Multi-battery-pack bidirectional charging and discharging system supporting pulse charging and discharging and control method thereof

Abstract

A multi-battery bidirectional charging and discharging system supporting pulse charging and discharging and a control method thereof belong to the field of power electronics, and the bidirectional charging and discharging system comprises a power factor correction (PFC) stage composed of a three-phase bridge type full-control circuit, a direct current-direct current (DC-DC) converter stage and a plurality of switching device groups. The intermittent characteristic of the pulse charging current is utilized, different battery packs are charged and discharged reasonably and alternately by staggering the conduction interval of the pulse current, the current and voltage fluctuation of the alternating current power supply side in the energy flowing process can be reduced, and the influence of the system on the stability of a power grid or other power supplies is reduced. The invention supports pulse charging and discharging, and can reduce the polarization effect of the battery, prolong the service life of the battery, improve the charging efficiency, reduce hardware equipment required by charging and reduce the cost. The system allows bidirectional flow of energy between the alternating current side and the direct current side of the system, is controllable in power, supports V2G application, and can be used for a scene in which a battery is charged or discharged by using pulse current and continuous current.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging and a control method thereof. Background Art

[0002] Traditional lithium-ion battery charging methods include constant current charging, constant voltage charging, and constant voltage-constant current charging. The constant current charging method uses a constant current for charging, which is faster but may cause overcharging. Although the constant voltage charging method can avoid overcharging of the battery, the charging speed is slower. Compared with the constant current charging technology, the constant voltage charging technology can make the lithium battery almost fully charged and avoid overcharging, but it takes more time to complete the charging process and accelerates the attenuation of capacity. The constant voltage-constant current charging method combines the advantages of the previous two technologies and improves the charging speed while avoiding overcharging. During the charging process, the constant voltage-constant current charging technology keeps the charging current of the lithium-ion battery constant until the preset voltage of the lithium-ion battery is reached, and then the charging voltage is kept constant, and the charging current decreases exponentially. When the current reaches the minimum value, the charging ends. In order to further improve the charging speed, a variety of charging methods have also emerged, such as multi-stage constant current-constant voltage charging, which consists of several constant current charging stages of different sizes, followed by a constant voltage charging stage to end the charging process. Unlike the multi-stage constant current-constant voltage charging technique, another method called pulse charging periodically interrupts the charging current.

[0003] In addition to the above charging methods, pulse charging is a fast and efficient charging method that charges the battery in an intermittent manner. The short pause in each cycle provides a relaxation that helps eliminate concentration polarization and increase the power transfer rate, thereby reducing the change time. Due to the relaxation process set during charging, this technology can delay the capacity decay of the battery. In a cycle T, the battery is first charged with a large current for a charging time of t on , then stop charging, stop time t off Compared with traditional charging methods, this method can reduce the polarization effect of the battery, extend the battery life, improve the charging efficiency, and is suitable for high-power charging application scenarios.

[0004] On the other hand, with the widespread popularity of electrochemical energy storage systems and electric vehicles, the installed capacity of lithium-ion batteries has also grown rapidly. At the same time, electric vehicles can also be regarded as energy storage systems, which can absorb electricity from the grid when the grid load is low, the electricity price is low, and the battery needs to be charged, and discharge back to the grid with the help of vehicle-to-grid (V2G) interaction technology when the grid load is high and the electricity price is high, thereby achieving peak shaving and valley filling and promoting the consumption of renewable energy. The sharp changes in pulse current and power will affect the terminal electrical stability of the charging system, which is crucial for the safe and stable operation of the grid or other power sources. When a photovoltaic power generation system is used to charge a battery, in order to make the photovoltaic panel smoothly track the maximum power point, the literature [[1] H.-I. Hsieh, C.-Y. Tsai and G.-C. Hsieh, "Photovoltaic Burp Charge System on Energy-Saving Configuration by Smart Charge Management," in IEEE Transactions on Power Electronics, vol. 29, no. 4, pp. 1777-1790, April 2014, doi: 10.1109 / TPEL.2013.2268943.] proposed a pulse charging circuit topology, in which two additional batteries are used to consume the output power of the photovoltaic system and the discharge power of the main battery when charging is interrupted. The interruption of the charging current in pulse charging provides the possibility of regulating the charging current when multiple batteries are charged simultaneously and properly coordinated. However, this system requires the use of two additional smaller batteries for assistance, and it is impossible to achieve bidirectional energy flow between the AC side and the DC side of the system. Reference [2] Zhenhua Jiang and RA Dougal, "Synergetic control of power converters for pulse current charging of advanced batteries from a fuel cell power source," in IEEE Transactions on Power Electronics, vol. 19, no. 4, pp. 1140-1150, July 2004, doi: 10.1109 / TPEL.2004.830044.] proposed a technical solution for controlling the pulse current of a fuel cell by adjusting a step-down chopper converter. This solution uses a multi-cell battery cooperative charging method to avoid drastic changes in the output power of the fuel cell.The literature [[3] KSVenkat, MVSatya Sai Chandra and S.Mohapatro,"Pulse Charging Scheme for Multiple Battery Charging in Electric Vehicle Applications,"2023IEEE 3rd International Conference on Smart Technologies for Power, Energy and Control (STPEC), Bhubaneswar, India, 2023, pp. 1-6, doi: 10.1109 / STPEC59253.2023.10431359.] proposes a DC charging system that uses pulse charging to continuously charge two batteries, which can reduce the size and variation of the total battery charging current. In order to reduce the number and complexity of chargers, the reference [[4]P.-J.Liu and C.-H.Yen,"AFast-Charging Switching-BasedChargerWithAdaptive Hybrid Duty Cycle Control for Multiple Batteries,"in IEEE Transactions on Power Electronics,vol.32,no.3,pp.1975-1983,March 2017,doi:10.1109 / TPEL.2016.2555998.] proposed a circuit topology and control scheme. By charging the batteries alternately, the number of chargers required can also be reduced. However, the schemes proposed in references [2], [3] and [4] do not consider the energy conversion between the AC system and the DC system, and only support the unidirectional flow of energy from the DC power source to the battery, which does not support V2G applications. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of voltage and current fluctuations caused to the power grid or other power sources when a pulse charging current is used to charge or discharge a battery in the prior art, thereby providing a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging and a control method thereof.

[0006] The present invention provides a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging and a control method thereof, which can realize the bidirectional flow of energy between the power supply side and the battery side, while reducing the hardware equipment required for charging multiple battery packs, thereby reducing the cost of charging facilities.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0008] The present invention provides a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, comprising: a harmonic filter stage, a power factor correction (Power Factor Correction, PFC) stage, a direct current-to-direct current (DC-DC) converter stage and a plurality of switch device groups; the harmonic filter stage is composed of a group of inductors; the power factor correction stage is composed of a three-phase bridge full-control circuit and a filter capacitor in parallel; the DC-DC converter stage is composed of a phase-shifted full-bridge circuit, which includes a first single-phase bridge full-control circuit, an isolation transformer and a second single-phase bridge full-control circuit; the AC side of the power factor correction stage is connected to a power grid, an AC power supply or an AC load, the DC side of the power factor correction stage is connected to the DC-DC converter stage, the first single-phase bridge full-control circuit of the DC-DC converter stage is connected in series with the isolation transformer, the other side of the isolation transformer is connected to the second single-phase bridge full-control circuit, the second single-phase bridge full-control circuit is connected to the capacitor C B After being connected in parallel, they are connected to a plurality of switch device groups, and each switch device group is connected in series with a battery group;

[0009] When the battery pack is charged, the three-phase bridge-type full-controlled circuit of the power factor correction stage works in a rectifying state, responsible for rectifying the AC power on the AC side into DC power, filtering some harmonics through the filter capacitor, and stabilizing the DC side voltage at the same time; the first single-phase bridge-type full-controlled circuit of the DC-DC converter stage inverts the voltage on the DC side into industrial frequency or high-frequency AC power and then inputs it into the primary side of the isolation transformer; the isolation transformer is used to achieve electrical isolation and improve system safety; the second single-phase bridge-type full-controlled circuit of the DC-DC converter stage rectifies the AC power output from the secondary side of the isolation transformer into DC power, and then transmits the electric energy to the battery pack through multiple switch device groups, completing the transmission of electric energy from the power grid or AC load to the battery pack;

[0010] When the battery pack discharges to the system AC side power grid or AC load, the electric energy flows from the battery pack through multiple switching device groups to the second single-phase bridge full-controlled circuit of the DC-DC converter stage, which inverts the AC power output by the battery pack into industrial frequency or high-frequency AC power and then inputs it into the secondary side of the isolation transformer; the AC power output by the primary side of the isolation transformer is then rectified into DC power by the first single-phase bridge full-controlled circuit of the DC-DC converter stage and transmitted to the three-phase bridge full-controlled circuit of the power factor correction stage. At this time, the three-phase bridge full-controlled circuit works in the inverter state, which inverts the DC power on the DC side into industrial frequency AC power and transmits it to the power grid or AC load, completing the transmission of electric energy from the battery pack to the power grid or AC load.

[0011] Furthermore, the three-phase bridge full-control circuit is composed of a switch T 1 ~T6 composition.

[0012] Furthermore, the first single-phase bridge full-control circuit of the DC-DC converter stage is composed of a switch T 7 ~T 10 composition.

[0013] Furthermore, the second single-phase bridge full-control circuit of the DC-DC converter stage is composed of a switch T 11 ~T 14 composition.

[0014] Furthermore, the n switch groups are denoted as T B1 、T B2 ,…,T Bn , switch group T B1 By switch T C1 and switch T D1 Composition, switch group T B2 By switch T C2 and switch T D2 Composition, ..., switch group T Bn By switch T Cn and switch T Dn Composition, where n is a positive integer.

[0015] Furthermore, the switch T 1 ~T 14 It is any power electronic switch that meets the technical requirements, specifically but not limited to a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT).

[0016] The present invention provides a control system for a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, comprising:

[0017] The AC side power controller is used to realize the active and reactive power control of the AC side of the multi-battery bidirectional charging and discharging system. Specifically, the three-phase AC voltage and current of the AC system are converted into the corresponding direct axis voltage v in the dq domain. d , quadrature axis voltage v q and the direct axis current i d , quadrature axis current i q , and then control the target value i of the direct-axis current according to the output of the reference current calculator d,ref and the quadrature axis current control target value i q,ref , calculate the switch T 1 ~T 6 The three-phase bridge type full-control circuit consists of switches T in each bridge arm 1 ~T 6 The gate control signal G 1 ~G 6 , thereby controlling the switch T1 ~T 6 The three-phase bridge full-control circuit is composed to work;

[0018] The DC side power controller is used to realize the DC side power control of the multi-battery bidirectional charging and discharging system. Specifically, the DC side power controller receives the real-time power value P of the DC side measured by the DC side power meter. DC And the DC power control target value P DC,ref , using the proportional-integral-derivative (PID) controller to control the active power control target value P output by the AC side power controller s,ref , and output it to the reference current calculator;

[0019] The DC-DC converter stage controller is used to control the switch T 7 ~T 10 The first single-phase bridge fully controlled circuit consisting of an isolation transformer and a switch T 11 ~T 14 The second single-phase bridge full-control circuit is composed of the output of each bridge arm switch T 7 ~T 14 The gate control signal G 7 ~G 14 , realize DC-AC-DC conversion, so as to meet the working conditions of the isolation transformer;

[0020] The battery pack controller is used to control each battery pack B 1 , B 2 , …, B n Working state, output control signal G C1 , G C2 , …, G Cn For control switch T C1 , T C2 ,…,T Cn and control signal G D1 , G D2 , …, G Dn For control switch T D1 , T D2 ,…,T Dn ; For battery pack i∈[1,n], when switch T Ci When turned on, battery pack B i Charging; when switch T Di When turned on, battery pack B i Discharge; and switch T Ci and switch T Di Cannot be turned on at the same time;

[0021] The reference current calculator is used to receive the active power control target value P output by the DC side power controller. s,refAnd reactive power control target value Q AC,ref , according to the two, the quadrature axis current control target value i in the dq domain is calculated d,ref and the quadrature axis current control target value i q,ref and output it to the AC side power controller;

[0022] The DC power meter is used to measure the real-time power value P of the DC side. DC And output to the DC side power controller.

[0023] The present invention provides a control method for a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, comprising the following steps:

[0024] (1) DC side power control of multi-battery bidirectional charging and discharging system;

[0025] Set the DC power output or input of the system DC side, that is, the target power P DC,ref , when P DC,ref >0, the multi-battery bidirectional charging and discharging system works in the charging mode, the battery pack is charged, let F = -1; when P DC,ref <0, the multi-battery bidirectional charging and discharging system works in the discharge mode, the battery pack is discharged, let F = 1; adopt closed-loop negative feedback control to control the DC power target value P DC,ref The actual DC power P DC The difference is compared and multiplied by F after passing through the proportional-integral-derivative (PID) controller. s,ref As the active power control target value of the AC side power controller, F is a control factor used to change the active power control target value P output by the controller. s,ref Symbols;

[0026] (2) AC side power control of multi-battery bidirectional charging and discharging system;

[0027] If you need to control the DC side power P of a multi-battery bidirectional charging and discharging system DC , the current control target value i in the dq domain d,ref The active power control target value P s,ref Calculate as follows:

[0028]

[0029] If it is necessary to control the AC side power P of a multi-battery bidirectional charging and discharging system AC , the current control target value i in the dq domain d,ref The active power control target value P AC,ref Calculate as follows:

[0030]

[0031] Current control target value i in dq domain q,ref The reactive power control target value Q AC,ref Calculate as follows:

[0032]

[0033] Then the controlled variable AC side voltage v abc and the AC side current i abc Perform Park transformation into voltage v in dq domain dq and current i dq :

[0034] v dq =Pv abc #(4)

[0035] i dq =Pi abc #(5)

[0036] in:

[0037] v dq =[v d v q ] T #(6)

[0038] i dq =[i d i q ] T #(7)

[0039] v abc =[v a v b v c ] T #(8)

[0040] i abc =[i a i b i c ] T #(9)

[0041]

[0042] Where ω represents the angular frequency of the AC system on the AC side of the charging system, t represents time, and v a Indicates the phase voltage of phase A of the AC system, v b Indicates the phase voltage of phase B of the AC system, v c Indicates the phase voltage of phase C of the AC system, v d represents the direct axis voltage in the dq domain, v q represents the quadrature axis voltage in the dq domain, ia Indicates the phase current of phase A of the AC system, i b Indicates the phase current of phase B of the AC system, i c represents the phase current of phase C of the AC system, i d represents the direct axis current in the dq domain, i q represents the quadrature-axis current in the dq domain, and the superscript T indicates transposition;

[0043] On the direct axis, the current control target value i in the dq domain is d,ref with i d The direct-axis proportional-integral-differential (PID) controller is used to control the difference and the output u of the direct-axis proportional-integral-differential (PID) controller is c,d With v d and ωLi q Calculate u together as follows d :

[0044] u d =u c,d +v d -ωLi q #(11)

[0045] Among them, ωLi q represents the voltage drop component of the inductor L on the d-axis, u d It represents the component of the output voltage of the three-phase fully controlled bridge circuit on the d-axis;

[0046] On the quadrature axis, the current control target value i in the dq domain is q,ref with i q For comparison, the difference is controlled by using a PID controller, and the output u c,q With v q and ωLi d Calculate u together as follows q :

[0047] u q =u c,q +v q +ωLi d #(12)

[0048] Among them, ωLi d represents the component of the voltage drop of the inductor L on the q axis, u q It represents the component of the output voltage of the three-phase fully controlled bridge circuit on the q axis;

[0049] Get u d and u q Then, divide the values ​​by the DC voltage v DChalf of the modulation signal m in the dq domain dq =[m d m q ] T , m d 、m q Respectively represent m dq The components on the d and q axes are then subjected to inverse Park transformation to obtain the three-phase reference voltage v abc,ref :

[0050]

[0051] in:

[0052]

[0053] (3) Alternating conduction control of battery packs;

[0054] Assume battery pack B i The charging or discharging voltage is U i , the charging or discharging current is I i , the charging or discharging power is P i , the pulse duty cycle is d i , the instantaneous charging or discharging power of the multi-battery bidirectional charging and discharging system is P s , where i∈[1,n], the above variables should satisfy the following relationship:

[0055] P i =U i I i d i =P s d i #(15)

[0056] By adjusting the pulse duty cycle d i Adjustable battery pack B i The average charging or discharging power P i , while not changing the instantaneous charging or discharging power P of the multi-battery bidirectional charging and discharging system s .

[0057] Furthermore, in step (2), the three-phase reference voltage v is obtained. abc,ref After that, it is used as a modulation signal and a pulse width modulation (PWM) algorithm is used to obtain the switching T 1 ~T 6 The three-phase bridge type full-control circuit consists of switches T in each bridge arm 1 ~T 6 The gate control signal G 1 ~G 6 .

[0058] Furthermore, in step (3), the conduction intervals of the n battery packs connected to the multi-battery pack bidirectional charge and discharge system within a period T should be staggered, and the sum of the conduction intervals is equal to an integer multiple of the period, that is:

[0059]

[0060] Furthermore, in step (4), when it is necessary to adjust the charging or discharging power of any one of the battery packs, the pulse duty cycle of one of the battery packs can be adjusted, while the pulse duty cycle of the other battery pack can be adjusted inversely.

[0061] The beneficial effects of the present invention are:

[0062] The present invention utilizes the intermittent characteristics of the pulse charging current, staggers the conduction interval of the pulse current, and reasonably alternately conducts different batteries, which can reduce the current and voltage fluctuations on the AC power supply side during the energy flow process and reduce the impact of the system on the stability of the power grid or other power sources. Due to the support of pulse charging and discharging technology, the present invention can reduce the polarization effect of the battery, extend the service life of the battery, and improve the charging efficiency. The present invention can reduce the hardware equipment required to charge multiple battery packs and reduce the cost of charging facilities. In addition, the present invention allows energy to flow bidirectionally between the AC side and the DC side of the system, and the power is controllable. Only one set of current conversion and control devices is used to realize the simultaneous charging or discharging of multiple battery packs, so V2G applications can be supported. It is worth noting that the present invention is not limited to applications where pulse currents are used to charge or discharge batteries, but can also be used in application scenarios where continuous currents are used to charge or discharge battery packs.

[0063] In addition, the present invention also proposes a control method for a multi-battery bidirectional charging and discharging system that supports pulse charging and discharging, which can control the bidirectional flow of energy between the battery pack and the AC power supply, while reducing the current and voltage fluctuations on the AC power supply side during the energy flow, thereby reducing the impact of the system on the stability of the power grid or other power sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 A circuit topology diagram of a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging provided by the present invention.

[0065] Figure 2 This is the control system structure diagram of the bidirectional charging and discharging system.

[0066] Figure 3 This is the block diagram of the DC side power controller system.

[0067] Figure 4 This is the block diagram of the AC side power controller system.

[0068] Figure 5 For battery pack B1 Charging voltage and current curve.

[0069] Figure 6 For battery pack B 2 Charging voltage and current curve.

[0070] Figure 7 is the power curve of the system AC side.

[0071] Figure 8 is the power curve of the system DC side.

[0072] Fig. 9 is the current curve of the system AC side.

[0073] Fig.10 is the voltage curve of the DC side of the system.

[0074] Fig.11 For battery pack B 1 Discharge voltage and current curve.

[0075] Fig.12 For battery pack B 2 Discharge voltage and current curve.

[0076] Fig.13 is the power curve of the system AC side.

[0077] Fig.14 is the power curve of the system DC side.

[0078] Fig.15 is the current curve of the system AC side.

[0079] Fig.16 is the voltage curve of the DC side of the system.

[0080] Fig.17 For battery pack B 1 Charging voltage and current curve.

[0081] Fig.18 For battery pack B 2 Charging voltage and current curve.

[0082] Fig.19 is the power curve of the system DC side.

[0083] Fig. 20 is the power curve of the system AC side.

[0084] Fig.21 is the current curve of the system AC side.

[0085] Fig. 22 is the voltage curve of the DC side of the system.

[0086] Fig.23For battery pack B 1 Charging voltage and current curve.

[0087] Fig.24 For battery pack B 2 Charging voltage and current curve.

[0088] Fig.25 is the power curve of the system AC side.

[0089] Fig.26 is the power curve of the system DC side.

[0090] Fig. 27 is the current curve of the system AC side.

[0091] Fig.28 is the voltage curve of the DC side of the system. DETAILED DESCRIPTION

[0092] In a first aspect, the present invention provides a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging.

[0093] The present invention provides a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, and its circuit topology is as follows: Figure 1 shown. Figure 1 In the figure, L and R are the filter inductance and resistance of the series circuit between the charging and discharging system and the AC system, respectively. A bidirectional charging and discharging system for multiple battery packs supporting pulse charging and discharging of the present invention mainly includes: a harmonic filter stage, a power factor correction (Power Factor Correction, PFC) stage, a DC-DC (DC-DC) converter stage and multiple switch device groups; wherein the harmonic filter stage is composed of a group of inductors; the power factor correction stage is composed of a three-phase bridge full-control circuit and a filter capacitor in parallel; the DC-DC converter stage is composed of a phase-shifted full-bridge circuit, which includes a first single-phase bridge full-control circuit, an isolation transformer and a second single-phase bridge full-control circuit; the AC side of the power factor correction stage is connected to the power grid, AC power supply or AC load, the DC side of the power factor correction stage is connected to the DC-DC converter stage, the first single-phase bridge full-control circuit is connected in series with the isolation transformer, the other side of the isolation transformer is connected to the second single-phase bridge full-control circuit, the second single-phase bridge full-control circuit is connected to the capacitor C B After being connected in parallel, they are connected to multiple switch device groups, and each switch device group is connected in series with a battery group.

[0094] Specifically, the part of the system AC side connected to the AC power supply is a switch T 1 ~T 6 The three-phase bridge full-control circuit consists of a filter capacitor C connected in parallel on the DC side, and then a switch T 7 ~T 10The first single-phase bridge full-control circuit is connected in series with an isolation transformer, and the other side of the isolation transformer is connected through a switch T 11 ~T 14 The second single-phase bridge full-control circuit and the voltage stabilizing capacitor C B After being connected in parallel, they are connected to multiple switch groups, and each switch group is finally connected in series with a battery group. Ci and switch T Di In reverse parallel connection, the switch T 1 ~T 14 It can be any power electronic switch that meets the technical requirements, including but not limited to metal oxide semiconductor field effect transistor (MOSFET), insulated gate bipolar transistor (IGBT), etc. The device shown in the figure is only a specific embodiment of the present invention.

[0095] When the battery pack is charging, the switch T 1 ~T 6 The three-phase bridge full-control circuit composed of the above components works in the rectification state, responsible for rectifying the AC power on the AC side (such as the power grid or other AC power supply) into DC power; the filter capacitor C is responsible for filtering some harmonics and stabilizing the DC side voltage; the switch T 7 ~T 10 The first single-phase bridge full-control circuit composed of the DC side voltage is inverted into industrial frequency or high-frequency AC and then input into the primary side of the isolation transformer; the switch T 11 ~T 14 The second single-phase bridge full-control circuit rectifies the AC power output from the secondary side of the isolation transformer into DC power, and then transmits the power to the battery pack B through a set of switching devices. 1 , B 2 , …, B n Thus, the electric energy is transmitted from the power grid or other AC power source to the battery pack.

[0096] When the battery pack discharges to the AC side of the system (such as the power grid, AC load), the electric energy is discharged from the battery pack B 1 , B 2 , …, B n The current flows through the switch device to the switch T 11 ~T 14 The second single-phase bridge full-control circuit composed of the battery pack converts the AC power output into industrial frequency or high-frequency AC power and then inputs it into the secondary side of the isolation transformer; the AC power output from the primary side of the isolation transformer is then transmitted through the T 7 ~T 10 The single-phase bridge fully controlled circuit is rectified into DC power and transmitted to the switch T 1 ~T 6 The three-phase bridge full-control circuit is composed of switch T 1 ~T6 The three-phase bridge full-control circuit works in the inverter state, which inverts the DC power on the DC side into industrial frequency AC power and transmits it to the power grid or AC load. Thus, the electric energy is transmitted from the battery pack to the power grid or AC load.

[0097] In a second aspect, the present invention provides a control system for a multi-battery bidirectional charging and discharging system that supports pulse charging and discharging.

[0098] The present invention provides a control system for a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, and its structure is as follows: Figure 2 As shown, the control system mainly includes: an AC side power controller, a DC side power controller, a DC-DC conversion stage controller, a battery pack controller, a reference current calculator and a DC side power meter.

[0099] Since the energy in the multi-battery bidirectional charging and discharging system can flow bidirectionally between the AC side and the DC side, in order to facilitate the explanation of the working principle of its control system, this description defines: all AC power and DC power flowing out of the control system are positive values, and all AC power and DC power flowing into the control system are negative values.

[0100] The AC side power controller is mainly used to realize the active and reactive power control of the AC side of the multi-battery bidirectional charging and discharging system. Specifically, it converts the three-phase AC voltage and current of the AC system into the corresponding direct-axis voltage v in the dq domain. d , quadrature axis voltage v q and the direct axis current i d , quadrature axis current i q , and then control the target value i of the direct-axis current according to the output of the reference current calculator d,ref and the quadrature axis current control target value i q,ref , calculate the switch T 1 ~T 6 The three-phase bridge type full-control circuit consists of switches T in each bridge arm 1 ~T 6 The gate control signal G 1 ~G 6 , thereby controlling the switch T 1 ~T 6 The three-phase bridge full-control circuit is composed to work;

[0101] The DC side power controller is mainly used to realize the DC side power control of the multi-battery bidirectional charging and discharging system. Specifically, the DC side power controller receives the real-time power value P of the DC side measured by the DC side power meter. DC And the target power value P DC,ref , using the proportional-integral-derivative (PID) controller to control the active power control target value P output by the AC side power controller s,ref, and output it to the reference current calculator;

[0102] The DC-DC conversion stage controller is mainly used to control the switch T 7 ~T 10 The first single-phase bridge fully controlled circuit consisting of an isolation transformer and a switch T 11 ~T 14 The second single-phase bridge full-control circuit is composed of the output of each bridge arm switch T 7 ~T 14 The gate control signal G 7 ~G 14 , realize DC-AC-DC conversion, so as to meet the working conditions of the isolation transformer;

[0103] The battery pack controller is mainly used to control each battery pack B 1 , B 2 , …, B n Working state, output control signal G C1 , G C2 , …, G Cn For control switch T C1 、T C2 ,…,T Cn and control signal G D1 , G D2 , …, G Dn For control switch T D1 、T D2 ,…,T Dn ; For switch group i, when switch T Ci When turned on, battery pack B i Charging; when switch T Di When turned on, battery pack B i Discharge; and switch T Ci and switch T Di Cannot be turned on at the same time;

[0104] The reference current calculator is mainly used to receive the active power control target value P of the AC side power controller from the DC side power controller. s,ref And reactive power control target value Q AC,ref , according to the two, the quadrature axis current control target value i in the dq domain is calculated d,ref and the quadrature axis current control target value i q,ref and output it to the AC side power controller;

[0105] The DC power meter is mainly used to measure the real-time power P of the DC side. DC And output to the DC side power controller.

[0106] In a third aspect, the present invention provides a control method for a multi-battery bidirectional charging and discharging system that supports pulse charging and discharging.

[0107] The present invention provides a control method for a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, and the specific implementation process is as follows:

[0108] (1) DC side power control of multi-battery bidirectional charging and discharging system;

[0109] The working principle of the DC side power controller of the multi-battery bidirectional charging and discharging system is as follows Figure 3 When the power on the DC side needs to be controlled, the target power P needs to be set. DC,ref , which is the DC power output or input on the DC side of the system. DC,ref >0, the multi-battery bidirectional charging and discharging system works in the charging mode, the battery pack is charged, let F = -1; when P DC,ref <0, the multi-battery bidirectional charging and discharging system works in the discharge mode, the battery pack is discharged, and F=1. The control system adopts closed-loop feedback control to set the target power P DC,ref The actual DC power P DC The difference is compared and then multiplied by F after passing through the proportional-integral-derivative (PID) controller. F is a control factor used to change the active power control target value P output by the controller. s,ref The symbol of P s,ref As the active power control target value of the AC side power controller.

[0110] (2) AC side power control of multi-battery bidirectional charging and discharging system;

[0111] The AC side power control of the multi-battery bidirectional charging and discharging system is carried out in the dq domain. The working principle of the AC side power controller is as follows: Figure 4 shown.

[0112] If it is necessary to control the DC side power P of a multi-battery bidirectional charging and discharging system DC , the current control target value i in the dq domain d,ref The active power control target value P s,ref Calculate as follows:

[0113]

[0114] If it is necessary to control the AC side power P of a multi-battery bidirectional charging and discharging system AC , the current control target value i in the dq domain d,ref The active power control target value P AC,ref Calculate as follows:

[0115]

[0116] Current control target value i in dq domain q,ref The reactive power control target value Q AC,ref Calculate as follows:

[0117]

[0118] Then, the controlled variable AC side voltage vector v abc and the AC side current vector i abc Perform Park transformation into voltage vector v in dq domain dq and the current vector i dq :

[0119] v dq =Pv abc #(20)

[0120] i dq =Pi abc #(twenty one)

[0121] in:

[0122] v dq =[v d v q ] T #(twenty two)

[0123] i dq =[i d i q ] T #(twenty three)

[0124] v abc =[v a v b v c ] T #(twenty four)

[0125] i abc =[i a i b i c ] T #(25)

[0126]

[0127] Where ω represents the angular frequency of the AC system on the AC side of the charging system, t represents time, and v a Indicates the phase voltage of phase A of the AC system, v b Indicates the phase voltage of phase B of the AC system, v c Indicates the phase voltage of phase C of the AC system, v d represents the direct axis voltage in the dq domain, vq represents the quadrature axis voltage in the dq domain, i a Indicates the phase current of phase A of the AC system, i b Indicates the phase current of phase B of the AC system, i c represents the phase current of phase C of the AC system, i d represents the direct axis current in the dq domain, i q It represents the quadrature-axis current in the dq domain, and the superscript T represents the transpose.

[0128] On the direct axis (d axis), the current control target value i in the dq domain is d,ref with i d The direct-axis proportional-integral-differential (PID) controller is used to control the difference and the output u of the direct-axis proportional-integral-differential (PID) controller is c,d With v d and ωLi q Calculate u together as follows d :

[0129] u d =u c,d +v d -ωLi q #(27)

[0130] Among them, ωLi q represents the voltage drop component of the inductor L on the d-axis, u d It represents the component of the output voltage of the three-phase fully controlled bridge circuit on the d-axis;

[0131] On the quadrature axis (q axis), the current control target value i in the dq domain is q,ref with i q For comparison, the difference is controlled by using a PID controller, and the output u c,q With v q and ωLi d Calculate u together as follows q :

[0132] u q =u c,q +v q +ωLi d #(28)

[0133] Among them, ωLi d represents the component of the voltage drop of the inductor L on the q axis, u q It represents the component of the output voltage of the three-phase fully controlled bridge circuit on the q axis;

[0134] Get u d and uq Then, divide the values ​​by the DC voltage v DC half of the modulation signal m in the dq domain dq =[m d m q ] T , m d 、m q Respectively represent m dq The components on the d and q axes are then inversely transformed to obtain the three-phase reference voltage vector v abc,ref :

[0135]

[0136] in:

[0137]

[0138] Get the three-phase reference voltage vector v abc,ref After that, it can be used as a modulation signal to obtain the pulse width modulation (PWM) algorithm by switching T 1 ~T 6 The three-phase bridge type full-control circuit consists of switches T in each bridge arm 1 ~T 6 The gate control signal G 1 ~G 6 .

[0139] (3) Alternating conduction control of battery packs;

[0140] The pulse charging method is used to control the alternating conduction when charging or discharging the battery pack, and the intermittent alternating conduction can be used to connect n battery packs in the same multi-battery bidirectional charging and discharging system.

[0141] Assume battery pack B i The charging or discharging voltage is U i , the charging or discharging current is I i , the charging or discharging power is P i , the pulse duty cycle is d i , the instantaneous charging or discharging power of the multi-battery bidirectional charging and discharging system is P s , where i∈[1,n], the above variables should satisfy the following relationship:

[0142] P i =U i I i d i =P s d i #(31)

[0143] Among them, the charging or discharging voltage U iUsually depends on the set system charging or discharging power, charging or discharging current I i It depends on U i , the working voltage of the battery E i , the internal resistance of the battery and the on-resistance of the switch, so adjust the pulse duty cycle d i Adjustable battery pack B i The average charging or discharging power P i , while not changing the instantaneous charging or discharging power P of the multi-battery bidirectional charging and discharging system s .

[0144] In order to reduce the fluctuation of voltage and current amplitude on the AC side of the multi-battery bidirectional charging and discharging system, the conduction intervals of the n battery packs connected to the multi-battery bidirectional charging and discharging system should be staggered as much as possible within a period T, and the sum of them is equal to an integer multiple of the period, that is:

[0145]

[0146] With n = 2, d i =0.5, P 1 =P 2 (P 1 For battery pack B 1 The charging or discharging power, P 2 For battery pack B 2 The charging or discharging power of the multi-battery bidirectional charging and discharging system is maintained constant at P. s .

[0147] When the battery pack is in the charging state, the switch T C1 Turn on, switch T D1 、T C2 、T D2 Turn off; switch T in the second half cycle C2 Turn on, switch T C1 、T D1 、T D2 Shut down.

[0148] When the battery pack is in the discharge state, the switch T D1 Turn on, switch T C1 、T C2 、T D2 Turn off; switch T in the second half cycle D2 Turn on, switch T C1 、T D1, T C2 Shut down.

[0149] When the charging or discharging power of any battery pack needs to be adjusted, the pulse duty cycle of one battery pack can be adjusted, and the pulse duty cycle of the other battery pack can be adjusted in the opposite direction. 1 The charging or discharging power P 1 , you can reduce the battery pack B 1 The pulse duty cycle d 1 At the same time, increase the battery pack B 2 The pulse duty cycle d 2 So that it still satisfies equation (16). This method can be used without changing the instantaneous charging or discharging power P s Under the premise of adjusting the charging or discharging power of the battery pack, the instantaneous charging or discharging power P of the system s Maintain constant, so that the voltage and current amplitude of the system AC side remain stable, reducing the impact of pulse charging or discharging on the power grid or other AC loads. s If the charging or discharging power of any battery group is adjusted under the premise of s .

[0150] If a battery pack stops charging or discharging during the charging or discharging process, the pulse duty ratio of the remaining battery packs in the system can be adjusted to satisfy equation (16) while ensuring that the current of each battery pack does not exceed its maximum allowable current. This method can be used without changing the instantaneous charging or discharging power P s If the adjustment causes the charging or discharging current of all remaining battery packs in the system to exceed their maximum allowable current, the instantaneous charging or discharging power P of the system needs to be reduced. s To ensure battery safety.

[0151] If other battery packs are added to the system and start charging or discharging during the charging and discharging process, the pulse duty ratios of the remaining battery packs in the system can be adjusted to satisfy equation (16) while ensuring that the current of each battery pack does not exceed its maximum allowable current. This method can be used without changing the instantaneous charging or discharging power P s In the case of a partial battery pack, the charging or discharging process is allowed to end.

[0152] It is worth noting that the bidirectional charging and discharging system for multiple battery packs supporting pulse charging and discharging, its control system and control method provided by the present invention are not limited to the case where the battery pack is charged or discharged using pulse current, but can also be used in application scenarios where the battery pack is charged or discharged using continuous current. Continuous current can be regarded as a special form of pulse current, that is, a pulse current with a pulse duty cycle of 1. Therefore, when the battery is charged and discharged using continuous current, formula (16) is automatically satisfied, thereby avoiding fluctuations in the voltage and current amplitude on the AC side of the system during the charging and discharging process.

[0153] The feasibility and effectiveness of a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging and its control system and control method provided by the present invention have been confirmed by computer time domain simulation. The simulation tool uses MATLAB Simulink, and the system parameters in the simulation embodiment are given in Table 1 below.

[0154] Table 1 System parameters in simulation example

[0155]

[0156]

[0157] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0158] Example 1: Using pulse current from the grid to charge two battery packs simultaneously

[0159] Consider two identical battery packs, each consisting of 125 lithium iron phosphate cells connected in series, with an initial state of charge (SOC) of 50% and a rated operating voltage of 400V. Pulse current is used to charge the two battery packs from the power grid through a multi-battery bidirectional charging and discharging system, and the average charging power of each battery pack is set to 50kW. Between 0 and 5 seconds, each battery pack is charged with a 1Hz pulse current. At the same time, the charging pulses of each battery pack are staggered and the duty cycle satisfies equation (16) to reduce the fluctuation of the pulse current on the power grid, and the DC power P output on the DC side of the multi-battery bidirectional charging and discharging system is controlled. s,ref 100kW. Battery Pack B 1 and battery pack B 2 The charging voltage and current waveforms are shown in Figure 5 and Figure 6 In this embodiment, the battery charging current is assumed to be a negative value, and the discharging current is assumed to be a positive value. Figure 5 and Figure 6 It can be seen that during this period, battery pack B 1 and battery pack B 2 The charging is performed alternately, and the voltage and current amplitudes when the charging is performed are basically the same.

[0160] During the charging process, the AC side power and DC side power output of the system remain unchanged, and the DC side output power is consistent with the control target 100kW. Figure 7 and Figure 8 .

[0161] Starting from the 5th second, battery pack B 2 Exit charging. If you want to keep the system transmission power unchanged, you can increase the battery pack B. 1 The charging pulse duty cycle of is such that it continues to satisfy equation (16). Figure 5 and Figure 6 It can be seen that battery pack B 1 The charging pulse duty cycle is increased to 1, which actually becomes a constant current charge, and the battery pack B 2 The charging current drops to zero and charging stops. Due to the use of the multi-battery bidirectional charging and discharging system and its control system and control method of the present invention, the AC side power and DC side power of the system remain unchanged, and there is no 2 After stopping charging, fluctuations occur. Figure 7 and Figure 8 During the entire charging process, the AC current and DC voltage remain basically constant. Fig. 9 and Fig.10 .

[0162] Example 2: Discharging from two battery packs to the grid simultaneously using pulse current

[0163] Consider the same two battery packs as in Example 1. In this case, pulse current is used to discharge from the battery pack to the grid through the multi-battery pack bidirectional charge-discharge system. The discharge power of the multi-battery pack bidirectional charge-discharge system to the grid is set to 100kW. Between 0 and 5 seconds, each battery pack is discharged with a pulse current of 1Hz. At the same time, the discharge pulses of each battery pack are staggered and the duty cycle satisfies equation (16) to reduce the fluctuation of the output current on the AC side of the system, and the DC power P output on the DC side of the multi-battery pack bidirectional charge-discharge system is controlled to be AC,ref 100kW. Battery Pack B 1 and battery pack B 2 The discharge voltage and current waveforms are shown in Fig.11 and Fig.12 .Depend on Fig.11 and Fig.12 It can be seen that during this period, battery pack B 1 and battery pack B 2 The discharge is alternately turned on and off, and the voltage and current amplitudes when it is turned on are basically the same.

[0164] During the discharge process, the system output power on the AC side and the input power on the DC side remain unchanged, and the output power on the AC side is consistent with the control target of 100kW. Fig.13 and Fig.14 .

[0165] Starting from the 5th second, battery pack B 1 Exit discharge. If you want to keep the system's output power to the grid unchanged, you can increase the battery pack B 2 The charging pulse duty cycle of 200mA makes it continue to satisfy equation (16). Fig.11 , Fig.12 It can be seen that battery pack B 2 The charge pulse duty cycle is increased to 1, which actually becomes a constant current discharge, and the battery pack B 1 The discharge current drops to zero and the discharge stops. Due to the use of the multi-battery bidirectional charging and discharging system and its control system and control method of the present invention, the power output on the AC side and the power input on the DC side of the system remain unchanged, and there is no 1 After stopping charging, fluctuations occur. Fig.13 and Fig.14 During the whole discharge process, the AC side current and DC side voltage remain basically constant. Fig.15 and Fig.16 .

[0166] Example 3: Using a constant current to charge two battery packs simultaneously from the grid

[0167] Consider the same two battery packs as in the above embodiment, using a constant current from the grid through the bidirectional charging and discharging system to charge the two battery packs. Between 0 and 1 seconds, the charging power of each battery pack is set to 50 kW, so the DC side of the multi-battery bidirectional charging and discharging system is controlled to output a DC power P s,ref is 100kW. After the first second, battery pack B 2 End charging, battery pack B 1 The charging power remains unchanged, so it is necessary to reduce the DC power P output on the DC side of the bidirectional charging and discharging system. s,ref It is 50kW.

[0168] Battery Pack B 1 and battery pack B 2 The charging voltage and current waveforms are shown in Fig.17 and Fig.18 .Depend on Fig.17 and Fig.18 It can be seen that during the first period of time, both battery packs are charging and the charging voltage and current are basically equal, and the charging power is 50kW. 2 Charging is finished and the charging current drops to zero. Battery Pack B 1The charging current returns to its previous size after a short transient process, and the charging power remains unchanged at 50kW.

[0169] During the charging process, the DC output power of the system is consistent with the control target of 100kW in the 0-1 second interval; in the 1-2 second interval, due to the battery pack B 2 After charging is completed, the DC output power of the system gradually decreases to 50kW. Fig.19 Because the system has energy loss, the AC power input to the system is slightly greater than the DC power output. Similarly, the input power on the AC side of the system also decreases from slightly more than 100kW in the 0-1 second interval to slightly more than 50kW in the 1-2 second interval. Fig. 20 .

[0170] Battery Pack B 2 After quitting charging, the input power of the system AC side decreases. Since the voltage amplitude of the AC side remains unchanged, the current amplitude decreases. Fig.21 During the whole process, the DC voltage remained basically constant, and only recovered to its previous value after a brief fluctuation after 1 second. Fig. 22 .

[0171] Example 4: Discharging from two battery packs to the grid simultaneously using a constant current

[0172] Consider the same two battery packs as in the above embodiment, using a constant current to discharge from the battery to the grid through the multi-battery bidirectional charging and discharging system. Between 0 and 1 seconds, only battery pack B 1 Discharge to the grid, set the system to discharge the AC power to the grid is 50kW, so the AC side output power P of the multi-battery bidirectional charging and discharging system is controlled AC,ref After the first second, the AC side output power P of the multi-battery bidirectional charging and discharging system is AC,ref Increase to 100kW, battery pack B 1 The battery pack B cannot provide the required power alone. 2 Also join the discharge, battery group B 1 Charging power remains unchanged.

[0173] Battery Pack B 1 Battery Pack B 2 The charging voltage and current waveforms are shown in Fig.23 and Fig.24 .Depend on Fig.23 and Fig.24 It can be seen that within 0-1 second, battery pack B 1 Discharge, the current amplitude is constant, because the system has energy loss, so the battery pack B 1 The discharge power is slightly higher than the system AC side output target power of 50kW; battery pack B 2No discharge, so its current value is zero. After the first second, because the output target power of the system AC side is increased to 100kW, battery pack B 1 cannot provide all the power, so battery pack B 2 During this period, battery pack B 1 The discharge power remains unchanged, so the current remains basically the same as before, battery pack B 2 Start discharging at a rate higher than 50kW, and the discharge current is the same as that of battery pack B. 1 quite.

[0174] During the discharge process, the system AC side output power is consistent with the control target of 50kW in the 0-1 second interval; in the 1-2 second interval, due to the increase in the set control target, the battery pack B 2 With the addition of discharge, the system AC side output power gradually increases to 100kW. Fig.25 Similarly, the system DC side input power also increases from slightly more than 50kW in the 0-1 second interval to slightly more than 100kW in the 1-2 second interval. Fig.26 .

[0175] Battery Pack B 2 After the discharge is added, the output power of the system AC side increases. Since the voltage amplitude of the AC side remains unchanged, the current amplitude increases. Fig. 27 During the whole process, the DC side voltage remains basically constant. Fig.28 .

[0176] It can be seen from the above four embodiments that the bidirectional charging and discharging system for multiple battery packs supporting pulse charging and discharging proposed in the present invention can realize the bidirectional flow of electric energy between its AC side power supply and multiple battery packs on its DC side, achieving the design purpose of a set of charging and discharging equipment serving multiple battery packs at the same time, which can reduce the construction cost of charging infrastructure, and can not only provide charging services for batteries, but also realize functions such as V2G, V2H, and V2B. The control system and control method for the bidirectional charging and discharging system for multiple battery packs supporting pulse charging and discharging proposed in the present invention can realize the control of the power on the DC side or AC side of the bidirectional charging and discharging system for multiple battery packs, and can smooth the impact of the current amplitude fluctuation in the process of charging or discharging the battery using pulse current on the system and the power grid. In particular, the bidirectional charging and discharging system for multiple battery packs supporting pulse charging and discharging proposed in the present invention and its control system and control method are not limited to the occasions where pulse current is used to charge and discharge the battery. When continuous current is used, the system and its control strategy proposed in the present invention are still effective.

[0177] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multi-battery bidirectional charging and discharging system supporting pulse charging and discharging, characterized in that: include: A harmonic filter stage, a power factor correction stage, a DC-DC converter stage and a plurality of switch device groups; the harmonic filter stage is composed of a group of inductors; the power factor correction stage is composed of a three-phase bridge full-controlled circuit and a filter capacitor in parallel; the DC-DC converter stage is composed of a phase-shifted full-bridge circuit, which includes a first single-phase bridge full-controlled circuit, an isolation transformer and a second single-phase bridge full-controlled circuit; the AC side of the power factor correction stage is connected to a power grid, an AC power supply or an AC load, the DC side of the power factor correction stage is connected to the DC-DC converter stage, the first single-phase bridge full-controlled circuit of the DC-DC converter stage is connected in series with the isolation transformer, the other side of the isolation transformer is connected to the second single-phase bridge full-controlled circuit, the second single-phase bridge full-controlled circuit is connected to the capacitor C B After being connected in parallel, they are connected to a plurality of switch device groups, and each switch device group is connected in series with a battery group; When the battery pack is charged, the three-phase bridge-type full-controlled circuit of the power factor correction stage works in a rectifying state, responsible for rectifying the AC power on the AC side into DC power, filtering some harmonics through the filter capacitor, and stabilizing the DC side voltage at the same time; the first single-phase bridge-type full-controlled circuit of the DC-DC converter stage inverts the DC side voltage into industrial frequency or high-frequency AC power and then inputs it into the primary side of the isolation transformer; the isolation transformer is used to achieve electrical isolation and improve system safety; the second single-phase bridge-type full-controlled circuit of the DC-DC converter stage rectifies the AC power output from the secondary side of the isolation transformer into DC power, and then transmits the electric energy to the battery pack through the switch device group, completing the transmission of electric energy from the power grid or AC load to the battery pack; When the battery pack discharges to the system AC side power grid or AC load, the electric energy flows from the battery pack through multiple switching device groups to the second single-phase bridge full-controlled circuit of the DC-DC converter stage, which inverts the AC power output by the battery pack into industrial frequency or high-frequency AC power and then inputs it into the secondary side of the isolation transformer; the AC power output by the primary side of the isolation transformer is then rectified into DC power by the first single-phase bridge full-controlled circuit of the DC-DC converter stage and transmitted to the three-phase bridge full-controlled circuit of the power factor correction stage. At this time, the three-phase bridge full-controlled circuit works in the inverter state, which inverts the DC power on the DC side into industrial frequency AC power and transmits it to the power grid or AC load, completing the transmission of electric energy from the battery pack to the power grid or AC load.

2. The multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 1 is characterized in that: The three-phase bridge full-control circuit is composed of switches T1-T6.

3. The multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 1, characterized in that: The first single-phase bridge full-control circuit of the DC-DC converter stage is composed of switches T7 to T 10 composition.

4. The multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 1, characterized in that: The second single-phase bridge full-control circuit of the DC-DC converter stage is composed of a switch T 11 ~T 14 composition.

5. The multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 1, characterized in that: The n switch groups are denoted as T B1 , T B2 ,…,T Bn , switch group T B1 By switch T C1 and switch T D1 Composition, switch group T B2 By switch T C2 and switch T D2 Composition, ..., switch group T Bn By switch T Cn and switch T Dn Composition, where n is a positive integer.

6. The control system of the multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to any one of claims 1 to 5, characterized in that: include: The AC side power controller is used to realize the active and reactive power control of the AC side of the multi-battery bidirectional charging and discharging system. Specifically, the three-phase AC voltage and current of the AC system are converted into the corresponding direct axis voltage v in the dq domain. d , quadrature axis voltage v q and the direct axis current i d , quadrature axis current i q , and then control the target value i of the direct-axis current according to the output of the reference current calculator d,ref and the quadrature axis current control target value i q,ref , calculate the gate control signals G1 to G6 of the switches T1 to T6 of each bridge arm of the three-phase bridge type full-control circuit composed of switches T1 to T6, so as to control the three-phase bridge type full-control circuit composed of switches T1 to T6 to work; The DC side power controller is used to realize the DC side power control of the multi-battery bidirectional charging and discharging system. Specifically, the DC side power controller receives the real-time power value P of the DC side measured by the DC side power meter. DC And the DC power control target value P DC,ref , using the proportional-integral-differential controller to control the active power control target value P output by the AC side power controller s,ref , and output it to the reference current calculator; The DC-DC conversion stage controller is used to control the switches T7 to T 10 The first single-phase bridge fully controlled circuit consisting of an isolation transformer and a switch T 11 ~T 14 The second single-phase bridge full-control circuit is composed of the output of each bridge arm switch T7~T 14 The gate control signal G7~G 14 , realize DC-AC-DC conversion, so as to meet the working conditions of the isolation transformer; The battery pack controller is used to control each battery pack B1, B2, ..., B n Working state, output control signal G C1 , G C2 , …, G Cn For control switch T C1 , T C2 ,…,T Cn and control signal G D1 , G D2 , …, G Dn For control switch T D1 , T D2 ,…,T Dn ; For battery pack i∈[1,n], when switch T Ci When turned on, battery pack B i Charging; when switch T Di When turned on, battery pack B i Discharge; and switch T Ci and switch T Di Cannot be turned on at the same time; The reference current calculator is used to receive the active power control target value P output by the DC side power controller. s,ref And reactive power control target value Q AC,ref , according to the two, the quadrature axis current control target value i in the dq domain is calculated d,ref and the quadrature axis current control target value i q,ref and output it to the AC side power controller; The DC power meter is used to measure the real-time power value P of the DC side. DC And output to the DC side power controller.

7. The control method of a multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) DC side power control of multi-battery bidirectional charging and discharging system; Set the DC power output or input of the system DC side, that is, the target power P DC,ref , when P DC,ref >0, the multi-battery bidirectional charging and discharging system works in the charging mode, the battery pack is charged, let F = -1; when P DC,ref <0, the multi-battery bidirectional charging and discharging system works in the discharge mode, the battery pack is discharged, and F=1; Adopt closed-loop negative feedback control to control the DC power target value P DC,ref The actual DC power P DC The difference is compared and multiplied by F after passing through the proportional-integral-differential controller. s,ref As the active power control target value of the AC side power controller, F is a control factor used to change the active power control target value P output by the controller. s,ref Symbols; (2) AC side power control of multi-battery bidirectional charging and discharging system; If you need to control the DC side power P of a multi-battery bidirectional charging and discharging system DC , the current control target value i in the dq domain d,ref The active power control target value P s,ref Calculate as follows: If it is necessary to control the AC side power P of a multi-battery bidirectional charging and discharging system AC , the current control target value i in the dq domain d,ref The active power control target value P AC,ref Calculate as follows: Current control target value i in dq domain q,ref The reactive power control target value Q AC,ref Calculate as follows: Then the controlled variable AC side voltage v abc and the AC side current i abc Perform Park transformation into voltage v in dq domain dq and current i dq : in dq =Pv abc #(4) i dq =Pi abc #(5) in: v dq =[v d v q ] T #(6) i dq =[i d i q ]T#(7) v abc =[v a v b v c ] T #(8) i abc =[i a i b i c ] T #(9) Where ω represents the angular frequency of the AC system on the AC side of the charging system, t represents time, and v a Indicates the phase voltage of phase A of the AC system, v b Indicates the phase voltage of phase B of the AC system, v c Indicates the phase voltage of phase C of the AC system, v d represents the direct axis voltage in the dq domain, v q represents the quadrature axis voltage in the dq domain, i a Indicates the phase current of phase A of the AC system, i b Indicates the phase current of phase B of the AC system, i c Indicates the phase current of phase C of the AC system, i d represents the direct axis current in the dq domain, i q represents the quadrature-axis current in the dq domain, and the superscript T indicates transposition; On the direct axis, the current control target value i in the dq domain is d,ref with i d For comparison, a direct-axis proportional-integral-differential controller is used to control the difference, and the output u of the direct-axis proportional-integral-differential controller is c,d With v d and ωLi q Calculate u together as follows d : the d =the c,d +v d -ωLi q #(11) Among them, ωLi q represents the voltage drop component of the inductor L on the d-axis, u d It represents the component of the output voltage of the three-phase fully controlled bridge circuit on the d-axis; On the quadrature axis, the current control target value i in the dq domain is q,ref with i q The difference is controlled by using the cross-axis proportional-integral-differential controller, and the output u of the cross-axis proportional-integral-differential controller is c,q With v q and ωLi d Calculate u together as follows q : the q =the c,q +v q +ωLi d #(12) Among them, ωLi d represents the component of the voltage drop of the inductor L on the q axis, u q It represents the component of the output voltage of the three-phase fully controlled bridge circuit on the q axis; Get u d and u q Then, divide the values ​​by the DC voltage v DC half of the modulation signal m in the dq domain dq =[m d m q ] T , m d 、m q Respectively represent m dq The components on the d and q axes are then subjected to inverse Park transformation to obtain the three-phase reference voltage v abc,ref : in: (3) Alternating conduction control of battery packs; Assume battery pack B i The charging or discharging voltage is U i , the charging or discharging current is I i , the charging or discharging power is P i , the pulse duty cycle is d i , the instantaneous charging or discharging power of the multi-battery bidirectional charging and discharging system is P s , where i∈[1,n], the above variables should satisfy the following relationship: P i =U i I i d i =P s d i #(15) By adjusting the pulse duty cycle d i Adjustable battery pack B i The average charging or discharging power P i , while not changing the instantaneous charging or discharging power P of the multi-battery bidirectional charging and discharging system s .

8. The control method of the multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 7, characterized in that: In step (2), the three-phase reference voltage v is obtained abc,ref After that, it is used as a modulation signal and a pulse width modulation algorithm is used to obtain gate control signals G1-G6 of the switches T1-T6 of each bridge arm of the three-phase bridge full-control circuit composed of switches T1-T6.

9. The control method of the multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 7, characterized in that: In step (3), the conduction intervals of the n battery packs connected to the multi-battery pack bidirectional charge and discharge system within a period T should be staggered, and the sum of the conduction intervals is equal to an integer multiple of the period, that is:

10. The control method of the multi-battery bidirectional charging and discharging system supporting pulse charging and discharging according to claim 7, characterized in that: In step (4), when it is necessary to adjust the charging or discharging power of any one of the battery packs, the pulse duty cycle of one of the battery packs can be adjusted, and the pulse duty cycle of the other battery pack can be adjusted inversely.

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