CN112952878A - Multi-direct-current coupling system and control method thereof - Google Patents
Multi-direct-current coupling system and control method thereof Download PDFInfo
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention provides a multi-direct current coupling system and a control method thereof.A scheduling power is equally divided according to the number of on-line direct current coupling systems and is respectively used as initial given power to be sent to each direct current coupling system after an external scheduling instruction is received so as to control each direct current coupling system to operate according to the initial given power; then determining the power regulating quantity of each direct current coupling system according to a preset balancing strategy and sending the power regulating quantity to each direct current coupling system, and further controlling each direct current coupling system to operate according to the superposition result of the initial given power and the power regulating quantity corresponding to each direct current coupling system; that is, the output of each direct current coupling system is adjusted according to the power adjustment obtained by the preset equalization strategy, so that the equalization of each battery system is realized, and the problems of large battery state deviation and inconsistent service life in the multiple direct current coupling systems are solved.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a multi-direct-current coupling system and a control method thereof.
Background
In the prior art, an optical storage dc coupling system is a widely used optical storage system, a photovoltaic array inside the optical storage dc coupling system can be directly connected to a dc bus of an inverter, and a battery system is generally connected to the dc bus through a bidirectional DCDC converter; the electric energy on the direct current bus can be from a photovoltaic array or from the reverse transformation of the inverter after receiving the power of the power grid; the electric energy on the direct current bus can be connected to the grid through an inverter, and can also be stored in a battery system through the bidirectional DCDC converter.
When a plurality of direct current coupling systems are connected in parallel, the above modes are generally adopted to independently control each system, and the storage battery part is relatively independently controlled, that is, cooperative scheduling of power among the plurality of direct current coupling systems and balanced control of batteries are not realized.
Disclosure of Invention
In view of this, embodiments of the present invention provide a multi-dc coupling system and a control method thereof, which can achieve state balance of each battery system, and solve the problems of large battery state deviation and inconsistent service life in the multi-dc coupling system.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
the invention provides a control method of a multi-direct current coupling system, wherein alternating current measurement of each direct current coupling system is connected in parallel, and the control method comprises the following steps:
receiving a power scheduling instruction issued by an external scheduling instruction; wherein the power scheduling instruction comprises: scheduling power;
according to the number of the on-line direct current coupling systems, uniformly dividing the scheduling power and respectively sending the scheduling power as initial given power to each direct current coupling system so as to control each direct current coupling system to operate according to the initial given power;
and determining the power regulating quantity of each direct current coupling system according to a preset balancing strategy and sending the power regulating quantity to each direct current coupling system so as to control each direct current coupling system to operate according to the superposition result of the initial given power and the power regulating quantity corresponding to each direct current coupling system.
Preferably, the determining the power adjustment amount of each dc-coupled system according to a preset equalization strategy and sending the power adjustment amount to each dc-coupled system includes:
determining the power regulation direction and the power regulation basic quantity according to the balance reference quantity of each direct current coupling system;
determining the power regulating quantity corresponding to each direct current coupling system according to the battery running state of each direct current coupling system, the balance reference quantity and the power regulating basic quantity;
and respectively transmitting the power regulating quantity to the corresponding direct current coupling systems.
Preferably, the determining the power adjustment direction according to the balance reference of each dc-coupled system includes:
respectively judging whether the balance reference quantity of each direct current coupling system is larger than the corresponding average value of each balance reference quantity;
if the judgment result is yes, determining that the power regulation direction of the corresponding direct current coupling system is increased;
and if the judgment result is negative, determining that the power regulation direction of the corresponding direct current coupling system is reduced.
Preferably, the determining the power adjustment basic quantity according to the balance reference quantity of each dc-coupled system includes:
and respectively determining the power regulation basic quantity by adopting a preset control mode according to the difference value between the balance reference quantity of each direct current coupling system and the corresponding average value of each balance reference quantity.
Preferably, the preset control mode is as follows: any one of a proportional control mode, an integral control mode, a proportional integral control mode, or a proportional integral derivative control mode.
Preferably, determining the power adjustment amount corresponding to each dc-coupled system according to the battery operating state of each dc-coupled system, the balance reference amount, and the power adjustment basic amount includes:
for the direct-current coupling system with the balance reference quantity smaller than the corresponding average value of each balance reference quantity, if the battery running state is charging, determining the power regulation quantity as the power regulation basic quantity in the corresponding power regulation direction; if the battery running state is discharging, determining that the power adjustment quantity is k times of the power adjustment basic quantity in the corresponding power adjustment direction;
for the direct-current coupling system with the balance reference quantity larger than the corresponding average value of each balance reference quantity, if the battery running state is discharging, determining the power regulation quantity as the power regulation basic quantity in the corresponding power regulation direction; and if the battery running state is charging, determining that the power adjustment quantity is k times of the power adjustment basic quantity in the corresponding power adjustment direction.
Preferably, k is 2.
Preferably, the equalization reference is: at least one of battery state of charge, battery health, or direct current voltage.
Preferably, the sum of the power adjustment amounts of the dc-coupled systems is zero, so as to ensure that the total output port power of the multiple dc-coupled systems is the scheduled power.
Preferably, before the step of equally dividing the scheduled power and transmitting each of the dc-coupled systems as the initial given power, the method further includes:
judging whether the multi-direct current coupling system operates in a limited transmission state or not;
if the judgment result is yes, the step of equally dividing the scheduling power and respectively sending the scheduling power as initial given power to each direct current coupling system is executed;
and if the judgment result is negative, controlling each direct current coupling system to operate according to the maximum power.
Preferably, the determining whether the multi-dc coupling system operates in a limited transmission state includes:
judging whether the scheduling power is smaller than the maximum power of each online direct current coupling system;
if the judgment result is yes, judging that the multi-direct current coupling system operates in a limited sending state;
and if the judgment result is negative, judging that the multi-direct current coupling system operates in an unlimited state.
A second aspect of the present invention provides a multiple dc coupling system, including: an energy management system EMS and a plurality of direct current coupling systems; wherein:
the alternating current of each direct current coupling system is connected to a power grid in parallel;
the EMS is in communication connection with a main controller in each dc coupling system, and is configured to execute the control method of the multiple dc coupling system as described in any one of the above embodiments.
Preferably, each of the dc coupling systems includes: the system comprises a battery system, a DCDC converter, a photovoltaic array, an inverter and the main controller; wherein:
the battery system is connected with one side of the DCDC converter;
the other side of the DCDC converter, the output end of the photovoltaic array and the direct current side of the inverter are connected to a direct current bus of the direct current coupling system;
the AC side of the inverter is used as the AC side of the DC coupling system;
the main controller is in communication connection with the DCDC converter and the inverter and is used for controlling the running state of the direct current coupling system.
Preferably, after each of the dc-coupled systems receives the power adjustment amount:
if the superposition result of the initial given power and the power regulating quantity is larger than the power upper limit, the inverter operates at the power upper limit;
when the battery system of the motor allows charging, if the superposition result is between the upper power limit and the lower power limit, the inverter of the motor operates according to the superposition result; if the superposition result is less than or equal to the lower power limit, the inverter operates at the lower power limit;
when the battery system of the motor is not allowed to be charged, if the superposition result is between the upper power limit and zero, the inverter of the motor operates according to the superposition result; and if the superposition result is less than or equal to zero, the inverter operates at zero power.
Preferably, the main controller is a controller provided independently, or is integrated in a controller of the DCDC converter or the inverter.
Preferably, the inverter is a DCAC power electronics device.
Based on the control method for the multiple dc-coupled systems provided by the embodiment of the present invention, after receiving an external scheduling instruction, the scheduling power is divided equally according to the number of the on-line dc-coupled systems and is respectively sent to each dc-coupled system as an initial given power, so as to control each dc-coupled system to operate according to the initial given power; then determining the power regulating quantity of each direct current coupling system according to a preset balancing strategy and sending the power regulating quantity to each direct current coupling system so as to control each direct current coupling system to operate according to the superposition result of the initial given power and the power regulating quantity corresponding to each direct current coupling system; that is, the output of each direct current coupling system is adjusted according to the power adjustment obtained by the preset equalization strategy, so that the equalization of each battery system is realized, and the problems of large battery state deviation and inconsistent service life in the multiple direct current coupling systems are solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a flowchart of a control method of a multiple dc coupling system according to an embodiment of the present invention;
fig. 2 is a partial flowchart of another control method for a multiple dc coupling system according to an embodiment of the present invention;
fig. 3 is a partial flowchart of another control method for a multiple dc coupling system according to an embodiment of the present invention;
fig. 4-fig. 7 are four control block diagrams for obtaining basic power adjustment quantities of the dc-coupled systems in the control method for a multiple dc-coupled system according to the embodiment of the present invention;
fig. 8 is a flowchart of a control method of a multiple dc coupling system according to another embodiment of the present invention;
fig. 9 is a schematic structural diagram of a multiple dc coupling system according to another embodiment 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.
In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The embodiment of the invention provides a control method of a multi-direct-current coupling system, which can realize the state balance of each battery system and solve the problems of large state deviation and inconsistent service life of batteries in the multi-direct-current coupling system.
The control method is applied to an EMS (Energy Management System) of a multi-dc coupling System, and a flow chart of the control method is shown in fig. 1, and includes:
s101, receiving a power scheduling instruction issued by an external scheduling instruction.
In practical application, the EMS performs scheduling control on the whole multi-dc-coupled system according to a power scheduling instruction in an external scheduling instruction received by the EMS, where the power scheduling instruction mainly includes scheduling power of the multi-dc-coupled system.
And S102, according to the number of the on-line direct current coupling systems, uniformly dividing the scheduling power and respectively sending the scheduling power as initial given power to each direct current coupling system so as to control each direct current coupling system to operate according to the initial given power.
After receiving the scheduling power issued by the external scheduling instruction, the EMS detects each dc-coupled system to determine the number of the on-line dc-coupled systems, and it should be noted that the method for determining the number of the on-line dc-coupled systems by the EMS may be the same as that in the prior art, and is not described herein again, and is within the protection scope of the embodiments of the present invention.
Then the EMS equally divides the received scheduling power according to the number of the on-line dc coupling systems, and sends the power value obtained after the average division as the initial given power P0 to each dc coupling system, so as to control each dc coupling system to operate according to the initial given power P0 through the main controller of each dc coupling system, and then step S103 is executed.
S103, determining the power regulating quantity of each direct current coupling system according to a preset balancing strategy and sending the power regulating quantity to each direct current coupling system so as to control each direct current coupling system to operate according to the superposition result of the initial given power and the power regulating quantity corresponding to each direct current coupling system.
It should be noted that the output of the battery systems in the dc-coupled systems are different, and therefore, after the dc-coupled systems operate according to the above initial given power P0, the state of each battery system may be biased; in this case, it is necessary to perform adjustment according to the actual capacity of each battery system to achieve the balance of each battery system. The power adjustment quantity P1 of each dc-coupled system determined according to the preset equalization strategy includes both the power adjustment direction and the specific magnitude of power adjustment. Regarding the power adjustment direction, in practical application, it may be set as: the power adjustment direction is increasing when P1 is positive and decreasing when P1 is negative.
Specifically, the power adjustment amount of each dc-coupled system can be obtained by the following method, as shown in fig. 2, including:
s201, determining the power regulation direction and the power regulation basic quantity according to the balance reference quantity of each direct current coupling system.
It should be noted that the equalization reference may be: the present invention provides an embodiment of a method for controlling a battery system, which includes at least one of SOC (state of charge), SOH (state of health, i.e., percentage of current capacity and factory capacity of a battery) or dc voltage, where the embodiment of the present invention describes the SOC of the battery system in each dc-coupled system by taking the balance reference as a real-time measurement, and the SOC of each battery system may be sent to the EMS by a main controller of each dc-coupled system; the equalization reference amount may be the SOH or the dc voltage, and so on, and will not be described again.
At this time, as shown in fig. 3, the step S201 of determining the power adjustment direction according to the balance reference of each dc-coupled system may be divided into the following steps:
s301, respectively judging whether the balance reference quantity of each direct current coupling system is larger than the corresponding average value of each balance reference quantity.
Taking the SOC of each battery system as a balance reference, calculating the average state of charge (SOC _ avg) of the multi-DC coupling system as a corresponding average value of the balance reference according to each SOC; if the determination result is yes, i.e. when the SOC > SOC _ avg, go to step S302; if the determination result is negative, that is, if the SOC is less than SOC _ avg, step S303 is executed.
And S302, determining that the power adjusting direction of the corresponding direct current coupling system is increased.
And S303, determining the power regulation direction of the corresponding direct current coupling system to be reduced.
The process of determining the power adjustment basic quantity according to the balance reference quantity of each dc-coupled system in step S201 is as follows: and respectively determining the basic power regulation quantity by adopting a preset control mode according to the difference value between the balance reference quantity of each direct current coupling system and the corresponding average value of each balance reference quantity.
It should be noted that the preset control mode may be: any one of a proportional control mode, an integral control mode, a proportional integral control mode, or a proportional integral derivative control mode. Control strategy diagrams of each control mode are respectively shown in fig. 4-7, taking proportional control as an example, and as shown in fig. 4, the specific control process is as follows: after proportional control is carried out by taking the difference value delta SOC between the SOC and the SOC _ avg as input, corresponding power regulation basic quantity delta P is output through amplitude limiting control regulation; the processes of other control modes are similar to this, and are not described again one by one, and are within the protection scope of the embodiment of the present invention.
S202, determining power regulating quantity corresponding to each direct current coupling system according to the battery running state, the balance reference quantity and the power regulating basic quantity of each direct current coupling system.
The battery operation state comprises two types: the charging operation state and the discharging operation state, and as can be seen from the above steps S301 to S303, there are two cases of the equalization reference amount of each battery system.
The process of determining the power adjustment amount corresponding to each dc coupling system according to the battery operating state, the balance reference amount, and the power adjustment basic amount of each dc coupling system through combination of various conditions can be roughly divided into the following four processes:
for a dc-coupled system in which the equalization reference is less than the corresponding average of each equalization reference:
(1) if the battery running state is charging, and the illumination intensity is considered to be good at this time, the power adjustment amount P1 is determined as the power adjustment basic amount Δ P in the corresponding power adjustment direction, that is, P1 ═ Δ P.
(2) If the battery is in a discharging state and the light intensity is weak, the power regulation quantity P1 is determined to be the power regulation basic quantity delta P which is k times of the corresponding power regulation direction, namely P1-k.
For a dc-coupled system in which the equalization reference is greater than the corresponding average of each equalization reference:
(3) if the battery running state is discharging, and the illumination intensity is weak at the moment, determining the power adjustment quantity P1 as a power adjustment basic quantity delta P in the corresponding power adjustment direction, namely P1 equals delta P;
(4) if the battery is in a charging state and the illumination intensity is stronger at the time, determining that the power regulation quantity P1 is a power regulation basic quantity delta P which is k times of the corresponding power regulation direction, namely P1 is k x delta P.
It should be noted that the k times are set for the purpose of distinguishing and adjusting the speed according to the illumination intensity and the current charge-discharge state, and accelerating the balancing speed; under the same SOC deviation, all the power regulation basic quantities delta P are the same; and under different SOC deviations, obtaining the corresponding power regulation basic quantity delta P according to the respective control modes. The specific value of k may be determined by the skilled person according to the practical application, for example, k is 2, but is not limited thereto and is within the scope of the embodiments of the present invention.
And S203, respectively issuing each power regulating quantity to each corresponding direct current coupling system.
And further controlling the direct current coupling systems to operate according to the superposition result (P0+ P1) of the initial given power and the power regulating quantity corresponding to each direct current coupling system.
In the control method of the multiple dc-coupled systems provided in this embodiment, after receiving an external scheduling instruction, first, according to the number of the on-line dc-coupled systems, the scheduling power is equally divided and respectively sent to each dc-coupled system as initial given power, so as to control each dc-coupled system to operate according to the initial given power; then determining the power regulating quantity P1 of each direct current coupling system according to a preset balancing strategy and sending the power regulating quantity P1 to each direct current coupling system so as to control each direct current coupling system to operate according to the superposition result of the initial given power P0 and the power regulating quantity P1 corresponding to each direct current coupling system; that is, the output of each dc coupled system is adjusted by the power adjustment amount P1 obtained according to the preset equalization strategy, so that the equalization of each battery system is realized, and the problems of large battery state deviation and inconsistent service life in the multi-dc coupled system are solved. And moreover, a variable balance given strategy is realized according to the running state of each battery system and the state of the photovoltaic array, so that different power regulating quantities P1 are obtained, and the system balance speed is accelerated.
In practical application, for the control principle of the multi-dc coupling system, the scheduled ac grid-connected point power should be preferentially ensured, i.e. the total output port power of the multi-dc coupling system is the scheduled power; secondly, the energy of the photovoltaic panel is fully utilized, namely the energy of the photovoltaic panel is preferentially utilized to meet the dispatching power, and meanwhile, the redundant electric energy is used for charging the battery; finally, the balance among the battery systems is realized through the control method provided by the embodiment, and the balance comprises the SOC balance, the SOH balance, the direct-current voltage balance and the like of the battery.
Therefore, another embodiment of the present invention further provides a method for controlling multiple dc-coupled systems, based on the above embodiment, in order to implement the balance of each battery system on the premise of meeting the two prior control requirements, when the power adjustment amount of each dc-coupled system is determined according to the preset balance strategy in step S103, it is ensured that the sum of the power adjustment amounts of each dc-coupled system is zero, that is, the sum is zero, that is, the power adjustment amount of each dc-coupled system is zero
Wherein, P1xThe power regulating variable of the x-th dc-coupled system is represented, x is 1, 2. The total output port power of the multi-direct current coupling system is guaranteed to be dispatching power, namely the power of the AC grid-connected point scheduled by the first priority is guaranteed; meanwhile, before the step S102 is executed, the following steps should be further included, as shown in fig. 8, so that the second priority is to ensure that the energy of the photovoltaic panel is fully utilized; specifically, after step S101, the following steps are performed:
s401, judging whether the multi-direct-current coupling system operates in a limited-transmission state.
When the multi-dc coupling system operates in the limited state, that is, it is described that the scheduling power received by the EMS is smaller than the power that can be output by the online inverter, that is, each dc coupling system needs to limit its own output, step S102 may be executed at this time to ensure the balance among the battery systems of the multi-dc coupling system.
If the multiple dc-coupled systems operate in an unlimited state, that is, the scheduling power received by the EMS is greater than or equal to the power that can be output by the online inverter, that is, each dc-coupled system can output with its own maximum power, then step S402 is executed.
Specifically, whether the multiple direct current coupling systems operate in a limited state or not can be determined by judging whether the scheduling power is smaller than the maximum power of each online direct current coupling system or not; if so, judging that the multi-direct-current coupling system operates in a limited-transmission state; and if the judgment result is negative, judging that the multi-direct-current coupling system operates in an unlimited state. It should be noted that there are many ways to determine whether the multi-dc coupling system operates in the transmission-limited state in the prior art, which are not limited to this and are not described herein again.
And S402, controlling each direct current coupling system to operate according to the maximum power.
Therefore, the control method for the multiple dc coupling systems provided in this embodiment can achieve the balance of each battery system without changing the existing requirement for controlling the ac side power and fully utilizing the energy of the photovoltaic panel.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
Another embodiment of the present invention further provides a multi-dc coupling system, a schematic structural diagram of which is shown in fig. 9, including: EMS and a plurality of dc coupling systems 100; wherein:
the ac side of each dc coupling system 100 is connected in parallel to the grid; in practical applications, the ac test of each dc-coupled system 100 may be connected to an ac grid-connected point in parallel, i.e. the total output port of the multi-dc-coupled system, and then the grid-connected point is connected to the power grid through a suitable transformer.
The EMS is communicatively connected to the main controller 101 in each dc-coupled system 100, and is configured to execute the control method of the multi-dc-coupled system 100 according to the above embodiment, so that the ac power at the point of connection, that is, the total output port power of the multi-dc-coupled system, is adjusted to the scheduling power received by the EMS.
In practical applications, as shown in fig. 9, each dc coupling system 100 includes: a battery system, a DCDC converter 102, a photovoltaic array, an inverter, and a master controller 101.
The power traces within the dc-coupled system 100 are shown as solid lines in fig. 9: the battery system is connected with one side of the DCDC converter 102; the other side of the DCDC converter 102, the output end of the photovoltaic array and the dc side of the inverter are all connected to a dc bus (not shown) of the dc coupling system 100; the ac side of the inverter is taken as the ac side of the dc-coupled system 100. The battery system is charged and discharged by the DCDC converter 102.
The communication traces within the dc-coupled system 100 are shown as dashed lines in fig. 9: the main controller 101 is connected to the DCDC converter 102 and the inverter in communication, and is configured to control an operation state of the dc-coupled system 100, and implement reading, controlling, and scheduling of power.
In practical applications, the main controller 101 may be a controller provided independently, or may be integrated into the controller of the DCDC converter 102 or the inverter.
In addition, the inverter may be any DCAC power electronic device, such as an energy storage converter or a photovoltaic inverter with a reverse charging function, and may be specifically a unidirectional power conversion device, preferably a bidirectional power conversion device.
When an external scheduling instruction issues a new instruction to the EMS for the first time, the EMS performs power sharing according to the number of the online subsystems (namely, the direct current coupling system 100) to give an initial operation power (namely, an initial given power P0) to each subsystem, and each subsystem operates according to a first beat power value issued by the EMS; and then the EMS performs balance control according to a preset balance strategy and the battery SOC state and the system average SOC state of each subsystem, and respectively transmits the calculated different P1 to each subsystem, and the subsystems superpose the balance power value P1 on the basis of the given power of the previous beat, wherein the P1 can be a positive value or a negative value.
When the subsystem can meet the scheduled power instruction, the subsystem operates according to the power scheduling instruction; and when the subsystem can not meet the scheduled power instruction, executing according to the maximum output of the system. When the system operates in an unlimited state, namely the power scheduling instruction received by the EMS is more than or equal to the power which can be output by the online inverter, the system operates according to the maximum power, and the SOC balance control is not carried out at the moment; when the system operates in a limited state, namely the power scheduling instruction received by the EMS is smaller than the power which can be output by the on-line inverter, the system operates according to the power scheduling instruction. According to the principle of bus voltage competition, the inside of each subsystem can automatically control the flow direction of the available power Ppv of the photovoltaic array, the operating power Pdc of the DCDC converter 102 and the inverter power Pac only by enabling the control direct-current voltage value of the DCDC converter 102 to be larger than the direct-current voltage value controlled by the inverter, and the system can realize the maximum power operating state of the internal photovoltaic array only by controlling the size of the inverter power Pac.
When the EMS of the multiple dc-coupled system 100 executes the control method of the multiple dc-coupled system 100 provided in the above embodiment, after each dc-coupled system 100 receives the power adjustment amount, if the superposition result (P0+ P1) of the initial given power P0 and the power adjustment amount P1 is greater than the upper power limit Pmax, the inverter thereof operates at the upper power limit Pmax; when the battery system allows charging, if the superposition result (P0+ P1) is between the upper power limit Pmax and the lower power limit-Pmax, the inverter operates with the superposition result (P0+ P1); if the superposition result (P0+ P1) is less than or equal to the lower power limit-Pmax, the inverter operates at the lower power limit-Pmax; when the battery system does not allow charging, if the superposition result (P0+ P1) is between the upper power limit Pmax and zero, the inverter operates with the superposition result (P0+ P1); if the superposition result (P0+ P1) is less than or equal to zero, the inverter operates at zero power. That is, each dc coupling system 100 in the multiple dc coupling systems 100 provided in this embodiment may be provided with its own power amplitude limit, and in practical application, it is determined according to its specific application environment, and all of them are within the protection scope of this application.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (16)
1. A control method of a multi-direct current coupling system is characterized in that alternating current measurement of each direct current coupling system is connected in parallel, and the control method comprises the following steps:
receiving a power scheduling instruction issued by an external scheduling instruction; wherein the power scheduling instruction comprises: scheduling power;
according to the number of the on-line direct current coupling systems, uniformly dividing the scheduling power and respectively sending the scheduling power as initial given power to each direct current coupling system so as to control each direct current coupling system to operate according to the initial given power;
and determining the power regulating quantity of each direct current coupling system according to a preset balancing strategy and sending the power regulating quantity to each direct current coupling system so as to control each direct current coupling system to operate according to the superposition result of the initial given power and the power regulating quantity corresponding to each direct current coupling system.
2. The method for controlling multiple dc-coupled systems according to claim 1, wherein determining the power adjustment amount of each dc-coupled system according to a preset equalization strategy and sending the power adjustment amount to each dc-coupled system comprises:
determining the power regulation direction and the power regulation basic quantity according to the balance reference quantity of each direct current coupling system;
determining the power regulating quantity corresponding to each direct current coupling system according to the battery running state of each direct current coupling system, the balance reference quantity and the power regulating basic quantity;
and respectively transmitting the power regulating quantity to the corresponding direct current coupling systems.
3. The method as claimed in claim 2, wherein the determining the power adjustment direction according to the balance reference of each dc-coupled system comprises:
respectively judging whether the balance reference quantity of each direct current coupling system is larger than the corresponding average value of each balance reference quantity;
if the judgment result is yes, determining that the power regulation direction of the corresponding direct current coupling system is increased;
and if the judgment result is negative, determining that the power regulation direction of the corresponding direct current coupling system is reduced.
4. The method for controlling multiple dc-coupled systems according to claim 2, wherein the determining the power adjustment basic quantity according to the balance reference quantity of each dc-coupled system comprises:
and respectively determining the power regulation basic quantity by adopting a preset control mode according to the difference value between the balance reference quantity of each direct current coupling system and the corresponding average value of each balance reference quantity.
5. The method for controlling a multi-dc coupling system according to claim 4, wherein the preset control mode is: any one of a proportional control mode, an integral control mode, a proportional integral control mode, or a proportional integral derivative control mode.
6. The method for controlling multiple dc-coupled systems according to claim 2, wherein determining the power adjustment amount corresponding to each dc-coupled system according to the battery operating state of each dc-coupled system, the balance reference amount, and the power adjustment basic amount comprises:
for the direct-current coupling system with the balance reference quantity smaller than the corresponding average value of each balance reference quantity, if the battery running state is charging, determining the power regulation quantity as the power regulation basic quantity in the corresponding power regulation direction; if the battery running state is discharging, determining that the power adjustment quantity is k times of the power adjustment basic quantity in the corresponding power adjustment direction;
for the direct-current coupling system with the balance reference quantity larger than the corresponding average value of each balance reference quantity, if the battery running state is discharging, determining the power regulation quantity as the power regulation basic quantity in the corresponding power regulation direction; and if the battery running state is charging, determining that the power adjustment quantity is k times of the power adjustment basic quantity in the corresponding power adjustment direction.
7. The method of claim 6, wherein k is 2.
8. The method for controlling a multiple dc-coupled system according to any one of claims 2 to 7, wherein the balance reference is: at least one of battery state of charge, battery health, or direct current voltage.
9. The method as claimed in any one of claims 1 to 7, wherein the sum of the power adjustment amounts of the dc-coupled systems is zero to ensure that the total output port power of the dc-coupled systems is the scheduled power.
10. The method for controlling multiple dc-coupled systems according to any one of claims 1 to 7, further comprising, before dividing the scheduled power equally and transmitting each of the dc-coupled systems as an initial given power, respectively:
judging whether the multi-direct current coupling system operates in a limited transmission state or not;
if the judgment result is yes, the step of equally dividing the scheduling power and respectively sending the scheduling power as initial given power to each direct current coupling system is executed;
and if the judgment result is negative, controlling each direct current coupling system to operate according to the maximum power.
11. The method of claim 10, wherein determining whether the multiple dc-coupled system is operating in a restricted state comprises:
judging whether the scheduling power is smaller than the maximum power of each online direct current coupling system;
if the judgment result is yes, judging that the multi-direct current coupling system operates in a limited sending state;
and if the judgment result is negative, judging that the multi-direct current coupling system operates in an unlimited state.
12. A multi-dc coupling system, comprising: an energy management system EMS and a plurality of direct current coupling systems; wherein:
the alternating current of each direct current coupling system is connected to a power grid in parallel;
the EMS is communicatively connected to a main controller in each of the dc-coupled systems, and is configured to perform the method for controlling the multiple dc-coupled systems according to any one of claims 1 to 11.
13. The multiple dc coupling system of claim 12, wherein each of said dc coupling systems comprises: the system comprises a battery system, a DCDC converter, a photovoltaic array, an inverter and the main controller; wherein:
the battery system is connected with one side of the DCDC converter;
the other side of the DCDC converter, the output end of the photovoltaic array and the direct current side of the inverter are connected to a direct current bus of the direct current coupling system;
the AC side of the inverter is used as the AC side of the DC coupling system;
the main controller is in communication connection with the DCDC converter and the inverter and is used for controlling the running state of the direct current coupling system.
14. The multiple dc-coupled system of claim 13, wherein each of the dc-coupled systems, after receiving a power adjustment amount:
if the superposition result of the initial given power and the power regulating quantity is larger than the power upper limit, the inverter operates at the power upper limit;
when the battery system of the motor allows charging, if the superposition result is between the upper power limit and the lower power limit, the inverter of the motor operates according to the superposition result; if the superposition result is less than or equal to the lower power limit, the inverter operates at the lower power limit;
when the battery system of the motor is not allowed to be charged, if the superposition result is between the upper power limit and zero, the inverter of the motor operates according to the superposition result; and if the superposition result is less than or equal to zero, the inverter operates at zero power.
15. The multiple dc coupling system of claim 14, wherein the main controller is a stand-alone controller or is integrated into a controller of the DCDC converter or the inverter.
16. The multiple dc-coupled system of claim 14, wherein the inverter is a DCAC power electronics device.
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