阅读说明：本技术 一种基于分布式多母线接入储能自适应柔性控制方法 (Distributed multi-bus access based energy storage self-adaptive flexible control method ) 是由 赖少川 廖兴万 徐烺 廖远桓 李斌 段曦瞳 于 2021-07-19 设计创作，主要内容包括：本发明公开了一种基于分布式多母线接入储能自适应柔性控制方法,涉及电网并网控制系统,解决了在电网负荷较少时,会将储能系统所发电能反送至电网上容易引起电网过载或电能逆流的技术问题。包括防逆流策略步骤、防过载策略步骤和系统运行步骤；所述防逆流策略步骤用于确定下发至各分布式储能系统的充电功率和放电功率；所述防过载策略步骤用于确定需要下发至所有的分布式储能系统的总充电功率限值和总放电功率限值；所述系统运行步骤用于分析判断储能系统以防逆流策略和防过载策略中的哪种运行,方能同时满足防逆流和防过载功能。本发明实现储能系统的自适应柔性控制、功率的动态调节,可避免接入母线过载、放电电流反送至电网的问题。(The invention discloses a distributed multi-bus access-based energy storage self-adaptive flexible control method, relates to a power grid-connected control system, and solves the technical problem that when the load of a power grid is low, the generated energy of an energy storage system is transmitted back to the power grid, so that the overload of the power grid or the backflow of electric energy are easily caused. The method comprises the steps of anti-reflux strategy, anti-overload strategy and system operation; the anti-reflux strategy step is used for determining charging power and discharging power which are issued to each distributed energy storage system; the overload prevention strategy step is used for determining a total charging power limit value and a total discharging power limit value which need to be issued to all distributed energy storage systems; the system operation step is used for analyzing and judging which operation of an energy storage system in a counter-flow prevention strategy and an overload prevention strategy is performed, so that the counter-flow prevention function and the overload prevention function can be simultaneously met. The invention realizes the self-adaptive flexible control and the dynamic power regulation of the energy storage system, and can avoid the problems of overload of an access bus and reverse transmission of discharge current to a power grid.)

1. A self-adaptive flexible control method based on distributed multi-bus access energy storage is characterized by comprising a counter-current prevention strategy step, an overload prevention strategy step and a system operation step;

the anti-reflux strategy step is used for calculating charging power and discharging power which are issued to each distributed energy storage system according to the collected real-time power of the high-voltage incoming cabinet and the collected real-time power of the energy storage system;

the overload prevention strategy step is used for calculating a total charging power limit value and a total discharging power limit value which need to be issued to all distributed energy storage systems according to the collected real-time power of the low-voltage incoming cabinet and the real-time power of the energy storage systems;

the system operation step is used for judging whether the total discharge power limit value meets the functional relation with the set anti-reflux power or not and whether the total charge power limit value meets the functional relation with the set overload power or not, if so, distributing the total discharge power limit value and the total charge power limit value, and sending the distribution result to a corresponding distributed energy storage system; and otherwise, issuing the charging power and the discharging power to the corresponding distributed energy storage system.

2. The distributed multi-bus access-based energy storage adaptive flexible control method according to claim 1, wherein the counter-flow prevention strategy specifically comprises the steps of:

s11, collecting the real-time power of the high-voltage incoming cabinet and the real-time power of the energy storage system in real time;

s12, judging whether the value of the analytic expression Ps + Pg is larger than or equal to the electric energy forward flow reserved power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total discharge power to zero and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ], and returns to S11;

wherein Pg is the real-time power of the high-voltage incoming cabinet; ps is the real-time power of the energy storage system; pz is the maximum allowable use power of the original power system;

s13, judging whether the value of the analytic expression Ps + Pg-Py is larger than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total discharge power of the energy storage system to a value of an analytic expression Ps + Pg-Py and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ], and returns to S11;

py reserves power for forward flow of electric energy;

s14, the energy management system assigns the total discharge power to the total rated power of the energy storage system and assigns the total charge power to an analytic expression- [ Pz- (Ps + Pg)]According to the formulaDetermining the discharge power of the distributed energy storage system according to a formulaDetermining charging power of a distributed energy storage system;

pfn is the discharge power of the nth distributed energy storage system; pcn is the charging power of the nth distributed energy storage system; pf is the total discharge power; pc is the total charging power; pe is the total rated power of the energy storage system; and Pen is the rated power of the nth distributed energy storage system.

3. The distributed multi-bus access-based energy storage adaptive flexible control method according to claim 2, wherein in S14, the energy management system returns to S11 after assigning values to the total discharge power and the total charge power.

4. The distributed multi-bus access-based energy storage adaptive flexible control method according to claim 1, wherein the overload prevention strategy step specifically comprises the following steps:

s21, collecting real-time power of the low-voltage incoming cabinet and real-time power of the energy storage system in real time;

s22, judging whether the real-time power of the low-voltage incoming cabinet is larger than or equal to zero, and if so, carrying out the next step; otherwise, jumping to S27;

s23, judging whether the real-time power of the energy storage system is less than or equal to zero, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

k is a reserved overload protection coefficient of the transformer; q is the capacity of the low-voltage bus allowed to operate; ps is the real-time power of the energy storage system; pd is the real-time power of the low-voltage incoming cabinet;

s24, judging whether the real-time power of the low-voltage incoming cabinet is less than or equal to the value of the product of the transformer protection overload prevention reserved coefficient and the capacity of the low-voltage bus allowed to run, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

s25, judging whether the value of the analytic expression KQ- (Ps + Pd) is less than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total charging power limit value as a negative value of the total rated power of the energy storage system, and assigns the total discharging power limit value as a value of an analytic formula KQ + (Ps + Pd); and returns to S21;

s26, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd);

s27, judging whether the real-time power of the energy storage system is larger than or equal to zero, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

s28, judging whether the negative value of the real-time power of the low-voltage incoming line cabinet is less than or equal to the value of the product of the transformer protection overload prevention reserved coefficient and the capacity of the low-voltage bus allowed to run, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

s29, judging whether the value of the analytic expression KQ + (Ps + Pd) is less than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value to the total rated power of the energy storage system; and returns to S21;

s30, the energy management system assigns the total charging power limit value to a value of an analytic expression- [ KQ- (Ps + Pd) ] and assigns the total discharging power limit value to a value of an analytic expression KQ + (Ps + Pd).

5. The distributed multi-bus access-based energy storage adaptive flexible control method according to claim 4, wherein in S26, the energy management system returns to S21 after assigning the total charging power limit value and the total discharging power limit value.

6. The distributed multi-bus access-based energy storage adaptive flexible control method according to claim 4, wherein in S30, the energy management system returns to S21 after assigning the total charging power limit value and the total discharging power limit value.

7. The distributed multi-bus access-based energy storage adaptive flexible control method according to claim 1, wherein a functional relationship between the total discharge power limit and the set anti-backflow power is as follows:

pfxi is the discharge power limit value of the ith distributed energy storage system;is the total discharge power limit; pg is the real-time power of the high-voltage incoming line cabinet; ps is the real-time power of the energy storage system; py reserves power for forward flow of electric energy; the set anti-reflux power is the value of an analytic expression Ps + Pg-Py;

the functional relationship between the total charging power limit value and the set overload power is as follows:

wherein Pcxi is the charging power limit value of the ith distributed energy storage system;is the total charging power limit; k is a transformer protection overload prevention reserved coefficient; pz is the maximum allowable use power of the original power system; the set overload power is the value of the analytical expression KPz.

8. The distributed multi-bus access-in energy storage adaptive flexible control method according to claim 7, wherein the distributing total discharging power limit value and total charging power limit value and issuing the distributing result to the corresponding distributed energy storage system specifically comprises:

and distributing the total charging power limit value and the total discharging power limit value according to the ratio of the rated charging power limit value and the rated discharging power limit value of each distributed energy storage system to obtain the charging power limit value and the discharging power limit value of each distributed energy storage system, and enabling the charging power limit value and the discharging power limit value to be lower than the corresponding distributed energy storage systems.

Technical Field

The invention relates to a grid-connected control system of a power grid, in particular to a distributed multi-bus access-based energy storage self-adaptive flexible control method.

Background

In recent years, the energy storage market has gradually increased as the cost of lithium ion batteries has decreased. By combining the data of various research institutions, the energy storage cost is on the descending trend from 2010. The price of the lithium ion battery is reduced by nearly 80% in 2010-2017. The rate of price reduction for each type of battery is approximately the same, despite the different prices for the different technologies. According to BNEF data, in 2019, the average price of the global lithium ion battery pack is reduced by 87% compared with 2010, and is reduced to 156 $ I/kWh, and the average price of the Chinese lithium ion battery pack is the lowest, namely 147 $ I/kWh.

Along with economic development, the power difference between the peak-hour power consumption and the valley-hour power consumption of the region is larger and larger, so that the peak-valley power price difference is continuously enlarged by a power grid enterprise, and the valley-hour power consumption is encouraged. And the price of the lithium ion battery pack is reduced, so that the overall cost of the energy storage system is reduced, and the mode that the energy storage system carries out peak clipping and valley filling on the user side to earn the electricity price difference is more feasible.

The distributed energy storage system on the user side has the advantages of flexible access, short construction period and the like. However, after the energy storage system is connected, how to match with the original power system does not affect the stability of the original power system, and is a solution to be urgently needed. At present, according to the peak-valley electricity price period, a charge-discharge time period and charge-discharge power are set for charging and discharging. However, when the load of the power grid is low, the energy storage management system transmits the electric energy generated by the energy storage system back to the power grid, so that the condition of overload or electric energy backflow of the power grid is easily caused, and under the condition, the discharge income is not generated, and the electric energy is also easily examined by the power grid.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art, provides a distributed multi-bus access-based energy storage self-adaptive flexible control method, and solves the problem that when the load of a power grid is low, the generated energy of an energy storage system is reversely transmitted to the power grid, so that the power grid overload or the electric energy reverse flow is easily caused.

The invention relates to a distributed multi-bus access-based energy storage self-adaptive flexible control method, which comprises an anti-reflux strategy step, an anti-overload strategy step and a system operation step;

the anti-reflux strategy step is used for calculating charging power and discharging power which are issued to each distributed energy storage system according to the collected real-time power of the high-voltage incoming cabinet and the collected real-time power of the energy storage system;

the overload prevention strategy step is used for calculating a total charging power limit value and a total discharging power limit value which need to be issued to all distributed energy storage systems according to the collected real-time power of the low-voltage incoming cabinet and the real-time power of the energy storage systems;

the system operation step is used for judging whether the total discharge power limit value meets the functional relation with the set anti-reflux power or not and whether the total charge power limit value meets the functional relation with the set overload power or not, if so, distributing the total discharge power limit value and the total charge power limit value, and sending the distribution result to a corresponding distributed energy storage system; and otherwise, issuing the charging power and the discharging power to the corresponding distributed energy storage system.

By monitoring the real-time power of the high-voltage incoming line side, the low-voltage grid-connected side and the energy storage system side, the self-adaptive flexible control of the energy storage system is realized according to the anti-reflux and anti-overload strategies arranged in the energy management system, the dynamic power regulation is carried out, and the problems that an access bus is overloaded and discharge current is reversely transmitted to a power grid can be solved.

The anti-reflux strategy specifically comprises the following steps:

s11, collecting the real-time power of the high-voltage incoming cabinet and the real-time power of the energy storage system in real time;

s12, judging whether the value of the analytic expression Ps + Pg is larger than or equal to the electric energy forward flow reserved power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total discharge power to zero and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ], and returns to S11;

wherein Pg is the real-time power of the high-voltage incoming cabinet; ps is the real-time power of the energy storage system; pz is the maximum allowable use power of the original power system;

s13, judging whether the value of the analytic expression Ps + Pg-Py is larger than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total discharge power of the energy storage system to a value of an analytic expression Ps + Pg-Py and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ], and returns to S11;

py reserves power for forward flow of electric energy;

s14, the energy management system assigns the total discharge power to the total rated power of the energy storage system and assigns the total charge power to an analytic expression- [ Pz- (Ps + Pg)]According to the formulaDetermining the discharge power of the distributed energy storage system according to a formulaDetermining charging power of a distributed energy storage system;

pfn is the discharge power of the nth distributed energy storage system; pcn is the charging power of the nth distributed energy storage system; pf is the total discharge power; pc is the total charging power; pe is the total rated power of the energy storage system; and Pen is the rated power of the nth distributed energy storage system.

In S14, after the energy management system has assigned the total discharge power and the total charge power, the energy management system returns to S11 to monitor the condition of the power grid in real time, so as to effectively prevent the situation of electric energy backflow when the power grid changes, and improve the reliability of the system.

The overload prevention strategy specifically comprises the following steps:

s21, collecting real-time power of the low-voltage incoming cabinet and real-time power of the energy storage system in real time;

s22, judging whether the real-time power of the low-voltage incoming cabinet is larger than or equal to zero, and if so, carrying out the next step; otherwise, jumping to S27;

s23, judging whether the real-time power of the energy storage system is less than or equal to zero, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

k is a reserved overload protection coefficient of the transformer; q is the capacity of the low-voltage bus allowed to operate; ps is the real-time power of the energy storage system; pd is the real-time power of the low-voltage incoming cabinet;

s24, judging whether the real-time power of the low-voltage incoming cabinet is less than or equal to the value of the product of the transformer protection overload prevention reserved coefficient and the capacity of the low-voltage bus allowed to run, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

s25, judging whether the value of the analytic expression KQ- (Ps + Pd) is less than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total charging power limit value as a negative value of the total rated power of the energy storage system, and assigns the total discharging power limit value as a value of an analytic formula KQ + (Ps + Pd); and returns to S21;

s26, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd);

s27, judging whether the real-time power of the energy storage system is larger than or equal to zero, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

s28, judging whether the negative value of the real-time power of the low-voltage incoming line cabinet is less than or equal to the value of the product of the transformer protection overload prevention reserved coefficient and the capacity of the low-voltage bus allowed to run, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21;

s29, judging whether the value of the analytic expression KQ + (Ps + Pd) is less than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value to the total rated power of the energy storage system; and returns to S21;

s30, the energy management system assigns the total charging power limit value to a value of an analytic expression- [ KQ- (Ps + Pd) ] and assigns the total discharging power limit value to a value of an analytic expression KQ + (Ps + Pd).

In S26, after the energy management system has assigned the total charging power limit and the total discharging power limit, the process returns to S21 to prevent the bus from being overloaded when the grid changes, thereby improving the reliability of the system.

In S30, after the energy management system has assigned the total charging power limit and the total discharging power limit, the process returns to S21 to prevent the bus from being overloaded when the grid changes, thereby improving the reliability of the system.

The function relation between the total discharge power limit value and the set anti-backflow power is as follows:

pfxi is the discharge power limit value of the ith distributed energy storage system;is the total discharge power limit; pg is the real-time power of the high-voltage incoming line cabinet; ps is the real-time power of the energy storage system; py reserves power for forward flow of electric energy; the set anti-reflux power is the value of an analytic expression Ps + Pg-Py;

the functional relationship between the total charging power limit value and the set overload power is as follows:

wherein Pcxi is the charging power limit value of the ith distributed energy storage system;is the total charging power limit; k is a transformer protection overload prevention reserved coefficient; pz is the maximum allowable use power of the original power system; the set overload power is the value of the analytical expression KPz.

The method comprises the following steps of distributing a total discharge power limit value and a total charge power limit value, and issuing a distribution result to a corresponding distributed energy storage system, wherein the distribution result comprises the following specific steps:

and distributing the total charging power limit value and the total discharging power limit value according to the ratio of the rated charging power limit value and the rated discharging power limit value of each distributed energy storage system to obtain the charging power limit value and the discharging power limit value of each distributed energy storage system, and enabling the charging power limit value and the discharging power limit value to be lower than the corresponding distributed energy storage systems.

Advantageous effects

The invention has the advantages that: by monitoring the real-time power of the high-voltage incoming line side, the low-voltage grid-connected side and the energy storage system side, the self-adaptive flexible control of the energy storage system is realized according to the anti-reflux and anti-overload strategies arranged in the energy management system, the dynamic power regulation is carried out, and the problems that an access bus is overloaded and discharge current is reversely transmitted to a power grid can be solved.

Drawings

FIG. 1 is a schematic diagram of a distributed energy storage system of the present invention accessing a primary power system;

FIG. 2 is a flow chart of a control strategy of the present invention;

FIG. 3 is a flow chart of the anti-reflux strategy steps of the present invention;

fig. 4 is a flowchart of the overload prevention strategy steps of the present invention.

Detailed Description

The invention is further described below with reference to examples, but not to be construed as being limited thereto, and any number of modifications which can be made by anyone within the scope of the claims are also within the scope of the claims.

Referring to fig. 1 to fig. 3, the distributed multi-bus access-based energy storage adaptive flexible control method of the present invention includes an anti-reflux strategy step, an anti-overload strategy step, and a system operation step. And the anti-reflux strategy step is used for calculating the charging power and the discharging power which are issued to each distributed energy storage system according to the collected real-time power of the high-voltage incoming line cabinet and the real-time power of the energy storage system. It should be noted that the energy storage system of the present embodiment is a generic term of all distributed energy storage systems.

The anti-reflux strategy specifically comprises the following steps:

and S11, acquiring the real-time power of the high-voltage incoming line cabinet and the real-time power of the energy storage system in real time. When the real-time power of the high-voltage incoming cabinet is a positive value, the electric energy flows in, and when the real-time power of the high-voltage incoming cabinet is a negative value, the electric energy is reversely transmitted; when the real-time power of the energy storage system is a positive value, the energy storage system is in a discharging state, and when the real-time power of the energy storage system is a negative value, the energy storage system is in a charging state.

S12, judging whether the value of the analytic expression Ps + Pg is larger than or equal to the electric energy forward flow reserved power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total discharge power to zero and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ], returns to S11, and performs acquisition and judgment again.

Pg in the analytic formula and the analytic formula is the real-time power of the high-voltage incoming cabinet; ps is the real-time power of the energy storage system; pz is the maximum allowable power of the original power system.

S13, judging whether the value of the analytic expression Ps + Pg-Py is larger than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total discharge power of the energy storage system to a value of an analytic expression Ps + Pg-Py and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ], returns to S11, and performs acquisition and judgment again.

Py in the analytic formula reserves power for electric energy forward flow.

And S14, the energy management system assigns the total discharge power to the total rated power of the energy storage system, and assigns the total charge power to a value of an analytic expression- [ Pz- (Ps + Pg) ]. At this time, the total charging and discharging power assignment of the energy storage system is completed. And the energy management system distributes the total charge and discharge power according to the percentage of rated power of each distributed energy storage system. The method comprises the following specific steps:

according to the formulaDetermining the discharge power of the distributed energy storage system according to a formulaA charging power of the distributed energy storage system is determined.

Pfn is the discharge power of the nth distributed energy storage system; pcn is the charging power of the nth distributed energy storage system; pf is the total discharge power, and Pf is more than or equal to 0 and less than or equal to Pe; pc is the total charging power, and-Pe is less than or equal to Pf is less than or equal to 0; pe is the total rated power of the energy storage system; and Pen is the rated power of the nth distributed energy storage system.

In addition, after the energy management system assigns the total discharge power and the total charge power, the operation returns to the step S11, and the real-time power of the high-voltage incoming cabinet and the energy storage system is collected continuously, so that the condition of the power grid is monitored in real time, the condition of electric energy countercurrent when the power grid changes can be effectively prevented, and the reliability of the system is improved.

And the overload prevention strategy step is used for calculating the total charging power limit value and the total discharging power limit value which need to be issued to all the distributed energy storage systems according to the collected real-time power of the low-voltage incoming line cabinet and the real-time power of the energy storage systems. The overload prevention strategy step specifically comprises the following steps:

and S21, acquiring the real-time power of the low-voltage incoming cabinet and the real-time power of the energy storage system in real time. When the real-time power of the low-voltage incoming line cabinet is a positive value, the electric energy flows in, and when the real-time power of the low-voltage incoming line cabinet is a negative value, the electric energy is reversely transmitted.

S22, judging whether the real-time power of the low-voltage incoming cabinet is larger than or equal to zero, and if so, carrying out the next step; otherwise, it jumps to S27. When the real-time power of the low-voltage incoming cabinet is larger than or equal to zero, the energy management system assigns values to the total charge-discharge power limit value through S23-S26; when the real-time power of the low-voltage incoming cabinet is less than zero, the energy management system assigns values to the total charging and discharging power limit value through S27-S30.

S23, judging whether the real-time power of the energy storage system is less than or equal to zero, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21 to make the acquisition judgment again.

The analytic expression and K in the analytic expression are reserved coefficients for protecting the transformer from overload; q is the capacity of the low-voltage bus allowed to operate; ps is the real-time power of the energy storage system; pd is the real-time power of the low-voltage incoming cabinet.

S24, judging whether the real-time power of the low-voltage incoming cabinet is less than or equal to the value of the product of the transformer protection overload prevention reserved coefficient and the capacity of the low-voltage bus allowed to run, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21 to make the acquisition judgment again.

S25, judging whether the value of the analytic expression KQ- (Ps + Pd) is less than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total charging power limit value as a negative value of the total rated power of the energy storage system, and assigns the total discharging power limit value as a value of an analytic formula KQ + (Ps + Pd); and returns to S21.

S26, the energy management system assigns the total charging power limit value to a value of an analytic expression- [ KQ- (Ps + Pd) ] and assigns the total discharging power limit value to a value of an analytic expression KQ + (Ps + Pd). At this time, after the total charge and discharge power limit value is assigned, a system operation step can be performed to determine that the system finally operates in a counter-current prevention strategy or an overload prevention strategy.

In addition, in the step, after the energy management system assigns the total charging power limit value and the total discharging power limit value, the energy management system continues to return to the step S21 to monitor the condition of the power grid in real time, so that the condition that the bus is overloaded when the power grid changes is prevented, and the reliability of the system is effectively improved.

S27, judging whether the real-time power of the energy storage system is larger than or equal to zero, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21.

S28, judging whether the negative value of the real-time power of the low-voltage incoming line cabinet is less than or equal to the value of the product of the transformer protection overload prevention reserved coefficient and the capacity of the low-voltage bus allowed to run, and if so, carrying out the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value as a value of an analytic expression KQ + (Ps + Pd); and returns to S21.

S29, judging whether the value of the analytic expression KQ + (Ps + Pd) is less than or equal to the total rated power of the energy storage system, and if so, performing the next step; otherwise, the energy management system assigns the total charging power limit value as a value of an analytic expression- [ KQ- (Ps + Pd) ], and assigns the total discharging power limit value to the total rated power of the energy storage system; and returns to S21.

S30, the energy management system assigns the total charging power limit value to a value of an analytic expression- [ KQ- (Ps + Pd) ] and assigns the total discharging power limit value to a value of an analytic expression KQ + (Ps + Pd). And returning to the step S21 after the energy management system assigns the total charging power limit value and the total discharging power limit value.

After the calculation and analysis are carried out according to the real-time situation of the power grid through the anti-reflux strategy step and the anti-overload strategy step, the energy management system can further analyze the analysis result through the system operation step so as to determine the operation mode which can finally realize the anti-reflux and anti-overload. Specifically, the system operation step is used for judging whether the total discharge power limit value meets a functional relationship with the set anti-backflow power or not and whether the total charge power limit value meets a functional relationship with the set overload power or not, if so, distributing the total discharge power limit value and the total charge power limit value, and sending a distribution result to the corresponding distributed energy storage system; and otherwise, transmitting the charging power and the discharging power to the corresponding distributed energy storage system.

The method comprises the following steps of distributing a total discharge power limit value and a total charge power limit value, and issuing a distribution result to a corresponding distributed energy storage system, wherein the method specifically comprises the following steps:

and distributing the total charging power limit value and the total discharging power limit value according to the occupation ratio of the rated charging power limit value and the rated discharging power limit value of each distributed energy storage system to obtain the charging power limit value and the discharging power limit value of each distributed energy storage system, and putting the charging power limit value and the discharging power limit value below the corresponding distributed energy storage systems.

The functional relation between the total discharge power limit value and the set anti-backflow power is as follows:

pfxi is the discharge power limit value of the ith distributed energy storage system;is the total discharge power limit; pg is the real-time power of the high-voltage incoming line cabinet; ps is the real-time power of the energy storage system; py reserves power for forward flow of electric energy; the set power for preventing reverse flow is the value of the analytic expression Ps + Pg-Py.

The functional relationship between the total charging power limit and the set overload power is as follows:

wherein Pcxi is the charging power limit value of the ith distributed energy storage system;is the total charging power limit; k is a transformer protection overload prevention reserved coefficient; pz is the maximum allowable use power of the original power system; the set overload power is the value of the analytical expression KPz.

That is, when the total charge-discharge power limit value satisfies the two functional relations, the energy management system operates in an overload prevention strategy; and when the total charge-discharge power limit value does not satisfy the two functional relations, the energy management system operates in an anti-backflow strategy. However, since the energy management system simultaneously monitors the real-time condition of the power grid through the backflow prevention strategy step and the overload prevention strategy step, the energy management system has backflow prevention and overload prevention functions no matter what strategy the energy management system operates. And in the running process of the energy management system, the power grid is continuously monitored, so that the system has the functions of dynamically and flexibly adjusting the charge and discharge power, preventing overload and preventing reverse flow, can be matched with the original power system, and ensures the normal work of the energy storage system and the stability of the original power system.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various changes and modifications without departing from the structure of the invention, which will not affect the effect of the invention and the practicability of the patent.