CN107482661B - Converter and flow battery energy storage system - Google Patents
Converter and flow battery energy storage system Download PDFInfo
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- CN107482661B CN107482661B CN201710800985.XA CN201710800985A CN107482661B CN 107482661 B CN107482661 B CN 107482661B CN 201710800985 A CN201710800985 A CN 201710800985A CN 107482661 B CN107482661 B CN 107482661B
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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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- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/10—Flexible AC transmission systems [FACTS]
Abstract
The invention discloses a converter and a flow battery energy storage system. The device is applied to a flow battery energy storage system and comprises: the power supply comprises a main switch, a voltage transformation unit, one or more power units and a main controller; the input end of the main switch is used for connecting an alternating current end, the output end of the main switch is connected with the first end of the voltage transformation unit, and the control end of the main switch is connected with the main controller; the second end of the transformation unit comprises one or more interfaces, and the interfaces are connected with the alternating current end of a power unit; the direct current end of the power unit is used for being connected with a flow battery pile; the voltage transformation unit is used for performing high-voltage and low-voltage transformation; and the control end of the power unit is connected with the control end of the main controller, and alternating current-direct current conversion is carried out according to a control command sent by the main controller. The technical scheme can realize the simultaneous connection with a plurality of flow battery galvanic piles to carry out unified energy conversion.
Description
Technical Field
The invention relates to the technical field of energy storage, in particular to a converter and a flow battery energy storage system.
Background
In recent years, battery energy storage technology has been developed rapidly, and energy storage systems using various types of batteries as energy storage media are also increasingly put into operation in power systems and power users, so that the battery energy storage system plays a very positive role in improving the stability, the power supply reliability and the like of the power systems. Among them, dry batteries represented by lithium batteries have the advantages of convenient use, convenient maintenance and the like, and flow batteries represented by vanadium batteries have the advantages of large energy, high energy efficiency, easy site selection and the like. From the recent development trend, dry batteries are more widely used, and particularly, dry batteries are more advantageous in the fields of electric vehicles, mobile energy storage and the like, so that supporting devices such as a converter device, a battery management system and the like in an energy storage system are often designed according to the characteristics of the dry batteries. However, the application value of the flow battery in a high-capacity, even ultra-high-capacity energy storage power station level should not be ignored.
Disclosure of Invention
In view of the above problems, the present invention has been developed to provide a converter device and a flow battery energy storage system that overcome or at least partially solve the above problems.
According to one aspect of the invention, a current transformation device is provided, which is applied to a flow battery energy storage system, and comprises: the power supply comprises a main switch, a voltage transformation unit, one or more power units and a main controller;
the input end of the main switch is used for connecting an alternating current end, the output end of the main switch is connected with the first end of the voltage transformation unit, and the control end of the main switch is connected with the main controller;
the second end of the transformation unit comprises one or more interfaces, and the interfaces are connected with the alternating current end of a power unit;
the direct current end of the power unit is used for being connected with a flow battery pile;
the voltage transformation unit is used for performing high-voltage and low-voltage transformation;
and the control end of the power unit is connected with the control end of the main controller, and alternating current-direct current conversion is carried out according to a control command sent by the main controller.
Optionally, the apparatus further comprises:
the pre-charging unit comprises an auxiliary switch and a starting resistor which are connected in series, wherein the input end of the auxiliary switch is used for being connected with the alternating current end, the control end of the auxiliary switch is connected with the main controller, one end of the starting resistor is connected with the output end of the auxiliary switch, and the other end of the starting resistor is connected with the first end of the voltage transformation unit;
the main controller is used for controlling the main switch to be switched off and the auxiliary switch to be switched on after the converter device is connected to the alternating current end, and pre-charging the power unit; and after the power unit is precharged, controlling the auxiliary switch to be switched off and controlling the main switch to be switched on.
Optionally, the transformation unit includes one or more single-phase transformers, primary sides of the one or more single-phase transformers are first ends of the transformation unit, and the number of the single-phase transformers is the same as the number of current phases at the ac end;
the number of the secondary windings of one single-phase transformer is one or more, and each secondary winding is connected with the first end of one power unit through an interface of the second end of the transformation unit; when the number of the secondary windings of one single-phase transformer is multiple, the multiple secondary windings are mutually independent.
Optionally, the apparatus further comprises: the primary side of the alternating voltage sensor is used for being connected with the alternating current end;
the main controller is also used for connecting a control console, receiving the total active power and the total reactive power sent by the control console, determining the unit active power and the unit reactive power of each power unit according to the total active power and the total reactive power, and sending the unit active power and the unit reactive power as control instructions to each power unit;
the power unit includes: the circuit comprises an H-bridge circuit, a filter circuit and a unit controller;
the alternating current end of the H-bridge circuit is connected with an interface of the second end of the voltage transformation unit, the direct current end of the H-bridge circuit is connected with the first end of the filter circuit, and the second end of the L C filter circuit is used for being connected with a flow battery pile;
the control end of the unit controller is connected with the control end of the main controller, and the unit control end of the unit controller is connected with the control end of the H-bridge circuit;
the unit controller is also connected with the secondary side of the alternating voltage sensor and used for collecting the voltage U of the alternating current endsAccording to UsThe above-mentionedTransformation ratio K of AC voltage sensortThe transformation ratio K of the transformation unitpCalculating the voltage U of the interface at the second end of the voltage transformation unitcell；
The unit controller is also used for collecting the voltage at the direct current side of the H-bridge circuit and calculating the voltage U at the direct current side of the power unit according to the voltage at the direct current side of the H-bridge circuitdc(ii) a And for according to Ucell、UdcAnd the control instruction sent by the main controller generates a Pulse Width Modulation (PWM) signal for the H-bridge circuit, and sends the PWM signal to the H-bridge circuit.
Optionally, the power unit further comprises: an AC contactor, a DC contactor, a unit AC current sensor;
the alternating current contactor is connected with the alternating current end of the H-bridge circuit, so that the alternating current end of the H-bridge circuit is connected with an interface of the second end of the voltage transformation unit through the alternating current contactor, and the control end of the alternating current contactor is connected with the unit controller;
the direct current contactor is connected with the second end of the filter circuit, so that the second end of the filter circuit is connected with the flow battery pile through the direct current contactor, and the control end of the direct current contactor is connected with the unit controller;
the main controller is further used for issuing a command for controlling the closing of the alternating-current contactor and the direct-current contactor in each power unit after the main switch is closed;
the primary side of the unit alternating current sensor is connected with the alternating current contactor in series, and the secondary side of the unit alternating current sensor is connected with the unit controller and used for collecting alternating current side current of the power unit;
the unit controller is further used for judging whether the power unit where the unit controller is located has a fault according to the working state of the H-bridge circuit and the alternating-current side current value of the power unit, and uploading fault information in the power unit where the unit controller is located to the main controller when the power unit has the fault;
the main controller is also used for connecting the flow battery management system and acquiring the working state of each flow battery cell stack; when fault information sent by the unit controller is received and/or a fault state of the flow battery pile is obtained, a redundancy instruction is issued to the corresponding power unit, so that the unit controller controls an H-bridge circuit to stop working and controls the alternating current contactor and the direct current contactor to be disconnected according to the redundancy instruction; and adjusting the control commands sent to the other power cells.
Optionally, the apparatus further comprises:
the primary side of the output current sensor is connected with the first end of the voltage transformation unit, and the secondary side of the output current sensor is connected with the secondary side of the main controller;
the main controller is used for collecting the output current I of the first end of the voltage transformation unitout；
The main controller is also connected with the secondary side of the alternating voltage sensor and used for collecting the voltage U of the alternating current ends(ii) a And for according to UsAnd IoutAnd calculating the output power of the converter device, and adjusting the control instruction sent to each power unit according to the output power and the total active power and the total reactive power sent by the console.
Optionally, the main controller is further configured to connect to a flow battery management system, and obtain a state of charge SOC of each flow battery cell stack;
calculating the energy difference degree of each flow battery cell stack according to the SOC of each flow battery cell stack, and adjusting a control instruction sent to a corresponding power unit according to the energy difference degree when the energy difference degree of one flow battery cell stack exceeds an adjustment threshold value;
and when the energy difference degree of the flow battery pile does not exceed the adjusting threshold value any more, the control command sent to the corresponding power unit is not adjusted any more.
Optionally, when there are multiple current phases at the ac end, the energy difference degree of each flow cell stack in the flow cell stack set is calculated according to the flow cell stack set corresponding to each phase.
According to another aspect of the invention, a flow battery energy storage system is provided, which comprises an alternating current end, a plurality of flow battery stacks and a current transformation device as described in any one of the above.
Optionally, the system further comprises: a console and a flow battery management system;
the flow battery management system is respectively connected with each flow battery cell stack and the converter device and is used for acquiring the working state and SOC of each flow battery cell stack;
the control console is respectively connected with the flow battery management system and the converter device and is used for acquiring the working state of the alternating current end, the working state of the flow battery pile and the SOC; and calculating the total active power and the total reactive power of the converter device according to the working state of the alternating current end, the working state of the flow battery pile and the SOC, and sending the total active power and the total reactive power to the converter device.
According to the current transformation device suitable for the flow battery energy storage system, the characteristics of the flow battery pile can be matched, the current transformation is completed by the power unit arranged corresponding to the flow battery pile, the high-low voltage transformation is realized through the voltage transformation unit, and the control of the current transformation device is realized through the main switch and the main controller. The technical scheme can realize the simultaneous connection with a plurality of flow battery galvanic piles to carry out unified energy conversion.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1 shows a schematic structural view of a deflector according to an embodiment of the invention;
fig. 2 shows a schematic circuit diagram of an inverter according to an embodiment of the invention;
fig. 3 is a schematic diagram of a circuit configuration of a power unit in a converter device according to an embodiment of the invention;
fig. 4 shows a schematic structural diagram of a flow battery energy storage system according to an embodiment of the invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Fig. 1 shows a schematic structural diagram of a current transformer device according to an embodiment of the present invention, which can be applied to a flow battery energy storage system. As shown in fig. 1, the variable flow device 100 includes: a main switch 110, a voltage transformation unit 120, one or more power units 130, a main controller 140.
The input end of the main switch 110 is used for connecting an alternating current end, the output end of the main switch is connected with the first end of the voltage transformation unit 120, and the control end of the main switch 110 is connected with the main controller 140; the second terminal of the transforming unit 120 includes one or more interfaces, which are connected to the ac terminal of a power unit 130; the dc end of the power unit 130 is used to connect to a flow cell stack; the voltage transformation unit 120 is used for performing high-voltage and low-voltage transformation; the control end of the power unit 130 is connected to the control end of the main controller 140, and performs ac/dc conversion according to a control command sent by the main controller 140.
Therefore, the device shown in fig. 1 can be matched with the characteristics of the flow cell stack, current transformation is completed by the power unit arranged corresponding to the flow cell stack, high-low voltage transformation is realized by the transformation unit, and control over the current transformation device is realized by the main switch and the main controller. The technical scheme can realize the simultaneous connection with a plurality of flow battery galvanic piles to carry out unified energy conversion.
In an embodiment of the present invention, the apparatus further includes: a precharge unit 150 including an auxiliary switch 151 and a start resistor 152 (not shown in fig. 1) connected in series, an input terminal of the auxiliary switch 151 being connected to the ac terminal, a control terminal of the auxiliary switch 151 being connected to the main controller 140, one end of the start resistor 152 being connected to an output terminal of the auxiliary switch 151, and the other end being connected to a first terminal of the transforming unit 120; the main controller 140 is configured to, after the converter device 100 is connected to the ac terminal, control the main switch 110 to be turned off, control the auxiliary switch 151 to be turned on, and precharge the power unit 130; and after the pre-charging of the power unit 130 is completed, controlling the auxiliary switch 151 to be opened and the main switch 110 to be closed. The main controller 140, the main switch 110, and the auxiliary switch 151 may be connected by cables.
The function of the pre-charging unit is to divide the voltage through the starting resistor 152, pre-charge the power device in the power unit first, and avoid the power device from being damaged due to overlarge voltage when the power device is directly connected to the alternating current terminal.
In an embodiment of the present invention, in the above apparatus, the transforming unit 120 includes one or more single-phase transformers 121 (not shown in fig. 1), the primary side of the one or more single-phase transformers 121 is the first end of the transforming unit 120, and the number of single-phase transformers 121 is the same as the number of current phases at the ac end; the number of the secondary windings of one single-phase transformer 121 is one or more, and each secondary winding is respectively connected with the first end of one power unit 130 through an interface at the second end of the transformation unit; when the number of the secondary windings of one single-phase transformer 121 is multiple, the multiple secondary windings are independent of each other and can be divided into multiple levels, which is convenient for control. Each power cell connected thereto is thus also divided into a plurality of levels. In order to connect more flow battery stacks, a single-phase multi-winding transformer can be selected.
Taking the example where the ac terminals are three-phase ac power grids, the number of the single-phase transformers 121 is three, and the three transformers correspond to A, B, C three phases respectively. If there are N secondary windings of each single-phase transformer 121, that is, divided into N stages, the power units 130 connected thereto may be respectively denoted as a1 and a2 … … AN, and these power units 130 are connected to the secondary windings of the single-phase transformers 121 corresponding to the a phase through interfaces; similarly, the power units 130B 1 and B2 … … BN are interfaced with the secondary winding of the single-phase transformer 121 corresponding to the B phase, and the power units 130C 1 and C2 … … CN are interfaced with the secondary winding of the single-phase transformer 121 corresponding to the C phase, wherein a1, B1 and C1, a2, B2 and C2 … … AN, BN and CN are of the same order as each other.
In an embodiment of the present invention, the apparatus further includes: an ac voltage sensor 160 (not shown in fig. 1), wherein the primary side of the ac voltage sensor 160 is used for connecting an ac terminal; the main controller 140 is further configured to connect to a console, receive the total active power and the total reactive power sent by the console, determine the unit active power and the unit reactive power of each power unit 130 according to the total active power and the total reactive power, and send the unit active power and the unit reactive power as control instructions to each power unit 130;
the power unit 130 includes: the circuit structure of the H-bridge circuit 131, the filter circuit 132, and the unit controller 133, and the power unit 130 can be seen in fig. 3.
The alternating current end of the H-bridge circuit 131 is connected to the interface of the second end of the voltage transformation unit 120, the direct current end of the H-bridge circuit is connected to the first end of the filter circuit 132, and the second end of the filter circuit 132 is used for being connected to a flow battery stack; the control end of the cell controller 133 is connected to the control end of the main controller 140 (generally, the control end is far away and can be connected through an optical fiber), and the cell control end of the cell controller 133 is connected to the control end of the H-bridge circuit 131 (through a cable); the unit controller 133 is also connected to the secondary side of the ac voltage sensor 160 (via a cable) for collecting the voltage U at the ac sidesAccording to UsTransformation ratio K of AC voltage sensortTransformation ratio K of transformation unitpCalculates the voltage U of the interface at the second terminal of the transformer unit 120cell(ii) a The unit controller 133 is also used to collect the voltage on the dc side of the H-bridge circuit 131 according to the dc side of the H-bridge circuit 131Voltage of (d) calculating the voltage U on the dc side of the power unit 130dc(ii) a And for according to Ucell、UdcAnd a control command transmitted from the main controller 140, generates a pulse width modulation PWM signal for the H-bridge circuit 131, and transmits the PWM signal to the H-bridge circuit 131.
The H-bridge circuit is a fully-controlled power device, such as an IGBT (Insulated Gate bipolar transistor), and the filter circuit may be a filter circuit of two or more stages, such as L C or L C L, and an example of the filter circuit of L C is given in fig. 3.
In an embodiment of the present invention, in the above apparatus, the power unit 130 further includes: ac contactor 134, dc contactor 135, unit ac current sensor 136; the ac contactor 134 is connected to the ac terminal of the H-bridge circuit 131, so that the ac terminal of the H-bridge circuit 131 is connected to the interface with the second terminal of the transformer unit 120 through the ac contactor 134, and the control terminal of the ac contactor 134 is connected to the unit controller 133; the dc contactor 135 is connected to the second end of the filter circuit 132, so that the second end of the filter circuit 132 is connected to the flow cell stack through the dc contactor 135, and the control end of the dc contactor 135 is connected to the unit controller 133;
the main controller 140 is further configured to issue an instruction for controlling the ac contactor and the dc contactor 135 in each power unit to be closed after the main switch is closed.
The primary side of the unit alternating current sensor 136 is connected in series with the alternating current contactor 134, and the secondary side of the unit alternating current sensor 136 is connected with the unit controller 133 and used for collecting the alternating current side current of the power unit 130;
the unit controller 133 is further configured to determine whether the power unit 130 in which the unit controller 133 is located has a fault according to the working state of the H-bridge circuit 131 and the ac-side current value of the power unit 1230, and upload fault information in the power unit 130 to the main controller 140 when the fault occurs; the main controller 140 is further configured to connect to a flow battery management system, and obtain a working state of each flow battery cell stack; when fault information sent by the unit controller 133 is received and/or a fault state of the flow battery cell stack is acquired, a redundancy instruction is issued to the corresponding power unit, so that the unit controller 133 controls the H-bridge circuit 131 to stop working and controls the ac contactor 134 and the dc contactor 135 to be disconnected according to the redundancy instruction; and adjusting control commands sent to other power units 130. The other power unit is a power unit which is not failed and the corresponding flow battery pile is not failed.
In an embodiment of the present invention, the apparatus further includes: an output current sensor 170 (not shown in fig. 1), a primary side of the output current sensor 170 being connected to the first end of the transformer unit 120, a secondary side of the output current sensor 170 being connected (via a cable) to a secondary side of the main controller 140; the main controller 140 is used for collecting the output current I of the first end of the transformer unit 120out(ii) a The main controller 140 is also connected to the secondary side of the ac voltage sensor 170 (via a cable) for collecting the voltage U at the ac sides(ii) a And for according to UsAnd IoutThe output power of the converter device 100 is calculated, and the control command sent to each power unit 130 is adjusted according to the output power and the total active power and the total reactive power sent by the console.
In an embodiment of the present invention, in the above apparatus, the main controller 140 is further configured to connect to a flow cell management system, and obtain a state of charge SOC of each flow cell stack; calculating the energy difference degree of each flow battery cell stack according to the SOC of each flow battery cell stack, and adjusting a control instruction sent to a corresponding power unit according to the energy difference degree when the energy difference degree of one flow battery cell stack exceeds an adjustment threshold; and when the energy difference degree of the flow battery pile does not exceed the adjusting threshold value any more, the control command sent to the corresponding power unit is not adjusted any more. When a plurality of current phases exist at the alternating current end, calculating the energy difference degree of each flow battery electric pile in the flow battery electric pile set according to the flow battery electric pile set corresponding to each phase.
In the above embodiments, the control command should not exceed the limit allowed by the power devices in the power unit.
Fig. 2 is a schematic diagram illustrating a circuit configuration of a current transformer apparatus according to an embodiment of the present invention, and as shown in fig. 2, the current transformer apparatus includes a main switch 110, a transforming unit 120 (including three single-phase transformers 121, an example of which is a single-phase multi-winding transformer), one or more power units 130, a main controller 140, a pre-charging unit 150 (including an auxiliary switch 151 and a starting resistor 152), an ac voltage sensor 160, and an output current sensor 170. Also shown are an ac terminal 410 and a flow cell stack 420 connected to the inverter.
Fig. 4 shows a schematic structural diagram of a flow battery energy storage system according to an embodiment of the present invention, and as shown in fig. 4, the flow battery energy storage system 400 includes an ac terminal 410, a plurality of flow battery stacks 420, and the inverter device 100 in any of the above embodiments.
In an embodiment of the present invention, the system further includes: a console 430 and a flow battery management system 440; the flow battery management system 440 is respectively connected with each flow battery stack 420 and the converter device 100, and is used for collecting the working state and the SOC of each flow battery stack; the console 430 is respectively connected with the flow battery management system 440, the alternating current terminal 410 and the converter device 100, and is configured to obtain a working state of the alternating current terminal 410, a working state of the flow battery stack 420 and an SOC; and calculating the total active power and the total reactive power of the converter device 100 according to the working state of the alternating current terminal 410, the working state of the flow battery stack 420 and the SOC and sending the total active power and the total reactive power to the converter device 100.
In one embodiment, in combination with fig. 1 to 4, the flow cell energy storage system 400 is connected to a 10kV three-phase ac power grid (i.e., the ac terminal 410), the power limit of the converter is 1200KVA (12 × 100KVA, i.e., the power limit of each power unit is 100KVA), the single-phase transformer 121 is a single-phase multi-winding transformer, and the number of secondary windings is 4, i.e., a 4-stage system is implemented.
First, the main controller 140 of the inverter device 100 first closes the auxiliary switch 151 to keep the main switch 110 open, pre-charges the power unit 130 through the starting resistor 152, closes the main switch 110 after the pre-charging is completed, and opens the auxiliary switch 151; ac contactor 134 and dc contactor 135 within power unit 130 are then closed, completing the connection of the three-phase ac power grid, power unit 130, and flow cell stack 420.
Then, the main controller 140 of the converter device 100 obtains the total active power P and the total reactive power Q currently required by the flow battery energy storage system 400 from the console 430, analyzes and confirms that the power allowed to operate by the flow battery energy storage system is not exceeded, and calculates the active power P required by each power unit 130* cellAnd reactive power P* cellGenerally, the average distribution is performed, and the calculation formula is shown in formula 1 and formula 2:
where N represents the number of secondary windings of a single-phase multi-winding transformer, i.e., the number of stages of each phase of power cells 130, X represents one of the three phases, i.e., A, B, and C, and Y represents one of the power cells 130 of that phase, from 1 to N, e.g., P* cell_A1Represents the active power, Q, of the A-phase first power cell 130* cell_A1Represents the reactive power of the first power cell 130 of phase a; in the present embodiment, it is assumed that P is currently received*＝600kW、Q*Since N is 4, the active power P of each power cell 130 can be calculated from the expressions 1 and 2 at 300kVar*cell _ XY 50kW, reactive power Q*cell_XY＝25kVar。
The main controller sends the calculated active power of 50kW and the calculated reactive power of 25kVar as control commands to the power units 130 at the corresponding positions through optical fibers, and the control commands are received by the unit controller 133.
The unit controller 133 receives P in the control command issued by the main controller 140* cell_XY50kW and Q* cell_XYAfter 25kVar, the AC side voltage U is combinedcellAnd a DC side voltage UdcAccording to the basic principle of the single-phase H-bridge circuit, PWM signals required by the H-bridge are calculated and transmitted to power devices in the H-bridge circuit through cables, and the H-bridge circuit is controlled to output designated active power and reactive power.
The main controller 140 measures the voltage U of the inverter 120 via the ac voltage sensor 160 and the output current sensor 170sAnd IoutAnd calculating whether the deviation exists between the output power and the required power of the whole converter device 120, and dynamically adjusting the control command according to the deviation value, thereby ensuring that the operation condition of the whole converter device 120 meets the requirement.
It can be seen that, in this embodiment, a plurality of independent single-phase voltages are constructed by using a single-phase multi-winding transformer, and the energy conversion of the corresponding flow battery cell stacks is controlled by a plurality of power units, so that distributed control and energy concentration are realized.
The optimal state is that the SOC of each flow battery is the same, and in order to ensure the energy balance, the converter device can start the energy balance control under certain conditions. In this example, it may be set that the condition for the energy balance control to be activated is that the absolute value of the power cell energy difference degree is not more than 0.02 (adjustment threshold).
The main controller 140 reads the state of charge of each flow cell stack from the battery management system 440, and records the state of charge as SOCXYWhere X represents one of the three phases, A, B and C, respectively, and Y represents one of the power cells of that phase, from 1 to N, e.g. SOCA1Representing the state of charge of the corresponding flow battery pile of the first power unit of the A phase by using the formulas 3, 4 and 5Respectively calculating the energy difference degree of each three-phase flow battery pile:
in this example, the flow cell stack SOC that the main controller 140 acquires from the flow cell management system 440 at a certain time is as follows: SOC (State of Charge) \A1＝0.51、SOC_A2＝0.50、SOC_A3＝0.50、SOC_A1When the SOC is 0.49, the SOC values of the B-phase and C-phase flow battery stacks are 0.5.
The degree of imbalance can be calculated according to equation 3A1＝0.02，A2＝0，A3＝0，A4Just at the critical regulation, no over-limit is set to-0.02, so that the energy balance function is not started temporarily, and the power instruction of each A-phase power unit maintains P* cell_XY50kW and Q* cell_XY＝25kVar。
With the continuous operation of the flow battery energy storage system 400, the SOC of the battery cell stack corresponding to each power unit of the phase a may continuously diverge, and at a certain time, the SOC value of the battery cell stack of the phase a obtained by the main controller is as follows: SOC (State of Charge) \A1＝0.52、SOC_A2＝0.50、SOC_A3＝0.50、SOC_A1When the SOC values of the B-phase and C-phase flow battery stacks are 0.49, the imbalance can be calculated according to equation 3A1＝0.04，A2＝0，A3＝0，A4The absolute value of imbalance of the a1 and a4 cell stacks is 0.04, which exceeds the set condition of 0.02, and thus the main controller 140 starts the energy balance control.
And substituting the calculated energy difference degree into a formula 6 or a formula 7, and calculating the active power of each adjusted power unit, wherein the formula 6 is carried in when the energy storage system is in a charging state, and the formula 7 is carried in when the energy storage system is in a discharging state. It can be seen that the active power corresponding to the flow cell stack with higher energy is smaller during charging and larger during discharging, whereas the active power corresponding to the flow cell stack with lower energy is larger during charging and smaller during discharging, so that the energy difference between the flow cell stacks can be effectively reduced after the flow cell stack operates for a period of time under the trend.
In this example, if the current flow battery energy storage system 400 is in a charging state, the charging power command of the a1 power unit is 50 × 1-0.04 — 48kW, the charging power command of the a4 power unit is 50 × 1- (-0.04)) 52kW, the charging power commands of the a2 and A3 power units are 50kW, the sum of the charging commands of the four power units in the a phase is still 48+50+50+52 — 200kW, and is identical to the sum of the charging power commands of the B phase and the C phase, but the charging speed of the a1 power unit is smaller than that of the a4 power unit, and the energy difference between the two power units in the charging process becomes small according to equation 6; if the current flow battery energy storage system 400 is in a discharging state, the discharging power command of the a1 power unit is 50 × (1+0.04) ═ 52kW, the discharging power command of the a4 power unit is 50 × (1+ (-0.04)) = 48kW, the discharging power commands of the a2 and A3 power units are 50kW, the sum of the discharging commands of the four a-phase power units is still 48+50 +52 ═ 200kW, which is identical to the sum of the discharging power commands of the B-phase and the C-phase power units, but the discharging speed of the a1 power unit is greater than that of the a4 power unit, and the energy difference of the two power units in the discharging process is reduced according to equation 7.
After the energy balance control is started, along with the continuous operation of the energy storage system, the energy difference of the flow battery galvanic pile corresponding to each power unit is reduced, and when the difference is smaller than a set value, the energy balance function is automatically quitted, so that the energy of the flow battery galvanic pile is in a relative balance process, absolute balance cannot occur, the reactive power of the unit is not influenced by the energy balance function, and 25kVar is still maintained.
Therefore, the energy balance function provided for the flow battery pile in the embodiment can avoid or reduce the limitation of the 'barrel effect' on the operation range of the flow battery energy storage system.
The unit controller 133 monitors the real-time state of the power unit 130, and uploads the fault information in the power unit 130 to the main controller 140 through an optical fiber, and the main controller 140 further obtains the real-time state of the flow cell stack 420 from the flow cell management system 440 through the communication interface, so as to comprehensively determine whether the power unit 130 fault or the flow cell stack 420 fault exists at present.
For example, at a certain time, the main controller detects that the a1 power unit or the corresponding flow battery cell stack 420 has a fault, that is, a redundancy command is sent to the a1 unit controller and the B1 and C1 unit controllers through optical fibers, the unit controller 133 stops the operation of the H-bridge circuit 131 immediately after receiving the redundancy command, and controls the dc contactor 135 and the ac contactor 134 to change from the closed position to the open position, so that the a1, B1 and C1 power units are quitted from operation together. That is to say, in this embodiment, not only the power unit corresponding to the failed flow cell stack is removed from operation, but also one power unit in another phase is removed, and the number of power units operating in each phase is kept the same, so that the energy of the flow cell stack corresponding to each phase is kept consistent.
The main controller 140 recalculates the control command to each power unit 130 according to the remaining power unit number 12-3 being 9, in combination with the total active power and the total reactive power sent by the console 430, at this time P* cell＝600/9＝66.67kW，Q* cellAnd 300/9, 33.33kVar, the recalculated power command does not exceed the limit value 100KVA allowed by the power unit 130, so that the command is continuously sent to the rest power units, and the operation state of the whole flow battery energy storage system 400 is maintained to be 600kW active and 300kVar idle.
The fault redundancy function can be seen, a power unit with a fault (or a supply quantity unit connected with a fault flow battery stack) can be cut off from the flow battery energy storage system, and the overall reliability and stability of the flow battery energy storage system are improved.
When the flow battery energy storage system 400 needs to stop running and the converter device should exit, the main controller 140 sends out instructions to control the main switch 110 to be disconnected, the auxiliary switch 151 to be disconnected, the unit controller 133 controls the H-bridge circuit 131 of the power unit 130 to stop working, and controls the ac contactor 134 and the dc contactor to be disconnected 135, so that the three-phase ac power grid (i.e., the ac terminal 410), the converter device 100 and the flow battery cell stack 420 are all disconnected.
If the power of the flow battery energy storage system is not changed due to the fact that a higher-voltage-level power grid is required to be connected, only the primary voltage and the transformation ratio of the single-phase multi-winding transformer need to be adjusted; if the flow battery energy storage system needs larger capacity, the power of the transformer and the power unit can be enlarged, or the number of secondary windings and the power unit of the transformer can be increased.
In summary, the technical scheme of the invention can conform to the characteristics of the flow battery stack, current transformation is completed by the power unit arranged corresponding to the flow battery stack, high-low voltage transformation is realized by the voltage transformation unit, and control over the current transformation device is realized by the main switch and the main controller. The technical scheme can realize the simultaneous connection with a plurality of flow battery galvanic piles to carry out unified energy conversion.
While the foregoing is directed to embodiments of the present invention, other modifications and variations of the present invention may be devised by those skilled in the art in light of the above teachings. It should be understood by those skilled in the art that the foregoing detailed description is for the purpose of better explaining the present invention, and the scope of the present invention should be determined by the scope of the appended claims.
Claims (7)
1. A converter device is characterized in that the converter device is applied to a flow battery energy storage system and comprises: the power supply comprises a main switch, a voltage transformation unit, one or more power units and a main controller;
the input end of the main switch is used for connecting an alternating current end, the output end of the main switch is connected with the first end of the voltage transformation unit, and the control end of the main switch is connected with the main controller;
the second end of the transformation unit comprises one or more interfaces, and the interfaces are connected with the alternating current end of a power unit;
the direct current end of the power unit is used for being connected with a flow battery pile;
the voltage transformation unit is used for performing high-voltage and low-voltage transformation;
the control end of the power unit is connected with the control end of the main controller, and alternating current-direct current conversion is carried out according to a control instruction sent by the main controller;
the transformation unit comprises one or more single-phase transformers, the primary sides of the one or more single-phase transformers are the first ends of the transformation unit, and the number of the single-phase transformers is the same as that of the current phases of the alternating current ends;
the single-phase transformer comprises a plurality of mutually independent secondary windings, and each secondary winding is connected with the first end of one power unit through an interface of the second end of the transformation unit; the secondary winding is divided into a plurality of levels;
the device also includes: the primary side of the alternating voltage sensor is used for being connected with the alternating current end;
the main controller is also used for connecting a control console, receiving the total active power and the total reactive power sent by the control console, determining the unit active power and the unit reactive power of each power unit according to the total active power and the total reactive power, and sending the unit active power and the unit reactive power as control instructions to each power unit;
the power unit includes: the circuit comprises an H-bridge circuit, a filter circuit and a unit controller;
the alternating current end of the H-bridge circuit is connected with an interface of the second end of the voltage transformation unit, the direct current end of the H-bridge circuit is connected with the first end of the filter circuit, and the second end of the filter circuit is used for being connected with a flow battery pile;
the control end of the unit controller is connected with the control end of the main controller, and the unit control end of the unit controller is connected with the control end of the H-bridge circuit;
the unit controller is also connected with the secondary side of the alternating voltage sensor and used for collecting the voltage U of the alternating current endsAccording to UsAnd a transformation ratio K of the AC voltage sensortThe transformation ratio K of the transformation unitpCalculating the voltage U of the interface at the second end of the voltage transformation unitcell；
The unit controller is also used for collecting the voltage at the direct current side of the H-bridge circuit and calculating the voltage U at the direct current side of the power unit according to the voltage at the direct current side of the H-bridge circuitdc(ii) a And for according to Ucell、UdcGenerating a Pulse Width Modulation (PWM) signal for the H-bridge circuit by using a control instruction sent by the main controller, and sending the PWM signal to the H-bridge circuit;
the main controller is also used for connecting the flow battery management system and acquiring the SOC of each flow battery cell stack;
calculating the energy difference degree of each flow battery cell stack according to the SOC of each flow battery cell stack, and adjusting a control instruction sent to a corresponding power unit according to the energy difference degree when the energy difference degree of one flow battery cell stack exceeds an adjustment threshold value;
and when the energy difference degree of the flow battery pile does not exceed the adjusting threshold value any more, the control command sent to the corresponding power unit is not adjusted any more.
2. The apparatus of claim 1, further comprising:
the pre-charging unit comprises an auxiliary switch and a starting resistor which are connected in series, wherein the input end of the auxiliary switch is used for being connected with the alternating current end, the control end of the auxiliary switch is connected with the main controller, one end of the starting resistor is connected with the output end of the auxiliary switch, and the other end of the starting resistor is connected with the first end of the voltage transformation unit;
the main controller is used for controlling the main switch to be switched off and the auxiliary switch to be switched on after the converter device is connected to the alternating current end, and pre-charging the power unit; and after the power unit is precharged, controlling the auxiliary switch to be switched off and controlling the main switch to be switched on.
3. The apparatus of claim 1,
the power unit further includes: an AC contactor, a DC contactor, a unit AC current sensor;
the alternating current contactor is connected with the alternating current end of the H-bridge circuit, so that the alternating current end of the H-bridge circuit is connected with an interface of the second end of the voltage transformation unit through the alternating current contactor, and the control end of the alternating current contactor is connected with the unit controller;
the direct current contactor is connected with the second end of the filter circuit, so that the second end of the filter circuit is connected with the flow battery pile through the direct current contactor, and the control end of the direct current contactor is connected with the unit controller;
the main controller is further used for issuing a command for controlling the closing of the alternating-current contactor and the direct-current contactor in each power unit after the main switch is closed;
the primary side of the unit alternating current sensor is connected with the alternating current contactor in series, and the secondary side of the unit alternating current sensor is connected with the unit controller and used for collecting alternating current side current of the power unit;
the unit controller is further used for judging whether the power unit where the unit controller is located has a fault according to the working state of the H-bridge circuit and the alternating-current side current value of the power unit, and uploading fault information in the power unit where the unit controller is located to the main controller when the power unit has the fault;
the main controller is also used for connecting the flow battery management system and acquiring the working state of each flow battery cell stack; when fault information sent by the unit controller is received and/or a fault state of the flow battery pile is obtained, a redundancy instruction is issued to the corresponding power unit, so that the unit controller controls an H-bridge circuit to stop working and controls the alternating current contactor and the direct current contactor to be disconnected according to the redundancy instruction; and adjusting the control commands sent to the other power cells.
4. The apparatus of claim 1, further comprising:
the primary side of the output current sensor is connected with the first end of the voltage transformation unit, and the secondary side of the output current sensor is connected with the secondary side of the main controller;
the main controller is used for collecting the output current I of the first end of the voltage transformation unitout；
The main controller is also connected with the secondary side of the alternating voltage sensor and used for collecting the voltage U of the alternating current ends(ii) a And for according to UsAnd IoutAnd calculating the output power of the converter device, and adjusting the control instruction sent to each power unit according to the output power and the total active power and the total reactive power sent by the console.
5. The apparatus of claim 1,
and when the current phases of the alternating current end are multiple, calculating the energy difference degree of each flow battery electric pile in the flow battery electric pile set according to the flow battery electric pile set corresponding to each phase.
6. A flow battery energy storage system, characterized in that the system comprises an alternating current terminal, a plurality of flow battery stacks and a flow transformation device according to any one of claims 1-5.
7. The system of claim 6, further comprising: a console and a flow battery management system;
the flow battery management system is respectively connected with each flow battery cell stack and the converter device and is used for acquiring the working state and SOC of each flow battery cell stack;
the control console is respectively connected with an alternating current end, the flow battery management system and the converter device and is used for acquiring the working state of the alternating current end, the working state of the flow battery pile and the SOC; and calculating the total active power and the total reactive power of the converter device according to the working state of the alternating current end, the working state of the flow battery pile and the SOC, and sending the total active power and the total reactive power to the converter device.
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| CN112769242B (en) * | 2020-12-30 | 2022-12-06 | 漳州科华技术有限责任公司 | Energy storage system starting method, device, equipment and system |
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