Wave energy generation direct current micro-grid energy management method and system based on battery soc grading

Abstract

The application discloses a wave energy generation direct-current micro-grid energy management method and system based on battery SOC grading, relates to the technical field of grid energy management, and comprises the following steps: mapping the battery state of charge to a grading value through a continuous Sigmoid function; taking the grading value as an independent variable to calculate a discharge suppression factor, a charge suppression factor, a wave energy intermittence correction factor and an alternating-current load priority guarantee coefficient; generating battery charge and discharge power instructions and bus voltage control instructions according to the factors; and performing grid-connected power compensation and direct-current load switching control. The application realizes smooth adjustment of charge and discharge power, wave energy trend prediction response and priority guarantee of alternating-current load power supply, and can effectively suppress bus voltage fluctuation and prolong the service life of the battery.

Description

Technical Field

[0001] This invention relates to the field of power grid energy management technology, specifically to a method and system for energy management of wave energy-generating DC microgrids based on battery SOC grading. Background Technology

[0002] Wave energy-powered DC microgrids have become an important energy solution for island power supply, offshore platforms, and coastal areas. However, wave energy generation is characterized by significant intermittency, randomness, and volatility. The output power of wave energy generation devices changes in real time with sea conditions, leading to frequent fluctuations in DC bus voltage, which seriously affects the power quality and reliability of the microgrid. Currently, the industry generally uses battery energy storage systems to mitigate power fluctuations. Existing energy management strategies are mainly divided into two categories: one is a closed-loop control strategy based on DC bus voltage, which switches the system operating mode by detecting voltage drops or rises; the other is a zoned control strategy based on battery state of charge (SOC), which divides SOC into discrete intervals and uses different charging and discharging strategies for different intervals.

[0003] However, existing strategies generally have the following shortcomings: they fail to establish a quantitative guarantee mechanism for AC load power supply priority, and cannot ensure the power supply continuity of important AC loads when power is insufficient; they lack the ability to predict the trend of wave energy changes, and the control strategy only passively responds to power deviations, resulting in a delayed response; the bus voltage reference value is fixed at the rated value and is not coordinated with the battery SOC state, which exacerbates the risk of battery overcharging or over-discharging when the SOC is at an extreme value.

[0004] Therefore, there is a need for a wave energy power generation DC microgrid energy management method that can smoothly and continuously adjust charging and discharging power, has wave energy trend prediction capability, and ensures AC load priority. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a method and system for energy management of wave energy generation DC microgrids based on battery SOC grading.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The energy management method for wave energy-generating DC microgrids based on battery SOC grading includes the following steps: Step S1: Real-time acquisition of the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply of the AC load, and the rated reference power of the AC load. At the same time, based on historical power data, determine whether the current wave energy is in the rising or declining phase. Step S2: Based on the collected battery state of charge values, the values ​​are mapped to continuous graded values ​​between 0 and 1 using a continuous Sigmoid function. The continuous graded values ​​represent the location of the current state of charge in the graded system. Step S3: Using the continuous grading value as the independent variable, calculate the discharge suppression factor, charging suppression factor, wave energy intermittent correction factor, and AC load priority protection coefficient respectively; Step S4: Calculate the net power of the system based on the wave energy generation power, the actual power of the AC load and the DC load power. Combine the discharge suppression factor, the charging suppression factor, the AC load priority protection coefficient and the net power of the system to calculate the charging and discharging power command of the battery energy storage unit and issue it for execution. Step S5: Calculate the bus voltage correction amount based on the continuous grade value, perform adaptive correction on the rated DC bus voltage to obtain the adaptive bus voltage reference value, and then calculate the voltage control command of the bidirectional DC / DC converter based on the deviation between the actual bus voltage and the adaptive bus voltage reference value and issue it for execution. Step S6: Execute the graded power supply control of the grid-connected inverter and the graded switching control of the DC load according to the continuous graded values, and then wait for the next control cycle to return to step S1, forming a continuous energy management closed-loop control.

[0007] Further, in step S2, the continuous grading value is calculated as follows: using the natural constant e as the base, multiplying the negative grading steepness coefficient by the product of the difference between the state of charge value and the grading reference bias point as the exponent, calculating the exponential function value, and then dividing 1 by 1 and adding the sum of the exponential function values ​​to obtain the continuous grading value; wherein the grading steepness coefficient is used to control the sensitivity of the grading value to changes in the state of charge, and the grading reference bias point is the state of charge value corresponding to the continuous grading value being equal to 0.5; when the state of charge is 0, the continuous grading value approaches 0, and when the state of charge is 1, the continuous grading value approaches 1.

[0008] Further, in step S3, the discharge suppression factor is calculated as follows: using the natural constant e as the base, multiplying the negative discharge steepness coefficient by the difference between the continuous grading value and the discharge suppression grading threshold as the exponent, calculating the exponential function value, and then dividing 1 by 1 and adding the sum of the exponential function values ​​to obtain the discharge suppression factor. The charging inhibition factor is calculated as follows: with the natural constant e as the base, the exponential function value is calculated by multiplying the charging steepness coefficient by the difference between the continuous grade value and the charging inhibition grade threshold, and then 1 is divided by 1 and the sum of the exponential function values ​​is added to obtain the charging inhibition factor. The wave energy intermittent correction factor is calculated as follows: add 1 to the intermittent correction coefficient, multiply by the wave energy trend direction value, and then multiply by the continuous grade value to obtain the wave energy intermittent correction factor.

[0009] Furthermore, in step S3, the calculation of the AC load priority protection coefficient specifically includes the following steps: The power deviation ratio is obtained by dividing the difference between the AC load's rated reference power and the actual AC load power by the sum of the AC load's rated reference power and a small positive number to prevent the denominator from being zero. The hyperbolic tangent function value of this power deviation ratio is then multiplied by the adjustment gain and added to the reference priority coefficient to obtain the basic priority protection coefficient. When the actual AC load power is lower than the rated reference power, the basic priority protection coefficient is greater than the reference priority coefficient, and the priority of the AC load is increased. The basic priority protection coefficient is modulated using the continuous graded value and the wave energy intermittent correction factor. The basic priority protection coefficient is multiplied by the wave energy intermittent correction factor, then multiplied by 1, and the sum of the graded modulation coefficient multiplied by the continuous graded value is subtracted to obtain the final priority protection coefficient. The graded modulation coefficient is used to control the influence intensity of the continuous graded value on the final priority protection coefficient.

[0010] Furthermore, step S4 specifically includes the following steps: Step S4.1: Subtract the actual power of the AC load and then the power of the DC load from the wave energy generation power to obtain the net power of the system. A positive net power indicates a power surplus, while a negative net power indicates a power deficit. Step S4.2: Multiply the discharge suppression factor, the charge suppression factor, and the final priority guarantee coefficient together, then multiply by the system net power, and finally take the negative value to obtain the battery charge / discharge power command. A positive value of the battery charge / discharge power command indicates battery discharge, and a negative value indicates battery charging. When the system net power is positive, the battery charge / discharge power command is negative, and the battery is charging to absorb surplus power. When the system net power is negative, the battery charge / discharge power command is positive, and the battery is discharging to make up for the power deficit.

[0011] Furthermore, step S5 specifically includes the following steps: Step S5.1: Calculate the bus voltage correction based on the continuous graded values. Specifically, this includes: taking the hyperbolic tangent function value of the difference between the continuous graded values ​​and 0.5, multiplying it by the maximum voltage correction amplitude to obtain the bus voltage correction. The maximum voltage correction amplitude is set according to the rated voltage of the DC bus, and the unit is volts. When the continuous graded value is greater than 0.5, the bus voltage correction is positive; when the continuous graded value is less than 0.5, the bus voltage correction is negative. Step S5.2: Add the rated DC bus voltage to the bus voltage correction amount to obtain the adaptive bus voltage reference value; Step S5.3: Subtract the adaptive bus voltage reference value from the actual DC bus voltage collected to obtain the actual bus voltage deviation; Step S5.4: The obtained actual bus voltage deviation is sent to the PID controller. After PID calculation, a voltage control command for the bidirectional DC / DC converter is generated and issued for execution.

[0012] Further, in step S6, the graded power supply control of the grid-connected inverter specifically includes: when the continuous graded value is lower than the power supply start threshold, the grid-connected inverter is started to draw power from the AC grid to charge the battery; when the continuous graded value is higher than the power supply stop threshold, the grid-connected inverter is stopped; when the continuous graded value is greater than or equal to the power supply start threshold and less than the power supply stop threshold, the power supply decreases linearly as the continuous graded value increases; the power supply start threshold is less than the power supply stop threshold, and a hysteresis interval is formed between the power supply start threshold and the power supply stop threshold.

[0013] Further, in step S6, the graded switching control of the DC load specifically involves: when the continuous graded value is higher than the input threshold and the difference between the wave energy power generation and the actual power of the AC load is greater than the preset DC load input power threshold, the DC load is input to absorb excess power; when the continuous graded value is lower than the cut-off threshold, the DC load is cut off; the cut-off threshold is less than the input threshold, and a hysteresis interval is formed between the cut-off threshold and the input threshold.

[0014] A wave energy generation DC microgrid energy management system based on battery SOC grading, used to implement any one of the wave energy generation DC microgrid energy management methods based on battery SOC grading, including: The data acquisition unit is used to collect in real time the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply power and rated reference power of the AC load, and to determine whether the current wave energy is in the rising or declining phase based on historical power data. The SOC grading mapping unit is used to map the collected battery state of charge values ​​to continuous grading values ​​between 0 and 1 using a continuous Sigmoid function. The control factor calculation unit is used to calculate the discharge suppression factor, charging suppression factor, wave energy intermittent correction factor, and AC load priority protection coefficient with continuous grade values ​​as independent variables. The power command calculation unit is used to calculate the net power of the system based on the wave energy generation power, the actual power of the AC load and the DC load power, and to calculate the battery charging and discharging power command by comprehensively considering the discharge suppression factor, the charging suppression factor, the AC load priority protection coefficient and the net power of the system. The bus voltage control unit is used to calculate the bus voltage correction amount based on the continuous graded values, adaptively correct the rated DC bus voltage to obtain the adaptive bus voltage reference value, and calculate the voltage control command based on the deviation between the actual bus voltage and the adaptive bus voltage reference value. The graded switching control unit is used to perform graded power supply control of the grid-connected inverter and graded switching control of the DC load according to the continuous graded values.

[0015] An electronic device includes a processor and a memory, the memory storing a computer program that, when executed by the processor, causes the processor to perform any of the wave energy generation DC microgrid energy management methods based on battery SOC grading.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention maps the battery SOC to a continuous gradation value between 0 and 1 using a continuous Sigmoid function, replacing the traditional discrete step partitioning. This achieves continuous and smooth adjustment of charging and discharging power within the SOC range, eliminating control jumps and bus voltage oscillations at discrete gradation boundaries.

[0017] 2. This invention couples the wave energy change trend into the control strategy in advance through the wave energy intermittent correction factor, enabling the system to have predictive adjustment capabilities. Before the wave energy decays, it actively reduces the charging and absorption capacity, prioritizes the power supply to the load, and improves the stability of the DC bus voltage.

[0018] 3. This invention establishes a quantitative guarantee mechanism for AC load power supply priority by combining a basic priority coefficient with a graded modulation coefficient to form an AC load priority guarantee coefficient. When the AC load power supply is insufficient, power is allocated first, ensuring the power supply continuity of important AC loads.

[0019] 4. This invention adaptively corrects the bus voltage reference value through a hyperbolic tangent function based on the graded value, enabling the bus voltage control to respond in tandem with the SOC graded state. When the SOC is too high, the bus reference voltage is increased to induce discharge; when the SOC is too low, the bus reference voltage is decreased to induce charging, effectively suppressing battery overcharging and over-discharging and extending battery cycle life. Attached Figure Description

[0020] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart illustrating an embodiment of the present invention; Figure 2 This is a schematic diagram of the system architecture according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1As shown, the energy management method for wave energy generation DC microgrids based on battery SOC grading includes the following steps: Step S1: Real-time acquisition of the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply of the AC load, and the rated reference power of the AC load. At the same time, based on historical power data, determine whether the current wave energy is in the rising or declining phase. Step S2: Based on the collected battery state of charge values, the values ​​are mapped to continuous graded values ​​between 0 and 1 using a continuous Sigmoid function. The continuous graded values ​​represent the location of the current state of charge in the graded system. Step S3: Using the continuous grading value as the independent variable, calculate the discharge suppression factor, charging suppression factor, wave energy intermittent correction factor, and AC load priority protection coefficient respectively; Step S4: Calculate the net power of the system based on the wave energy generation power, the actual power of the AC load and the DC load power. Combine the discharge suppression factor, the charging suppression factor, the AC load priority protection coefficient and the net power of the system to calculate the charging and discharging power command of the battery energy storage unit and issue it for execution. Step S5: Calculate the bus voltage correction amount based on the continuous grade value, perform adaptive correction on the rated DC bus voltage to obtain the adaptive bus voltage reference value, and then calculate the voltage control command of the bidirectional DC / DC converter based on the deviation between the actual bus voltage and the adaptive bus voltage reference value and issue it for execution. Step S6: Execute the graded power supply control of the grid-connected inverter and the graded switching control of the DC load according to the continuous graded values, and then wait for the next control cycle to return to step S1, forming a continuous energy management closed-loop control.

[0023] After the system starts up and the communication link is established, the energy management controller collects the following data in real time through the communication network during each control cycle, including: the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply power and rated reference power of the AC load; at the same time, the energy management controller determines whether the current wave energy is in the rising or declining phase based on historical power data, and this determination is used for the calculation of the subsequent wave energy intermittent correction factor.

[0024] The energy management controller maps the collected SOC value to a continuous gradation between 0 and 1 using a continuous sigmoid function. The specific formula is as follows:

[0025] in, This represents a continuous gradation value, ranging from 0 to 1. This indicates the current SOC value of the battery, which is the percentage of remaining battery capacity. This represents the grading steepness coefficient, used to control the sensitivity of the grading value to changes in state of charge. It is set according to the battery type and is typically between 10 and 20. Indicates the grading reference bias point, i.e. The state of charge value corresponding to 0.5 is set according to the optimal operating range of the battery; in this embodiment, it is taken as 0.55. When it is 0 Approaching 0 corresponds to the lower-level region, when When it is 1 Approaching 1 corresponds to a higher-level region, when and When equal The value is 0.5, corresponding to the intermediate grading zone. It is continuously differentiable at any SOC value. By replacing the traditional discrete step partitioning with a continuous sigmoid function, a smooth and continuous mapping from SOC to step values ​​is achieved. The classification indicates which grade zone SOC is in, rather than the precise percentage of SOC.

[0026] After obtaining the grade value, the energy management controller uses the grade value as the independent variable to calculate four control factors in sequence. These are all dimensionless adjustment coefficients, which are only used for the numerical calculation of subsequent power commands. 1. Discharge suppression factor: When the State of Charge (SOC) is in the low-level region, the battery power is insufficient, and discharge behavior must be suppressed to prevent over-discharge. Traditional solutions directly prohibit discharge at the threshold, causing the discharge power to drop instantly from full capacity to 0. This invention uses the Sigmoid function to make the suppression process continuous and smooth. The formula for calculating the discharge suppression factor is:

[0027] in, This represents the discharge suppression factor, with a value ranging from 0 to 1, used to characterize the degree to which the current rating allows for acceptable battery discharge behavior. This represents the discharge steepness coefficient, used to control the transition rate of the discharge suppression factor near the threshold. It is set according to the system response speed requirements, and is usually taken as 15~25. This represents the discharge suppression grading threshold. When the grading value is lower than this threshold, the discharge will be suppressed. It is set according to the battery discharge depth safety boundary, and in this embodiment, it is set to 0.35. 2. Charging inhibition factor: When the State of Charge (SOC) is in the high-level region, the battery is fully charged, and charging behavior must be suppressed to prevent overcharging. This factor is opposite in direction to the discharging inhibition factor, together forming a two-way soft constraint on the battery's charging and discharging behavior. The formula for calculating the charging inhibition factor is:

[0028] in, This represents the charging inhibition factor, with a value ranging from 0 to 1, used to characterize the degree to which the current rating allows for battery charging behavior. This represents the charging steepness coefficient, used to control the transition speed of the charging inhibition factor near the threshold. It is set according to the system response speed requirements, and is usually taken as 15~25. This represents the charging suppression grading threshold. When the grading value is higher than this threshold, charging will be suppressed. It is set according to the upper limit safety boundary of battery charging, and in this embodiment, it is set to 0.70. In the intermediate grading zone At approximately 0.5~0.6, both the discharge inhibition factor and the charge inhibition factor are close to 1, and the battery's charge and discharge capabilities are not suppressed. In the low-level region, the discharge inhibition factor approaches 0, and discharge is suppressed. In the high-level region, the charge inhibition factor approaches 0, and charging is suppressed. The two work together to achieve graded but continuous control of the charge and discharge direction. 3. Wave Energy Intermittency Correction Factor: Wave energy generation exhibits significant intermittency. If the control strategy passively responds only to the current power deviation, the bus voltage will have already dropped when the power suddenly decreases significantly, resulting in a lag in response. This invention anticipates wave energy change trends and couples this trend information into the control factor, giving the control strategy predictive capabilities. The formula for calculating the wave energy intermittency correction factor is:

[0029] in, This indicates the wave energy intermittent correction factor. This represents the intermittent correction coefficient, used to control the intensity of the influence of wave energy trend direction on the control factor. It is set according to the wave energy fluctuation amplitude and is usually taken as 0.2~0.4. This value represents the trend direction of wave energy, determined by the energy management controller based on the power change trend within the most recent wave cycle. It is +1 when power is continuously rising and -1 when power is continuously falling. This value only indicates the sign and does not involve the specific power value. When wave energy is in an upward phase and... At higher levels, When the value is greater than 1, the control strategy enhances charging and absorption to utilize surplus energy; when wave energy is in its decay phase, If the value is less than 1, the control strategy tends to be conservative, reducing charging and consumption, and prioritizing power supply to existing loads. 4. AC Load Priority Protection Factor: To prioritize power supply to AC loads, it is necessary to quantify the AC load power deficit and adjust the power allocation priority accordingly. First, calculate the basic priority protection factor based on the power deviation. The specific formula is as follows:

[0030] in, This represents the basic priority guarantee coefficient. This represents the baseline priority coefficient, i.e., the default priority when there is no power deficit, and is set to 1.0. This represents the adjustment gain, used to control the adjustment range of the priority coefficient with power deficit; it is set to 0.5. Indicates the rated reference power of the AC load. The actual power supplied to the AC load is obtained from step S1. This indicates a small positive number to prevent the denominator from being zero. The unit is the same as the power supply capacity. ; The final priority protection coefficient is obtained by modulating the continuous grade value and the wave energy intermittent correction factor. The specific formula is as follows:

[0031] in, This indicates the final priority guarantee coefficient. This represents the graded modulation coefficient, used to control the influence of continuous graded values ​​on the final priority protection coefficient. It is set to 0~0.3. When in the low graded area, i.e. when power is scarce, the priority coefficient is slightly larger, and when in the high graded area, i.e. when power is abundant, the priority coefficient is slightly smaller. When the AC load power supply is insufficient, the battery power command is amplified to enhance discharge or weaken charging, forcing power to flow to the AC load first, so as to achieve the goal of prioritizing the AC load power supply.

[0032] Based on the calculated multiple control factors, these factors are integrated into a unified power command to achieve multi-objective coordinated control. First, the net power of the system is calculated, and the specific formula is as follows:

[0033] in, Indicates the system's net power. Indicates the power generation capacity of wave energy. Indicates the actual power of the AC load. Indicates DC load power. A value greater than 0 indicates a power surplus, while a value less than 0 indicates a power deficit. Then, the battery charging and discharging power command is calculated using the following formula:

[0034] in, This indicates the battery charging / discharging power command. A positive value indicates battery discharging, and a negative value indicates battery charging. It falls within the intermediate range. and Both are close to 1, allowing for free charging and discharging of the battery; in the lower grade region, Approaching 0, the discharge command is forcibly weakened; in the high-level region, Approaching 0, the charging command is forcibly weakened; When the AC load is insufficient, the discharge command is increased or the charging command is weakened, so that power flows preferentially to the AC load. Since all factors are... It is a continuous function, and the power command changes smoothly and continuously across the entire SOC range without any step jumps.

[0035] In traditional DC microgrids, the bus voltage reference value is fixed at the rated value. The battery-side DC / DC converter adjusts only based on the bus voltage deviation, without considering the State of Charge (SOC). Continuing to charge when the SOC is already high will overcharge the battery, and continuing to discharge when the SOC is already low will over-discharge it. This invention introduces a tiered value to correct the bus voltage reference value, enabling voltage control to respond collaboratively with the SOC tiered state. The energy management controller calculates the bus voltage correction amount based on the continuous tiered values, using the following formula:

[0036] in, This indicates the bus voltage correction amount. This indicates the maximum voltage correction range, which is set according to the rated voltage of the DC bus. It is usually ±5% of the rated bus voltage. In the high-level zone, the correction amount is positive, the bus reference voltage increases, and the battery discharges to maintain the voltage. In the low-level zone, the correction amount is negative, the bus reference voltage decreases, and the battery charges to increase the voltage. The formula for calculating the adaptive bus voltage reference value is as follows:

[0037] in, This represents the adaptive bus voltage reference value. This indicates the rated voltage of the DC bus, which is determined by the system's nominal value. The specific formula for calculating the actual bus voltage deviation is as follows:

[0038] in, This indicates the deviation between the actual bus voltage and the adaptive bus voltage reference value. This represents the actual DC bus voltage; After obtaining the actual bus voltage deviation, the energy management controller sends the deviation to the PID regulator. After PID calculation, the regulator generates a voltage control command for the bidirectional DC / DC converter and sends it out for execution. The local controller of the converter performs closed-loop voltage regulation to maintain the stability of the DC bus voltage.

[0039] The startup of the grid-connected inverter and the switching of the DC contactor are hardware switching actions. Frequent operations will severely shorten the equipment lifespan; therefore, a tiered value is still used. As a basis for decision-making, in order to maintain the consistency of the entire control strategy; Regarding the tiered power supply control of grid-connected inverters, the energy management controller executes the following control based on the continuous tiered values: When When the battery level is below the charging start threshold, the battery is in the low-level zone, indicating a severe power shortage. The grid-connected inverter is then activated to draw power from the AC grid to charge the battery. When the power supply exceeds the charging stop threshold, the grading value has risen to a higher grading zone, the power supply is restored, and the grid-connected inverter is stopped; when When the power supply is greater than or equal to the power supply start threshold and less than the power supply stop threshold, the power supply power increases accordingly. The charging mode increases continuously and then decreases linearly; the charging start threshold is less than the charging stop threshold, and the two form a hysteresis interval to prevent the charging mode from frequently starting and stopping at the boundary. Regarding DC load tiered switching control, the energy management controller executes the following control based on the continuous tiered values: when When the wave energy output exceeds the input threshold and the difference between the wave energy generation power and the actual AC load power is greater than the preset DC load input power threshold, the DC load is input to absorb the excess power; when When the load falls below the cut-off threshold, the DC load is cut off. The cut-off threshold is less than the connection threshold, and the two form a hysteresis interval to prevent the DC load from being frequently switched on and off at the boundary. After completing the above steps, the energy management controller waits for the next control cycle to arrive, returns to step S1 to re-collect data and update all calculated values. The above steps are executed cyclically during normal system operation, forming a continuous closed-loop control for energy management.

[0040] like Figure 2 As shown, the wave energy generation DC microgrid energy management system based on battery SOC grading is used to implement any of the wave energy generation DC microgrid energy management methods based on battery SOC grading, including: The data acquisition unit is used to collect in real time the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply power and rated reference power of the AC load, and to determine whether the current wave energy is in the rising or declining phase based on historical power data. The SOC grading mapping unit is used to map the collected battery state of charge values ​​to continuous grading values ​​between 0 and 1 using a continuous Sigmoid function. The control factor calculation unit is used to calculate the discharge suppression factor, charging suppression factor, wave energy intermittent correction factor, and AC load priority protection coefficient with continuous grade values ​​as independent variables. The power command calculation unit is used to calculate the net power of the system based on the wave energy generation power, the actual power of the AC load and the DC load power, and to calculate the battery charging and discharging power command by comprehensively considering the discharge suppression factor, the charging suppression factor, the AC load priority protection coefficient and the net power of the system. The bus voltage control unit is used to calculate the bus voltage correction amount based on the continuous graded values, adaptively correct the rated DC bus voltage to obtain the adaptive bus voltage reference value, and calculate the voltage control command of the bidirectional DC / DC converter based on the deviation between the actual bus voltage and the adaptive bus voltage reference value. The graded switching control unit is used to perform graded power supply control of the grid-connected inverter and graded switching control of the DC load according to the continuous graded values.

[0041] An electronic device includes a processor and a memory, the memory storing a computer program that, when executed by the processor, causes the processor to perform any of the wave energy generation DC microgrid energy management methods based on battery SOC grading.

[0042] Before system startup, the energy management controller establishes communication connections with each converter device and BMS. After confirming that all devices are communicating successfully and that the BMS is powered on normally, step S1 is executed.

[0043] The total power output of the wave energy generation unit is obtained by summing the output power of the 50kW AC / DC rectifier and the 100kW AC / DC rectifier. Both rectifiers adopt a three-phase PWM rectifier topology, and the AC power output from the wave energy generator is converted into DC power and fed into the DC bus through a dual closed-loop control of the voltage outer loop and the current inner loop. The rated voltage of the DC bus is 750V, and a bus capacitor is connected in parallel on the DC bus side to smooth high-frequency ripple. The battery energy storage unit consists of a lithium iron phosphate battery pack and a battery-side bidirectional DC / DC converter. The battery pack has a rated voltage of 600V and a capacity of 200Ah. The bidirectional DC / DC converter adopts an isolated CLLC resonant topology and operates in constant voltage or constant current mode. The charging and discharging current of the battery and the bus voltage are controlled by adjusting its duty cycle. The AC load is connected to the DC bus via a DC / AC off-grid inverter. The DC / AC off-grid inverter adopts a three-phase full-bridge inverter topology and outputs 380V / 50Hz AC power. The grid-connected inverter connects the DC bus to the AC grid. In supplementary power mode, it converts AC grid power into DC power to charge the battery, with a rated power of 30kW. DC loads are connected to the DC bus via DC contactors and serve as interruptible loads to absorb surplus power.

[0044] The energy management controller is an industrial-grade control computer equipped with LabVIEW real-time control software. It communicates with the bidirectional DC / DC converter via CAN bus, and with the 50kW AC / DC rectifier, 100kW AC / DC rectifier, DC / AC off-grid inverter, and grid-connected inverter via RS485 bus. It also communicates with the BMS via CAN bus. The BMS collects real-time data on individual battery cell voltages, total voltage, charging / discharging current, and temperature. It calculates the State of Charge (SOC) using the ampere-hour integration method and uploads this data to the energy management controller via CAN bus. Based on the calculation results from steps S1 to S6, the energy management controller sends power and voltage commands to the BMS and bidirectional DC / DC converter via CAN bus, and sends charging and switching commands to the grid-connected inverter and DC contactor, respectively. Each converter's local controller uses a DSP as its core processor, executing low-level PWM modulation and current / voltage closed-loop control with a control cycle of 100μs. The energy management controller's control cycle is 100ms; this separation in time scales ensures control stability.

[0045] After step S6 is completed, the energy management controller waits for the next 100ms control cycle, then returns to step S1 to re-acquire data and update all calculated values. These steps are executed in an infinite loop during normal system operation, forming a continuous closed-loop energy management control.

[0046] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. An energy management method for wave energy-generating DC microgrids based on battery SOC grading, characterized in that, Includes the following steps: Step S1: Real-time acquisition of the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply of the AC load, and the rated reference power of the AC load. At the same time, based on historical power data, determine whether the current wave energy is in the rising or declining phase. Step S2: Based on the collected battery state of charge values, the values ​​are mapped to continuous graded values ​​between 0 and 1 using a continuous Sigmoid function. The continuous graded values ​​represent the location of the current state of charge in the graded system. Step S3: Using the continuous grading value as the independent variable, calculate the discharge suppression factor, charging suppression factor, wave energy intermittent correction factor, and AC load priority protection coefficient respectively; Step S4: Calculate the net power of the system based on the wave energy generation power, the actual power of the AC load and the DC load power. Combine the discharge suppression factor, the charging suppression factor, the AC load priority protection coefficient and the net power of the system to calculate the charging and discharging power command of the battery energy storage unit and issue it for execution. Step S5: Calculate the bus voltage correction amount based on the continuous grade value, perform adaptive correction on the rated DC bus voltage to obtain the adaptive bus voltage reference value, and then calculate the voltage control command of the bidirectional DC / DC converter based on the deviation between the actual bus voltage and the adaptive bus voltage reference value and issue it for execution. Step S6: Execute the graded power supply control of the grid-connected inverter and the graded switching control of the DC load according to the continuous graded values, and then wait for the next control cycle to return to step S1, forming a continuous energy management closed-loop control.

2. The method according to claim 1, characterized in that, In step S2, the continuous grading value is calculated as follows: using the natural constant e as the base, the product of the negative grading steepness coefficient and the difference between the state of charge value and the grading reference bias point is used as the exponent to calculate the exponential function value. Then, 1 is divided by 1 and the sum of the exponential function values ​​is added to obtain the continuous grading value. The grading steepness coefficient is used to control the sensitivity of the grading value to changes in the state of charge. The grading reference bias point is the state of charge value corresponding to the continuous grading value being equal to 0.

5. When the state of charge is 0, the continuous grading value approaches 0, and when the state of charge is 1, the continuous grading value approaches 1.

3. The method according to claim 2, characterized in that, In step S3, the discharge suppression factor is calculated as follows: using the natural constant e as the base, multiplying the negative discharge steepness coefficient by the difference between the continuous grade value and the discharge suppression grade threshold as the exponent, the exponential function value is calculated, and then 1 is divided by 1 and the sum of the exponential function values ​​is added to obtain the discharge suppression factor. The charging inhibition factor is calculated as follows: with the natural constant e as the base, the exponential function value is calculated by multiplying the charging steepness coefficient by the difference between the continuous grade value and the charging inhibition grade threshold, and then 1 is divided by 1 and the sum of the exponential function values ​​is added to obtain the charging inhibition factor. The wave energy intermittent correction factor is calculated as follows: add 1 to the intermittent correction coefficient, multiply by the wave energy trend direction value, and then multiply by the continuous grade value to obtain the wave energy intermittent correction factor.

4. The method according to claim 3, characterized in that, In step S3, the calculation of the AC load priority protection coefficient specifically includes the following steps: The power deviation ratio is obtained by dividing the difference between the AC load's rated reference power and the actual AC load power by the sum of the AC load's rated reference power and a small positive number to prevent the denominator from being zero. The hyperbolic tangent function value of this power deviation ratio is then multiplied by the adjustment gain and added to the reference priority coefficient to obtain the basic priority protection coefficient. When the actual AC load power is lower than the rated reference power, the basic priority protection coefficient is greater than the reference priority coefficient, and the priority of the AC load is increased. The basic priority protection coefficient is modulated using the continuous graded value and the wave energy intermittent correction factor. The basic priority protection coefficient is multiplied by the wave energy intermittent correction factor, then multiplied by 1, and the sum of the graded modulation coefficient multiplied by the continuous graded value is subtracted to obtain the final priority protection coefficient. The graded modulation coefficient is used to control the influence intensity of the continuous graded value on the final priority protection coefficient.

5. The method according to claim 4, characterized in that, Step S4 specifically includes the following steps: Step S4.1: Subtract the actual power of the AC load and then the power of the DC load from the wave energy generation power to obtain the net power of the system. A positive net power indicates a power surplus, while a negative net power indicates a power deficit. Step S4.2: Multiply the discharge suppression factor, the charge suppression factor, and the final priority guarantee coefficient together, then multiply by the system net power, and finally take the negative value to obtain the battery charge / discharge power command. A positive value of the battery charge / discharge power command indicates battery discharge, and a negative value indicates battery charging. When the system net power is positive, the battery charge / discharge power command is negative, and the battery is charging to absorb surplus power. When the system net power is negative, the battery charge / discharge power command is positive, and the battery is discharging to make up for the power deficit.

6. The method according to claim 5, characterized in that, Step S5 specifically includes the following steps: Step S5.1: Calculate the bus voltage correction based on the continuous graded values. Specifically, this includes: taking the hyperbolic tangent function value of the difference between the continuous graded values ​​and 0.5, multiplying it by the maximum voltage correction amplitude to obtain the bus voltage correction. The maximum voltage correction amplitude is set according to the rated voltage of the DC bus, and the unit is volts. When the continuous graded value is greater than 0.5, the bus voltage correction is positive; when the continuous graded value is less than 0.5, the bus voltage correction is negative. Step S5.2: Add the rated DC bus voltage to the bus voltage correction amount to obtain the adaptive bus voltage reference value; Step S5.3: Subtract the adaptive bus voltage reference value from the actual DC bus voltage collected to obtain the actual bus voltage deviation; Step S5.4: The obtained actual bus voltage deviation is sent to the PID controller. After PID calculation, a voltage control command for the bidirectional DC / DC converter is generated and issued for execution.

7. The method according to claim 6, characterized in that, In step S6, the graded power supply control of the grid-connected inverter specifically includes: when the continuous graded value is lower than the power supply start threshold, the grid-connected inverter is started to draw power from the AC grid to charge the battery; when the continuous graded value is higher than the power supply stop threshold, the grid-connected inverter is stopped; when the continuous graded value is greater than or equal to the power supply start threshold and less than the power supply stop threshold, the power supply decreases linearly as the continuous graded value increases; the power supply start threshold is less than the power supply stop threshold, and the power supply start threshold and the power supply stop threshold constitute a hysteresis interval.

8. The method according to claim 7, characterized in that, In step S6, the graded switching control of the DC load is specifically as follows: when the continuous graded value is higher than the input threshold and the difference between the wave energy power generation and the actual power of the AC load is greater than the preset DC load input power threshold, the DC load is input to absorb the excess power; when the continuous graded value is lower than the cut-off threshold, the DC load is cut off; the cut-off threshold is less than the input threshold, and the cut-off threshold and the input threshold form a hysteresis interval.

9. A wave energy generation DC microgrid energy management system based on battery SOC grading, used to implement the wave energy generation DC microgrid energy management method based on battery SOC grading as described in any one of claims 1-8, characterized in that, include: The data acquisition unit is used to collect in real time the total power generation of the wave energy generation unit, the state of charge of the battery energy storage unit, the DC bus voltage, the DC load power, the actual power supply power and rated reference power of the AC load, and to determine whether the current wave energy is in the rising or declining phase based on historical power data. The SOC grading mapping unit is used to map the collected battery state of charge values ​​to continuous grading values ​​between 0 and 1 using a continuous Sigmoid function. The control factor calculation unit is used to calculate the discharge suppression factor, charging suppression factor, wave energy intermittent correction factor, and AC load priority protection coefficient with continuous grade values ​​as independent variables. The power command calculation unit is used to calculate the net power of the system based on the wave energy generation power, the actual power of the AC load and the DC load power, and to calculate the battery charging and discharging power command by comprehensively considering the discharge suppression factor, the charging suppression factor, the AC load priority protection coefficient and the net power of the system. The bus voltage control unit is used to calculate the bus voltage correction amount based on the continuous graded values, adaptively correct the rated DC bus voltage to obtain the adaptive bus voltage reference value, and calculate the voltage control command based on the deviation between the actual bus voltage and the adaptive bus voltage reference value. The graded switching control unit is used to perform graded power supply control of the grid-connected inverter and graded switching control of the DC load according to the continuous graded values.

10. An electronic device, characterized in that, It includes a processor and a memory, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the energy management method for wave energy generation DC microgrid based on battery SOC grading as described in any one of claims 1 to 8.

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