CN114825412A - Energy management method and device for energy storage access low-voltage direct-current power supply system - Google Patents

Abstract

The invention discloses an energy management method and device for accessing energy storage to a low-voltage direct-current power supply system, which comprises the following steps: dividing related equipment of a low-voltage direct-current power supply system into controllable equipment and uncontrollable equipment; respectively establishing control constraint conditions of the controllable equipment and the uncontrollable equipment; establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to a preset energy management target of the direct-current power supply system and the control constraint condition; and managing the energy of the energy storage access low-voltage direct-current power supply system according to the controllable equipment regulation and control instruction output by the optimization target model. The control characteristics and requirements of energy storage, photovoltaic, AC/DC converters and controllable loads are taken into consideration, and the method has the advantages of complete regulation and control equipment and good model adaptability, and is suitable for energy storage regulation and control of a novel power system.

Description

Energy management method and device for energy storage access low-voltage direct-current power supply system

Technical Field

The application relates to the field of optimized operation of power systems, in particular to an energy management method and device for accessing energy storage to a low-voltage direct-current power supply system.

Background

The distributed power supply has the characteristics of randomness and intermittence, the direct access to an alternating current power grid can generate great influence on the quality of electric energy, and the electric energy generated by the common distributed power supply comprises a direct current link, so that the distributed access to the direct current bus not only can save a current conversion link and loss, but also can be used as a buffer link to reduce negative influence caused by power fluctuation. Moreover, the direct-current power distribution network can be conveniently connected with direct-current and variable-frequency loads, high-efficiency, flexible and safe power supply service is provided according to user requirements, and the development requirements of the intelligent power grid are met. Therefore, the low-voltage direct-current power supply system becomes one of important ways of distributed photovoltaic grid connection. The low-voltage direct-current power supply system comprises a networking AC/DC converter, an energy storage DC/DC converter, a photovoltaic DC/DC converter, an electric automobile and other controllable loads, so that how to optimally schedule the energy of the energy storage access low-voltage direct-current power supply system is a difficult problem.

Disclosure of Invention

In order to solve the above problem, the present application provides an energy management method for accessing an energy storage to a low-voltage dc power supply system, including:

dividing related equipment of a low-voltage direct-current power supply system into controllable equipment and uncontrollable equipment;

respectively establishing control constraint conditions of the controllable equipment and the uncontrollable equipment;

establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to a preset energy management target of the direct-current power supply system and the control constraint condition;

and managing the energy of the energy storage access low-voltage direct-current power supply system according to the controllable equipment regulation and control instruction output by the optimization target model.

Preferably, the device related to the low voltage dc power supply system is divided into a controllable device and an uncontrollable device, and includes:

the associated devices of the low voltage dc supply system are divided into controllable devices and uncontrollable devices according to their control characteristics, wherein,

the controllable device comprises: photovoltaic equipment, energy storage equipment and an AC/DC converter;

the uncontrollable device comprises: distribution unit load, uncontrollable distributed power.

Preferably, the establishing of the control constraints of the controllable device and the uncontrollable device respectively comprises:

establishing photovoltaic power upper and lower limit constraints for photovoltaic equipment in the controllable equipment;

for energy storage equipment in the controllable equipment, establishing charge-discharge state constraint, energy storage power upper-lower limit constraint and energy storage charge state constraint of the energy storage equipment;

establishing upper and lower limit constraints of the external power purchase of the converter for an AC/DC converter in the controllable equipment;

and for the uncontrollable equipment, taking the uncontrollable equipment as an uncontrollable disturbance variable, and establishing the uncontrollable equipment to meet power balance constraint.

Preferably, the charge and discharge state constraint of the energy storage device includes: the energy storage device cannot be in charge-discharge state constraint and the energy storage device prevents frequent switching of charge-discharge state constraint.

Preferably, the preset energy management target of the dc power supply system includes: the direct-current voltage is maintained within a safe range; the photovoltaic utilization rate is maximized; the total outsourcing electricity cost of the building is minimized; the dc voltage is minimized.

Preferably, the establishing an optimization target model of the energy storage access low-voltage dc power supply system according to a preset energy management target of the dc power supply system and the control constraint condition includes:

assigning different weights to the energy management targets of the direct current power supply systems;

establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to the weight and the control constraint condition, wherein the model is,

wherein t represents a time period, and is divided into 96 points every day; alpha, beta and epsilon respectively represent the weight of each item, wherein the weight alpha of the abandoned light quantity is greater than the other two weights, and the light is preferentially not abandoned; p _i,t Representing the actual generated power of the ith photovoltaic during the t-th time period, wherein i belongs to PV and refers to the ith photovoltaic from the set of photovoltaic devices; c _t Represents the time-of-use electricity price of the t-th time period;

the full power generation power representing the ith photovoltaic time interval is obtained by power prediction; p _PCC,t P _PCC,t-1 Representing the exchange power of the AC/DC converter with the external system during the t-th, t-1 th period.

Preferably, the managing the energy of the energy storage access low-voltage dc power supply system according to the controllable device regulation and control instruction output by the optimization target model includes:

solving the optimization target model through a Newton method to obtain a controllable device regulation and control instruction output by the optimization target model;

and regulating and controlling the controllable equipment through the controllable equipment regulating and controlling instruction to complete energy management of accessing the stored energy into the low-voltage direct-current power supply system.

This application provides an energy management device for energy storage inserts low pressure DC power supply system simultaneously, includes:

the device dividing unit is used for dividing related devices of the low-voltage direct-current power supply system into controllable devices and uncontrollable devices;

the control constraint condition establishing unit is used for respectively establishing control constraint conditions of the controllable equipment and the uncontrollable equipment;

the optimization target model establishing unit is used for establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to a preset energy management target of the direct-current power supply system and the control constraint condition;

and the energy management unit is used for managing the energy of the energy storage access low-voltage direct-current power supply system according to the controllable equipment regulation and control instruction output by the optimization target model.

Drawings

Fig. 1 is a schematic flowchart of an energy management method for accessing an energy storage to a low-voltage dc power supply system according to an embodiment of the present application;

fig. 2 is a topology diagram of a low-voltage dc power supply system according to an embodiment of the present application;

FIG. 3 is a graph of energy storage power variation according to an embodiment of the present application;

FIG. 4 is a variation curve of the energy storage SOC according to the embodiment of the present application;

fig. 5 is a schematic diagram of an energy management device for accessing an energy storage into a low-voltage dc power supply system according to an embodiment of the present application.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of implementation in many different ways than those herein set forth and of similar import by those skilled in the art without departing from the spirit of this application and is therefore not limited to the specific implementations disclosed below.

Fig. 1 is a schematic flowchart of an energy management method for accessing a low-voltage dc power supply system through stored energy according to an embodiment of the present application, and the method provided in the present application is described in detail below with reference to fig. 1.

Step S101, dividing related equipment of a low-voltage direct-current power supply system into controllable equipment and uncontrollable equipment.

The application provides an energy management method for an energy storage access low-voltage direct-current power supply system, which is suitable for a high-permeability distributed power supply and the energy storage access low-voltage direct-current power supply system.

According to the control characteristics of related equipment of a low-voltage direct-current power supply system, dividing the related equipment into controllable equipment and uncontrollable equipment, wherein the controllable equipment comprises: photovoltaic equipment, energy storage equipment and a networking AC/DC converter; the uncontrollable device comprises: distribution unit load, uncontrollable distributed power.

The photovoltaic power of the photovoltaic equipment can be fully utilized as far as possible under the premise of meeting the safety and load requirements of a power supply system, and the power can be adjusted under necessary conditions.

The energy storage power of the energy storage equipment realizes peak clipping and valley filling, and the exchange power with an external network is stabilized as far as possible on the premise of maximally absorbing photovoltaic power generation.

The AC/DC converter power of the AC/DC converter, i.e. the power exchanged with the external system, is responsible for establishing and stabilizing the DC bus voltage.

And step S102, respectively establishing control constraint conditions of the controllable equipment and the uncontrollable equipment.

And establishing corresponding control constraint conditions for the controllable equipment according to the control characteristics of the controllable equipment.

For photovoltaic equipment in the controllable equipment, photovoltaic power upper and lower limit constraints are established, the photovoltaic power generation power is required to be not more than the full power generation power, the full power generation power is determined by the illumination condition, the full power generation power is less than or equal to the photovoltaic capacity, and the power lower limit is 0, namely

Wherein, P _i,t Represents the generated power of the ith photovoltaic period t,

expressed as the photovoltaic capacity of the ith photovoltaic period. In principle, light is not abandoned, but when the power is difficult to balance and the system has operation risks, the light abandoning method can be adopted to maintain the stable operation of the system.

And for the energy storage equipment in the controllable equipment, establishing the charge-discharge state constraint, the energy storage power upper-lower limit constraint and the energy storage charge state constraint of the energy storage equipment. The charge-discharge state constraint of the energy storage device comprises: the energy storage device cannot be in charge-discharge state constraint and the energy storage device prevents frequent switching of charge-discharge state constraint.

The energy storage equipment can not be in the restriction of charging and discharging states at the same time, and the energy storage equipment is required to be in the charging and discharging states at the same time, namely

x _j,t ,y _j,t ∈[0,1],for t∈{1,2,…,96}

0≤x _j,t +y _j,t ≤1,for t∈{1,2,…,96}

Wherein x _j,t ,y _j,t Respectively showing the energy storage charging and discharging states of the jth energy storage in the tth time period, if the energy storage charging and discharging states are charging, x _j,t ＝1,y _j,t 0, if discharge, x _j,t ＝0,y _j,t 1. The sum of the state variables of 0 to 1 is not more than 1, so that the constraint that the stored energy cannot be in a charging and discharging state at the same time is met.

The energy storage prevents the restraint of frequent switching of charging and discharging states, and the charging and discharging states cannot be frequently switched by the requirement of energy storage so as to guarantee the service life of the energy storage. Requiring the stored energy to remain charged between two charging periods and to remain discharged between two discharging periods, i.e.

x _j,t ≥x _j,t-1 +x _j,t+1 -1,for t∈{1,2,…,96}

y _j,t ≥y _j,t-1 +y _j,t+1 -1,for t∈{1,2,…,96}

Wherein x _j,t ,x _j,t-1 ,x _j,t+1 And y _j,t ,y _j,t-1 ,y _j,t+1 Respectively showing the energy storage charging and discharging states of the jth energy storage in the tth period, the t-1 period and the t +1 period. The constraints described above ensure that the energy storage state does not change frequently, as is a 0-1 state variable.

And the upper limit and the lower limit of the energy storage power are restricted, and the energy storage charging and discharging power is required not to exceed the upper limit of the capacity. Constraints can be expressed as

Wherein, P _c,j,t Representing charging power, P, for j energy-storing t-th periods _d,j,t Represents the discharge power of j energy storage t-th time periods,

represents the upper power limit of the jth energy storage period t.

The energy storage charge state is constrained to be in a feasible range with the upper limit and the lower limit specified so as to ensure that the energy storage has sufficient regulation space, the upper limit and the lower limit are determined by energy storage parameters, and the charge state is determined by charge-discharge power and energy storage efficiency, namely

SOC _j,t ＝SOC _j,t-1 -P _d,j,t Δt/λ _d,j +λ _c,j P _c,j,t Δt,for t∈{1,2,…,96}

L _j ≤SOC _j,t ≤U _j ,for t∈{1,2,…,96}

Therein, SOC _j,t 、SOC _j,t-1 Representing the charge states of a jth energy storage time interval and a t-1 time interval; Δ t represents the time interval between two periods, typically set at 15 minutes; p _d,j,t Representing the discharge power, P, of j energy-storing t-th periods _c,j,t Representing the charging power of j energy storage t-th time periods; lambda [ alpha ] _d,j Representing the discharge efficiency of the jth stored energy; lambda [ alpha ] _c,j Represents the charging efficiency of the jth stored energy; l is _j Represents the lower state of charge of the jth stored energy; u shape _j Representing the upper state of charge of the jth stored energy.

For the AC/DC converter in the controllable equipment, the upper and lower limits of the external power purchase of the converter are restricted, and the power exchange between the system converter and an external system is required not to exceed the upper limit of the capacity of the converter. Constraints can be expressed as

Wherein, P _PCC,t Representing the power exchanged by the system converter with the external system during the t-th period, P _PCC,t Representing the upper limit of the system converter capacity. The converter power can be exchanged bi-directionally, neither of which can exceed the capacity limit.

For the uncontrollable equipment, the uncontrollable equipment is used as an uncontrollable disturbance variable, the uncontrollable equipment is established to meet the power balance constraint, and the total power generation power and the total load of photovoltaic power, energy storage power and outsourcing power are balanced in 96 time intervals, namely

Wherein, P _PCC,t Representing the exchanged power of the system converter with the external system in the t-th period; p _i,t Representing the generated power of the ith photovoltaic in the tth time period, wherein i belongs to PV and refers to the ith photovoltaic in the set of photovoltaic equipment; x is the number of _j,t And y _j,t The energy storage discharge and charge state variables represent the jth energy storage period t, if the energy storage discharge and charge state variables are discharge (charge) state, the value is 1, otherwise, the value is 0; p _d,j,t Representing the discharge power, P, of the jth energy-storage period t _c,j,t Represents the charging power of the jth energy storage tth period, _j e ES refers to the jth from the energy storage device set; p _D,t And the total load power of the system in the t-th period comprises the total load of the air conditioner, the fresh air machine, the charging pile and the integrated power distribution unit.

And S103, establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to a preset energy management target of the direct-current power supply system and the control constraint condition.

The preset energy management target of the direct current power supply system comprises the following steps: the direct-current voltage is maintained within a safe range; the photovoltaic utilization rate is maximized; the total outsourcing electricity cost of the building is minimized; the dc voltage is minimized.

Assigning different weights to the energy management targets of the direct current power supply systems; firstly, maximum photovoltaic consumption is guaranteed as far as possible, so that the power of the abandoned light quantity is given high weight and is placed in an objective function, and on the basis, the purchased electric power cost and the square of the power fluctuation of the converter are weighted and summed, and the optimization target is realized on the premise of complete photovoltaic consumption.

Establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to the weight and the control constraint condition, wherein the model is,

wherein t represents a time period, and is divided into 96 points every day; alpha, beta and epsilon respectively represent the weight of each item, wherein the weight alpha of the abandoned light quantity is greater than the other two weights, and the light is preferentially not abandoned; p _i,t Representing the actual generated power of the ith photovoltaic during the t-th time period, wherein i belongs to PV and refers to the ith photovoltaic from the set of photovoltaic devices; c _t Represents the time-of-use electricity price of the t-th time period;

the full power generation power representing the ith photovoltaic time interval is obtained by power prediction; p _PCC,t P _PCC,t-1 Representing the exchange power of the AC/DC converter with the external system during the t-th, t-1 th period.

And step S104, managing the energy of the energy storage access low-voltage direct current power supply system according to the controllable equipment regulation and control instruction output by the optimization target model.

Solving the optimization target model through a Newton method to obtain a controllable device regulation and control instruction output by the optimization target model; and regulating and controlling the controllable equipment through the controllable equipment regulating and controlling instruction to complete energy management of accessing the stored energy into the low-voltage direct-current power supply system.

The preferred embodiment for the specific application is as follows:

as shown in FIG. 2, the municipal input voltage class on the AC side of the example is 10kV, 380V AC voltage class is output through the transformer, the power supply capacity of the front-end AC transformer is designed to be 630kV, and the DC capacity of the rectifier module is designed to be 300 kW; the total power load is 450kW, the controllable load is mainly divided into two parts, the direct current charging pile is 30kW and 2 to 60kW, and the direct current variable frequency air conditioner is 120 kW; the DC voltage class includes: high-voltage side ± 375V (750V inter-pole voltage), single pole 375V, low-voltage side 48V; the distributed power supply mainly comprises 150kW photovoltaic power generation and 100kWh storage batteries; the energy storage system is 150kW, participates in system regulation and control, provides and optimizes the power supply quality and the operation characteristic of the system, and receives a system control instruction.

1. And dividing the low-voltage direct current power supply system equipment. The uncontrollable device includes a power distribution unit load. A controllable device for energy management comprising:

1) the power of the AC/DC converter is 300 kW;

2) energy storage power, capacity is 150 kW;

3) photovoltaic power, capacity 150 kW.

2. And establishing control constraint conditions for controllable equipment such as controllable photovoltaic, energy storage and networking AC/DC converters according to the control characteristics of the controllable equipment.

1) Requiring the stored energy not to be charged or discharged simultaneously, i.e.

x _j,t ,y _j,t ∈[0,1],for t∈{1,2,…,96}

0≤x _j,t +y _j,t ≤1,for t∈{1,2,…,96}

Wherein x _j,t ,y _j,t Respectively showing the energy storage charging and discharging states of the jth energy storage in the tth time period, if the energy storage charging and discharging states are charging, x _j,t ＝1,y _j,t 0, if discharge, x _j,t ＝0,y _j,t 1. The sum of the state variables of 0 to 1 is not more than 1, so that the constraint that the stored energy cannot be in a charging and discharging state at the same time is met.

2) Energy storage for preventing frequent switching of charging and discharging state constraint

The energy storage state can not be frequently switched to the charge-discharge state, so that the service life of the energy storage is ensured. Requiring the stored energy to remain charged between two charging periods and to remain discharged between two discharging periods, i.e.

x _j,t ≥x _j,t-1 +x _j,t+1 -1,for t∈{1,2,…,96}

y _j,t ≥y _j,t-1 +y _j,t+1 -1,for t∈{1,2,…,96}

Wherein x _j,t ,x _j,t-1 ,x _j,t+1 And y _j,t ,y _j,t-1 ,y _j,t+1 Respectively showing the energy storage charging and discharging states of the jth energy storage in the tth period, the t-1 period and the t +1 period. Due to the fact thatIs a 0-1 state variable, and the constraint can ensure that the energy storage state does not change frequently.

3) Upper and lower energy storage power limits

The energy storage charging and discharging power is required not to exceed the upper limit of the capacity. Constraints can be expressed as

Wherein, P _c,j,t Representing charging power, P, for j energy-storing t-th periods _d,j,t Represents the discharge power of j energy storage t-th time periods,

the upper power limit, which represents the jth stored energy period t, is 150kW in this example.

4) Upper and lower photovoltaic power constraints

The photovoltaic power generation power is required not to exceed the full power generation power, the full power generation power is determined by the illumination condition, the photovoltaic capacity is less than or equal to 150kW, and the lower power limit is 0, namely

Wherein, P _i,t Represents the generated power of the ith photovoltaic period t,

expressed as the photovoltaic capacity of the ith photovoltaic period. In principle, light is not abandoned, but when the power is difficult to balance and the system has operation risks, the light abandoning method can be adopted to maintain the stable operation of the system.

5) Converter outsourcing power upper and lower limit constraints

The system converter is required to exchange power with an external system not to exceed 300kW of upper converter capacity. Constraints can be expressed as

Wherein, P _PCC,t Representing the power exchanged by the system converter with the external system during the t-th period,

representing the upper limit of the system converter capacity. The converter power can be exchanged bi-directionally, neither of which can exceed the capacity limit.

6) Energy storage state of charge confinement

The state of charge of the stored energy is required to be in a feasible range defined by the upper limit and the lower limit to ensure that the stored energy has sufficient regulation space, the upper limit and the lower limit are determined by the stored energy parameters, and the state of charge is determined by the charge-discharge power and the stored energy efficiency, namely

SOC _j,t ＝SOC _j,t-1 -P _d,j,t Δt/λ _d,j +λ _c,j P _c,j,t Δt,for t∈{1,2,…,96}

L _j ≤SOC _j,t ≤U _j ,for t∈{1,2,…,96}

Wherein, SOC _j,t 、SOC _j,t-1 Representing the charge states of a jth energy storage time interval and a t-1 time interval; Δ t represents the time interval between two periods, typically set at 15 minutes; p _d,j,t Representing the discharge power, P, of j energy-storing t-th periods _c,j,t Representing the charging power of j energy storage t-th time periods; lambda [ alpha ] _d,j Representing the discharge efficiency of the jth stored energy; lambda [ alpha ] _c,j Represents the charging efficiency of the jth stored energy; l is _j Represents the lower state of charge of the jth stored energy; u shape _j Representing the upper state of charge of the jth stored energy.

3. For an uncontrollable device, it is considered as an uncontrollable disturbance variable. Satisfying power balance constraints

The photovoltaic, energy storage and outsourcing power generation total power and the total load are balanced in 96 time intervals, namely

Wherein the content of the first and second substances,

P _PCC,t representing the exchanged power of the system converter with the external system in the t-th period; p _i,t Representing the generated power of the ith photovoltaic in the tth time period, wherein i belongs to PV and refers to the ith photovoltaic in the set of photovoltaic equipment; x is the number of _j,t And y _j,t The energy storage discharge and charge state variables represent the jth energy storage period t, if the energy storage discharge and charge state variables are discharge (charge) state, the value is 1, otherwise, the value is 0; p _d,j,t Representing the discharge power, P, of the jth energy-storage period t _c,j,t Representing the charging power of the jth energy storage tth period, wherein j epsilon ES refers to the jth energy storage device in the set of energy storage devices; p _D,t And the total load power of the system in the t-th period comprises the total load of the air conditioner, the fresh air machine, the charging pile and the integrated power distribution unit.

4. And establishing an objective function of accessing the stored energy into the low-voltage direct-current power supply system according to different optimization objectives of the low-voltage direct-current power supply system.

Energy storage, a converter and photovoltaic power are used as optimization variables, light is not abandoned in principle, and the initial state of charge of the energy storage is assumed to be 50kWh, namely 50% of the total energy storage capacity. The optimization routine is run to obtain the daily variation curve of the stored energy power as shown in fig. 3. As can be seen from fig. 3, the number of times of change of the charging and discharging states of the energy storage day is 6, and due to constraint limitation, the energy storage does not have the situation of frequent switching of the charging and discharging states.

5. Energy management optimization model for solving energy storage access low-voltage direct-current power supply system by using Czochralski method

According to the energy management method suitable for the energy storage access low-voltage direct-current power supply system, the energy storage power daily change curve is shown in fig. 3, the change frequency of the energy storage daily charge and discharge state can be obtained to be 6 times, and due to constraint limitation, the energy storage does not have the condition of frequently switching the charge and discharge state. The change of the energy storage SOC is shown in fig. 4, and it can be seen from the figure that the energy storage SOC is within the range of its charge capacity, satisfying the SOC safety constraint.

Based on the same inventive concept, the present application also provides an energy management apparatus 500 for accessing an energy storage to a low-voltage dc power supply system, as shown in fig. 5, including:

a device dividing unit 510, configured to divide devices related to the low-voltage dc power supply system into controllable devices and uncontrollable devices;

a control constraint condition establishing unit 520, configured to respectively establish control constraint conditions of the controllable device and the uncontrollable device;

an optimization target model establishing unit 530, configured to establish an optimization target model of the energy storage access low-voltage dc power supply system according to a preset energy management target of the dc power supply system and the control constraint condition;

and the energy management unit 540 is configured to manage the energy stored in the energy storage access low-voltage dc power supply system according to the controllable device regulation and control instruction output by the optimization target model.

According to the energy management method and device for the energy storage access low-voltage direct-current power supply system, different control targets of the low-voltage direct-current power supply system are integrated, an energy management optimization model of the low-voltage direct-current power supply system comprising the energy storage, the distributed photovoltaic, the AC/DC converter and the controllable load is established, then the optimization model is solved through a Newton method to obtain regulation and control instructions of controllable equipment such as the energy storage and the like, and the energy of the energy storage access low-voltage direct-current power supply system is optimally scheduled through the regulation and control instructions. Meanwhile, the control characteristics and requirements of energy storage, photovoltaic, AC/DC converters and controllable loads are considered, and the method has the advantages of complete regulation and control equipment, good model adaptability and the like, and is suitable for energy storage regulation and control of a novel power system.

Finally, it should be noted that: although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention.

Claims (8)

1. An energy management method for accessing an energy storage into a low-voltage direct-current power supply system is characterized by comprising the following steps:

dividing related equipment of a low-voltage direct-current power supply system into controllable equipment and uncontrollable equipment;

respectively establishing control constraint conditions of the controllable equipment and the uncontrollable equipment;

establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to a preset energy management target of the direct-current power supply system and the control constraint condition;

and managing the energy of the energy storage access low-voltage direct-current power supply system according to the controllable equipment regulation and control instruction output by the optimization target model.

2. The method of claim 1, wherein dividing the devices associated with the low voltage dc power supply system into controllable devices and uncontrollable devices comprises:

the associated devices of the low voltage dc supply system are divided into controllable devices and uncontrollable devices according to their control characteristics, wherein,

the controllable device comprises: photovoltaic equipment, energy storage equipment and an AC/DC converter;

the uncontrollable device comprises: distribution unit load, uncontrollable distributed power.

3. The method of claim 1, wherein establishing control constraints for the controllable device and the uncontrollable device respectively comprises:

establishing photovoltaic power upper and lower limit constraints for photovoltaic equipment in the controllable equipment;

for energy storage equipment in the controllable equipment, establishing charge-discharge state constraint, energy storage power upper-lower limit constraint and energy storage charge state constraint of the energy storage equipment;

establishing upper and lower limit constraints of the external power purchase of the converter for an AC/DC converter in the controllable equipment;

and for the uncontrollable equipment, taking the uncontrollable equipment as an uncontrollable disturbance variable, and establishing the uncontrollable equipment to meet power balance constraint.

4. The method of claim 3, wherein the charging and discharging state constraints of the energy storage device comprise: the energy storage device cannot be in charge-discharge state constraint and the energy storage device prevents frequent switching of charge-discharge state constraint.

5. The method of claim 1, wherein the pre-set dc power system energy management goals comprise: the direct-current voltage is maintained within a safe range; the photovoltaic utilization rate is maximized; the total outsourcing electricity cost of the building is minimized; the dc voltage is minimized.

6. The method according to claim 1, wherein the establishing of the optimization objective model of the energy storage access low-voltage dc power supply system according to the preset energy management objective of the dc power supply system and the control constraint condition comprises:

assigning different weights to the energy management targets of the direct current power supply systems;

establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to the weight and the control constraint condition, wherein the model is,

wherein t represents a time period, and is divided into 96 points every day; alpha, beta and epsilon respectively represent the weight of each item, wherein the weight alpha of the abandoned light quantity is greater than the other two weights, and the light is preferentially not abandoned; p _i,t Representing the actual generated power of the ith photovoltaic during the t-th time period, wherein i belongs to PV and refers to the ith photovoltaic from the set of photovoltaic devices; c _t Represents the time-of-use electricity price of the t-th time period;

the full power generation power representing the ith photovoltaic time interval is obtained by power prediction; p _PCC,t P _PCC,t-1 Representing the exchange work of the AC/DC converter with the external system in the t-th and t-1-th time periodsAnd (4) rate.

7. The method according to claim 1, wherein managing the energy stored in the energy storage and accessed to the low-voltage DC power supply system according to the controllable device regulation and control instruction output by the optimization objective model comprises:

solving the optimization target model through a Newton method to obtain a controllable device regulation and control instruction output by the optimization target model;

and regulating and controlling the controllable equipment through the controllable equipment regulating and controlling instruction to complete energy management of accessing the stored energy into the low-voltage direct-current power supply system.

8. An energy management device for accessing stored energy into a low voltage dc power supply system, comprising:

the device dividing unit is used for dividing related devices of the low-voltage direct-current power supply system into controllable devices and uncontrollable devices;

the control constraint condition establishing unit is used for respectively establishing control constraint conditions of the controllable equipment and the uncontrollable equipment;

the optimization target model establishing unit is used for establishing an optimization target model of the energy storage access low-voltage direct-current power supply system according to a preset energy management target of the direct-current power supply system and the control constraint condition;

and the energy management unit is used for managing the energy of the energy storage access low-voltage direct-current power supply system according to the controllable equipment regulation and control instruction output by the optimization target model.

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