Hybrid DC link energy storage converter and control method thereof

Abstract

Provided is a hybrid DC chain energy storage converter and a control method thereof. The hybrid DC chain energy storage converter comprises: a positive DC bus; a negative DC bus; a main circuit inductor; at least one high-frequency submodule, comprising a first switch circuit and a first capacitor connected in parallel; a plurality of low-frequency submodules, each comprising a second switch circuit and an energy storage element connected in parallel, the main circuit inductor, at least one high-frequency submodule and a plurality of low-frequency submodules are connected in series to form a series branch, and the series branch is respectively connected to the positive DC bus and the negative DC bus; a controller, coupled to the first switch circuit of at least one high-frequency submodule and the second switch circuits of the plurality of low-frequency submodules, respectively, for controlling the action of the first switch circuit of at least one high-frequency submodule according to the current of the main circuit inductor, and controlling the action of the second switch circuits of the plurality of low-frequency submodules according to the voltage of the first capacitor of at least one high-frequency submodule and the voltage of the plurality of energy storage elements.

Description

Technical Field

[0001] The present invention relates to the field of energy storage conversion, and in particular to a hybrid DC link type energy storage converter and a control method thereof. Background Art

[0002] In recent years, with the development of the energy storage industry, more and more energy storage projects have been put into use, and vigorously developing and safely using energy storage systems has gradually become a consensus.

[0003] However, because the existing energy storage systems have different modes such as large-scale centralized, distributed and mobile, there may still be some problems and defects in the energy storage systems.

[0004] For example, when a large number of battery cells are connected in series and parallel, the inconsistency of the battery cells will cause circulation loss and short-board effect between the battery cells; there are defects in the design of the thermal management system, which causes the battery performance in different temperature zones to decay at different rates, thus creating safety hazards; the timeliness of the safety warning is not high and there is a significant lag. When the system detects the abnormality, the battery thermal runaway reaction has already begun; the energy storage batteries are arranged in a centralized manner, making it impossible to bypass a single faulty battery, and local thermal runaway will spread rapidly, causing the fault to expand and cause a fire.

[0005] Therefore, it is necessary to ensure the safety of battery energy storage power stations during operation, eliminate circulation losses and short-board effects between battery cells, improve the design of thermal management systems, increase the timeliness of safety warnings, and effectively bypass faulty batteries.

[0006] When comparing the cycle efficiency of energy storage systems with different structures, it can be found that Figure 1A In the existing low-voltage DC chain energy storage system shown, the battery modules are distributed and connected to the DC low-voltage bus through the converter, which is beneficial to the system safety. However, the step-up transformer increases the system volume and cost, and the system efficiency is low after two-stage power conversion.

[0007] Compared with such a low-voltage DC chain energy storage system, the medium-voltage DC chain energy storage system can greatly improve the circulation efficiency from the power generation end to the energy storage end.

[0008] However, in Figure 1B In the existing cascaded H-bridge medium voltage AC direct connection solution shown, the battery full-bridge module is connected to the medium voltage AC grid through the cascaded battery full-bridge module, and the battery group control is beneficial to the system safety. However, the full-bridge module has a double power fluctuation, which has an adverse effect on the battery life.

[0009] At the same time, the existing commonly used constant current and constant voltage charging method is not conducive to the long-term cycle use of batteries. Although the pulse charging method can effectively reduce polarization and extend the cycle life, the pulse charging of a large number of batteries will cause an impact on the power grid and cannot be practical.

[0010] Research results in recent years have shown that hybrid DC link energy storage converters are more suitable for the development of modern urban distribution networks, but there is currently no mature technical solution to achieve the above functions. Summary of the invention

[0011] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a hybrid DC link energy storage converter that can solve the battery thermal management problem.

[0012] Another object of the present invention is to provide a hybrid DC link type energy storage converter that can solve the problem of low battery cycle efficiency.

[0013] The present invention also aims to provide a hybrid DC link energy storage converter that can solve the problems of battery life and rapid capacity decay.

[0014] The present invention also aims to provide a hybrid DC link energy storage converter that can solve the problem of pulse charging impacting the power grid.

[0015] In order to solve the above problems and other related problems, the hybrid DC link type energy storage converter of the present invention may include: a positive DC bus; a negative DC bus; a main circuit inductor; at least one high-frequency submodule, including a first switch circuit and a first capacitor, the first switch circuit being connected in parallel with the first capacitor; a plurality of low-frequency submodules, each of the low-frequency submodules including a second switch circuit and an energy storage element, the second switch circuit being connected in parallel with the energy storage element, the main circuit inductor, the at least one high-frequency submodule and the plurality of low-frequency submodules being connected in series to form a series branch, the series branch being respectively connected to the positive DC bus and the negative DC bus; and a controller, coupled to the first switch circuit of the at least one high-frequency submodule and the second switch circuit of the plurality of low-frequency submodules, respectively, for controlling the action of the first switch circuit of the at least one high-frequency submodule according to the current of the main circuit inductor, and controlling the action of the second switch circuit of the plurality of low-frequency submodules according to the voltage of the first capacitor of the at least one high-frequency submodule and the voltage of the plurality of energy storage elements.

[0016] Preferably, in the hybrid DC link energy storage converter, the first switching circuit may be a full-bridge circuit.

[0017] Preferably, in the hybrid DC link energy storage converter, the second switch circuit may be a half-bridge circuit or a full-bridge circuit. Specifically, the second switch circuit may be all half-bridge circuits, or all full-bridge circuits, or a part of the second switch circuit may be a half-bridge circuit and the other part may be a full-bridge circuit.

[0018] Preferably, in the hybrid DC link energy storage converter, each of the low-frequency submodules may further include a second capacitor; and the second capacitor is connected in parallel with the energy storage element.

[0019] Preferably, in the hybrid DC link energy storage converter, each of the low-frequency sub-modules may further include a module inductor, and the module inductor is respectively connected to the energy storage element and the second capacitor.

[0020] Preferably, in the hybrid DC link energy storage converter, all of the multiple energy storage elements may be battery packs, or a portion of the multiple energy storage elements may be battery packs and another portion may be supercapacitors.

[0021] Preferably, in the hybrid DC link energy storage converter, the plurality of low-frequency sub-modules may further include a bypass unit arranged at the input end thereof.

[0022] Preferably, the hybrid DC link energy storage converter may further include: an active front-end circuit, the input end of the active front-end circuit is coupled to the power grid, and the output end of the active front-end circuit is coupled to the positive DC bus and the negative DC bus.

[0023] Preferably, in the hybrid DC link energy storage converter, the controller may further include: an inductor current control unit, used to receive the current and current reference value of the main circuit inductor and output a first control signal to control the first switch circuit action of the at least one high-frequency sub-module; a capacitor voltage control unit, used to receive the voltage of the first capacitor and the first voltage reference value of the at least one high-frequency sub-module and output a modulation voltage; and a plurality of energy storage voltage control units, corresponding one-to-one to the plurality of low-frequency sub-modules, each of the energy storage voltage control units being used to receive the modulation voltage, the voltage of the energy storage element of the corresponding low-frequency sub-module and the second voltage reference value and output a second control signal to control the second switch circuit action of the corresponding low-frequency sub-module.

[0024] Preferably, in the hybrid DC link energy storage converter, a plurality of the second voltage reference values ​​are the same value.

[0025] Preferably, in the hybrid DC chain energy storage converter, the inductor current control unit may include a first operation unit, a current loop regulator and a first control signal generating unit; the first operation unit is used to receive the current of the main circuit inductor and the current reference value and calculate the current calculated value, the current loop regulator is used to receive the current calculated value and output a first voltage, and the first control signal generating unit is used to receive the first voltage and the first carrier signal and output the first control signal to control the first switching circuit action of the at least one high-frequency sub-module.

[0026] Preferably, in the hybrid DC chain energy storage converter, the capacitor voltage control unit may include a second operation unit and a capacitor voltage loop regulator; the second operation unit is used to receive the voltage of the first capacitor of the at least one high-frequency sub-module and the first voltage reference value and calculate the first voltage calculation value; the capacitor voltage loop regulator is used to receive the first voltage calculation value and output the modulation voltage.

[0027] Preferably, in the hybrid DC chain energy storage converter, the at least one high-frequency sub-module may include multiple high-frequency sub-modules; the second operation unit is used to receive the sum of the voltages of multiple first capacitors and the first voltage reference value and calculate the first voltage calculated value.

[0028] Preferably, in the hybrid DC chain energy storage converter, each of the energy storage voltage control units may include a third calculation unit, an energy storage voltage loop regulator, a fourth calculation unit, a fifth calculation unit and a second control signal generating unit; the third calculation unit is used to receive the voltage of the energy storage element corresponding thereto and the second voltage reference value and calculate the second voltage calculation value; the energy storage voltage loop regulator is used to receive the second voltage calculation value and output the second voltage, the fourth calculation unit receives the second voltage and the sign value of the current reference value and calculates the third voltage calculation value; the fifth calculation unit is used to receive the third voltage calculation value and the modulation voltage and calculates the fourth voltage calculation value; the second control signal generating unit is used to receive the fourth voltage calculation value and the second carrier signal and output the second control signal to control the second switching circuit action of the corresponding low-frequency sub-module.

[0029] To achieve the above-mentioned purpose and other related purposes, in the control method of the hybrid DC link type energy storage converter of the present invention, the hybrid DC link type energy storage converter may include: a positive DC bus; a negative DC bus; a main circuit inductor; at least one high-frequency submodule, including a first switch circuit and a first capacitor, the first switch circuit is connected in parallel with the first capacitor; and a plurality of low-frequency submodules, each of the low-frequency submodules includes a second switch circuit and an energy storage element, the second switch circuit is connected in parallel with the energy storage element, the main circuit inductor, the at least one high-frequency submodule and the plurality of low-frequency submodules are connected in series to form a series branch, and the series branch is respectively connected to the positive DC bus and the negative DC bus; the control method includes: controlling the first switch circuit action of the at least one high-frequency submodule according to the current of the main circuit inductor; and controlling the second switch circuit action of the plurality of low-frequency submodules according to the voltage of the first capacitor of the at least one high-frequency submodule and the voltage of the plurality of energy storage elements.

[0030] Preferably, the control method of the hybrid DC link energy storage converter may also specifically include: an inductor current control step, receiving the current and current reference value of the main circuit inductor and outputting a first control signal to control the action of the first switch circuit of the at least one high-frequency sub-module; a capacitor voltage control step, receiving the voltage and first voltage reference value of the first capacitor of the at least one high-frequency sub-module and outputting a modulation voltage; and a plurality of energy storage voltage control steps corresponding to the plurality of low-frequency sub-modules one by one, in each of the energy storage voltage control steps, receiving the modulation voltage, the voltage of the corresponding energy storage element and the second voltage reference value and outputting a second control signal to control the action of the second switch circuit of the corresponding low-frequency sub-module.

[0031] Preferably, in the control method of the hybrid DC link energy storage converter, in the inductor current control step, the current of the main circuit inductor and the current reference value are received by a first operation unit and a current calculation value is calculated, the current calculation value is received by a current loop regulator and a first voltage is output, and the first voltage and a first carrier signal are received by a first control signal generating unit and the first control signal is output, so as to control the action of the first switching circuit of the at least one high-frequency sub-module.

[0032] Preferably, in the control method of the hybrid DC chain energy storage converter, in the capacitor voltage control step, the voltage of the first capacitor of the at least one high-frequency sub-module and the first voltage reference value are received by the second operation unit and a first voltage calculation value is calculated, and the first voltage calculation value is received by the capacitor voltage loop regulator and the modulation voltage is output.

[0033] Preferably, in the control method of the hybrid DC link energy storage converter, in the capacitor voltage control step, the second operation unit may receive the sum of the voltages of the plurality of first capacitors and the first voltage reference value and calculate the first voltage calculated value.

[0034] Preferably, in the control method of the hybrid DC chain energy storage converter, in the energy storage voltage control step, the voltage of the corresponding energy storage element and the second voltage reference value are received by a third calculation unit and a second voltage calculation value is calculated, the second voltage calculation value is received by an energy storage voltage loop regulator and a second voltage is output, the second voltage and the sign value of the current reference value are received by a fourth calculation unit and a third voltage calculation value is calculated, the third voltage calculation value and the modulation voltage are received by a fifth calculation unit and a fourth voltage calculation value is calculated, the fourth voltage calculation value and a second carrier signal are received by a second control signal generating unit and the second control signal is output to control the second switching circuit action of the corresponding low-frequency sub-module.

[0035] As described above, in the hybrid DC link energy storage converter of the present invention, by grouping and packaging the batteries, the temperature of the battery pack can be controlled, and new and old batteries can be used in a cascade manner, thus solving the problem of battery thermal management.

[0036] In addition, in the hybrid DC chain energy storage converter of the present invention, by adopting the battery submodule cascade mode and directly connecting to the medium voltage DC distribution network, the conversion links are greatly reduced, the cycle efficiency is improved, and the problem of low battery cycle efficiency is solved.

[0037] In addition, in the hybrid DC chain energy storage converter of the present invention, the battery submodules are cascaded to output pulse power in turn, and the grid power is smooth and impact-free, thus solving the problem of pulse charging impacting the grid.

[0038] In addition, in the hybrid DC link energy storage converter of the present invention, by adopting a pulse charging method, the battery polarization effect is weakened, the battery service life is extended, and the problem of rapid battery life and capacity decay is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1A is a circuit diagram showing an existing low voltage DC chain energy storage system. Figure 1B It is a circuit diagram showing an existing cascaded H-bridge medium voltage AC direct connection solution.

[0040] Figure 2 1 is a circuit diagram showing a first embodiment of a hybrid DC link type energy storage converter according to the present invention.

[0041] Figure 3 is a circuit diagram showing a controller of a hybrid DC link type energy storage converter according to the present invention.

[0042] Figure 4 2 is a circuit diagram showing a second embodiment of the hybrid DC link type energy storage converter of the present invention.

[0043] Figure 5is a circuit diagram showing a third embodiment of the hybrid DC link type energy storage converter of the present invention.

[0044] Figure 6 is a circuit diagram showing a fourth embodiment of the hybrid DC link type energy storage converter of the present invention.

[0045] Figure 7 is a circuit diagram showing a fifth embodiment of the hybrid DC link type energy storage converter of the present invention.

[0046] Figure 8 is a circuit diagram showing a sixth embodiment of the hybrid DC link energy storage converter of the present invention.

[0047] Fig. 9 is a circuit diagram showing a seventh embodiment of the hybrid DC link energy storage converter of the present invention.

[0048] Fig.10 is a circuit diagram showing another controller of the hybrid DC link energy storage converter of the present invention.

[0049] Fig.11 (a) to (d) are simulation waveform diagrams of the hybrid DC link energy storage converter of the present invention. DETAILED DESCRIPTION

[0050] The embodiments disclosed in this specification are described in detail below with reference to the accompanying drawings. Here, the same reference numerals are assigned to the same or similar structural elements that are not related to the figure numerals, and repeated descriptions thereof will be omitted. The suffixes "component" and "part" used in the following description for structural elements are only assigned or mixed for the convenience of writing the specification, and they themselves do not have the meaning or function of dividing each other.

[0051] Furthermore, in the process of describing the embodiments disclosed in the present invention, if it is determined that the specific description of the related known technology will cause confusion with the technical ideas of the embodiments disclosed in this specification, the detailed description will be omitted. Furthermore, the attached drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in the present invention should not be limited by the attached drawings, but should cover all changes, equivalents and even substitutes included in the ideas and technical scope of the present invention.

[0052] Terms including ordinal numbers such as first and second can be used to describe various structural elements, but the structural elements are not limited by the terms. The terms are used only for the purpose of distinguishing one structural element from other structural elements.

[0053] If a structural element is mentioned as being "connected" or "contacting" another structural element, it may be directly connected to or in contact with the other structural element, but it can also be understood that there are other structural elements between them. Conversely, if a structural element is mentioned as being "directly connected" or "directly in contact with" another structural element, it should be understood that there are no other structural elements between them.

[0054] Unless the context clearly indicates otherwise, expressions in the singular shall include expressions in the plural.

[0055] In the present invention, terms such as "including" or "having" are only used to specify the existence of features, numbers, steps, actions, structural elements, parts or their combinations recorded in the specification, and are not intended to exclude the possibility of the existence or addition of one or more other features or numbers, steps, actions, structural elements, parts or their combinations.

[0056] Figure 2 1 is a circuit diagram showing a first embodiment of a hybrid DC link type energy storage converter according to the present invention.

[0057] The hybrid DC link type energy storage converter of the first embodiment of the present invention comprises: a positive DC bus U bus +; negative DC bus U bus -; Main circuit inductance L o At least one high frequency submodule (HFSM), including a first switch circuit and a first capacitor C f , the first switch circuit and the first capacitor C f Parallel connection; multiple low frequency sub modules (Low Frequency Sub Module, LFSM) LFSM1 to LFSM n , wherein n is a positive integer greater than 1, and each low-frequency submodule includes a second switch circuit and an energy storage element E bn , the second switch circuit and the energy storage element E bn Parallel connection, main circuit inductance L o , at least one high frequency submodule HFSM and low frequency submodules LFSM1 to LFSM n The series connection forms a series branch, which is connected to the positive DC bus U bus + and negative DC bus U bus The controller is coupled to the first switch circuit of the at least one high frequency submodule HFSM and the second switch circuits of the plurality of low frequency submodules LFSM, respectively, for controlling the inductance L of the main circuit according to the inductance L oThe current controls the first switch circuit action of the at least one high frequency submodule HFSM, and the first capacitor C of the at least one high frequency submodule f The voltage of the plurality of energy storage elements and the voltage of the plurality of energy storage elements control the actions of the second switch circuits of the plurality of low-frequency sub-modules LFSM.

[0058] In the hybrid DC link type energy storage converter of the present invention, at least one high frequency submodule HFSM may include a high frequency submodule HFSM1 (such as Figure 2 As shown), or may also include a plurality of high-frequency submodules HFSM1 to HFSM n .

[0059] In the hybrid DC link type energy storage converter of the present invention, the first switch circuit is a full bridge circuit. The high frequency submodule HFSM1 includes a full bridge circuit and a first capacitor C f , wherein the full-bridge circuit includes switch tubes S1, S2, S3 and S4 and diodes connected in anti-parallel to the switch tubes S1, S2, S3 and S4, respectively, the switch tubes S1 and S2 are connected in series to form a first bridge arm, the switch tubes S3 and S4 are connected in series to form a second bridge arm, the midpoint of the first bridge arm and the midpoint of the second bridge arm constitute the connection port of the high-frequency submodule HFSM1, the first bridge arm and the second bridge arm are respectively connected to the first capacitor C f Connect in parallel.

[0060] In the hybrid DC link type energy storage converter of the present invention, the plurality of energy storage elements E bn All of them can be battery packs, or multiple energy storage elements E bn One part is the battery pack and the other part is the supercapacitor.

[0061] In addition, in the hybrid DC link energy storage converter of the present invention, the second switch circuit is a half-bridge circuit or a full-bridge circuit. Specifically, the second switch circuit can be all half-bridge circuits, or all full-bridge circuits, or a part of the second switch circuit is a half-bridge circuit and the other part is a full-bridge circuit.

[0062] In the first embodiment of the present invention, all of the second switch circuits are half-bridge circuits. Figure 2 As shown, the low frequency submodule LFSM n It includes a half-bridge circuit and an energy storage element, wherein the half-bridge circuit includes a switch tube S n1 , S n2 And respectively with the switch tube S n1 , S n2 The diode connected in anti-parallel, the switch tube S n1 and S n2 are connected in series to form a bridge arm, the switch tube S n2The two ends of the bridge arm and the energy storage element E form the connection port of the low-frequency submodule. bn Connect in parallel.

[0063] In addition, in the first embodiment of the present invention, the low frequency submodule LFSM n Also includes a second capacitor C fn , the second capacitor C fn With energy storage element E bn The controller can control the second capacitor C through the second switch circuit. fn voltage.

[0064] Other low frequency submodules LFSM1 to LFSM n-1 It can also be used with the low frequency submodule LFSM n Same composition.

[0065] exist Figure 2 In the circuit, one HFSM and n LFSMs are connected in cascade with the main circuit inductor L o , and DC bus U bus In this embodiment, the controller is used to control the operation of the full-bridge circuit of the high-frequency submodule HFSM1, thereby controlling the main circuit inductance L o The current and the first capacitor C f The voltage of the first capacitor C f The current is a high-frequency square wave current with an average value of zero, and the connection port of the high-frequency submodule HFSM1 is a high-frequency square wave voltage with an average voltage of zero. Since the switches S1, S2, S3 and S4 of the full-bridge circuit are in a high-frequency switching state, the main circuit inductance L can be effectively controlled. o The current ripple is reduced, and the main circuit inductance L is reduced. o The controller is used to control the actions of the half-bridge circuits of multiple low-frequency sub-modules LFSM, such as adjusting the switching tube S n1 and S n2 The duty cycle of the switch tube S is equalized to balance the voltage of the energy storage elements of multiple low-frequency submodules LFSM. The inductor is omitted in the low-frequency submodule LFSM, which reduces the volume of the low-frequency submodule LFSM and reduces the cost of the hybrid DC link energy storage converter. In addition, in the half-bridge circuit, the switch tube S n1 and S n2 In the low-frequency switching state, the voltage at the connection port of the low-frequency submodule LFSM is a low-frequency square wave, which helps to reduce the switching tube S n1 and S n2The switching loss is reduced, which improves the efficiency of the hybrid DC link energy storage converter. The voltages of the connection ports of multiple low-frequency submodules LFSM are phase-shifted, and the voltage of the total port of the low-frequency submodule LFSM is a low-frequency square wave voltage with an average value of the DC bus voltage. The controller controls the half-bridge circuit to charge the energy storage element in a pulse charging manner, which reduces the battery polarization effect and prolongs the battery life.

[0066] Figure 3 is a circuit diagram showing a controller of a hybrid DC link type energy storage converter according to the present invention.

[0067] In the hybrid DC link type energy storage converter of the present invention, the controller may specifically include: an inductor current control unit 10, which is used to receive the main circuit inductance L o The current i Lo and current reference value i ref And output a first control signal to control the full bridge circuit action of the high frequency submodule HFSM1, wherein the current reference value i ref It can be a current instruction issued by a battery management system (Battery Management System, BMS); a capacitor voltage control unit 20, which is used to receive a first capacitor C of the high frequency submodule HFSM1 f The voltage u cf and the first voltage reference value u cref And output modulation voltage u c ; and the low frequency submodules LFSM1 to LFSM n One-to-one corresponding energy storage voltage control units 301 to 30 n , energy storage voltage control units 301 to 30 n Used to receive the modulation voltage u c , and its corresponding energy storage element E bn The voltage e bn and the second voltage reference value e bref And output a second control signal to control the low frequency submodules LFSM1 to LFSM n The half-bridge circuit action.

[0068] In addition, in the present invention, it should be noted that the energy storage voltage control units 301 to 30 n The second voltage reference value e bref can be the same or different. By setting the same second voltage reference value e bref , the circuit can be simplified. By setting different second voltage reference values ​​e bref , batteries can be used in a gradient manner and different types of recycled batteries can be connected.

[0069] exist Figure 3In the inductor current control unit 10 of the controller, the inductor current control unit 10 may further include a first operation unit (a portion surrounded by a dotted line frame) 11, a current loop regulator H iL and a first control signal generating unit (the part surrounded by a solid line frame) 12. The first operation unit 11 is used to receive the main circuit inductance L o The current i Lo and current reference value i ref And calculate the current value, the current loop regulator H iL Used to receive the current calculation value and output the first voltage u i , the first voltage u i is a modulated wave, the first control signal generating unit 12 is used to receive the first voltage u i and the first carrier signal u thf And output a first control signal to control the actions of the switch tubes S1 , S2 , S3 and S4 of the high frequency submodule HFSM1 .

[0070] exist Figure 3 In the capacitor voltage control unit 20 of the controller, the capacitor voltage control unit 20 may further include a second operation unit 21 (a portion surrounded by a dotted line frame) and a capacitor voltage loop regulator H cf The second operation unit 21 is used to receive the first capacitor C f The voltage u cf and the first voltage reference value u cref And calculate to obtain the first voltage calculation value, the capacitor voltage loop regulator H cf Used to receive the first voltage calculation value and output the modulation voltage u c .

[0071] exist Figure 3 The energy storage voltage control unit 301 to 30 of the controller n In the embodiment, the energy storage voltage control unit 30 may further include a third calculation unit (the portion surrounded by a dotted line frame) 31, an energy storage voltage loop regulator H eb , a fourth calculation unit 32, a fifth calculation unit 33 and a second control signal generating unit 34 (the part surrounded by a solid line frame). n For example, the third calculation unit 31 n Used to receive the corresponding energy storage element E bn The voltage e bn and the second voltage reference value e bref And calculate to obtain the second voltage calculation value, the energy storage voltage loop regulator H ebThe fourth calculation unit 32 is used to receive the second voltage calculation value and output the second voltage. n for receiving the second voltage and the current reference value i ref The symbol value Sign(i ref ) and calculate the third voltage calculated value u bn , the fifth calculation unit 33 n For receiving the third voltage calculated value u bn and the modulation voltage u c And calculate and obtain the fourth voltage calculation value u n , the fourth voltage calculated value u n is a modulated wave, the second control signal generating unit 34 n For receiving the fourth voltage calculated value u n and the second carrier signal u tlfn And output a second control signal to control the low frequency submodule LFSM n The switch tube S n1 , S n2 action.

[0072] Other low frequency submodules LFSM1 to LFSM n-1 One-to-one corresponding energy storage voltage control units 301 to 30 n-1 Can be used with low frequency submodule LFSM n Corresponding energy storage voltage control unit 30 n Have the same composition.

[0073] Similarly, the energy storage voltage loop regulator H of each energy storage voltage control unit 30 eb Can be the same or different.

[0074] Through the hybrid DC chain energy storage converter of the first embodiment of the present invention as described above, it can be seen that since the low-frequency submodule LFSM omits the module inductance, the module volume is reduced and the system cost is reduced. At the same time, since the switch tube of the second switch circuit of the low-frequency submodule LFSM is in a low-frequency state, the switching loss of the switch tube of the second switch circuit is reduced, and the efficiency of the hybrid DC chain energy storage converter is improved. Moreover, the second switch circuit of the low-frequency submodule LFSM provides a pulse charging method for the battery pack, which reduces the battery polarization effect and prolongs the battery life.

[0075] Moreover, the output port voltage of a single LFSM is a low-frequency square wave. The voltages of the connection ports of n low-frequency sub-modules LFSM are phase-shifted with each other, and the voltage of the total port of the low-frequency sub-module LFSM together is a low-frequency square wave voltage with an average value of the DC bus voltage, wherein the frequency of the low-frequency component in the DC bus voltage is n times the switching frequency of the switch tube of the second switch circuit, and the frequency of the high-frequency component is the switching frequency of the switch tube of the first switch circuit.

[0076] Figure 4 2 is a circuit diagram showing a second embodiment of the hybrid DC link type energy storage converter of the present invention.

[0077] and Figure 2 Different from the first embodiment, the second switching circuits are all half-bridge circuits. Figure 4 In the second embodiment, the second switch circuits of the low frequency submodule LFSM all use full bridge circuits to control the energy storage element E bn The full bridge circuit includes a switch tube S n1 , S n2 , S n3 and S n4 And respectively with the switch tube S n1 , S n2 , S n3 and S n4 The diode connected in anti-parallel, the switch tube S n1 and S n2 The first bridge arm is formed in series, and the switch tube S n3 and S n4 The first bridge arm and the second bridge arm are connected in series to form a second bridge arm, the midpoint of the first bridge arm and the midpoint of the second bridge arm constitute a connection port of the low-frequency submodule, and the first bridge arm and the second bridge arm are connected to the energy storage element E bn The use of the full-bridge circuit can have a switch tube (switch tube S n4 and / or S n1 ) short-circuit function, realize low-voltage ride-through of DC short circuit, and improve system reliability. The use of full-bridge circuit can also provide energy storage element E bn A positive and negative pulse charging method is provided to further extend the battery life. In some embodiments, the number of low-frequency submodules LFSM can be increased and a certain low-frequency submodule margin can be maintained so that the duty cycle of the battery pack pulse charging is maintained at an optimal level, thereby extending the battery life.

[0078] Figure 5 is a circuit diagram showing a third embodiment of the hybrid DC link type energy storage converter of the present invention.

[0079] and Figure 2 The second switching circuits of the first embodiment are all half-bridge circuits and Figure 4The second switching circuits of the second embodiment are all full-bridge circuits. Figure 5 In the third embodiment, a part of the second switch circuits in the low frequency submodule LFSM is a half-bridge circuit and another part is a full-bridge circuit. That is, the third embodiment is an embodiment in which the first embodiment and the second embodiment are combined.

[0080] In the third embodiment, by reasonably allocating the ratio of the half-bridge circuit to the full-bridge circuit in the low-frequency submodule LFSM, for example, about 50%, low voltage ride-through of a DC short circuit can still be achieved, thereby improving the reliability of the system.

[0081] Preferably, the full-bridge circuit can output a negative voltage to offset a portion of the positive voltage of the half-bridge circuit, thereby achieving the purpose of adjusting the duty cycle of the converter, thereby maintaining the battery pack pulse charging at an optimal duty cycle.

[0082] Figure 6 is a circuit diagram showing a fourth embodiment of the hybrid DC link type energy storage converter of the present invention.

[0083] like Figure 6 As shown, the hybrid DC chain energy storage converter of the fourth embodiment is applied to the constant current charging mode. Different from the pulse charging method provided in the first embodiment, the fourth embodiment can meet the constant current charging requirements of the battery. That is, the hybrid DC chain energy storage converter of the fourth embodiment can further include an inductor L in the low frequency submodule LFSM of the first embodiment. n , inductance L n Connect energy storage element E bn With the second capacitor C fn , ensuring the continuity of the current charging the battery pack.

[0084] Figure 7 is a circuit diagram showing a fifth embodiment of the hybrid DC link type energy storage converter of the present invention.

[0085] like Figure 7 As shown, in the hybrid DC link type energy storage converter of the fifth embodiment, the low frequency submodule LFSM further includes a bypass protection circuit arranged at the connection port of the second switch circuit thereof. For example, the bypass protection circuit may be a bypass switch. Figure 7 It is shown that a bypass protection circuit is added on the basis of the third embodiment, that is, bypass switches are respectively provided at the connection ports of the half-bridge circuit and the full-bridge circuit of the low-frequency submodule LFSM.

[0086] By further setting up a bypass protection circuit, in addition to the above functions, it is also possible to effectively bypass the faulty battery, realize the fault clearing function, and improve the system reliability.

[0087] Combination Figure 7, further illustrating the anti-short circuit function of the upper bridge arm switch tube mentioned in the second embodiment and the third embodiment.

[0088] exist Figure 7 In the case where the low-frequency submodule LFSM adopts a half-bridge circuit, if the switch tube S of the upper bridge arm 21 If a short circuit occurs, once the switch S of the lower bridge arm 22 If the bypass switch K1 is closed, the battery pack will be short-circuited, which is very dangerous. Therefore, it can be said that the half-bridge circuit does not have the function of resisting the short circuit of the switch tube of the upper bridge arm.

[0089] However, when the low-frequency submodule LFSM adopts a full-bridge circuit, if the switch tube S of the upper bridge arm n1 If a short circuit fault occurs, the bypass switch K2 is closed and the battery pack will not be in danger of short circuit. Therefore, the full-bridge circuit has the function of resisting short circuit of the switch tube of the upper bridge arm.

[0090] As described above, a part of the second switch circuit of the low frequency submodule LFSM adopts a full bridge circuit, which also has the function of resisting short circuit of the switch tube of the upper bridge arm, realizes low voltage ride through of DC short circuit, and improves the reliability of the system.

[0091] like Figure 7 As shown, when the second switch circuit of the low-frequency submodule LFSM adopts a half-bridge circuit, if the switch tube of the upper bridge arm (switch tube S 21 ) short-circuit fault occurs. Once the switch tube S of the lower bridge arm 22 If the bypass switch K1 is closed, the battery pack will be short-circuited, which is very dangerous. Therefore, it can be said that the half-bridge circuit does not have a switch tube (switch tube S 21 ) short-circuit function.

[0092] When the second switch circuit of the low-frequency submodule LFSM adopts a full-bridge circuit, if the switch tube of the upper bridge arm (switch tube S n3 and / or S n1 ) short-circuit fault occurs, and then the bypass switch K2 is closed, the battery pack will not be short-circuited, so the full-bridge circuit has an anti-upper arm switch tube (switch tube S n3 and / or S n1 ) short-circuit function.

[0093] As described above, a part of the second switch circuit of the low frequency submodule LFSM adopts a full bridge circuit, and also has a switch tube (switch tube S) for resisting the upper bridge arm. n3 and / or S n1 ) short-circuit function, realizing low-voltage ride-through of DC short circuit and improving the reliability of the system.

[0094] Figure 8is a circuit diagram showing a sixth embodiment of the hybrid DC link energy storage converter of the present invention.

[0095] like Figure 8 As shown, in the hybrid DC link type energy storage converter of the sixth embodiment, an active front-end circuit may also be included, the input end of the active front-end circuit may be coupled to the power grid, and the output end of the active front-end circuit may be coupled to the positive DC bus U bus + and negative DC bus U bus -. Thus, the hybrid DC link type energy storage converter of the present invention can be connected to a power grid.

[0096] Fig. 9 is a circuit diagram showing a seventh embodiment of the hybrid DC link energy storage converter of the present invention.

[0097] like Fig. 9 As shown, in the hybrid DC link type energy storage converter of the seventh embodiment, the at least one high frequency submodule HFSM includes a plurality of high frequency submodules HFSM1 and HFSM2, and the main circuit inductor L o , a plurality of high frequency submodules HFSM1 and HFSM2 and a plurality of low frequency submodules LFSM1 to LFSM n The series connection forms a series branch, and the series branch is respectively connected to the positive DC bus U bus + and the negative DC bus U bus -connection. The plurality of high frequency submodules HFSM1 and HFSM2 each include a first switch circuit and a first capacitor. The first switch circuit may be a full bridge circuit. The plurality of low frequency submodules LFSM1 to LFSM n All of the second switching circuits may include a second switching circuit and an energy storage element. All of the second switching circuits may be full-bridge circuits, or all of the second switching circuits may be half-bridge circuits, or a portion of all of the second switching circuits may be full-bridge circuits and another portion may be half-bridge circuits. All of the energy storage elements may be battery packs, or a portion of all of the energy storage elements may be battery packs and another portion may be supercapacitors. In some embodiments, the plurality of low-frequency submodules LFSM1 to LFSM n Each may include a second capacitor, wherein the second capacitor is connected in parallel with the energy storage element.

[0098] Fig.10 is a circuit diagram showing another controller of the hybrid DC link energy storage converter of the present invention.

[0099] In the hybrid DC link type energy storage converter of the present invention, the controller may specifically include: an inductor current control unit 10', which is used to receive the main circuit inductance L o The current i Lo and current reference value i refAnd output a plurality of first control signals to respectively control the first switch circuit actions of the high frequency submodules HFSM1 and HFSM2. The plurality of first control signals may be the same, wherein the current reference value i ref It can be a current instruction issued by a battery management system (Battery Management System, BMS); a capacitor voltage control unit 20', which is used to receive the first capacitor C of the high-frequency sub-module HFSM1 and HFSM2 f The voltage u cf The sum of the voltage and the first voltage reference value u cref And output modulation voltage u c , wherein the first voltage reference value is Figure 3 The first voltage reference value in the low frequency submodules LFSM1 to LFSM n One-to-one corresponding energy storage voltage control units 301 ' to 30 n ', energy storage voltage control unit 301' to 30 n 'Used to receive the modulation voltage u c , and its corresponding energy storage element E bn The voltage e bn and the second voltage reference value e bref And output a second control signal to control the low frequency submodules LFSM1 to LFSM n The half-bridge circuit operates.

[0100] In addition, in the present invention, it should be noted that the energy storage voltage control units 301 'to 30 n The second voltage reference value e in ' bref can be the same or different. By setting the same second voltage reference value e bref , the circuit can be simplified. By setting different second voltage reference values ​​e bref , batteries can be used in a gradient manner and different types of recycled batteries can be connected.

[0101] Fig.11 (a) to (d) are simulation waveform diagrams showing the hybrid DC link type energy storage converter of the present invention. Fig.11 It can be seen from the simulation waveform shown in (a) that the charging current waveforms of the four battery packs are phase-shifted with each other, and the battery pack achieves pulse charging, with a current ripple of 1% during charging. Fig.11 As can be seen from the simulation waveform shown in (b), the capacitor voltage waveform in the high-frequency submodule HFSM1 is stable, and the voltage ripple is 0.83%. Fig.11 It can be seen from the simulation waveform shown in (c) that the main circuit inductance L o The current is stably controlled and the current ripple is 5%. Fig.11From the simulation waveform shown in (d), it can be seen that the voltage waveform of the battery pack in the low-frequency submodule LFSM is stable, and the voltage ripple is 0.42%. Therefore, the hybrid DC link energy storage converter can work stably and has good control performance.

[0102] As described above, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0103] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A hybrid DC link energy storage converter, characterized in that: include: Positive DC bus; Negative DC bus; Main circuit inductance; at least one high-frequency submodule, comprising a first switch circuit and a first capacitor, wherein the first switch circuit is connected in parallel with the first capacitor; A plurality of low-frequency submodules, each of which comprises a second switch circuit and an energy storage element, wherein the second switch circuit is connected in parallel with the energy storage element; the main circuit inductor, the at least one high-frequency submodule and the plurality of low-frequency submodules are connected in series to form a series branch, and two ends of the series branch are respectively connected to the positive DC bus and the negative DC bus; as well as A controller is coupled to the first switch circuit of the at least one high-frequency sub-module and the second switch circuit of the multiple low-frequency sub-modules, respectively, and is used to control the action of the first switch circuit of the at least one high-frequency sub-module according to the current of the main circuit inductor, and to control the action of the second switch circuit of the multiple low-frequency sub-modules according to the voltage of the first capacitor of the at least one high-frequency sub-module and the voltage of the multiple energy storage elements.

2. The hybrid DC link type energy storage converter according to claim 1, characterized in that: The first switching circuit is a full-bridge circuit.

3. The hybrid DC link type energy storage converter according to claim 1, characterized in that: The second switching circuit is a half-bridge circuit or a full-bridge circuit.

4. The hybrid DC link type energy storage converter according to claim 3, characterized in that: Each of the low-frequency sub-modules further includes a second capacitor, which is connected in parallel with the energy storage element.

5. The hybrid DC link type energy storage converter according to claim 4, characterized in that: Each of the low-frequency submodules further includes a module inductor, Two ends of the module inductor are connected to the energy storage element and the second capacitor respectively.

6. The hybrid DC link type energy storage converter according to claim 1, characterized in that: All of the multiple energy storage elements are battery packs, or some of the multiple energy storage elements are battery packs and the other parts are supercapacitors.

7. The hybrid DC link type energy storage converter according to claim 1, characterized in that: The plurality of low-frequency sub-modules further include a bypass unit arranged at the input end thereof.

8. The hybrid DC link type energy storage converter according to claim 1, characterized in that: Also includes: An active front-end circuit, wherein an input end of the active front-end circuit is coupled to a power grid, and an output end of the active front-end circuit is coupled to the positive DC bus and the negative DC bus.

9. The hybrid DC link type energy storage converter according to claim 1, characterized in that: The controller comprises: an inductor current control unit, configured to receive the current and the current reference value of the main circuit inductor and output a first control signal to control the action of the first switch circuit of the at least one high-frequency submodule; a capacitor voltage control unit, configured to receive the voltage of the first capacitor of the at least one high-frequency submodule and a first voltage reference value and output a modulation voltage; and Multiple energy storage voltage control units correspond one-to-one to the multiple low-frequency sub-modules, and each of the energy storage voltage control units is used to receive a modulation voltage, the voltage of the energy storage element of the corresponding low-frequency sub-module, and a second voltage reference value and output a second control signal to control the action of the second switch circuit of the corresponding low-frequency sub-module.

10. The hybrid DC link type energy storage converter according to claim 9, characterized in that: The plurality of second voltage reference values ​​are the same value.

11. The hybrid DC link type energy storage converter according to claim 9, characterized in that: The inductor current control unit includes a first operation unit, a current loop regulator and a first control signal generating unit; The first operation unit is used to receive the current of the main circuit inductor and the current reference value and calculate the current calculation value. The current loop regulator is used to receive the current calculation value and output a first voltage, The first control signal generating unit is used to receive the first voltage and the first carrier signal and output the first control signal to control the action of the first switch circuit of the at least one high-frequency sub-module.

12. The hybrid DC link type energy storage converter according to claim 9, characterized in that: The capacitor voltage control unit includes a second operation unit and a capacitor voltage loop regulator; The second operation unit is used to receive the voltage of the first capacitor of the at least one high-frequency sub-module and the first voltage reference value and calculate to obtain a first voltage calculation value; The capacitor voltage loop regulator is used to receive the first voltage calculation value and output the modulation voltage.

13. The hybrid DC link type energy storage converter according to claim 12, characterized in that: The at least one high frequency submodule includes a plurality of high frequency submodules; The second operation unit is used to receive the sum of the voltages of the plurality of first capacitors and the first voltage reference value and calculate the first voltage calculation value.

14. The hybrid DC link type energy storage converter according to claim 9, characterized in that: Each of the energy storage voltage control units includes a third calculation unit, an energy storage voltage loop regulator, a fourth calculation unit, a fifth calculation unit and a second control signal generating unit; The third calculation unit is used for receiving the voltage of the energy storage element corresponding thereto and the second voltage reference value and calculating and obtaining a second voltage calculation value; The energy storage voltage loop regulator is used to receive the second voltage calculation value and output a second voltage, The fourth calculation unit receives the second voltage and the sign value of the current reference value and calculates to obtain a third voltage calculation value; The fifth calculation unit is used for receiving the third voltage calculation value and the modulation voltage and calculating to obtain a fourth voltage calculation value; The second control signal generating unit is used to receive the fourth voltage calculation value and the second carrier signal and output the second control signal to control the action of the second switch circuit of the corresponding low-frequency sub-module.

15. A control method for a hybrid DC link energy storage converter, characterized in that: The hybrid DC link type energy storage converter comprises: Positive DC bus; Negative DC bus; Main circuit inductance; at least one high-frequency submodule, comprising a first switch circuit and a first capacitor, wherein the first switch circuit is connected in parallel with the first capacitor; and A plurality of low-frequency submodules, each of which comprises a second switch circuit and an energy storage element, the second switch circuit is connected in parallel with the energy storage element, the main circuit inductor, the at least one high-frequency submodule and the plurality of low-frequency submodules are connected in series to form a series branch, and two ends of the series branch are respectively connected to the positive DC bus and the negative DC bus; The control method comprises: Controlling the operation of the first switch circuit of the at least one high-frequency submodule according to the current of the main circuit inductor; and The second switch circuits of the plurality of low-frequency sub-modules are controlled to operate according to the voltage of the first capacitor of the at least one high-frequency sub-module and the voltage of the plurality of energy storage elements.

16. The control method of the hybrid DC link energy storage converter according to claim 15, characterized in that: The control method comprises: an inductor current control step, receiving the current and current reference value of the main circuit inductor and outputting a first control signal to control the action of the first switch circuit of the at least one high-frequency submodule; a capacitor voltage control step, receiving the voltage of the first capacitor of the at least one high-frequency submodule and a first voltage reference value and outputting a modulation voltage; and A plurality of energy storage voltage control steps corresponding one to the plurality of low-frequency sub-modules, in each of the energy storage voltage control steps, receiving the modulation voltage, the voltage of the corresponding energy storage element and a second voltage reference value and outputting a second control signal to control the action of the second switch circuit of the corresponding low-frequency sub-module.

17. The control method of the hybrid DC link type energy storage converter according to claim 16, characterized in that: In the inductor current control step, the current of the main circuit inductor and the current reference value are received by a first operation unit to calculate a current calculation value, the current calculation value is received by a current loop regulator and a first voltage is output, and the first voltage and a first carrier signal are received by a first control signal generating unit and the first control signal is output to control the action of the first switch circuit of the at least one high-frequency sub-module.

18. The control method of the hybrid DC link energy storage converter according to claim 16, characterized in that: In the capacitor voltage control step, the voltage of the first capacitor of the at least one high-frequency sub-module and the first voltage reference value are received by the second operation unit to calculate a first voltage calculation value, and the first voltage calculation value is received by the capacitor voltage loop regulator and the modulation voltage is output.

19. The control method of the hybrid DC link energy storage converter according to claim 18, characterized in that: In the capacitor voltage control step, the second operation unit receives the sum of the voltages of the plurality of first capacitors and the first voltage reference value and calculates and obtains the first voltage calculation value.

20. The control method of the hybrid DC link energy storage converter according to claim 16, characterized in that: In the energy storage voltage control step, the voltage of the corresponding energy storage element and the second voltage reference value are received by the third calculation unit to calculate the second voltage calculation value, the second voltage calculation value is received by the energy storage voltage loop regulator and the second voltage is output, the second voltage and the sign value of the current reference value are received by the fourth calculation unit and the third voltage calculation value is calculated, the third voltage calculation value and the modulation voltage are received by the fifth calculation unit and the fourth voltage calculation value is calculated, the fourth voltage calculation value and the second carrier signal are received by the second control signal generating unit and the second control signal is output to control the second switch circuit action of the corresponding low-frequency sub-module.

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