Energy storage integrated current conversion module with direct current fault blocking capability and current converter

Abstract

The invention provides an energy storage integrated current conversion module with DC fault blocking capability and a current converter, the current conversion module comprises a self-resistance type sub-module, a non-isolation type bidirectional DC converter and an energy storage unit, and the non-isolation type bidirectional DC converter is connected with the self-resistance type sub-module and the energy storage unit. According to the converter provided by the invention, the functions of active support, energy dissipation, DC fault blocking and the like are integrated through the self-resistance type sub-module, the non-isolation type bidirectional DC converter and the energy storage unit in the converter module, so that auxiliary equipment such as active support equipment, an energy dissipation device and a DC circuit breaker does not need to be configured in a power grid system; the system simplifies the structure of a power grid system, reduces the complexity of the power grid system, improves the economical efficiency, and achieves the cooperation and control of different functions more easily.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage direct current transmission, and in particular to an integrated energy storage converter module and a converter with direct current fault blocking capability. Background Art

[0002] Flexible direct current transmission technology based on modular multilevel converter (MMC) has the advantages of low harmonic content, flexible control, independent regulation of active and reactive power, etc. It has important applications in high-voltage direct current transmission, grid interconnection, island power supply, and new energy grid connection. In recent years, with the continuous development and application of flexible direct current technology, the power grid will also face new challenges, which are specifically reflected in: First, the proportion of new energy continues to increase, and the system inertia is significantly reduced, resulting in a decrease in stability when the power grid is disturbed, and it is necessary to configure equipment with active support capabilities for assistance; second, new energy is random and volatile, and it is necessary to configure energy storage / energy consumption equipment to smooth out new energy fluctuations and achieve fault crossing; third, direct current development tends to be multi-terminal and networked, and the grid form is more diverse and complex, and it is necessary to have direct current fault blocking capabilities to prevent faults from spreading.

[0003] At present, the above challenges are addressed by configuring active supporting equipment (such as grid-based energy storage, wind turbines and inverters), energy-consuming devices, and specialized equipment such as DC circuit breakers. However, there are generally problems such as poor technical and economic efficiency, high system complexity, and difficulty in coordination between new equipment. Summary of the invention

[0004] In order to solve the problems of poor economy and high complexity of the flexible direct current transmission system in the prior art, the present invention proposes an integrated energy storage commutation module with direct current fault blocking capability, comprising a self-resistance submodule, a non-isolated bidirectional direct current converter and an energy storage unit, wherein the non-isolated bidirectional direct current converter is connected to the self-resistance submodule and the energy storage unit respectively;

[0005] The non-isolated bidirectional DC converter is used to conduct the energy storage unit and the self-resistance submodule, so that when the working state of the commutation module is the input state or the cut-off state, the energy storage unit provides active support to the commutation module, and when the commutation module has a power transmission failure, the energy storage unit absorbs the surplus power in the commutation module; when a DC fault occurs in the commutation module, the self-resistance submodule blocks the fault current injected into the fault point where the DC fault occurs on the AC side of the commutation module, so as to achieve DC fault ride-through.

[0006] Preferably, the self-resistance submodule comprises: a first branch, a second branch and a capacitor;

[0007] The first end of the first branch is connected to the first end of the second branch and the first end of the capacitor, the second end of the first branch is connected to the second end of the second branch, and the third end of the first branch is connected to the second end of the capacitor;

[0008] The capacitor is also connected in parallel with the non-isolated bidirectional DC converter.

[0009] Preferably, the first branch includes a first IGBT switch, a second IGBT switch, a third IGBT switch, a first diode, a second diode and a third diode, and the second branch includes a fourth diode;

[0010] The first IGBT switch is connected in reverse parallel to the first diode, the second IGBT switch is connected in reverse parallel to the second diode, the third IGBT switch is connected in reverse parallel to the third diode, the first IGBT switch is connected in series to the second IGBT switch, and the second IGBT switch is connected in reverse series to the third IGBT switch;

[0011] The collector of the first IGBT switch serves as the first end of the first branch, the collector of the third IGBT switch serves as the second end of the first branch, and the connection point between the second IGBT switch and the third IGBT switch serves as the third end of the first branch;

[0012] The cathode of the fourth diode serves as the first end of the second branch, and the anode of the fourth diode serves as the second end of the second branch.

[0013] Preferably, when the working state of the commutation module is the input state, the first IGBT switch and the third IGBT switch are turned on, and the second IGBT switch is turned off, forming a circuit for alternating charging and discharging of the capacitor;

[0014] Among them, the current input from the AC side in the circuit of alternately charging and discharging the capacitor passes through the first diode, the capacitor and the third diode, or the current input from the AC side passes through the first IGBT switch, the capacitor and the third IGBT switch.

[0015] Preferably, when the working state of the commutation module is the cut-off state, the second IGBT switch and the third IGBT switch are turned on, and the first IGBT switch is turned off, so that the current in the commutation module passes through the second diode and the third diode, or the current in the commutation module passes through the second IGBT switch and the third IGBT switch, and the capacitor is short-circuited.

[0016] Preferably, when the working state of the commutation module is a locked state, the first IGBT switch, the second IGBT switch and the third IGBT switch are turned off, so that the current in the commutation module passes through the first diode, the capacitor and the third diode, or passes through the fourth diode, the capacitor and the second diode, and the capacitor is charged.

[0017] Preferably, the non-isolated bidirectional DC converter comprises a fourth IGBT switch, a fifth IGBT switch, a fifth diode, and a sixth diode, and the energy storage unit comprises an inductor and an energy storage subunit, and the inductor is connected in series with the energy storage subunit;

[0018] The fourth IGBT switch is connected in reverse parallel to the fifth diode, the fifth IGBT switch is connected in reverse parallel to the sixth diode, and the fourth IGBT switch is connected in series to the fifth IGBT switch;

[0019] The fifth IGBT switch is connected in parallel with the energy storage unit.

[0020] Preferably, the energy storage subunit is used to charge the inductor when the fourth IGBT switch is turned off and the fifth IGBT switch is turned on.

[0021] Preferably, the non-isolated bidirectional DC converter is specifically used to turn on the energy storage unit and the self-resistance sub-module when the fourth IGBT switch is turned on and the fifth IGBT switch is turned off.

[0022] Based on the same inventive concept, the present invention also provides a modular multi-level converter, which includes a plurality of parallel bridge arms; the connection points of the plurality of bridge arms serve as the DC ends of the converter, and the bridge arms include a plurality of series-connected integrated energy storage converter modules with DC fault blocking capability.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides an integrated energy storage commutation module and a converter with DC fault blocking capability, wherein the commutation module includes a self-resistance submodule, a non-isolated bidirectional DC converter and an energy storage unit, wherein the non-isolated bidirectional DC converter is connected to the self-resistance submodule and the energy storage unit. The converter provided by the present invention integrates active support, energy dissipation, DC fault blocking and other functions into one through the self-resistance submodule, the non-isolated bidirectional DC converter and the energy storage unit in the commutation module, so that the power grid system does not need to be configured with auxiliary equipment such as active support equipment, energy consumption devices and DC circuit breakers, thereby simplifying the structure of the power grid system, reducing the complexity of the power grid system, improving the economy, and making it easier to achieve coordination and control between different functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of an integrated energy storage converter module with DC fault blocking capability provided by the present invention;

[0026] Figure 2 A schematic diagram of another energy storage integrated converter module with DC fault blocking capability provided by the present invention;

[0027] Figure 3 A schematic diagram of a current path of a converter module provided by the present invention when the working state is an input state;

[0028] Figure 4 A schematic diagram of a current path of another converter module provided by the present invention when the working state is the input state;

[0029] Figure 5 A schematic diagram of a current path of a commutation module provided by the present invention when the working state is a cut-out state;

[0030] Figure 6 A schematic diagram of a current path of another converter module provided by the present invention when the working state is a cut-out state;

[0031] Figure 7 A schematic diagram of a current path when an energy storage device provided by the present invention is not working;

[0032] Figure 8 A schematic diagram of a current path of a converter module provided by the present invention when the working state is a locked state;

[0033] Fig. 9 A schematic diagram of a current path of another converter module provided by the present invention when the working state is a locked state;

[0034] Fig.10 A schematic diagram of a fault current path when a converter module provided by the present invention is fully locked;

[0035] Fig.11 A schematic diagram of a current path of an active support mode of an energy storage unit in a converter module provided by the present invention;

[0036] Fig.12 A schematic diagram of the current path of an energy dissipation mode of an energy storage unit in a converter module provided by the present invention. DETAILED DESCRIPTION

[0037] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0038] Embodiment 1:

[0039] Figure 1 A schematic diagram of an integrated energy storage converter module with DC fault blocking capability provided by the present invention is shown in FIG. Figure 1 As shown: the energy storage integrated commutation module may include a self-resistance submodule 101, a non-isolated bidirectional DC converter 102 and an energy storage unit 103, wherein the non-isolated bidirectional DC converter 102 may be connected to the self-resistance submodule 101 and the energy storage unit 103 respectively; the non-isolated bidirectional DC converter 102 may be used to conduct the energy storage unit 103 and the self-resistance submodule 101, so that when the working state of the commutation module is the input state or the cut-off state, the energy storage unit 103 provides active support to the commutation module, and when the commutation module has a power transmission failure, the energy storage unit 103 absorbs the surplus power in the commutation module; when a DC fault occurs in the commutation module, the self-resistance submodule 101 blocks the fault point where the DC fault occurs on the AC side of the commutation module from injecting fault current, so as to achieve DC fault ride-through.

[0040] The converter module further includes a first access terminal P and a second access terminal N, wherein the first access terminal P is used to connect to the second access terminal N of a converter module adjacent to the converter module in the converter bridge arm where the converter module is located, and the second access terminal N is used to connect to the first access terminal P of another converter module adjacent to the converter module in the converter bridge arm where the converter module is located. The input state is that the current input to the converter module through the first access terminal P flows through the capacitor and flows out through the second access terminal N, or the current input to the converter module through the second access terminal N flows through the capacitor and flows out through the first access terminal P, so that the capacitor is in a charging state. The cut-off state is that the current input to the converter module through the first access terminal P flows out directly through the second access terminal N, or the current input to the converter module through the second access terminal N flows out directly through the first access terminal P, so that the capacitor in the converter module is in a short-circuit state.

[0041] It should be noted that the self-resistance submodule 101 can be regarded as an MMC (Modular Multilevel Converter) full-bridge submodule with one IGBT (Insulated Gate Bipolar Transistor) tube removed, and can output 0, U c, -U c Three levels, with bidirectional blocking capability of fault current. The energy storage unit 103 is connected in parallel to the capacitor side of the self-resistance module via the non-isolated bidirectional DC converter 102. The converter integrates the functions of active support equipment, energy consumption devices and circuit breakers through the self-resistance submodule 101, the non-isolated bidirectional DC converter 102 and the energy storage unit 103 in the converter module, reduces the configuration of additional equipment in the power grid system, improves the overall economy of the power grid system, and integrates the functions of active support equipment, energy consumption devices and circuit breakers into the converter module of the converter, improves the convenience and reliability of coordinated control of the power grid system, and is conducive to simplifying the control logic. Secondly, the energy storage unit 103 is connected in parallel to the capacitor side via the isolated bidirectional DC converter 102, which can quickly respond to system requirements and minimize the loss during energy transmission, which is conducive to improving the energy conversion efficiency of the converter.

[0042] The present invention provides an integrated energy storage commutation module with DC fault blocking capability, including a self-resistance submodule, a non-isolated bidirectional DC converter and an energy storage unit, wherein the non-isolated bidirectional DC converter is connected to the self-resistance submodule and the energy storage unit. The converter provided by the present invention integrates active support, energy dissipation, DC fault blocking and other functions into one through the self-resistance submodule, the non-isolated bidirectional DC converter and the energy storage unit in the commutation module, so that the power grid system does not need to be configured with auxiliary equipment such as active support equipment, energy consumption devices and DC circuit breakers, thereby simplifying the structure of the power grid system, reducing the complexity of the power grid system, improving the economy, and making it easier to achieve coordination and control between different functions.

[0043] Figure 2 A schematic diagram of another energy storage integrated converter module with DC fault blocking capability provided by the present invention is shown as follows: Figure 2 As shown, the self-resistance submodule 101 may include: a first branch 1011, a second branch 1012 and a capacitor C; the first end of the first branch 1011 may be connected to the first end of the second branch 1012 and the first end of the capacitor C, the second end of the first branch 1011 may be connected to the second end of the second branch 1012, and the third end of the first branch 1011 may be connected to the second end of the capacitor C; the capacitor C may also be connected in parallel with the non-isolated bidirectional DC converter 102.

[0044] It should be noted that the commutation module controls the capacitor C to be in a charging state or a short-circuit state through the conduction state of the first branch 1011 in the self-resistance submodule 101. When a DC fault occurs in the commutation module, the commutation module inputs a reverse voltage to the second branch 1012 in the self-resistance submodule 101 to block the fault current injected into the AC lateral fault point, thereby achieving DC fault crossing.

[0045] Preferably, Figure 2 For example, the first branch 1011 may include a first IGBT switch T1, a second IGBT switch T2, a third IGBT switch T3, a first diode D1, a second diode D2 and a third diode D3, and the second branch 1012 may include a fourth diode D4; the first IGBT switch T1 may be connected in reverse parallel to the first diode D1, the second IGBT switch T2 may be connected in reverse parallel to the second diode D2, the third IGBT switch T3 may be connected in reverse parallel to the third diode D3, the first IGBT switch T1 may be connected in series to the second IGBT switch T2, and the The second IGBT switch T2 can be connected in reverse series with the third IGBT switch T3; wherein, the collector of the first IGBT switch T1 can serve as the first end of the first branch 1011, the collector of the third IGBT switch T3 can serve as the second end of the first branch 1011, and the connection point between the second IGBT switch T2 and the third IGBT switch T3 can serve as the third end of the first branch 1011; the cathode of the fourth diode D4 can serve as the first end of the second branch 1012, and the anode of the fourth diode D4 can serve as the second end of the second branch 1012.

[0046] The first IGBT switch T1 , the second IGBT switch T2 , and the third IGBT switch T3 may be controlled to be turned on or off by means of PWM (Pulse Width Modulation).

[0047] It should be noted that when the commutation module is in normal operation (i.e., the working state of the commutation module is in the on state or the off state), the third IGBT switch T3 can be in the on state all the time. When the first IGBT switch T1 is on and the second IGBT switch T2 is off, the working state of the commutation module is in the on state; when the first IGBT switch T1 is off and the second IGBT switch T2 is on, the working state of the commutation module is in the off state; when the first IGBT switch T1 and the second IGBT switch T2 are off at the same time, the working state of the commutation module is in the locked state (i.e., an abnormal operating state).

[0048] Preferably, Figure 2For example, when the working state of the converter module is the input state, the first IGBT switch T1 and the third IGBT switch T3 are turned on, and the second IGBT switch T2 is turned off (for example, represented by the input state T1=1, T2=0, T3=1), forming a circuit for alternating charging and discharging of the capacitor C; wherein, in the circuit for alternating charging and discharging of the capacitor C, the current input from the AC side passes through the first diode D1, the capacitor C and the third diode D3, or the current input from the AC side passes through the first IGBT switch T1, the capacitor C and the third IGBT switch T3.

[0049] For example, Figure 3 As shown, Figure 3 A schematic diagram of a current path of a converter module provided by the present invention in the working state of the input state, wherein the solid line represents the current flow path, the arrow represents the current flow direction, the first IGBT switch T1 and the third IGBT switch T3 are turned on (for example, represented as the input state T1=1, T2=0, T3=1), and the current i of the converter module is input through the first access terminal P SM The current flows to the capacitor C through the first diode D1 connected in reverse parallel to the first IGBT switch T1, and is output through the third diode D3 connected in reverse parallel to the third IGBT switch T3 and the second access terminal N, so that the capacitor C is charged or discharged. SM is the voltage of capacitor C. Figure 4 As shown, Figure 4 A schematic diagram of a current path of another converter module provided by the present invention in which the working state is the input state, and the current i of the converter module is input through the second access terminal N SM The current flows to the capacitor C through the third IGBT switch T3 and is output through the second access terminal N to charge or discharge the capacitor C. SM is the voltage of capacitor C.

[0050] Preferably, Figure 2 For example, when the working state of the commutation module is the cut-off state, the second IGBT switch T2 and the third IGBT switch T3 are turned on, and the first IGBT switch T1 is turned off (for example, represented by the cut-off state T1=0, T2=1, T3=1), so that the current in the commutation module passes through the second diode D2 and the third diode D3, or the current in the commutation module passes through the second IGBT switch T2 and the third IGBT switch T3, and the capacitor C is short-circuited.

[0051] For example, Figure 5 As shown, Figure 5A schematic diagram of a current path of a converter module provided by the present invention in a cut-out state, wherein the second IGBT switch T2 and the third IGBT switch T3 are turned on, and the first IGBT switch T1 is turned off (for example, represented as a cut-out state T1=0, T2=1, T3=1), and the current i of the converter module is input through the first access terminal P SM The current passes through the second IGBT switch T2 and the third IGBT switch T3 in sequence and is output through the second access terminal N, so that the capacitor C is short-circuited. SM is the voltage of capacitor C. Figure 6 As shown, Figure 6 A schematic diagram of a current path of another converter module provided by the present invention when the working state is a cut-out state, wherein the current i of the converter module is input through the second access terminal N SM The current passes through the third IGBT switch T3 and the second IGBT switch T2 in sequence and is output through the second access terminal N, so that the capacitor C is short-circuited. SM is the voltage of capacitor C.

[0052] It should be noted that when the commutation module is in normal operation (i.e., the working state of the commutation module is in the on state or the off state), the switch state in the self-resistance submodule 101 is as above. Figures 3 to 6 As shown, the energy storage device is in a locked state (i.e., T4 and T5 are turned off at the same time, that is, the energy storage device is not working). At this time, the working state of the converter module is similar to that of the MMC half-bridge submodule. The current path of the converter module is as follows: Figure 7 When the converter composed of the converter modules is in normal operation, the control system of the converter composed of the converter modules can be completely consistent with the modular multi-level converter of the traditional half-bridge structure, which is conducive to improving the compatibility of the converter control system.

[0053] Preferably, Figure 2 For example, when the working state of the commutation module is the locked state, the first IGBT switch T1, the second IGBT switch T2 and the third IGBT switch T3 are turned off, so that the current in the commutation module passes through the first diode D1, the capacitor C and the third diode D3, or passes through the fourth diode D4, the capacitor C and the second diode D2, and the capacitor C is charged.

[0054] It should be noted that if Figure 8 As shown, Figure 8 A schematic diagram of a current path when the working state of a commutation module provided by the present invention is a locked state. When the working state of the commutation module is the locked state, the first IGBT switch T1, the second IGBT switch T2 and the third IGBT switch T3 are turned off (for example, the locked state T1=0, T2=0, T3=0), and the current i of the commutation module is input through the first access terminal P.SM Passing through the first diode D1, capacitor C (u SM The first IGBT switch T1 and the second IGBT switch T2 are connected to the first access terminal P and the second access terminal N of the commutation module. The first IGBT switch T1 and the second IGBT switch T2 are connected to the third diode D3 and output through the second access terminal N. In this process, the current will continue to charge the capacitor. As time goes by, the reverse voltage borne by the first IGBT switch T1 and the second IGBT switch T2 will become higher and higher, resulting in the breakdown of the first IGBT switch T1 and the second IGBT switch T2. Therefore, in order to avoid the IGBT breakdown, a bypass switch is connected in parallel between the first access terminal P and the second access terminal N of the commutation module. When the above fault occurs in the commutation module, the commutation module is short-circuited by closing the bypass switch to avoid damage to the IGBT in the commutation module.

[0055] Fig. 9 A schematic diagram of a current path of another converter module provided by the present invention when the working state is a locked state, such as Fig. 9 As shown, when a DC fault occurs in the converter module (i.e., the working state of the converter module is the locked state), the first IGBT switch T1, the second IGBT switch T2, and the third IGBT switch T3 are turned off (for example, the locked state T1=0, T2=0, T3=0), and the current i of the converter module is input through the second access terminal N. SM Passing through the fourth diode D4, capacitor C (u SM The voltage of the capacitor C is connected to the second diode D2, and is output through the first access terminal P, and the capacitor C is charged. When a DC fault occurs in the power grid system (or DC transmission system), the switch state in the self-resistance submodule 101 is as follows: Fig. 9 As shown (that is, all IGBT tubes in the commutation module are turned off), as Fig.10 As shown, Fig.10 A schematic diagram of a fault current path when a converter module is fully locked provided by the present invention. The converter module can output a reverse voltage to block the injection of fault current at the fault point where a DC fault occurs on the AC side of the converter module, so as to achieve DC fault ride-through.

[0056] Preferably, Figure 2 For example, the non-isolated bidirectional DC converter 102 may include a fourth IGBT switch T4, a fifth IGBT switch T5, a fifth diode D5, and a sixth diode D6, and the energy storage unit 103 may include an inductor L and an energy storage sub-unit E, and the inductor L is connected in series with the energy storage sub-unit E; the fourth IGBT switch T4 is connected in reverse parallel to the fifth diode D5, the fifth IGBT switch T5 is connected in reverse parallel to the sixth diode D6, and the fourth IGBT switch T4 is connected in series with the fifth IGBT switch T5; the fifth IGBT switch T5 is connected in parallel to the energy storage unit 103.

[0057] The fourth IGBT switch T4 and the fifth IGBT switch T5 may be controlled to be turned on or off by PWM.

[0058] It should be noted that when the energy storage unit 103 is in the input state, the fourth IGBT switch T4 is turned on and the fifth IGBT switch T5 is turned off (i.e., T4 is turned on and T5 is turned off); when the energy storage unit 103 is in the cut-off state (inductor energy storage state), the fourth IGBT switch T4 is turned off and the fifth IGBT switch T5 is turned on (i.e., T4 is turned off and T5 is turned on); when the energy storage unit 103 is in the locked state, the fourth IGBT switch T4 and the fifth IGBT switch T5 are turned off at the same time (i.e., T4 and T5 are turned off at the same time). The inductor L is used to filter out the harmonic components of the energy storage unit 103.

[0059] Preferably, Figure 2 For example, the energy storage subunit E is used to charge the inductor L when the fourth IGBT switch T4 is turned off and the fifth IGBT switch T5 is turned on.

[0060] It should be noted that when the commutation module is in normal operation (i.e., the working state of the commutation module is in the on state or the off state), the energy storage unit 103 is in the active support mode (i.e., the energy storage unit discharges to the capacitor C through the energy storage subunit E and the inductor L to provide active support). Fig.11 As shown, Fig.11 A schematic diagram of the current path of an active support mode of an energy storage unit in a commutation module provided by the present invention, when the fourth IGBT switch T4 is turned off and the fifth IGBT switch T5 is turned on, the energy storage subunit E charges the inductor L through the fifth IGBT switch T5.

[0061] Preferably, Figure 2 For example, the non-isolated bidirectional DC converter 102 is specifically used to conduct the energy storage unit 103 and the self-resistance submodule 101 when the fourth IGBT switch T4 is turned on and the fifth IGBT switch T5 is turned off.

[0062] It should be noted that the energy storage unit 103 is in the energy dissipation mode, the fourth IGBT switch T4 is turned on, and the fifth IGBT switch T5 is turned off. At the moment when the fifth IGBT switch T5 is turned off, due to the existence of the (energy storage inductor) inductor L, the loop current cannot change suddenly, and a large reverse induced voltage will be generated on the inductor L to hinder the change of the loop current. At this time, the superposition of the energy storage voltage and the induced voltage of the inductor L will be higher than the voltage of the capacitor in the converter module, so they charge the capacitor together and play an active supporting role. The current path of the energy storage unit 103 discharging to the capacitor is as follows: Fig.12 As shown, as the induced voltage decreases and the capacitor voltage increases, the discharge current of the energy storage unit 103 gradually decreases.

[0063] Embodiment 2:

[0064] Based on the same inventive concept, the present invention also provides a modular multi-level converter, which includes a plurality of parallel bridge arms; the connection points of the plurality of bridge arms serve as the DC ends of the converter, and the bridge arms include a plurality of series-connected integrated energy storage converter modules with DC fault blocking capability.

[0065] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. An integrated energy storage commutation module with DC fault blocking capability, characterized in that: It includes a self-resistance submodule, a non-isolated bidirectional DC converter and an energy storage unit, wherein the non-isolated bidirectional DC converter is connected to the self-resistance submodule and the energy storage unit respectively; The non-isolated bidirectional DC converter is used to conduct the energy storage unit and the self-resistance submodule, so that when the working state of the commutation module is the input state or the cut-off state, the energy storage unit provides active support to the commutation module, and when the commutation module has a power transmission failure, the energy storage unit absorbs the surplus power in the commutation module; when a DC fault occurs in the commutation module, the self-resistance submodule blocks the fault current injected into the fault point where the DC fault occurs on the AC side of the commutation module, so as to achieve DC fault ride-through.

2. The commutation module according to claim 1, characterized in that: The self-resistance submodule includes: a first branch, a second branch and a capacitor; The first end of the first branch is connected to the first end of the second branch and the first end of the capacitor, the second end of the first branch is connected to the second end of the second branch, and the third end of the first branch is connected to the second end of the capacitor; The capacitor is also connected in parallel with the non-isolated bidirectional DC converter.

3. The commutation module according to claim 2, characterized in that: The first branch includes a first IGBT switch, a second IGBT switch, a third IGBT switch, a first diode, a second diode and a third diode, and the second branch includes a fourth diode; The first IGBT switch is connected in reverse parallel to the first diode, the second IGBT switch is connected in reverse parallel to the second diode, the third IGBT switch is connected in reverse parallel to the third diode, the first IGBT switch is connected in series to the second IGBT switch, and the second IGBT switch is connected in reverse series to the third IGBT switch; The collector of the first IGBT switch serves as the first end of the first branch, the collector of the third IGBT switch serves as the second end of the first branch, and the connection point between the second IGBT switch and the third IGBT switch serves as the third end of the first branch; The cathode of the fourth diode serves as the first end of the second branch, and the anode of the fourth diode serves as the second end of the second branch.

4. The commutation module according to claim 3, characterized in that: When the working state of the commutation module is the input state, the first IGBT switch and the third IGBT switch are turned on, and the second IGBT switch is turned off, so as to form a circuit for alternately charging and discharging the capacitor; Among them, the current input from the AC side in the circuit of alternately charging and discharging the capacitor passes through the first diode, the capacitor and the third diode, or the current input from the AC side passes through the first IGBT switch, the capacitor and the third IGBT switch.

5. The commutation module according to claim 3, characterized in that: When the working state of the commutation module is the cut-off state, the second IGBT switch and the third IGBT switch are turned on, and the first IGBT switch is turned off, so that the current in the commutation module passes through the second diode and the third diode, or the current in the commutation module passes through the second IGBT switch and the third IGBT switch, and the capacitor is short-circuited.

6. The commutation module according to claim 3, characterized in that: When the working state of the commutation module is the locked state, the first IGBT switch, the second IGBT switch and the third IGBT switch are turned off, so that the current in the commutation module passes through the first diode, the capacitor and the third diode, or passes through the fourth diode, the capacitor and the second diode, and the capacitor is charged.

7. The commutation module according to claim 3, characterized in that: The non-isolated bidirectional DC converter includes a fourth IGBT switch, a fifth IGBT switch, a fifth diode, and a sixth diode, and the energy storage unit includes an inductor and an energy storage sub-unit, and the inductor is connected in series with the energy storage sub-unit; The fourth IGBT switch is connected in reverse parallel to the fifth diode, the fifth IGBT switch is connected in reverse parallel to the sixth diode, and the fourth IGBT switch is connected in series to the fifth IGBT switch; The fifth IGBT switch is connected in parallel with the energy storage unit.

8. The commutation module according to claim 7, characterized in that: The energy storage subunit is used to charge the inductor when the fourth IGBT switch is turned off and the fifth IGBT switch is turned on.

9. The commutation module according to claim 7, characterized in that: The non-isolated bidirectional DC converter is specifically used to turn on the energy storage unit and the self-resistance sub-module when the fourth IGBT switch is turned on and the fifth IGBT switch is turned off.

10. A modular multilevel converter, characterized in that: The converter comprises a plurality of bridge arms connected in parallel; the connection points of the plurality of bridge arms serve as the DC ends of the converter, and the bridge arms comprise a plurality of converter modules as described in any one of claims 1 to 9 connected in series.

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