阅读说明：本技术 一种超级电容联合锂电储能进行火电调频的系统 (System for performing thermal power frequency modulation by combining super capacitor with lithium battery energy storage ) 是由 尚德华 贾葳 于 2019-11-07 设计创作，主要内容包括：本发明公开了一种超级电容联合锂电储能进行火电调频的系统,包括储能系统；储能系统由磷酸铁锂电池、超级电容、第一PCS电路、第二PCS电路、DC/DC变换器和中压变压器构成；超级电容、第二PCS电路和DC/DC变换器构成该系统的超级电容储能,磷酸铁锂电池和第一PCS电路构成该系统的锂电池储能。本发明的有益效果是：既能够大功率充放电,又可以实现较大功率较长时间充放电。超级电容单元响应电网小功率的调频指令,对蓄电池储能子系统进行保护,使锂电储能系统能够大功率低倍率充放电,延长其工作寿命,提高系统的经济性；混合储能系统可以减少机组的出力波动,提高调频稳定区的调节精度。(The invention discloses a system for performing thermal power frequency modulation by combining super-capacitor with lithium battery energy storage, which comprises an energy storage system; the energy storage system consists of a lithium iron phosphate battery, a super capacitor, a first PCS circuit, a second PCS circuit, a DC/DC converter and a medium voltage transformer; the super capacitor, the second PCS circuit and the DC/DC converter form the super capacitor energy storage of the system, and the lithium iron phosphate battery and the first PCS circuit form the lithium battery energy storage of the system. The invention has the beneficial effects that: the charging and discharging device can realize high-power charging and discharging and can realize charging and discharging with larger power for a longer time. The super capacitor unit responds to a low-power frequency modulation instruction of a power grid and protects the storage battery energy storage subsystem, so that the lithium battery energy storage system can be charged and discharged at high power and low multiplying power, the service life of the lithium battery energy storage system is prolonged, and the economical efficiency of the system is improved; the hybrid energy storage system can reduce the output fluctuation of the unit and improve the adjustment precision of the frequency modulation stable area.)

1. A system for performing thermal power frequency modulation by combining super capacitor with lithium battery energy storage comprises an energy storage system; the method is characterized in that: the energy storage system consists of a lithium iron phosphate battery, a super capacitor, a first PCS circuit, a second PCS circuit, a DC/DC converter and a medium voltage transformer; the super capacitor, the second PCS circuit and the DC/DC converter form super capacitor energy storage of the system, and the lithium iron phosphate battery and the first PCS circuit form lithium battery energy storage of the system;

the super capacitor energy storage and the lithium battery energy storage are connected in parallel on a direct current bus of the energy storage container, the super capacitor energy storage adopts a two-stage control structure consisting of a triple bidirectional DC/DC converter and a bidirectional grid-connected converter, the lithium battery energy storage system adopts a single-stage control structure, and direct current of the lithium iron phosphate battery is converted into medium-frequency alternating current through a first PCS (power control System) circuit and is connected to the input side of a medium-voltage transformer; a certain number of super capacitors are connected in parallel, a plurality of parallel modules are connected in series to form an energy storage array, the super capacitors are connected in parallel and then connected with a second PCS circuit through a bidirectional DC/DC conversion circuit, the second PCS circuit converts direct current into alternating current through an IGBT module and is electrically connected with the input side of a medium voltage transformer, and the output side of the medium voltage transformer is connected with a service bus of a power plant;

the system work comprises the following steps:

step one, for a short-time/low-power instruction, independently outputting power by a super-capacitor energy storage system

For the power smaller than the configured power of the super-capacitor system, the super-capacitor energy storage system preferentially outputs power alone to respond, the stored energy in the super-capacitor energy storage system can meet the demand of the instruction, or the super-capacitor energy storage system can meet the demand of the instruction by matching with the unit, and the lithium battery energy storage system does not need to act;

step two, for long-time/high-power instructions, the two energy storage systems cooperatively and jointly output power

For a long-time/high-power instruction, the super-capacitor energy storage system is used for outputting to bear the peak power requirement at the initial stage of the instruction preferentially, and when the super-capacitor energy storage system outputs power independently and cannot meet the instruction requirement, the lithium battery energy storage system is used for outputting power in a matched manner;

step three, improving the adjustment precision index of the super capacitor energy storage system

And the super capacitor energy storage system is called to charge and discharge rapidly to make up, so that the adjustment precision index of the frequency modulation of the unit is improved.

2. The system for thermal power frequency modulation by combining super capacitor with lithium battery energy storage according to claim 1, characterized in that: when the thermal power generating unit enters an AGC frequency modulation stable operation stage, the super-capacitor energy storage system compensates the deviation between the actual output of the thermal power generating unit and the target output of the AGC through frequent charging or discharging.

3. The system for thermal power frequency modulation by combining super capacitor with lithium battery energy storage according to claim 1, characterized in that: the energy storage system master control unit and the energy storage system sub-control unit are installed in the centralized control container, and an upper computer is placed in a power plant master control room.

4. The system for thermal power frequency modulation by combining super capacitor with lithium battery energy storage according to claim 1, characterized in that: the energy storage system master control unit is realized with the data communication of unit DCS control system by adopting a communication/hard wiring mode, the energy storage system master control unit is connected with the sub-control units through a field bus, and the controller, the communication clamping pieces, the IO clamping pieces and the control power supply of the energy storage system master control unit are integrally installed in the centralized control container control cabinet.

5. The system for thermal power frequency modulation of super-capacitor combined lithium-ion power storage according to claim 3, characterized in that: the energy storage system control subunit is located within each medium voltage conversion container.

Technical Field

The invention relates to a thermal power frequency modulation system, in particular to a system for performing thermal power frequency modulation by combining a super capacitor with lithium battery energy storage, and belongs to the technical field of thermal power frequency modulation.

Background

In the calculation rule of the conventional thermal power frequency modulation system, the frequency modulation mileage of the power generation unit is taken as a trade target, wherein the most important is a frequency modulation performance index K consisting of three technical indexes, namely the adjustment rate of the power generation unit responding to an AGC control instruction, the response time and the adjustment precision.

In the existing energy storage participation power grid AGC frequency modulation, a power grid AGC scheduling instruction is issued to a thermal power generating unit, an energy storage system simultaneously acquires the AGC instruction and synchronously participates in the frequency modulation, and the energy storage system compensates a power difference value between the unit output and the AGC instruction by utilizing the characteristic of high response speed (second level) of the thermal power generating unit. And after the output of the set is kept up, the output of the energy storage system is gradually reduced so as to ensure that the combined output of the energy storage system and the set is consistent with the AGC instruction.

The lithium battery has the advantages that the lithium battery has higher energy storage density, can realize large-capacity energy storage, has the defect of lower power density, is difficult to realize large-current continuous and quick discharge, and the super capacitor has the advantages of higher power density, high charge and discharge speed, less influence by temperature, more than 10 ten thousand charge and discharge cycle life, but the energy storage density of the super capacitor is lower than that of the lithium battery, so that the situation that the demand of instructions cannot be met can occur during independent output.

Disclosure of Invention

The invention aims to solve the problems and provide a system for performing thermal power frequency modulation by combining a super capacitor with lithium battery energy storage.

The invention realizes the purpose through the following technical scheme: a system for performing thermal power frequency modulation by combining super capacitor with lithium battery energy storage comprises an energy storage system; the energy storage system consists of a lithium iron phosphate battery, a super capacitor, a first PCS circuit, a second PCS circuit, a DC/DC converter and a medium voltage transformer; the super capacitor, the second PCS circuit and the DC/DC converter form super capacitor energy storage of the system, and the lithium iron phosphate battery and the first PCS circuit form lithium battery energy storage of the system; the super capacitor energy storage and the lithium battery energy storage are connected in parallel on a direct current bus of the energy storage container, the super capacitor energy storage adopts a two-stage control structure consisting of a triple bidirectional DC/DC converter and a bidirectional grid-connected converter, the lithium battery energy storage system adopts a single-stage control structure, and direct current of the lithium iron phosphate battery is converted into medium-frequency alternating current through a first PCS (power control System) circuit and is connected to the input side of a medium-voltage transformer; a certain number of super capacitors are connected in parallel, a plurality of parallel modules are connected in series to form an energy storage array, the super capacitors are connected in parallel and then connected with a second PCS circuit through a bidirectional DC/DC conversion circuit, the second PCS circuit converts direct current into alternating current through an IGBT module and is electrically connected with the input side of a medium voltage transformer, and the output side of the medium voltage transformer is connected with a service bus of a power plant;

the system work comprises the following steps:

step one, for a short-time/low-power instruction, independently outputting power by a super-capacitor energy storage system

For the power smaller than the configured power of the super-capacitor system, the super-capacitor energy storage system preferentially outputs power alone to respond, the stored energy in the super-capacitor energy storage system can meet the demand of the instruction, or the super-capacitor energy storage system can meet the demand of the instruction by matching with the unit, and the lithium battery energy storage system does not need to act;

step two, for long-time/high-power instructions, the two energy storage systems cooperatively and jointly output power

For a long-time/high-power instruction, the super-capacitor energy storage system is used for outputting to bear the peak power requirement at the initial stage of the instruction preferentially, and when the super-capacitor energy storage system outputs power independently and cannot meet the instruction requirement, the lithium battery energy storage system is used for outputting power in a matched manner;

step three, improving the adjustment precision index of the super capacitor energy storage system

And the super capacitor energy storage system is called to charge and discharge rapidly to make up, so that the adjustment precision index of the frequency modulation of the unit is improved.

As a still further scheme of the invention: when the thermal power generating unit enters an AGC frequency modulation stable operation stage, the super-capacitor energy storage system compensates the deviation between the actual output of the thermal power generating unit and the target output of the AGC through frequent charging or discharging.

As a still further scheme of the invention: the energy storage system master control unit and the energy storage system sub-control unit are installed in the centralized control container, and an upper computer is placed in a power plant master control room.

As a still further scheme of the invention: the energy storage system master control unit is realized by adopting a communication/hard wiring mode with the data communication of the unit DCS control system, the energy storage system master control unit is connected with the sub-control units through a field bus, and the controller, the communication clamping pieces, the IO clamping pieces, the control power supply and the like of the energy storage system master control unit are integrally installed in the centralized control container control cabinet.

As a still further scheme of the invention: the energy storage system control subunit is located within each medium voltage conversion container.

The invention has the beneficial effects that: the system for thermal power frequency modulation by combining the super capacitor with the lithium battery energy storage is reasonable in design, the advantages of quick charge-discharge response, high-rate charge-discharge, long service life and the like of the super capacitor energy storage system are fully exerted by configuring the lithium battery system and the hybrid energy storage system of the super capacitor system, and the hybrid energy storage system is coordinated with the lithium ion battery energy storage system to jointly assist the thermal power unit to complete AGC frequency modulation, improve the performance index (K value) of AGC frequency modulation, obtain higher frequency modulation mileage compensation, obviously reduce the charge-discharge times of the lithium ion battery and greatly prolong the service life; the hybrid energy storage system can be charged and discharged at high power and can be charged and discharged at higher power for a longer time. The super capacitor unit responds to a low-power frequency modulation instruction of a power grid and protects the storage battery energy storage subsystem, so that the lithium battery energy storage system can be charged and discharged at high power and low multiplying power, the service life of the lithium battery energy storage system is prolonged, and the economical efficiency of the system is improved; the hybrid energy storage system can reduce the output fluctuation of the unit and improve the adjustment precision of the frequency modulation stable area.

Drawings

FIG. 1 is a schematic wiring diagram of the system of the present invention;

FIG. 2 is a power curve diagram illustrating energy storage of a lithium battery according to the present invention;

FIG. 3 is a schematic flow chart of the present invention;

FIG. 4 is a power curve diagram of the hybrid energy storage of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 to 4, a system for performing thermal power frequency modulation by combining a super capacitor and a lithium battery for energy storage includes an energy storage system; the energy storage system consists of a 9MW/4.5MWh lithium iron phosphate battery, a 4MW/120MWs super capacitor, a first PCS circuit, a second PCS circuit, a DC/DC converter and a medium voltage transformer; the 4MW/120MWs super capacitor, the second PCS circuit and the DC/DC converter form super capacitor energy storage of the system, and the 9MW/4.5MWh lithium iron phosphate battery and the first PCS circuit form lithium battery energy storage of the system; the super capacitor energy storage and the lithium battery energy storage are connected in parallel on a 600-plus-1000V energy storage container direct current bus, the super capacitor energy storage adopts a two-stage control structure consisting of a triple bidirectional DC/DC converter and a bidirectional grid-connected converter, the lithium battery energy storage system adopts a single-stage control structure, and direct current of the lithium iron phosphate battery is converted into 6.3kV alternating current through a first PCS circuit and is connected to the input side of a medium-voltage transformer; the system comprises a plurality of super capacitors, a bidirectional DC/DC conversion circuit, a second PCS circuit, a medium voltage transformer, a hybrid energy storage system and a main transformer, wherein the super capacitors are connected in parallel, a plurality of parallel modules are connected in series to form an energy storage array, the super capacitors are connected in parallel and then connected with the second PCS circuit through the bidirectional DC/DC conversion circuit, the second PCS circuit converts direct current into 6.3kV alternating current through an IGBT module and is electrically connected with the input side of the medium voltage transformer, the output side of the medium voltage transformer is connected with a service bus of a power plant, the output of the hybrid energy storage system is connected into a 1# unit or a 2# unit for 6kV service power through a power cable and then is transmitted out through the main transformer of the power plant, the auxiliary power of the;

the system work comprises the following steps:

step one, for a short-time/low-power instruction, independently outputting power by a super-capacitor energy storage system

For the power smaller than the configured power of the super-capacitor system, the super-capacitor energy storage system preferentially outputs power independently to respond, the stored energy in the super-capacitor energy storage system can meet the demand of the instruction, or the super-capacitor energy storage system can meet the demand of the instruction by matching with the unit, the lithium battery energy storage system does not need to act, and the charging and discharging times of the lithium battery are reduced;

step two, for long-time/high-power instructions, the two energy storage systems cooperatively and jointly output power

For a long-time/high-power instruction, the super-capacitor energy storage system is used for outputting to bear the peak power requirement at the initial stage of the instruction preferentially, and when the super-capacitor energy storage system outputs power independently and cannot meet the instruction requirement, the lithium battery energy storage system is used for outputting power in a matched manner, so that the lithium battery energy storage charging and discharging multiplying power can be reduced, the impact of charging and discharging on the lithium ion battery during the peak output period is reduced, the operation safety of the system is improved, and the service life of the lithium ion battery is prolonged;

step three, improving the adjustment precision index of the super capacitor energy storage system

And the super capacitor energy storage system is called to charge and discharge rapidly to make up, so that the adjustment precision index of the frequency modulation of the unit is improved.

According to the statistics of the distribution of AGC frequency modulation commands of a power plant for one month, the commands with the duration less than 2MW is less than 60 seconds, and the commands with the duration less than 4MW is less than 30 seconds account for about 25 percent of the total commands. These super capacitor systems, which are commanded to 4MW/120MWs, can respond independently to meet frequency modulation requirements. The part of the instructions with the depth less than 4MW but the duration exceeding the super capacitor energy storage capacity range can be completely responded by matching the super capacitor energy storage with the unit, and the instructions account for about 20 percent of the whole. The super capacitor can completely respond to the instruction, and the output force of the unit can completely reach the instruction set point value within the support time of the super capacitor; the sum of the instruction quantity of complete response of the super capacitor energy storage and the unit is about 45%. Therefore, the 4MW/120MWs super-capacitor energy storage subsystem configured by the system can meet approximately half of instruction response requirements, and the lithium battery energy storage system does not need to be put into use. From the AGC command depth profile, the duty cycle of less than 9MW is approximately 79%, and the duty cycle of 9MW-11MW is 12%. With the small proportion of the instructions, the contribution rate to the compensation benefit exceeds 40% due to the long frequency modulation range.

Further, in the embodiment of the invention, when the thermal power generating unit enters an AGC frequency modulation steady operation stage, the super capacitor energy storage system compensates the deviation between the actual output of the unit and the target output of the AGC by frequent charging or discharging, so that the power of the hybrid energy storage combined frequency modulation grid-connected side is rapidly converged to the AGC set point power, the precise control of the combined output is realized, and the value of the adjusting precision is improved.

Furthermore, in the embodiment of the invention, the energy storage system main control unit and the energy storage system sub-control unit are installed in the centralized control container, and an upper computer is placed in the power plant main control room, so that important running state signals of the energy storage system can be uploaded, and monitoring by operators is facilitated.

Further, in the embodiment of the present invention, the data communication between the energy storage system main control unit and the unit DCS control system is implemented by a communication/hard-wiring manner, and the energy storage system main control unit is connected with the sub-control units by a field bus, the controller, the communication card, the IO card, the control power supply, and the like of the energy storage system main control unit are integrally installed in the centralized control container control cabinet, and the energy storage system main control unit obtains operating data such as a frequency modulation command and unit output through a communication interface/hard-wiring manner with the power plant DCS system, receives a DCS switching operation command, and uploads an energy storage system status signal at the same time, and the energy storage system main control unit determines an energy storage system output command through algorithm calculation according to the received operating data such as the frequency modulation command and the unit output, and sends the energy storage system output command to the energy storage system sub-control unit, and, and issuing signals such as switching instructions of the energy storage system.

Further, in the embodiment of the present invention, the energy storage system control subunit is located in each medium voltage variable flow container, receives the instruction of the main control unit, and actually controls the operation and output of the energy storage system.

The working principle is as follows: when the super capacitor and lithium ion battery combined energy storage system is used for carrying out thermal power frequency modulation, the overall operation strategy of hybrid energy storage is that when the hybrid energy storage system receives an AGC (automatic gain control) set point instruction, the hybrid energy storage of the super capacitor and the lithium ion battery immediately starts discharging (charging) response, before the unit output is not followed, the hybrid energy storage system supports the unit output with rated power, the super capacitor energy storage exits after the super capacitor energy storage completely releases (or is full of) the stored electricity in the period, when the unit enters a stable operation stage, the lithium ion battery energy storage exits, the super capacitor starts rapid charging (discharging), and the deviation between the unit output and the AGC set point instruction is corrected until the instruction is finished.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.