CN115085177A

CN115085177A - Energy storage system SOC (System on chip) balancing method and system sharing DC bus

Info

Publication number: CN115085177A
Application number: CN202210748386.9A
Authority: CN
Inventors: 练净雯; 许清荣; 朱志煌; 李国伟; 张新池
Original assignee: Fujian Times Nebula Technology Co Ltd
Current assignee: Fujian Times Nebula Technology Co Ltd
Priority date: 2022-06-29
Filing date: 2022-06-29
Publication date: 2022-09-20

Abstract

The invention provides a method and a system for balancing the SOC of an energy storage system sharing a direct current bus, which comprises the following steps: the host EMS controls the working mode of the DC/DC converter according to the working state of the energy storage converter PCS, the working state of the electric cabinet and the SOC; the system comprises a PCS, an electric cabinet and a DC/DC converter, wherein the PCS, the electric cabinet and the DC/DC converter are arranged in each subsystem of an energy storage system, the PCS, the DC/DC converter and the electric cabinet are sequentially connected in each subsystem, the subsystems are connected to a power grid in parallel, and the connection part of each PCS and the DC/DC converter is connected in parallel through a direct current bus; according to the invention, independent regulation and control of the subsystems are realized by configuring the PCS for each subsystem, the DC/DC converters of each subsystem share one direct current bus, when the SOC is unbalanced, the host EMS can timely regulate and control the working mode of the DC/DC converter, and the electric quantity among the electric cabinets is transferred under the direct current bus so as to balance the consistency of the charging and discharging currents of each subsystem, so that the problem of nonuniform electric quantity among the electric cabinets of the energy storage system is solved.

Description

Energy storage system SOC (System on chip) balancing method and system sharing DC bus

Technical Field

The invention relates to the technical field of energy storage systems, in particular to a method and a system for balancing an SOC of an energy storage system sharing a direct current bus.

Background

The charging current of the electric cabinet of the current Energy storage System adopts an Energy Management System (EMS) to issue a total current to a Power Conversion System (PCS), and the electric cabinet freely distributes charging and discharging currents.

However, the internal impedance of the electric cabinets is inconsistent, which causes the deviation of the actual current between the electric cabinets, so that the SOC difference between the electric cabinets is large, and the SOC difference between the electric cabinets causes the circulation problem between the electric cabinets, which causes some of the electric cabinets to be insufficiently charged and each electric cabinet to be discharged unevenly, and increases the electric quantity loss.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method and the system for balancing the SOC of the energy storage system sharing the DC bus are provided, and the problem of nonuniform electric quantity among electric cabinets of the energy storage system is solved.

In order to solve the technical problems, the invention adopts the technical scheme that:

an energy storage system SOC balancing method of a common direct current bus comprises the following steps:

s1, controlling the working mode of the DC/DC converter by the host EMS according to the working state of the energy storage converter PCS, the working state of the electric cabinet and the SOC;

the PCS, the electric cabinet and the DC/DC converter are respectively configured in each subsystem of an energy storage system, in each subsystem, the PCS, the DC/DC converter and the electric cabinet are sequentially connected, one end of each PCS, which is not connected with the DC/DC converter, is connected to a power grid in parallel, and the connection position of each PCS and the DC/DC converter is connected in parallel through a direct current bus.

In order to solve the technical problem, the invention adopts another technical scheme as follows:

a common direct current bus energy storage system SOC balance system comprises a host EMS, wherein the host EMS comprises a first memory, a first processor and a first computer program which is stored on the first memory and can run on the first processor,

the first processor, when executing the first computer program, implements the steps of:

s1, controlling the working mode of the DC/DC converter according to the working state of the energy storage converter PCS, the working state of the electric cabinet and the SOC;

The invention has the beneficial effects that: the invention provides an energy storage system SOC balancing method and system sharing a direct current bus, wherein a PCS is configured for a plurality of subsystems of an energy storage system to realize independent regulation and control of the subsystems, a direct current bus is shared by DC/DC converters of the subsystems, a constant voltage mode is set for the DC/DC converters of the subsystems under a default condition, when the SOC of each electric cabinet is unbalanced, a host EMS can timely regulate and control the working mode of the DC/DC converters according to the working states of the PCS and the electric cabinet and the SOC of each electric cabinet, and electric quantity among the electric cabinets is transferred under the direct current bus to balance the consistency of the charging and discharging currents of the subsystems, so that the problem of non-uniform electric quantity among the electric cabinets of the energy storage system is solved.

Drawings

FIG. 1 is a diagram of a topology of a prior art energy storage system;

fig. 2 is a topology structure diagram of an energy storage system sharing a dc bus according to an embodiment of the present invention;

fig. 3 is a flowchart of an energy storage system SOC equalization method for a common dc bus according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of an energy storage system SOC equalization system sharing a dc bus according to an embodiment of the present invention.

Description of reference numerals:

10. an energy storage system SOC balance system with a common direct current bus;

20. a host EMS; 21. a first memory; 22. a first processor;

30. a slave EMS; 31. a second memory; 32. a second processor.

Detailed Description

In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

Referring to fig. 2 to 3, an SOC equalization method for an energy storage system with a common dc bus includes the steps of:

As can be seen from the above description, the beneficial effects of the present invention are: the system comprises a plurality of subsystems of an energy storage system, a power management system (PCS) and a host computer (EMS), wherein the PCS is respectively configured for the subsystems of the energy storage system to realize independent regulation and control of each subsystem, the DC/DC converters of each subsystem share one direct current bus, the DC/DC converters of each subsystem are set to adopt a constant voltage mode under the default condition, when the SOC of each electric cabinet is unbalanced, the host computer (EMS) can timely regulate and control the working mode of the DC/DC converters according to the working states of the PCS and the electric cabinet and the SOC of each electric cabinet, and the electric quantity among the electric cabinets is transferred under the direct current bus to balance the consistency of the charging and discharging currents of each subsystem, so that the problem of non-uniform electric quantity among the electric cabinets of the energy storage system is solved.

Further, the step S1 is preceded by the step of:

s0, detecting and collecting the working state of the PCS, the working state of the electric cabinet and the SOC of the electric cabinet of each subsystem in real time by a slave EMS of each subsystem, and sending the working state, the working state and the SOC to the master EMS;

the working state of the PCS comprises an operating state and a stopping state, wherein the PCS converts alternating current on the power grid side into direct current or converts the direct current into alternating current and enters the power grid side in the operating state, and the PCS stops electric energy conversion in the stopping state;

the working state of the electric cabinet comprises a charging state and a discharging state.

As can be seen from the above description, each subsystem is also provided with a slave EMS for real-time detecting the operating states of the PCS and the electrical cabinets in each subsystem and real-time collecting the SOC of each electrical cabinet, and sending the operating states to the master EMS in time for analysis and power value transmission, i.e., the slave EMS is responsible for transmitting information, and the master EMS is responsible for controlling DC transmission, and has clear division of power and no interference with each other, thereby facilitating the regulation and control of the operating mode of the DC/DC converter of each subsequent subsystem.

Further, the step S1 is specifically:

the master EMS receives and analyzes the working state of each PCS sent by the slave EMS, when the working state of each PCS is the stop state, the step S11 is executed, when the working state of each PCS is the running state, the step S12 is executed, otherwise, a fault alarm is carried out;

s11, the master EMS receives and analyzes the SOC of each electric cabinet sent by the slave EMS:

if the SOC of a first electric cabinet is 20% higher than the lowest SOC of other electric cabinets, controlling the DC/DC converter in the subsystem where the first electric cabinet is located to equally divide the electric quantity output of the first electric cabinet into the rest subsystems at the output power of 10% of rated power, and controlling the DC/DC converters in the rest subsystems to keep a constant voltage mode;

if the SOC of a second electric cabinet is lower than 20% of the highest SOC in other electric cabinets, controlling the DC/DC converters in the subsystems where the other electric cabinets except the second electric cabinet are located to output the electric quantity of the electric cabinet in each subsystem to the subsystem where the second electric cabinet is located at the output power of 2% of rated power, and controlling the DC/DC converters in the subsystems where the second electric cabinet is located to keep a constant voltage mode;

if the highest SOC is 20% higher than the lowest SOC and the lowest SOC is 10% lower than the next-lowest SOC in the SOCs of the electric cabinets, controlling the DC/DC converter in the subsystem where the first highest electric cabinet with the highest SOC is located to output the electric quantity of the first highest electric cabinet with the output power of 10% of the rated power, controlling the DC/DC converter in the subsystem where the first lowest electric cabinet with the lowest SOC is located to receive the electric quantity output by the first highest electric cabinet with the input power of 10% of the rated power to charge the first lowest electric cabinet, and controlling the DC/DC converters in the rest subsystems to keep in a constant voltage mode;

otherwise the DC/DC converters in each subsystem are kept in a constant voltage mode;

and S12, the master EMS receives and analyzes the working state and the SOC of each electric cabinet sent by the slave EMS, and controls the working mode of the DC/DC converter according to the working state and the SOC of the electric cabinet.

As can be seen from the above description, when the PCS is in a stop state, that is, when the PCS stops power conversion, the ac power input to the energy storage system at the grid side is not converted into DC power and is transmitted to the electrical cabinets of the subsystems for energy storage or power supply in the DC load, but if the SOC of the electrical cabinets of the subsystems is unbalanced, and a single too high state, a single too low state, or a high state and a low state occur, the DC/DC converter may be controlled to output or input the electric quantity of the electrical cabinets to other subsystems under the action of the common DC bus or to ensure the balance and consistency of the SOC among the electrical cabinets of the subsystems according to the SOC state of the electrical cabinets of the subsystems.

Further, in step S12, the operating mode of the DC/DC converter is controlled according to the operating state and the SOC of the electrical cabinet, specifically:

when the working state of each electric cabinet is the charging state, executing a step S13, when the working state of each electric cabinet is the discharging state, executing a step S14, otherwise, performing fault warning;

s13, the master EMS receives and analyzes the SOC of each electric cabinet sent by the slave EMS:

if the SOC of a third electric cabinet is 20% higher than the lowest SOC of other electric cabinets, controlling the DC/DC converter in the subsystem where the third electric cabinet is located to store the direct current converted from the power grid side through the PCS into the third electric cabinet with the charging power of 80% of the rated power, and controlling the DC/DC converters in the other subsystems to keep in a constant voltage mode;

if the SOC of a fourth electric cabinet is lower than 20% of the highest SOC of other electric cabinets, controlling the DC/DC converter in the subsystem where the fourth electric cabinet is located to store the direct current converted from the power grid side through the PCS into the fourth electric cabinet with the charging power of 120% of the rated power, and controlling the DC/DC converters in the other subsystems to keep in a constant voltage mode;

if the highest SOC is 20% higher than the lowest SOC and the lowest SOC is 10% lower than the next-lowest SOC among the SOCs of the electric cabinets, controlling the DC/DC converter in the subsystem where the second highest electric cabinet with the highest SOC is located to store the direct current converted from the grid side through the PCS into the second highest electric cabinet with a charging power of 80% of a rated power, controlling the DC/DC converter in the subsystem where the second lowest electric cabinet with the lowest SOC is located to store the direct current converted from the grid side through the PCS into the second lowest electric cabinet with a charging power of 120% of the rated power, and controlling the DC/DC converters in the remaining subsystems to maintain a constant voltage mode;

s24, the master EMS receives and analyzes the SOC of each electric cabinet sent by the slave EMS: if the SOC of a fifth electric cabinet is 20% higher than the lowest SOC of other electric cabinets, controlling the DC/DC converter in the subsystem where the fifth electric cabinet is located to store the direct current converted from the power grid side through the PCS into the fifth electric cabinet with the charging power of 120% of the rated power, and controlling the DC/DC converters in the other subsystems to keep in a constant voltage mode;

if the SOC of a sixth electric cabinet is lower than 20% of the highest SOC in other electric cabinets, controlling the DC/DC converter in the subsystem where the sixth electric cabinet is located to store the direct current converted from the power grid side through the PCS into the sixth electric cabinet with the charging power of 80% of the rated power, and controlling the DC/DC converters in the other subsystems to keep in a constant voltage mode;

if the highest SOC is 20% higher than the lowest SOC and the lowest SOC is 10% lower than the next-lowest SOC among the SOCs of the electric cabinets, controlling the DC/DC converter in the subsystem where the third highest electric cabinet with the highest SOC is located to store the direct current converted from the grid side through the PCS into the third highest electric cabinet with a charging power of 120% of a rated power, controlling the DC/DC converter in the subsystem where the third lowest electric cabinet with the lowest SOC is located to store the direct current converted from the grid side through the PCS into the third lowest electric cabinet with a charging power of 80% of the rated power, and controlling the DC/DC converters in the remaining subsystems to maintain a constant voltage mode;

otherwise the DC/DC converters in each of the subsystems remain in constant voltage mode.

As can be seen from the above description, when the PCS is in the operating state, that is, the PCS converts the ac power at the power grid side into the DC power and outputs the DC power to the electric cabinets of the subsystems to charge energy or supply power to the DC loads, and the electric cabinets at this time may have a state of being charged by the DC power converted by the PCS at the power grid side or a state of supplying power to the DC loads together with the DC power converted by the PCS at the power grid side, and when a single over-high state, a single under-low state, or a single over-low state occurs in the SOC of the electric cabinets, the DC/DC converters may be controlled according to the SOC states of the electric cabinets in the subsystems to adjust the charging or discharging power of the electric cabinets in the subsystems, so as to ensure the balance of charging and discharging among the electric cabinets of the subsystems, and further ensure the balance and consistency of the SOCs among the electric cabinets of the subsystems.

Further, if the SOC of the first electrical cabinet is 20% higher than the lowest SOC of the other electrical cabinets in step S11, the method further includes the steps of:

analyzing the difference value between the SOC of the first electric cabinet and the lowest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the first electric cabinet is located to be 0 when the difference value is less than 3%;

if the SOC of the second electrical cabinet is lower than 20% of the highest SOC of the other electrical cabinets in step S11, the method further includes:

analyzing the difference value between the SOC of the second electric cabinet and the highest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%;

in step S11, if the highest SOC is 20% higher than the lowest SOC and the lowest SOC is 10% lower than the second lowest SOC, the method further includes the steps of:

analyzing a difference value between the highest SOC and the lowest SOC in real time, and when the difference value is less than 3%, adjusting the output power of the DC/DC converter in the subsystem where the first highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the first lowest electric cabinet is located to be 0;

if the SOC of the third electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in step S13, the method further includes:

analyzing the difference value between the SOC of the third electric cabinet and the lowest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the third electric cabinet is located to be 0 when the difference value is less than 3%;

if the SOC of the fourth electrical cabinet is lower than 20% of the highest SOC of the other electrical cabinets in step S13, the method further includes:

analyzing the difference value of the SOC of the fourth electric cabinet and the highest SOC in the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%;

in step S13, if the highest SOC is 20% higher than the lowest SOC and the lowest SOC is 10% lower than the second lowest SOC, the method further includes the steps of:

analyzing a difference value between the highest SOC and the lowest SOC in real time, and when the difference value is less than 3%, adjusting the output power of the DC/DC converter in the subsystem where the second highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the second lowest electric cabinet is located to be 0;

if the SOC of the fifth electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in the step S14, the method further includes the steps of:

analyzing the difference value between the SOC of the fifth electric cabinet and the lowest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the fifth electric cabinet is located to be 0 when the difference value is less than 3%;

if the SOC of the sixth electrical cabinet is lower than 20% of the highest SOC of the other electrical cabinets in step S14, the method further includes:

analyzing the difference value between the SOC of the sixth electric cabinet and the highest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%;

in step S14, if the highest SOC is 20% higher than the lowest SOC and the lowest SOC is 10% lower than the second lowest SOC, the method further includes the steps of:

and analyzing the difference value between the highest SOC and the lowest SOC in real time, and regulating the output power of the DC/DC converter in the subsystem where the third highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the third lowest electric cabinet is located to be 0 when the difference value is less than 3%.

As can be seen from the above description, after the DC/DC converters in each subsystem are controlled to execute corresponding input and output powers, the states of the SOCs between the electrical cabinets of each subsystem need to be monitored in real time, so as to stop the set working mode of the DC/DC converters in time when the SOC states are close to the same state, and resume each DC/DC converter to be in the constant voltage mode, thereby preventing the DC/DC converters in the subsystems with higher or lower SOCs from continuously inputting or outputting the electrical quantity of the electrical cabinet of the subsystem in which the DC/DC converters are located to other subsystems, which causes imbalance in reverse SOC compared to the previous subsystems; similarly, after the DC/DC converters in each subsystem are controlled to execute corresponding charging and discharging powers, the states of the SOCs between the electrical cabinets of each subsystem also need to be monitored in real time, so as to stop the set working mode of the DC/DC converters in time when the SOC states are close to be consistent, and recover each DC/DC converter to be in the constant voltage mode again, thereby avoiding imbalance that the DC/DC converters in the subsystems with higher or lower SOCs continuously work with higher or lower charging and discharging powers to cause the electric quantity of the electrical cabinet of the subsystem where the DC/DC converters are located to be overcharged or overdischarged to cause the inverse direction of the SOC between the electrical cabinets before being compared.

Referring to fig. 4, an energy storage system SOC equalization system with common dc bus includes a host EMS, the host EMS includes a first memory, a first processor, and a first computer program stored in the first memory and running on the first processor,

As can be seen from the above description, the beneficial effects of the present invention are: based on the same technical concept, the energy storage system SOC balancing system sharing the direct current bus is provided by matching with the energy storage system SOC balancing method sharing the direct current bus, independent regulation and control of each subsystem are realized by configuring a PCS for a plurality of subsystems of the energy storage system, a direct current bus is shared by DC/DC converters of each subsystem, the DC/DC converters of each subsystem are set to adopt a constant voltage mode under the default condition, when the SOC of each electric cabinet is unbalanced, a host EMS can timely regulate and control the working mode of the DC/DC converters according to the working states of the PCS and the electric cabinet and the SOC of each electric cabinet, electric quantity among the electric cabinets is transferred under the direct current bus to balance the consistency of the charging and discharging currents of each subsystem, and the problem that the electric quantity among the electric energy storage system electric cabinets is not equalized is solved.

Further, a slave EMS is included, the slave EMS including a second memory, a second processor, and a second computer program stored on the second memory and executable on the second processor;

the second processor, when executing the second computer program, implements the steps of:

s0, detecting and collecting the working state of the PCS, the working state of the electric cabinet and the SOC of the electric cabinet under each subsystem in real time, and sending the working states to the host EMS;

the working state of the PCS comprises an operating state and a stopping state, wherein the PCS converts alternating current on a power grid side into direct current or converts the direct current into alternating current and enters the power grid side in the operating state, and the PCS stops electric energy conversion in the stopping state;

Further, the step S1 is specifically:

receiving and analyzing the working state of each PCS sent by the slave EMS, executing a step S11 when the working state of each PCS is the stop state, executing a step S12 when the working state of each PCS is the running state, and otherwise, performing fault warning;

s11, receiving and analyzing the SOC of each electric cabinet sent by the slave EMS:

and S12, receiving and analyzing the working state and SOC of each electric cabinet sent by the slave EMS, and controlling the working mode of the DC/DC converter according to the working state and SOC of the electric cabinet.

when the working state of each electric cabinet is the charging state, executing step S13, when the working state of each electric cabinet is the discharging state, executing step S14, otherwise, performing fault warning;

s13, receiving and analyzing the SOC of each electric cabinet sent by the slave EMS:

s24, receiving and analyzing the SOC of each electric cabinet sent by the slave EMS: if the SOC of a fifth electric cabinet is 20% higher than the lowest SOC of other electric cabinets, controlling the DC/DC converter in the subsystem where the fifth electric cabinet is located to store the direct current converted from the power grid side through the PCS into the fifth electric cabinet with the charging power of 120% of the rated power, and controlling the DC/DC converters in the other subsystems to keep in a constant voltage mode;

if there is a highest SOC which is 20% higher than the lowest SOC and a lowest SOC which is 10% lower than the next lowest SOC among the SOCs of the electric cabinets, controlling the DC/DC converter in the subsystem where a third highest electric cabinet having the highest SOC is located to store the DC power converted from the grid side through the PCS into the third highest electric cabinet with a charging power of 120% of a rated power, controlling the DC/DC converter in the subsystem where a third lowest electric cabinet having the lowest SOC is located to store the DC power converted from the grid side through the PCS into the third lowest electric cabinet with a charging power of 80% of a rated power, and controlling the DC/DC converters in the remaining subsystems to maintain a constant voltage mode;

Further, if the SOC of the first electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in step S11, the method further includes the steps of:

analyzing the difference value between the SOC of the fourth electric cabinet and the highest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%;

analyzing a difference value between the highest SOC and the lowest SOC in real time, and regulating the output power of the DC/DC converter in the subsystem where the second highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the second lowest electric cabinet is located to be 0 when the difference value is less than 3%;

The method and the system for balancing the SOC of the energy storage system sharing the DC bus are suitable for the energy storage system formed by a plurality of subsystems and can be used for continuously adding or reducing the subsystems, and are specifically described below by combining with an embodiment.

Referring to fig. 1 to fig. 3, a first embodiment of the present invention is:

on the basis of the existing energy storage system topology structure which is composed of a plurality of subsystems and is shown in figure 1, in the embodiment, as shown in figure 2, a PCS energy storage converter is added for each subsystem to be connected with a power grid side and a power cabinet side, wherein one end of a PCS of each subsystem is connected with the power grid in parallel, the other end of the PCS of each subsystem is connected with a DC/DC converter and the power cabinet in sequence, the connection part of the PCS of each subsystem and the DC/DC converter is connected with each other in parallel through a direct current bus, and the direct current buses can perform mutual current flowing among the subsystems.

In this embodiment, the PCS energy storage converter employs a bidirectional AC/DC converter, and when the PCS operates as an AC/DC rectifier, the PCS rectifies the AC power at the grid side into a DC power, and then the DC power is adjusted by the DC/DC converter and then input to an electric cabinet for charging or supplies power to a DC load. It should be noted that the ac power at the grid side may also be directly supplied to the ac load without being inverted into dc power by the PCS, that is, as shown in fig. 1; meanwhile, if the PCS serves as a DC/AC inverter, the direct current output by power regulation of the electric cabinet side through the DC/DC converter can be inverted into alternating current to supply power to an alternating current load.

As shown in fig. 3, in the present embodiment, the method includes the steps of:

s0, detecting and collecting the working state of PCS, the working state of the electric cabinet and the SOC of the electric cabinet of each subsystem from the EMS in real time, and sending the working states to the host EMS;

the working state of the PCS comprises an operating state and a stopping state, the PCS converts alternating current on the power grid side into direct current or converts the direct current into alternating current and enters the power grid side in the operating state, and the PCS stops electric energy conversion in the stopping state;

And S1, controlling the working mode of the DC/DC converter by the host EMS according to the working state of the energy storage converter PCS, the working state of the electric cabinet and the SOC.

In the embodiment, a PCS is configured for each of the subsystems of the energy storage system to realize individual regulation of each subsystem, the DC/DC converters of each subsystem share one DC bus, the slave EMS detects the operating states of the PCS and the electrical cabinets in each subsystem in real time, acquires the SOC of each electrical cabinet in real time, and transmits the SOC to the host EMS, the DC/DC converters of each subsystem are set to adopt a constant voltage mode under a default condition, when the SOCs of the electrical cabinets are unbalanced, the host EMS can regulate and control the operating mode of the DC/DC converters in time according to the operating states of the PCS and the electrical cabinets and the SOCs of the electrical cabinets, and the electric quantity among the electrical cabinets is transferred under the DC bus to balance the consistency of the electric quantity of each subsystem, so as to solve the problem of non-uniform electric quantity among the electrical cabinets of the energy storage system.

In addition, in step S0, each subsystem is also configured with a slave EMS for real-time detecting the operating states of the PCS and the electrical cabinets in each subsystem and real-time collecting the SOC of each electrical cabinet, and sending the operating states to the master EMS in time for analysis and power value issue, i.e., the slave EMS is responsible for transmitting information, the master EMS is responsible for controlling DC issue, the division of labor is clear, and the slave EMS does not interfere with each other, so as to facilitate the regulation and control of the operating mode of the DC/DC converter of each subsequent subsystem.

The second embodiment of the invention is as follows:

on the basis of the first embodiment, in this embodiment, the step S1 specifically includes:

and the master EMS receives and analyzes the working state of each PCS sent by the slave EMS, when the working state of each PCS is the stop state, the step S11 is executed, when the working state of each PCS is the running state, the step S12 is executed, and otherwise, a fault alarm is carried out.

if the SOC of a first electric cabinet is 20% higher than the lowest SOC of other electric cabinets, controlling the DC/DC converter in the subsystem where the first electric cabinet is located to equally divide the electric quantity output of the first electric cabinet into the rest subsystems with the output power of 10% of the rated power, and controlling the DC/DC converters in the rest subsystems to keep a constant voltage mode;

and analyzing the difference value between the SOC of the first electric cabinet and the lowest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the first electric cabinet is located to be 0 when the difference value is less than 3%.

If the SOC of the second electric cabinet is lower than 20% of the highest SOC in other electric cabinets, controlling the DC/DC converters in the subsystems where the other electric cabinets except the second electric cabinet are located to output the electric quantity of the electric cabinet in each subsystem to the subsystem where the second electric cabinet is located at the output power of 2% of rated power, and controlling the DC/DC converters in the subsystems where the second electric cabinet is located to keep a constant voltage mode;

and meanwhile, analyzing the difference value between the SOC of the second electric cabinet and the highest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%.

and meanwhile, analyzing the difference value between the highest SOC and the lowest SOC in real time, and when the difference value is less than 3%, adjusting the output power of the DC/DC converter in the subsystem where the first highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the first lowest electric cabinet is located to be 0.

In this embodiment, in step S12, the operating mode of the DC/DC converter is controlled according to the operating state and the SOC of the electrical cabinet, specifically:

and executing step S13 when the working state of each electric cabinet is the charging state, executing step S14 when the working state of each electric cabinet is the discharging state, and otherwise, performing fault warning.

and meanwhile, analyzing the difference value between the SOC of the third electric cabinet and the lowest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the third electric cabinet is located to be 0 when the difference value is less than 3%.

and meanwhile, analyzing the difference value between the SOC of the fourth electric cabinet and the highest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%.

and meanwhile, analyzing the difference value between the highest SOC and the lowest SOC in real time, and regulating the output power of the DC/DC converter in the subsystem where the second highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the second lowest electric cabinet is located to be 0 when the difference value is less than 3%.

and meanwhile, analyzing the difference value between the SOC of the fifth electric cabinet and the lowest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the fifth electric cabinet is located to be 0 when the difference value is less than 3%.

and meanwhile, analyzing the difference value between the SOC of the sixth electric cabinet and the highest SOC of the rest electric cabinets in real time, and controlling the output power of the DC/DC converter in the subsystem where the rest electric cabinets are located to be 0 when the difference value is less than 3%.

and meanwhile, analyzing the difference value between the highest SOC and the lowest SOC in real time, and regulating the output power of the DC/DC converter in the subsystem where the third highest electric cabinet is located and the input power of the DC/DC converter in the subsystem where the third lowest electric cabinet is located to be 0 when the difference value is less than 3%.

In other words, in this embodiment, when the PCS is in a stop state, that is, when the PCS stops power conversion, the ac power input into the energy storage system at the grid side is not converted into DC power and is transmitted to the electrical cabinets of the subsystems for energy storage or power supply in the DC load, but if the SOC among the electrical cabinets of the subsystems is unbalanced, and a single over-high state, a single under-low state, or a high-low state occurs, the DC/DC converter may be controlled to output or input the electric quantity of the electrical cabinets to other subsystems under the action of the common DC bus or according to the SOC state of the electrical cabinets of the subsystems, so as to ensure the balance and consistency of the SOC among the electrical cabinets of the subsystems.

After the DC/DC converters in each subsystem are controlled to execute corresponding input and output power, the SOC state among the electric cabinets of each subsystem is monitored in real time, so that the set working mode of the DC/DC converters is stopped in time when the SOC states are close to consistency, each DC/DC converter is recovered to be in a constant voltage mode again, the situation that the DC/DC converters in the subsystems with higher or lower SOC continuously input or output the electric quantity of the electric cabinets of the subsystems where the DC/DC converters are located to other subsystems and reverse SOC imbalance is caused is avoided.

Similarly, when the PCS is in the operating state, that is, the PCS converts the ac power at the power grid side into the DC power to output the DC power to the electric cabinets of the subsystems for charging or supplying the DC load, and the electric cabinets at this time may have a state of being charged by the DC power converted by the PCS at the power grid side or a state of supplying the DC load together with the DC power converted by the PCS at the power grid side, and when a single over-high, a single under-low, or a high-low state occurs in the SOC of the electric cabinets, the DC/DC converters may be controlled according to the SOC states of the electric cabinets in the subsystems to adjust the charging or discharging power of the electric cabinets in the subsystems, so as to ensure the balance of charging and discharging among the electric cabinets of the subsystems, and further ensure the balance and consistency of the SOCs among the electric cabinets of the subsystems.

After the DC/DC converters in the subsystems are controlled to execute corresponding charging and discharging powers, the states of the SOC among the electric cabinets of the subsystems also need to be monitored in real time, so that the set working mode of the DC/DC converters is stopped in time when the SOC states are close to consistency, the DC/DC converters are recovered to be in a constant voltage mode again, and unbalance that the SOC among the electric cabinets becomes reverse before the SOC among the electric cabinets is compared due to the fact that the DC/DC converters in the subsystems with higher or lower SOCs continuously work with higher or lower charging and discharging powers is avoided.

It should be noted that, in this embodiment, the operating states of the PCS and the electrical cabinets of the subsystems should be consistent, that is, the host EMS in step S1 needs to analyze whether the operating state of each PCS is the stop state or the operating state, and the host EMS also needs to analyze whether the operating state of each electrical cabinet is the charge state or the discharge state in step S12, otherwise, a fault alarm is generated. The SOC balancing method of the energy storage system sharing the direct current bus is established under the same operation condition of each subsystem of the energy storage system to solve the problems of SOC imbalance and non-uniform charging and discharging currents among the electric cabinets, so that the working states of the PCS of each subsystem and the electric cabinets are necessarily the same.

Referring to fig. 4, a third embodiment of the present invention is:

an energy storage system SOC balancing system 10 with a common direct current bus comprises a master EMS20 and a slave EMS30, wherein the master EMS20 comprises a first memory 21, a first processor 22 and a first computer program stored on the first memory 21 and capable of running on the first processor 22, and the slave EMS30 comprises a second memory 31, a second processor 32 and a second computer program stored on the second memory 31 and capable of running on the second processor 32.

The first processor 22 realizes step S1 as in the first or second embodiment when executing the first computer program, and the second processor 32 realizes step S0 as in the first or second embodiment when executing the second computer program.

In summary, the energy storage system SOC equalization method and system provided by the invention have the following beneficial effects:

1. the subsystems are flexibly expanded and reduced, and the installation is convenient;

2. the problem of SOC unbalance among the electric cabinets of all subsystems is solved.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to the related technical fields, are included in the scope of the present invention.

Claims

1. An energy storage system SOC balancing method sharing a direct current bus is characterized by comprising the following steps:

2. The method for balancing the SOC of the energy storage system of the common direct current bus according to claim 1, wherein the step S1 is preceded by the steps of:

3. The method for balancing the SOC of the energy storage system of the common dc bus according to claim 2, wherein the step S1 specifically includes:

if the highest SOC is 20% higher than the lowest SOC in the SOCs of the electric cabinets and the lowest SOC is 10% lower than the second-lowest SOC, controlling the DC/DC converter in the subsystem where the first highest electric cabinet with the highest SOC is located to output the electric quantity of the first highest electric cabinet with the output power of 10% of the rated power, controlling the DC/DC converter in the subsystem where the first lowest electric cabinet with the lowest SOC is located to receive the electric quantity output by the first highest electric cabinet with the input power of 10% of the rated power to charge the first lowest electric cabinet, and controlling the DC/DC converters in the rest subsystems to keep a constant voltage mode;

4. The method for balancing the SOC of the energy storage system of the common DC bus according to claim 3, wherein in step S12, the operating mode of the DC/DC converter is controlled according to the operating state and the SOC of the electrical cabinet, specifically:

if the SOC of a fourth electric cabinet is lower than 20% of the highest SOC in other electric cabinets, controlling the DC/DC converter in the subsystem where the fourth electric cabinet is located to store the direct current converted from the power grid side through the PCS into the fourth electric cabinet with the charging power of 120% of the rated power, and controlling the DC/DC converters in the other subsystems to keep in a constant voltage mode;

5. The method for balancing SOC of an energy storage system on a common dc bus according to claim 4, wherein if the SOC of the first electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in step S11, the method further comprises the steps of:

if the SOC of the third electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in step S13, the method further includes the steps of:

if the SOC of the fifth electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in step S14, the method further includes the steps of:

6. A common direct current bus energy storage system SOC balance system is characterized by comprising a host EMS, wherein the host EMS comprises a first memory, a first processor and a first computer program which is stored on the first memory and can run on the first processor,

7. The energy storage system SOC balancing system according to claim 6, further comprising a slave EMS, the slave EMS comprising a second memory, a second processor, and a second computer program stored in the second memory and operable on the second processor;

8. The system for SOC equalization of an energy storage system with a common dc bus according to claim 7, wherein the step S1 specifically comprises:

9. The system for SOC equalization of an energy storage system with a common DC bus according to claim 8, wherein in step S12, the operating mode of the DC/DC converter is controlled according to the operating state and SOC of the electrical cabinet, specifically:

10. The system for equalizing the SOC of an energy storage system on a common dc bus according to claim 9, wherein if the SOC of the first electrical cabinet is higher than 20% of the lowest SOC of the other electrical cabinets in step S11, the method further comprises the steps of: