WO2024040982A1 - 一种交流直接并网型电池储能***的功率变换方法 - Google Patents

一种交流直接并网型电池储能***的功率变换方法 Download PDF

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Publication number
WO2024040982A1
WO2024040982A1 PCT/CN2023/087517 CN2023087517W WO2024040982A1 WO 2024040982 A1 WO2024040982 A1 WO 2024040982A1 CN 2023087517 W CN2023087517 W CN 2023087517W WO 2024040982 A1 WO2024040982 A1 WO 2024040982A1
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Prior art keywords
energy storage
phase
full
current control
voltage
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PCT/CN2023/087517
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English (en)
French (fr)
Inventor
左文平
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佛山和储能源科技有限公司
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Priority to US18/144,763 priority Critical patent/US11764703B1/en
Publication of WO2024040982A1 publication Critical patent/WO2024040982A1/zh

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Classifications

    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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]

Definitions

  • the invention belongs to the technical field of electric energy storage, and more specifically, relates to a power conversion method of an AC direct grid-connected battery energy storage system.
  • Existing battery energy storage systems usually use assembled technology, which consists of multiple battery cells connected in series and parallel to form a battery module. Multiple battery modules are connected in series to form a battery cluster. Multiple battery clusters are connected in parallel to form a battery stack. The positive and negative DC voltages of the battery stack The bus is connected to the positive and negative DC buses of the power conversion system, and the AC side of the power conversion system is connected to the external AC system to form a grid-connected battery energy storage system.
  • the power conversion system usually uses a two-level or three-level voltage source inverter topology, which is used to realize DC/AC power conversion between the battery stack and the external AC system. It also needs to configure AC filtering. In order to reduce the AC output harmonics of the power conversion system, it will bring problems of high cost and high loss to the grid-connected battery energy storage system.
  • the purpose of the present invention is to provide a power conversion method for an AC direct grid-connected battery energy storage system, which can achieve AC/DC power conversion between the battery energy storage system and the AC system at low cost and low loss.
  • the present invention provides a power conversion method for an AC direct grid-connected battery energy storage system.
  • the AC direct grid-connected battery energy storage system includes several energy storage modules, and each energy storage module includes A, B, and C are three phase units composed of upper bridge arms and/or lower bridge arms.
  • Each bridge arm is composed of multiple fully controlled battery modules connected in series and then connected in series with a reactor;
  • each phase unit when each phase unit only includes an upper bridge arm, the low-voltage end of the upper bridge arm in each phase unit constitutes the AC end of the phase unit.
  • the AC ends of the three phase units correspond to A, B, and C of the external AC system respectively.
  • the three-phase terminals are connected, and the high-voltage terminals of the upper arm of the three phase units in each energy storage module are connected together to form the positive DC bus H+ of the energy storage module; when each phase unit only includes the lower arm, The high-voltage end of the lower arm constitutes the AC end of the phase unit.
  • the AC ends of the three phase units are connected to the A, B, and C three-phase ends of the external AC system.
  • the lower bridge of the three phase units in each energy storage module The low-voltage ends of the arms are commonly connected to form the negative DC bus L- of the energy storage module; when each phase unit 11 includes both an upper bridge arm and a lower bridge arm, the high-voltage ends of all upper bridge arms in each energy storage module are commonly connected to form the The positive DC bus of the energy storage module, the low-voltage ends of all the lower bridge arms in each energy storage module are connected together to form the negative DC bus of the energy storage module, the low-voltage end of the upper bridge arm and the high-voltage end of the lower bridge arm in each phase unit
  • the AC terminals of the three phase units are connected to the three-phase terminals A, B, and C of the external AC system respectively;
  • Each fully controlled battery module includes a full current control battery module and a battery module.
  • the full current control battery module includes an energy transmission control unit and a relay energy unit.
  • the relay energy unit uses an energy storage capacitor, and the energy storage capacitor and the battery module Parallel connection;
  • the energy transmission control unit uses multiple first fully controlled power electronic devices to connect or disconnect the energy storage capacitor from the external AC system;
  • the power conversion method includes the following steps:
  • V ref_Ap V dcn /2-m a ⁇ V dcn /2
  • V ref_An V dcn /2+m a ⁇ V dcn /2
  • V ref_Bp V dcn /2-m b ⁇ V dcn /2
  • V ref_Bn V dcn /2+m b ⁇ V dcn /2
  • V ref_Cp V dcn /2-m c ⁇ V dcn /2
  • V ref_Cn V dcn /2+m c ⁇ V dcn /2
  • V ref_Ap represents the reference voltage of the upper bridge arm in phase A
  • V ref_An represents the reference voltage of the lower bridge arm in phase A
  • V ref_Bp represents the reference voltage of the upper bridge arm in phase B
  • V ref_Bn represents the lower bridge arm in phase B.
  • V ref_Cp represents the reference voltage of the upper bridge arm in phase C
  • V ref_Cn represents the reference voltage of the lower bridge arm in phase C
  • V dcn represents the DC voltage rating of the positive DC bus to the negative DC bus
  • the power conversion method of the AC direct grid-connected battery energy storage system can realize the integration between the battery energy storage system and the AC system by adding a full-current control battery module to each battery module and controlling it accordingly.
  • the power conversion system can be omitted, which greatly reduces the system cost; at the same time, because the power conversion system is omitted, the power conversion system is omitted.
  • the corresponding losses make the provided AC direct grid-connected battery energy storage system have lower losses.
  • step (3) the formula for calculating the number of full-current control battery modules that need to be put into the upper arm and/or lower arm of phases A, B, and C is:
  • N Ap ROUND (V ref_Ap /V cn ) N
  • An ROUND(V ref_An /V cn ) N
  • Bp ROUND(V ref_Bp /V cn ) N
  • Bn ROUND(V ref_Bn /V cn ) N
  • Cp ROUND (V ref_Cp /V cn )
  • Cn ROUND(V ref_Cn /V cn )
  • N Ap represents the number of full-current control battery modules put in the upper arm of phase A
  • N An represents the number of full-current control battery modules put in the lower arm of phase A
  • N Bp represents the number of full-current control battery modules put in the upper arm of phase B.
  • the number of full-current control battery modules N Bn represents the number of full-current control battery modules put in the lower arm of phase B
  • N Cp represents the number of full-current control battery modules put in the upper arm of phase C
  • N Cn represents the number of full-current control battery modules put in the upper arm of phase C
  • the full current input into the bridge arm controls the number of battery modules
  • ROUND represents the rounding function
  • V cn represents the rated voltage value of the energy storage capacitor.
  • step (1) the steps for calculating the AC active current reference value I dref and the AC reactive current reference value I qref are as follows:
  • the AC active current reference value I dref is obtained after proportional and integral adjustment; the actual measured value of reactive power Q pu and the reference value of reactive power Q ref are calculated as After difference comparison, the AC reactive current reference value I qref is obtained after proportional and integral adjustment.
  • the full-current control battery module also includes a current control unit.
  • the current control unit adopts six three-phase full-bridge circuits composed of second fully-controlled power electronic devices. Three-phase circuits in each full-current control battery module are The two input terminals of the full-bridge circuit are connected to the two terminals of the energy storage capacitor in the full-current control battery module. Each phase AC output terminal of the three-phase full-bridge circuit in each full-current control battery module is connected to an inductor respectively.
  • the battery modules are connected;
  • the power conversion method also includes the following steps:
  • the difference is compared with the reference value V Cref of the average capacitance voltage of the energy storage capacitor.
  • the difference obtained after the difference comparison is After the value is adjusted by proportional integral, the discharge current command I ord of each battery module is obtained;
  • each full-current controller After comparing the difference between the discharge current command I ord of each battery module and the current I dis of the inductor in each corresponding full-current control battery module, and after closed-loop control by a proportional-integral controller or a current hysteresis controller, each full-current controller is obtained.
  • the duty cycle signals of the six second fully controlled power electronic devices in the current control battery module correspond to the on/off status of the six second fully controlled power electronic devices in each full current control battery module, thereby controlling each The current of the inductor in the full-current control battery module is controlled in a closed loop to maintain the balance between the active power output by the AC direct grid-connected battery energy storage system to the external AC system and the discharge power of the full-current control battery module.
  • AC terminals of the three phase units in each energy storage module are respectively connected to the A, B, and C three-phase terminals of the external AC system through AC transformers.
  • each phase unit is composed of three bridge arms, and the combination of the three bridge arms includes a combination of three upper bridge arms or a combination of three lower bridge arms.
  • the AC direct grid-connected battery energy storage system also includes a redundant phase unit, the AC end of the redundant phase unit is connected to one end of three single-phase AC circuit breakers, and the three single-phase AC circuit breakers The other end is connected to the three-phase terminals A, B, and C of the external AC system respectively; and the AC terminals of the three phase units in each energy storage module are respectively connected to the three-phase A, B, and C terminals of the external AC system through the AC circuit breaker. end connected.
  • first fully controlled power electronic device and the second fully controlled power electronic device both use one or more transistors and diodes connected in anti-parallel with them; each battery module uses 12 to 24 single cells. formed in series.
  • the energy transmission control unit in the full-current control battery module includes two first fully-controlled power electronic devices, which are fully-controlled power electronic devices Q1 and Q2 respectively.
  • the fully-controlled power electronic device Q1 Low voltage side
  • the high voltage end of the fully controlled power electronic device Q2 is connected to the high voltage end of the fully controlled power electronic device Q1 and one end of the energy storage capacitor is connected to the low voltage end of the fully controlled power electronic device Q2.
  • the other end of the energy storage capacitor is connected.
  • Figure 1 is a module block diagram of an AC direct grid-connected battery energy storage system provided by an embodiment of the present invention
  • FIG. 2 is a module block diagram of an AC direct grid-connected battery energy storage system provided by another embodiment of the present invention.
  • Figure 3 is a schematic diagram of the circuit principle of a bridge arm provided by an embodiment of the present invention.
  • Figure 4 is a module block diagram of a full current control battery module provided by an embodiment of the present invention.
  • Figure 5 is a control principle diagram of the power exchange method of the AC direct grid-connected battery energy storage system provided by an embodiment of the present invention
  • Figure 6 is a control principle diagram of the power exchange method of the AC direct grid-connected battery energy storage system provided by another embodiment of the present invention.
  • Figure 7 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 1 of the present invention.
  • Figure 8 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 2 of the present invention.
  • Figure 9 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 3 of the present invention.
  • Figure 10 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 4 of the present invention.
  • Figure 11 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 5 of the present invention.
  • Figure 12 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 6 of the present invention.
  • Figure 13 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 7 of the present invention.
  • Figure 14 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 8 of the present invention.
  • Figure 15 is the topology structure of the AC direct grid-connected battery energy storage system provided by Embodiment 9 of the present invention.
  • Figure 16 is a topological structure of a full current control battery module provided by an embodiment of the present invention.
  • first and second are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as “first” and “second” may explicitly or implicitly include at least one of these features.
  • plural means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.
  • severeal means at least one, such as one, two, etc., unless otherwise expressly and specifically limited.
  • the present invention eliminates the need for centralized power conversion used to connect the battery energy storage system and the AC system in the traditional grid-connected battery energy storage system.
  • the system provides an AC direct grid-connected battery energy storage system, and realizes the AC/DC power conversion between the AC direct grid-connected battery energy storage system and the AC system through the corresponding power conversion algorithm.
  • FIG 1 is a module block diagram of an AC direct grid-connected battery energy storage system provided by an embodiment of the present invention.
  • the system includes several energy storage modules 10, and each energy storage module 10 includes A, B , C three phase units composed of an upper bridge arm and/or a lower bridge arm. That is to say, each phase unit 11 can be a topological structure that only includes an upper bridge arm or a lower bridge arm, or it can also include an upper bridge arm at the same time.
  • the topology of the arm and lower arm is shown in Figure 2.
  • each phase unit 11 adopts a topological structure including only the upper bridge arm
  • the low voltage end of the upper bridge arm in each phase unit constitutes the AC end of the phase unit
  • the AC ends of the three phase units respectively correspond to the external AC system.
  • the three-phase terminals A, B, and C are connected, and the high-voltage terminals of the upper bridge arms of the three phase units in each energy storage module are commonly connected to form the positive DC bus H+ of the energy storage module.
  • the high-voltage end of the lower arm in each phase unit constitutes the AC end of the phase unit.
  • the AC ends of the three phase units correspond to A, B, and A of the external AC system.
  • each phase unit 11 adopts a topological structure including both an upper bridge arm and a lower bridge arm, as shown in Figure 2, the low voltage end of the upper bridge arm in each phase unit 11 is connected to the high voltage end of its lower bridge arm to form the phase
  • the AC terminals of the unit and the AC terminals of the three phase units are respectively connected to the three-phase terminals A, B, and C of the external AC system, and the high-voltage terminals of the upper bridge arms of the three phase units in each energy storage module 10 are commonly connected.
  • the positive DC bus H+ of the energy storage module is formed, and the low voltage ends of the lower bridge arms of the three phase units in each energy storage module 10 are commonly connected to form the negative DC bus L- of the energy storage module.
  • each bridge arm provided in this embodiment is composed of multiple fully controlled battery modules connected in series and then connected in series with a reactor L.
  • the reactor L plays the role of active power and reactive power of the AC system and energy storage system.
  • each fully controlled battery module includes a fully current controlled battery module D and a battery module E.
  • the full current control battery module includes an energy transmission control unit and a relay energy unit.
  • the relay energy unit uses an energy storage capacitor, and the energy storage capacitor is connected in parallel with the battery module E.
  • the energy transmission control unit uses multiple first fully controlled power electronic devices.
  • the specific circuit form only needs to ensure that the energy storage capacitor can be connected or disconnected from the external AC system, as shown in Figure 16.
  • 2 Two fully-controlled power electronic devices Q1 and Q2 are connected in series.
  • the common contact point between the low-voltage end of the fully-controlled power electronic device Q1 and the high-voltage end of the fully-controlled power electronic device Q2 is an input end of the energy transmission unit.
  • the fully-controlled power electronic device The high-voltage end of the electronic device Q1 or the low-voltage end of the fully-controlled power electronic device Q2 is the other input end of the energy transmission control unit.
  • the high-voltage end of the fully-controlled power electronic device Q1 and the low-voltage end of the fully-controlled power electronic device Q2 Correspondingly connected to both ends of the energy storage capacitor; or four fully controlled power electronic devices can also be used, and the specific circuit can be set accordingly by referring to the connection principle of two series-connected fully controlled power electronic devices. In this embodiment No longer.
  • the power conversion method of the AC direct grid-connected battery energy storage system provided by the present invention includes active outer loop control, reactive outer loop control and AC current control. As shown in Figure 5, it includes steps S10 to S30, which are detailed as follows:
  • the step of calculating the AC active current reference value I dref and the AC reactive current reference value I qref may be: after comparing the difference between the actual measured value of active power P acpu and the reference value of active power P acref , through proportional integral control After the proportional integral adjustment of the controller PI, the AC active current reference value I dref is obtained, that is, the d-axis current reference value; after comparing the difference between the measured reactive power value Q pu and the reactive power reference value Q ref , the proportional integral controller PI After adjustment by proportional integral, communication is obtained The reactive current reference value I qref is the q-axis current reference value.
  • the AC active current reference value I dref and the AC reactive current reference value I qref are obtained through closed-loop control of the actual measured value of active power P acpu and the actual measured value of reactive power Q acpu , so that the active power can be accurately controlled.
  • P acpu and reactive power Q acpu enable the AC direct grid-connected battery energy storage system to accurately respond to the grid's active power and reactive power instructions for the energy storage system.
  • the closed-loop tracking control is specifically: the difference obtained by subtracting the unit value I dpu of the actual measured value of the d-axis current from the d-axis current reference value I dref , and the difference is output through the proportional integral controller PI, Obtain the d-axis current control fine-tuning amount.
  • the d-axis current control fine-tuning amount output is negative, it is the same as the per unit value V dpu of the d-axis voltage actual measurement value and the per unit value I qpu *(L pu +L armpu /2)
  • the d-axis modulation ratio M d is obtained; similarly, the difference obtained by subtracting the q-axis current reference value I qref from the per unit value I qpu of the q-axis current measured value is obtained.
  • the difference is proportional
  • the PI output of the integral controller is used to obtain the q-axis current control fine-tuning amount.
  • L pu is the standard unit value of the AC output reactance of the AC direct grid-connected battery energy storage system
  • L armpu is the standard unit value of the bridge arm reactance
  • I qpu is obtained by dividing the current of the three phases A, B, and C by abc/dq conversion by the current reference value of the three-phase terminals A, B, and C
  • the standard unit value V dpu of the actual measured value of the d-axis voltage is obtained by dividing the voltage at the three-phase terminals A, B, and C by the voltage reference value at the three-phase terminals A, B, and C after abc/dq conversion.
  • step S20 the formula for calculating the reference voltage of the upper bridge arm and/or the lower bridge arm in phases A, B, and C is:
  • V ref_Ap V dcn /2-m a ⁇ V dcn /2
  • V ref_An V dcn /2+m a ⁇ V dcn /2
  • V ref_Bp V dcn /2-m b ⁇ V dcn /2
  • V ref_Bn V dcn /2+m b ⁇ V dcn /2
  • V ref_Cp V dcn /2-m c ⁇ V dcn /2
  • V ref_Cn V dcn /2+m c ⁇ V dcn /2
  • V ref_Ap represents the reference voltage of the upper bridge arm in phase A
  • V ref_An represents the reference voltage of the lower bridge arm in phase A
  • V ref_Bp represents the reference voltage of the upper bridge arm in phase B
  • V ref_Bn represents the lower bridge arm in phase B.
  • the reference voltage of the arm V ref_Cp represents the reference voltage of the upper arm in phase C
  • V ref_Cn represents the reference voltage of the lower arm in phase C
  • V dcn represents the DC voltage rating of the positive DC bus to the negative DC bus.
  • the function of the reference voltages V ref_Ap ⁇ V ref_Cn is to approach the reference voltages V ref_Ap ⁇ V ref_Cn through the output voltage of each bridge arm, so that the AC terminals of the three phase units of the AC direct grid-connected battery energy storage system
  • the output voltage approaches the AC terminal output voltage reference values m a ⁇ V dcn /2, m b ⁇ V dcn /2, m c ⁇ V dcn /2.
  • step S30 the formula for calculating the number of full-current control battery modules that need to be put into the upper arm and/or the lower arm of phases A, B, and C is:
  • N Ap ROUND (V ref_Ap /V cn ) N
  • An ROUND(V ref_An /V cn ) N
  • Bp ROUND(V ref_Bp /V cn ) N
  • Bn ROUND(V ref_Bn /V cn ) N
  • Cp ROUND (V ref_Cp /V cn )
  • Cn ROUND(V ref_Cn /V cn )
  • N Ap represents the number of full-current control battery modules put in the upper arm of phase A
  • N An represents the number of full-current control battery modules put in the lower arm of phase A
  • N Bp represents the number of full-current control battery modules put in the upper arm of phase B.
  • the number of full-current control battery modules N Bn represents the number of full-current control battery modules put in the lower arm of phase B
  • N Cp represents the number of full-current control battery modules put in the upper arm of phase C
  • N Cn represents the number of full-current control battery modules put in the upper arm of phase C
  • the full current input into the bridge arm controls the number of battery modules
  • ROUND represents the rounding function
  • V cn represents the rated voltage value of the energy storage capacitor.
  • the power conversion method of the AC direct grid-connected battery energy storage system provided by this embodiment can realize the integration of the battery energy storage system and the AC system by adding a full-current control battery module to each battery module and controlling it accordingly. Compared with the traditional grid-connected battery energy storage system, the AC/DC power conversion between The corresponding losses of the system make the provided AC direct grid-connected battery energy storage system have lower losses.
  • the full current control battery module D provided by the present invention also includes a current control unit, as shown in Figure 16,
  • the current control unit uses six three-phase full-bridge circuits composed of second fully controlled power electronic devices (Q9a, Q9b, Q9c, Q10a, Q10b, Q10c).
  • Each full-current control unit controls two of the three-phase full-bridge circuits in the battery module.
  • the input end is connected to both ends of the energy storage capacitor in the full-current control battery module.
  • Each phase AC output end of the three-phase full-bridge circuit in each full-current control battery module is connected to a battery module E through an inductor.
  • the power conversion method provided by the present invention also sets average capacitor voltage control and inductor current control, as shown in Figure 6, specifically:
  • Step 1 Measure and obtain the voltage v ci k of the energy storage capacitor C and the current I dis of the inductor of all full-current control battery modules in each bridge arm.
  • each energy storage module when each energy storage module includes three phase units A, B, and C composed of an upper bridge arm and a lower bridge arm, the value of k is 1 to 6, corresponding to the three phase units A, B, and C. There are a total of 6 bridge arms; similarly, when each energy storage module includes three phase units A, B, and C composed of upper bridge arms or lower bridge arms, the value range of k is no longer in this embodiment. Repeat.
  • the value range of i is 1 ⁇ N, N is the total number of full-current control battery modules in each bridge arm.
  • N and N Ap For example, for the A-phase upper bridge arm, the relationship between N and N Ap is: N ⁇ N Ap ; for the A-phase lower bridge arm, then the relationship between N and N An is: N ⁇ N An ; for the B-phase upper bridge arm, the relationship between N and N Bp is: N ⁇ N Bp ; for the B-phase lower bridge arm, then the relationship between N and N Bn The relationship is: N ⁇ N Bn ; for the C-phase upper bridge arm, the relationship between N and N Cp is: N ⁇ N Cp ; for the C-phase lower bridge arm, the relationship between N and N Cn is: N ⁇ N Cn .
  • Step 2 Average the voltage v ci k of the energy storage capacitors in all full-current control battery modules in each bridge arm. Finally, after dividing by (6*N), the average value V cavg of the energy storage capacitor voltage in each bridge arm is obtained. The average voltage V cavg is then compared with the reference value Vcref of the average capacitor voltage of the energy storage capacitor. After the proportional integral controller PI is used, the discharge current command I ord of each battery module is obtained. In the same way, it can be seen that when each energy storage module includes three phase units A, B, and C composed of upper bridge arms or lower bridge arms, the control principle of obtaining the discharge current command of each battery module will not be described in detail in this embodiment. .
  • Step 3 After comparing the difference between the discharge current command I ord of each battery module and the current I dis of the inductor in the corresponding full-current control battery module, it is controlled in a closed loop by a proportional-integral controller or a current hysteresis controller.
  • the duty cycle signals of the six second fully controlled power electronic devices in each full current control battery module are obtained, corresponding to controlling the on/off status of the six second fully controlled power electronic devices in each full current control battery module,
  • the current of the inductor in each full-current control battery module is closed-loop controlled to maintain the balance between the active power output by the AC direct grid-connected battery energy storage system to the external AC system and the discharge power of the full-current control battery module.
  • the average voltage of the energy storage capacitors in all the input full-current control battery modules is used to represent the balance between the AC active power of the energy storage system and the discharge energy of the battery modules of the energy storage system.
  • the discharge power of the battery energy storage system to the AC system increases, the average voltage of the energy storage capacitor will decrease.
  • the battery module discharge current command value I ord can be increased to increase the battery module capacity. The discharge energy thus supplements the voltage drop caused by the energy storage capacitor discharging the AC system.
  • the average voltage of the energy storage capacitor will increase.
  • the average capacitor voltage control provided by the present invention can reduce the battery module discharge current command value I ord to reduce The battery module discharges energy, thereby absorbing the voltage rise caused by the energy storage capacitor reducing the discharge to the AC system.
  • the AC terminals of the three phase units in each energy storage module 10 are respectively connected to the three-phase terminals A, B, and C of the external AC system through AC transformers, which can flexibly match different voltage levels of the external AC system.
  • each phase unit may be composed of three bridge arms, and the combination of the three bridge arms includes a combination of three upper bridge arms or a combination of three lower bridge arms. Compared with the structure of two bridge arms for each phase unit, the number of energy storage modules corresponding to the energy storage system can be more conveniently configured.
  • the AC direct grid-connected battery energy storage system provided by the present invention may also include a redundant phase unit.
  • the topology of the redundant phase unit is the same as the topology of the phase unit in the energy storage module.
  • the redundant phase unit The AC end of the unit is connected to one end of the three single-phase AC circuit breakers, and the other ends of the three single-phase AC circuit breakers are connected to the A, B, and C three-phase ends of the external AC system respectively; and three of the energy storage modules
  • the AC terminals of each phase unit are connected to the A, B, and C three-phase terminals of the external AC system through AC circuit breakers.
  • any one of the A, B or C phase units of the AC direct grid-connected energy storage system fails, by closing the corresponding A-phase, B-phase or C-phase single-phase AC circuit breaker, the The redundant phase unit is connected to the corresponding external AC system to achieve redundant backup of the energy storage system phase unit and avoid the failure of a single phase unit causing the energy storage module to become inoperable.
  • FIG. 7 is a circuit schematic diagram of an AC direct grid-connected battery energy storage system provided by a specific embodiment of the present invention.
  • the battery energy storage system includes one energy storage module, and the energy storage module consists of three
  • Each phase unit 11 is composed of an upper bridge arm 11a and a lower bridge arm 11b connected in series.
  • the high-voltage ends of each upper bridge arm 11a are connected together to form the positive DC bus H+ of the energy storage module 10.
  • Each lower bridge arm 11a is connected in series.
  • the low-voltage ends of the bridge arms 11b are connected together to form the negative DC bus L- of the energy storage module 10.
  • the common contact point of the upper bridge arm and the lower bridge arm in each phase unit 11 constitutes the AC output end of the phase unit.
  • the AC output terminals of the three-phase units are connected to the three-phase terminals A, B, and C of the external AC system, and each upper arm and lower arm are composed of multiple fully controlled battery modules connected in series and then connected to the reactor. L are connected in series, and each fully controlled battery module includes a fully current controlled battery module D and a battery module E.
  • each phase unit 11 is composed of an upper bridge arm 11a and a lower bridge arm 11b connected in series.
  • Each upper bridge arm 11a is composed of N fully controlled battery modules and a reactor L connected in series, each fully controlled
  • Each type of battery module includes a full-current control battery module D and a battery module E.
  • the high-voltage end of the first full-current control battery module is the high-voltage end of the upper bridge arm 11a
  • the low-voltage end of the first full-current control battery module is connected to the high-voltage end of the second full-current control battery module, and so on.
  • the low-voltage end of the N-1th full-current control battery module is connected to the high-voltage end of the N-th full-current control battery module, and the low-voltage end of the N-th full-current control battery module is connected to one end of the reactor L of the upper arm.
  • the other end of the reactor L of the upper arm is connected to one end of the reactor of the lower arm 11b.
  • the other end of the reactor of the lower arm is connected to the high-voltage end of the first full-current control battery module in the lower arm, and the low-voltage end of the first full-current control battery module in the lower arm is connected to the second end of the lower arm.
  • the high-voltage terminals of the N-1th full-current control battery module in the lower arm are connected to the high-voltage terminal of the N-th full-current control battery module in the lower arm.
  • the low-voltage end of the Nth full-current control battery module in the lower arm constitutes the low-voltage end of the lower arm 11b.
  • Figure 8 is similar to the embodiment of Figure 7. The difference is that the high-voltage end of the upper arm 11a of each phase unit 11 is one end of the upper reactor L, and the other end of the upper reactor L is connected to the first full current control of the upper arm.
  • the high-voltage end of the battery module is connected, the low-voltage end of the first full-current control battery module on the upper arm is connected to the high-voltage end of the second full-current control battery module, and so on, the N-1th full-current control battery module
  • the low-voltage end of is connected to the high-voltage end of the Nth full-current control battery module, and the low-voltage end of the Nth full-current control battery module is connected to the high-voltage end of the first full-current control battery module in the lower bridge arm 11b.
  • the low-voltage end of the first full-current control battery module in the lower arm 11b is connected to the high-voltage end of the second full-current control battery module in the lower arm 11b, and so on, the N-1th full-current control end of the lower arm 11b
  • the low-voltage end of the battery module is connected to the high-voltage end of the Nth full-current control battery module 1 in the lower arm 11b, and the low-voltage end of the Nth full-current control battery module 1 in the lower arm 11b is connected to one end of the lower arm reactor. Connected to each other, the other end of the lower arm reactor constitutes the low voltage end of the lower arm 11b.
  • Figure 9 is similar to the embodiment of Figure 7. The difference is that the energy storage module 10 is connected to the three-phase terminals A, B, and C of the external AC system through an AC circuit breaker, and the energy storage system is also equipped with an additional phase unit, which is called the The phase unit is a redundant phase unit 12.
  • the high-voltage end of the redundant phase unit 12 is connected to the positive DC bus H+.
  • the low-voltage end of the redundant phase unit 12 is connected to the negative DC bus L-.
  • the AC output of the redundant phase unit 12 is The terminal is connected to one end of the three single-phase AC circuit breakers, and the other end of the three single-phase AC circuit breakers is connected to the A, B, and C three-phase terminals of the external AC system.
  • any of the A, B or C phase units of the AC direct grid-connected battery energy storage system fails, that is, a downlink communication failure, a downlink communication failure, the overtemperature of the single cell in the battery module, or the overtemperature of the power electronic device When, it is judged that the full-current control battery module is in a fault state.
  • phase unit When the number of full-current control battery modules in a fault state in a phase unit exceeds the number of redundant full-current control battery modules, it is judged that the phase unit is in a fault state, and the corresponding The single-phase AC circuit breaker in phase A, B or C can connect the redundant phase unit 12 to the corresponding external AC system, thereby realizing the redundant backup of the phase unit of the energy storage system and avoiding the failure of the energy storage module caused by the failure of a single phase unit. run.
  • the redundant phase unit 12 provided by this embodiment can also conveniently realize non-stop online operation of each energy storage module 10. dimension, when the upper arm 11a or lower arm 11b of a certain energy storage module 10 fails, causing a phase unit 11 of the energy storage module 10 to fail and cannot continue to operate, the redundant phase unit 12 can be put into operation to replace the energy storage The faulty phase unit of module 10 causes a phase unit failure to occur. The failed energy storage module 10 can still maintain uninterrupted operation, and then the failed phase unit can be inspected and maintained online.
  • the specific implementation method is: lock the faulty energy storage module 10, then close the single-phase AC circuit breaker of the X phase (for example, A phase) of the redundant phase unit 12, and then close the redundant phase unit 12 and the faulty energy storage module.
  • the non-faulty phase of the module is controlled as a new energy storage module and the new energy storage module is unlocked.
  • the embodiment of Figure 10 is a further improvement of the embodiment of Figure 9.
  • the AC output end of each phase unit is connected to the external AC system through an AC transformer, so that it can flexibly match different voltage levels of the external AC system.
  • each AC direct-grid-connected energy storage system can include two or more energy storage modules 10 , and the positive DC bus of each energy storage module 10 is different. They are connected to each other, and the negative DC bus bars of each energy storage module 10 are not connected to each other, so that mutual coupling of each energy storage module 10 on the DC side can be avoided.
  • a single AC direct grid-connected energy storage system includes a total of two energy storage modules 10.
  • the embodiment of Fig. 12 is similar to the embodiment of Fig. 11. The difference is that in the embodiment of Fig. 12, the positive DC buses H+ of each energy storage module 10 are connected to each other, and the negative DC buses L- of each energy storage module 10 are also connected to each other. Together, the positive DC bus and the negative DC bus of the energy storage module 10 can be further connected to an external DC system.
  • each energy storage module is composed of three phase units, each phase unit 11 is composed of an upper bridge arm, and each upper bridge arm is composed of N fully controlled battery modules and a reactor L Connected in series, each fully controlled battery module includes a fully current controlled battery module D and a battery module E.
  • the high-voltage end of the first full-current control battery module is the high-voltage end of the upper arm
  • the low-voltage end of the first full-current control battery module is connected to the high-voltage end of the second full-current control battery module, and so on.
  • the low-voltage end of the N-1th full-current control battery module is connected to the high-voltage end of the Nth full-current control battery module, and the low-voltage end of the Nth full-current control battery module 1 is connected to one end of the reactor L of the upper arm.
  • the other end of the reactor L of the upper arm is connected to the A, B or C three-phase terminals of the external AC system.
  • Figure 14 is a combination of the technical route of the embodiment of Figure 7 and the embodiment of Figure 13.
  • the complete energy storage module 10 composed of three phase units 11 shown in Figure 7 and the energy storage module 10 composed of three lower bridge arms 11b The combination.
  • the AC output of the energy storage module composed of the three lower bridge arms 11b is connected with the AC output of the energy storage module composed of the three phase units 11, and connected to the A, B, and C three-phase terminals of the external AC system.
  • the advantage of Figure 14 is that the minimum divisible unit of each energy storage system is three bridge arms, making it easy to configure the number of energy storage modules corresponding to the energy storage system as needed.
  • FIG 15 is another implementation form of the topology of Figure 13.
  • the energy storage system includes two energy storage modules, each of which is composed of three lower bridge arms 11b.
  • Figure 16 illustrates an implementation topology of the full-current control battery module, which consists of fully-controlled power electronic devices Q1, Q2, Q9a, Q9b, Q9c, Q10a, Q10b, Q10c, energy storage capacitor C, inductors La, Lb, Lc, freewheeling diode D and battery module E.
  • Each fully controlled power electronic device uses a transistor and a diode connected in anti-parallel.
  • Each battery module E is composed of 12 to 24 single cells connected in series.
  • the fully controlled power electronic devices Q1 and Q2 are connected in series and in parallel with the energy storage capacitor C.
  • the capacitor C is connected to the AC system and can draw AC current from the AC system or inject AC current into the AC system.
  • Q2 is turned on and Q1 is turned off, the full current control battery module is bypassed by Q2, and capacitor C neither draws AC current from the AC system nor releases AC current to the AC system.
  • Q9a, Q10a, La, Q9b, Q10b, Lb, Q9c, Q1c, and Lc constitute three sets of energy transmission channels connecting the capacitor C and the battery module E.
  • Q9a, Q10a, and La Take Q9a, Q10a, and La as an example.
  • Q9a When it is necessary to charge the battery module E, keep Q10a in the off state.
  • the capacitor C charges the battery module E through Q9a and La.
  • Q9a is turned off, then La The current flows through La, battery module E, and the anti-parallel diode of Q10a to form a freewheeling loop, and capacitor C no longer charges battery module E.
  • Each bridge arm in Figure 7 is composed of multiple fully controlled battery modules connected in series.
  • the capacitor C voltage of each fully controlled battery module is U c .
  • Q1 of the fully controlled battery module is turned on and Q2 is turned off, all The controlled battery module is in the input state, and the output voltage of the fully controlled battery module is U c .
  • Q2 of the fully controlled battery module is turned on and Q1 is turned off, the fully controlled battery module is in the cut-off state, and the output of the fully controlled battery module The voltage is 0.
  • each bridge arm After obtaining the reference voltages V ref_Ap , V ref_An , V ref_Bp , V ref_Bn , V ref_Cp , and V ref_cn of each bridge arm, record the rated value of the capacitor voltage as V cn , and each bridge arm (Take the A-phase upper bridge arm as an example)
  • the output voltage of each bridge arm can be approximated its reference voltage.
  • phase A the equivalent AC voltage output by phase A is (V ref_An -V ref_Ap )/2.
  • V ref_An and V ref_Ap the equivalent voltage of phase A can be adjusted.
  • the size of the output AC voltage controls the power exchanged between phase A and the external AC system.

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Abstract

本发明涉及电力储能技术领域，公开了一种交流直接并网型电池储能***的功率变换方法，其中，该交流直接并网型电池储能***包括若干个储能模块，每个储能模块均包括A、B、C三个由上桥臂和/或下桥臂组成的相单元，各桥臂均采用多个全控制型电池模块串联后再与电抗器串联而成，各储能模块中所有上桥臂的高压端共接构成该储能模块的正极直流母线，各储能模块中所有下桥臂的低压端共接构成该储能模块的负极直流母线，每个相单元中上桥臂的低压端与下桥臂的高压端相连构成该相单元的交流端，三个相单元的交流端对应与外部交流***的A、B、C三相端相连。本发明能低成本、低损耗地实现电池储能***与交流***的交流/直流功率变换。

Description

一种交流直接并网型电池储能***的功率变换方法 技术领域
本发明属于电力储能技术领域，更具体地，涉及一种交流直接并网型电池储能***的功率变换方法。
背景技术
随着我国“3060”双碳目标的提出，电力***中风力发电、光伏发电的比重将大规模上升，为了抵御大规模新能源发电带来的间歇性与波动性问题，电力储能成为未来电力***不可或缺的部分。
现有的电池储能***通常采用拼装式技术，由多个电池单体串并联构成电池模块，多个电池模块串联构成电池簇，多个电池簇并联构成电池堆，电池堆的正、负直流母线与功率变换***的正、负直流母线相连接，功率变换***的交流侧再与外部交流***相连接从而构成并网电池储能***。其中，功率变换***通常采用的是两电平或三电平电压源型换流器的拓扑结构，用于实现电池堆与外部交流***间的直流/交流功率变换的同时，还需配置交流滤波器以降低功率变换***的交流输出谐波，会给并网电池储能***带来成本高、损耗高的问题。
如此，如何低成本、低损耗地实现电池储能***与交流***的交流/直流功率变换是亟需解决的技术问题。
发明内容
针对现有技术的缺陷，本发明的目的在于提供一种交流直接并网型电池储能***的功率变换方法，能低成本、低损耗地实现电池储能***与交流***的交流/直流功率变换。
为实现上述目的，本发明提供了一种交流直接并网型电池储能***的功率变换方法，所述交流直接并网型电池储能***包括若干个储能模块，每个储能模块均包括A、B、C三个由上桥臂和/或下桥臂组成的相单元，各桥臂均采用多个全控制型电池模块串联后再与电抗器串联而成；
其中，当各相单元仅包括上桥臂时，各相单元中上桥臂的低压端构成该相单元的交流端，三个相单元的交流端分别对应与外部交流***的A、B、C三相端相连，各储能模块中的三个相单元中上桥臂的高压端共接构成该储能模块的正极直流母线H+；当各相单元仅包括下桥臂时，各相单元中下桥臂的高压端构成该相单元的交流端，三个相单元的交流端对应与外部交流***的A、B、C三相端相连，各储能模块中的三个相单元中下桥臂的低压端共接构成该储能模块的负极直流母线L-；当各相单元11同时包括上桥臂和下桥臂时，各储能模块中所有上桥臂的高压端共接构成该储能模块的正极直流母线，各储能模块中所有下桥臂的低压端共接构成该储能模块的负极直流母线，每个相单元中上桥臂的低压端与下桥臂的高压端相连构成该相单元的交流端，三个相单元的交流端分别对应与外部交流***的A、B、C三相端相连；
各全控制型电池模块均包括一全电流控制电池模块和一电池模块，全电流控制电池模块包括能量传输控制单元和中继能量单元，中继能量单元采用储能电容，储能电容与电池模块并联；能量传输控制单元采用多个第一全控型电力电子器件，用于实现储能电容与外部交流***的连通或断开；
所述功率变换方法包括如下步骤：
(1)获取并根据外部交流***A、B、C三相端的电压和电流，对应计算交流直接并网型电池储能***的有功功率实测值Pacpu和无功功率实测值Qacpu，然后根据有功功率实测值Pacpu、无功功率实测值Qacpu、有功功率参考值Pacref和无功功率参考值Qref，计算交流有功电流参考值Idref和交流无功电流参考值Iqref；
(2)对参考值Idref和参考值Iqref进行闭环跟踪控制，得到交流调制比ma、mb、mc，然后根据交流调制比ma、mb、mc，计算A、B、C相中上桥臂和/或下桥臂参考电压；其中，计算A、B、C相中上桥臂和/或下桥臂的参考电压的公式为：
Vref_Ap＝Vdcn/2-ma×Vdcn/2
Vref_An＝Vdcn/2+ma×Vdcn/2
Vref_Bp＝Vdcn/2-mb×Vdcn/2
Vref_Bn＝Vdcn/2+mb×Vdcn/2
Vref_Cp＝Vdcn/2-mc×Vdcn/2
Vref_Cn＝Vdcn/2+mc×Vdcn/2
式中，Vref_Ap表示A相中上桥臂的参考电压；Vref_An表示A相中下桥臂的参考电压；Vref_Bp表示B相中上桥臂的参考电压；Vref_Bn表示B相中下桥臂的参考电压；Vref_Cp表示C相中上桥臂的参考电压；Vref_Cn表示C相中下桥臂的参考电压；Vdcn表示正极直流母线对负极直流母线直流电压额定值；
(3)根据A、B、C相中上桥臂和/或下桥臂参考电压，计算A、B、C相中上桥臂和/或下桥臂需投入的全电流控制电池模块数量，然后根据各桥臂需投入的全电流控制电池模块数量，对应控制各桥臂中全电流控制电池模块中的第一全控型电力电子器件，使各桥臂的输出电压对应与其参考电压的差值在设定范围内，从而实现交流直接并网型电池储能***与外部交流***的功率变换。
本发明提供的交流直接并网型电池储能***的功率变换方法，通过在各电池模块中增设一全电流控制电池模块，并通过对其进行相应控制，可实现电池储能***与交流***之间的交流/直流功率变换，相比于传统并网电池储能***，可省去其中的功率变换***，大大降低***成本；同时，由于省去了功率变换***，从而省去了功率变换***对应的损耗，使得所提供的交流直接并网型电池储能***的损耗更低。
进一步地，步骤(3)中，计算A、B、C相中上桥臂和/或下桥臂需投入的全电流控制电池模块数量的公式为：
NAp＝ROUND(Vref_Ap/Vcn)
NAn＝ROUND(Vref_An/Vcn)
NBp＝ROUND(Vref_Bp/Vcn)
NBn＝ROUND(Vref_Bn/Vcn)
NCp＝ROUND(Vref_Cp/Vcn)
NCn＝ROUND(Vref_Cn/Vcn)
式中，NAp表示A相中上桥臂投入的全电流控制电池模块数量；NAn表示A相中下桥臂投入的全电流控制电池模块数量；NBp表示B相中上桥臂投入的全电流控制电池模块数量；NBn表示B相中下桥臂投入的全电流控制电池模块数量；NCp表示C相中上桥臂投入的全电流控制电池模块数量；NCn表示C相中下桥臂投入的全电流控制电池模块数量；ROUND表示四舍五入取整函数；Vcn表示所述储能电容的额定电压值。
进一步地，步骤(1)中，计算得到交流有功电流参考值Idref和交流无功电流参考值Iqref的步骤，具体为：
将有功功率实测值Pacpu和有功功率参考值Pacref作差比较后，经比例积分调节后得到交流有功电流参考值Idref；将无功功率实测值Qpu与无功功率参考值Qref作差比较后，经比例积分调节后得到交流无功电流参考值Iqref。
进一步地，所述全电流控制电池模块还包括电流控制单元，所述电流控制单元采用6个由第二全控型电力电子器件组成的三相全桥电路，各全电流控制电池模块中三相全桥电路的两输入端对应与该全电流控制电池模块中储能电容的两端相连，各全电流控制电池模块中三相全桥电路的每相交流输出端均对应通过一电感分别与一电池模块相连；
所述功率变换方法还包括如下步骤：
获取各个桥臂中的所有全电流控制电池模块中储能电容的电压和其中电感的电流Idis；
将各个桥臂中的所有全电流控制电池模块中储能电容的电压求平均值后，与所述储能电容平均电容电压的参考值VCref进行作差比较，将作差比较后得到的差值经比例积分调节后，得到各电池模块的放电电流指令Iord；
将各电池模块的放电电流指令Iord分别与对应的各全电流控制电池模块中电感的电流Idis作差比较后，经比例-积分控制器或电流滞环控制器闭环控制后，得到各全电流控制电池模块中6个第二全控型电力电子器件的占空比信号，对应控制各全电流控制电池模块中的6个第二全控型电力电子器件开通/关断状态，从而对各全电流控制电池模块中电感的电流进行闭环控制，保持交流直接并网型电池储能***向外部交流***输出的有功功率与全电流控制电池模块放电功率的平衡。
进一步地，各储能模块中三个相单元的交流端通过交流变压器分别对应与外部交流***的A、B、C三相端相连。
进一步地，每个相单元由3个桥臂组成，3个桥臂的组合形式包括3个上桥臂的组合或3个下桥臂的组合。
进一步地，所述交流直接并网型电池储能***还包括冗余相单元，所述冗余相单元的交流端与3个单相交流断路器的一端相连，3个单相交流断路器的另一端分别对应与外部交流***的A、B、C三相端相连；且各储能模块中三个相单元的交流端通过交流断路器分别对应与外部交流***的A、B、C三相端相连。
进一步地，所述第一全控型电力电子器件和所述第二全控型电力电子器件均采用1个或多个晶体管及与其反并联的二极管；各电池模块采用12～24节单体电池串联而成。
进一步地，所述全电流控制电池模块中的能量传输控制单元包括2个第一全控型电力电子器件，分别为全控型电力电子器件Q1和Q2，所述全控型电力电子器件Q1的低压端 与所述全控型电力电子器件Q2的高压端相连，所述全控型电力电子器件Q1的高压端与所述储能电容的一端相连，所述全控型电力电子器件Q2的低压端与所述储能电容的另一端相连。
附图说明
图1是本发明一实施例提供的交流直接并网型电池储能***的模块框图；
图2是本发明另一实施例提供的交流直接并网型电池储能***的模块框图；
图3是本发明一实施例提供的桥臂的电路原理示意图；
图4是本发明一实施例提供的全电流控制电池模块的模块框图；
图5是本发明一实施例提供的交流直接并网型电池储能***的功率交换方法的控制原理图；
图6是本发明另一实施例提供的交流直接并网型电池储能***的功率交换方法的控制原理图；
图7是本发明实施例一提供的交流直接并网型电池储能***拓扑结构；
图8是本发明实施例二提供的交流直接并网型电池储能***拓扑结构；
图9是本发明实施例三提供的交流直接并网型电池储能***拓扑结构；
图10是本发明实施例四提供的交流直接并网型电池储能***拓扑结构；
图11是本发明实施例五提供的交流直接并网型电池储能***拓扑结构；
图12是本发明实施例六提供的交流直接并网型电池储能***拓扑结构；
图13是本发明实施例七提供的交流直接并网型电池储能***拓扑结构；
图14是本发明实施例八提供的交流直接并网型电池储能***拓扑结构；
图15是本发明实施例九提供的交流直接并网型电池储能***拓扑结构；
图16是本发明一实施例提供的全电流控制电池模块的拓扑结构。
具体实施方式
为了便于理解本发明，下面将参照相关附图对本发明进行更全面的描述。附图中给出了本发明的首选实施例。但是，本发明可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本发明的公开内容更加透彻全面。
除非另有定义，本文所使用的所有的技术和科学术语与属于本发明的技术领域的技术人员通常理解的含义相同。本文中在本发明的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本发明。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。在本发明的描述中，“多个”的含义是至少两个，例如两个，三个等，除非另有明确具体的限定。在本发明的描述中，“若干”的含义是至少一个，例如一个，两个等，除非另有明确具体的限定。
为低成本、低损耗地实现电池储能***与交流***的交流/直流功率变换，本发明省去了传统并网电池储能***中用于衔接电池储能***与交流***的集中式功率变换系 统，提供了一种交流直接并网型电池储能***，并通过相应的功率变换算法来实现该交流直接并网型电池储能***与交流***的交流/直流功率变换。
图1是本发明一实施例提供的交流直接并网型电池储能***的模块框图，如图1所示，该***包括若干个储能模块10，每个储能模块10均包括A、B、C三个由上桥臂和/或下桥臂组成的相单元，也即是说，各相单元11可以是仅包括上桥臂或下桥臂的拓扑结构，也可以是同时包括上桥臂和下桥臂的拓扑结构，如图2所示。
其中，当各相单元11采用仅包括上桥臂的拓扑结构时，各相单元中上桥臂的低压端构成该相单元的交流端，三个相单元的交流端分别对应与外部交流***的A、B、C三相端相连，且各储能模块中的三个相单元中上桥臂的高压端共接构成该储能模块的正极直流母线H+。当各相单元采用仅包括下桥臂的拓扑结构时，各相单元中下桥臂的高压端构成该相单元的交流端，三个相单元的交流端对应与外部交流***的A、B、C三相端相连，且各储能模块中的三个相单元中下桥臂的低压端共接构成该储能模块的负极直流母线L-。当各相单元11均采用同时包括上桥臂和下桥臂的拓扑结构时，如图2所示，各相单元11中上桥臂的低压端和其下桥臂的高压端相连构成该相单元的交流端，三个相单元的交流端分别对应与外部交流***的A、B、C三相端相连，且各储能模块10中的三个相单元中上桥臂的高压端共接构成该储能模块的正极直流母线H+，各储能模块10中三个相单元中下桥臂的低压端共接构成该储能模块的负极直流母线L-。
如图3所示，本实施例提供的各桥臂均采用多个全控制型电池模块串联后再与电抗器L串联而成，电抗器L起着交流***与储能***有功功率与无功功率变换的桥梁作用。且各全控制型电池模块均包括一全电流控制电池模块D和一电池模块E。
如图4所示，全电流控制电池模块包括能量传输控制单元和中继能量单元。其中，中继能量单元采用储能电容，储能电容与电池模块E并联。能量传输控制单元采用多个第一全控型电力电子器件，其具体电路形式只需保证能实现储能电容与外部交流***的连通或断开即可，如图16所示，比如可采用2个串联的全控型电力电子器件Q1和Q2，全控型电力电子器件Q1的低压端与全控型电力电子器件Q2的高压端共接点为该能量传输单元的一输入端，全控型电力电子器件Q1的高压端或全控型电力电子器件Q2的低压端为该能量传输控制单元的另一输入端，全控型电力电子器件Q1的高压端与全控型电力电子器件Q2的低压端对应与储能电容的两端相连；亦或还可采用4个全控型电力电子器件，其具体电路可参照采用2个串联的全控型电力电子器件的连接原理进行相应设置，本实施例不再赘述。
本发明提供的交流直接并网型电池储能***的功率变换方法包括有功外环控制、无功外环控制和交流电流控制，如图5所示，包括步骤S10～S30，详述如下：
S10，获取并根据外部交流***A、B、C三相端的电压和电流，对应计算交流直接并网型电池储能***的有功功率实测值Pacpu和无功功率实测值Qacpu，然后根据实测值Pacpu、实测值Qacpu、有功功率参考值Pacref和无功功率参考值Qref，计算交流有功电流参考值Idref和交流无功电流参考值Iqref。
步骤S10中，计算得到交流有功电流参考值Idref和交流无功电流参考值Iqref的步骤可以为：将有功功率实测值Pacpu和有功功率参考值Pacref作差比较后，通过比例积分控制器PI经比例积分调节后得到交流有功电流参考值Idref，即d轴电流参考值；将无功功率实测值Qpu与无功功率参考值Qref作差比较后，通过比例积分控制器PI经比例积分调节后得到交流 无功电流参考值Iqref，即q轴电流参考值。
在本实施例中，通过对有功功率实测值Pacpu及无功功率实测值Qacpu的闭环控制得到交流有功电流参考值Idref和交流无功电流参考值Iqref，从而可以精确地控制有功功率Pacpu和无功功率Qacpu，使得交流直接并网型电池储能***精确地响应电网对储能***的有功功率和无功功率指令。
S20，对参考值Idref和参考值Iqref进行闭环跟踪控制，得到A、B、C坐标下的交流调制比ma、mb、mc，然后根据交流调制比ma、mb、mc，计算A、B、C相中上桥臂和/或下桥臂的参考电压。
在本实施例中，闭环跟踪控制具体为：将d轴电流参考值Idref减去d轴电流实测值的标幺值Idpu后得到的差值，该差值经过比例积分控制器PI输出，得到d轴电流控制微调量，该d轴电流控制微调量输出取负后，与d轴电压实测值的标幺值Vdpu及q轴电流实测值的标幺值Iqpu*(Lpu+Larmpu/2)叠加后，得到d轴调制比Md；同理，将q轴电流参考值Iqref减去q轴电流实测值的标幺值Iqpu后得到的差值，该差值经过比例积分控制器PI输出，得到q轴电流控制微调量，该q轴电流控制微调量输出取负后，与q轴电压实测值Vqpu及﹣Iqpu*(Lpu+Larmpu/2)叠加后，得到q轴调制比Mq；然后d轴调制比Md及q轴调制比Mq经dq/abc转换后，即可得到A、B、C坐标下的交流调制比ma、mb、mc。
其中，Lpu为交流直接并网型电池储能***交流输出电抗的标幺值；Larmpu为桥臂电抗的标幺值；d轴电流实测值的标幺值Idpu、q轴电流实测值的标幺值Iqpu为A、B、C三相的电流经abc/dq转换后，再除以A、B、C三相端的电流基准值得到；d轴电压实测值的标幺值Vdpu、q轴电压实测值的标幺值Vqpu为A、B、C三相端的电压经abc/dq转换后，再除以A、B、C三相端的电压基准值得到。
步骤S20中，计算A、B、C相中上桥臂和/或下桥臂的参考电压的公式为：
Vref_Ap＝Vdcn/2-ma×Vdcn/2
Vref_An＝Vdcn/2+ma×Vdcn/2
Vref_Bp＝Vdcn/2-mb×Vdcn/2
Vref_Bn＝Vdcn/2+mb×Vdcn/2
Vref_Cp＝Vdcn/2-mc×Vdcn/2
Vref_Cn＝Vdcn/2+mc×Vdcn/2
式中，Vref_Ap表示A相中上桥臂的参考电压；Vref_An表示A相中下桥臂的参考电压；Vref_Bp表示B相中上桥臂的参考电压；Vref_Bn表示B相中下桥臂的参考电压；Vref_Cp表示C相中上桥臂的参考电压；Vref_Cn表示C相中下桥臂的参考电压；Vdcn表示正极直流母线对负极直流母线直流电压额定值。
根据上述计算A、B、C相中上桥臂和/或下桥臂的参考电压的公式可知：
ma×Vdcn/2＝(Vref_An-Vref_Ap)/2
mb×Vdcn/2＝(Vref_Bn-Vref_Bp)/2
mc×Vdcn/2＝(Vref_Cn-Vref_Cp)/2
在本实施例中，参考电压Vref_Ap～Vref_Cn的作用是通过每个桥臂输出电压逼近参考电压Vref_Ap～Vref_Cn，使得交流直接并网型电池储能***的三个相单元的交流端输出电压逼近交流端输出电压参考值ma×Vdcn/2、mb×Vdcn/2、mc×Vdcn/2。
S30，根据A、B、C相中上桥臂和/或下桥臂的参考电压，计算A、B、C相中上桥臂和/或 下桥臂需投入的全电流控制电池模块数量，然后根据各桥臂需投入的全电流控制电池模块数量，对应控制各桥臂中全电流控制电池模块中的第一全控型电力电子器件，使各桥臂的输出电压与各桥臂的参考电压的差值在设定范围内，即使得各桥臂的输出电压对应与其参考电压逼近，从而实现交流直接并网型电池储能***与外部交流***的功率变换。
在步骤S30中，计算A、B、C相中上桥臂和/或下桥臂需投入的全电流控制电池模块数量的公式为：
NAp＝ROUND(Vref_Ap/Vcn)
NAn＝ROUND(Vref_An/Vcn)
NBp＝ROUND(Vref_Bp/Vcn)
NBn＝ROUND(Vref_Bn/Vcn)
NCp＝ROUND(Vref_Cp/Vcn)
NCn＝ROUND(Vref_Cn/Vcn)
式中，NAp表示A相中上桥臂投入的全电流控制电池模块数量；NAn表示A相中下桥臂投入的全电流控制电池模块数量；NBp表示B相中上桥臂投入的全电流控制电池模块数量；NBn表示B相中下桥臂投入的全电流控制电池模块数量；NCp表示C相中上桥臂投入的全电流控制电池模块数量；NCn表示C相中下桥臂投入的全电流控制电池模块数量；ROUND表示四舍五入取整函数；Vcn表示储能电容的额定电压值。
本实施例提供的交流直接并网型电池储能***的功率变换方法，通过在各电池模块中增设一全电流控制电池模块，并通过对其进行相应控制，可实现电池储能***与交流***之间的交流/直流功率变换，相比于传统并网电池储能***，可省去其中的功率变换***，大大降低***成本；同时，由于省去了功率变换***，从而省去了功率变换***对应的损耗，使得所提供的交流直接并网型电池储能***的损耗更低。
在一个实施例中，为确保储能***向交流***输出的有功功率与电池储能***放电功率的平衡，本发明提供的全电流控制电池模块D还包括电流控制单元，如图16所示，电流控制单元采用6个由第二全控型电力电子器件(Q9a、Q9b、Q9c、Q10a、Q10b、Q10c)组成的三相全桥电路，各全电流控制电池模块中三相全桥电路的两输入端对应与该全电流控制电池模块中储能电容的两端相连，各全电流控制电池模块中三相全桥电路的每相交流输出端均对应通过一电感分别与一电池模块E相连。对应地，本发明提供的功率变换方法还设置了平均电容电压控制以及电感电流控制，如图6所示，具体为：
步骤1：测量并获取各个桥臂中的所有全电流控制电池模块的储能电容C的电压vci k和其中电感的电流Idis。
其中，当每个储能模块均包括A、B、C三个由上桥臂和下桥臂组成的相单元时，k的取值为1～6，对应A、B、C三个相单元共计6个桥臂；同理可知，当每个储能模块均包括A、B、C三个由上桥臂或下桥臂组成的相单元时，k的取值范围，本实施例不再赘述。i的取值范围为1～N，N为各桥臂全电流控制电池模块的总数，比如对于A相上桥臂，则N与NAp的关系为：N≥NAp；对于A相下桥臂，则N与NAn的关系为：N≥NAn；对于B相上桥臂，则N与NBp的关系为：N≥NBp；对于B相下桥臂，则N与NBn的关系为：N≥NBn；对于C相上桥臂，则N与NCp的关系为：N≥NCp；对于C相下桥臂，则N与NCn的关系为：N≥NCn。
步骤2：将各个桥臂中的所有全电流控制电池模块中储能电容的电压vci k求平均值 后，除以(6*N)后，得到各桥臂中储能电容电压平均值Vcavg后，该电压平均值Vcavg再与储能电容平均电容电压的参考值Vcref进行作差比较，经比例积分控制器PI后，得到各电池模块的放电电流指令Iord。同理可知，当每个储能模块均包括A、B、C三个由上桥臂或下桥臂组成的相单元时，获取各电池模块放电电流指令的控制原理，本实施例不再赘述。
步骤3：将各电池模块的放电电流指令Iord分别与对应的各全电流控制电池模块中电感的电流Idis作差比较后，经比例-积分控制器或电流滞环控制器闭环控制后，得到各全电流控制电池模块中6个第二全控型电力电子器件的占空比信号，对应控制各全电流控制电池模块中的6个第二全控型电力电子器件开通/关断状态，从而对各全电流控制电池模块中电感的电流进行闭环控制，保持交流直接并网型电池储能***向外部交流***输出的有功功率与全电流控制电池模块放电功率的平衡。
本实施例以投入的所有全电流控制电池模块中储能电容的电压平均值作为表征储能***交流有功功率与储能***电池模块放电能量之间的平衡。当电池储能***对交流***的放电功率增大时，储能电容的电压平均值会降低，通过本发明提供的平均电容电压控制可提高电池模块放电电流指令值Iord，以增大电池模块的放电能量，从而补充储能电容因对交流***放电而产生的电压下降。当电池储能***对交流***的放电功率减小时，储能电容的电压平均值会升高，可通过本发明提供的平均电容电压控制可将降低电池模块放电电流指令值Iord，以减小电池模块的放电能量，从而吸收储能电容因降低对交流***放电而产生的电压上升。
在一个实施例中，各储能模块10中三个相单元的交流端通过交流变压器分别对应与外部交流***的A、B、C三相端相连，可灵活匹配外部交流***不同的电压等级。
在一个实施例中，每个相单元可采用3个桥臂组成，3个桥臂的组合形式包括3个上桥臂的组合或3个下桥臂的组合。相比于各相单元采用2个桥臂的结构形式，可更加方便地配置储能***对应的储能模块数。
在一个实施例中，本发明提供的交流直接并网型电池储能***还可包括冗余相单元，该冗余相单元的拓扑结构与储能模块中的相单元拓扑结构相同，冗余相单元的交流端与3个单相交流断路器的一端相连，3个单相交流断路器的另一端分别对应与外部交流***的A、B、C三相端相连；且各储能模块中三个相单元的交流端均通过交流断路器分别对应与外部交流***的A、B、C三相端相连。
在本实施例中，当交流直接并网型储能***的A、B或C相任意一个相单元发生故障，通过合闸对应的A相、B相或C相单相交流断路器，可将冗余相单元联接到对应的外部交流***，从而实现储能***相单元的冗余备份，避免单一相单元故障导致储能模块不可运行。
以下结合具体实施例，对本发明提供的交流直接并网型电池储能***和其控制策略(功率变换方法)进行相应说明：
图7是本发明一具体实施例提供的交流直接并网型电池储能***的电路原理图，如图7所示，该电池储能***包括1个储能模块，该储能模块由三个相单元11构成，每个相单元11由上桥臂11a以及下桥臂11b串联而成，各个上桥臂11a的高压端连接在一起，构成该储能模块10的正极直流母线H+，各个下桥臂11b的低压端连接在一起，构成该储能模块10的负极直流母线L-，每个相单元11中上桥臂与下桥臂的共接点处构成该相单元的交流输出端， 三个相单元的交流输出端对应与外部交流***的A、B、C三相端相接，且每个上桥臂以及下桥臂均由多个全控制型电池模块串联后再与电抗器L串联而成，各全控制型电池模块均包括一全电流控制电池模块D和一电池模块E。
图7实施例中，每个相单元11由上桥臂11a及下桥臂11b串联而成，每个上桥臂11a由N个全控制型电池模块与电抗器L串联而成，各全控制型电池模块均包括一全电流控制电池模块D和一电池模块E。其中，第1个全电流控制电池模块的高压端为上桥臂11a的高压端，第1个全电流控制电池模块的低压端与第2个全电流控制电池模块的高压端相连接，依次类推，第N-1个全电流控制电池模块的低压端与第N个全电流控制电池模块的高压端相连接，第N个全电流控制电池模块的低压端与上桥臂的电抗器L的一端相连接，上桥臂的电抗器L的另一端与下桥臂11b的电抗器的一端相连接。下桥臂的电抗器的另一端与下桥臂中第1个全电流控制电池模块的高压端相连接，下桥臂中第1个全电流控制电池模块的低压端与下桥臂中第2个全电流控制电池模块的高压端相连接，依次类推，下桥臂中第N-1个全电流控制电池模块的低压端与下桥臂中第N个全电流控制电池模块的高压端相连接，下桥臂中第N个全电流控制电池模块的低压端构成下桥臂11b的低压端。
图8与图7实施例类似，区别在于，每个相单元11的上桥臂11a的高压端为上电抗器L的一端，上电抗器L的另一端与上桥臂第1个全电流控制电池模块的高压端相连接，上桥臂第1个全电流控制电池模块的低压端与第2个全电流控制电池模块的高压端相连接，依次类推，第N-1个全电流控制电池模块的低压端与第N个全电流控制电池模块的高压端相连接，第N个全电流控制电池模块的低压端与下桥臂11b中第1个全电流控制电池模块的高压端相连接。下桥臂11b中第1个全电流控制电池模块的低压端与下桥臂中第2个全电流控制电池模块的高压端相连接，依次类推，下桥臂11b第N-1个全电流控制电池模块的低压端与下桥臂11b第N个全电流控制电池模块1的高压端相连接，下桥臂11b中第N个全电流控制电池模块1的低压端与下桥臂电抗器的一端相连接，下桥臂电抗器的另一端构成下桥臂11b的低压端。
图9与图7实施例类似，区别在于，储能模块10经交流断路器连接到外部交流***的A、B、C三相端上，且储能***还额外配置了一个相单元，称该相单元为冗余相单元12，冗余相单元12的高压端与正极直流母线H+相连接，冗余相单元12的低压端与负极直流母线L-相连接，冗余相单元12的交流输出端与三个单相交流断路器的一端相连接，三个单相交流断路器的另一端对应与外部交流***的A、B、C三相端连接。
当交流直接并网型电池储能***的A、B或C相任意一个相单元发生故障，即在发生下行通讯故障、下行通讯故障、电池模块内单体电芯过温，电力电子器件过温时，判断全电流控制电池模块处于故障状态，一个相单元中处于故障状态的全电流控制电池模块数目超出冗余的全电流控制电池模块数目时，判断相单元处于故障状态，通过合闸对应的A、B或C相中单相交流断路器，可以将冗余相单元12连接到对应的外部交流***，从而实现储能***相单元的冗余备份，避免单一相单元故障导致储能模块不可运行。
当图9实施例提供的交流直接并网型电池储能***包括多个储能模块10时，本实施例提供的冗余相单元12还可以方便地实现各储能模块10的不停机在线运维，当某个储能模块10的上桥臂11a或下桥臂11b故障，导致储能模块10的一个相单元11故障不可继续运行时，可将冗余相单元12投入运行，取代储能模块10发生故障的相单元，使得发生了相单元故 障的储能模块10仍能维持不间断运行，而后对发生了故障的相单元进行在线检修与维护。具体实现方式为：将该故障的储能模块10闭锁，而后将冗余相单元12的X相(例如A相)的单相交流断路器合闸，而后将冗余相单元12及故障储能模块的非故障相作为一个新的储能模块进行整体控制，解锁该新的储能模块。
图10实施例为图9实施例的进一步改进，各相单元的交流输出端经过交流变压器与外部交流***相连接，从而可以灵活匹配外部交流***不同的电压等级。
为了提高单套交流直接并网型储能***的能量，每个交流直接并网型储能***中可包含2个及2个以上的储能模块10，各个储能模块10的正极直流母线不相互连接，各个储能模块10的负极直流母线也不相互连接，从而可避免各个储能模块10在直流侧相互耦合。图11实施例中，单套交流直接并网型储能***共包含2个储能模块10。
图12实施例与图11实施例类似，区别在于，图12实施例中，各个储能模块10的正极直流母线H+相互连接在一起，各个储能模块10的负极直流母线L-也相互连接在一起，从而使得储能模块10的正极直流母线以及负极直流母线可以对外进一步连接外部直流***。
图13实施例中，每个储能模块由三个相单元构成，每个相单元11均由1个上桥臂构成，每个上桥臂由N个全控制型电池模块和一个电抗器L串联而成，各全控制型电池模块均包括一全电流控制电池模块D和一电池模块E。其中，第1个全电流控制电池模块的高压端为上桥臂的高压端，第1个全电流控制电池模块的低压端与第2个全电流控制电池模块的高压端相连接，依次类推，第N-1个全电流控制电池模块的低压端与第N个全电流控制电池模块的高压端相连接，第N个全电流控制电池模块1的低压端与上桥臂的电抗器L的一端相连接，上桥臂的电抗器L的另一端与外部交流***的A、B或C三相端连接。
图14为图7实施例与图13实施例技术路线的组合，由图7所示的由三个相单元11构成的完整储能模块10与由3个下桥臂11b构成的储能模块10的组合。3个下桥臂11b构成的储能模块的交流输出与三个相单元11构成的储能模块的交流输出连接在一起，并与外部交流***的A、B、C三相端连接。图14的优势在于，每个储能***的最小可分割单元是3个桥臂，从而方便地根据需要配置储能***对应的储能模块数。
图15是图13拓扑的另外一种实现形式，该储能***由包含2个储能模块，每个储能模块均由3个下桥臂11b构成。
图16示例了所述全电流控制电池模块的一种实现拓扑，由全控型电力电子器件Q1、Q2、Q9a、Q9b、Q9c、Q10a、Q10b、Q10c，储能电容C，电感La、Lb、Lc，续流二极管D以及电池模块E构成，各全控型电力电子器件均采用1个晶体管及与其反并联的二极管，各电池模块E采用12～24节单体电池串联而成。
全控型电力电子器件Q1和Q2串联后与储能电容C并联，当Q1开通且Q2关断时，电容C与交流***相连接，可以从交流***吸取交流电流或者将交流电流注入到交流***；当Q2开通且Q1关断时，全电流控制电池模块被Q2旁路，电容C既不从交流***吸取交流电流，也不释放交流电流至交流***。
Q9a、Q10a、La，Q9b、Q10b、Lb，Q9c、Q1c、Lc则构成连接电容C与电池模块E的3组能量传输通道。以Q9a、Q10a、La为例，当需要给电池模块E充电时，维持Q10a始终处于关断状态，通过开通Q9a则电容C通过Q9a、La给电池模块E充电，将Q9a关断时，则La上的电流经La、电池模块E、及Q10a的反并联二极管形成续流回路，电容C不再给电池模块E充电。当电池模块E需 要放电时，仍以Q9a、Q10a、La为例，维持Q9a处于关断状态，通过开通Q10a，则电池模块E经La、Q10a，形成通流回路，电感La的电流被增加，电池模块E放电，关断Q10a时，电感La上的电流经La、Q9a的反并联二极管、电容C、电池模块E形成续流回路，电感La以及电池模块E给电容C放电。
以上述图7实施例提供的交流直接并网型电池储能***采用图16所示的全电流控制电池模块电路为例，对其功率变换方法进行说明。
图7的每个桥臂由多个全控型电池模块串联而成，记每个全控型电池模块的电容C电压为Uc，开通全控型电池模块的Q1、关断Q2时，全控型电池模块处于投入状态，全控型电池模块的输出电压为Uc，开通全控型电池模块的Q2、关断Q1时，全控型电池模块处于切除状态，全控型电池模块的输出电压为0。根据图5储能***的控制，得到每个桥臂的参考电压Vref_Ap、Vref_An、Vref_Bp、Vref_Bn、Vref_Cp、Vref_cn后，记电容电压的额定值为Vcn，每个桥臂(以A相上桥臂为例)投入的全控型电池模块个数为ROUND(Vref_Ap/Vcn)时(其中，ROUND为四舍五入取整函数)，每个桥臂的输出电压即能逼近其参考电压。以A相为例，根据本领域公知的基尔霍夫电压定律，A相输出等效交流电压为(Vref_An-Vref_Ap)/2，调节Vref_An，Vref_Ap的大小即可调节A相等效输出交流电压的大小，从而控制A相与外部交流***交换的功率。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (9)

  1. 一种交流直接并网型电池储能***的功率变换方法，其特征在于，所述交流直接并网型电池储能***包括若干个储能模块，每个储能模块均包括A、B、C三个由上桥臂和/或下桥臂组成的相单元，各桥臂均采用多个全控制型电池模块串联后再与电抗器串联而成；
    其中，当各相单元仅包括上桥臂时，各相单元中上桥臂的低压端构成该相单元的交流端，三个相单元的交流端分别对应与外部交流***的A、B、C三相端相连，各储能模块中的三个相单元中上桥臂的高压端共接构成该储能模块的正极直流母线H+；当各相单元仅包括下桥臂时，各相单元中下桥臂的高压端构成该相单元的交流端，三个相单元的交流端对应与外部交流***的A、B、C三相端相连，各储能模块中的三个相单元中下桥臂的低压端共接构成该储能模块的负极直流母线L-；当各相单元11同时包括上桥臂和下桥臂时，各储能模块中所有上桥臂的高压端共接构成该储能模块的正极直流母线，各储能模块中所有下桥臂的低压端共接构成该储能模块的负极直流母线，每个相单元中上桥臂的低压端与下桥臂的高压端相连构成该相单元的交流端，三个相单元的交流端分别对应与外部交流***的A、B、C三相端相连；
    各全控制型电池模块均包括一全电流控制电池模块和一电池模块，全电流控制电池模块包括能量传输控制单元和中继能量单元，中继能量单元采用储能电容，储能电容与电池模块并联；能量传输控制单元采用多个第一全控型电力电子器件，用于实现储能电容与外部交流***的连通或断开；
    所述功率变换方法包括如下步骤：
    (1)获取并根据外部交流***A、B、C三相端的电压和电流，对应计算交流直接并网型电池储能***的有功功率实测值Pacpu和无功功率实测值Qacpu，然后根据有功功率实测值Pacpu、无功功率实测值Qacpu、有功功率参考值Pacref和无功功率参考值Qref，计算交流有功电流参考值Idref和交流无功电流参考值Iqref；
    (2)对参考值Idref和参考值Iqref进行闭环跟踪控制，得到交流调制比ma、mb、mc，然后根据交流调制比ma、mb、mc，计算A、B、C相中上桥臂和/或下桥臂参考电压；其中，计算A、B、C相中上桥臂和/或下桥臂的参考电压的公式为：
    Vref_Ap＝Vdcn/2-ma×Vdcn/2
    Vref_An＝Vdcn/2+ma×Vdcn/2
    Vref_Bp＝Vdcn/2-mb×Vdcn/2
    Vref_Bn＝Vdcn/2+mb×Vdcn/2
    Vref_Cp＝Vdcn/2-mc×Vdcn/2
    Vref_Cn＝Vdcn/2+mc×Vdcn/2
    式中，Vref_Ap表示A相中上桥臂的参考电压；Vref_An表示A相中下桥臂的参考电压；Vref_Bp表示B相中上桥臂的参考电压；Vref_Bn表示B相中下桥臂的参考电压；Vref_Cp表示C相中上桥臂的参考电压；Vref_Cn表示C相中下桥臂的参考电压；Vdcn表示正极直流母线对负极直流母线直流电压额定值；
    (3)根据A、B、C相中上桥臂和/或下桥臂参考电压，计算A、B、C相中上桥臂和/或下桥臂需投入的全电流控制电池模块数量，然后根据各桥臂需投入的全电流控制电池模块数量，对应控制各桥臂中全电流控制电池模块中的第一全控型电力电子器件，使各桥臂的输出电压对应与其参考电压的差值在设定范围内，从而实现交流直接并网型电池储能***与外部 交流***的功率变换。
  2. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，步骤(3)中，计算A、B、C相中上桥臂和/或下桥臂需投入的全电流控制电池模块数量的公式为：
    NAp＝ROUND(Vref_Ap/Vcn)
    NAn＝ROUND(Vref_An/Vcn)
    NBp＝ROUND(Vref_Bp/Vcn)
    NBn＝ROUND(Vref_Bn/Vcn)
    NCp＝ROUND(Vref_Cp/Vcn)
    NCn＝ROUND(Vref_Cn/Vcn)
    式中，NAp表示A相中上桥臂投入的全电流控制电池模块数量；NAn表示A相中下桥臂投入的全电流控制电池模块数量；NBp表示B相中上桥臂投入的全电流控制电池模块数量；NBn表示B相中下桥臂投入的全电流控制电池模块数量；NCp表示C相中上桥臂投入的全电流控制电池模块数量；NCn表示C相中下桥臂投入的全电流控制电池模块数量；ROUND表示四舍五入取整函数；Vcn表示所述储能电容的额定电压值。
  3. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，步骤(1)中，计算得到交流有功电流参考值Idref和交流无功电流参考值Iqref的步骤，具体为：
    将有功功率实测值Pacpu和有功功率参考值Pacref作差比较后，经比例积分调节后得到交流有功电流参考值Idref；将无功功率实测值Qpu与无功功率参考值Qref作差比较后，经比例积分调节后得到交流无功电流参考值Iqref。
  4. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，所述全电流控制电池模块还包括电流控制单元，所述电流控制单元采用6个由第二全控型电力电子器件组成的三相全桥电路，各全电流控制电池模块中三相全桥电路的两输入端对应与该全电流控制电池模块中储能电容的两端相连，各全电流控制电池模块中三相全桥电路的每相交流输出端均对应通过一电感分别与一电池模块相连；
    所述功率变换方法还包括如下步骤：
    获取各个桥臂中的所有全电流控制电池模块中储能电容的电压和其中电感的电流Idis；
    将各个桥臂中的所有全电流控制电池模块中储能电容的电压求平均值后，与所述储能电容平均电容电压的参考值VCref进行作差比较，将作差比较后得到的差值经比例积分调节后，得到各电池模块的放电电流指令Iord；
    将各电池模块的放电电流指令Iord分别与对应的各全电流控制电池模块中电感的电流Idis作差比较后，经比例-积分控制器或电流滞环控制器闭环控制后，得到各全电流控制电池模块中6个第二全控型电力电子器件的占空比信号，对应控制各全电流控制电池模块中的6个第二全控型电力电子器件开通/关断状态，从而对各全电流控制电池模块中电感的电流进行闭环控制，保持交流直接并网型电池储能***向外部交流***输出的有功功率与全电流控制电池模块放电功率的平衡。
  5. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，各储能模块中三个相单元的交流端通过交流变压器分别对应与外部交流***的A、B、C三相 端相连。
  6. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，每个相单元由3个桥臂组成，3个桥臂的组合形式包括3个上桥臂的组合或3个下桥臂的组合。
  7. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，所述交流直接并网型电池储能***还包括冗余相单元，所述冗余相单元的交流端与3个单相交流断路器的一端相连，3个单相交流断路器的另一端分别对应与外部交流***的A、B、C三相端相连；且各储能模块中三个相单元的交流端通过交流断路器分别对应与外部交流***的A、B、C三相端相连。
  8. 根据权利要求4所述的交流直接并网型电池储能***的功率变换方法，其特征在于，所述第一全控型电力电子器件和所述第二全控型电力电子器件均采用1个或多个晶体管及与其反并联的二极管；各电池模块采用12～24节单体电池串联而成。
  9. 根据权利要求1所述的交流直接并网型电池储能***的功率变换方法，其特征在于，所述全电流控制电池模块中的能量传输控制单元包括2个第一全控型电力电子器件，分别为全控型电力电子器件Q1和Q2，所述全控型电力电子器件Q1的低压端与所述全控型电力电子器件Q2的高压端相连，所述全控型电力电子器件Q1的高压端与所述储能电容的一端相连，所述全控型电力电子器件Q2的低压端与所述储能电容的另一端相连。
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