CN113612256A - Renewable energy direct-current micro-grid hydrogen production black start optimization method - Google Patents

Abstract

The invention relates to a renewable energy direct-current micro-grid hydrogen production black start optimization method, which comprises the following steps: (1) before executing a system black start command, judging whether the stored energy can meet the condition of being used as a system black start power supply at the moment, if so, executing (2), otherwise, executing (8); (2) the energy storage system is used as a black start power supply and executes a system black start mode; (3) the wind turbine generator and the hydrogen production electrolytic cell auxiliary equipment recover power supply; (4) judging the optimal equipment investment sequence at the next moment based on an optimization control algorithm; (5) sequentially starting the equipment according to the optimal starting sequence; (6) hydrogen production is started when the temperature of the hydrogen production electrolytic cell reaches the hot standby working condition; (7) completing the black start of the system; (8) the photovoltaic power generation unit is used as a black start power supply; (9) charging the low SOC energy storage system by the photovoltaic power generation unit; (10) if the light storage unit meets the conditions, the wind turbine generator and the hydrogen production electrolytic cell auxiliary equipment are recovered to supply power; and (4) executing the step.

Description

Renewable energy direct-current micro-grid hydrogen production black start optimization method

Technical Field

The invention relates to the field of electric power, in particular to a renewable energy direct-current micro-grid hydrogen production black start optimization method.

Background

In recent years, hydrogen energy is used as a clean, efficient and sustainable secondary energy, and is subjected to national key support cultivation and vigorous development. Meanwhile, with the promotion of the development planning of national renewable energy sources, the permeability of distributed renewable energy sources is continuously improved. However, due to the fluctuation of wind power and photovoltaic power generation, the output power is extremely unbalanced, the consumption capacity of a power grid to renewable energy sources is very limited, the phenomena of severe wind abandoning and light abandoning are caused, the consumption of the renewable energy sources can be effectively realized by taking hydrogen production equipment as a load, the wind abandoning and light abandoning are effectively reduced, and the hydrogen production cost is reduced at the same time. Therefore, the hydrogen production by renewable energy can realize the urgent needs of urban environment and energy transformation, and further promote the development of the hydrogen energy industry.

A typical renewable energy direct current microgrid hydrogen production structure is shown in fig. 1. Compared with a large power grid, the renewable energy direct-current micro-grid hydrogen production system is low in stability. Due to the wind and light fluctuation characteristics of the micro-grid, the energy storage system in the micro-grid plays a role in continuously supplying power for important loads and maintaining the stability of the system. Unreasonable load distribution and extreme weather conditions will result in the energy storage system shutting down as the battery empties. In addition, due to the limitation of the capacity and the support margin of the energy storage system, when an external power grid fails, power grid protection actions and power loss of a total station are often generated. Patent CN 104318317A, CN 103986186A is based on a renewable energy microgrid system, and provides a corresponding black start scheme and an optimization method, but the dynamic characteristic of a hydrogen production load cannot be considered. Patent CN 111668862 a proposes an energy storage system black start sequence control method, but fails to combine with new energy output prediction data to realize optimization of the black start scheme and enhance the adaptability of the scheme to different situations.

Disclosure of Invention

The renewable energy direct-current micro-grid hydrogen production system has a prominent stability problem due to the limitations of the output fluctuation of the renewable energy and the energy storage capacity of the system. The system is particularly sensitive to stability problems caused by large grid faults and extreme weather problems. In order to solve the technical problems, the invention provides a black-start sequence control optimization method for a renewable energy direct-current micro-grid hydrogen production system, which can safely, reliably and quickly recover the normal work of the system under the failure of the micro-grid system, provide innovative solutions and optimization schemes for important load power supply, improve the safety and reliability of the micro-grid system and the hydrogen production efficiency, and further promote the continuous development of renewable energy and hydrogen energy industries in China.

The technical scheme of the invention is as follows: a renewable energy direct-current micro-grid hydrogen production black start optimization method comprises the following steps:

(1) before the system black start command is executed, the energy storage unit SOC at the current t0 moment is read_t0Judging whether the stored energy can meet the condition of being used as a system black start power supply at the moment, and executing the step (2) if the stored energy can meet the condition; otherwise, executing the step (8);

(2) the energy storage system is used as a black start power supply to execute a system black start mode, and the energy storage unit works in a constant voltage mode at the moment and is used for maintaining the voltage of the direct current bus;

(3) the wind turbine generator and the hydrogen production electrolytic cell auxiliary equipment recover power supply;

(4) judging the optimal equipment investment sequence at the next moment based on an optimization control algorithm according to the wind and light prediction data and the optimization objective function;

(5) solving the optimized objective function in the step (4) to obtain an optimal equipment starting sequence, and sequentially starting the equipment to be merged into the microgrid system according to the obtained optimal starting sequence;

(6) judging whether the temperature of the hydrogen production electrolytic cell reaches a hot standby working condition, if not, waiting until the system meets a hot start condition, and the hydrogen production electrolytic cell starts to receive a system scheduling instruction to produce hydrogen, wherein the electrolytic cell works in a constant-current control mode, the wind-solar power generation unit works in a power limiting mode, and the upper-layer coordination control system regulates the output of each unit in the microgrid according to a power conservation principle;

(7) completing the black start of the system;

(8) the photovoltaic power generation unit is used as a black start power supply, works in a constant voltage mode and is used for maintaining the voltage of the direct current bus;

(9) the energy storage system at the next moment is put into operation, and the photovoltaic power generation unit charges the low SOC energy storage system;

(10) judging whether the light storage unit can meet the preset power supply condition at the next moment t, and if the light storage unit meets the preset power supply condition, recovering the power supply of the wind power generator set and the hydrogen production electrolytic cell auxiliary equipment in the system; next, executing the optimization control algorithm in the step (4); adding a constraint condition: otherwise, returning to the step (8), and continuously charging the energy storage system by the photovoltaic power generation unit.

Further, the conditions are:

P_dis(t₀)≥P_sup

wherein P is_dis(t₀) For the maximum discharge power of the energy storage unit at the time t0, the specific expression is as follows:

SOC_lowfor the lower limit value SOC of the energy storage unit SOC_t0The SOC of the energy storage unit at the time t0 is shown, and delta t is a preset time interval; eta_disTo discharge efficiency; e_batRated capacity for energy storage;

the maximum discharge power allowed for the energy storage system; p_supIn order to ensure the total power required by the power supply of auxiliary equipment for normal operation of equipment in a system, the specific expression is as follows:

P_sup＝P_{sup_wind}+P_{h2_sup}

P_{sup_wind}and P_{h2_sup}And the power required by power supply is respectively supplied to auxiliary equipment for ensuring normal operation of the wind turbine generator and the hydrogen production electrolytic cell.

Further, the step (4) specifically includes:

the optimization objective function takes the most important load, namely the fastest recovery power supply of the hydrogen production electrolytic cell, as an optimization objective, and the specific function expression is as follows:

wherein T is the total time period number of the operation of the optimization objective function, gamma is a binary variable and represents all start-stop state sets of the hydrogen production electrolytic cell in the time period T, 1 represents that the unit is in a working state at the moment, and 0 represents that the unit is in a shutdown state at the moment;

in addition, binary variables alpha and beta are set to respectively correspond to all start-stop state sets of the wind turbine generator and the photovoltaic power generation unit in a T time period, the meanings represented by 1 and 0 are the same as gamma, and all equipment are in a stop state at the initial moment, namely:

α(0)＝β(0)＝γ(0)＝0

at each calculation time t, α, β and γ, the following constraints have to be satisfied:

meanwhile, in order to ensure that the wind-solar power generation unit and the hydrogen production electrolytic cell start the access system one by one and prevent the bus voltage from overlarge fluctuation caused by simultaneously merging a plurality of devices into the system, the alpha, the beta and the gamma also need to meet the following constraint conditions:

α(t)-α(t-1)+β(t)-β(t-1)+γ(t)-γ(t-1)≤1

besides, the system needs to satisfy the power balance constraint conditions during operation, namely:

α(t)(P_PV(t)-P_{sup_pV})+β(t)P_wind(t)-P_{sup_wind}+P_bat(t)-γ(t)P_{h2_hot}-P_{h2_sup}＝0

wherein P is_PV(t)、P_wind(t) predicting output of photovoltaic power and wind power at the moment t respectively; p_{sup_PV}The power required by the work of a DC/DC converter corresponding to the photovoltaic power generation unit is directly obtained from the photovoltaic PV assembly; p_{h2_hot}Power, P, required for the cell to reach hot standby conditions_bat(t) is the charge-discharge power of the energy storage system at the moment t, and the specific expression is as follows:

wherein the content of the first and second substances,

and

the binary variables respectively represent the charging and discharging states of the stored energy and meet the following constraint conditions:

P_ch(t) and P_dis(t) the energy storage charging and discharging power at the moment t respectively meets the following constraint conditions:

wherein the content of the first and second substances,

for the maximum limit of the stored energy charging power,

and the maximum limit value of the energy storage discharge power is obtained.

Further, in the step (6), the upper layer coordination control system adjusts the output of each unit in the microgrid according to the power conservation principle, and the following conditions are met:

P_{PV_ref}(t)-P_{sup_PV}+P_{wind_ref}(t)-P_{sup_wind}+P_bat(t)-P_{h2_ref}(t)-P_{h2_sup}＝0 (6)

wherein P is_{PV_ref}(t)、P_{wind_ref}(t)、P_{h2_ref}And (t) respectively controlling the photovoltaic, the fan and the hydrogen production electrolytic cell scheduling instructions issued by the coordination system at the moment t.

Further, in the step (10), the predetermined power supply condition is:

P_dis(t)+P_PV(t)-P_{sup_PV}≥P_sup(ii) a The constraint condition is that α (0) is 1.

Has the advantages that:

the invention provides a black start optimization method suitable for a renewable energy direct-current micro-grid hydrogen production system, which ensures that the important load of the system, namely hydrogen production electrolytic cell power supply, can be safely, reliably and quickly restored under the fault condition of the micro-grid system, and improves the stability, reliability and hydrogen production efficiency of the system. One of the innovations of the invention is to consider the dynamic characteristic of the hydrogen production load, and provide an optimal equipment investment scheme which takes the fastest recovery of the power supply of the hydrogen production load as an optimization target and makes a decision and judgment on the fastest recovery of the power supply of the hydrogen production load based on future wind-solar power generation prediction data for preventing potential safety hazards caused by long-time power loss of the hydrogen production load. The safety and the reliability of the black start scheme are improved. Meanwhile, various initial conditions and future weather conditions are considered, a targeted black-start equipment operation scheme is provided, and black-start flexibility and feasibility of the microgrid system are improved.

Drawings

FIG. 1 is a schematic block diagram of renewable energy direct current micro-grid hydrogen production;

fig. 2 is a schematic flow diagram of a renewable energy direct-current microgrid hydrogen production black-start optimization method.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the present invention without creative efforts.

According to an embodiment of the invention, a black start optimization method for hydrogen production by a renewable energy direct current microgrid is provided, as shown in fig. 2, and is characterized by comprising the following steps:

(1) before the system black start command is executed, the energy storage unit SOC at the current t0 moment is read_t0And judging whether the stored energy can meet the condition of being used as a system black start power supply at the moment. Namely:

P_dis(t₀)≥P_sup

wherein P is_dis(t₀) For the maximum discharge power of the energy storage unit at the time t0, the specific expression is as follows:

SOC_lowthe lower limit value of the SOC of the energy storage unit; eta_disTo discharge efficiency; e_batRated capacity for energy storage;

the maximum discharge power allowed for the energy storage system; p_supIn order to ensure the total power required by the power supply of auxiliary equipment for normal operation of equipment in a system, the specific expression is as follows:

P_sup＝P_{sup_wind}+P_{h2_sup}

P_{sup_wind}and P_{h2_sup}And the power required by power supply is respectively supplied to auxiliary equipment for ensuring normal operation of the wind turbine generator and the hydrogen production electrolytic cell.

If the condition is met, executing the step (2); otherwise, executing step (8).

(2) The energy storage system is used as a black start power supply to execute a system black start mode. At this time, the energy storage unit works in a constant voltage mode and is used for maintaining the voltage of the direct current bus.

(3) And the wind turbine generator and the hydrogen production electrolytic cell auxiliary equipment recover power supply.

(4) And judging the optimal equipment investment sequence at the next moment according to the wind and light prediction data and the optimization objective function.

The optimization objective function takes the most important load, namely the fastest recovery power supply of the hydrogen production electrolytic cell, as an optimization objective, and the specific function expression is as follows:

wherein T is the total time period number of the operation of the optimization objective function, and gamma is a binary variable, and represents all start-stop state sets of the hydrogen production electrolytic cell in the T time period. A 1 indicates that the unit is now in operation and a 0 indicates that the unit is now in a shutdown state.

In addition, binary variables alpha and beta are set to respectively correspond to all start-stop state sets of the wind turbine generator and the photovoltaic power generation unit in the T time period, and the meanings represented by 1 and 0 are the same as gamma. All equipment is in a shutdown state at the initial moment, namely:

α(0)＝β(0)＝γ(0)＝0

at each calculation time t, α, β and γ, the following constraints have to be satisfied:

meanwhile, in order to ensure that the wind-solar power generation unit and the hydrogen production electrolytic cell start the access system one by one and prevent the bus voltage from overlarge fluctuation caused by simultaneously merging a plurality of devices into the system, the alpha, the beta and the gamma also need to meet the following constraint conditions:

α(t)-α(t-1)+β(t)-β(t-1)+γ(t)-γ(t-1)≤1

besides, the system needs to satisfy the power balance constraint conditions during operation, namely:

α(t)(P_PV(t)-P_{sup_PV})+β(t)P_wind(t)-P_{sup_wind}+P_bat(t)-γ(t)P_{h2_hot}-P_{h2_sup}＝0

wherein P is_PV(t)、P_wind(t) predicting output of photovoltaic power and wind power at the moment t respectively; p_{sup_PV}The power required by the work of a DC/DC converter corresponding to the photovoltaic power generation unit can be directly obtained from the photovoltaic PV assembly; p_{h2_hot}Power, P, required for the cell to reach hot standby conditions_bat(t) is the charge-discharge power of the energy storage system at the moment t, and the specific expression is as follows:

wherein the content of the first and second substances,

and

the binary variables respectively represent the charging and discharging states of the stored energy and meet the following constraint conditions:

P_ch(t) and P_dis(t) the energy storage charging and discharging power at the moment t respectively meets the following constraint conditions:

wherein the content of the first and second substances,

for the maximum limit of the stored energy charging power,

and the maximum limit value of the energy storage discharge power is obtained.

(5) And (4) solving the optimization objective function in the step (4) to obtain the optimal equipment starting sequence. And sequentially starting the equipment to be merged into the microgrid system according to the optimal starting sequence.

(6) And judging whether the temperature of the hydrogen production electrolytic cell reaches a hot standby working condition, if not, waiting until the system meets a hot start condition, and the hydrogen production electrolytic cell starts to receive a system scheduling instruction to produce hydrogen, at the moment, the electrolytic cell works in a constant-current control mode, and the wind-solar power generation unit works in a limited power mode. And the upper layer coordination control system regulates the output of each unit in the microgrid according to a power conservation principle. The following conditions are satisfied:

at this time:

P_{PV_ref}(t)-P_{sup_PV}+P_{wind_ref}(t)-P_{sup_wind}+P_bat(t)-P_{h2_ref}(t)-P_{h2_sup}＝0 (6)

wherein P is_{PV_ref}(t)、P_{wind_ref}(t)、P_{h2_ref}And (t) respectively controlling the photovoltaic, the fan and the hydrogen production electrolytic cell scheduling instructions issued by the coordination system at the moment t.

(7) The system black start is complete.

(8) The photovoltaic power generation unit is used as a black start power supply, works in a constant voltage mode and is used for maintaining the voltage of the direct current bus.

(9) And the energy storage system is put into operation at the next moment, and the photovoltaic power generation unit charges the low SOC energy storage system.

(10) And judging whether the next time t is the moment when the light storage unit can meet the following power supply conditions:

P_dis(t)+P_PV(t)-P_{sup_pV}≥P_sup

and if the conditions are met, the power supply of the wind power generator set and the auxiliary equipment of the hydrogen production electrolytic cell in the system is restored. And (5) executing the optimization control algorithm in the step (4). Adding a constraint condition:

α(0)＝1

otherwise, returning to the step (8), and continuously charging the energy storage system by the photovoltaic power generation unit.

In conclusion, the black-start scheme optimization method suitable for the renewable energy direct-current micro-grid hydrogen production system is provided. The method ensures that the important load of the system, namely the power supply of the hydrogen production electrolytic cell, can be safely, reliably and quickly recovered under the fault condition of the micro-grid system, and improves the stability, reliability and hydrogen production efficiency of the system. The method is characterized in that the dynamic characteristic of the hydrogen production load is considered, meanwhile, in order to prevent potential safety hazards caused by long-time power loss of the hydrogen production load, an optimization objective function taking the fastest recovery of hydrogen production load power supply as an optimization objective is provided based on future wind-solar power generation prediction data, and an optimal equipment investment scheme for recovering the hydrogen production load power supply within the fastest time is decided and judged. The safety and the reliability of the black start scheme are improved. Meanwhile, various initial conditions and future weather conditions are considered, a targeted black-start equipment operation scheme is provided, and black-start flexibility and feasibility of the microgrid system are improved.

Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but various changes may be apparent to those skilled in the art, and it is intended that all inventive concepts utilizing the inventive concepts set forth herein be protected without departing from the spirit and scope of the present invention as defined and limited by the appended claims.

Claims (5)

1. A renewable energy direct-current micro-grid hydrogen production black start optimization method is characterized by comprising the following steps:

(1) before the system black start command is executed, the energy storage unit SOC at the current t0 moment is read_t0Judging whether the stored energy can meet the condition of being used as a system black start power supply at the moment, and executing the step (2) if the stored energy can meet the condition; otherwise, executing the step (8);

(2) the energy storage system is used as a black start power supply to execute a system black start mode, and the energy storage unit works in a constant voltage mode at the moment and is used for maintaining the voltage of the direct current bus;

(3) the wind turbine generator and the hydrogen production electrolytic cell auxiliary equipment recover power supply;

(4) judging the optimal equipment investment sequence at the next moment based on an optimization control algorithm according to the wind and light prediction data and the optimization objective function;

(5) solving the optimized objective function in the step (4) to obtain an optimal equipment starting sequence, and sequentially starting the equipment to be merged into the microgrid system according to the obtained optimal starting sequence;

(6) judging whether the temperature of the hydrogen production electrolytic cell reaches a hot standby working condition, if not, waiting until the system meets a hot start condition, and the hydrogen production electrolytic cell starts to receive a system scheduling instruction to produce hydrogen, wherein the electrolytic cell works in a constant-current control mode, the wind-solar power generation unit works in a power limiting mode, and the upper-layer coordination control system regulates the output of each unit in the microgrid according to a power conservation principle;

(7) completing the black start of the system;

(8) the photovoltaic power generation unit is used as a black start power supply, works in a constant voltage mode and is used for maintaining the voltage of the direct current bus;

(9) the energy storage system at the next moment is put into operation, and the photovoltaic power generation unit charges the low SOC energy storage system;

(10) judging whether the light storage unit can meet the preset power supply condition at the next moment t, and if the light storage unit meets the preset power supply condition, recovering the power supply of the wind power generator set and the hydrogen production electrolytic cell auxiliary equipment in the system; next, executing the optimization control algorithm in the step (4); adding a constraint condition: otherwise, returning to the step (8), and continuously charging the energy storage system by the photovoltaic power generation unit.

2. The black-start optimization method for hydrogen production through renewable energy direct-current microgrid according to claim 1 is characterized in that the conditions are as follows:

P_dis(t₀)≥P_sup

wherein P is_dis(t₀) Is t₀The maximum discharge power of the energy storage unit at any moment is expressed as follows:

SOC_lowfor the lower limit value SOC of the energy storage unit SOC_t0The SOC of the energy storage unit at the time t0 is shown, and delta t is a preset time interval; eta_disTo discharge efficiency; e_batRated capacity for energy storage;

the maximum discharge power allowed for the energy storage system; p_supIn order to ensure the total power required by the power supply of auxiliary equipment for normal operation of equipment in a system, the specific expression is as follows:

P_sup＝P_{sup_wind}+P_{h2_sup}

P_{sup_wind}and P_{h2_sup}And the power required by power supply is respectively supplied to auxiliary equipment for ensuring normal operation of the wind turbine generator and the hydrogen production electrolytic cell.

3. The black-start optimization method for hydrogen production through renewable energy direct-current microgrid according to claim 1, characterized in that step (4) specifically comprises:

the optimization objective function takes the most important load, namely the fastest recovery power supply of the hydrogen production electrolytic cell, as an optimization objective, and the specific function expression is as follows:

wherein T is the total time period number of the operation of the optimization objective function, gamma is a binary variable and represents all start-stop state sets of the hydrogen production electrolytic cell in the time period T, 1 represents that the unit is in a working state at the moment, and 0 represents that the unit is in a shutdown state at the moment;

in addition, binary variables alpha and beta are set to respectively correspond to all start-stop state sets of the wind turbine generator and the photovoltaic power generation unit in a T time period, the meanings represented by 1 and 0 are the same as gamma, and all equipment are in a stop state at the initial moment, namely:

α(0)＝β(0)＝γ(0)＝0

at each calculation time t, β and γ, the following constraints have to be satisfied:

meanwhile, in order to ensure that the wind-solar power generation unit and the hydrogen production electrolytic cell start the access system one by one and prevent the bus voltage from overlarge fluctuation caused by simultaneously merging a plurality of devices into the system, the alpha, the beta and the gamma also need to meet the following constraint conditions:

α(t)-α(t-1)+β(t)-β(t-1)+γ(t)-γ(t-1)≤1

besides, the system needs to satisfy the power balance constraint conditions during operation, namely:

α(t)(P_PV(t)-P_{sup_PV})+β(t)P_wind(t)-P_{sup_wind}+P_bat(t)-γ(t)P_{h2_hot}-P_{h2_sup}＝0

wherein P is_PV(t)、P_wind(t) predicting output of photovoltaic power and wind power at the moment t respectively; p_{sup_PV}The power required by the work of a DC/DC converter corresponding to the photovoltaic power generation unit is directly obtained from the photovoltaic PV assembly; p_{h2_hot}Power, P, required for the cell to reach hot standby conditions_bat(t) is the charge-discharge power of the energy storage system at the moment t, and the specific expression is as follows:

wherein the content of the first and second substances,

and

the binary variables respectively represent the charging and discharging states of the stored energy and meet the following constraint conditions:

P_ch(t) and P_dis(t) the energy storage charging and discharging power at the moment t respectively meets the following constraint conditions:

wherein the content of the first and second substances,

for the maximum limit of the stored energy charging power,

and the maximum limit value of the energy storage discharge power is obtained.

4. The renewable energy direct-current microgrid hydrogen production black start optimization method according to claim 1, characterized in that in step (6), the upper layer coordination control system adjusts the output of each unit in the microgrid according to a power conservation principle, and the following conditions are satisfied:

P_{PV_ref}(t)-P_{sup_PV}+P_{wind_ref}(t)-P_{sup_wind}+P_bat(t)-P_{h2_ref}(t)-P_{h2_sup}＝0 (6)

wherein P is_{PV_ref}(t)、P_{wind_ref}(t)、P_{h2_ref}And (t) respectively controlling the photovoltaic, the fan and the hydrogen production electrolytic cell scheduling instructions issued by the coordination system at the moment t.

5. The black-start optimization method for hydrogen production through renewable energy direct current microgrid according to claim 1, characterized in that in the step (10), the predetermined power supply conditions are as follows:

P_dis(t)+P_PV(t)-P_{sup_PV}≥P_sup(ii) a The constraint condition is that α (0) is 1.

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