range, the battery charging power reference value is set to a negative value, and the battery-side reference voltage is increased to suppress the current reference value output by the fuel cell voltage loop.

[0035] S3. Construct the first sub-control loop, the second sub-control loop, and the third sub-control loop to operate in parallel within the control loop.

[0036] Specifically, the battery's state of charge (SOC) signal is acquired in real time using either the current integration method or the open-circuit voltage method. This SOC signal is simultaneously fed into two parallel hysteresis comparators: a low-charge hysteresis comparator and a high-charge hysteresis comparator.

[0037] The low-charge hysteresis comparator internally sets two thresholds: a discharge cutoff threshold and a charge cutoff threshold. In this embodiment, the discharge cutoff threshold is set to 20%, and the charge cutoff threshold is set to 50%. There is a significant difference between these two thresholds; the discharge cutoff threshold is significantly lower than the charge cutoff threshold, thus forming a hysteresis range. When the battery's SOC gradually decreases below 20% due to continuous discharge, the output of the low-charge hysteresis comparator flips from a logic low level to a logic high level, indicating that the system has entered the low-charge range. Even if the SOC subsequently recovers slightly due to the start of charging, the comparator output remains high as long as it has not reached the 50% charge cutoff threshold. Only when the SOC continues to rise and eventually exceeds 50% does the comparator output reset from high to low, indicating that the system has exited the low-charge range. This hysteresis characteristic effectively prevents frequent jumps in the range indicator caused by small fluctuations in SOC near the critical value.

[0038] The high-charge hysteresis comparator also has two internal thresholds: a forced discharge start threshold and a forced discharge exit threshold. In this embodiment, the forced discharge start threshold is set to 80%, and the forced discharge exit threshold is set to 50%. When the battery's SOC gradually rises above 80% due to continuous charging, the output of the high-charge hysteresis comparator flips from logic low to logic high, indicating that the system has entered the high-charge range. Even if the SOC subsequently drops due to the start of discharge, as long as it does not fall below the 50% forced discharge exit threshold, the comparator output remains high. Only when the SOC continues to fall and eventually falls below 50% does the comparator output reset from high to low, indicating that the system has exited the high-charge range.

[0039] The output signals of the low-charge hysteresis comparator and the high-charge hysteresis comparator are fed into the logic processing unit for NOR logic operation. The logic processing unit outputs a logic high level only when both the low-charge interval marker and the high-charge interval marker are low, indicating that the system is in the normal charge range. When either the low-charge interval marker or the high-charge interval marker is high, the normal charge range markers are both low.

[0040] Based on the above interval determination results, the system dynamically adjusts two key parameters in real time: the battery charging power reference value Pcharge and the bus voltage reference correction term, and injects the updated parameters into the corresponding sub-control loop.

[0041] The following is in conjunction with the appendix Figures 2 to 6 The specific working process of the system under various typical operating conditions is described separately.

[0042] like Figure 2 As shown, when the battery's SOC is within the normal charge range, i.e., between 50% and 80%, the parameter adjustment logic sets the battery charging power reference value Pcharge to zero. After receiving the zero-power reference command, the output of its inner current loop naturally reduces the duty cycle of the second switch S2 to zero under closed-loop regulation, keeping the second switch continuously off and cutting off the charging path between the fuel cell and the battery. At this time, the first and third sub-control loops work together. The integral element of the first sub-control loop makes the fuel cell's equivalent output impedance inductive, and the fuel cell only responds to slowly changing low-frequency components in the load current, resulting in a smooth, glitch-free output power waveform. The first-order inertial element of the third sub-control loop makes the battery exhibit low impedance, allowing the battery to actively absorb or release abruptly changing high-frequency components in the load current. When the load power experiences a step increase, such as... Figure 2As shown in the waveform of the medium load power, the battery rapidly releases current to fill the power gap during sudden changes, while the fuel cell current gradually rises to a new steady-state value. When the load power drops sharply, the battery quickly absorbs the excess current, and the fuel cell current gradually decreases. Throughout the entire process, the DC bus voltage remains stable without significant drops or overshoots.

[0043] like Figure 3 As shown, when the battery's SOC drops below 20% due to prolonged discharge, the low-charge hysteresis comparator output flips to a high level, and the system enters the low-charge range. The parameter adjustment logic adjusts the battery charging power reference value Pcharge from zero to a non-zero rated charging power value. The first and second sub-control loops enter a cooperative working state. While the fuel cell supplies power to the load, it also delivers charging power to the battery through the second boost circuit. The constant power control strategy of the second sub-control loop ensures that the charging current is stable and controllable, avoiding additional impact on the fuel cell. The third sub-control loop continues to maintain a stable bus voltage. Figure 3 As can be seen from the power distribution waveform, the output power of the fuel cell is significantly higher than the load power in this range, and the difference between the two is the charging power flowing to the battery.

[0044] like Figure 4 As shown, when the battery's SOC rises above 80% due to prolonged charging, the high-charge hysteresis comparator output flips to a high level, and the system enters the high-charge range. The parameter adjustment logic sets the battery charging power reference value Pcharge to a negative value, while simultaneously adding a positive correction term to the bus voltage reference value of the third sub-control loop. The corrected equivalent reference voltage on the battery side is higher than the output voltage on the fuel cell side, thus reducing the voltage error signal of the first sub-control loop. The output duty cycle of the first sub-control loop naturally decreases under closed-loop regulation, the conduction time of the first switch S1 gradually shortens, and the output power of the fuel cell smoothly decreases until it completely exits the range. The system seamlessly transitions to a mode where the battery supplies power to the load alone. Figure 4 As can be seen from the power distribution waveform, the power of the fuel cell gradually decreases to zero, and the load power is entirely borne by the battery.

[0045] like Figure 5As shown in the figure, this illustrates the dynamic process of the system switching between the normal and low charge ranges. When the State of Charge (SOC) drops from above 20% to below 20%, the system transitions from the normal range to the low charge range. The battery charging power reference value Pcharge switches from zero to a non-zero rated value, and the second switch S2 begins operation, smoothly building up the charging power from zero. When the SOC recovers from below 50% to above 50%, the system exits the low charge range and returns to the normal range. Pcharge switches back from a non-zero value to zero, and the charging power smoothly decays to zero. Throughout the entire process, all sub-control loops maintain closed-loop operation, the control structure remains unchanged, and there is no significant oscillation in the bus voltage.

[0046] like Figure 6 As shown in the figure, this illustrates the dynamic process of the system switching between the normal charge range and the high charge range. When the State of Charge (SOC) rises from below 80% to above 80%, the system transitions from the normal range to the high charge range, Pcharge is set to a negative value, and a bus voltage reference correction term is applied, causing the fuel cell power to begin a smooth decrease. When the SOC falls from above 50% back to below 50%, the system exits the high charge range and returns to the normal range, the reference parameters are restored to the normal range setpoint, and the fuel cell power recovers smoothly. The entire switching process involves no changes to the control structure, and the power distribution curve is smooth and continuous.

[0047] Through the frequency domain decoupling design of the three sub-control loops and the parameter adaptive adjustment mechanism based on the hysteresis comparator, this embodiment successfully solves the problem of the mismatch between the dynamic response time scale of the fuel cell and the battery, avoids the fuel cell from being subjected to high-frequency overload, and eliminates the bus voltage oscillation problem caused by traditional hard switching control, thus realizing the stable and efficient operation of the system in the full operating range.

[0048] The above are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A power control method for a hybrid power supply system using a three-port converter, the hybrid power supply system comprising a fuel cell unit, a battery unit, a load unit, and a three-port converter connected between the fuel cell unit, the battery unit, and the load unit, the three-port converter comprising a first switch, a second switch, a third switch, and a fourth switch, characterized in that: The power control method includes the following steps: S1. Real-time acquisition of the state of charge (SOC) signal of the battery unit, and inputting the SOC signal to the low charge hysteresis comparator and the high charge hysteresis comparator respectively to obtain the low charge range identifier, the high charge range identifier and the normal charge range identifier. S2. Based on the low power range indicator, high power range indicator, and normal power range indicator, dynamically adjust the battery charging power reference value and bus voltage reference correction item, and inject the adjusted battery charging power reference value and bus voltage reference correction item into the control loop in real time. S3. Construct a first sub-control loop, a second sub-control loop, and a third sub-control loop that operate in parallel within the control loop: The first sub-control loop is used to control the first switching transistor. Its voltage outer loop contains only an integral element so that the equivalent output impedance of the fuel cell unit is inductive, thereby responding only to the low-frequency components of the load. The second sub-control loop is used to control the second switching transistor. It adopts a constant power control strategy and adjusts the power of the fuel cell unit to charge the battery unit according to the battery charging power reference value. The third sub-control loop is used to control the third and fourth switching transistors, and introduces a first-order inertial element to simulate the parallel characteristics of resistors and capacitors, so that the battery unit can carry the high-frequency components of the load and maintain the stability of the bus voltage.

2. The power control method for a hybrid power supply system for a three-port converter according to claim 1, characterized in that: S1 includes the following steps: S11. The real-time acquired State of Charge (SOC) signal is input to a low-charge hysteresis comparator, which is set with a discharge cutoff threshold. and charging cutoff threshold And satisfy When the state of charge (SOC) signal drops below When the SOC rises to a level higher than the specified value, the output is high, indicating that the battery has entered a low-charge range. When the battery is low, the output level is low to indicate that the battery has exited the low battery range. S12. The real-time acquired State of Charge (SOC) signal is input to a high-charge hysteresis comparator, which is set with a forced discharge initiation threshold. and forced discharge exit threshold ,satisfy When the state of charge (SOC) signal rises above When the state of charge (SOC) signal drops below a certain level, the output is high, indicating that the battery has entered a high charge range. When the output is low and flat, it indicates that the high battery range has been exited. S13. Input the output results of S11 and S12 to the logic processing unit for AND, OR, and NOT operations. Only when the results are both low level is it marked as the normal power range.

3. The power control method for a hybrid power supply system for a three-port converter according to claim 2, characterized in that: S2 includes the following steps: S21. When the State of Charge (SOC) signal is detected to be within the normal charge range, the battery charging power reference value is set to zero. S22. When the State of Charge (SOC) signal is detected to be in the low charge range, the battery charging power reference value is set to a non-zero rated charging power value. S23. When the State of Charge (SOC) signal is detected to be in the high charge range, the battery charging power reference value is set to a negative value, and the battery-side reference voltage is increased to suppress the current reference value output by the fuel cell voltage loop.

4. The power control method for a hybrid power supply system for a three-port converter according to claim 3, characterized in that: The discharge cutoff threshold The charging cutoff threshold is set to 20%. The forced discharge initiation threshold is set to 50%. Set to 80%, forced discharge exit threshold Set to 50%.

5. The power control method for a hybrid power supply system for a three-port converter according to claim 1, characterized in that: In S3, the voltage outer loop transfer function of the first sub-control loop is: ,in The integral coefficient is used to make the equivalent output impedance of the fuel cell unit inductive in the frequency domain, so as to filter out the high-frequency components in the load current. The transfer function of the third sub-control loop includes a first-order inertial element. ,in This is the proportionality coefficient. The inertial time constant is used to simulate the impedance characteristics of a resistor and capacitor in parallel, so that the battery unit can actively absorb or release the high-frequency components in the load current.

6. A power control method for a hybrid power supply system for a three-port converter according to claim 5, characterized in that: The three-port converter also includes a first inductor, a first diode, a second diode, a second inductor, and a bus capacitor; The first inductor, the first switching transistor, the first diode, and the bus capacitor constitute the first boost circuit, which is connected between the fuel cell unit and the load unit. The first inductor, the first switch, the second switch, and the second diode constitute a second boost circuit, which is connected between the fuel cell unit and the battery unit. The first inductor and the first switch are multiplexed devices for the first boost circuit and the second boost circuit. The second inductor, the third switch, the fourth switch, and the bus capacitor form a bidirectional step-up / step-down circuit, which is connected between the battery unit and the load unit.

7. A power control method for a hybrid power supply system for a three-port converter according to claim 6, characterized in that: When the State of Charge (SOC) signal is detected to be in the low charge range, the first sub-control loop and the second sub-control loop work together to control the fuel cell unit to supply power to the load unit and charge the battery unit at the same time, while the third sub-control loop maintains the bus voltage stability.

8. A power control method for a hybrid power supply system for a three-port converter according to claim 6, characterized in that: When the State of Charge (SOC) signal is detected to be in the high charge range, the error signal in the first sub-control loop causes the duty cycle of the first switch to decrease naturally, and the system smoothly transitions to a mode where the battery unit supplies power to the load unit alone.

9. A power control method for a hybrid power supply system for a three-port converter according to claim 6, characterized in that: When the State of Charge (SOC) signal is detected to be within the normal charge range, the first sub-control loop and the third sub-control loop work together. The fuel cell unit bears the low-frequency component of the load current, and the battery unit bears the high-frequency component of the load current. The duty cycle of the second switching transistor naturally decreases to zero under closed-loop regulation.

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