Energy efficiency optimization method and system of a wind-solar power generation hydrogen production system

Abstract

The application relates to the technical field of hydrogen production system energy efficiency optimization, and discloses an energy efficiency optimization method and system of a wind-solar power generation hydrogen production system. The three-step cooperative strategy of first adjusting a rectifier transformer tap to make an actual operation load rate enter an economic operation interval, recording a secondary side actual output voltage value as a voltage reference, then determining an electrolytic cell switching scheme by taking the voltage reference as a constraint, and finally checking the rectifier transformer load rate after switching and correcting the electrolytic cell load distribution when deviation occurs, enables the wind-solar power generation hydrogen production system to track wind-solar fluctuations while keeping the rectifier transformer in a low-loss state at all times, thereby improving the electric energy conversion efficiency of the wind-solar power generation hydrogen production system.

Description

Technical Field

[0001] This application relates to the technical field of energy efficiency optimization of hydrogen production systems, and in particular to a method and system for energy efficiency optimization of a wind and solar power hydrogen production system. Background Technology

[0002] With the accelerated global energy structure transformation, using renewable energy sources such as wind and solar power for water electrolysis to produce hydrogen has become a key pathway to achieving carbon neutrality. Wind-solar power-to-hydrogen systems couple fluctuating renewable energy with water electrolysis equipment, enabling large-scale green hydrogen production while also providing an effective way to localize renewable energy consumption. In this system, the renewable energy generation unit and energy storage unit are connected to the electrolyzer array via an AC bus, rectifier transformer, and IGBT rectifier power supply cabinet, forming a complete power conversion and hydrogen production chain. However, due to the inherent randomness, intermittency, and volatility of wind and solar power generation, maintaining efficient and stable operation of the hydrogen production system under significant fluctuations in wind and solar power output has become a core engineering problem restricting the large-scale promotion of this technology.

[0003] Existing technologies generally focus on the start-up and shutdown strategies and load allocation optimization of electrolyzer clusters. For example, related patents propose cluster optimization scheduling strategies based on differences in hydrogen production efficiency, load limits, single-unit rated capacity, start-up and shutdown frequency, and response characteristics of each unit in a hybrid electrolyzer. Other solutions aim to maximize economic benefits or system hydrogen production, establishing objective functions and constraint models for wind and solar power output, hydrogen production, hydrogen storage, and energy storage, and using solvers for optimization. These methods improve the adaptability of hydrogen production systems under wind and solar power fluctuations to some extent, but they all focus on power allocation optimization at the electrolyzer level, neglecting the energy efficiency coordination of two key links in the hydrogen production power supply chain: first, whether the rectifier transformer, as the power conversion hub, operates within the economically lowest-loss range; and second, how the IGBT rectifier power supply cabinet maintains efficient conversion under fluctuating input voltage. Existing technologies often treat rectifier transformer voltage regulation and electrolyzer switching as two independent problems, failing to establish a coordinated optimization mechanism from the rectifier transformer operating point to the electrolyzer load allocation. Summary of the Invention

[0004] Therefore, the purpose of this application is to overcome the technical defects in existing wind and solar power hydrogen production systems, which result in the disconnect between rectifier transformer energy efficiency optimization and electrolyzer load scheduling, leading to low power supply link efficiency when dealing with wind and solar fluctuations. This application provides an energy efficiency optimization method and system for wind and solar power hydrogen production systems. The method involves first adjusting the rectifier transformer taps to bring the actual operating load rate into the economic operating range and recording the actual output voltage value of the secondary side as a voltage reference. Then, using this voltage reference as a constraint, the electrolyzer switching scheme is determined. Finally, after switching, the rectifier transformer load rate is verified, and the electrolyzer load allocation is corrected when it deviates. This three-step coordinated strategy ensures that the wind and solar power hydrogen production system keeps the rectifier transformer in a low-loss state while tracking wind and solar fluctuations, thereby improving the power conversion efficiency of the wind and solar power hydrogen production system.

[0005] To address the aforementioned technical problems, this invention discloses, on the one hand, an energy efficiency optimization method for a wind-solar power generation hydrogen production system, comprising: When the real-time power factor of the AC bus is within the target power factor threshold, the tap position of the rectifier transformer is adjusted according to the economic operating load rate range of the rectifier transformer under the current actual load, so that the actual operating load rate of the rectifier transformer enters the economic operating load rate range, and the actual output voltage value of the secondary side of the rectifier transformer is recorded. Based on the total available power supply and the actual output voltage of the secondary side, the operation plan of the electrolytic cell array is determined, and the switching command is issued to the electrolytic cell array according to the operation plan; After the electrolytic cell array executes the switching command, the relationship between the actual operating load rate after switching and the economic operating load rate range is compared: When the actual operating load rate after the switch-off deviates from the economic operating load rate range, a load adjustment command is sent to the electrolytic cell array to adjust the load allocation value of each electrolytic cell put into operation, so that the actual operating load rate after the switch-off returns to the economic operating load rate range.

[0006] Preferably, the energy efficiency optimization method further includes: When the real-time power factor of the AC bus is less than the target power factor threshold, the first-level topology AC / DC module of the IGBT rectifier power supply cabinet is started to output the first capacitive reactive power to the AC bus until the real-time power factor rises to within the target power factor threshold. When the real-time power factor of the AC bus is greater than the target power factor threshold, the first-level topology AC / DC module of the IGBT rectifier power supply cabinet is started to output the first inductive reactive power to the AC bus until the real-time power factor is reduced to within the target power factor threshold.

[0007] Preferably, the method for determining the economic operating load rate range includes: When the real-time power factor of the AC bus is within the target power factor threshold, the economic operating load rate range of the rectifier transformer under the current actual load is determined based on the real-time load loss, rated copper loss and rated iron loss of the rectifier transformer. The method for determining the total available power supply includes: taking the sum of the actual power generation of the new energy power generation unit of the wind and solar power hydrogen production system and the current discharge capacity of the energy storage unit as the total available power supply.

[0008] Preferably, the method for adjusting the tap position of the rectifier transformer includes: When the actual operating load rate is lower than the lower limit of the economic operating load rate range and the on-load tap changer has not reached the highest position, the on-load tap changer of the rectifier transformer is raised by one position, and the raising step is repeated until the actual operating load rate of the rectifier transformer enters the economic operating load rate range. When the actual operating load rate is higher than the upper limit of the economic operating load rate range, and the on-load tap changer has not reached the lowest position, the on-load tap changer of the rectifier transformer is lowered by one position, and the down-slotting step is repeated until the actual operating load rate of the rectifier transformer enters the economic operating load rate range. If the tap position has reached the boundary position but still cannot bring the actual operating load rate into the economic operating load rate range, then maintain the boundary position operation.

[0009] Preferably, the operation plan includes: the total number of electrolytic cells put into operation and the load allocation value for each electrolytic cell put into operation; The constraints of the operation plan include: the sum of the load distribution values ​​of each electrolytic cell put into operation does not exceed the total available power supply; and the sum of the load distribution values ​​of each electrolytic cell put into operation does not exceed the maximum output DC power of the IGBT rectifier power supply cabinet corresponding to the actual output voltage value of the secondary side.

[0010] Preferably, adjusting the load distribution value of each electrolytic cell put into operation includes: If the actual operating load rate after the switch is lower than the lower limit of the economic operating load rate range, the load allocation value of the electrolytic cells already in operation will be increased to the rated load first; if the actual operating load rate after the switch is still lower than the lower limit of the economic operating load rate range after all the electrolytic cells in operation have reached the rated load, the electrolytic cells not yet in operation will be started, and the newly started electrolytic cells will be put into operation at the minimum operating load, and then gradually loaded. If the actual operating load rate after switching is higher than the upper limit of the economic operating load rate range, the load allocation value of the electrolytic cell with the lowest efficiency will be gradually reduced. Once the load allocation value of the electrolytic cell drops to the minimum operating load, the electrolytic cell will be disconnected.

[0011] Preferably, the constraints for adjusting the load distribution value of each electrolytic cell put into operation include: The sum of the adjusted load distribution values ​​for each electrolytic cell put into operation shall not exceed the total available power supply. The sum of the load distribution values ​​of each electrolytic cell put into operation after adjustment shall not exceed the maximum output DC power of the IGBT rectifier power supply cabinet corresponding to the actual output voltage value of the secondary side.

[0012] Preferably, the energy efficiency optimization method further includes: When the actual operating load rate after the switching does not deviate from the economic operating load rate range, the voltage deviation between the real-time voltage value of the AC bus and the actual output voltage value of the secondary side is obtained. When the absolute value of the voltage deviation exceeds the allowable deviation value, the reactive power output of the primary topology AC / DC module of the IGBT rectifier power supply cabinet to the AC bus is adjusted so that the real-time voltage value approaches the actual output voltage value of the secondary side, until the absolute value of the voltage deviation falls back to within the allowable deviation value. During the adjustment of the reactive power, the DC current output from the IGBT rectifier power supply cabinet to the electrolytic cell array is kept constant.

[0013] Preferably, adjusting the reactive power output from the primary topology AC / DC module of the IGBT rectifier power supply cabinet to the AC bus includes: When the real-time voltage value is higher than the actual output voltage value of the secondary side and the absolute value of the voltage deviation exceeds the allowable deviation value, the primary topology AC / DC module of the IGBT rectifier power supply cabinet outputs the second inductive reactive power to the AC bus. When the real-time voltage value is lower than the actual output voltage value of the secondary side and the absolute value of the voltage deviation exceeds the allowable deviation value, the primary topology AC / DC module of the IGBT rectifier power supply cabinet outputs a second capacitive reactive power to the AC bus.

[0014] On the other hand, the present invention provides an energy efficiency optimization system for a wind and solar power generation hydrogen production system. The wind and solar power generation hydrogen production system includes a new energy power generation unit, an energy storage unit, a rectifier transformer, an IGBT rectifier power supply cabinet, and an electrolyzer array. The new energy power generation unit and the energy storage unit are electrically connected to the electrolyzer array in sequence via an AC bus through the rectifier transformer and the IGBT rectifier power supply cabinet. The energy efficiency optimization system includes a system energy management center, which is configured to execute the steps of the energy efficiency optimization method for the wind and solar power generation hydrogen production system.

[0015] The above-described technical solution of this application has the following advantages over the prior art: The energy efficiency optimization method and system for wind and solar power generation hydrogen production systems described in this application employ a three-step coordinated strategy: first, adjusting the tap changer of the rectifier transformer to bring the actual operating load rate into the economic operating range and recording the actual output voltage value of the secondary side as a voltage reference; then, determining the electrolyzer switching scheme based on the voltage reference; and finally, verifying the rectifier transformer load rate after switching and correcting the electrolyzer load distribution when it deviates. This ensures that the wind and solar power generation hydrogen production system keeps the rectifier transformer in a low-loss state while tracking wind and solar fluctuations, thereby improving the power conversion efficiency of the wind and solar power generation hydrogen production system.

[0016] Specifically, the losses of a rectifier transformer include iron losses and copper losses. The overall loss varies parabolically with the load rate: when the load rate is too low, iron losses dominate the total loss; when the load rate is too high, copper losses increase sharply. The total loss is lowest only within a specific economic operating load rate range. By adjusting the tap position to change the turns ratio and secondary output voltage, the impedance matching state of the rectifier transformer under the current load can be altered, guiding the actual operating load rate closer to the point of lowest loss. Simultaneously, this ensures that the subsequent IGBT rectifier power supply cabinet operates within its optimal operating voltage range, effectively reducing the rectifier transformer's own losses.

[0017] Furthermore, by using the voltage output capacity of the rectifier transformer as a hard constraint for the load distribution of the electrolytic cell, the switching scheme is not only feasible in terms of power balance, but also feasible in terms of voltage matching. This avoids the engineering disconnect problem caused by focusing only on power balance and ignoring the actual output capacity of the rectifier cabinet in the traditional scheme.

[0018] Meanwhile, due to differences in the efficiency of each electrolyzer, varying rates of load increase and decrease, and inconsistent initial conditions, the actual load on the rectifier transformer after switching may deviate from its economic range. This application employs a mechanism for immediate verification and timely correction after switching to ensure that the hydrogen production system, during the electrolyzer switching process in accordance with wind and solar power fluctuations, always keeps the rectifier transformer's operating state within its economically low-loss range, thereby reducing AC power consumption in hydrogen production and improving the overall energy efficiency of the hydrogen production power supply system. Attached Figure Description

[0019] To make the content of this application easier to understand, the following detailed description is provided based on specific embodiments of this application and in conjunction with the accompanying drawings.

[0020] Figure 1 This is a schematic flowchart of an energy efficiency optimization method for a wind and solar power hydrogen production system in this application.

[0021] Figure 2 This is another schematic diagram of the energy efficiency optimization method for the wind and solar power hydrogen production system in the embodiments of this application.

[0022] Figure 3 This is a flowchart illustrating an energy efficiency optimization method after the switching command is executed in the electrolytic cell array, as described in this application embodiment.

[0023] Figure 4 This is a schematic diagram of the energy efficiency optimization system of the wind and solar power hydrogen production system in the embodiments of this application. Detailed Implementation

[0024] The present application will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present application, but the embodiments are not intended to limit the present application.

[0025] Traditional wind and solar power hydrogen production systems face challenges in system operating efficiency and stability when dealing with fluctuations in wind and solar power output. Existing methods focus on the start-up and shutdown of the electrolyzer cluster and load distribution, but fail to effectively coordinate the economic operating load rate of the rectifier transformer with the conversion efficiency of the IGBT rectifier power supply cabinet, resulting in independent voltage regulation of the rectifier transformer and switching of the electrolyzers. This application provides an energy efficiency optimization method and system for wind and solar power hydrogen production systems, which can achieve coordinated optimization control of the rectifier transformer and the electrolyzer array, ensuring that the rectifier transformer always operates within the economic load rate range, effectively reducing system iron and copper losses, and improving the overall energy efficiency and energy utilization efficiency of the wind and solar power hydrogen production system.

[0026] Example 1: This example introduces an energy efficiency optimization system for a wind and solar power hydrogen production system.

[0027] A wind-solar power generation hydrogen production system is an integrated energy system that produces hydrogen through water electrolysis via power conversion and transmission links. Further, refer to... Figure 4 The wind and solar power hydrogen production system of this embodiment includes a new energy power generation unit, an energy storage unit, a rectifier transformer, an IGBT rectifier power supply cabinet, and an electrolyzer array. The new energy power generation unit and the energy storage unit are electrically connected to the electrolyzer array via an AC bus, the rectifier transformer, and the IGBT rectifier power supply cabinet in sequence.

[0028] The new energy power generation unit includes a wind power generation unit and a photovoltaic power generation unit. It generates electricity using wind power and photovoltaic new energy sources and produces hydrogen with grid assistance.

[0029] Due to the fluctuating and uncertain nature of wind and solar power generation, energy storage units of a certain capacity are configured to buffer power and time-shift energy to ensure a reliable supply of the load required by the electrolyzer array under rated operating conditions. When the wind and solar power generation exceeds the power consumed by the electrolyzer, the energy storage unit absorbs and stores the excess electrical energy; when the wind and solar power generation is insufficient to support the rated operation of the electrolyzer, the energy storage unit releases electrical energy to power the hydrogen production system together with the wind and solar power generation.

[0030] An AC busbar is a common conductor or busbar in a power system that connects multiple generating, consuming, or transforming devices. It is used to collect and distribute electrical energy and serves as a hub for energy exchange between different parts of the system. Further, the AC busbar is divided into three sections: the first section is supplied from wind and solar power generation via a step-up rectifier transformer to the hydrogen production AC 10kV power supply system; the energy saving and power quality improvement of the first section are comprehensively considered by the photovoltaic and wind power generation centers. The second section is supplied from the hydrogen production AC 10kV power supply system to the high-voltage side of the rectifier transformer's primary winding. The third section is supplied from the low-voltage side of the rectifier transformer's secondary winding to the AC input terminal of the IGBT rectifier power supply cabinet.

[0031] An electrolyzer array consists of multiple electrolyzers, each producing hydrogen and oxygen through the electrolysis of water. Furthermore, the electrolyzers can be alkaline water electrolysis cells for hydrogen production.

[0032] A rectifier transformer is a front-end rectifier transformer used in rectifier equipment to convert alternating current (AC) to direct current (DC). It performs voltage transformation and isolation, providing a suitable AC input voltage for subsequent rectifier equipment. Furthermore, a single rectifier transformer and its associated electrolytic cell constitute a power supply unit. For example, each oil-immersed double-split rectifier transformer has two split windings, each connected to an electrolytic cell via an IGBT rectifier power supply cabinet. Even further, the rectifier transformer is an on-load tap-changing rectifier transformer, equipped with an on-load tap changer and multiple voltage adjustment positions. Each position corresponds one-to-one with the actual output voltage value on the secondary side: increasing the position by one level increases the actual output voltage value on the secondary side; decreasing the position by one level decreases the actual output voltage value on the secondary side.

[0033] The primary topology of the IGBT rectifier power supply cabinet is an AC / DC module used to convert source-side AC power into DC power required by the hydrogen production system. This primary topology AC / DC module is a voltage-source PWM rectifier with bidirectional reactive power output capability, capable of pushing capacitive or inductive reactive power back to the AC bus. Preferably, the voltage-source PWM rectifier adopts a dual closed-loop control structure based on an outer voltage loop and an inner current loop. The outer voltage loop is used to control the DC bus voltage stability, and the inner current loop includes an active current loop and a reactive current loop, used to control the active and reactive power on the input side of the IGBT rectifier power supply cabinet, respectively. By adjusting the setpoint of the reactive current loop, the direction and amplitude of the reactive power output by the voltage-source PWM rectifier to the AC bus are controlled.

[0034] The energy efficiency optimization system of this embodiment includes a system energy management center, which is configured to execute the steps of the energy efficiency optimization method for a wind and solar power generation hydrogen production system.

[0035] In application, the system energy management center communicates with the new energy power generation unit, energy storage unit, rectifier transformer, IGBT rectifier power supply cabinet, and electrolyzer array via industrial Ethernet. The system energy management center collects data from the new energy power generation unit, the energy storage unit, the AC bus, the rectifier transformer, and the electrolyzer array in real time, and executes the specific steps of the energy efficiency optimization method for the wind and solar power hydrogen production system based on the collected data.

[0036] In practical applications, the system energy management center includes a processor and a memory. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the energy efficiency optimization method for the wind and solar power hydrogen production system as described in any one of Embodiments 1 to 3.

[0037] Example 2: This example introduces an energy efficiency optimization method for a wind and solar power hydrogen production system.

[0038] refer to Figure 1 The energy efficiency optimization method in this embodiment includes steps SS1 to SS3.

[0039] Step SS1: The system energy management center obtains the real-time power factor from the power metering instrument on the AC bus and determines whether the real-time power factor belongs to the target power factor threshold.

[0040] In application, the target power factor threshold is the range of power factors that achieves optimal energy saving and power quality on the user side while minimizing electricity costs. Furthermore, the upper and lower limits of the target power factor threshold are determined based on the power supply method and the number of rectifier transformer stages. Specifically, the power supply method determines the electricity metering method and the power factor adjustment fee method, thereby determining the power factor range that minimizes electricity costs. The more rectifier transformer stages there are, the greater the cumulative load losses and line losses caused by the progressive flow of reactive power, thus requiring a corresponding increase in the lower limit of the target power factor. Simultaneously, to avoid overcompensation leading to bus voltage rise, resonance risk, and corresponding electricity cost penalties, an upper limit for the target power factor is set.

[0041] In some embodiments, when the real-time power factor falls within the target power factor threshold range, it indicates that the system reactive power is in a relatively balanced state, the current AC bus power quality is in a superior state, the system operating loss is low, and economic operation adjustment of the rectifier transformer can be performed. Specifically, step SS11 involves adjusting the tap position of the rectifier transformer according to its economic operating load rate range under the current actual load, so that the actual operating load rate of the rectifier transformer enters the economic operating load rate range, and recording the actual output voltage value of the secondary side of the rectifier transformer as a voltage reference. The voltage reference is determined by the tap position of the rectifier transformer; subsequent steps SS33 and SS34, which adjust reactive power, are only used to correct the deviation between the real-time AC bus voltage value and the voltage reference, without changing the voltage reference itself.

[0042] The economic operating load rate range refers to the range of load rates within which the total losses (including iron losses and copper losses) of the rectifier transformer are at or near their lowest levels under specific operating conditions. Bringing the actual operating load rate of the rectifier transformer into this economic operating load rate range helps reduce the energy losses of the rectifier transformer itself and improves the overall energy efficiency of the system.

[0043] Furthermore, the method for determining the economic operating load rate range includes: when the real-time power factor of the AC bus is within the target power factor threshold, determining the economic operating load rate range of the rectifier transformer under the current actual load based on the real-time load loss, rated copper loss, and rated iron loss of the rectifier transformer.

[0044] Specifically, the real-time load loss of a rectifier transformer includes iron loss and copper loss. Rated iron loss is the loss of the rectifier transformer when operating under no-load conditions at rated voltage, while rated copper loss is the loss when operating at rated current. Both are inherent parameters of the rectifier transformer and can be obtained from its nameplate or design data. Real-time load loss is the loss value of the rectifier transformer under the current actual load, which can be estimated by monitoring the output current of the rectifier transformer and combining it with its winding resistance.

[0045] The method for determining the economic operating load rate range includes: calculating the operating efficiency of the rectifier transformer under the current actual load based on the rated iron loss, the rated copper loss, and the real-time load loss; when the actual operating load rate of the rectifier transformer changes, the total loss of the rectifier transformer changes accordingly; when the actual operating load rate is too low, the iron loss dominates the total loss, resulting in low efficiency; when the actual operating load rate is too high, the copper loss increases sharply, and the efficiency also decreases; when the total loss is at its lowest, the operating efficiency of the rectifier transformer is at its highest, and the range of the actual operating load rate corresponding to this point is the economic operating load rate range.

[0046] In practical applications, tap positions refer to the multiple taps set on the windings of a rectifier transformer. Switching taps changes the transformer's turns ratio, thereby altering the actual output voltage value on the secondary side. With a constant load power, changes in output voltage cause changes in load current, thus altering the operating load rate of the rectifier transformer and bringing it closer to the economic operating range. After adjustment, the system's energy management center records the actual output voltage value on the secondary side of the rectifier transformer. Simultaneously, an on-load tap changer is configured to allow tap switching while the rectifier transformer is energized.

[0047] The mechanism of tap changer adjustment is as follows: When the on-load tap changer is raised by one position, the actual output voltage of the rectifier transformer secondary side increases. With the electrolytic cell load distribution remaining constant, the DC output power of the IGBT rectifier power supply cabinet remains essentially constant. The secondary current of the rectifier transformer decreases, and copper losses decrease. Although iron losses increase slightly with the increase in secondary voltage, the overall loss decreases, and the actual operating load rate decreases, moving closer to the economic operating load rate range. Conversely, when the on-load tap changer is lowered by one position, with the electrolytic cell load distribution remaining constant, the secondary voltage decreases, the secondary current increases, copper losses increase, the overall loss increases, and the actual operating load rate increases. The actual operating load rate is a load rate indicator that comprehensively reflects the current actual voltage, current, and loss status of the rectifier transformer. It can be calculated based on the real-time load loss, real-time copper loss, and real-time iron loss of the rectifier transformer.

[0048] Specifically, the method for adjusting the tap position of the rectifier transformer includes: step A1 or step A2.

[0049] Step A1: When the actual operating load rate is higher than the upper limit of the economic operating load rate range, and the on-load tap changer has not reached the highest position, raise the on-load tap changer of the rectifier transformer by one position, and repeat the raising step until the actual operating load rate of the rectifier transformer enters the economic operating load rate range.

[0050] When the actual operating load rate of the rectifier transformer is detected to be higher than the upper limit of the economic operating load rate range, it indicates that the rectifier transformer may be operating in an overload or efficiency degradation region, requiring a reduction in its operating load rate. At this time, the system will determine whether the on-load tap changer of the rectifier transformer has reached its highest position. If it has not yet reached the highest position, the on-load tap changer will be raised by one position to adjust the output voltage by changing the rectifier transformer's turns ratio, thereby affecting its load characteristics and gradually reducing the actual operating load rate, avoiding system shock caused by a large-scale adjustment at once. During actual operation, the step of raising the tap changer will be repeated until the actual operating load rate of the rectifier transformer successfully enters the preset economic operating load rate range, or the on-load tap changer has reached its highest position.

[0051] If the tap position has reached the boundary position (e.g., the highest position) and still cannot bring the actual operating load rate into the economic operating load rate range, then maintain the boundary position operation.

[0052] Step A2: When the actual operating load rate is lower than the lower limit of the economic operating load rate range, and the on-load tap changer has not reached the lowest position, the on-load tap changer of the rectifier transformer is lowered by one position, and the down-slotting step is repeated until the actual operating load rate of the rectifier transformer enters the economic operating load rate range.

[0053] When the actual operating load rate of the rectifier transformer is detected to be lower than the lower limit of the economic operating load rate range, it indicates that the rectifier transformer is currently operating in an inefficient region and its operating load rate needs to be increased to achieve a better operating state. At this time, the system will determine whether the on-load tap changer of the rectifier transformer has reached the lowest position. If it has not yet reached the lowest position, the on-load tap changer will be lowered by one position to adjust its output voltage by changing the rectifier transformer turns ratio, so that the actual operating load rate gradually increases, avoiding system shock caused by a one-time large adjustment. In actual operation, the step of lowering the tap will be repeated until the actual operating load rate of the rectifier transformer returns to the economic operating load rate range, or the on-load tap changer has reached the lowest position.

[0054] If the tap position has reached the boundary position (e.g., the lowest position) and still cannot bring the actual operating load rate into the economic operating load rate range, then maintain the boundary position operation.

[0055] In some embodiments, when the real-time power factor is not within the target power factor threshold range, the AC bus power factor is first adjusted to bring the real-time power factor within the target power factor threshold, effectively reducing AC bus losses and improving power quality. Further, the voltage-source PWM rectifier adjusts the amplitude and phase of its AC-side voltage vector to change the phase difference between the AC-side current and the AC bus voltage, thereby achieving continuous reactive power regulation. When the AC-side current of the voltage-source PWM rectifier leads the real-time voltage value of the AC bus, the voltage-source PWM rectifier outputs capacitive reactive power to the AC bus; when the AC-side current of the voltage-source PWM rectifier lags behind the real-time voltage value of the AC bus, the voltage-source PWM rectifier outputs inductive reactive power to the AC bus. Specifically, steps SS12 and SS13 are executed.

[0056] Step SS12: When the real-time power factor of the AC bus is less than the target power factor threshold, start the first-level topology AC / DC module of the IGBT rectifier power supply cabinet to output the first capacitive reactive power to the AC bus until the real-time power factor rises to within the target power factor threshold. (Refer to...) Figure 2 The magnitude of the first inductive reactive power is determined based on the reactive power injected from the system required to raise the real-time power factor to within the target power factor threshold range.

[0057] Specifically, when the real-time power factor of the AC bus is less than the lower limit of the target power factor threshold, the system energy management center sends a reactive power command to the IGBT rectifier power supply cabinet to control the first-level topology AC / DC module to inject reactive power into the AC bus, thereby enhancing the AC bus voltage support and reducing the reactive current to improve the real-time power factor until the real-time power factor rises to within the target power factor threshold.

[0058] Step SS13: When the real-time power factor of the AC bus is greater than the target power factor threshold, start the first-level topology AC / DC module of the IGBT rectifier power supply cabinet to output the first inductive reactive power to the AC bus until the real-time power factor decreases to within the target power factor threshold. (Refer to...) Figure 2 The magnitude of the first capacitive reactive power is determined based on the reactive power required to reduce the real-time power factor to within the target power factor threshold range.

[0059] Specifically, when the real-time power factor of the AC bus is greater than the lower limit of the target power factor threshold, the system energy management center sends a reactive power command to the IGBT rectifier power supply cabinet to control the first-level topology AC / DC module to absorb reactive power from the AC bus in order to reduce the real-time power factor until the real-time power factor rises to within the target power factor threshold.

[0060] After adjusting the tap position of the rectifier transformer, the system energy management center re-acquires the real-time power factor of the AC bus and determines whether it still falls within the target power factor threshold. If the real-time power factor exceeds the target power factor threshold, step SS12 or step SS13 is executed until the real-time power factor returns to within the target power factor threshold.

[0061] Step SS2: Determine the operating scheme of the electrolytic cell array based on the total available power supply and the actual output voltage value of the secondary side, and issue switching commands to the electrolytic cell array according to the operating scheme.

[0062] In application, the total available power supply refers to the sum of the actual power generation of the new energy power generation unit and the current discharge capacity of the energy storage unit in the wind and solar power hydrogen production system, which represents the maximum power that the system can provide to the electrolyzer array at a certain moment.

[0063] Furthermore, the method for determining the total available power supply includes: taking the sum of the actual power generation of the new energy power generation unit in the wind and solar power hydrogen production system and the current discharge capacity of the energy storage unit as the total available power supply. The actual power generation of the new energy power generation unit includes the output power of the wind turbine generator and photovoltaic array monitored in real time; the current discharge capacity of the energy storage unit is related to the current state of charge of the energy storage battery, the maximum discharge rate, and the system's strategy for energy storage lifespan.

[0064] In practical applications, the operating plan refers to the specific strategy for the conductive electrolyzer array to perform hydrogen production. Further, the operating plan includes: the total number of electrolyzers put into operation and the load allocation value for each electrolyzer in operation.

[0065] The total number of electrolyzers put into operation refers to the actual number of electrolyzers that the system decides to start and participate in hydrogen production under the current operating conditions. This requires comprehensive consideration of the total available power supply, the minimum operating load of the electrolyzers, the maximum operating load of the electrolyzers, and the hydrogen production efficiency curve. For example, the system can initially estimate the required number of electrolyzers based on the total power demand and the rated power of a single electrolyzer, and then optimize this estimate by taking into account the start-up and shutdown characteristics of the electrolyzers.

[0066] The load allocation value for each operational electrolyzer refers to the specific power or current value allocated to each operational electrolyzer. This allocation needs to be based on the characteristics of the electrolyzer and the overall system optimization goals. For example, based on the hydrogen production efficiency curve of the electrolyzer, more load can be allocated to the currently more efficient electrolyzer, or all electrolyzers can be operated within their optimal efficiency range while meeting the total load demand.

[0067] In actual operation, the constraints that the operation plan must meet include: (1) The sum of the load distribution values ​​of each electrolyzer in operation shall not exceed the total available power supply, so as to avoid problems such as underload of electrolyzers, frequent start-up and shutdown or system crash due to insufficient power supply, so as to ensure the continuity and stability of the hydrogen production process. (2) The sum of the load distribution values ​​of each electrolyzer in operation shall not exceed the maximum output DC power of the IGBT rectifier power supply cabinet corresponding to the actual output voltage value of the secondary side, so as to ensure that the total load demand of the electrolyzer array will not exceed the safe operating limit of the IGBT rectifier power supply cabinet under the current voltage conditions, prevent the IGBT rectifier power supply cabinet from malfunctioning or being damaged due to overload, and ensure the safe and reliable operation of the entire power conversion link. Among them, the maximum output DC power of the IGBT rectifier power supply cabinet can be calculated based on the total available power supply and the actual output voltage value of the secondary side of the rectifier transformer.

[0068] When determining the operation plan, the system energy management center can, under the premise of meeting the above constraints, aim at maximizing the system's hydrogen production, overall energy efficiency, or economic benefits, and select the optimal combination of the number of electrolyzers to be put into operation and the load allocation value by combining the differences in hydrogen production efficiency curves, start-up and shutdown times, and response characteristics of each electrolyzer. Alternatively, it can adopt various operation plans, such as operating some electrolyzers at rated capacity and operating the rest at low load, and adjust the operating load of each electrolyzer as needed.

[0069] Step SS3: After the electrolytic cell array executes the switching command, compare the relationship between the actual operating load rate after switching and the economic operating load rate range, referring to... Figure 3 .

[0070] In application, the actual load loss of the rectifier transformer after switching is obtained, and the actual operating load rate after switching is calculated based on the actual load loss, actual copper loss and actual iron loss of the rectifier transformer after switching.

[0071] In practical applications, the actual load loss after the rectifier transformer is switched on or off can be obtained by: measuring it through an online monitoring device for rectifier transformer losses; or by measuring the current and voltage on the secondary side of the rectifier transformer and calculating it in conjunction with the rectifier transformer parameters; or by calculating it through the difference between the active power input on the primary side and the active power output on the secondary side of the rectifier transformer.

[0072] The methods for obtaining the actual iron loss of the rectifier transformer after switching include: measurement using an online loss monitoring device for the rectifier transformer; or calculation using the voltage and current of the primary and secondary sides of the rectifier transformer combined with an iron loss calculation model; or obtaining the actual iron loss through no-load testing or by adjusting the no-load loss value in the rectifier transformer nameplate parameters based on the relationship between the current actual operating voltage and the rated voltage. The methods for obtaining the actual copper loss of the rectifier transformer after switching include: acquiring the primary and secondary current waveforms using an online loss monitoring device for the rectifier transformer, and calculating the copper loss including harmonics based on a built-in loss model. The methods for obtaining the actual iron loss of the rectifier transformer after switching include: acquiring the voltage and current waveforms using an online loss monitoring device for the rectifier transformer, and separating and calculating the iron loss in real time based on a built-in model.

[0073] In some embodiments, when the actual operating load rate after switching deviates from the economic operating load rate range, a load adjustment command is sent to the electrolytic cell array to adjust the load allocation value of each electrolytic cell put into operation, so that the actual operating load rate after switching returns to the economic operating load rate range.

[0074] In application, the load adjustment command is intended to adjust the load distribution value of each electrolytic cell put into operation. Adjusting the load distribution value of each electrolytic cell put into operation includes steps SS31 to SS32.

[0075] Step SS31: If the actual operating load rate after the switchover is lower than the lower limit of the economic operating load rate range, the load allocation value of the electrolytic cells already in operation will be increased to the rated load first. If, after all the electrolytic cells in operation have reached the rated load, the actual operating load rate after the switchover is still lower than the lower limit of the economic operating load rate range, the electrolytic cells not yet in operation will be started. The newly started electrolytic cells will be put into operation at the minimum operating load, and then gradually loaded. The minimum operating load is the minimum load for safe operation of the electrolytic cells, typically 20% to 40% of the rated load.

[0076] When applied, if the actual operating load rate after switching is lower than the lower limit of the economic operating load rate range, the load allocation value of the electrolytic cells already in operation will be increased to the rated load first, avoiding unnecessary equipment start-ups and shutdowns, thereby reducing energy loss and equipment wear.

[0077] In practical applications, if after all operating electrolytic cells have reached their rated load, the actual operating load rate after switching is still lower than the lower limit of the economic operating load rate range, then it is determined whether there are any electrolytic cells that are not in operation. If there are electrolytic cells that are not in operation, one or more new electrolytic cells will be started. The number of cells started will be determined based on the difference between the actual operating load rate after switching and the lower limit of the economic operating load rate range, as well as the rated power of a single electrolytic cell. The newly started electrolytic cells will be put into operation at the minimum operating load, and then gradually loaded. The above judgment process will be repeated to smoothly increase the actual operating load rate of the rectifier transformer to the economic operating load rate range. If there are no unoperated electrolytic cells, meaning all electrolytic cells are operational and at their rated load, but the actual operating load rate after the switching is still lower than the lower limit of the economic operating load rate range, then the current state of all electrolytic cells operating at their rated load will be maintained, and the power deficit information of the electrolytic cells will be sent to the system energy management center. During actual operation, the system energy management center can compensate for the power deficit by increasing the output of new energy power generation units or increasing the discharge power of energy storage units.

[0078] Step SS32: If the actual operating load rate after switching is higher than the upper limit of the economic operating load rate range, the load allocation value of the electrolytic cell with the lowest efficiency is gradually reduced. After the load allocation value of the electrolytic cell drops to the minimum operating load, the electrolytic cell is disconnected.

[0079] In application, if the actual operating load rate is high after switching on / off, it indicates that the system is overloaded, which may lead to a decrease in the operating efficiency of the rectifier transformer or an overload risk. To reduce the load on the rectifier transformer, the load allocation value of the electrolyzer with the lowest efficiency should be gradually reduced first. Selecting the electrolyzer with the lowest efficiency for load reduction helps to maximize the overall hydrogen production efficiency of the system while reducing the total load. After the load allocation value of the electrolyzer has been reduced to the minimum operating load, if the actual operating load rate still needs to be further reduced after switching on / off, the electrolyzer is disconnected, thereby effectively reducing the total load and allowing the actual operating load rate of the rectifier transformer to fall back to the economic operating load rate range.

[0080] In practical applications, after each electrolytic cell is removed, the actual operating load rate of the rectifier transformer is re-acquired. If it is still higher than the upper limit of the economic operating load rate range, step SS32 is repeated until the actual operating load rate enters the economic operating load rate range.

[0081] It is worth noting that the minimum operating load is the minimum load required for the safe operation of the electrolytic cell. Furthermore, the constraints for adjusting the load distribution value of each electrolytic cell in operation include: the sum of the adjusted load distribution values ​​of each electrolytic cell in operation does not exceed the total available power supply, ensuring that the power demand of the electrolytic cell array does not exceed the actual supply capacity of the power supply side; and the sum of the adjusted load distribution values ​​of each electrolytic cell in operation does not exceed the maximum output DC power of the IGBT rectifier power supply cabinet corresponding to the actual output voltage value of the secondary side, ensuring that the IGBT rectifier power supply cabinet will not be damaged due to overload, while ensuring that the electrolytic cell array can obtain a stable DC power supply that meets its operating requirements.

[0082] In some embodiments, when the actual operating load rate after switching does not deviate from the economic operating load rate range, the voltage deviation between the real-time voltage value of the AC bus and the actual output voltage value of the secondary side is obtained; when the absolute value of the voltage deviation exceeds the allowable deviation value, the reactive power output of the primary topology AC / DC module of the IGBT rectifier power supply cabinet to the AC bus is adjusted to actively adjust the AC bus voltage, so that the real-time voltage value approaches the actual output voltage value of the secondary side, until the absolute value of the voltage deviation falls back to within the allowable deviation value, so as to solve the power quality degradation and system stability problems caused by voltage deviation.

[0083] In application, when the absolute value of the voltage deviation exceeds a preset allowable deviation value, the system energy management center will instruct the primary topology AC / DC module of the IGBT rectifier power supply cabinet to output reactive power to the AC bus. The method for determining the allowable deviation value includes: determining the allowable voltage deviation value corresponding to the nominal voltage level of the AC bus in the wind-solar power generation hydrogen production system; determining the allowable voltage deviation value of the rectifier transformer based on the allowable deviation of the rectifier transformer's power supply voltage; and taking the intersection of the allowable voltage deviation value corresponding to the nominal voltage level of the AC bus and the allowable voltage deviation value of the rectifier transformer as the allowable deviation value.

[0084] In practical applications, the system energy management center maintains a constant DC current output from the IGBT rectifier power supply cabinet to the electrolyzer array while adjusting the reactive power. During AC side voltage stabilization control, the system energy management center prioritizes ensuring the normal operation of the electrolyzer array. The IGBT rectifier power supply cabinet has independent active and reactive power control channels. The system energy management center can ensure that while adjusting reactive power to stabilize the AC bus voltage, the IGBT rectifier power supply cabinet can continue to supply power to the electrolyzer array according to the preset DC current command, maintaining the stability and continuity of the hydrogen production process.

[0085] In actual operation, based on the determined direction and amplitude of reactive power, the amplitude and phase of the AC-side output voltage of the primary topology AC / DC module of the IGBT rectifier power supply cabinet are adjusted to make the real-time voltage value of the AC bus approach the actual output voltage value of the secondary side. The primary topology AC / DC module of the IGBT rectifier power supply cabinet is a voltage-type PWM rectifier, which controls the direction and amplitude of reactive power exchanged with the AC bus by adjusting the amplitude and phase of the AC-side voltage vector, thereby changing the phase difference between the AC-side current and the AC bus voltage. When the AC-side current leads the AC bus voltage, capacitive reactive power is output to the bus; when the AC-side current lags the AC bus voltage, inductive reactive power is output to the bus. Furthermore, during the adjustment of reactive power, the DC current output by the IGBT rectifier power supply cabinet to the electrolyzer array remains constant to ensure that the hydrogen production rate is not disturbed by the voltage correction process. Specifically, steps SS33 to SS34 are executed.

[0086] Step SS33: When the real-time voltage value is higher than the actual output voltage value of the secondary side and the absolute value of the voltage deviation exceeds the allowable deviation value, the primary topology AC / DC module of the IGBT rectifier power supply cabinet outputs a second inductive reactive power to the AC bus. By absorbing the inductive reactive power, the AC bus voltage is effectively reduced, so that the real-time voltage value of the AC bus approaches the actual output voltage value of the secondary side.

[0087] In application, the amplitude of the second inductive reactive power is determined based on the absolute value of the voltage deviation, and the amplitude of the second inductive reactive power increases as the absolute value of the voltage deviation increases.

[0088] Step SS34: When the real-time voltage value is lower than the actual output voltage value of the secondary side and the absolute value of the voltage deviation exceeds the allowable deviation value, the primary topology AC / DC module of the IGBT rectifier power supply cabinet outputs a second capacitive reactive power to the AC bus to increase the AC bus voltage and make the real-time voltage value of the AC bus approach the actual output voltage value of the secondary side.

[0089] In application, the amplitude of the second capacitive reactive power is determined based on the absolute value of the voltage deviation, and the amplitude of the second capacitive reactive power increases as the absolute value of the voltage deviation increases.

[0090] If repeated tap changer adjustment and / or reactive power adjustment reach the preset maximum number of adjustments and still fail to meet the requirements for real-time power factor, actual operating load rate, and / or voltage deviation, then maintain the current operating state.

[0091] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for optimizing the energy efficiency of a wind-solar power generation hydrogen production system, characterized in that, include: When the real-time power factor of the AC bus is within the target power factor threshold, the tap position of the rectifier transformer is adjusted according to the economic operating load rate range of the rectifier transformer under the current actual load, so that the actual operating load rate of the rectifier transformer enters the economic operating load rate range, and the actual output voltage value of the secondary side of the rectifier transformer is recorded. Based on the total available power supply and the actual output voltage of the secondary side, the operation plan of the electrolytic cell array is determined, and the switching command is issued to the electrolytic cell array according to the operation plan; After the electrolytic cell array executes the switching command, the relationship between the actual operating load rate after switching and the economic operating load rate range is compared: when the actual operating load rate after switching deviates from the economic operating load rate range, a load adjustment command is issued to the electrolytic cell array to adjust the load allocation value of each electrolytic cell put into operation, so that the actual operating load rate after switching returns to the economic operating load rate range.

2. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 1, characterized in that, Also includes: When the real-time power factor of the AC bus is less than the target power factor threshold, the first-level topology AC / DC module of the IGBT rectifier power supply cabinet is started to output the first capacitive reactive power to the AC bus until the real-time power factor rises to within the target power factor threshold. When the real-time power factor of the AC bus is greater than the target power factor threshold, the first-level topology AC / DC module of the IGBT rectifier power supply cabinet is started to output the first inductive reactive power to the AC bus until the real-time power factor is reduced to within the target power factor threshold.

3. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 1, characterized in that, The method for determining the economic operating load rate range includes: When the real-time power factor of the AC bus is within the target power factor threshold, the economic operating load rate range of the rectifier transformer under the current actual load is determined based on the real-time load loss, rated copper loss and rated iron loss of the rectifier transformer. The method for determining the total available power supply includes: taking the sum of the actual power generation of the new energy power generation unit of the wind and solar power hydrogen production system and the current discharge capacity of the energy storage unit as the total available power supply.

4. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 1, characterized in that, The method for adjusting the tap position of the rectifier transformer includes: When the actual operating load rate is higher than the upper limit of the economic operating load rate range and the on-load tap changer has not reached the highest position, the on-load tap changer of the rectifier transformer is raised by one position, and the raising step is repeated until the actual operating load rate of the rectifier transformer enters the economic operating load rate range. When the actual operating load rate is lower than the lower limit of the economic operating load rate range, and the on-load tap changer has not reached the lowest position, the on-load tap changer of the rectifier transformer is lowered by one position, and the down-slotting step is repeated until the actual operating load rate of the rectifier transformer enters the economic operating load rate range. If the tap position has reached the boundary position but still cannot bring the actual operating load rate into the economic operating load rate range, then maintain the boundary position operation.

5. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 1, characterized in that, The operation plan includes: the total number of electrolytic cells put into operation and the load allocation value for each electrolytic cell put into operation; The constraints of the operation plan include: the sum of the load distribution values ​​of each electrolytic cell put into operation does not exceed the total available power supply; and the sum of the load distribution values ​​of each electrolytic cell put into operation does not exceed the maximum output DC power of the IGBT rectifier power supply cabinet corresponding to the actual output voltage value of the secondary side.

6. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 1, characterized in that, The adjustment of the load distribution value for each electrolytic cell put into operation includes: If the actual operating load rate after the switch is lower than the lower limit of the economic operating load rate range, the load allocation value of the electrolytic cells already in operation will be increased to the rated load first; if the actual operating load rate after the switch is still lower than the lower limit of the economic operating load rate range after all the electrolytic cells already in operation have reached the rated load, the electrolytic cells not yet in operation will be started, and the newly started electrolytic cells will be put into operation at the minimum operating load, and then gradually loaded. If the actual operating load rate after switching is higher than the upper limit of the economic operating load rate range, the load allocation value of the electrolytic cell with the lowest efficiency will be gradually reduced. Once the load allocation value of the electrolytic cell drops to the minimum operating load, the electrolytic cell will be disconnected.

7. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 6, characterized in that, The constraints for adjusting the load distribution value of each electrolytic cell put into operation include: The sum of the adjusted load distribution values ​​for each electrolytic cell put into operation shall not exceed the total available power supply. The sum of the load distribution values ​​of each electrolytic cell put into operation after adjustment shall not exceed the maximum output DC power of the IGBT rectifier power supply cabinet corresponding to the actual output voltage value of the secondary side.

8. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 1, characterized in that, The energy efficiency optimization method also includes: When the actual operating load rate after the switching does not deviate from the economic operating load rate range, the voltage deviation between the real-time voltage value of the AC bus and the actual output voltage value of the secondary side is obtained. When the absolute value of the voltage deviation exceeds the allowable deviation value, the reactive power output of the primary topology AC / DC module of the IGBT rectifier power supply cabinet to the AC bus is adjusted so that the real-time voltage value approaches the actual output voltage value of the secondary side, until the absolute value of the voltage deviation falls back to within the allowable deviation value. During the adjustment of the reactive power, the DC current output from the IGBT rectifier power supply cabinet to the electrolytic cell array is kept constant.

9. The energy efficiency optimization method for a wind-solar power generation hydrogen production system according to claim 8, characterized in that, The regulation of reactive power output from the primary topology AC / DC module of the IGBT rectifier power supply cabinet to the AC bus includes: When the real-time voltage value is higher than the actual output voltage value of the secondary side and the absolute value of the voltage deviation exceeds the allowable deviation value, the primary topology AC / DC module of the IGBT rectifier power supply cabinet outputs the second inductive reactive power to the AC bus. When the real-time voltage value is lower than the actual output voltage value of the secondary side and the absolute value of the voltage deviation exceeds the allowable deviation value, the primary topology AC / DC module of the IGBT rectifier power supply cabinet outputs a second capacitive reactive power to the AC bus.

10. An energy efficiency optimization system for a wind-solar power generation hydrogen production system, characterized in that, The wind and solar power hydrogen production system includes a new energy power generation unit, an energy storage unit, a rectifier transformer, an IGBT rectifier power supply cabinet, and an electrolyzer array. The new energy power generation unit and the energy storage unit are connected to the electrolyzer array via an AC bus, the rectifier transformer, and the IGBT rectifier power supply cabinet in sequence. The energy efficiency optimization system includes a system energy management center, which is configured to perform the steps of the energy efficiency optimization method for a wind and solar power generation hydrogen production system as described in any one of claims 1 to 9.

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