Multi-battery pack bidirectional charge-discharge system supporting pulse charge-discharge and control method thereof

Abstract

The application discloses a multi-battery-pack bidirectional charge-discharge system supporting pulse charge-discharge and a control method thereof, and belongs to the field of power electronics. The bidirectional charge-discharge system comprises a power factor correction (PFC) stage composed of a three-phase bridge full-control circuit, a direct current-direct current (DC-DC) converter stage and a plurality of switching device groups. The application utilizes the intermittent characteristics of the pulse charging current, and through staggering the conduction interval of the pulse current, the different battery packs are alternately charged and discharged, so that the current and voltage fluctuation of the alternating current power supply side in the energy flow process is reduced, and the influence of the system on the stability of the power grid or other power supply is reduced. The application supports pulse charge-discharge, can reduce the battery polarization effect, prolong the service life, improve the charging efficiency, reduce the required hardware devices for charging and reduce the cost. The application allows the energy to flow bidirectionally between the alternating current side and the direct current side of the system and the power is controllable, supports V2G application, and can be used in the scenes of charging or discharging the battery by using the pulse current and the 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, constant voltage, and constant voltage-constant current. Constant current uses a constant current for faster charging, but can cause overcharging. While constant voltage can prevent overcharging, it is slower. Compared to constant current, constant voltage allows lithium batteries to be almost fully charged, preventing overcharging. However, it takes longer to complete the charging process and accelerates capacity decay. Constant voltage-constant current combines the advantages of both technologies, improving charging speed while avoiding overcharging. During charging, constant voltage-constant current maintains a constant charging current until the battery reaches a preset voltage. The voltage is then kept constant while the charging current decreases exponentially, terminating the charge when the current reaches its minimum. To further increase charging speed, various charging methods have emerged, such as multi-stage constant current-constant voltage charging, which consists of several constant current stages of varying magnitudes, followed by a constant voltage stage to conclude 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, increase the power transfer rate, and thus reduce 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, and the charging time is 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. They can absorb electricity from the grid when the grid load is low, the electricity price is low, and the battery needs to be charged. When the grid load is high and the electricity price is high, they can use vehicle-to-grid (V2G) technology to discharge back to the grid, thereby achieving peak shaving and valley filling and promoting the consumption of renewable energy. The rapid 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 using a photovoltaic power generation system to charge a battery, in order to enable the photovoltaic panel to 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 Configurationby 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 in proper coordination. However, this system requires the use of two additional smaller batteries for assistance and cannot achieve bidirectional energy flow between the AC side and the DC side of the system. In the literature [2] Zhenhua Jiang and RADougal, "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.], a technical solution for controlling the pulse current of a fuel cell by adjusting a step-down chopper converter is proposed. This solution adopts a multi-cell coordinated charging method to avoid drastic changes in the output power of the fuel cell.Reference [3] KSVenkat, MVSatya Sai Chandra and S.Mohapatro,"PulseCharging Scheme forMultiple Battery Charging in ElectricVehicleApplications,"2023IEEE 3rd International Conference on SmartTechnologies 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 using pulse charging current to charge or discharge batteries in the prior art, thereby providing a multi-battery bidirectional charging and discharging system that supports pulse charging and discharging and its control method.

[0006] The present invention provides a bidirectional charging and discharging system for multiple battery packs 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 to charge multiple battery packs, thereby reducing the cost of charging facilities.

[0007] The technical solutions adopted by the present invention to solve the technical problems are 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 (PFC) stage, a DC-DC (DC-DC) converter stage, and multiple switching 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-type 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-type full-controlled circuit, an isolation transformer, and a second single-phase bridge-type 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, and the DC side of the power factor correction stage is connected to the DC-DC converter stage. The first single-phase bridge-type full-controlled circuit of the DC-DC converter stage is connected in series with the isolation transformer, and the other side of the isolation transformer is connected to the second single-phase bridge-type full-controlled circuit, and the second single-phase bridge-type full-controlled circuit is connected to the capacitor C B After being connected in parallel, they are then connected to multiple switch device groups, and each switch device group is connected in series with a battery group;

[0009] When the battery pack is charging, the three-phase bridge-type fully-controlled circuit of the power factor correction stage operates 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. The first single-phase bridge-type fully-controlled circuit of the DC-DC converter stage inverts the DC side voltage into industrial frequency or high-frequency AC power, which is then input 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 fully-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 electrical energy to the battery pack through multiple switching device groups, completing the transmission of electrical energy from the power grid or AC load to the battery pack.

[0010] When the battery pack discharges to the system AC side 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 operates in the inverter state, which inverts the DC power on the DC side into industrial frequency AC power and transmits it to the grid or AC load, completing the transmission of electric energy from the battery pack to the grid or AC load.

[0011] Furthermore, the three-phase bridge full-control circuit is composed of switches T1 to T6.

[0012] Furthermore, the first single-phase bridge full-control circuit of the DC-DC converter stage is composed of switches T7 to 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 where n is a positive integer.

[0015] Furthermore, the switches T1 to 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, 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 according to the direct axis current output by the reference current calculator d,ref and the quadrature axis current control target value i q,ref , calculating the gate control signals G1 to G6 of the switches T1 to T6 of each bridge arm of the three-phase bridge full-control circuit composed of switches T1 to T6, thereby controlling the three-phase bridge full-control circuit composed of switches T1 to T6 to operate;

[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. DCAnd 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 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 , realizing DC-AC-DC conversion, thereby meeting the working conditions of the isolation transformer;

[0020] 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 controlling switch T C1 、T C2 ,…,T Cn and control signal G D1 , G D2 ,…,G Dn For controlling 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 from the DC side power controller. s,ref And reactive power control target value Q AC,ref , calculate the quadrature axis current control target value i in the dq domain based on the two 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 side 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 charge and discharge 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 side real-time power P DC The difference is compared and multiplied by F after passing through the proportional-integral-differential (PID) controller. The product P 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 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 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 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 AC side current i abcPerform Park transform 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, 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;

[0043] On the direct axis, the current control target value i in the dq domain isd,ref with i d For comparison, a 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 Indicates the component of the voltage drop 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 cross-axis proportional-integral-differential (PID) controller is used to control the difference, and the output u of the cross-axis proportional-integral-differential (PID) controller is 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 Indicates the component of the voltage drop of the inductor L on the q axis, u q 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 its value by the DC voltage v DC Half of the modulated signal m in the dq domain is obtained dq =[m d m q ] T , m d 、m q Represents 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], then 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 Then, the gate control signals G1 to G6 of the switches T1 to T6 of each bridge arm of the three-phase bridge full-control circuit composed of switches T1 to T6 are obtained by using the pulse width modulation (PWM) algorithm as the modulation signal.

[0058] Furthermore, in step (3), the conduction intervals of the n battery packs connected to the multi-battery bidirectional charge and discharge system within a period T should be staggered, and the sum of the conduction intervals should be 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, and 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 intervals of the pulse current, and rationally alternates the conduction of 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 in both directions 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 it can support V2G applications. It is worth noting that the present invention is not limited to applications where pulse current is used to charge or discharge batteries, but can also be used in application scenarios where continuous current is used to charge or discharge battery packs.

[0063] In addition, the present invention also proposes a control method for a multi-battery pack 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, and 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 This is a circuit topology diagram of a multi-battery bidirectional charging and discharging system that supports 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 The charging voltage and current curves of battery pack B1 are shown in FIG.

[0069] Figure 6 The charging voltage and current curves of battery pack B2 are shown in FIG.

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

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

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

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

[0074] Figure 11 is the discharge voltage and current curve of battery pack B1.

[0075] Figure 12 The discharge voltage and current curves of battery pack B2.

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

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

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

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

[0080] Figure 17 The charging voltage and current curves of battery pack B1 are shown in FIG.

[0081] Figure 18 The charging voltage and current curves of battery pack B2 are shown in FIG.

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

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

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

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

[0086] Figure 23 The charging voltage and current curves of battery pack B1 are shown in FIG.

[0087] Figure 24 The charging voltage and current curves of battery pack B2 are shown in FIG.

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

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

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

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

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

[0093] The present invention provides a multi-battery bidirectional charging and discharging system that supports 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. The bidirectional charging and discharging system of a multi-battery pack supporting pulse charging and discharging of the present invention mainly includes: a harmonic filter stage, a power factor correction (PFC) stage, a DC-DC (DC-DC) converter stage and a plurality of switching 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 three-phase bridge full-control circuit composed of switches T1 to T6, a filter capacitor C is connected in parallel on the DC side, and then a filter capacitor C is connected through a circuit composed of switches T7 to T8. 10 The first single-phase bridge type 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, it is 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, switches T1 to T 14 It can be any power electronic switch that meets the technical requirements, including but not limited to metal oxide semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), etc. The device shown in the drawings is only a specific embodiment of the present invention.

[0095] When the battery pack is charging, the three-phase bridge full-control circuit composed of switches T1 to T6 works in the rectification state, responsible for rectifying the AC power on the AC side (such as the 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 switches T7 to T 10 The first single-phase bridge type full-control circuit converts 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 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 packs B1, B2, ..., B through a set of switching devices. n Thus, the electric energy is transferred from the 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 packs B1, B2, ..., B n The current flows through the switch T 11 ~T 14 The second single-phase bridge full-control circuit is composed of a second single-phase bridge full-control circuit, which converts the AC output of the battery pack into industrial frequency or high-frequency AC and then inputs it into the secondary side of the isolation transformer; the AC output of the primary side of the isolation transformer is then transmitted through T7 to T 10 The single-phase fully-controlled bridge circuit rectifies the DC power and transmits it to the three-phase fully-controlled bridge circuit composed of switches T1 to T6. At this point, the three-phase fully-controlled bridge circuit composed of switches T1 to T6 operates in an inverter mode, converting the DC power on the DC side into industrial frequency AC power and transmitting it to the grid or AC load. This completes the transmission of electrical energy from the battery pack to the 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 that supports pulse charging and discharging, and its structure is as follows: Figure 2 As shown, the control system mainly includes: AC side power controller, DC side power controller, DC-DC conversion stage controller, battery pack controller, reference current calculator and DC side power meter.

[0099] Since energy can flow in both directions between the AC side and the DC side in a multi-battery bidirectional charging and discharging system, in order to facilitate the explanation of the working principle of its control system, this description defines that 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 according to the direct axis current output by the reference current calculator d,ref and the quadrature axis current control target value i q,ref , calculating the gate control signals G1 to G6 of the switches T1 to T6 of each bridge arm of the three-phase bridge full-control circuit composed of switches T1 to T6, thereby controlling the three-phase bridge full-control circuit composed of switches T1 to T6 to operate;

[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 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 , realizing DC-AC-DC conversion, thereby meeting the working conditions of the isolation transformer;

[0103] The battery pack controller is mainly used to control each battery pack B1, B2, ..., B n Working state, output control signal G C1 , G C2 ,…,G Cn For controlling switch T C1 、T C2 ,…,T Cn and control signal G D1 , G D2 ,…,G Dn For controlling switch T D1 、T D2 ,…,T Dn ; For switch group i, when switch T Ci When turned on, battery pack Bi 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 , calculate the quadrature axis current control target value i in the dq domain based on the two 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 side 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 its 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 charge and discharge 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 side real-time power P DC The difference is compared and 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 Serves 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 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 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 AC side current vector i abc Perform Park transform 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, 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 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 For comparison, a 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 Indicates the component of the voltage drop 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 iq For comparison, the cross-axis proportional-integral-differential (PID) controller is used to control the difference, and the output u of the cross-axis proportional-integral-differential (PID) controller is 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 Indicates the component of the voltage drop of the inductor L on the q axis, u q Represents the component of the output voltage of the three-phase fully controlled bridge circuit on the q-axis;

[0134] Get u d and u q Then, divide its value by the DC voltage v DC Half of the modulated signal m in the dq domain is obtained dq =[m d m q ] T , m d 、m q Represents m dq The components on the d and q axes are then subjected to inverse Park transformation 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 adopt a pulse width modulation (PWM) algorithm to obtain the gate control signals G1~G6 of each bridge arm switch T1~T6 of the three-phase bridge full-control circuit composed of switches T1~T6.

[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 its 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], then 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 i Usually depends on the set system charging or discharging power, charging or discharging current I i It depends on U i , battery operating voltage 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 charge and discharge system, the conduction intervals of the n battery packs connected to the multi-battery bidirectional charge and discharge system should be staggered as much as possible within a period T, and the sum of their conduction intervals should be equal to an integer multiple of the period, that is:

[0145]

[0146] With n=2, d i =0.5, P1=P2 (P1 is the charging or discharging power of battery pack B1, P2 is the charging or discharging power of battery pack B2), N=1 as an example, the first battery pack can be turned on in the first half of the cycle and turned off in the second half of the cycle, the second battery pack can be turned off in the first half of the cycle and turned on again in the second half of the cycle, and so on. In this way, the two battery packs can be charged alternately in one cycle, while maintaining the instantaneous charging or discharging power of the DC side of the multi-battery bidirectional charging and discharging system 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; in the second half cycle, switch TC2 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; in the second half cycle, switch T D2 Turn on, switch T C1 、T D1 、T C2 Shut down.

[0149] When it is necessary to adjust the charge or discharge power of any of the battery groups, the pulse duty cycle of one of the battery groups can be adjusted, and the pulse duty cycle of the other battery group can be adjusted inversely. Still taking n = 2, N = 1 as an example, if it is necessary to reduce the charge or discharge power P1 of battery group B1, the pulse duty cycle d1 of battery group B1 can be reduced while the pulse duty cycle d2 of battery group B2 can be increased so that it still satisfies formula (16). This method can be used without changing the instantaneous charge or discharge 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 is 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 pack 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 ratios of the remaining battery packs in the system can be adjusted to satisfy equation (16) 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 or discharging process, the pulse duty ratios of the remaining battery packs in the system can be adjusted to satisfy equation (16) without changing the instantaneous charging or discharging power P. sIn 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 a pulse current is used to charge or discharge the battery pack, but can also be used in application scenarios where a continuous current is used to charge or discharge the battery pack. 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 a continuous current is used to charge and discharge the battery, 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 the multi-battery bidirectional charge-discharge system supporting pulse charge and discharge, its control system, and its control method provided by the present invention have been confirmed through computer time-domain simulation. The simulation tool used was MATLAB Simulink, and the system parameters in the simulation example are given in Table 1 below.

[0154] Table 1 System parameters in the 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 embodiments described 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 making creative efforts 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. A pulse current is used to charge the two battery packs from the grid through a multi-battery bidirectional charge-discharge system, with an average charging power of 50kW set for each battery pack. Between seconds 0 and 5, 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 fluctuations caused by the pulse current on the grid, and the DC power P output from the DC side of the multi-battery bidirectional charge-discharge system is controlled. s,ref The charging voltage and current waveforms of battery pack B1 and battery pack B2 are shown in Figure 5 and Figure 6In this embodiment, the battery charging current is assumed to be negative and the discharge current is assumed to be positive. Figure 5 and Figure 6 It can be seen that during this time period, the battery pack B1 and the battery pack B2 are alternately turned on and charged, and the voltage and current amplitudes when they are turned on are substantially 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 of 100kW. Figure 7 and Figure 8 .

[0161] Starting from the 5th second, battery pack B2 stops charging. At this time, if you want to keep the system transmission power unchanged, you can increase the charging pulse duty cycle of battery pack B1 so that it continues to satisfy formula (16). Figure 5 and Figure 6 It can be seen that the charging pulse duty cycle of battery pack B1 is increased to 1, which actually becomes constant current charging, while the charging current of battery pack B2 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 do not fluctuate after battery pack B2 stops charging. Figure 7 and Figure 8 During the entire charging process, the AC side current and DC side voltage remain basically constant. Figure 9 and Figure 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 packs 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 seconds 0 and 5, each battery pack is discharged using a 1Hz pulse current. 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. The DC power P output on the DC side of the multi-battery pack bidirectional charge-discharge system is controlled to be AC,ref The discharge voltage and current waveforms of battery pack B1 and battery pack B2 are shown in Figure 11 and Figure 12 .Depend on Figure 11 and Figure 12 It can be seen that during this time period, the battery pack B1 and the battery pack B2 are alternately turned on and discharged, and the voltage and current amplitudes when they are turned on are substantially the same.

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

[0165] Starting from the 5th second, battery pack B1 stops discharging. At this time, if you want to keep the system's output power to the grid unchanged, you can increase the charging pulse duty cycle of battery pack B2 so that it continues to satisfy equation (16). Figure 11 、 Figure 12 It can be seen that the charging pulse duty cycle of battery pack B2 is increased to 1, which actually becomes a constant current discharge, while the discharge current of battery pack B1 drops to zero and stops discharging. 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 do not fluctuate after battery pack B1 stops charging. Figure 13 and Figure 14 During the whole discharge process, the AC side current and DC side voltage remain basically constant. Figure 15 and Figure 16 .

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

[0167] Consider the same two battery packs as in the above embodiment, using a constant current from the grid through the bidirectional charge-discharge system to charge the two battery packs. Between 0 and 1 seconds, the charging power of each battery pack is set to 50kW, so the DC side output DC power P of the multi-battery bidirectional charge-discharge system is controlled. s,ref After the first second, battery pack B2 finishes charging, and the charging power of battery pack B1 remains unchanged. Therefore, 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] The charging voltage and current waveforms of battery pack B1 and battery pack B2 are shown in Figure 17 and Figure 18 .Depend on Figure 17 and Figure 18 As can be seen, during the first period, both battery packs were charging with essentially equal charging voltage and current, each at a charging power of 50 kW. During the second period, battery pack B2 finished charging, and the charging current dropped to zero. After a brief transient, the charging current of battery pack B1 returned to its previous level, and the charging power remained unchanged at 50 kW.

[0169] During the charging process, the DC side output power of the system is consistent with the control target of 100kW in the interval of 0-1 second; in the interval of 1-2 seconds, due to the completion of charging of battery pack B2, the DC side output power of the system gradually decreases to 50kW, as shown in Figure 2. Figure 19Because the system has energy loss, the AC power input to the system is slightly greater than the DC power output. Similarly, the AC side input power 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. Figure 20 .

[0170] After battery pack B2 stops charging, the input power of the system AC side decreases. Since the voltage amplitude of the AC side remains unchanged, the current amplitude decreases. Figure 21 During the whole process, the DC side voltage remained basically constant, and only recovered to its previous value after a brief fluctuation after 1 second. Figure 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 charge-discharge system. Between 0 and 1 seconds, only battery pack B1 discharges to the grid. The AC power discharged by the system to the grid is set to 50kW. Therefore, the AC side output power P of the multi-battery bidirectional charge-discharge 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 When the power increases to 100kW, battery pack B1 cannot provide the required power alone. At this time, battery pack B2 also joins in the discharge, and the charging power of battery pack B1 remains unchanged.

[0173] The charging voltage and current waveforms of battery pack B1 and battery pack B2 are shown in Figure 23 and Figure 24 .Depend on Figure 23 and Figure 24 As can be seen, between seconds 0 and 1, battery pack B1 discharges with a constant current amplitude. Due to system energy losses, battery pack B1's discharge power is slightly higher than the system's AC-side target output power of 50 kW. Battery pack B2 does not discharge, so its current is zero. After the first second, the system's AC-side target output power increases to 100 kW, and battery pack B1 is unable to provide all the power, so battery pack B2 joins the discharge. During this period, battery pack B1's discharge power remains unchanged, so the current remains roughly the same as before. Battery pack B2 then begins discharging at a rate exceeding 50 kW, with a discharge current comparable to that of battery pack B1.

[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, battery pack B2 joins the discharge, and the system AC side output power gradually increases to 100kW, as shown in Figure 2. Figure 25Similarly, 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. Figure 26 .

[0175] After the battery pack B2 is added to the discharge, the system AC side output power increases. Since the AC side voltage amplitude remains unchanged, the current amplitude increases. Figure 27 During the whole process, the DC side voltage remains basically constant. Figure 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 by 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 by 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 by the present invention, its control system, and control method are not limited to the occasion where pulse current is used to charge and discharge the battery. When continuous current is used, the system and its control strategy proposed by 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 principles 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 that supports pulse charging and discharging, characterized by: include: A harmonic filter stage, a power factor correction stage, a DC-DC converter stage, and a plurality of switching 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 the power grid, AC power supply, or AC load, and 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, and the other side of the isolation transformer is connected to the second single-phase bridge full-controlled circuit, and the second single-phase bridge full-controlled circuit is connected to the capacitor C B After being connected in parallel, they are then connected to multiple switch device groups, and each switch device group is connected in series with a battery group; When the battery pack is charging, the three-phase bridge-type fully-controlled circuit of the power factor correction stage operates 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. The first single-phase bridge-type fully-controlled circuit of the DC-DC converter stage inverts the DC side voltage into industrial frequency or high-frequency AC power, which is then input 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 fully-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 electrical energy to the battery pack through the switching device group, completing the transmission of electrical energy from the power grid or AC load to the battery pack. When the battery pack discharges to the AC side grid or AC load of the system, electric energy flows from the battery pack through multiple switching device groups to the second single-phase bridge-type fully-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-type fully-controlled circuit of the DC-DC converter stage and transmitted to the three-phase bridge-type fully-controlled circuit of the power factor correction stage. At this time, the three-phase bridge-type fully-controlled circuit operates in the inverter state, inverting the DC power on the DC side into industrial frequency AC power and transmitting it to the grid or AC load, completing the transmission of electric energy from the battery pack to the grid or AC load; The three-phase bridge full-control circuit is composed of switches T1 to T6; the first single-phase bridge full-control circuit of the DC-DC converter stage is composed of switches T7 to T 10 The second single-phase bridge fully controlled circuit of the DC-DC converter stage is composed of a switch T 11 ~T 14 Composition; 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; 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, 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 according to the direct axis current output by the reference current calculator d,ref and the quadrature axis current control target value i q,ref , calculating the gate control signals G1 to G6 of the switches T1 to T6 of each bridge arm of the three-phase bridge full-control circuit composed of switches T1 to T6, thereby controlling the three-phase bridge full-control circuit composed of switches T1 to T6 to operate; 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 , realizing DC-AC-DC conversion, thereby meeting 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 controlling switch T C1 、T C2 ,…,T Cn and control signal G D1 , G D2 ,…,G Dn For controlling 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 from the DC side power controller. s,ref And reactive power control target value Q AC,ref , calculate the quadrature axis current control target value i in the dq domain based on the two d,ref and the quadrature axis current control target value i q,ref and output it to the AC side power controller; The DC side 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.

2. The control method of the multi-battery bidirectional charge and discharge system supporting pulse charge and discharge according to claim 1, 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 DC power control target value 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 charge and discharge 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 side real-time power P DC The difference is compared and multiplied by F after passing through the proportional-integral-differential controller. The product P 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 real-time power value P on the DC side of a multi-battery bidirectional charging and discharging system DC , the current control target value i in the dq domain d,ref 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 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 AC side current i abc Perform Park transform 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 Indicates the component of the voltage drop 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 For comparison, the cross-axis proportional-integral-differential controller is used to control the difference, 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 Indicates the component of the voltage drop of the inductor L on the q axis, u q 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 its value by the DC voltage v DC Half of the modulated signal m in the dq domain is obtained dq =[m d m q ] T , m d 、m q Represents 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], then 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 .

3. The control method of the multi-battery bidirectional charge and discharge system supporting pulse charge and discharge according to claim 2, characterized in that: In step (2), the three-phase reference voltage v is obtained abc,ref Then, the gate control signals G1 to G6 of the switches T1 to T6 of each bridge arm of the three-phase bridge full-control circuit composed of switches T1 to T6 are obtained by using the pulse width modulation algorithm as the modulation signal.

4. The control method of a multi-battery bidirectional charge and discharge system supporting pulse charge and discharge according to claim 2, characterized in that: In step (3), the conduction intervals of the n battery packs connected to the multi-battery bidirectional charge and discharge system within a period T should be staggered, and the sum of the conduction intervals should be equal to an integer multiple of the period, that is: N is a positive integer #(16).

5. The control method of a multi-battery bidirectional charge and discharge system supporting pulse charge and discharge according to claim 2, 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.

Images