Energy storage valve sub-module and high-pressure direct-hanging energy storage system

Abstract

The invention relates to an energy storage valve sub-module and a high-voltage direct-hanging energy storage system, a suppression circuit of underdamped oscillation is added in the energy storage valve sub-module, the suppression circuit is connected in series with a direct-current support capacitor, and a resistance-capacitance branch formed by connecting the suppression circuit and the direct-current support capacitor in series is connected in parallel with a power conversion unit and an energy storage unit. The suppression circuit can suppress the under-damped oscillation current generated by the energy storage valve sub-module at the switching state switching moment by adjusting the resistance value of the impedance in the energy storage valve sub-module, so that the under-damped oscillation current generated by the energy storage valve sub-module at the switching state switching moment is reduced; therefore, the damage of the underdamped oscillation current to the energy storage valve sub-module is reduced, and the reliability of the energy storage valve sub-module is improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to an energy storage valve submodule and a high-pressure direct-mounted energy storage system. Background Art

[0002] With the development of large-scale energy storage, high-voltage direct-mounted energy storage systems have gradually been widely used.

[0003] In the related art, the high-voltage direct-mounted energy storage system includes a plurality of cascaded energy storage valve submodules, each of which includes an energy storage unit. When used, the charging and discharging of the energy storage unit in each energy storage valve submodule can be achieved by controlling the switching state of each energy storage valve submodule.

[0004] However, in the related art, the reliability of the energy storage valve submodule is low. Summary of the invention

[0005] Based on this, it is necessary to provide an energy storage valve submodule and a high-pressure direct-mounted energy storage system to address the above-mentioned technical problems, which can improve the reliability of the energy storage valve submodule.

[0006] In a first aspect, an embodiment of the present application provides an energy storage valve submodule, which includes a power conversion unit, a DC support capacitor, a suppression circuit and an energy storage unit. The suppression circuit and the DC support capacitor are connected in series to form a resistor-capacitor branch, and the resistor-capacitor branch is respectively connected in parallel with the power conversion unit and the energy storage unit.

[0007] The energy storage valve submodule provided in the embodiment of the present application adds an under-damped oscillation suppression circuit in the energy storage valve submodule, the suppression circuit is connected in series with the DC support capacitor, and the resistance-capacitance branch formed by the suppression circuit and the DC support capacitor in series is respectively connected in parallel with the power conversion unit and the energy storage unit. Since the suppression circuit can suppress the under-damped oscillation current generated by the energy storage valve submodule at the switching state switching moment by adjusting the resistance value of the impedance in the energy storage valve submodule, the under-damped oscillation current generated by the energy storage valve submodule at the switching state switching moment is greatly reduced, thereby achieving the effect of suppressing the under-damped oscillation current, so that the harm caused by the under-damped oscillation current to the energy storage valve submodule is greatly reduced, thereby improving the reliability of the energy storage valve submodule.

[0008] In one embodiment, the suppression circuit includes a resistive element.

[0009] In the embodiment of the present application, the suppression circuit is realized by a resistor element, so that the resistor element provides the resistance required to suppress the under-damped oscillating current generated by the energy storage valve submodule at the time of input. This is not only highly economical but also convenient and simple, and greatly reduces the additional impact on the overall function of the energy storage valve submodule, thereby further improving the reliability of the energy storage valve submodule.

[0010] In one embodiment, the suppression circuit further includes a switch circuit connected in parallel with the resistance element.

[0011] In the embodiment of the present application, a switch circuit is connected in parallel next to the resistance element, and the opening and closing of the switch circuit is used to realize whether the resistance element is in the energy storage valve submodule or is cut out. Only when it is put into operation in the energy storage valve submodule can the under-damped oscillation generated at the time of input under the corresponding state of the energy storage unit be suppressed, thereby improving the suppression accuracy of the under-damped oscillation of the energy storage valve submodule.

[0012] In one embodiment, the resistance element includes a first resistor and a second resistor connected in series, and the switch circuit also includes a first switch and a second switch, the first switch is connected in parallel with the first resistor, and the second switch is connected in parallel with the second resistor.

[0013] In the embodiment of the present application, two resistors are added to the energy storage valve submodule, and then two different switches are added to control the switching states of the two resistors in the energy storage valve submodule respectively. Only one of the two resistors is switched on when the energy storage unit is in the charging state or when the energy storage unit is in the discharging state. On this basis, the resistance values ​​of the two resistors are different, so that the degree of underdamped oscillation that can be suppressed when the energy storage unit is in the charging state or when the energy storage unit is in the discharging state is also different. In this way, the suppression of underdamped oscillation of the energy storage unit in different charging and discharging states is more accurate.

[0014] In one embodiment, the first switch and / or the second switch is a diode.

[0015] In the embodiment of the present application, a diode is used to implement the first switch and the second switch. Since the diode does not need to be controlled and relies on the voltage in the circuit to switch between the on and off states, it has the advantages of fast switching speed and extremely short switching time, so that the switching state of the resistance element can be quickly and accurately controlled, thereby achieving a more accurate effect of suppressing the under-damped oscillation of the energy storage unit in different charging and discharging states.

[0016] In one embodiment, the resistance of the first resistor is greater than the resistance of the second resistor.

[0017] In the embodiment of the present application, by setting the resistance value of the first resistor to be greater than the resistance value of the second resistor, the under-damped oscillating current generated when the energy storage unit is in the charging state can be suppressed to a greater extent, and the degree of suppression of the under-damped oscillating current generated when the energy storage unit is in the discharging state can be less. In this way, by setting the first resistor and the second resistor to different resistance values, the under-damped oscillating current generated when the energy storage unit is in the charging state and the discharging state can be suppressed differently, so as to improve the suppression accuracy of the under-damped oscillation of the energy storage valve submodule.

[0018] In the embodiment of the present application, by setting the resistance value of the first resistor to be greater than the resistance value of the second resistor, the under-damped oscillating current generated when the energy storage unit is in the charging state can be suppressed to a greater extent, and the degree of suppression of the under-damped oscillating current generated when the energy storage unit is in the discharging state can be less. In this way, by setting the first resistor and the second resistor to different resistance values, the under-damped oscillating current generated when the energy storage unit is in the charging state and the discharging state can be suppressed differently, so as to improve the suppression accuracy of the under-damped oscillation of the energy storage valve submodule.

[0019] In one embodiment, the resistance element includes a third resistor and a fourth resistor connected in parallel with each other, and the switch circuit also includes a third switch and a fourth switch, the third switch is connected in series with the third resistor, and the fourth switch is connected in series with the fourth resistor.

[0020] In the embodiment of the present application, two resistors are added to the energy storage valve submodule, and then two different switches are added to control the switching states of the two resistors in the energy storage valve submodule respectively. Only one of the two resistors is switched on when the energy storage unit is in the charging state or when the energy storage unit is in the discharging state. On this basis, the resistance values ​​of the two resistors are different, so that the degree of underdamped oscillation that can be suppressed when the energy storage unit is in the charging state or when the energy storage unit is in the discharging state is also different. In this way, the suppression of underdamped oscillation of the energy storage unit in different charging and discharging states is more accurate.

[0021] In one embodiment, the third switch and / or the fourth switch is a diode.

[0022] In the embodiment of the present application, diodes are used to implement the third switch and the fourth switch. Since the diodes do not need to be controlled and rely on the voltage in the circuit to switch between the on and off states, they have the advantages of fast switching speed and extremely short switching time, so that the switching state of the resistance element can be quickly and accurately controlled, thereby achieving a more accurate effect of suppressing the under-damped oscillation of the energy storage unit in different charging and discharging states.

[0023] In one embodiment, the resistance of the third resistor is greater than the resistance of the fourth resistor.

[0024] In the embodiment of the present application, by setting the resistance value of the third resistor to be greater than the resistance value of the fourth resistor, the under-damped oscillating current generated when the energy storage unit is in the charging state can be suppressed to a greater extent, and the degree of suppression of the under-damped oscillating current generated when the energy storage unit is in the discharging state can be less. In this way, by setting the third resistor and the fourth resistor to different resistance values, the under-damped oscillating current generated when the energy storage unit is in the charging state and the discharging state can be suppressed differently, so as to improve the suppression accuracy of the under-damped oscillation of the energy storage valve submodule.

[0025] In one embodiment, the resistance value of the resistor element ranges from 10 mΩ to 500 mΩ.

[0026] In an embodiment of the present application, the value range of the resistance element is set to 10mΩ-500mΩ, so that the resistance element matches the capacitance of the DC support capacitor in the high-voltage direct-mounted energy storage system scenario, the inductance of the equivalent stray inductance in the energy storage unit, and the resistance of the equivalent internal resistance in the energy storage unit, thereby accurately suppressing the under-damped oscillation of the energy valve sub-module in the high-voltage direct-mounted energy storage system scenario.

[0027] In one embodiment, the energy storage valve submodule further includes a buffer capacitor, which is connected in parallel with the resistor-capacitor branch.

[0028] In the embodiment of the present application, a buffer capacitor is connected in parallel next to the RC branch as a whole, so that the overvoltage stress of the power device in the power conversion unit at the time of shutdown can be reduced. In this way, the risk of failure of the power device in the power conversion unit due to excessive overvoltage stress is reduced, thereby increasing the working reliability of the power device in the power conversion unit, and further increasing the working reliability of the energy storage valve submodule.

[0029] In one embodiment, the capacitance of the buffer capacitor is smaller than the capacitance of the DC link capacitor.

[0030] In the embodiment of the present application, by setting the capacitance of the buffer capacitor to be smaller than the capacitance of the DC support capacitor, a certain distinction is made between the high-frequency current passed by the buffer capacitor and the high-frequency current passed by the DC support capacitor when the energy storage valve submodule is put into operation. And because the capacitance of the buffer capacitor is much smaller than the capacitance of the DC support capacitor, the degree of under-damped oscillation of the energy storage valve submodule aggravated by the excessive capacitance of the buffer capacitor is reduced, so that the overvoltage stress at the time of shutting off the power device in the power conversion unit is reduced while reducing the risk of generating additional impacts, thereby increasing the working reliability of the energy storage valve submodule.

[0031] In one embodiment, the capacitance range of the buffer capacitor includes 10uF to 300uF.

[0032] In the embodiment of the present application, the capacitance range of the buffer capacitor includes 10uF to 300uF. This can not only reduce the overvoltage stress of the power device in the power conversion unit at the time of shutdown in the high-voltage direct-mounted energy storage scenario, but also reduce the additional impact on the overall topology of the energy storage valve sub-module, thereby increasing the working reliability of the energy storage valve sub-module.

[0033] In one embodiment, the energy storage valve submodule further includes a bypass circuit, and the bypass circuit is connected in parallel with the energy storage valve submodule.

[0034] In the embodiment of the present application, a bypass circuit is provided between the ports at which the energy storage valve submodule is connected to the main circuit of the high-voltage direct-hung energy storage system, so that in the event of a failure in the energy storage valve submodule, the energy storage valve submodule can be cut out of the high-voltage direct-hung energy storage system, thereby improving the operating stability and safety of the high-voltage direct-hung energy storage system.

[0035] In one embodiment, the switching frequency of the energy storage valve submodule is positively correlated with the energy loss generated by the suppression circuit.

[0036] The embodiment of the present application sets the equivalent switching frequency of the energy storage valve submodule when it is switched on and off in the high-voltage direct-hung energy storage system through the characteristic that the switching frequency of the energy storage valve submodule is positively correlated with the energy loss generated by the suppression circuit, so that the energy storage valve submodule can be switched on and off at a lower equivalent switching frequency, thereby reducing the loss of the energy storage valve submodule and improving the economy and safety of the application of the energy storage valve submodule.

[0037] In one embodiment, the turn-off current change rate of the power device in the power conversion unit is inversely correlated with the parameter value of the driving device in the driving circuit of the power device.

[0038] In the embodiment of the present application, by virtue of the characteristic that the turn-off current change rate of the power device in the power conversion unit is inversely correlated with the parameter value of the driving device in the driving circuit of the power device, it is possible to reduce the turn-off current change rate of the power device in the power conversion unit, thereby further reducing the turn-off overvoltage of the power device in the power conversion unit, and greatly reducing the problem of failure of the power device in the power conversion unit due to excessive overvoltage stress, thereby increasing the working reliability of the power conversion unit.

[0039] In one embodiment, the parameter value of the driving device includes the resistance value of the gate turn-off resistor in the driving circuit and / or the capacitance value of the gate capacitor in the driving circuit.

[0040] In a second aspect, an embodiment of the present application provides a high-pressure direct-hung energy storage system, which includes an energy storage valve submodule provided in any embodiment of the first aspect above.

[0041] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the architecture of a high-voltage direct-mounted energy storage system in an embodiment;

[0043] Figure 2A topological schematic diagram of an energy storage valve submodule in an embodiment;

[0044] Figure 3 A schematic diagram of equivalent stray inductance and equivalent internal resistance of an energy storage unit in an energy storage valve submodule in one embodiment;

[0045] Figure 4 A topological schematic diagram of an energy storage valve submodule in another embodiment;

[0046] Figure 5 A topological schematic diagram of an energy storage valve submodule in another embodiment;

[0047] Figure 6 Schematic diagram of the implementation structure of the power conversion unit in the energy storage valve submodule in one embodiment;

[0048] Figure 7 A schematic diagram of the implementation structure of a power conversion unit in an energy storage valve submodule in another embodiment;

[0049] Figure 8 Schematic diagram of the implementation structure of the suppression circuit in the energy storage valve submodule in one embodiment;

[0050] Fig. 9 It is a schematic diagram of an equivalent network after a suppression circuit is added to the energy storage valve submodule in one embodiment;

[0051] Fig.10 It is a schematic diagram of the implementation structure of the suppression circuit in the energy storage valve submodule in another embodiment;

[0052] Fig.11 is a schematic diagram of the implementation structure of a switch circuit in an inhibition circuit in an embodiment;

[0053] Fig.12 It is a schematic diagram of the implementation structure of the suppression circuit in the energy storage valve submodule in another embodiment;

[0054] Fig.13 It is a schematic diagram of the implementation structure of the suppression circuit in the energy storage valve submodule in another embodiment;

[0055] Fig.14 A schematic diagram of a structure in which a buffer capacitor is added to an energy storage valve submodule in one embodiment;

[0056] Fig.15 is a schematic diagram of a driving circuit of a power device in a power conversion unit in one embodiment;

[0057] Fig.16 It is a schematic diagram of the structure of adding a bypass circuit in the energy storage valve submodule in one embodiment.

[0058] Description of reference numerals:

[0059] 10: Power conversion unit;

[0060] 20: DC support capacitor;

[0061] 30: Energy storage unit;

[0062] 40: Inhibition circuit;

[0063] 401: resistance element;

[0064] 402: switch circuit;

[0065] 50: buffer capacitor;

[0066] 60: Bypass circuit. DETAILED DESCRIPTION

[0067] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and any variations thereof in the specification and claims of the present application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions. In the description of the embodiments of the present application, the technical terms "first", "second", "third", "fourth", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0069] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0070] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "connection" should be understood in a broad sense, for example, it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0071] The high-voltage direct-mounted energy storage system is a new type of energy storage system. It uses modular multi-level cascade technology to cascade multiple energy storage valve submodules, which can simultaneously realize AC / DC power conversion and energy storage. It has the advantages of high modularity and good harmonic characteristics. Therefore, it is increasingly widely used in power grids. Each energy storage valve submodule in the high-voltage direct-mounted energy storage system includes an energy storage unit, and the energy storage unit includes a battery pack. In practical applications, the energy storage units in each energy storage valve submodule can be charged and discharged by controlling the cascaded energy storage valve submodules.

[0072] Figure 1 The following is a schematic diagram of a high-voltage AC direct-mounted energy storage system architecture, taking a direct-mounted energy storage system of three-phase grids A, B, and C as an example. Figure 1 As shown, the high-voltage direct-hung energy storage system includes a three-phase energy storage cascade chain of A, B, and C, and each phase energy storage cascade chain includes a bridge arm reactor and m energy storage modules. Among them, the energy storage modules on the three-phase energy storage cascade chain are represented by SM1#m, SM2#m, and SM3#m, respectively, and m is 1, 2, 3, ..., n. In other embodiments, such as a high-voltage direct-hung energy storage system, the three-phase alternating current can also be converted into direct current by a converter valve, the energy storage valve can be directly hung on the DC power grid, and the energy storage valve can include multiple energy storage valve submodules, etc.

[0073] In the related art, the topology of the energy storage valve submodule in the high-pressure direct-mounted energy storage system is as follows: Figure 2 As shown, it includes a power conversion unit 10, a DC support capacitor 20 and an energy storage unit 30, wherein: Figure 2 S1 and S2 in the figure represent two connection ports. Each energy storage valve submodule needs to be connected to the main circuit of the high-voltage direct-mounted energy storage system through the two connection ports S1 and S2, so as to be connected to the high-voltage power grid through the main circuit. The connection relationship here can be seen in Figure 1 S1 and S2 in .

[0074] Usually, there is a large equivalent internal resistance and equivalent stray inductance inside the energy storage unit, which comes not only from the connection bar inside the energy storage unit, but also from the bus bar connecting the energy storage unit and the power conversion unit in the entire energy storage valve submodule topology. Figure 2After the connection is shown in the schematic diagram, the equivalent resistance and equivalent stray inductance inside the energy storage unit and the DC support capacitor are equivalent to a parallel RLC network. The energy storage valve module in the entire high-voltage direct-mounted energy storage system has two modes: the on-state and the off-state. When the energy storage valve module is switched to the on-state, the current on the main circuit of the high-voltage direct-mounted energy storage system enters the energy storage valve module. This current can be regarded as a step current source excitation for the RLC network. Please refer to Figure 3 , Figure 3 is a schematic diagram of a parallel RLC network equivalent to the topology of the energy storage valve submodule, where L represents the equivalent stray inductance, Rdc represents the equivalent internal resistance, I / P represents the step current source excitation, and Figure 3 The power conversion unit in the energy storage valve submodule is not shown.

[0075] Due to the large equivalent stray inductance, the inductive reactance of the equivalent stray inductance L in the energy storage valve submodule does not match the capacitive reactance of the DC support capacitor. In this case, once under the step current source excitation I / P, the mismatch between the inductive reactance of the equivalent stray inductance L and the capacitive reactance of the DC support capacitor will cause the entire RLC network to have an underdamped oscillation, forming an underdamped network, thereby causing the DC support capacitor and the energy storage unit to have an underdamped oscillation.

[0076] The underdamped oscillation may cause certain harm to the energy storage valve submodule, including but not limited to overcurrent of the energy storage unit, resulting in damage, degradation and reduced life of the energy storage unit; and the capacitor current in the energy storage valve submodule increases, for example, it can increase by about 30%, which will increase the weight, volume and cost of the capacitor; and if the energy storage valve submodule is in an overcurrent state for a long time during operation, it will also cause greater current stress on the electrical components in the energy storage valve submodule, etc., thereby affecting the working reliability of the energy storage valve submodule.

[0077] This problem can be solved by increasing the capacitance of the capacitor in the energy storage valve submodule, reducing the stray inductance, increasing the resistance, etc. However, considering that the main source of the equivalent stray inductance in the energy storage unit is the connecting bar inside the energy storage unit and the busbar connecting the energy storage unit and the power conversion unit, it is difficult to reduce it. Moreover, the equivalent internal resistance in the energy storage unit mainly comes from the internal resistance of a large number of internal series-parallel cells. The resistance value of this equivalent internal resistance is relatively low, which makes the equivalent internal resistance fluctuate greatly with the charging and discharging frequency. Therefore, this equivalent internal resistance is not enough to smooth out under-damped oscillations. If resistance is added to the main circuit of the high-voltage direct-mounted energy storage system, since the charging and discharging current of the energy stored in the high-voltage direct-mounted energy storage system is as high as thousands of amperes, even increasing the resistance by milliohms will cause huge losses, thereby causing a substantial temperature rise, which will affect the heat dissipation design and life of the energy storage unit. If the oscillation is suppressed by increasing the capacitance of the capacitor in the energy storage valve sub-module, the capacitance of the capacitor needs to be increased to several hundred mF, and the increase in the capacitance of the capacitor is accompanied by a corresponding increase in the volume, weight and cost of the capacitor, resulting in a certain impact on the applicability and convenience of the energy storage valve sub-module.

[0078] Based on the above considerations, it is currently impossible to suppress under-damped oscillations by adjusting the parameters in the energy storage valve submodule. Based on this, the embodiment of the present application improves the topology of the energy storage valve submodule, adds an under-damped oscillation suppression circuit in the energy storage valve submodule, and suppresses the under-damped oscillation current generated by the entire energy storage valve submodule at the switching state, so that the under-damped oscillation current generated by the energy storage valve submodule at the switching state can be greatly reduced, achieving the effect of suppressing the under-damped oscillation current, so that the harm caused by the under-damped oscillation current to the energy storage valve submodule is greatly reduced, thereby improving the reliability of the energy storage valve submodule.

[0079] The detailed implementation process of the energy storage valve submodule provided by the present application is described below through specific embodiments. Figure 4 As shown, a topological schematic diagram of an energy storage valve submodule is provided in an embodiment of the present application. The energy storage valve submodule includes a power conversion unit 10, a DC support capacitor 20, a suppression circuit 40 and an energy storage unit 30, wherein the suppression circuit 40 and the DC support capacitor 20 are connected in series to form a resistance-capacitance branch, and the resistance-capacitance branch is connected in parallel with the power conversion unit 10 and the energy storage unit 30 respectively.

[0080] In the embodiment of the present application, a suppression circuit 40 is connected in series to the branch where the DC support capacitor 20 is located in the energy storage valve submodule to form a resistance-capacitance branch, which is connected in parallel with the power conversion unit 10 and the energy storage unit 30. It can be understood that Figure 4 This is just an example of one connection method. In some scenarios, the RC branch can also be connected in the following way. Figure 5 Connect as shown.

[0081] In the energy storage valve submodule, the power conversion unit 10 mainly realizes the two working modes of the energy storage unit 30 in the charging and discharging state through different paths. The power conversion unit 10 can be realized by a half-bridge circuit composed of power semiconductor devices, a full-bridge circuit composed of power semiconductor devices, a quasi-full-bridge circuit composed of power semiconductor devices, and so on.

[0082] In one embodiment, Figure 6 As shown, a method for implementing a power conversion unit 10 is illustrated. It should be noted that: Figure 6 The drawings of the subsequent embodiments of the present application will be Figure 4 The connection method is shown as the basis. Figure 6 The diagram shows a half-bridge circuit composed of power semiconductor devices, wherein T1 and T2 are both power devices, for example, they can be implemented by insulated gate bipolar transistors (IGBT).

[0083] In another embodiment, Figure 7 As shown, another implementation of the power conversion unit 10 is illustrated. Figure 7 The diagram shows a full-bridge circuit, in which T1, T2, T3 and T4 are all power devices, and can also be implemented by IGBTs.

[0084] In addition, taking the IGBT as an example, since the IGBT is a switch tube, Figure 6 and Figure 7 The gate of the IGBT is connected to a driving circuit, which is mainly used to drive the IGBT to turn on and off. However, in order to highlight the key points, the embodiment of the present application does not illustrate the driving circuit connected to the gate of the IGBT.

[0085] In actual operation, the energy storage unit 30 in the energy storage valve submodule is divided into an input mode and a cut-off mode in a charging state, and an input mode and a cut-off mode in a discharging state. Figure 6 Take the above-mentioned working principle in the input mode and the cut-off mode as an example, and combine the circuit schematic diagram to explain, as follows:

[0086] (1) The energy storage unit 30 is in the charging state in the input mode: In this mode, the T2 tube is turned off, and the D2 and T1 tubes are also not turned on due to the reverse voltage. Then, the current on the main circuit of the high-voltage direct-hung energy storage system enters the energy storage unit 30 from the S1 port through D1 and then flows out through the S2 port to form a loop, so that the energy storage unit 30 can be charged.

[0087] (2) Cut-off mode when the energy storage unit 30 is in the charging state: In this mode, the T2 tube is turned on. Since the voltage drop across the tube T2 is very low when it is turned on, the current in the main circuit will directly flow through T2 and then out of the S2 port after entering the S1 port to form a loop, cutting off the energy storage unit 30 from the main circuit and no longer charging. At this time, because there is voltage on the energy storage unit 30, D1 is clamped by the reverse voltage and is in the cut-off state.

[0088] (3) The energy storage unit 30 is in the discharging state in the input mode: In this mode, the T2 tube, D2 and D1 are not conducting, while the T1 tube is conducting. Then, the current on the main circuit of the high-voltage direct-hung energy storage system directly enters the energy storage unit 30 from the S2 port, passes through the T1 tube, and then flows out from the S1 port to form a loop, so that the energy storage unit 30 is in the discharging state.

[0089] (4) Cut-off mode in which the energy storage unit 30 is in a discharging state: In this mode, the T2 tube, D2 and T1 are all off, and the current on the main circuit of the high-voltage direct-hung energy storage system enters from the S2 port through D2 and directly flows out from the S1 port to form a loop, completely cutting off the energy storage unit 30 from the main circuit and no longer discharging.

[0090] Based on the working principle of the power conversion unit 10, it can be known that the reason why it is mentioned above that when the energy storage valve submodule is switched in the switching state, the current on the main circuit of the high-voltage direct-mounted energy storage system enters the energy storage valve submodule, and this current can be regarded as a step current source excitation for the entire energy storage valve submodule, is that when the energy storage valve submodule is switched in the switching state, it needs to be realized by turning on or off the IGBT in the power conversion unit 10, and the speed of turning on or off the IGBT is extremely fast. Therefore, after the IGBT is turned on, the current pouring in from the main circuit forms a step current source excitation. Under this step current source excitation, the mismatch between the capacitive reactance of the DC support capacitor 20 and the inductive reactance of the equivalent stray inductance in the energy storage valve submodule causes the energy storage valve submodule to oscillate underdamped when the switching state is switched. Then to suppress this underdamped oscillation, it is necessary to minimize the mismatch between the capacitive reactance of the DC support capacitor 20 and the inductive reactance of the equivalent stray inductance, that is, in essence, to suppress the underdamped oscillation current generated by the energy storage valve submodule.

[0091] Since the functions of the DC support capacitor 20 in the energy storage valve submodule include but are not limited to filtering high-frequency harmonics during IGBT switching, constructing a power device commutation circuit, etc., it is an indispensable key part of the energy storage valve submodule, and the equivalent stray inductance is also caused by the indispensable energy storage unit 30 in the energy storage valve submodule, so the capacitive reactance and inductive reactance cannot be adjusted as mentioned in the above embodiment of the present application. The impedance of the RLC network equivalent to the DC support capacitor 20 and the energy storage unit 30 has resistance in addition to the reactance composed of capacitive reactance and inductive reactance. Therefore, the embodiment of the present application adjusts the resistance in the impedance value of the RLC network by adding a suppression circuit 40, so that the RLC network is in an over-damped state, suppressing the under-damped oscillation phenomenon of the RLC network, thereby suppressing the under-damped oscillation current.

[0092] Optionally, the suppression circuit 40 may include a resistor element. That is, the suppression circuit 40 in the embodiment of the present application may be implemented by a resistor element. The resistor element provides the resistance required to suppress the under-damped oscillating current generated by the energy storage valve submodule at the time of input, which is not only highly economical and easy to use, but also greatly reduces the additional impact on the overall function of the energy storage valve submodule.

[0093] In practical applications, the resistance element in the embodiment of the present application can be realized by any device with resistance through any connection method, for example, it can be realized by a resistor, or it can be realized by some passive devices with resistance, etc.

[0094] The energy storage valve submodule provided in the embodiment of the present application adds an under-damped oscillation suppression circuit in the energy storage valve submodule, the suppression circuit is connected in series with the DC support capacitor, and the resistance-capacitance branch formed by the suppression circuit and the DC support capacitor in series is respectively connected in parallel with the power conversion unit and the energy storage unit. Since the suppression circuit can suppress the under-damped oscillation current generated by the energy storage valve submodule at the switching state switching moment by adjusting the resistance value of the impedance in the energy storage valve submodule, the under-damped oscillation current generated by the energy storage valve submodule at the switching state switching moment is greatly reduced, thereby achieving the effect of suppressing the under-damped oscillation current, so that the harm caused by the under-damped oscillation current to the energy storage valve submodule is greatly reduced, thereby improving the reliability of the energy storage valve submodule.

[0095] like Figure 8 As shown, the embodiment of the present application takes the above-mentioned resistor element as an example to explain in detail the implementation method of the above-mentioned suppression circuit 40. For the convenience of illustration, Figure 8 In the example of the resistor element 401, the under-damping state of the entire energy storage valve submodule is changed by adding the resistor element 401 to the branch of the DC support capacitor 20 to suppress the under-damping oscillation current. In practical applications, the resistor element 401 can be set according to requirements, and can include a single resistor, or a series-parallel combination of multiple resistors.

[0096] Regardless of the implementation method of the suppression circuit 40, if the under-damped oscillating current generated by the energy storage valve submodule at the switching state is to be suppressed by adjusting the resistance value of the impedance in the energy storage valve submodule, it is necessary to accurately design the resistance value of the resistor element 401. The resistance value of the resistor element 401 needs to be able to make the current generated in the entire network at the switching state of the energy storage valve submodule not exceed the tolerance current of the energy storage unit 30, so that the entire network can be in a critical damping or over-damping state.

[0097] like Fig. 9 As shown, Fig. 9 To combine the above Figure 3 and the above Figure 8 Schematic diagram of the equivalent network after the damping resistor is connected in series in the energy storage valve submodule.

[0098] According to Kirchhoff's current law and Kirchhoff's voltage law, Fig. 9 The equivalent network of is used to establish the model and the following second-order differential equation can be obtained:

[0099]

[0100] In the above second-order differential equation, L represents the equivalent stray inductance value of the energy storage unit 30, C represents the capacitance value of the DC support capacitor 20, and R c represents the resistance value of the resistor element 401 in the suppression circuit 40, R 1 represents the resistance value of the equivalent internal resistance Rdc of the energy storage unit 30, u c represents the voltage on the DC support capacitor 20. Naturally, represents the current on the DC support capacitor 20, i s It represents the current entering the energy storage unit 30 when the energy storage valve submodule is put into operation. OCV represents the starting voltage on the DC support capacitor 20 of the energy storage valve submodule under steady-state conditions. Since the energy storage valve submodule is in a steady state before the step current on the main circuit enters the energy storage valve submodule, the capacitor does not pass DC in this steady state, which is equivalent to an open circuit. Therefore, OCV can be understood as the voltage on the energy storage unit 30.

[0101] Solving the above second-order differential equation, the general solution of the characteristic equation is:

[0102] LcP 2 +(R C +R 1 )Cp+1=0 Formula 2

[0103] Wherein, Formula 2 is a homogeneous equation, and p represents the Therefore, according to Formula 2, the resistance value of the resistor element 401 is related to the capacitance value of the DC support capacitor 20 in the energy storage valve submodule, the inductance value of the equivalent stray inductance L in the energy storage valve submodule, and the resistance value of the equivalent internal resistance Rdc in the energy storage valve submodule.

[0104] That is, based on the specific values ​​of the capacitance of the DC support capacitor 20 in the energy storage valve submodule, the inductance of the equivalent stray inductance L of the energy storage unit 30 in the energy storage valve submodule, and the resistance of the equivalent internal resistance Rdc of the energy storage unit 30 in the actual application, the resistance value of the resistor element 401 can be calculated by substituting them into the above formula 2.

[0105] For example, in the high-voltage direct-mounted energy storage system scenario, if the capacitance of the DC support capacitor 20 is in the mF level, the inductance of the equivalent stray inductance L in the energy storage unit 30 is in the μH level, and the resistance of the equivalent internal resistance Rdc in the energy storage unit 30 is in the mΩ to 10mΩ level. And under this condition, if the entire network of the energy storage valve submodule is required to be in an overdamped state at the time of switching mode switching, then combined with the above formula 2, the resistance range of the resistor element 401 can be between 10mΩ-500mΩ. For example, the resistance of the resistor element 401 can be 50mΩ, 100mΩ, 150mΩ, etc., which are not listed here one by one, as long as they are within the value range.

[0106] In an embodiment of the present application, the value range of the resistance element is set to 10mΩ-500mΩ, so that the resistance element matches the capacitance of the DC support capacitor, the inductance of the equivalent stray inductance in the energy storage unit, and the resistance of the equivalent internal resistance in the energy storage unit in the high-voltage direct-hung energy storage system scenario, thereby accurately suppressing the under-damped oscillation of the energy valve sub-module in the high-voltage direct-hung energy storage system scenario.

[0107] In the embodiment of the present application, based on Kirchhoff's current law and Kirchhoff's voltage law in the energy storage valve submodule, a second-order differential equation of the topological network model of the energy storage valve submodule is constructed, and the second-order differential equation is solved to obtain the functional relationship between the equivalent stray inductance of the energy storage unit, the equivalent internal resistance of the energy storage unit, the DC support capacitor and the resistance element, and then the capacitance of the DC support capacitor, the equivalent stray inductance value of the energy storage unit, and the equivalent internal resistance value of the energy storage unit in actual application are substituted into the functional relationship for solution to obtain the resistance value of the resistance element. Since it is a second-order differential equation constructed based on the energy storage valve submodule with the addition of the resistance element, the second-order differential equation can accurately reflect the characteristics of the entire topology of the energy storage valve submodule, so that the resistance value of the resistance element can be accurately calculated, thereby effectively suppressing the under-damped oscillating current generated in the energy storage valve submodule.

[0108] In addition, considering that the under-damped oscillation current in the energy storage valve submodule may be generated not only when the energy storage unit 30 is put into the charging state, but also when the energy storage unit 30 is put into the discharging state, a method is provided in the embodiment of the present application to achieve accurate suppression of the under-damped oscillation of the energy storage unit 30 in different charging and discharging states.

[0109] like Fig.10 As shown, in one embodiment, the suppression circuit 40 further includes a switch circuit 402 , and the switch circuit 402 is connected in parallel with the resistance element 401 .

[0110] The function of the switch circuit 402 is to control the switching state of the resistor element 401 in the energy storage valve submodule. That is, by connecting the switch circuit 402 in parallel with the resistor element 401, when the energy storage unit 30 is in the charging state, the switch circuit 402 is disconnected to put the resistor element 401 in the switching state; when the energy storage unit 30 is in the discharging state, the switch circuit 402 is turned on to put the resistor element 401 in the switching-out state.

[0111] When the resistor element 401 is in the on state, the switch circuit 402 is disconnected, and in this case the current on the main circuit will pass through the resistor element 401 to suppress the under-damped oscillating current generated when the energy storage unit 30 is in the charging state. Similarly, when the resistor element 401 is in the off state, the switch circuit 402 is turned on, and in this case the current on the main circuit will pass through the switch circuit 402, which is equivalent to almost no current passing through the resistor element 401, which is short-circuited by the switch circuit 402, so that in this case the under-damped oscillating current generated when the energy storage unit 30 is in the discharging state is not suppressed.

[0112] like Fig.11 As shown, the suppression circuit 40 is illustrated by taking the switch circuit 402 as a diode as an example. The switching characteristics of the diode make the diode in the off state when the energy storage unit 30 is in the charging state, so the current of the main circuit can only pass through the resistor element 401 at the time of input, and when the energy storage unit 30 is in the discharging state, the diode is in the on state, the resistor element 401 is short-circuited, and the current in the main circuit flows directly through the diode at the time of input. The diode is used to implement the switching circuit. The diode does not need to be controlled. It relies on the voltage in the circuit to switch between the on and off states. It has the advantages of fast switching speed and very short switching time, so that the switching state of the resistor element can be quickly and accurately controlled, thereby achieving a more accurate effect of suppressing the underdamped oscillation of the energy storage unit in different states of charging and discharging.

[0113] In the embodiment of the present application, a switch circuit is connected in parallel next to the resistance element, and the opening and closing of the switch circuit is used to realize whether the resistance element is in the energy storage valve submodule or is cut out. Only when it is put into operation in the energy storage valve submodule can the under-damped oscillation generated at the time of input under the corresponding state of the energy storage unit be suppressed, thereby improving the suppression accuracy of the under-damped oscillation of the energy storage valve submodule.

[0114] The above is an embodiment of realizing precise suppression of under-damped oscillations in different charging and discharging processes of the energy storage unit 30 by using a resistor in the resistor element 401 and a switch in the switch circuit 402. Precise suppression of under-damped oscillations in different charging and discharging processes of the energy storage unit 30 can also be realized by using multiple resistors in the resistor element 401 and multiple switches in the switch circuit 402.

[0115] In one embodiment, if Fig.12 As shown, the resistor element 401 includes a first resistor R1 and a second resistor R2 connected in series, and the switch circuit 402 also includes a first switch D5 and a second switch D6, the first switch D5 is connected in parallel with the first resistor R1, and the second switch D6 is connected in parallel with the second resistor R2. Optionally, the first switch D5 and / or the second switch D6 are diodes.

[0116] For ease of explanation, Fig.12 The first switch is a diode D5, the second switch is a diode D6, the first resistor is R1, and the second resistor is R2. It should be noted that in actual applications, the first switch D5 and the second switch D6 are both diodes, or one of the first switch D5 and the second switch D6 can be a diode.

[0117] Same principle as above, Fig.12 In the embodiment, when the energy storage unit 30 is in the charging state, once the energy storage valve submodule is put into operation, the first switch D5 is reversely cut off and the second switch D6 is forwardly turned on. The current in the main circuit passes through the first resistor R1 and then passes through the second switch D6. In this case, it is equivalent to that only the first resistor R1 is in the put-in state, and the second resistor R2 is cut out. Therefore, the first resistor R1 can suppress the under-damped oscillation current generated when the energy storage unit 30 is in the charging state.

[0118] When the energy storage unit 30 is in a discharging state, once the energy storage valve submodule is put into operation, the first switch D5 is forward-conducted and the second switch D6 is reversely turned off, and the current in the main circuit passes through the second resistor R2 and then through the first switch D5. In this case, it is equivalent to that only the second resistor R2 is in the engaged state, and the first resistor R1 is cut out, so the second resistor R2 can suppress the under-damped oscillating current generated when the energy storage unit 30 is in a discharging state.

[0119] Based on the above working process, according to actual needs, for example, the degree of under-damped oscillating current generated when the energy storage unit 30 is in the charging state is greater than the under-damped oscillating current generated when the energy storage unit 30 is in the discharging state, and the under-damped oscillating current generated when the energy storage unit 30 is in the charging state is set to be suppressed to a greater extent, while the degree of suppression of the under-damped oscillating current generated when the energy storage unit 30 is in the discharging state can be smaller. Based on this, in one embodiment, the first resistor R1 is greater than the second resistor R2, that is, the larger the resistance value, the stronger the degree of suppression of the under-damped oscillating current, so that by setting the first resistor R1 and the second resistor R2 to different resistance values, the under-damped oscillating current generated when the energy storage unit 30 is in the charging state and the discharging state is suppressed differently, so as to improve the accuracy of suppressing the under-damped oscillation of the energy storage valve submodule.

[0120] In one embodiment, Fig.13 As shown, the resistor element 401 includes a third resistor R3 and a fourth resistor R4 connected in parallel, and the switch circuit 402 also includes a third switch D7 and a fourth switch D8, the third switch D7 is connected in series with the third resistor R3, and the fourth switch D8 is connected in series with the fourth resistor R4. Optionally, the third switch D7 and / or the fourth switch D8 are diodes.

[0121] Again, for ease of illustration, Fig.13 In the figure, the third switch is a diode D7, the fourth switch is a diode D8, the third resistor is R3, and the fourth resistor is R4. It should be noted that: Fig.13 The second resistor R4 can also be interchanged with the fourth switch D8, and the two methods are substantially equivalent. As described above, in actual applications, the third switch D7 and the fourth switch D8 are both diodes, or one of the third switch D7 and the fourth switch D8 can be a diode.

[0122] Same principle as above, Fig.13 In the embodiment, when the energy storage unit 30 is in the charging state, once the energy storage valve submodule is put into operation, the third switch D7 is forward-conducted and the fourth switch D8 is reversely turned off, and the current in the main circuit passes through the third resistor R3 and then flows out through the third switch D7. In this case, it is equivalent to that only the third resistor R3 is in the put-in state, and the fourth resistor R4 is cut out, so the third resistor R3 can suppress the under-damped oscillation current generated when the energy storage unit 30 is in the charging state.

[0123] When the energy storage unit 30 is in the discharging state, once the energy storage valve submodule is put into operation, the third switch D7 is reversely cut off and forwardly conducted, and the current in the main circuit passes through the fourth switch D8 and then flows out through the fourth resistor R4. In this case, it is equivalent to that only the fourth resistor R4 is in the put-in state, and the third resistor R3 is cut out, so the fourth resistor R4 can suppress the under-damped oscillation current generated at the time when the energy storage unit 30 is in the discharging state.

[0124] Based on the above working process, according to actual needs, for example, the degree of under-damped oscillating current generated when the energy storage unit 30 is in the charging state is greater than the under-damped oscillating current generated when the energy storage unit 30 is in the discharging state, and the under-damped oscillating current generated when the energy storage unit 30 is in the charging state is set to be suppressed to a greater extent, while the degree of suppression of the under-damped oscillating current generated when the energy storage unit 30 is in the discharging state can be smaller. Based on this, in one embodiment, the third resistor R3 is greater than the fourth resistor R4, that is, the greater the resistance value, the stronger the degree of suppression of the under-damped oscillating current, so that by setting the third resistor R3 and the fourth resistor R4 to different resistance values, the under-damped oscillating current generated when the energy storage unit 30 is in the charging state and the discharging state is suppressed differently, so as to improve the accuracy of suppressing the under-damped oscillation of the energy storage valve submodule.

[0125] In the embodiment of the present application, two resistors are added to the energy storage valve submodule, and then two different switches are added to respectively control the switching states of the two resistors in the energy storage valve submodule. Only one of the two resistors is switched on when the energy storage unit is in a charging state or when the energy storage unit is in a discharging state. On this basis, the resistance values ​​of the two resistors are different, so that the degree of under-damped oscillation that can be suppressed when the energy storage unit is in a charging state or when the energy storage unit is in a discharging state is also different. In this way, the suppression of under-damped oscillation of the energy storage unit in different charging and discharging states is more accurate.

[0126] After the DC support capacitor 20 in the energy storage valve submodule is connected in series with the suppression circuit 40, the overvoltage stress when the IGBT in the power conversion unit 10 is turned off will increase accordingly due to the resistance in the suppression circuit 40. Wherein, under the same IGBT switch di / dt (turn-off current change rate per unit time) value, the overvoltage U when the IGBT is turned off will increase according to U=L*di / dt+i*R; wherein R represents the resistance value of the resistor element itself, and L represents the stray inductance of the resistor element itself.

[0127] Based on this, the embodiment of the present application reduces the overvoltage stress of the IGBT when it is turned off by connecting a buffer capacitor in parallel with the RC branch. Fig.14As shown, in one embodiment, the energy storage valve submodule further includes a buffer capacitor 50, and the buffer capacitor 50 is connected in parallel with the RC branch.

[0128] It should be noted that Fig.14 The illustrated connection method of the buffer capacitor 50 is only an example. In practical applications, the buffer capacitor 50 can be Fig.14 The schematic diagram shows that the whole is connected in parallel between the power conversion unit 10 and the RC branch; it can also be connected in parallel between the RC branch and the energy storage unit 30. Of course, if the RC branch is connected in parallel according to the above Figure 5 In the manner shown, the buffer capacitor 50 can be connected in parallel behind the energy storage unit 30. Figure 5 Based on the schematic diagram, the whole is connected in parallel behind the RC branch, or between the energy storage unit 30 and the RC branch.

[0129] The function of the buffer capacitor 50 in the energy storage valve submodule is mainly to buffer the high-frequency current in the current of the energy storage valve submodule when it is turned on, so as to reduce the turn-off current change rate when the IGBT is turned off, thereby reducing the overvoltage stress when the IGBT is turned off.

[0130] In one embodiment, the capacitance of the buffer capacitor 50 is smaller than the capacitance of the DC link capacitor 20 .

[0131] By setting the capacitance of the buffer capacitor 50 to be much smaller than that of the DC support capacitor 20, when the energy storage valve submodule is put into operation, a certain distinction is made between the high-frequency current passed through the buffer capacitor 50 and the high-frequency current passed through the DC support capacitor 20. For example, the buffer capacitor 50 mainly passes the high-frequency component of the current, and the DC support capacitor 20 mainly passes the medium- and low-frequency components of the current.

[0132] In practical applications, when the capacitance of the buffer capacitor 50 is determined, the determination process can be achieved through circuit simulation. During the simulation, it is necessary to consider not only the overvoltage capability at the time of IGBT shutdown, but also whether the excessively large capacitance of the buffer capacitor 50 will aggravate the degree of under-damped oscillation of the energy storage valve sub-module. Therefore, it is necessary to set the capacitance of the buffer capacitor 50 to a range that does not generate under-damped oscillation with other devices in the energy storage valve sub-module.

[0133] Optionally, the capacitance value of the buffer capacitor 50 may be in the sub-mF range. For example, the capacitance value range of the buffer capacitor 50 includes 10uF to 300uF. This capacitance value range may be a value range in a high-voltage direct-hanging scenario. When the buffer capacitor 50 is in this range, the overvoltage stress at the IGBT turn-off time can be reduced while reducing the additional impact on the overall topology of the energy storage valve submodule.

[0134] In the embodiment of the present application, a buffer capacitor is connected in parallel next to the RC branch as a whole, so that the overvoltage stress at the time of IGBT shutdown can be reduced, and the risk of IGBT failure due to excessive overvoltage stress is reduced, thereby increasing the working reliability of the IGBT and further increasing the working reliability of the energy storage valve submodule.

[0135] In the above embodiment, the overvoltage stress at the IGBT turn-off time is reduced by connecting the buffer capacitor 50 in parallel. However, in actual applications, after the suppression circuit 40 is connected to the energy storage valve submodule, the resistance value of the suppression circuit 40 will cause the IGBT to have a large turn-off overvoltage, and the buffer capacitor 50 alone may not be able to completely offset the IGBT turn-off overvoltage stress. Therefore, the embodiment of the present application also provides a method to reduce the IGBT turn-off di / dt, thereby further reducing the IGBT turn-off overvoltage, so that the risk of IGBT failure due to excessive overvoltage stress can be reduced.

[0136] Specifically, the power conversion unit 10 of the energy storage valve submodule is implemented with IGBT. Combined with the description of the previous embodiment, it can be seen that the gate of the IGBT in each power conversion unit 10 is connected to a drive circuit, and the drive circuit drives the IGBT to be turned on and off. Optionally, the parameter value of the driver in the drive circuit is inversely correlated with the turn-off current change rate of the IGBT. That is, the embodiment of the present application can reduce the IGBT turn-off di / dt (i.e., the turn-off current change rate) by increasing the parameter value of the driver.

[0137] like Fig.15 As shown, Fig.15 Figure 1 is a schematic diagram of an IGBT drive circuit. For clarity, Fig.15 Only a schematic diagram of one IGBT connected to the driving circuit is shown. Fig.15 In the figure, Rgon represents the gate turn-on resistance, Rgoff represents the gate turn-off circuit, and Cg represents the gate capacitance. The IGBT is turned on and off by Rgon, Rgoff, diodes D1 and D2, and gate capacitance Cg.

[0138] In view of the need to reduce the di / dt when the IGBT is turned off, therefore, in one embodiment, the above-mentioned increase in the parameter value of the driving device can be to increase the resistance of the gate turn-off resistor Rgoff, and / or to increase the capacitance of the gate capacitor Cg, that is, to increase either the parameter value of the gate turn-off resistor Rgoff or the gate capacitor Cg, or to increase both of them, etc., both of which can achieve the purpose of reducing the di / dt when the IGBT is turned off.

[0139] In practical applications, the specific values ​​that need to be increased for the gate turn-off resistance Rgoff and the gate capacitance Cg can be calculated based on the IGBT specifications. The voltage and current levels of the IGBT are different under different IGBT specifications, and the parameter values ​​of the driving devices in the driving circuit need to be adjusted to different degrees. Therefore, adjustments need to be made based on actual conditions.

[0140] For example, taking the IGBT voltage and current level of 4.5kV / 3kA as an example, in this case, for the flexible direct current engineering scenario, the parameter value of the driver device can be adjusted so that the di / dt of the IGBT when it is turned off reaches 5000A / μs, while in the high-voltage direct-mounted energy storage system scenario, the parameter value of the driver device can be adjusted so that the di / dt of the IGBT of the energy storage valve submodule when it is turned off is reduced to 3000A / μs. By reducing the di / dt of the IGBT of the energy storage valve submodule to 3000A / μs when it is turned off, the IGBT turn-off overvoltage can be effectively reduced.

[0141] In the embodiment of the present application, by virtue of the characteristic that the turn-off current change rate of the power device in the power conversion unit is inversely correlated with the parameter value of the driving device in the driving circuit of the power device, it is possible to reduce the turn-off current change rate of the power device in the power conversion unit, thereby further reducing the turn-off overvoltage of the power device in the power conversion unit. In this way, the problem of failure of the power device in the power conversion unit due to excessive overvoltage stress is greatly reduced, thereby increasing the working reliability of the power conversion unit.

[0142] In practical applications, once the suppression circuit 40 is added to the energy storage valve sub-module, the resistance characteristics of the suppression circuit 40 will bring additional ohmic heat loss to the entire energy storage valve sub-module. Based on this, the heat loss caused by the suppression circuit 40 to the energy storage valve sub-module can be reduced by adjusting the switching frequency of the energy storage valve sub-module.

[0143] In one embodiment, the switching frequency of the energy storage valve submodule is positively correlated with the energy loss generated by the suppression circuit.

[0144] Assuming that when the energy storage valve submodule is switched on and off once in the high-voltage direct-hung energy storage system, the energy loss generated by the resistance of the suppression circuit 40 is E, and the equivalent switching frequency of the energy storage valve submodule is f, then the heating power P of the resistance of the suppression circuit 40 is ≈ f*E. That is, the higher the switching frequency f, the greater the energy loss E generated by the resistance of the suppression circuit 40, so that the switching frequency should be positively correlated with the energy loss generated by the suppression circuit.

[0145] Based on the relationship between the equivalent switching frequency of the energy storage valve submodule and the energy loss generated by the suppression circuit, the value of the equivalent switching frequency can be set according to the energy loss value generated by the resistance of the specific suppression circuit 40 of the energy storage valve submodule. For example, in the actual flexible DC project, the value of the converter valve f can be set to about 100Hz-200Hz; and in the application of DC direct-hung energy storage valve, the value of the switching frequency f can be set between 50Hz-150Hz.

[0146] It should be noted that the value of the equivalent switching frequency of the above energy storage valve submodule is only an example. In actual applications, under the premise of meeting the operating requirements of the high-voltage direct-mounted energy storage system, the equivalent switching frequency is set to a smaller value of the switching frequency acceptable to the system as much as possible, that is, the loss of the high-voltage direct-mounted energy storage system can be optimized by minimizing the system switching frequency.

[0147] The embodiment of the present application sets the equivalent switching frequency of the energy storage valve submodule when it is switched on and off in the high-voltage direct-hung energy storage system through the characteristic that the switching frequency of the energy storage valve submodule is positively correlated with the energy loss generated by the suppression circuit, so that the energy storage valve submodule can be switched on and off at a lower equivalent switching frequency, thereby reducing the loss of the energy storage valve submodule and improving the economy and safety of the application of the energy storage valve submodule.

[0148] In one embodiment, Fig.16 As shown, the energy storage valve submodule further includes a bypass circuit 60 , which is connected in parallel with the energy storage valve submodule.

[0149] Please continue to see Fig.16 A bypass circuit 60 is provided between the two ports S1 and S2 of the energy storage valve submodule and the power conversion unit 10, so that when the energy storage valve submodule fails, or when the energy storage valve submodule may fail, the energy storage valve submodule can be cut out of the high-voltage direct-hung energy storage system through the bypass circuit 60.

[0150] For example, when an overvoltage is generated in the high-voltage direct-hung energy storage system, the bypass circuit 60 can conveniently and timely temporarily cut off the energy storage valve submodule from the high-voltage direct-hung energy storage system, thereby greatly reducing the probability of failure of the energy storage valve submodule due to the overvoltage generated by the high-voltage direct-hung energy storage system, thereby improving the operating stability and safety of the high-voltage direct-hung energy storage system.

[0151] Optionally, the bypass circuit 60 may be a bypass switch. Optionally, the bypass switch may be, but is not limited to, a mechanical bypass switch or a semiconductor device bypass switch.

[0152] In the event of a fault in the energy storage valve submodule, the current on the main circuit enters from the S1 port. At this time, the bypass switch is closed, and the current flows out from the S2 port through the bypass switch, completely short-circuiting the entire energy storage valve submodule and completely cutting the energy storage valve submodule out of the high-voltage direct-hung energy storage system.

[0153] In the embodiment of the present application, a bypass circuit is provided between the ports at which the energy storage valve submodule is connected to the main circuit of the high-voltage direct-hung energy storage system, so that in the event of a failure in the energy storage valve submodule, the energy storage valve submodule can be cut out of the high-voltage direct-hung energy storage system, thereby improving the operating stability and safety of the high-voltage direct-hung energy storage system.

[0154] In addition, an embodiment of the present application also provides a high-pressure direct-mounted energy storage system, which includes an energy storage valve submodule provided in any of the above embodiments.

[0155] The high-voltage direct-mounted energy storage system in the embodiment of the present application may include a DC high-voltage direct-mounted energy storage system, or may include an AC high-voltage direct-mounted energy storage system. Figure 1 Shown is an example diagram of an AC high-voltage direct-mounted energy storage system.

[0156] Since the energy storage valve submodule provided in the embodiment of the present application can suppress the under-damped oscillating power generated at the time of switching the switching mode, it has high reliability, so the high-voltage direct-mounted energy storage system constructed using the energy storage valve submodule in the embodiment of the present application also has high reliability.

[0157] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A storage valve submodule, characterized in that: The energy storage valve submodule includes a power conversion unit, a DC support capacitor, a suppression circuit and an energy storage unit. The suppression circuit and the DC support capacitor are connected in series to form a resistance-capacitance branch, and the resistance-capacitance branch is respectively connected in parallel with the power conversion unit and the energy storage unit.

2. The energy storage valve submodule according to claim 1, characterized in that: The suppression circuit includes a resistive element.

3. The energy storage valve submodule according to claim 2, characterized in that: The suppression circuit further includes a switch circuit connected in parallel with the resistance element.

4. The energy storage valve submodule according to claim 3, characterized in that: The resistance element includes a first resistor and a second resistor connected in series, and the switch circuit also includes a first switch and a second switch, the first switch is connected in parallel with the first resistor, and the second switch is connected in parallel with the second resistor.

5. The energy storage valve submodule according to claim 4, characterized in that: The first switch and / or the second switch is a diode.

6. The energy storage valve submodule according to claim 4, characterized in that: The resistance value of the first resistor is greater than the resistance value of the second resistor.

7. The energy storage valve submodule according to claim 3, characterized in that: The resistance element includes a third resistor and a fourth resistor connected in parallel with each other, and the switch circuit also includes a third switch and a fourth switch, the third switch is connected in series with the third resistor, and the fourth switch is connected in series with the fourth resistor.

8. The energy storage valve submodule according to any one of claims 2 to 7, characterized in that: The resistance value of the resistor element ranges from 10 mΩ to 500 mΩ.

9. The energy storage valve submodule according to any one of claims 1 to 8, characterized in that: The energy storage valve submodule further includes a buffer capacitor, which is connected in parallel with the RC branch.

10. The energy storage valve submodule according to claim 9, characterized in that: The capacitance of the buffer capacitor is smaller than the capacitance of the DC support capacitor.

11. The energy storage valve submodule according to claim 9, characterized in that: The capacitance range of the buffer capacitor includes 10uF to 300uF.

12. The energy storage valve submodule according to any one of claims 1 to 11, characterized in that: The energy storage valve submodule further includes a bypass circuit, and the bypass circuit is connected in parallel with the energy storage valve submodule.

13. The energy storage valve submodule according to any one of claims 1 to 12, characterized in that: The switching frequency of the energy storage valve submodule is positively correlated with the energy loss generated by the suppression circuit.

14. The energy storage valve submodule according to any one of claims 1 to 13, characterized in that: The turn-off current change rate of the power device in the power conversion unit is inversely correlated with the parameter value of the driving device in the driving circuit of the power device.

15. The energy storage valve submodule according to claim 14, characterized in that: The parameter value of the driving device includes the resistance value of the gate turn-off resistor in the driving circuit and / or the capacitance value of the gate capacitor in the driving circuit.

16. A high-voltage direct-mounted energy storage system, characterized in that: The high-pressure direct-mounted energy storage system comprises the energy storage valve submodule according to any one of claims 1-15.

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