A kind of cascaded channel number can be arbitrarily expanded large capacity energy storage system and its control system and method

Abstract

The application discloses a large-capacity energy storage system with an arbitrary expansion of cascade channels and a control system and method thereof. The energy storage system comprises n cascade four-port energy storage modules. The kth energy storage module comprises a first energy storage unit, a second energy storage unit, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first inductor, a second inductor, a first capacitor and a second capacitor, and is provided with a positive external terminal, a negative external terminal, a first neutral terminal and a second neutral terminal. The positive external terminal of the kth energy storage module is connected to a positive bus of a power supply, the negative external terminal is connected to a negative bus of the power supply, the first neutral terminal is connected to the second neutral terminal of the k-1th energy storage module, the second neutral terminal is connected to the first neutral terminal of the k+1th energy storage module, and the second neutral terminal of the last energy storage module is connected to the first neutral terminal of the first energy storage module. The energy storage module can be arbitrarily expanded, non-isolated partial power conversion can be realized, and automatic balancing can be realized.

Description

Technical Field

[0001] This invention relates to energy storage systems, and more particularly to a large-capacity energy storage system with arbitrarily expandable cascaded channel count, as well as its control system and method. Background Technology

[0002] In recent years, new energy power generation technologies, represented by solar and wind power, have flourished. However, because the power generation of new energy sources is easily affected by environmental factors such as sunlight intensity, temperature, and wind speed, the power output fluctuates greatly and is highly random. Peak power generation periods often do not align with peak electricity consumption periods, easily leading to power shortages and waste. Therefore, energy storage systems are widely used to fill the energy gap during off-peak periods of new energy power generation and to absorb excess energy as load during peak periods. Consequently, efficient management methods for large-capacity energy storage systems have been extensively researched and applied.

[0003] However, for traditional energy storage system energy management technologies, the rapid increase in system power capacity brings about power dissipation, control complexity, and increased size and weight, posing severe challenges to the system's economy and stability. To improve converter efficiency, partial power conversion technology has been widely researched and applied. However, in traditional series partial power conversion circuits, the converter's input and output cannot share a common ground, thus existing partial power conversion circuits must adopt isolated topologies. For example, in the paper "A Multiport Partial Power Converter for Smart Home Applications" published in IEEE Transactions on Power Electronics, Vol. 7, 2024, Dr. Yong Dae Kwon proposed a multiport partial power conversion circuit based on multiple boost circuits and resonant converters to manage distributed power sources, energy storage units, and electrical loads in smart home applications. This circuit achieves partial power conversion, effectively reducing the power capacity of the main power circuit and improving efficiency compared to traditional full-power converters. However, the introduction of the resonant converter brings isolation transformers and complex primary-side and rectifier circuits to the energy management system, resulting in high system cost and low power density, affecting the overall performance and economy of the converter.

[0004] For example, in the paper "High Efficiency and Full MPPT Range Partial Power Processing PV Module-Integrated Converter" published in the 5th issue of IEEE Transactions on Power Electronics in 2023, Dr. Mohammad Daryaei proposed a high-efficiency photovoltaic partial power converter that can achieve maximum efficiency point tracking across the entire range, and introduced a modular photovoltaic cell management circuit. Similarly, although this circuit achieves partial power conversion, the resulting isolation transformer, complex switching and rectifier networks, and its complex control methods all severely impact the overall performance of the converter.

[0005] The above-mentioned solutions can all improve the system's energy storage capacity through direct parallel connection. However, since each module requires individual control, the system's control complexity is directly proportional to its capacity. The surge in control costs associated with large-capacity energy storage systems further impacts their reliability and economic efficiency. In summary, current energy management solutions struggle to achieve partial power conversion based on non-isolated converters, and they also fail to address the increasing control complexity associated with multiple modules connected in parallel as system capacity increases. Therefore, a large-capacity energy storage system with arbitrarily expandable channel count, capable of non-isolated partial power conversion, and easily controllable, has become a much-needed technology. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a large-capacity energy storage system with expandable channel number, simpler control, and arbitrarily expandable cascaded channel number, as well as its control system and method.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a cascaded, high-capacity energy storage system with arbitrarily expandable channel count, comprising n cascaded four-port energy storage modules. The k-th stage four-port energy storage module includes a first energy storage unit, a second energy storage unit, a first switching transistor, and a first switching transistor Q. 1_#k Second switch Q 2_#k The third switch Q 3_#k The fourth switch Q 4_#k First inductor L 1_#k Second inductor L 2_#k First capacitor C 1_#k With the second capacitor C 2_#k It is equipped with a positive external terminal V. +_#k Negative external terminal V -_#kFirst neutral terminal N 1_#k Second neutral terminal N 2_#k ;

[0009] Among them, the positive external terminal V of the k-th stage four-port energy storage module +_#k Connected to the positive terminal V of the power bus + The negative external terminal V -_#k Connected to the negative terminal V of the power bus - The first neutral terminal N 1_#k The second neutral terminal V connected to the (k-1)th stage four-port energy storage module -_#k-1 The second neutral terminal N 2_#k The first neutral terminal N connected to the (k+1)th stage four-port energy storage module 1_#k+1 The second neutral terminal N of the last stage four-port energy storage module 2_#n The first neutral terminal N connected to the first stage four-port energy storage module 1_#1 ,

[0010] The negative terminal of the first energy storage unit is connected to the negative external terminal V. -_#k The positive terminal is connected to the first neutral terminal N. 1_#k The positive terminal of the second energy storage unit is connected to the external positive terminal V. +_#k The negative electrode is connected to the first capacitor C. 1_#k Connected to the negative external terminal V -_#k The first neutral terminal N 1_#k via the first switching transistor Q 1_#k First inductor L 1_#k The third switch Q 3_#k Second inductor L 2_#k Connect to the second neutral terminal N 2_#k The second switch Q 2_#k One end is connected to the negative external terminal V. -_#k The other end is connected to the first switching transistor Q. 1_#k With the first inductor L 1_#k Between, the fourth switch Q 4_#k One end is connected to the positive external terminal V. +_#k The other end is connected to the third switch Q. 3_#k Second inductor L 2_#k Between, the second neutral terminal N 2_#k Through the second capacitor C 2_#k Connect to the positive external terminal V +_#k .

[0011] As an alternative, the first switch Q 1_#k The drain is connected to the first neutral terminal N. 1_#k The source is connected to the second switch Q.2_#k Drain and first inductor L 1_#k The first terminal, the second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k First inductor L 1_#k The second end is connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the third switch Q 3_#k The source, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k The third switch Q 3_#k The drains are connected to the fourth switching transistor Q. 4_#k Source and second inductor L 2_#k The first terminal, the fourth switch Q 4_#k Drain connected to positive terminal V +_#k Second inductor L 2_#k The second end is connected to the second neutral terminal N. 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

[0012] As an alternative approach, the first inductor L 1_#k The first end is connected to the first neutral terminal N 1_#k The second end is connected to the first switching transistor Q. 1_#k Source and second switch Q 2_#k Drain, second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k The first switching transistor Q 1_#k The drains are connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the second inductor L 2_#k The first terminal, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k Second inductor L 2_#k The second end is connected to the fourth switch Q. 4_#k Source and third switch Q 3_#k Drain, fourth switch Q 4_#k Drain connected to positive terminal V +_#k The third switch Q 3_#k Source connected to the second neutral terminal N 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

[0013] As another alternative, the k-th stage four-port energy storage module also includes a fifth switch Q. 5_#k The sixth switch Q 6_#k The seventh switch Q 7_#k and the eighth switch Q 8_#k The first switch Q 1_#k The drain is connected to the first neutral terminal N. 1_#k The source is connected to the second switch Q. 2_#k Drain and first inductor L 1_#k The first terminal, the second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k First inductor L 1_#k The second end is connected to the sixth switch Q. 5_#k Source and fifth switch Q 5_#k Drain, fifth switch Q 5_#k The source is connected to the external terminal V of the negative terminal. -_#k The sixth switch Q 6_#k The drains are connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the third switch Q 3_#k The source, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k The third switch Q 3_#k The drains are connected to the fourth switching transistor Q. 4_#k Source and second inductor L 2_#k The first terminal, the fourth switch Q 4_#k Drain connected to positive terminal V +_#k Second inductor L 1_#k The second end is connected to the seventh switch Q. 7_#k Source and eighth switch Q 8_#k Drain, seventh switch Q 7_#k Drain connected to positive terminal V +_#k The eighth switch Q 8_#k Source connected to the second neutral terminal N 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

[0014] This invention also provides a control system for a large-capacity energy storage system with arbitrarily expandable cascaded channel count, comprising:

[0015] Voltage and current sampling circuit, used to sample the first inductor current i of any four-port energy storage module. L1_#k Second inductor current i L2_#k and the positive V of the power bus+ With the negative terminal V of the power bus - Bus voltage v between o ;

[0016] Error amplifier, used to calculate the first inductor current i L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0017] A PI controller is used to process the error signal err separately. iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0018] The PWM generator is used to generate PWM drive signals pwm1 and pwm3 for the first and third switching transistors respectively, based on the duty cycle signals d1 and d2 of the first and third switching transistors, and to generate PWM drive signals pwm2 and pwm4 for the second and fourth switching transistors respectively, which are complementary to the PWM drive signals pwm1 of the first and third switching transistors.

[0019] The signal amplifier is used to amplify the PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor, and then input them to the first, second, third, and fourth switches of all four-port energy storage modules.

[0020] This invention also provides a control system for a large-capacity energy storage system, comprising:

[0021] Voltage and current sampling circuit, used to sample the first inductor current i of all four-port energy storage modules. L1_#1 ~ i L1_#n Second inductor current i L2_#1 ~ i L2_#n The voltage v of the first energy storage unit s1_#1~ v s1_#n The voltage v of the second energy storage unit s2_#1~v s2_#n and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0022] The sampling signal analysis program is used to analyze the sampled voltage and current signals, determine whether the four-port energy storage module is normal, and disconnect abnormal four-port energy storage modules; and to set the first inductor current i of any normal four-port energy storage module. L1_#k Second inductor current i L2_#k and bus voltage v o Output to error amplifier;

[0023] Error amplifier, used to calculate the first inductor current i L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0024] A PI controller is used to process the error signal err separately. iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0025] The PWM generator is used to generate PWM drive signals pwm1 and pwm3 for the first and third switching transistors respectively, based on the duty cycle signals d1 and d2 of the first and third switching transistors, and to generate PWM drive signals pwm2 and pwm4 for the second and fourth switching transistors respectively, which are complementary to the PWM drive signals pwm1 of the first and third switching transistors.

[0026] The signal amplifier is used to amplify the PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor, and then input them to the first, second, third, and fourth switches of all four-port energy storage modules.

[0027] The present invention also provides a control method for the above-mentioned large-capacity energy storage system with arbitrarily expandable cascaded channel number, comprising the following steps:

[0028] Sample the first inductor current i in any four-port energy storage module L1_#k Second inductor current i L2_#k and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0029] Calculate the first inductor current i respectively L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0030] For the error signal err respectively iL1_#k err iL2_#k err v_#k A PI control is performed to implement dual-loop voltage and current control, obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0031] Based on the duty cycle signals d1 and d2 of the first and third switching transistors, respectively, PWM drive signals pwm1 and pwm3 of the first and third switching transistors are generated. Additionally, PWM drive signals pwm2 and pwm4 of the second and fourth switching transistors, which are complementary to the PWM drive signal pwm1 of the first and third switching transistors, respectively, are also generated.

[0032] The PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor are amplified and then input to the first, second, third, and fourth switches of all four-port energy storage modules.

[0033] The present invention also provides another control method for the above-mentioned large-capacity energy storage system with arbitrarily expandable cascaded channel number, comprising the following steps:

[0034] Sample the first inductor current i in all four-port energy storage modules L1_#1 ~ iL1_#n Second inductor current i L2_#1 ~i L2_#n The voltage v of the first energy storage unit s1_#1~ v s1_#n The voltage v of the second energy storage unit s2_#1 ~v s2_#n and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0035] Analyze the sampled voltage and current signals to determine if the four-port energy storage module is functioning properly, and disconnect any abnormal four-port energy storage modules.

[0036] Calculate the first inductor current i of any normal four-port energy storage module. L1_#k Second inductor current i L2_#k And the bus voltage, and the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0037] For the error signal err respectively iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0038] Based on the duty cycle signals d1 and d2 of the first and third switching transistors, respectively, PWM drive signals pwm1 and pwm3 of the first and third switching transistors are generated. Additionally, PWM drive signals pwm2 and pwm4 of the second and fourth switching transistors, which are complementary to the PWM drive signal pwm1 of the first and third switching transistors, respectively, are also generated.

[0039] The PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor are amplified and then input to the first, second, third, and fourth switches of all four-port energy storage modules.

[0040] Compared with the prior art, the beneficial effects of this invention are:

[0041] 1. The system modules can be expanded arbitrarily without increasing control complexity: The energy storage system provided by this patent can be expanded arbitrarily, which makes it easy to flexibly change the capacity of the energy storage system as needed and improve the scalability of the system.

[0042] 2. Automatic voltage balancing can be achieved at each port of each energy storage module: The voltage of each port of each energy storage module in the energy storage system provided by this patent can be automatically balanced. Therefore, the energy storage system provided by this invention has low control difficulty and the control complexity is not affected by changes in system capacity and the number of parallel modules.

[0043] 3. Each energy storage unit achieves non-isolated partial power conversion: The unique internal connection of the four-port energy storage module provided by this invention solves the problem of partial power conversion relying on isolation converters. Compared with traditional management methods, this invention is more efficient, has higher power density, simpler control, and lower cost. Attached Figure Description

[0044] Figure 1 This is a circuit diagram of a large-capacity energy storage system with arbitrarily expandable cascaded channels provided in an embodiment of the present invention;

[0045] Figure 2 This is a circuit diagram of another four-port energy storage module provided in an embodiment of the present invention;

[0046] Figure 3 This is a circuit diagram of another four-port energy storage module provided in an embodiment of the present invention;

[0047] Figure 4 This is a structural block diagram of a control system for a large-capacity energy storage system with arbitrarily expandable cascaded channels, provided in an embodiment of the present invention.

[0048] Figure 5 for Figure 4 Control principle diagram;

[0049] Figure 6 This is a structural block diagram of the control system for another large-capacity energy storage system with arbitrarily expandable cascaded channels, provided in an embodiment of the present invention.

[0050] Figure 7 for Figure 1 The simulated current waveform of the energy storage system is shown.

[0051] Figure 8 for Figure 1 The simulated voltage waveform of the energy storage system is shown.

[0052] Figure 9 for Figure 1 The prototype of the energy storage system shown;

[0053] Figure 10 for Figure 1 The experimental drive waveform and inductor current waveform of the energy storage system are shown.

[0054] Figure 11 for Figure 1 The experimental drive waveform and inductor current waveform of the energy storage system are shown. Detailed Implementation

[0055] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0056] This invention provides a large-capacity energy storage system with arbitrarily expandable cascaded channel count, such as... Figure 1 As shown, it includes three cascaded four-port energy storage modules (#1 energy storage module ~ #3 energy storage module). The k-th stage four-port energy storage module includes two energy storage units (battery B). 1_#k and storage battery B 2_#k ), First switching transistor Q 1_#k Second switch Q 2_#k The third switch Q 3_#k The fourth switch Q 4_#k First inductor L 1_#k Second inductor L 2_#k First capacitor C 1_#k With the second capacitor C 2_#k It is equipped with a positive external terminal V. +_#k Negative external terminal V -_#k First neutral terminal N 1_#k Second neutral terminal N 2_#k k=1,2,3.

[0057] The external connection relationships of each four-port energy storage module are as follows: the positive external terminal V of the k-th level four-port energy storage module +_#k Connected to the positive terminal V of the power bus + The negative external terminal V -_#k Connected to the negative terminal V of the power bus - The first neutral terminal N 1_#k The second neutral terminal V connected to the (k-1)th stage four-port energy storage module -_#k-1 The second neutral terminal N 2_#k The first neutral terminal N connected to the (k+1)th stage four-port energy storage module 1_#k+1 The second neutral terminal N of the last stage four-port energy storage module 2_#n The first neutral terminal N connected to the first stage four-port energy storage module 1_#1 .

[0058] The internal connection relationships of each four-port energy storage module are as follows: Battery B 1_#k The negative terminal is connected to the external negative terminal V. -_#k The positive terminal is connected to the first neutral terminal N. 1_#k The B 2_#k The positive terminal is connected to the external positive terminal V. +_#k The negative electrode is connected to the first capacitor C. 1_#k Connected to the negative external terminal V -_#k The first neutral terminal N 1_#k via the first switching transistor Q 1_#k First inductor L 1_#k The third switch Q 3_#k Second inductor L 2_#k Connect to the second neutral terminal N 2_#k The second switch Q 2_#k One end is connected to the negative external terminal V. -_#k The other end is connected to the first switching transistor Q. 1_#k With the first inductor L 1_#k Between, the fourth switch Q 4_#k One end is connected to the positive external terminal V. +_#k The other end is connected to the third switch Q. 3_#k Second inductor L 2_#k Between, the second neutral terminal N 2_#k Through the second capacitor C 2_#k Connect to the positive external terminal V +_#k The first switching transistor Q 1_#k The drain is connected to the first neutral terminal N. 1_#k The source is connected to the second switch Q. 2_#k Drain and first inductor L 1_#k The first terminal, the second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k First inductor L 1_#k The second end is connected to the first capacitor C. 1_#k The first end, B 2_#k The negative terminal and the third switch Q 3_#k The source, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k The third switch Q 3_#k The drains are connected to the fourth switching transistor Q. 4_#k Source and second inductor L 2_#k The first terminal, the fourth switch Q 4_#k Drain connected to positive terminal V +_#k Second inductor L 2_#k The second end is connected to the second neutral terminal N. 2_#k The second capacitor C2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

[0059] Among them, the first, second, third, fourth, fifth, sixth, seventh, and eighth switching transistors of each energy storage module can be any power semiconductor device, including MOSFET, IGBT, and GaN.

[0060] It is understood that in other embodiments, the first energy storage unit and the second energy storage unit may also be any power supply device including photovoltaic panels, supercapacitors, electrolytic capacitors, and fuel cells.

[0061] In other embodiments, the structure of the four-port energy storage module can also be as follows: Figure 2 As shown, the first inductor L 1_#k The first end is connected to the first neutral terminal N 1_#k The second end is connected to the first switching transistor Q. 1_#k Source and second switch Q 2_#k Drain, second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k The first switching transistor Q 1_#k The drains are connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the second inductor L 2_#k The first terminal, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k Second inductor L 2_#k The second end is connected to the fourth switch Q. 4_#k Source and third switch Q 3_#k Drain, fourth switch Q 4_#k Drain connected to positive terminal V +_#k The third switch Q 3_#k Source connected to the second neutral terminal N 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

[0062] In other embodiments, the structure of the four-port energy storage module can also be as follows: Figure 3 As shown, compared to Figure 1 The structure shown further includes a fifth switch Q in the k-th stage four-port energy storage module. 5_#k The sixth switch Q 6_#k The seventh switch Q 7_#k and the eighth switch Q8_#k The first switch Q 1_#k The drain is connected to the first neutral terminal N. 1_#k The source is connected to the second switch Q. 2_#k Drain and first inductor L 1_#k The first terminal, the second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k First inductor L 1_#k The second end is connected to the sixth switch Q. 5_#k Source and fifth switch Q 5_#k Drain, fifth switch Q 5_#k The source is connected to the external terminal V of the negative terminal. -_#k The sixth switch Q 6_#k The drains are connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the third switch Q 3_#k The source, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k The third switch Q 3_#k The drains are connected to the fourth switching transistor Q. 4_#k Source and second inductor L 2_#k The first terminal, the fourth switch Q 4_#k Drain connected to positive terminal V +_#k Second inductor L 1_#k The second end is connected to the seventh switch Q. 7_#k Source and eighth switch Q 8_#k Drain, seventh switch Q 7_#k Drain connected to positive terminal V +_#k The eighth switch Q 8_#k Source connected to the second neutral terminal N 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

[0063] The following will be a brief description Figure 1 The voltage self-balancing principle of the energy storage system shown is as follows:

[0064] Let Q be the first switching transistor in the #1 energy storage module. 1_#1 The duty cycle of the drive signal is d 1_#1 When the first switching transistor Q 1_#1 When turned on, the first inductor L 1_#1 Voltage withstand:

[0065]

[0066] When the first switching transistor Q 1_#1 When turned off, the second switch Q 2_#1 When turned on, the first inductor L 1_#1 Voltage withstand:

[0067]

[0068] In a switching cycle T s Internally, according to the volt-second balance principle:

[0069]

[0070] We can obtain:

[0071]

[0072] Let Q be the third switch in the #1 battery energy storage module. 3_#1 The duty cycle of the drive signal is d 2_#1 Similarly, when the third switch Q... 3_#1 When turned on, the second inductor L 2_#1 Voltage withstand:

[0073]

[0074] When the third switch Q 3_#1 When turned off, the fourth switch Q 4_#1 When turned on, the second inductor L 2_#1 Voltage withstand:

[0075]

[0076] According to the volt-second balance principle, within one switching cycle:

[0077]

[0078] We can obtain:

[0079]

[0080] like Figure 1 As shown, V + With V - The output voltage v between o The voltages at each port satisfy the following:

[0081]

[0082] Similarly, let Q be the first switching transistor in the #2 battery energy storage module. 1_#2 The duty cycle of the drive signal is d 1_#2 Let Q be the third switch in the #2 energy storage module. 3_#2 The duty cycle of the drive signal is d 2_#2 We can obtain:

[0083]

[0084]

[0085]

[0086] Similarly, let Q be the first switch in the #3 energy storage module. 1_#3 The duty cycle of the drive signal is d 1_#3 Let Q be the third switch in the #2 energy storage module. 3_#3 The duty cycle of the drive signal is d 2_#3 We can obtain:

[0087]

[0088]

[0089]

[0090] Let d 1_#1 d 1_#2 d 1_#3 Both are d1, d 2_#1 d 2_#2 d 2_#3 Both are d2. Therefore, according to (4), (8), and (9), we can obtain:

[0091]

[0092] Similarly, according to (10), (11), and (12), we can obtain:

[0093]

[0094] From (9):

[0095]

[0096] Therefore, combining (16), (17), and (19), we can obtain:

[0097]

[0098] From (14), we can obtain:

[0099]

[0100] From (13), we can obtain:

[0101]

[0102] And from:

[0103]

[0104] The solution is:

[0105]

[0106] Similarly:

[0107]

[0108]

[0109] When the common duty cycle of each energy storage module in the energy storage system is controlled, the following can be obtained:

[0110]

[0111]

[0112] Substituting (26) and (27) into (23), (24), and (25), we get:

[0113]

[0114] Substituting (28) into (4), (10), and (13), we get:

[0115]

[0116] Furthermore, we can obtain:

[0117]

[0118] Further, we can obtain:

[0119]

[0120] Therefore, the voltage of all ports in the energy storage system can be self-balanced by controlling the common duty cycle of all energy storage modules.

[0121] The following section will provide a detailed analysis of some power conversion characteristics of the energy storage system, and will describe the operating mode in which the energy storage system supplies power to the power bus.

[0122] Let the total output current of the energy storage system be i. o Let the current in the first inductor of energy storage module #1 be i. L1_#1 Let the current in the second inductor of the #1 energy storage module be i. L2_#1 Let the current in the first inductor of energy storage module #2 be i. L1_#2 Let the current in the second inductor of energy storage module #1 be i. L2_#2 Let the current in the first inductor of energy storage module #1 be i. L1_#3 Let the current in the second inductor of energy storage module #1 be i. L2_#3 And based on the circuit connection method, we can obtain:

[0123]

[0124] Therefore, the total output power of the system is:

[0125]

[0126] The power after power conversion is v. c1_#1 v c2_#1 v c1_#2 v c2_#2 v c1_#3 v c2_#3 The power output from the port can be obtained as follows:

[0127]

[0128] Therefore, the equivalent power conversion level of the energy storage system can be obtained as follows:

[0129]

[0130] It is easy to see that α < 1, and no isolation components are introduced into the energy storage system, that is, the energy storage system realizes the power conversion of the non-isolated part.

[0131] This invention also provides a control system and control method for the above-described energy storage system. For example... Figure 4 and Figure 5 As shown, the control system provided in this embodiment of the invention includes:

[0132] Voltage and current sampling circuit, used to sample the first inductor current i of any four-port energy storage module. L1_#k Second inductor current i L2_#k and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0133] Error amplifier, used to calculate the first inductor current i L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Reference voltage v of the first energy storage unit s1_ref The reference voltage v of the second energy storage unit s2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0134] A PI controller is used to process the error signal err separately. iL1_#k err iL2_#k err v_#k A PI control is performed to implement dual-loop voltage and current control, obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0135] The PWM generator is used to generate PWM drive signals pwm1 and pwm3 for the first and third switching transistors respectively, based on the duty cycle signals d1 and d2 of the first and third switching transistors. It also generates PWM drive signals pwm2 for the second switching transistor (complementary to pwm1) and pwm4 for the fourth switching transistor (complementary to pwm3).

[0136] The signal amplifier is used to amplify the PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor, and then input them to the first, second, third, and fourth switches of all four-port energy storage modules.

[0137] This invention also provides a control method corresponding to the above-described control system, specifically including the following steps:

[0138] S1. Sample the first inductor current i in any four-port energy storage module. L1_#k Second inductor current i L2_#k and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0139] S2, Calculate the first inductor current i respectively. L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0140] S3, respectively, for the error signal err iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0141] S4. Based on the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch, generate the PWM drive signal pwm1 of the first switch and the PWM drive signal pwm3 of the third switch, respectively. Also generate the PWM drive signal pwm2 of the second switch, which is complementary to the PWM drive signal pwm1 of the first switch, and the PWM drive signal pwm4 of the fourth switch, which is complementary to the PWM drive signal pwm3 of the fourth switch.

[0142] S5. The PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor are amplified and then input to the first, second, third, and fourth switches of all four-port energy storage modules.

[0143] Considering the system's fault tolerance, such as Figure 6 As shown, this embodiment of the invention also provides another control system, including:

[0144] Voltage and current sampling circuit, used to sample the first inductor current i of all four-port energy storage modules. L1_#1 ~ i L1_#n Second inductor current i L2_#1 ~ i L2_#n The voltage v of the first energy storage unit s1_#1~ v s1_#n The voltage v of the second energy storage unit s2_#1 ~v s2_#n and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0145] The sampling signal analysis program is used to analyze the sampled voltage and current signals, determine whether the four-port energy storage module is normal, and disconnect abnormal four-port energy storage modules; and to set the first inductor current i of any normal four-port energy storage module. L1_#k Second inductor current i L2_#k and bus voltage v o Output to error amplifier;

[0146] Error amplifier, used to calculate the first inductor current i L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ;

[0147] A PI controller is used to process the error signal err separately. iL1_#k err iL2_#k Perform PI calculations to obtain the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch, respectively;

[0148] The PWM generator is used to generate PWM drive signals pwm1 and pwm3 for the first and third switching transistors respectively, based on the duty cycle signals d1 and d2 of the first and third switching transistors, and to generate PWM drive signals pwm2 and pwm4 for the second and fourth switching transistors respectively, which are complementary to the PWM drive signals pwm1 of the first and third switching transistors.

[0149] The signal amplifier is used to amplify the PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor, and then input them to the first, second, third, and fourth switches of all four-port energy storage modules.

[0150] This invention also provides a control method corresponding to the above-mentioned control system, comprising the following steps:

[0151] Sample the first inductor current i in all four-port energy storage modules L1_#1 ~ i L1_#n Second inductor current i L2_#1 ~i L2_#n and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ;

[0152] Analyze the sampled voltage and current signals to determine if the four-port energy storage module is functioning properly, and disconnect any abnormal four-port energy storage modules.

[0153] Calculate the first inductor current i of any normal four-port energy storage module. L1_#k Second inductor current i L2_#k And the bus voltage, and the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err vs1_#k err vs2_#k err v_#k ;

[0154] For the error signal err respectively iL1_#k err iL2_#k err v_#kPI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch.

[0155] Based on the duty cycle signals d1 and d2 of the first and third switching transistors, respectively, PWM drive signals pwm1 and pwm3 of the first and third switching transistors are generated. Additionally, PWM drive signals pwm2 and pwm4 of the second and fourth switching transistors, which are complementary to the PWM drive signal pwm1 of the first and third switching transistors, respectively, are also generated.

[0156] The PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor are amplified and then input to the first, second, third, and fourth switches of all four-port energy storage modules.

[0157] The technical solution described in this embodiment will be demonstrated below through a specific simulation and experimental waveform:

[0158] For the DC distributed power supply network, the output voltage of the proposed converter is connected to the LVDC bus. In this system, the voltage of each battery is 48V, the bus voltage is 60V, the maximum power is 10kW, the switching frequency of the switching transistor is 100kHz, the inductance value of each is 20uH, and the capacitance value of each is 100uF.

[0159] To better describe this invention, simulations based on SIMULNK were conducted, and the simulation results are as follows: Figure 7 and Figure 8 As shown, the inductor currents of the three energy storage modules are naturally balanced, and the voltages at each port are naturally balanced, indicating that the topology and control method provided by this invention are feasible.

[0160] To further describe the invention, a physical prototype was developed and manufactured, and photographs of the prototype are shown below. Figure 9 As shown. Each battery has a voltage of 48V, the bus voltage is 60V, the maximum power is 10kW, the switching frequency of the switching transistor is 100kHz, the inductance value of each is 20uH, the capacitance value of each is 100uF, the switching transistor model is HUF75652G3, and the controller model is TMS320F28035. The experimental results are as follows. Figures 10-11 As shown, the voltages at each port of the three energy storage modules are naturally balanced, the duty cycles of the switching transistors are consistent, and the phases of the driving signals can be inconsistent, indicating that the topology and control method provided by this invention are feasible.

[0161] It should be understood that the embodiments and descriptions above are only the principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A large-capacity energy storage system with arbitrarily expandable cascaded channel count, characterized in that: It includes n cascaded four-port energy storage modules. The k-th stage four-port energy storage module includes a first energy storage unit, a second energy storage unit, a first switching transistor, and a first switching transistor Q. 1_#k Second switch Q 2_#k The third switch Q 3_#k The fourth switch Q 4_#k First inductor L 1_#k Second inductor L 2_#k First capacitor C 1_#k With the second capacitor C 2_#k It is equipped with a positive external terminal V. +_#k Negative external terminal V -_#k First neutral terminal N 1_#k Second neutral terminal N 2_#k ; Among them, the positive external terminal V of the k-th stage four-port energy storage module +_#k Connected to the positive terminal V of the power bus + The negative external terminal V -_#k Connected to the negative terminal V of the power bus - The first neutral terminal N 1_#k The second neutral terminal V connected to the (k-1)th stage four-port energy storage module -_#k-1 The second neutral terminal N 2_#k The first neutral terminal N connected to the (k+1)th stage four-port energy storage module 1_#k+1 The second neutral terminal N of the last stage four-port energy storage module 2_#n The first neutral terminal N connected to the first stage four-port energy storage module 1_#1 ; The negative terminal of the first energy storage unit is connected to the negative external terminal V. -_#k The positive terminal is connected to the first neutral terminal N. 1_#k The positive terminal of the second energy storage unit is connected to the external positive terminal V. +_#k The negative electrode is connected to the first capacitor C. 1_#k Connected to the negative external terminal V -_#k The first neutral terminal N 1_#k via the first switching transistor Q 1_#k First inductor L 1_#k The third switch Q 3_#k Second inductor L 2_#k Connect to the second neutral terminal N 2_#k The second switch Q 2_#k One end is connected to the negative external terminal V. -_#k The other end is connected to the first switching transistor Q. 1_#k With the first inductor L 1_#k Between, the fourth switch Q 4_#k One end is connected to the positive external terminal V. +_#k The other end is connected to the third switch Q. 3_#k Second inductor L 2_#k Between, the second neutral terminal N 2_#k Through the second capacitor C 2_#k Connect to the positive external terminal V +_#k .

2. The large-capacity energy storage system with arbitrarily expandable cascaded channel number according to claim 1, characterized in that: The first switch Q 1_#k The drain is connected to the first neutral terminal N. 1_#k The source is connected to the second switch Q. 2_#k Drain and first inductor L 1_#k The first terminal, the second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k First inductor L 1_#k The second end is connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the third switch Q 3_#k The source, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k The third switch Q 3_#k The drains are connected to the fourth switching transistor Q. 4_#k Source and second inductor L 2_#k The first terminal, the fourth switch Q 4_#k Drain connected to positive terminal V +_#k Second inductor L 2_#k The second end is connected to the second neutral terminal N. 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

3. The large-capacity energy storage system with arbitrarily expandable cascaded channel number according to claim 1, characterized in that: The first inductor L 1_#k The first end is connected to the first neutral terminal N 1_#k The second end is connected to the first switching transistor Q. 1_#k Source and second switch Q 2_#k Drain, second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k The first switching transistor Q 1_#k The drains are connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the second inductor L 2_#k The first terminal, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k Second inductor L 2_#k The second end is connected to the fourth switch Q. 4_#k Source and third switch Q 3_#k Drain, fourth switch Q 4_#k Drain connected to positive terminal V +_#k The third switch Q 3_#k Source connected to the second neutral terminal N 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

4. The large-capacity energy storage system with arbitrarily expandable cascaded channel number according to claim 1, characterized in that: The k-th stage four-port energy storage module also includes a fifth switching transistor Q. 5_#k The sixth switch Q 6_#k The seventh switch Q 7_#k and the eighth switch Q 8_#k ; The first switch Q 1_#k The drain is connected to the first neutral terminal N. 1_#k The source is connected to the second switch Q. 2_#k Drain and first inductor L 1_#k The first terminal, the second switch Q 2_#k The source is connected to the external terminal V of the negative terminal. -_#k First inductor L 1_#k The second end is connected to the sixth switch Q. 5_#k Source and fifth switch Q 5_#k Drain, fifth switch Q 5_#k The source is connected to the external terminal V of the negative terminal. -_#k The sixth switch Q 6_#k The drains are connected to the first capacitor C. 1_#k The first terminal, the negative terminal of the second energy storage unit, and the third switch Q 3_#k The source, the first capacitor C 1_#k The second end is connected to the negative external terminal V. -_#k The third switch Q 3_#k The drains are connected to the fourth switching transistor Q. 4_#k Source and second inductor L 2_#k The first terminal, the fourth switch Q 4_#k Drain connected to positive terminal V +_#k Second inductor L 1_#k The second end is connected to the seventh switch Q. 7_#k Source and eighth switch Q 8_#k Drain, seventh switch Q 7_#k Drain connected to positive terminal V +_#k The eighth switch Q 8_#k Source connected to the second neutral terminal N 2_#k The second capacitor C 2_#k The first end is connected to the positive external terminal V. +_#k The second end is connected to the second neutral terminal N. 2_#k .

5. The large-capacity energy storage system with arbitrarily expandable cascaded channel number according to claim 1, characterized in that: The first energy storage unit and the second energy storage unit can be any type of bidirectional energy storage device.

6. The large-capacity energy storage system with arbitrarily expandable cascaded channel number according to claim 1, characterized in that: All switching transistors are arbitrary power semiconductor devices.

7. A control system for a large-capacity energy storage system with arbitrarily expandable cascaded channel number as described in any one of claims 1-6, characterized in that, include: Voltage and current sampling circuit, used to sample the first inductor current i of any four-port energy storage module. L1_#k Second inductor current i L2_#k and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ; Error amplifier, used to calculate the first inductor current i L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ; A PI controller is used to process the error signal err separately. iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch. The PWM generator is used to generate PWM drive signals pwm1 and pwm3 for the first and third switching transistors respectively, based on the duty cycle signals d1 and d2 of the first and third switching transistors, and to generate PWM drive signals pwm2 and pwm4 for the second and fourth switching transistors respectively, which are complementary to the PWM drive signals pwm1 of the first and third switching transistors. The signal amplifier is used to amplify the PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor, and then input them to the first, second, third, and fourth switches of all four-port energy storage modules.

8. A control system for a large-capacity energy storage system with arbitrarily expandable cascaded channel number as described in any one of claims 1-6, characterized in that, include: Voltage and current sampling circuit, used to sample the first inductor current i of all four-port energy storage modules. L1_#1 ~ i L1_#n Second inductor current i L2_#1 ~ i L2_#n The voltage v of the first energy storage unit s1_#1~ v s1_#n The voltage v of the second energy storage unit s2_#1 ~v s2_#n and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ; The sampling signal analysis program is used to analyze the sampled voltage and current signals, determine whether each four-port energy storage module is normal, disconnect abnormal four-port energy storage modules, and set the first inductor current i of any normal four-port energy storage module. L1_#k Second inductor current i L2_#k and bus voltage v o Output to error amplifier; Error amplifier, used to calculate the first inductor current i L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ; A PI controller is used to process the error signal err separately. iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch. The PWM generator is used to generate PWM drive signals pwm1 and pwm3 for the first and third switching transistors respectively, based on the duty cycle signals d1 and d2 of the first and third switching transistors, and to generate PWM drive signals pwm2 and pwm4 for the second and fourth switching transistors respectively, which are complementary to the PWM drive signals pwm1 of the first and third switching transistors. The signal amplifier is used to amplify the PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor, and then input them to the first, second, third, and fourth switches of all four-port energy storage modules.

9. A control method for a large-capacity energy storage system with arbitrarily expandable cascaded channel number as described in any one of claims 1-6, characterized in that, Includes the following steps: Sample the first inductor current i in any four-port energy storage module L1_#k Second inductor current i L2_#k and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ; Calculate the first inductor current i respectively L1_#k Second inductor current i L2_#k and bus voltage v o With the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ; For the error signal err respectively iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch. Based on the duty cycle signals d1 and d2 of the first and third switching transistors, respectively, PWM drive signals pwm1 and pwm3 of the first and third switching transistors are generated. Additionally, PWM drive signals pwm2 and pwm4 of the second and fourth switching transistors, which are complementary to the PWM drive signal pwm1 of the first and third switching transistors, respectively, are also generated. The PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor are amplified and then input to the first, second, third, and fourth switches of all four-port energy storage modules.

10. A control method for a large-capacity energy storage system with arbitrarily expandable cascaded channel number as described in any one of claims 1-6, characterized in that, Includes the following steps: Sample the first inductor current i in all four-port energy storage modules L1_#1 ~ i L1_#n Second inductor current i L2_#1 ~ i L2_#n The voltage v of the first energy storage unit s1_#1~ v s1_#n The voltage v of the second energy storage unit s2_#1 ~v s2_#n and the positive V of the power bus + With the negative terminal V of the power bus - Bus voltage v between o ; Analyze the sampled voltage and current signals to determine if the four-port energy storage module is functioning properly, and disconnect any abnormal four-port energy storage modules. Calculate the first inductor current i of any normal four-port energy storage module. L1_#k Second inductor current i L2_#k And the bus voltage, and the corresponding first inductor reference current i L1_ref Second inductor current i L2_ref Bus reference voltage v o_ref The error between them is used to obtain the corresponding error signal err. iL1_#k err iL2_#k err v_#k ; For the error signal err respectively iL1_#k err iL2_#k err v_#k PI control is performed to achieve dual-loop voltage and current control, thereby obtaining the duty cycle signal d1 of the first switch and the duty cycle signal d2 of the third switch. Based on the duty cycle signals d1 and d2 of the first and third switching transistors, respectively, PWM drive signals pwm1 and pwm3 of the first and third switching transistors are generated. Additionally, PWM drive signals pwm2 and pwm4 of the second and fourth switching transistors, which are complementary to the PWM drive signal pwm1 of the first and third switching transistors, respectively, are also generated. The PWM drive signals pwm1, pwm2, pwm3, and pwm4 of the first switch transistor are amplified and then input to the first, second, third, and fourth switches of all four-port energy storage modules.

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