CN116316768B - Net-structured distributed energy storage system - Google Patents
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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Abstract
The present disclosure provides a grid-structured distributed energy storage system, which relates to the technical field of energy storage, and the system comprises: the system comprises a battery module, a net-structured power conversion module, an integrated energy storage management module and a medium-voltage transformer; the battery module comprises a battery and a battery management unit, wherein the battery management unit is used for collecting operation data of the battery; the integrated energy storage management module is used for issuing preset operation parameters; the grid-structured power conversion module comprises a sub-power conversion unit which is used for converting battery direct current into three-phase alternating current, collecting electric data, presetting operation parameters so as to generate control signals, and adjusting corresponding battery output currents based on the control signals. Through setting up the sub-power conversion unit with battery one-to-one, can prevent that the cluster from bringing by the battery cluster inconsistency from the inter-cluster voltage uneven, automatically regulated each battery cluster power distribution can also make full use of the flexibility of decentralized energy storage under the condition of initiative support electric wire netting, realizes battery energy storage and utilizes the maximize.
Description
Technical Field
The disclosure relates to the field of energy storage technologies, and in particular relates to a grid-structured distributed energy storage system.
Background
In high proportion renewable energy scenarios, the need for energy flexibility has grown substantially. The electrochemical energy storage serving as a high-quality flexible resource can solve the problems of randomness and volatility brought by new energy installation, ensure the stability of a power grid, reliable power supply and safe operation, and can greatly improve the peak regulation, frequency modulation and voltage regulation capacity of a power system. The net-structured energy storage system with the frequency adjusting and voltage controlling capabilities of the synchronous generator or similar synchronous generator is added near the new energy source, so that the adjusting capability and flexibility of the power system can be comprehensively improved. The method has the outstanding characteristics of stabilizing the power generation fluctuation of the new energy, improving the inertia, voltage and frequency supporting capacity of the system, controlling the short-circuit capacity, improving the damping characteristic of the power grid and the like, and can effectively reconcile various contradictions in the development process of the new energy technically.
Currently, the control strategy of the grid-built energy storage system mainly comprises droop control for simulating the droop characteristics of active power-frequency and reactive power-voltage of the synchronous generator operation and virtual synchronous generator control for simulating the mechanical movement of the generator. But the droop control only simulates the speed regulation and the excitation external characteristics of the synchronous generator system, and the moment of inertia is hard to characterize, so that the frequency stability is poor. The whole process is controlled by a steady state value, so that the transient process of the synchronous machine cannot be embodied, and the dispatching speed is not fast. Currently, the network-structured energy storage technology is mostly applied to a centralized energy storage architecture.
Disclosure of Invention
The present disclosure aims to solve, at least to some extent, one of the technical problems in the related art.
To this end, it is an object of the present disclosure to propose a grid-structured decentralized energy storage system.
To achieve the above object, embodiments of a first aspect of the present disclosure provide a grid-structured distributed energy storage system, including: the system comprises a battery module, a net-structured power conversion module, an integrated energy storage management module and a medium-voltage transformer; the integrated energy storage management module is connected with the battery module and the network-structured power conversion module respectively; the battery module comprises n batteries connected in series and n corresponding battery management units, wherein n is an integer greater than 1, and the battery management units are used for collecting operation data of the batteries; the integrated energy storage management module is used for carrying out numerical calculation, performance analysis, alarm processing and record storage on the operation data uploaded by the battery management unit and issuing preset operation parameters; the grid-structured power conversion module comprises n sub-power conversion units which are in one-to-one correspondence with the batteries, wherein the sub-power conversion units are used for converting direct current input into the batteries or output by the batteries into three-phase alternating current, collecting electric data of the alternating current side of the grid-structured power conversion module, receiving preset operation parameters sent by the integrated energy storage management module, generating control signals, and adjusting output currents of the corresponding batteries based on the control signals.
According to one embodiment of the disclosure, the sub-power conversion unit comprises an energy storage converter and a converter controller, wherein a direct current end of the energy storage converter is connected with a battery corresponding to the sub-power conversion unit, an alternating current end of the energy storage converter is connected with the power grid through a medium voltage transformer, and a control end of the energy storage converter is connected with the converter controller; the converter controller is used for collecting electric data at the grid-connected point and receiving preset operation parameters sent by the integrated energy storage management module, generating adjustment parameters based on the electric data, the preset operation parameters and the operation data, and generating control signals based on the adjustment parameters, wherein the grid-connected point is a collection point of alternating-current ends of all the energy storage converters; the energy storage converter is used for adjusting the operation parameters based on the control signals so as to adjust the operation parameters of the energy storage converter to the adjustment parameters.
According to one embodiment of the present disclosure, the preset operation parameters include preset power, preset reactive power, and the generating the adjustment parameters based on the electrical data, the preset operation parameters, and the operation data includes: performing primary frequency modulation and primary voltage regulation respectively based on the electric data to obtain a target frequency difference and a target voltage difference respectively; determining an adjusted active power based on the target frequency difference and the preset active power, and determining an adjusted reactive power based on the target voltage difference and the preset reactive power; and calculating the regulated active power and the regulated reactive power to obtain a reference three-phase voltage, a reference equivalent electromagnetic torque and a reference reactive power, and taking the reference three-phase voltage, the reference equivalent electromagnetic torque and the reference reactive power as the adjustment parameters.
According to one embodiment of the disclosure, the preset operation parameters further include a preset frequency, primary frequency modulation is performed based on the electrical data, and the obtaining the target frequency difference includes: acquiring acquisition frequency in the electric data, and determining a frequency difference based on the acquisition frequency and the preset frequency; comparing the frequency difference with a first judging range; determining that the target frequency difference is 0 in response to the frequency difference being within the first determination range; and determining the target frequency difference as the frequency difference in response to the frequency difference not being within the first judgment range.
According to one embodiment of the disclosure, the preset operation parameters further include a preset voltage, and performing voltage regulation once based on the electrical data to obtain the target voltage difference includes: acquiring acquisition voltage in the electric data, and determining a voltage difference based on the acquisition voltage and a preset voltage; comparing the voltage difference with a second judging range; determining that the target voltage difference is 0 in response to the voltage difference being within the second determination range; and determining the target voltage difference as the voltage difference in response to the voltage difference not being within the second judgment range.
According to one embodiment of the present disclosure, the determining the adjusted active power based on the target frequency difference and the preset active power, and the determining the adjusted reactive power based on the target voltage difference and the preset reactive power, comprises: acquiring a first sagging coefficient and a second sagging coefficient; determining a biased active power based on the target frequency difference and the first droop coefficient, and determining a biased reactive power based on the target voltage difference and the second droop coefficient; summing the deviation active power and the preset active power to obtain the regulated active power, and summing the deviation reactive power and the preset reactive power to obtain the regulated reactive power.
According to one embodiment of the present disclosure, the preset operation parameters further include a reference voltage change rate, a reference frequency change rate, an active power change rate, and a reactive power change rate, the acquiring the first droop coefficient and the second droop coefficient includes: dividing the active power change rate by the reference frequency change rate to obtain the first droop coefficient, and dividing the reactive power change rate by the reference voltage change rate to obtain the second droop coefficient.
According to one embodiment of the present disclosure, before calculating the regulated active power and the regulated reactive power, it comprises: determining an equivalent torque reference value based on the regulated active power and the preset frequency; determining a torque difference based on the equivalent torque reference value and an equivalent electromagnetic torque calculation value; determining the working frequency of the sub-power conversion unit based on the torque difference, the damping value, the preset frequency and the virtual moment of inertia; and integrating the working frequency to obtain the basic phase of the sub-power conversion unit.
According to one embodiment of the present disclosure, the calculating the regulated active power and the regulated reactive power to obtain a reference three-phase voltage, a reference equivalent electromagnetic torque, and a reference reactive power includes: determining the reference equivalent electromagnetic torque based on the three-phase current vector, the base phase, and the reactive power difference integral value; and determining the reference three-phase voltage based on the operating frequency, the base phase, and the reactive power difference integral value; and determining the reference reactive power based on the operating frequency, the base phase, the three-phase current vector, and the reactive power difference integral value.
According to one embodiment of the present disclosure, obtaining the reactive power difference value integrated value includes: and integrating based on the difference value between the preset reactive power and the regulated reactive power to obtain the reactive power difference value integral value.
Through setting up the sub-power conversion unit with battery one-to-one, can prevent that the cluster from bringing by the battery cluster inconsistency from the inter-cluster voltage uneven, automatically regulated each battery cluster power distribution can also make full use of the flexibility of decentralized energy storage under the condition of initiative support electric wire netting, realizes battery energy storage and utilizes the maximize.
Drawings
FIG. 1 is a schematic diagram of a structured distributed energy storage system according to one embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a sub-power conversion unit according to one embodiment of the present disclosure;
FIG. 3 is a schematic flow diagram of power conversion unit control according to one embodiment of the present disclosure;
fig. 4 is a schematic flow chart of acquiring a first droop coefficient and a second droop coefficient according to an embodiment of the disclosure.
Detailed Description
Embodiments of the present disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and intended for the purpose of explaining the present disclosure and are not to be construed as limiting the present disclosure.
The net-structured energy storage refers to an energy storage technology, and can effectively improve the new energy receiving capacity. The network-structured energy storage technology can relieve the stability problems of transient voltage, frequency and the like of a power system at present. The net construction type energy storage device can effectively improve new energy acceptance, and in the future, the net construction type energy storage device is hopeful to become an important direction of energy storage development and guarantee a large power grid to safely and stably operate a new foundation stone. The control strategy of the network-structured energy storage system in the prior art mainly comprises droop control for simulating the droop characteristics of active power-frequency and reactive power-voltage of the operation of the synchronous generator and virtual synchronous generator control for simulating the mechanical movement of the generator. But the droop control only simulates the speed regulation and the excitation external characteristics of the synchronous generator system, and the moment of inertia is hard to characterize, so that the frequency stability is poor. The whole process is controlled by a steady state value, so that the transient process of the synchronous machine cannot be embodied, and the dispatching speed is not fast. The current grid-structured energy storage technology is mainly applied to a centralized energy storage architecture, and the application of the technology in a distributed energy storage system is still mentioned, but the distributed energy storage technology is a mainstream technical scheme in the field of battery energy storage because the problem of circulation among battery clusters can be solved. Therefore, research and development of the grid-structured distributed energy storage can conform to the development trend of accessing a novel power grid by high-proportion new energy, and fully exert the application advantages of the distributed energy storage technology.
Fig. 1 is a schematic diagram of a grid-structured distributed energy storage system according to the present disclosure, as shown in fig. 1, where the grid-structured distributed energy storage system includes: battery module 110, grid-tied power conversion module 120, integrated energy storage management module 130, and medium voltage transformer 140.
The battery module 110 is connected to the grid-configured power conversion module 120, the grid-configured power conversion module 120 is connected to the power grid through the medium voltage transformer 140, and the integrated energy storage management module 130 is connected to the battery module 110 and the grid-configured power conversion module 120, respectively.
In the embodiment of the disclosure, the battery module 110 includes n batteries 150 connected in series and n corresponding battery management units 160, where n is an integer greater than 1, and the battery management units 160 are configured to collect operation data of the corresponding batteries 150.
Through setting up battery management unit alone to the battery, can realize the individual management to the battery, promote the precision of battery control.
The integrated energy storage management module 130 is configured to perform numerical calculation, performance analysis, alarm processing, record and storage on the operation data uploaded by the battery management unit 160, and simultaneously issue preset operation parameters.
It should be noted that the preset operation parameter is a target value for the transition of the current grid-structured distributed energy storage system. The preset operation parameters may be generated based on manual expected input, or may be generated by an integrated energy storage management module based on the current operation state of the grid-structured distributed energy storage system, which is not limited herein.
In one possible implementation of the present disclosure, the BATTERY management unit 160 may be a BATTERY management system (BATTERY MANAGEMENT SYSTEM, BMS), and the BMS can monitor the state of the BATTERY 150 in real time, enhance the use efficiency of the BATTERY 150, prevent the occurrence of overcharge and overdischarge of the BATTERY 150, and improve the service life of the BATTERY 150, in addition to collecting the operation data of the BATTERY 150.
The grid-structured power conversion module comprises n sub-power conversion units 170 which are in one-to-one correspondence with the batteries 150, wherein the sub-power conversion units 170 are used for inputting the batteries 150 or converting direct currents output by the batteries 150 into three-phase alternating currents, and collecting electric data of an alternating current side of the grid-structured power conversion module and preset operation parameters sent by the integrated energy storage management module.
By arranging the sub-power conversion units 170 corresponding to the batteries 150 one by one, the inter-cluster voltage unevenness caused by the inconsistency of the battery clusters can be prevented, the power distribution of each battery cluster can be automatically adjusted, the flexibility of distributed energy storage can be fully utilized, and the energy storage utilization maximization of the batteries 150 can be realized.
It should be noted that the electrical data may include various information, and is not limited in any way, for example, the electrical data may include voltage data, frequency data, current data, and the like, and may be specifically limited according to actual design requirements.
The sub-power conversion unit 170 is further configured to generate a control signal based on the electrical data and the operation data, and adjust the output current of the corresponding battery 150 based on the control signal.
In the embodiment of the present disclosure, as shown in fig. 2, the sub-power conversion unit 170 includes: an energy storage converter 210, and a converter controller 220.
The dc end of the energy storage converter 210 is connected to the battery 150 corresponding to the sub-power conversion unit 170, the ac end of the energy storage converter 210 is connected to the power grid through the medium voltage transformer 140, and the control end of the energy storage converter 210 is connected to the converter controller 220.
The energy storage converter 210 (Power Conversion System, PCS) can control the charging and discharging processes of the storage battery to perform ac-dc conversion, and can directly supply power to the ac load under the condition of no power grid. The PCS is composed of a DC/AC bidirectional converter, a control unit and the like.
The integrated energy storage management module 130 is configured to obtain a state of the power grid, a state of the battery management system 160, and a state of the energy storage converter 210, and control the energy storage converter 210 to operate in a grid-connected mode or an off-grid mode according to the state of the power grid and the state of the energy storage converter 210.
Particularly, when the power grid is electrified and the integrated energy storage management module 130 reads that the energy storage converter 210 is in a standby state, a starting instruction and a power setting instruction are sequentially sent to the energy storage converter 210 so as to control the energy storage converter 210 to operate in a grid-connected mode; or,
when the power grid is powered down, the integrated energy storage management module 130 sends an off-grid mode instruction and a power setting instruction to the energy storage converter 210 when receiving a power-down alarm signal sent by the energy storage converter 210 so as to control the energy storage converter 210 to operate in an off-grid mode; or,
in the case of a power grid restoration call, the energy storage converter 210 stops outputting when the scram switch is detected to be closed, and the integrated energy storage management module 130 controls the energy storage converter 210 to be turned off and then turned on again when the power grid restoration call is detected.
In one embodiment of the present disclosure, the converter controller 220 is configured to collect electrical data at a grid-connected point and receive a preset operation parameter sent by the integrated energy storage management module, generate an adjustment parameter based on the electrical data, the preset operation parameter and the operation data, and generate a control signal based on the adjustment parameter, where the grid-connected point is a collection point of ac ends of all the energy storage converters 210.
In the disclosed embodiment, the converter controller 220 may be provided with a pulse width modulation (Pulse Width Modulation, PWM) module for generating a control signal to implement pulse width modulation.
In the embodiment of the disclosure, as shown in fig. 2, the electrical data required by the converter controller may be obtained by sampling through a grid-tie point and by a phase-locked loop.
The converter controller 220 may also be used for three-level voltage current control, midpoint voltage control, active damping control, repetitive control, and the like.
The energy storage converter 210 is configured to adjust an operation parameter based on the control signal, so as to adjust the operation parameter of the energy storage converter 210 to the adjustment parameter.
It should be noted that the energy storage converter 210 may include a plurality of adjustment modules, and the operation parameters of the plurality of adjustment modules may be adjusted based on the adjustment parameters in the control signal, so as to adjust the operation parameters of the energy storage converter 210 to the frequency and the power in the adjustment parameters.
In the above embodiment, the preset operation parameters include preset power and preset reactive power, and the adjustment parameters are generated based on the electrical data, the preset operation parameters and the operation data, which may be further explained by fig. 3, and the method includes:
s301, primary frequency modulation and primary voltage modulation are respectively carried out based on the electric data so as to respectively acquire a target frequency difference and a target voltage difference.
In the embodiment of the disclosure, the preset operation parameters further include a preset frequency, primary frequency modulation is performed based on the electric data, the acquisition frequency of the electric data can be firstly acquired by acquiring the target frequency difference, the frequency difference is determined based on the acquisition frequency and the preset frequency, then the frequency difference is compared with a first judgment range, the target frequency difference is determined to be 0 in response to the frequency difference being located in the first judgment range, and the target frequency difference is determined to be the frequency difference in response to the frequency difference not being located in the first judgment range.
In the embodiment of the present disclosure, the first determination range is set in advance, and may be changed according to actual design requirements, which is not limited in any way. In implementation, the first determination range is generally set to 0.033-0.1 hz.
In the embodiment of the disclosure, the frequency difference after one voltage adjustment can be determined by the following formula:
wherein,,for a preset frequency->For the acquisition frequency +.>For the frequency difference +.>Is the first judgment range.
In an embodiment of the disclosure, the preset operation parameter further includes a preset voltage, the voltage is adjusted once based on the electrical data, the acquired voltage difference in the electrical data may be acquired first, the voltage difference is determined based on the acquired voltage and the preset voltage, then the voltage difference is compared with a second judgment range, the target voltage difference is determined to be 0 in response to the voltage difference being located in the second judgment range, and the target voltage difference is determined to be the voltage difference in response to the voltage difference not being located in the second judgment range.
In the embodiment of the present disclosure, the second determination range is set in advance, and may be changed according to actual design requirements, which is not limited in any way. In an implementation, this second determination range is typically set to 0.5% of rated power.
Wherein,,for a preset voltage, < >>For voltage acquisition, < >>For the second judgment range, ++>Is the voltage difference.
The preset frequency, the preset active power, the preset reactive power and the preset voltage are the frequency, the reactive power, the active power and the voltage which are finally changed after the three-phase cross-flow adjustment is expected.
S302, determining to adjust the active power based on the target frequency difference and the preset active power, and determining to adjust the reactive power based on the target voltage difference and the preset reactive power.
It should be noted that, in the example of the present disclosure, the adjusted reactive power may be obtained by first obtaining the first droop coefficient and the second droop coefficient, then determining the deviation active power based on the target frequency difference and the first droop coefficient, and determining the deviation reactive power based on the target voltage difference and the second droop coefficient, and finally summing the deviation active power and the preset active power to obtain the adjusted active power, and summing the deviation reactive power and the preset reactive power to obtain the adjusted reactive power.
In the disclosed embodiments, the regulated active power and the regulated reactive power may be calculated by the following formulas:
wherein,,to regulate active power, +.>For the target frequency difference +.>For the first sagging coefficient, +>Is the preset active power.
Wherein,,for the preset reactive power, < >>For the second droop factor,/->For the target voltage difference, < >>To regulate reactive power.
S303, calculating the regulated active power and the regulated reactive power to obtain a reference three-phase voltage, a reference equivalent electromagnetic torque and a reference reactive power, and taking the reference three-phase voltage, the reference equivalent electromagnetic torque and the reference reactive power as regulating parameters.
In an embodiment of the present disclosure, the reference equivalent electromagnetic torque is determined based on the three-phase current vector, the base phase, the reactive power difference integral, and the reference three-phase voltage is determined based on the operating frequency, the base phase, the reactive power difference integral, and the reference reactive power is determined based on the operating frequency, the base phase, the three-phase current vector, and the reactive power difference integral.
The three-phase current vector is a vector representing current properties such as current frequency and magnitude, and is obtained by sampling the system.
In the disclosed embodiment, the reference three-phase voltage, the reference equivalent electromagnetic torque, and the reference reactive power may be obtained by the following formulas:
wherein,,for reference of equivalent electromagnetic torque +.>For reactive power difference integral value>Basic phase->For the operating frequency of the network-built power conversion module, < >>For reference three-phase voltage>For reference reactive power +.>Is a three-phase current vector.
The operating frequency of the grid-formation power conversion module is set in advance, and may be changed according to actual design requirements, and is not limited in any way.
In the middle ofIt can be expressed as that,
in the middle ofIt can be expressed as that,
in the middle ofIt can be expressed as that,
。
in the middle ofExpressed as->。
In the middle ofExpressed as->。
In the embodiment of the disclosure, first, primary frequency modulation and primary voltage regulation are respectively performed based on electric data to obtain a target frequency difference and a target voltage difference respectively, then, based on the target frequency difference and a preset active power, an adjustment active power is determined, and based on the target voltage difference and the preset reactive power, an adjustment reactive power is determined, and finally, the adjustment active power and the adjustment reactive power are calculated to obtain a reference three-phase voltage, a reference equivalent electromagnetic torque and a reference reactive power, and the reference three-phase voltage, the reference equivalent electromagnetic torque and the reference reactive power are used as adjustment parameters. The speed regulation and the excitation external characteristics of the synchronous generator system are simulated through primary frequency modulation and primary voltage regulation, so that the accuracy and the robustness of finally obtained adjustment parameters can be improved.
In the embodiment of the present disclosure, integration may be performed based on a difference value between the preset reactive power and the adjusted reactive power to obtain a reactive power difference value integrated value.
It should be noted that, before calculating the adjusted active power and the adjusted reactive power, the equivalent torque reference value is determined based on the adjusted active power and the preset frequency, then the torque difference is determined based on the equivalent torque reference value and the equivalent electromagnetic torque calculation value, then the working frequency of the sub-power conversion unit 170 is determined based on the torque difference, the damping value, the preset frequency and the virtual moment of inertia, and finally the working frequency is integrated to obtain the basic phase of the sub-power conversion unit 170.
In the above embodiment, the first droop coefficient and the second droop coefficient are obtained, which may be further explained by fig. 4, and the method includes:
s401, acquiring a reference voltage change rate, a reference frequency change rate, an active power change rate and a reactive power change rate.
After the reference voltage change rate, the reference frequency change rate, the active power change rate and the reactive power change rate are adjusted, the change rate of the data between the system steady state and the last steady state is set in advance.
S402, dividing the active power change rate and the reference frequency change rate to obtain a first droop coefficient, and dividing the reactive power change rate and the reference voltage change rate to obtain a second droop coefficient.
In the disclosed embodiment, the first droop coefficient and the second droop coefficient may be calculated by the following formulas.
Wherein,,for the active power rate of change, +.>For the rate of change of frequency>For the reactive power rate of change +.>Is the rate of change of voltage.
For example, when the rate of change of the energy storage system frequencyEqual to 0.5%, active rate of change +.>Equal to 25%, the power-frequency droop coefficient is set>50.
In the embodiment of the disclosure, the reference voltage change rate, the reference frequency change rate, the active power change rate, and the reactive power change rate are first obtained, then the active power change rate and the reference frequency change rate are divided to obtain a first droop coefficient, and the reactive power change rate and the reference voltage change rate are divided to obtain a second droop coefficient. By setting the reference voltage change rate, the reference frequency change rate, the active power change rate and the reactive power change rate in advance, the change trend of the control network type distributed energy storage system can be realized based on expected change and the change rate, and the practicability of the control network type distributed energy storage system is improved.
The main parameters of the control of the grid-structured distributed energy storage system comprise active-frequency droop coefficients of each PCS module unitReactive-voltage sag factor->Virtual moment of inertia->Virtual damping coefficient->Virtual excitation coefficient->。
After the first sagging coefficient and the second sagging coefficient are obtained, parameters and operation states of each battery 150 may be different, so that the sagging coefficient needs to be separately determined according to the operation state corresponding to each battery 150 to realize targeted regulation and control.
Active-frequency droop coefficients for each unit moduleThe method is set according to the following formula:
in the formula, the SOC is the charge state of the battery cluster connected with the current PCS,is the average charge state of each battery cluster of the whole distributed energy storage system put into operation, and is +.>Is the first sag factor of the i-th cell.
Reactive-voltage sag factorAnd (5) adjusting the SOC in real time according to the distributed management battery cluster. Preliminary reactive-voltage sag factor +.>According to the voltage change rate of the energy storage system>And reactive change rate->Design is carried out
For example, when the rate of change of the energy storage system voltageEqual to 3%, reactive change rate->Equal to 30%, the reactive-voltage sag coefficient is initially set +.>10.
Reactive-voltage sag coefficient of each unit moduleThe method is set according to the following formula:
in the formula, the SOC is the charge state of the battery cluster connected with the current PCS,the average charge state of each battery cluster of the whole distributed energy storage system is put into operation. />Is the second sag factor of the ith cell.
In the description of the present disclosure, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present disclosure.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present disclosure, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Although embodiments of the present disclosure have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the present disclosure, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the present disclosure.
Claims (9)
1. A grid-structured distributed energy storage system, comprising: the system comprises a battery module, a net-structured power conversion module, an integrated energy storage management module and a medium-voltage transformer; the integrated energy storage management module is respectively connected with the battery module and the grid-structured power conversion module;
the battery module comprises n batteries connected in series and n corresponding battery management units, wherein n is an integer greater than 1, and the battery management units are used for collecting operation data of the batteries;
the integrated energy storage management module is used for carrying out numerical calculation, performance analysis, alarm processing and record storage on the operation data uploaded by the battery management unit, and simultaneously issuing preset operation parameters, wherein the preset operation parameters comprise preset power and preset reactive power;
the grid-structured power conversion module comprises n sub-power conversion units which are in one-to-one correspondence with the batteries, wherein the sub-power conversion units are used for converting direct current output by the batteries into three-phase alternating current, collecting electric data of an alternating current side of the grid-structured power conversion module, receiving preset operation parameters sent by the integrated energy storage management module to generate control signals, and adjusting output currents of the corresponding batteries based on the control signals, the sub-power conversion units comprise a converter controller, the converter controller is used for collecting electric data at a grid-connected point and receiving preset operation parameters sent by the integrated energy storage management module, performing primary frequency modulation and primary voltage modulation respectively based on the electric data to obtain a target frequency difference and a target voltage difference respectively, determining an adjustment active power based on the target frequency difference and the preset active power, determining an adjustment reactive power based on the target voltage difference and the preset reactive power, calculating the adjustment active power and the adjustment reactive power to obtain a reference three-phase voltage, a reference equivalent electromagnetic torque and a reference reactive power, and generating the reference three-phase voltage, the reference equivalent electromagnetic torque and the reactive power as the reference electromagnetic torque and the reference reactive power adjusting parameters.
2. The system of claim 1, wherein the grid connection point is a collection point of alternating current ends of all energy storage converters, the sub-power conversion unit further comprises an energy storage converter, a direct current end of the energy storage converter is connected with a battery corresponding to the sub-power conversion unit, the alternating current end of the energy storage converter is connected with the power grid through a medium voltage transformer, and a control end of the energy storage converter is connected with the converter controller;
the energy storage converter is used for adjusting the operation parameters based on the control signals so as to adjust the operation parameters of the energy storage converter to the adjustment parameters.
3. The system of claim 2, wherein the predetermined operating parameters further comprise a predetermined frequency, primary frequency modulation based on the electrical data, the obtaining the target frequency difference comprising:
acquiring acquisition frequency in the electric data, and determining a frequency difference based on the acquisition frequency and the preset frequency;
comparing the frequency difference with a first judging range;
determining that the target frequency difference is 0 in response to the frequency difference being within the first determination range;
and determining the target frequency difference as the frequency difference in response to the frequency difference not being within the first judgment range.
4. The system of claim 1, wherein the predetermined operating parameters further comprise a predetermined voltage, wherein the obtaining the target voltage difference comprises performing a voltage adjustment based on the electrical data, comprising:
acquiring acquisition voltage in the electric data, and determining a voltage difference based on the acquisition voltage and a preset voltage;
comparing the voltage difference with a second judging range;
determining that the target voltage difference is 0 in response to the voltage difference being within the second determination range;
and determining the target voltage difference as the voltage difference in response to the voltage difference not being within the second judgment range.
5. The system of claim 4, wherein the determining to adjust the active power based on the target frequency difference and the preset active power, and the determining to adjust the reactive power based on the target voltage difference and the preset reactive power comprises:
acquiring a first sagging coefficient and a second sagging coefficient;
determining a biased active power based on the target frequency difference and the first droop coefficient, and determining a biased reactive power based on the target voltage difference and the second droop coefficient;
summing the deviation active power and the preset active power to obtain the regulated active power, and summing the deviation reactive power and the preset reactive power to obtain the regulated reactive power.
6. The system of claim 5, wherein the predetermined operating parameters further comprise a reference voltage rate of change, a reference frequency rate of change, an active power rate of change, and a reactive power rate of change, the obtaining the first droop coefficient and the second droop coefficient comprising:
dividing the active power change rate by the reference frequency change rate to obtain the first droop coefficient, and dividing the reactive power change rate by the reference voltage change rate to obtain the second droop coefficient.
7. The system of claim 1, wherein prior to calculating the regulated active power and the regulated reactive power, comprising:
determining an equivalent torque reference value based on the regulated active power and a preset frequency;
determining a torque difference based on the equivalent torque reference value and an equivalent electromagnetic torque calculation value;
determining the working frequency of the sub-power conversion unit based on the torque difference, the damping value, the preset frequency and the virtual moment of inertia;
and integrating the working frequency to obtain the basic phase of the sub-power conversion unit.
8. The system of claim 7, wherein said calculating said regulated active power and said regulated reactive power to obtain a reference three-phase voltage, a reference equivalent electromagnetic torque, and a reference reactive power comprises:
determining the reference equivalent electromagnetic torque based on the three-phase current vector, the base phase, and the reactive power difference integral value; the method comprises the steps of,
determining the reference three-phase voltage based on the operating frequency, the base phase, and the reactive power difference integral value; the method comprises the steps of,
the reference reactive power is determined based on the operating frequency, the base phase, the three-phase current vector, and the reactive power difference integral value.
9. The system of claim 8, wherein obtaining the reactive power difference integral value comprises:
and integrating based on the difference value between the preset reactive power and the regulated reactive power to obtain the reactive power difference value integral value.
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