Hydrogen storage coordinated control method for hydrogen-electricity coupled three-port dc transformer

Abstract

The application discloses a hydrogen-electricity coupling three-port direct-current transformer hydrogen storage coordination control method. The coordination control method comprises the following steps: collecting photovoltaic power generation power in a direct-current microgrid system connected with a first port of a three-port direct-current transformer and medium-voltage direct-current bus load demand power, and taking a power difference value; collecting actual power values of a second port and a third port of the three-port direct-current transformer, comparing the actual power values with power reference values of the second port and the third port respectively, and obtaining power differences of the second port and the third port; establishing a relationship between a phase-shifting ratio of the three-port direct-current transformer and the power differences of the second port and the third port; and adjusting the phase-shifting ratio of the second port and the third port based on the power differences of the second port and the third port and the phase-shifting ratio relationship. The application dynamically adjusts the power of each port of the three-port direct-current transformer, coordinates power distribution between energy storage and electrolytic cells, and realizes efficient utilization of renewable energy.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage coordinated control and relates to a hydrogen storage coordinated control method for a hydrogen-electric coupling three-port DC transformer. Background Technology

[0002] Because renewable energy generation, such as wind or solar power, is intermittent and irregular, it affects grid operation. However, coordinating with energy storage devices can effectively solve these problems. Hydrogen energy, as an emerging green energy source, has the advantages of abundant reserves, high energy density, and being non-toxic and pollution-free. Hydrogen production through electrolysis can effectively absorb fluctuating power, greatly improving the problem of wind and solar power curtailment, and has received widespread attention within the industry.

[0003] In electrolytic hydrogen production applications, ideally, the electrolyzer operates under rated conditions with a power fluctuation tolerance within 0-100%. In practical applications, to reduce energy consumption and the impact of frequent start-stop cycles on the electrolyzer's lifespan, energy storage units are needed to maintain operation at minimum capacity. Multi-port DC transformers can simultaneously connect the electrolyzer and energy storage to a DC microgrid system, reducing intermediate conversion stages and improving energy conversion efficiency. In practical engineering, multi-port DC transformers use multiple sub-modules connected in series and parallel, effectively adapting to the low-voltage, high-current characteristics required by the electrolyzer and solving the problems of high-power, multi-voltage level conversion, and device withstand voltage when connecting hydrogen production power to a DC microgrid. However, the dynamic response speed of the electrolyzer in a multi-port DC transformer is relatively slow, necessitating the solution of coordinated control between the electrolyzer and energy storage at different time scales. Therefore, researching hydrogen-storage power coordination control strategies for electrolytic hydrogen production and energy storage devices is particularly important. Summary of the Invention

[0004] In view of this, the present invention proposes a hydrogen storage coordinated control method for a hydrogen-electric coupling three-port DC transformer. It utilizes a multi-port DC transformer to connect the electrolytic hydrogen production-electrolyzer and energy storage into a DC microgrid. By coordinating the electrolytic hydrogen production and energy storage, the power fluctuations in the system are smoothed, and the power distribution between energy storage and electrolyzer is coordinated, thereby achieving efficient utilization of renewable energy and extending the service life of the electrolyzer.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method, wherein the first port of the three-port DC transformer is connected to the load through the medium-voltage DC bus in the DC microgrid system and is a free port; the second port of the three-port DC transformer is connected to the energy storage device through the low-voltage DC bus in the DC microgrid system and is in power control mode; the third port of the three-port DC transformer is connected to the electrolyzer and is in power control mode.

[0006] The aforementioned coordination and control method includes:

[0007] The photovoltaic power generation and the load demand of the medium-voltage DC bus in the DC microgrid system connected to the first port are collected, and the power difference is obtained; based on the power difference, the power allocation between the second port and the third port is coordinated.

[0008] The actual power of the second and third ports of the three-port DC transformer is collected and compared with the power reference values ​​of the second and third ports of the three-port DC transformer to obtain the power difference between the second and third ports.

[0009] Establish the relationship between the shift ratio of the three-port DC transformer and the power difference between the second and third ports. Based on the relationship between the power difference between the second and third ports and the shift ratio, adjust the shift ratio of the second and third ports.

[0010] Furthermore, the relationship between the shift ratio of the three-port DC transformer and the power difference between the second and third ports is as follows: the difference between the power reference value and the actual power of each port is passed through a PI circuit to output the shift ratio of each port.

[0011] The specific details of coordinating the power distribution between the second and third ports are as follows:

[0012] The power reference values ​​for the second and third ports are:

[0013] When the power difference is greater than 0 and greater than or equal to the rated power of the third port: if the state of charge of the second port is less than or equal to its maximum state of charge, the power reference value of the third port is its rated power, and the power reference value of the second port is the difference between the power difference and the rated power of the third port; otherwise, the reference power of the second port is 0, and the power reference value of the third port is its rated power.

[0014] When the power difference is greater than 0 and less than the rated power of the third port, but greater than or equal to the minimum operating power of the third port: the power reference value of the third port is the power difference, and the power reference value of the second port is 0.

[0015] When the power difference is greater than 0 and less than the minimum operating power of the third port: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is the minimum operating power of the third port, and the power reference value of the second port is the difference between the power difference and the minimum operating power of the third port; otherwise, the reference power value of the third port is 0, and the power reference value of the second port is 0.

[0016] When the power difference is equal to 0: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is its minimum operating power, and the power reference value of the second port is the power reference value of the third port; otherwise, the reference power of the third port is 0, and the reference power of the second port is 0.

[0017] When the power difference is less than 0: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is its minimum operating power, and the power reference value of the second port is the difference between the power difference and the minimum operating power of the third port; otherwise, the reference power of the third port is 0, and the reference power of the second port is 0.

[0018] When a load change occurs, based on the above situation, the power reference value of the third port remains unchanged, and the power reference value of the second port is the difference between the original power reference value and the load change amount.

[0019] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Greater than the medium load P on the grid side G Unloaded mutation amount P d And excess photovoltaic output P PV_s The rated power P of hydrogen production by electrolysis is greater than or equal to that of hydrogen production. 3n Time: To achieve maximum utilization of renewable energy, the power reference value of the third port is set to the rated power P of the third port. 3n At this time, the surplus power in the DC microgrid system is absorbed by the energy storage device, and the power reference value P at the second port... 2ref It should be within the power limit allowed by the second port power, i.e., P 2min ≤P 2ref ≤P 2max P 2max With P 2min These represent the maximum and minimum charge / discharge power allowed at the second port, respectively; when the SOC during charging reaches the maximum SOC of the energy storage device... max When charging is in progress, the energy storage device is prohibited from charging, and the power reference value of the second port is 0; when the SOC during charging has not reached the maximum SOC of the energy storage device. max At that time, the power reference value at the second port is the excess photovoltaic output P. PV_s With the rated power P of the third port 3n The difference;

[0020] The product of the voltage U2 at the second port and the current I2 at the second port, P2, and the power reference value P sent to the second port. 2ref Subtraction, followed by a PI regulator, yields the shift ratio d between the second port and the first port. 21 When the SOC of the energy storage device = SOC maxWhen this occurs, the energy storage device prohibits charging, sends an alarm to the upper-level controller, and limits photovoltaic output; the power reference value P at the third port is then... 3ref Slope limiting is applied, and the power reference value P is used. 3ref After subtracting the actual power value P3 collected at the third port, the result is passed through another PI regulator to obtain the shift ratio d between the third port and the first port. 31 .

[0021] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Greater than the medium load P on the grid side G Unloaded mutation amount P d And excess photovoltaic output P PV_s Less than the rated power P of the third port 3n The minimum operating power P defined by the third port is greater than or equal to that of the third port. 3min At this time, to achieve the maximum utilization rate of renewable energy, the power reference value at the third port is the excess photovoltaic output P. PV_s In the DC microgrid system, the surplus power after electrolysis for hydrogen production is 0, and the power reference value of the second port is 0.

[0022] The second port does not participate in power transmission in the DC microgrid system. Excess photovoltaic output is used entirely for hydrogen electrolysis. The second port transmits zero power, and the upper-level controller sends P to the second port. 2ref Subtracting the actual power value P2 from the second port, the shift ratio d is obtained after passing through a PI regulator. 21 At this time, the power reference value P of the third port 3ref For P PV -P G The power reference value P at the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref Subtracting the first and second parts, and passing through another PI regulator, we obtain the shift ratio d between the third port and the first port. 31 .

[0023] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Greater than the medium load P on the grid side G Unloaded mutation amount P d Excess photovoltaic output P PV_s Less than the minimum operating power P of the third port 3min When the state of charge at the second port is less than the minimum state of charge, the upper-level controller sends the power reference value P to the third port. 3ref =0, the power reference value P at the second port 2ref =0; When the state of charge at the second port is greater than or equal to the minimum state of charge, the minimum power required by the electrolytic cell is P.3min The upper-level controller sends the power reference value P to the third port. 3ref =P 3min For the power reference value P 3ref After slope limiting, the final power command for the third port is obtained; the power reference value for the second port is: P 2ref =P 3min -(P PV -P G The energy storage device automatically replenishes the power difference, enabling the electrolyzer to operate in minimum power mode;

[0024] The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller. 21 The power reference value P at the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref The shift ratio d is obtained after subtraction and then passed through a PI controller. 31 When the SOC of the second port is less than or equal to the SOC min At that time, the energy storage device stops discharging and exits operation, and the electrolytic cell also exits operation.

[0025] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Equal to the load P on the grid side G Unloaded mutation amount P d When there is no excess power for hydrogen electrolysis: when the state of charge at the second port is less than the minimum state of charge, the power reference value P at the third port is... 3ref =0, the power reference value of the second port is: P 2ref =0; When the state of charge at the second port is greater than or equal to the minimum state of charge, the electrolytic cell needs to be maintained in minimum power mode to reduce the number of start-ups and shutdowns. The minimum power required by the electrolytic cell is P. 3min Since all the photovoltaic output in the system is used for loads on the grid side, the minimum power required by the electrolyzer is provided by the energy storage device. In this case, the power reference value at the third port is: P 3ref =P 3min The power reference value P at the third port 3ref After slope limiting, the final power command for the third port is obtained. The power reference value for the second port is: P 2ref =P 3min The energy storage device provides the required power for the third port;

[0026] The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller.21 The power reference value P at the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref The shift ratio d is obtained after subtraction and then passed through a PI controller. 31 When the SOC of the second port is less than or equal to the SOC min At that time, the energy storage device stops discharging and exits operation, and the electrolytic cell also exits operation.

[0027] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Less than the medium load P on the grid side G Unloaded mutation amount P d Time: Output P of the photovoltaic power generation system in the DC microgrid system PV All used for load P on the grid side G When the state of charge at the second port is less than the minimum state of charge, the power reference value P at the third port... 3ref =0, the power reference value of the second port is: P 2ref =0; When the state of charge at the second port is greater than or equal to the minimum state of charge, a portion of the energy storage device at the second port provides the minimum power P to the electrolyzer. 3min The other part provides the output power of the photovoltaic power generation system P PV With load P in the power grid G The difference is P PV_s P PV_s =P PV -P G The power reference value for the second port is: P 2ref =|P pv -P G |+P 3min The upper-level controller will use the power reference value P at the second port. 2ref The power is sent to the DC transformer at the third port to control the energy storage device to replenish the power difference. In this mode, the charging and discharging safety of the second port is guaranteed by the upper-level controller, and the power reference value P of the third port is used. 3ref Operating at minimum power P 3min P 3ref =P 3min The upper-level controller sends the power reference value P to the third port. 3ref The final power command for the third port is obtained after slope limiting.

[0028] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Greater than the medium load P on the grid side G The load mutation amount P d Time: When the load suddenly increases, P d>0, calculate the relationship between the surplus power in the DC microgrid system and the power required by the electrolytic cell; when P PV_s ≥P 3n P PV_s =P PV -P G The third port operates at maximum power, while the second port responds to load changes. The power reference value for the second port is the surplus power in the current DC microgrid system; when P 3min ≤P PV_s <P 3n The third port operates at the power reference value P. 3ref =P PV_s The second port responds to load changes; the DC microgrid system has no surplus power, and the power reference value at the second port is 0; when P PV_s <P 3min To reduce the number of start-ups and shutdowns of the electrolytic cell, the power reference value P at the third port is... 3ref =P 3min The second port responds to load changes and provides the required power P in the DC microgrid system. 2ref =P 3min -P PV_s The upper-level controller's power reference value P for the third port 3ref Slope limiting is applied to obtain the final power reference value; the charging and discharging safety of the second port is guaranteed by the upper-level controller; when the load suddenly decreases, P d If the value is less than 0, the selection of the power reference value for the port is re-evaluated based on the aforementioned method.

[0029] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Equal to the load P on the grid side G The load mutation amount P d Time: When the load suddenly decreases, P d <0, calculate the surplus power P in the DC microgrid system. PV_s The relationship between P and the power required by the electrolytic cell; when P PV_s ≥P 3n The third port operates at maximum power, while the second port responds to load changes. The power reference value for the second port is the surplus power in the current DC microgrid system; when P 3min ≤P PV_s <P 3n The third port operates at the power reference value P. 3ref =P PV_s The second port responds to load changes; the DC microgrid system has no surplus power, and the power reference value at the second port is 0; when P PV_s <P 3min To reduce the number of start-ups and shutdowns of the electrolytic cell, the power reference value P at the third port is... 3ref=P 3min The second port responds to load changes and provides the required power P in the DC microgrid system. 2ref =P 3min -P PV_s The upper-level controller's power reference value P for the third port 3ref Slope limiting is applied to obtain the final power reference value; the charging and discharging safety of the second port is guaranteed by the upper-level controller; when the load suddenly increases, P d >0, based on the aforementioned method, re-determine the selection of the port's power reference value.

[0030] Furthermore, when the output P of the photovoltaic power generation system in the DC microgrid system... PV Less than the medium load P on the grid side G The load mutation amount P d Time: When the load suddenly decreases, P d <0, calculate the surplus power P in the DC microgrid system. PV_s The relationship between P and the power required by the electrolytic cell; when P PV_s ≥P 3n The third port operates at maximum power, while the second port responds to load changes. The power reference value for the second port is the surplus power in the current DC microgrid system; when P 3min ≤P PV_s <P 3n The third port operates at the power reference value P. 3ref =P PV_s The second port responds to load changes; the DC microgrid system has no surplus power, and the power reference value at the second port is 0; when P PV_s <P 3min To reduce the number of start-ups and shutdowns of the electrolytic cell, the power reference value P at the third port is... 3ref =P 3min The second port responds to load changes and provides the required power P in the DC microgrid system. 2ref =P 3min -P PV_s The upper-level controller's power reference value P for the third port 3ref Slope limiting is applied to obtain the final power reference value; the charging and discharging safety of the second port is guaranteed by the upper-level controller; when the load suddenly increases, P d >0, based on the aforementioned method, re-determine the selection of the port's power reference value.

[0031] The beneficial effects of this invention are as follows: This invention can dynamically adjust the power of each port of the three-port DC transformer according to the power capacity of each port, the state of charge of the energy storage system, and the dynamic response speed of the electrolytic hydrogen production. It can smooth the power fluctuation in the system by coordinating the electrolytic hydrogen production and energy storage, and coordinate the power distribution between energy storage and electrolytic cells to achieve efficient utilization of renewable energy. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the hydrogen-electrically coupled DC microgrid system of the present invention;

[0033] Figure 2 This is a schematic diagram of the three-port converter hydrogen storage coordinated control method of the present invention;

[0034] Figure 3 This is a flowchart of the three-port converter hydrogen storage coordinated control method of the present invention. Detailed Implementation

[0035] To make the objectives and technical solutions of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0036] like Figure 1 The diagram shows a partial schematic of a hydrogen-electric coupling DC microgrid system. This system includes a ±10kV medium-voltage DC bus and a ±375V low-voltage DC bus. In this system, the first port of the three-port DC transformer is connected to the load via the medium-voltage straight bus and is a free port. The second port of the three-port DC transformer is connected to the energy storage device via the low-voltage straight bus and is in power control mode. The third port of the three-port DC transformer is connected to the electrolyzer and is also in power control mode. The three-port DC transformer is a key device coordinating the electrolyzer and the energy storage device. Figure 1 The schematic diagram shown illustrates the hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method of the present invention.

[0037] The coordinated control method includes: collecting the photovoltaic power generation power and the medium-voltage DC bus load demand power in the DC microgrid system connected to the first port, and taking the power difference; coordinating the power distribution between the second port and the third port based on the power difference; collecting the actual power values ​​of the second port and the third port of the three-port DC transformer, and comparing them with the power reference values ​​of the second port and the third port of the three-port DC transformer respectively to obtain the power difference between the second port and the third port; establishing the relationship between the shift ratio of the three-port DC transformer and the power difference between the second port and the third port, and adjusting the shift ratio of the second port and the third port based on the relationship between the power difference between the second port and the third port and the shift ratio.

[0038] The relationship between the shift ratio of the three-port DC transformer and the power difference between the second and third ports is as follows: the difference between the power reference value and the actual power value of each port, after passing through a PI circuit, outputs the shift ratio of each port. Figure 2 As shown.

[0039] The specific details of coordinating the power distribution between the second and third ports are as follows:

[0040] The power reference values ​​for the second and third ports are:

[0041] When the power difference is greater than 0 and greater than or equal to the rated power of the third port: if the state of charge of the second port is less than or equal to its maximum state of charge, the power reference value of the third port is its rated power, and the power reference value of the second port is the difference between the power difference and the rated power of the third port; otherwise, the reference power of the second port is 0, and the power reference value of the third port is its rated power.

[0042] When the power difference is greater than 0 and less than the rated power of the third port, but greater than or equal to the minimum operating power of the third port: the power reference value of the third port is the power difference, and the power reference value of the second port is 0.

[0043] When the power difference is greater than 0 and less than the minimum operating power of the third port: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is the minimum operating power of the third port, and the power reference value of the second port is the difference between the power difference and the minimum operating power of the third port; otherwise, the reference power value of the third port is 0, and the power reference value of the second port is 0.

[0044] When the power difference is equal to 0: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is its minimum operating power, and the power reference value of the second port is the power reference value of the third port; otherwise, the reference power of the third port is 0, and the reference power of the second port is 0.

[0045] When the power difference is less than 0: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is its minimum operating power, and the power reference value of the second port is the difference between the power difference and the minimum operating power of the third port; otherwise, the reference power of the third port is 0, and the reference power of the second port is 0.

[0046] When a load change occurs, based on the above situation, the power reference value of the third port remains unchanged, and the power reference value of the second port is the difference between the original power reference value and the load change amount.

[0047] Specifically, the actual operation mode of the hydrogen-electric coupled DC microgrid system (hereinafter referred to as the system) has the following 8 modes.

[0048] Mode 1: When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G There are no sudden load changes, and the excess photovoltaic output is greater than or equal to the rated power P of the electrolysis hydrogen production. 3n .

[0049] Mode 2: When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G There is no sudden load change, and the excess photovoltaic output is less than the rated power P of the electrolysis hydrogen production. 3n The minimum operating power P required for hydrogen production by electrolysis is greater than or equal to that specified in the manual description. 3min .

[0050] Mode 3: When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G No load abrupt change, excess photovoltaic output P PV_s Less than the minimum operating power P for hydrogen production by electrolysis 3min .

[0051] Mode 4: When the output P of the photovoltaic power generation system in the system PV Equal to the load P on the grid side G There are no sudden load changes and no excess power is used for hydrogen production by electrolysis.

[0052] Mode 5: When the output P of the photovoltaic power generation system in the system PV Less than the medium load P on the grid side G .

[0053] Mode 6: When the output P of the photovoltaic power generation system in the system... PV Greater than the medium load P on the grid side G There is a load mutation.

[0054] Mode 7: When the output P of the photovoltaic power generation system in the system PV Equal to the load P on the grid sideG There is a load mutation.

[0055] Mode 8: When the output P of the photovoltaic power generation system in the system PV Less than the medium load P on the grid side G There is a load mutation.

[0056] In this embodiment, the three-port DC transformer employs single-phase-shift control, where power transfer between ports is controlled by phase difference, resulting in two degrees of freedom among the three ports. Therefore, in practical control, one port needs to be designated as a free port, controlling only the voltage, current, and power of the remaining ports. Using the first port as a reference, the ratios of the H-bridge square wave phases corresponding to the three ports of the three-port DC transformer to π are denoted as phase ratios D1, D2, and D3. The phase shift ratio between the second port and the first port is defined as d. 21 The shift ratio between the third port and the first port is d. 31 .

[0057]

[0058] The process of the coordination and control methods of the above eight modes is as follows: Figure 3 As shown, the coordination control methods for the eight modes are described in detail below.

[0059] I. Coordination and Control Methods in Mode 1

[0060] When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G Unloaded mutation amount P d And excess photovoltaic output P PV_s Greater than the rated power P of hydrogen production by electrolysis 3n hour:

[0061] P pv_s =(P pv -P G )≥P 3n

[0062] To achieve maximum utilization of renewable energy, the power reference value for the third port is as follows:

[0063] P 3ref =P 3n

[0064] The surplus power in the system after electrolysis for hydrogen production is:

[0065] P a =P pv -P G -P 3n

[0066] Based on the real-time SOC status of the energy storage device, the output range of the energy storage device is:

[0067] P 2min ≤P2≤P 2max

[0068] At this time, the power reference value for the second port is:

[0069] P 2ref =P a

[0070] The power reference value of the second port should be within the power limit allowed by the second port, when the SOC during charging reaches the maximum SOC of the energy storage device. max When charging is prohibited, the maximum power P that the energy storage device is allowed to absorb is... 2max =0.

[0071] The product P2 of the voltage U2 at the second port and the current I2 at the second port is collected, along with the power reference value P sent to the second port. 2ref Subtraction, followed by a PI regulator, yields the shift ratio d between the second port and the first port. 21 When the SOC of the energy storage device = SOC max When this occurs, the energy storage device prohibits charging, sends an alarm to the upper-level controller, and limits photovoltaic output. The power command P at the third port is then transmitted. 3ref After slope limiting, the power command is subtracted from the actual power value P3 acquired at the third port, and then passed through another PI regulator to obtain the shift ratio d between the third port and the first port. 31 .

[0072] II. Coordination and Control Methods in Mode 2

[0073] When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G Excess photovoltaic output P PV_s Less than the rated power P of hydrogen production by electrolysis 3n The minimum operating power P required for hydrogen production by electrolysis is greater than or equal to that specified in the manual description. 3min hour:

[0074] P 3min ≤(P pv_s =P pv -P G ) <P 3n

[0075] To achieve maximum utilization of renewable energy, the power reference value for the third port is as follows:

[0076] P 3ref =P pv_s

[0077] At this point, the surplus power in the system used for hydrogen production via electrolysis is:

[0078] P a =P pv -P G -P 3ref

[0079] The power reference value for the second port is:

[0080] P 2ref =P a =0

[0081] The second port does not participate in power transmission in the system; its power transmission is 0. The upper-level controller sends P to the second port. 2ref Subtracting the actual power P2 at the second port from the shift ratio d by the PI regulator yields the shift ratio d. 21 At this time, the power reference value P at the third port... 3ref For P PV -P G The power command P on the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref Subtraction, followed by a PI circuit, yields the shift ratio d between the third port and the first port. 31 .

[0082] III. Coordination and Control Methods for Mode 3

[0083] When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G Excess photovoltaic output P PV_s Less than the minimum operating power P for hydrogen production by electrolysis 3min hour:

[0084] (P pv_s =P pv -P G ) <P 3min

[0085] When the state of charge at the second port is greater than or equal to the minimum state of charge, frequent start-ups and shutdowns of the electrolytic cell not only increase system energy consumption but also affect the cell's lifespan. Therefore, it is necessary to maintain the electrolytic cell in minimum power mode to reduce the number of start-ups and shutdowns. The minimum power required by the electrolytic cell is P. 3min The energy storage device needs to compensate for the power difference to ensure that the electrolyzer operates in minimum power mode.

[0086] At this time, the power reference value for the second port is:

[0087] P2ref =P 3min -(P pv -P G )

[0088] The power reference value for the third port is:

[0089] P 3ref =P 3min

[0090] When the state of charge at the second port is less than the minimum state of charge, the power reference value at the second port is:

[0091] P 2ref =0

[0092] The power reference value for the third port is:

[0093] P 3ref =0

[0094] The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller. 21 The power command P on the third port. 3ref Slope limiting is applied, and the actual power value P3 at the third port is compared with the reference value P. 3ref The shift ratio d is obtained after subtraction and then passed through a PI controller. 31 When the second port of the SOC <SOC min At that time, the energy storage device stops discharging and exits operation, and the electrolytic cell also exits operation.

[0095] IV. Coordination and Control Methods for Mode 4

[0096] When the output P of the photovoltaic power generation system in the system PV Equal to the load P on the grid side G When there is no spare power for hydrogen production by electrolysis

[0097] P pv_s =P pv -P G =0

[0098] When the state of charge at the second port is greater than or equal to the minimum state of charge, frequent start-ups and shutdowns of the electrolytic cell not only increase system energy consumption but also affect the cell's lifespan. Therefore, it is necessary to maintain the electrolytic cell in minimum power mode to reduce the number of start-ups and shutdowns. The minimum power required by the electrolytic cell is P. 3min Since all the photovoltaic output in the system is used for loads on the grid side, the minimum power required by the electrolyzer is provided by the energy storage device.

[0099] At this time, the power reference value of the third port is:

[0100] P 3ref =P 3min

[0101] The power reference value for the second port is:

[0102] P 2ref =P 3min

[0103] When the state of charge at the second port is less than the minimum state of charge,

[0104] At this time, the power reference value for the second port is:

[0105] P 2ref =0

[0106] The power reference value for the third port is:

[0107] P 3ref =0

[0108] The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller. 21 The power command P on the third port. 3ref Slope limiting is applied, and the actual power value P3 at the third port is compared with the reference value P. 3ref The shift ratio d is obtained after subtraction and then passed through a PI controller. 31 When the SOC of the second port is less than or equal to the SOC of the second port. min At that time, the energy storage device stops discharging and exits operation, and the electrolytic cell also exits operation.

[0109] V. Coordination and Control Methods for Mode 5

[0110] When the output P of the photovoltaic power generation system in the system PV Less than the medium load P on the grid side G ;

[0111] P pv_s =P pv -P G <0

[0112] Photovoltaic output P in the system PV All used for load P on the grid side G The energy storage device at the second port is partly used to provide the minimum power P to the electrolyzer. 3min Another part is used to provide photovoltaic power output P PV With load P in the power grid G The difference P pv_s P pv_s =P PV -P G .

[0113] The power reference value for the second port is:

[0114] P 2ref =|P pv -P G |+P 3min

[0115] The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller. 21 The control method for the third port is the same as in mode 3. When the SOC of the second port is less than or equal to the SOC... min When the energy storage device shuts down, it sends a warning to the upper-level controller, cuts off the load, and the electrolytic cell shuts down.

[0116] VI. Coordination and Control Methods for Mode 6

[0117] When the output P of the photovoltaic power generation system in the system PV Greater than the medium load P on the grid side G And there is a load mutation amount P d .

[0118] (1) When the load suddenly increases, P d >0

[0119] Surplus power in the system:

[0120] P pv_s =P pv -P G -P d

[0121] When P pv_s ≥P 3n The system is still operating in mode 1. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 1.

[0122] When P 3min ≤P pv_s <P 3n The system is operating in mode 2. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 2. The power reference value of the third port is also updated in mode 2.

[0123] When P pv_s <P 3min The system is running in mode 3. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 2. The power reference value of the third port is also updated in mode 2.

[0124] (2) When the load suddenly decreases, Pd <0

[0125] Based on the method in (1), the selection of the mode is determined.

[0126] VII. Coordination and Control Methods for Mode 7

[0127] When the output P of the photovoltaic power generation system in the system PV Equal to the load P on the grid side G And there is a load mutation amount P d .

[0128] (1) When the load suddenly decreases, P d <0

[0129] Surplus power in the system:

[0130] P pv_s =P pv -P G -P d

[0131] When P pv_s ≥P 3n The system is still operating in mode 1. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 1.

[0132] When P 3min ≤P pv_s <P 3n The system is operating in mode 2. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 2. The power reference value of the third port is also updated in mode 2.

[0133] When P pv_s <P 3min The system is running in mode 3. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 2. The power reference value of the third port is also updated in mode 2.

[0134] (2) When the load suddenly increases, P d >0

[0135] The system transitions from mode 4 to mode 5.

[0136] VIII. Coordination and Control Methods for Mode 8

[0137] When the output P of the photovoltaic power generation system in the system PV Less than the medium load P on the grid side G And there is a load mutation amount P d .

[0138] (1) When the load suddenly decreases, Pd <0

[0139] Surplus power in the system:

[0140] P pv_s =P pv -P G -P d

[0141] When P pv_s ≥P 3n The system is still operating in mode 1. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 1.

[0142] When P 3min ≤P pv_s <P 3n The system is operating in mode 2. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 2. The power reference value of the third port is also updated in mode 2.

[0143] When P pv_s <P 3min The system is running in mode 3. The second port responds to load changes, and the power reference value of the second port is updated in the calculation of mode 2. The power reference value of the third port is also updated in mode 2.

[0144] (2) When the load suddenly increases, P d >0

[0145] The system remains in mode 5, with the second port responding to rapid load changes.

[0146] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for coordinated control of hydrogen storage in a hydrogen-electrically coupled three-port DC transformer, characterized in that, The first port of the three-port DC transformer is connected to the load via the medium-voltage DC bus in the DC microgrid system and is a free port; the second port of the three-port DC transformer is connected to the energy storage device via the low-voltage DC bus in the DC microgrid system and is in power control mode; the third port of the three-port DC transformer is connected to the electrolytic cell and is in power control mode. The aforementioned coordination and control method includes: The photovoltaic power generation and the medium-voltage DC bus load demand in the DC microgrid system connected to the first port are collected, and the power difference is calculated; based on the power difference, the power allocation between the second port and the third port is coordinated. The actual power values ​​of the second and third ports of the three-port DC transformer are collected and compared with the power reference values ​​of the second and third ports of the three-port DC transformer, respectively, to obtain the power difference between the second and third ports; Establish the relationship between the shift ratio of the three-port DC transformer and the power difference between the second and third ports. Based on the relationship between the power difference between the second and third ports and the shift ratio, adjust the shift ratio of the second and third ports. When the output P of the photovoltaic power generation system in the DC microgrid system PV Greater than the medium load P on the grid side G Unloaded mutation amount P d Excess photovoltaic output P PV_s Less than the minimum operating power P of the third port 3min When the state of charge at the second port is less than the minimum state of charge, the upper-level controller sends the power reference value P to the third port. 3ref =0, the power reference value P at the second port 2ref =0; When the state of charge at the second port is greater than or equal to the minimum state of charge, the minimum power required by the electrolytic cell is P. 3min The upper-level controller sends the power reference value P to the third port. 3ref =P 3min For the power reference value P 3ref After slope limiting, the final power command for the third port is obtained; the power reference value for the second port is: P 2ref =P 3min -(P PV -P G The energy storage device automatically replenishes the power difference, enabling the electrolyzer to operate in minimum power mode; The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller. 21 The power reference value P at the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref The shift ratio d is obtained after subtraction and then passed through a PI controller. 31 When the SOC of the second port is less than or equal to the SOC min At that time, the energy storage device stops discharging and exits operation, and the electrolytic cell also exits operation.

2. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, The relationship between the shift ratio of the three-port DC transformer and the power difference between the second and third ports is as follows: the difference between the power reference value and the actual power value of each port is passed through a PI circuit to output the shift ratio of each port. The power reference values ​​for the second and third ports are: When the power difference is greater than 0 and greater than or equal to the rated power of the third port: if the state of charge of the second port is less than or equal to its maximum state of charge, the power reference value of the third port is its rated power, and the power reference value of the second port is the difference between the power difference and the rated power of the third port; otherwise, the reference power of the second port is 0, and the power reference value of the third port is its rated power. When the power difference is greater than 0 and less than the rated power of the third port, but greater than or equal to the minimum operating power of the third port: the power reference value of the third port is the power difference, and the power reference value of the second port is 0. When the power difference is greater than 0 and less than the minimum operating power of the third port: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is the minimum operating power of the third port, and the power reference value of the second port is the difference between the power difference and the minimum operating power of the third port. Otherwise, the reference power value of the third port is 0, and the power reference value of the second port is 0; When the power difference is equal to 0, if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is its minimum operating power, and the power reference value of the second port is the power reference value of the third port; otherwise, the reference power of the third port is 0, and the reference power of the second port is 0. When the power difference is less than 0: if the state of charge of the second port is greater than or equal to the minimum state of charge, the power reference value of the third port is its minimum operating power, and the power reference value of the second port is the difference between the power difference and the minimum operating power of the third port. Otherwise, the reference power of the third port is 0, and the reference power of the second port is 0; When a load change occurs, based on the above situation, the power reference value of the third port remains unchanged, and the power reference value of the second port is the difference between the original power reference value and the load change amount.

3. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1 or 2, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Greater than the medium load P on the grid side G Unloaded mutation amount P d And excess photovoltaic output P PV_s The rated power P of hydrogen production by electrolysis is greater than or equal to that of hydrogen production. 3n Time: To achieve maximum utilization of renewable energy, the power reference value of the third port is set to the rated power P of the third port. 3n At this time, the surplus power in the DC microgrid system is absorbed by the energy storage device, and the power reference value P at the second port... 2ref It should be within the power limit allowed by the second port power, i.e., P 2min ≤P 2ref ≤P 2max P 2max With P 2min These represent the maximum and minimum charge / discharge power allowed at the second port, respectively. When the SOC during charging reaches the maximum SOC of the energy storage device max When charging is in progress, the energy storage device is prohibited from charging, and the power reference value of the second port is 0; when the SOC during charging has not reached the maximum SOC of the energy storage device. max At that time, the power reference value of the second port is the excess photovoltaic output and the rated power P of the third port. 3n The difference; The product of the voltage U2 at the second port and the current I2 at the second port, P2, and the power reference value P sent to the second port. 2ref Subtraction, followed by a PI regulator, yields the shift ratio d between the second port and the first port. 21 When the SOC of the energy storage device = SOC max When this occurs, the energy storage device prohibits charging, sends an alarm to the upper-level controller, and limits photovoltaic output; the power reference value P at the third port is then... 3ref Slope limiting is applied, and the power reference value P is used. 3ref After subtracting the actual power value P3 collected at the third port, the result is passed through another PI regulator to obtain the shift ratio d between the third port and the first port. 31 .

4. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Greater than the medium load P on the grid side G Unloaded mutation amount P d And excess photovoltaic output P PV_s Less than the rated power P of the third port 3n The minimum operating power P defined by the third port is greater than or equal to that of the third port. 3min At this time, to achieve the maximum utilization rate of renewable energy, the power reference value at the third port is the excess photovoltaic output P. PV_s In the DC microgrid system, the surplus power after electrolysis for hydrogen production is 0, and the power reference value of the second port is 0. The second port does not participate in power transmission in the DC microgrid system. Excess photovoltaic output is used entirely for hydrogen electrolysis. The second port transmits zero power, and the upper-level controller sends P to the second port. 2ref Subtracting the actual power value P2 from the second port, the shift ratio d is obtained after passing through a PI regulator. 21 At this time, the power reference value P of the third port 3ref For P PV -P G The power reference value P at the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref Subtracting the first and second parts, and passing through another PI regulator, we obtain the shift ratio d between the third port and the first port. 31 .

5. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Equal to the load P on the grid side G Unloaded mutation amount P d When there is no excess power for hydrogen electrolysis: when the state of charge at the second port is less than the minimum state of charge, the power reference value P at the third port is... 3ref =0, the power reference value of the second port is: P 2ref =0; When the state of charge at the second port is greater than or equal to the minimum state of charge, the electrolytic cell needs to be maintained in minimum power mode to reduce the number of start-ups and shutdowns. The minimum power required by the electrolytic cell is P. 3min Since all the photovoltaic output in the system is used for loads on the grid side, the minimum power required by the electrolyzer is provided by the energy storage device. In this case, the power reference value at the third port is: P 3ref =P 3min The power reference value P at the third port 3ref After slope limiting, the final power command for the third port is obtained. The power reference value for the second port is: P 2ref =P 3min The energy storage device provides the required power for the third port; The actual power value P2 of the second port is collected and compared with the power reference value P. 2ref After subtraction, the phase shift angle d is obtained after passing through a PI controller. 21 The power reference value P at the third port 3ref Slope limiting is applied, and the actual power value P3 and the power reference value P at the third port are collected. 3ref The shift ratio d is obtained after subtraction and then passed through a PI controller. 31 ; When the SOC of the second port ≤ SOC min At that time, the energy storage device stops discharging and exits operation, and the electrolytic cell also exits operation.

6. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Less than the medium load P on the grid side G Unloaded mutation amount P d Time: Output P of the photovoltaic power generation system in the DC microgrid system PV All used for load P on the grid side G When the state of charge at the second port is less than the minimum state of charge, the power reference value P at the third port... 3ref =0, the power reference value of the second port is: P 2ref =0; When the state of charge at the second port is greater than or equal to the minimum state of charge, a portion of the energy storage device at the second port provides the minimum power P to the electrolyzer. 3min The other part provides the output P of the photovoltaic power generation system. PV With load P in the power grid G The difference is P PV_s P PV_s =P PV -P G The power reference value for the second port is: The upper-level controller will use the power reference value P at the second port. 2ref The power is sent to the DC transformer at the third port to control the energy storage device to replenish the power difference. In this mode, the charging and discharging safety of the second port is guaranteed by the upper-level controller, and the power reference value P of the third port is used. 3ref Operating at minimum power P 3min P 3ref =P 3min The upper-level controller sends the power reference value P to the third port. 3ref The final power command for the third port is obtained after slope limiting.

7. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Greater than the medium load P on the grid side G The load mutation amount P d Time: When the load suddenly increases, P d >0, calculate the relationship between the surplus power in the DC microgrid system and the power required by the electrolytic cell; when P PV_s ≥P 3n P PV_s =P PV -P G The third port operates at maximum power, while the second port responds to load changes. The power reference value for the second port is the surplus power in the current DC microgrid system; when P 3min ≤P PV_s <P 3n The third port operates at the power reference value P. 3ref = P PV_s The second port responds to load changes; the DC microgrid system has no surplus power, and the power reference value at the second port is 0; when P PV_s <P 3min To reduce the number of start-ups and shutdowns of the electrolytic cell, the power reference value P at the third port is... 3ref =P 3min ; The second port responds to load changes and provides the required power P in the DC microgrid system. 2ref =P 3min -P PV_s The upper-level controller's power reference value P for the third port 3ref Slope limiting is applied to obtain the final power reference value; the charging and discharging safety of the second port is guaranteed by the upper-level controller; when the load suddenly decreases, P d If the value is less than 0, the selection of the power reference value for the port is re-evaluated based on the aforementioned method.

8. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Equal to the load P on the grid side G The load mutation amount P d Time: When the load suddenly decreases, P d <0, calculate the surplus power P in the DC microgrid system. PV_s The relationship between P and the power required by the electrolytic cell; when P PV_s ≥P 3n The third port operates at maximum power, while the second port responds to load changes. The power reference value for the second port is the surplus power in the current DC microgrid system; when P 3min ≤P PV_s <P 3n The third port operates at the power reference value P. 3ref =P PV_s The second port responds to load changes; the DC microgrid system has no surplus power, and the power reference value at the second port is 0; when P PV_s <P 3min To reduce the number of start-ups and shutdowns of the electrolytic cell, the power reference value P at the third port is... 3ref =P 3min ; The second port responds to load changes and provides the required power P in the DC microgrid system. 2ref =P 3min -P PV_s The upper-level controller's power reference value P for the third port 3ref Slope limiting is applied to obtain the final power reference value; the charging and discharging safety of the second port is guaranteed by the upper-level controller; when the load suddenly increases, P d >0, based on the aforementioned method, re-determine the selection of the port's power reference value.

9. The hydrogen-electric coupling three-port DC transformer hydrogen storage coordinated control method according to claim 1, characterized in that, When the output P of the photovoltaic power generation system in the DC microgrid system PV Less than the medium load P on the grid side G The load mutation amount P d Time: When the load suddenly decreases, P d <0, calculate the surplus power P in the DC microgrid system. PV_s The relationship between P and the power required by the electrolytic cell; when P PV_s ≥P 3n The third port operates at maximum power, while the second port responds to load changes. The power reference value for the second port is the surplus power in the current DC microgrid system; when P 3min ≤P PV_s <P 3n The third port operates at the power reference value P. 3ref = P PV_s The second port responds to load changes; the DC microgrid system has no surplus power, and the power reference value at the second port is 0; when P PV_s <P 3min To reduce the number of start-ups and shutdowns of the electrolytic cell, the power reference value P at the third port is... 3ref =P 3min The second port responds to load changes and provides the required power P in the DC microgrid system. 2ref =P 3min -P PV_s The upper-level controller's power reference value P for the third port 3ref Slope limiting is applied to obtain the final power reference value; the charging and discharging safety of the second port is guaranteed by the upper-level controller; when the load suddenly increases, P d >0, based on the aforementioned method, re-determine the selection of the port's power reference value.

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