Direct current system

Abstract

The invention relates to the technical field of direct-current energy consumption control in direct-current power transmission, and discloses a direct-current system. The direct current system comprises a power module, a first direct current support capacitor branch, a first switch branch and a first energy consumption resistor; the first end of the first switch branch is connected with the first end of the first direct-current support capacitor branch, and the second end of the first energy consumption resistor is connected with the second end of the first direct-current support capacitor branch; the first switch branch comprises at least two first switch modules; each first switch module comprises a first power device, a first diode, a first static voltage-sharing resistor and a first dynamic voltage-sharing module; a first electrode of the first power device is connected with a cathode of the first diode, and a second electrode of the first power device is connected with an anode of the first diode; the first static voltage-sharing resistor is connected in parallel with two ends of the first diode; the first dynamic voltage-sharing module is connected in parallel with two ends of the first static voltage-sharing resistor. The overall cost of the direct current system is reduced while the workload of designers is reduced.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of direct current energy consumption control in direct current power transmission, and in particular to a direct current system. Background Art

[0002] In the field of DC transmission, with the development of power electronics technology, new energy has the ability to connect to large power grids or local power grids. However, with the access of large-scale photovoltaic, wind power and other new energy sources or when the local power grid experiences a voltage drop, active power cannot be delivered. The DC system will have surplus power, which will increase the voltage of the DC transmission line, which may cause harm to both the power transmission equipment and the user equipment. When the DC system is shut down for maintenance, the capacitors of the DC converter equipment will be charged, which will bring unnecessary danger to the maintenance personnel. The existing flexible DC converter uses power devices as the main components. Due to the uneven voltage characteristics of the devices, the power devices have uneven voltage distribution. The DC system requires static voltage equalizing resistors to design voltage equalization for the power devices.

[0003] The topological structure of the existing DC system is composed of a switch module and a resistor in series. The design is only for the control of the DC energy consumption circuit. If power devices are used, only the voltage balancing design is considered, and the state of the overall equipment during operation or maintenance is not considered. The safety of on-site maintenance personnel cannot be guaranteed during maintenance. The capacitor discharge circuit, energy consumption circuit and power device voltage balancing circuit of the existing DC system are designed separately, which increases the workload of designers and the overall cost of the DC system. Summary of the invention

[0004] The present invention provides a direct current system, which reduces the workload of designers and reduces the overall cost of the direct current system.

[0005] According to one aspect of the present invention, a direct current system is provided, the direct current system comprising:

[0006] A power module, a first DC support capacitor branch, a first switch branch and a first energy dissipation resistor;

[0007] A first end of the first DC support capacitor branch is connected to a first end of the power module, and a second end of the first DC support capacitor branch is connected to a second end of the power module;

[0008] The first switch branch and the first energy-consuming resistor form a first series structure;

[0009] The first series structure is connected in parallel to the two ends of the first DC support capacitor branch; wherein the first end of the first switch branch is connected to the first end of the first DC support capacitor branch, the second end of the first switch branch is connected to the first end of the first energy dissipation resistor, and the second end of the first energy dissipation resistor is connected to the second end of the first DC support capacitor branch;

[0010] The first switch branch includes at least two first switch modules, and the at least two first switch modules are connected in series in sequence;

[0011] Wherein, the first switch module includes: a first power device, a first diode, a first static voltage balancing resistor and a first dynamic voltage balancing module;

[0012] The first electrode of the first power device is connected to the cathode of the first diode, and the second electrode of the first power device is connected to the anode of the first diode;

[0013] The first static voltage-equalizing resistor is connected in parallel at both ends of the first diode; and the first dynamic voltage-equalizing module is connected in parallel at both ends of the first static voltage-equalizing resistor.

[0014] Optionally, the first dynamic voltage balancing module includes: a first dynamic voltage balancing resistor and a first dynamic voltage balancing capacitor;

[0015] Wherein, the first dynamic balancing resistor is connected in series with the first dynamic balancing capacitor.

[0016] Optionally, the first DC support capacitor branch includes a first capacitor.

[0017] Optionally, the first DC support capacitor branch includes N first capacitors connected in series in sequence, wherein N is an integer greater than or equal to 2.

[0018] Optionally, the DC system further includes N first regulating resistors;

[0019] Two ends of each first regulating resistor are respectively connected to the first capacitor and the first power device to form a discharge loop of the first capacitor.

[0020] Optionally, the DC system further comprises:

[0021] A second DC support capacitor branch, a second switch branch and a second energy dissipation resistor;

[0022] The first end of the second DC support capacitor branch is connected to the second end of the power module, and the second end of the second DC support capacitor branch is connected to the third end of the power module;

[0023] The second switch branch and the second energy dissipation resistor form a second series structure;

[0024] The second series structure is connected in parallel to the two ends of the second DC support capacitor branch; wherein the first end of the second switch branch is connected to the first end of the second DC support capacitor branch, the second end of the second switch branch is connected to the first end of the second energy dissipation resistor, and the second end of the second energy dissipation resistor is connected to the second end of the second DC support capacitor branch;

[0025] The second switch branch includes at least two second switch modules, and the at least two second switch modules are connected in series in sequence;

[0026] Wherein, the second switch module includes: a second power device, a second diode, a second static voltage balancing resistor and a second dynamic voltage balancing module;

[0027] The first electrode of the second power device is connected to the cathode of the second diode, and the second electrode of the second power device is connected to the anode of the second diode;

[0028] The second static voltage-equalizing resistor is connected in parallel at both ends of the second diode; and the second dynamic voltage-equalizing module is connected in parallel at both ends of the second static voltage-equalizing resistor.

[0029] Optionally, the second dynamic voltage balancing module includes: a second dynamic voltage balancing resistor and a second dynamic voltage balancing capacitor;

[0030] Wherein, the second dynamic balancing resistor is connected in series with the second dynamic balancing capacitor.

[0031] Optionally, when the first DC support capacitor branch includes one first capacitor, the second DC support capacitor branch includes one second capacitor.

[0032] Optionally, when the first DC support capacitor branch includes N first capacitors connected in series, the second DC support capacitor branch includes M second capacitors connected in series, wherein M is an integer greater than or equal to 2.

[0033] Optionally, the DC system further includes M second regulating resistors;

[0034] Two ends of each second regulating resistor are respectively connected to the second capacitor and the second power device to form a discharge loop of the second capacitor.

[0035] The embodiment of the present invention normalizes the capacitor discharge circuit, the voltage balancing circuit, and the DC energy consumption circuit, and designs the three circuits into the DC system. The first energy consumption resistor is used as both the capacitor discharge circuit and the voltage balancing circuit. The design of the capacitor discharge circuit resistor and the design of the power device voltage balancing circuit resistor are considered at the same time, so as to avoid wasting design time and increasing the overall cost of the DC system. The number of resistors and power devices invested in step-by-step voltage control is adopted to perform power control and charge and discharge control, which ensures the stable operation of the DC system and the personal safety of maintenance personnel in the shutdown state, and can quickly restore the DC system to a normal operating state in a fault state. In summary, the present invention solves the problem that the capacitor discharge circuit, the energy consumption circuit, and the power device voltage balancing circuit of the existing DC energy consumption circuit are designed separately, which increases the workload of designers and increases the overall cost of the DC system.

[0036] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 is a structural schematic diagram of a DC system provided according to an embodiment of the present invention;

[0039] Figure 2 is a structural schematic diagram of another DC system provided according to an embodiment of the present invention;

[0040] Figure 3 is a structural schematic diagram of another DC system provided according to an embodiment of the present invention;

[0041] Figure 4 is a structural schematic diagram of another DC system provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] Figure 1 is a schematic diagram of a DC energy consumption circuit according to an embodiment of the present invention, referring to Figure 1 , an embodiment of the present invention provides a DC system, the DC system comprising:

[0045] A power module 10, a first DC support capacitor branch 20, a first switch branch 30 and a first energy dissipation resistor R1;

[0046] A first end of the first DC support capacitor branch 20 is connected to a first end of the power module 10, and a second end of the first DC support capacitor branch 20 is connected to a second end of the power module 10;

[0047] The first switch branch 30 and the first energy-consuming resistor R1 form a first series structure;

[0048] The first series structure is connected in parallel at both ends of the first DC support capacitor branch 20; wherein the first end of the first switch branch 30 is connected to the first end of the first DC support capacitor branch 20, the second end of the first switch branch 30 is connected to the first end of the first energy dissipation resistor R1, and the second end of the first energy dissipation resistor R1 is connected to the second end of the first DC support capacitor branch 20;

[0049] The first switch branch 30 includes at least two first switch modules, and the at least two first switch modules are connected in series in sequence;

[0050] Wherein, the first switch module includes: a first power device, a first diode, a first static voltage balancing resistor and a first dynamic voltage balancing module;

[0051] A first electrode of the first power device is connected to a cathode of the first diode, and a second electrode of the first power device is connected to an anode of the first diode;

[0052] The first static voltage-equalizing resistor is connected in parallel at both ends of the first diode; and the first dynamic voltage-equalizing module is connected in parallel at both ends of the first static voltage-equalizing resistor.

[0053] Specifically, the DC system includes a DC energy consumption circuit, a first DC support capacitor branch 20, a power module 10, etc. The DC energy consumption circuit includes a first switch branch 30 and a first energy consumption resistor R1. The power module 10 is composed of power devices to form a rectifier circuit or an inverter circuit. The front-stage topology of the DC system is composed of N power modules, which are used to convert AC into DC or invert DC into AC.

[0054] Figure 1 The DC system in the embodiment is composed of a front-stage rectifier or inverter topology composed of N power modules, a first DC support capacitor branch 20, N first power devices Tsz1-TszN, N first static voltage-equalizing resistors Rsz1-RszN, N first dynamic voltage-equalizing modules 31-3N, and a first energy-consuming resistor R1. The above devices can be connected in series in multiple stages to adapt to different system powers and system voltages. Optionally, the first power device includes at least one of: IGBT, IGCT, SiC, and IEGT.

[0055] The first DC support capacitor branch 20 plays the role of voltage stabilization and filtering in the circuit. The N first power devices Tsz1-TszN are mainly used as switches, playing the role of inputting or withdrawing the first energy dissipation resistor R1. The N first static voltage-equalizing resistors Rsz1-RszN play the role of voltage balancing of the first power devices in the circuit on the one hand, and play the role of discharging the first DC support capacitor branch 20 on the other hand. The N first dynamic voltage-equalizing modules 31-3N are used to absorb the peak overvoltage generated by the N first power devices Tsz1-TszN when they are turned off. The main function of the first energy dissipation resistor R1 in the circuit is to consume excess energy in the loop.

[0056] Functions and effects of the DC system: When an abnormality occurs in the DC system, the N first power devices Tsz1-TszN are turned on to release the excess voltage of the system into the first energy-consuming resistor R1, complete the energy release, and maintain the voltage of the DC system at the rated operating condition. When the DC system is shut down for maintenance, the first DC support capacitor branch 20 completes the release of the capacitor charge within the specified time through the N first static voltage-equalizing resistors Rsz1-RszN and the first energy-consuming resistor R1.

[0057] Necessity of N first static voltage-equalizing resistors Rsz1-RszN: Due to the dispersion of the static volt-ampere characteristics of the power devices, the voltage division of each power device is not equal. Since the dispersion of the resistor can be very small, it is necessary to use static voltage-equalizing resistors to make the voltage division of each power device equal.

[0058] In the prior art, the capacitor discharge circuit, voltage balancing circuit, and DC energy consumption circuit are designed separately, which increases the workload of designers and the overall cost of the DC system. In the prior art, the capacitor discharge circuit, voltage balancing circuit, and DC energy consumption circuit each have their own resistors to form a circuit.

[0059] However, if Figure 1 As shown, in the DC system provided by the present invention, by setting two capacitor discharge circuits (the first capacitor discharge circuit is composed of the first capacitor Cs1, N first power devices Tsz1-TszN, and the first energy dissipation resistor R1; the second capacitor discharge circuit is composed of the first capacitor Cs1, N static voltage-equalizing resistors Rsz1-RszN, and the first energy dissipation resistor R1), an energy dissipation circuit (the energy dissipation circuit is composed of N first power devices Tsz1-TszN, and the first energy dissipation resistor R1), and a voltage-equalizing circuit (the voltage-equalizing circuit is composed of N first static voltage-equalizing resistors Rsx1-RsxN), the capacitor discharge circuit, the voltage-equalizing circuit, and the DC energy dissipation circuit are normalized, and the three circuits are combined and designed into the DC system, and the resistances of the above-mentioned capacitor discharge circuit, voltage-equalizing circuit, and DC energy dissipation circuit are uniformly considered, and the energy dissipation resistor is used as both a capacitor discharge circuit and a voltage-equalizing circuit, and the voltage-equalizing resistor and the energy dissipation resistor are reduced in resistance so that they can meet the discharge circuit requirements. Reducing the resistance also leads to cost reduction, and in addition, the reduction in resistance further reduces the cost.

[0060] Control method of DC system: Control of DC energy consumption circuit: Set a three-stage voltage starting method. When the DC system voltage is higher than the first stage starting voltage, some power devices in the DC energy consumption circuit are turned on, and the system voltage is reduced to a controllable range by reducing the circuit resistance. If the system voltage still rises after some power devices are put into use, and reaches or exceeds the second stage voltage setting value, the DC system increases the number of power devices put into use, further reduces the number of circuit resistances, and reduces the voltage of the DC system to a controllable range. If the voltage of the DC system is still rising after the above steps, all power devices are put into use, so that the voltage of the DC system is reduced to a controllable range.

[0061] Capacitor discharge loop control: Method 1 is to discharge the capacitor quickly by controlling the conduction of the power device, and method 2 is to discharge naturally through the first energy dissipation resistor.

[0062] The embodiment of the present invention normalizes the capacitor discharge circuit, the voltage balancing circuit, and the DC energy consumption circuit, and designs the three circuits into the DC system. The first energy consumption resistor is used as both the capacitor discharge circuit and the voltage balancing circuit. The design of the capacitor discharge circuit resistor and the design of the power device voltage balancing circuit resistor are considered at the same time, so as to avoid wasting design time and increasing the overall cost of the DC system. The number of resistors and power devices invested in step-by-step voltage control is adopted to perform power control and charge and discharge control, which ensures the stable operation of the DC system and the personal safety of maintenance personnel in the shutdown state, and can quickly restore the DC system to a normal operating state in a fault state. In summary, the present invention solves the problem that the capacitor discharge circuit, the energy consumption circuit, and the power device voltage balancing circuit of the existing DC energy consumption circuit are designed separately, which increases the workload of designers and increases the overall cost of the DC system.

[0063] Continue to refer Figure 1 , Optionally, the first dynamic voltage balancing module includes: a first dynamic voltage balancing resistor and a first dynamic voltage balancing capacitor;

[0064] The first dynamic voltage balancing resistor is connected in series with the first dynamic voltage balancing capacitor.

[0065] Specifically, Figure 1 The N first dynamic voltage balancing modules 31-3N are composed of N first dynamic voltage balancing resistors Rsx1-RsxN and N first dynamic voltage balancing capacitors Csx1-CsxN. The N first dynamic voltage balancing resistors Rsx1-RsxN and the N first dynamic voltage balancing capacitors Csx1-CsxN are used to absorb the peak overvoltage generated by the N first power devices Tsz1-TszN when they are turned off.

[0066] Continue to refer Figure 1 Optionally, the first DC support capacitor branch 20 includes one first capacitor Cs1. For example, in a two-level circuit, the first DC support capacitor branch 20 may include one first capacitor Cs1.

[0067] Specifically, Figure 1 It is exemplarily shown that the first DC support capacitor branch 20 includes a first capacitor Cs1, and the first capacitor Cs1 plays the role of voltage stabilization and filtering in the circuit.

[0068] Figure 2 is a schematic diagram of a structure of another DC system provided according to an embodiment of the present invention, referring to Figure 2 Optionally, the first DC support capacitor branch 20 includes N first capacitors connected in series, where N is an integer greater than or equal to 2.

[0069] In some embodiments, Figure 2 The DC system structure shown can also be applied to two-level circuits.

[0070] Specifically, Figure 2 The example shows that the first DC support capacitor branch 20 is composed of N first capacitors Cs1 -CsN, and the N first capacitors Cs1 -CsN play the role of voltage stabilization and filtering in the circuit.

[0071] Continue to refer Figure 2 , Optionally, the DC system further includes N first regulating resistors Rsc1-Rscn;

[0072] Two ends of each first regulating resistor are respectively connected to the first capacitor and the first power device to form a discharge loop of the first capacitor.

[0073] As an example, Figure 2 The first capacitor Cs1 shown has three discharge circuits, namely the first discharge circuit (first capacitor Cs1, N first power devices Tsz1-TszN, first energy dissipation resistor R1); the second capacitor discharge circuit (first capacitor Cs1, N first static voltage-equalizing resistors Rsz1-RszN, first energy dissipation resistor R1); and the third capacitor discharge circuit (first capacitor Cs1, first power device Tsz1, first adjustment resistor Rsc1).

[0074] Specifically, the N first regulating resistors Rsc1 -Rscn are used to release the excess electricity of the DC system into the loop, and at the same time, the safety of on-site personnel can be ensured when the DC system is under maintenance.

[0075] like Figure 2As shown, in the DC system provided by the embodiment of the present invention, three capacitor discharge circuits are set (the first capacitor discharge circuit is composed of a first capacitor Cs1, N first power devices Tsz1-TszN, and a first energy dissipation resistor R1; the second capacitor discharge circuit is composed of a first capacitor Cs1, N static voltage-equalizing resistors Rsz1-RszN, and a first energy dissipation resistor R1; the third capacitor discharge circuit is composed of N first capacitors Cs1-CsN, N first power devices Tsz1-TszN, and N first adjustment resistors Rsc1-Rscn), an energy dissipation circuit ( The energy consumption circuit is composed of N first power devices Tsz1-TszN, a first energy consumption resistor R1), a voltage equalizing circuit (the voltage equalizing circuit is composed of N first static voltage equalizing resistors Rsx1-RsxN), the capacitor discharge circuit, the voltage equalizing circuit, and the DC energy consumption circuit are normalized, and the three circuits are combined and designed into the DC system. The resistance of the above capacitor discharge circuit, the voltage equalizing circuit, and the DC energy consumption circuit are uniformly considered. The energy consumption resistor is used as both a capacitor discharge circuit and a voltage equalizing circuit, and the voltage equalizing resistor and the energy consumption resistor are reduced in resistance so that they can meet the requirements of the discharge circuit. Reducing resistance also leads to cost reduction. In addition, the reduction in resistance further reduces costs.

[0076] The technical solution of the embodiment of the present invention utilizes the regulating effect of N first regulating resistors Rsc1-Rscn to release the excess electricity in the DC system into the loop. It can not only meet the demand for DC energy consumption, but also ensure the safety of on-site maintenance personnel during DC system maintenance. The present invention solves the problem that the existing DC energy consumption circuit and the DC support capacitor discharge circuit are designed separately, that is, the design does not consider how the DC support capacitor is discharged or the design problem of the DC energy consumption circuit is not considered when designing the discharge resistor.

[0077] Figure 3 is a schematic diagram of a structure of another DC system provided according to an embodiment of the present invention, referring to Figure 3 , optionally, the DC system further comprises:

[0078] A second DC support capacitor branch 40, a second switch branch 50 and a second energy dissipation resistor R2;

[0079] A first end of the second DC support capacitor branch 40 is connected to a second end of the power module 10, and a second end of the second DC support capacitor branch 40 is connected to a third end of the power module 10;

[0080] The second switch branch 50 and the second energy dissipation resistor R2 form a second series structure;

[0081] The second series structure is connected in parallel at both ends of the second DC support capacitor branch 40; wherein the first end of the second switch branch 50 is connected to the first end of the second DC support capacitor branch 40, the second end of the second switch branch 50 is connected to the first end of the second energy dissipation resistor R2, and the second end of the second energy dissipation resistor R2 is connected to the second end of the second DC support capacitor branch 40;

[0082] The second switch branch 50 includes at least two second switch modules, and the at least two second switch modules are connected in series in sequence;

[0083] Wherein, the second switch module includes: a second power device, a second diode, a second static voltage balancing resistor and a second dynamic voltage balancing module;

[0084] The first electrode of the second power device is connected to the cathode of the second diode, and the second electrode of the second power device is connected to the anode of the second diode;

[0085] The second static voltage-equalizing resistor is connected in parallel at both ends of the second diode; and the second dynamic voltage-equalizing module is connected in parallel at both ends of the second static voltage-equalizing resistor.

[0086] Specifically, Figure 3 The DC system in the embodiment is composed of a second DC support capacitor branch 40, M second power devices Txz1-TxzM, M second diodes Dxz1-DxzM, M second static voltage balancing resistors Rxz1-RxzM, M second dynamic voltage balancing modules 51-5M and a second energy dissipation resistor R2. The above devices can be connected in series in multiple stages to adapt to different system powers and system voltages.

[0087] The second DC support capacitor branch 40 plays the role of voltage stabilization and filtering in the circuit. The M second power devices Txz1-TxzM are mainly used as switches, playing the role of inputting or withdrawing the second energy-consuming resistor R2. The M second static voltage-equalizing resistors Rxz1-RxzM play the role of voltage balancing of the second power devices in the circuit on the one hand, and the role of discharging the second DC support capacitor branch 40 on the other hand. The M second dynamic voltage-equalizing modules 51-5M are used to absorb the peak overvoltage generated when the M second power devices Txz1-TxzM are turned off. The main function of the second energy-consuming resistor R2 in the circuit is to consume excess energy in the loop.

[0088] Functions and effects of the DC system: When an abnormality occurs in the DC system, the M second power devices Txz1-TxzM are turned on to release the excess voltage of the DC system into the second energy-consuming resistor R2, complete the energy release, and maintain the voltage of the DC system at the rated working condition. When the DC system is shut down for maintenance, the second DC support capacitor branch 40 completes the release of the capacitor charge within the specified time through the M second static voltage-equalizing resistors Rxz1-RxzM and the second energy-consuming resistor R2.

[0089] Necessity of M second static voltage-equalizing resistors Rxz1-RxzM: Due to the dispersion of the static volt-ampere characteristics of the power devices, the voltage division of each power device is not equal. Since the dispersion of the resistor can be very small, it is necessary to use static voltage-equalizing resistors to make the voltage division of each power device equal.

[0090] The number of the first switch modules and the second switch modules are equal and the structure is symmetrical, which can achieve the effect of balancing the upper and lower bus voltages, and the DC system is more stable.

[0091] In the prior art, the capacitor discharge circuit, voltage balancing circuit, and DC energy consumption circuit are designed separately, which increases the workload of designers and the overall cost of the DC system. In the prior art, the capacitor discharge circuit, voltage balancing circuit, and DC energy consumption circuit each have their own resistors to form a circuit.

[0092] However, if Figure 3 As shown, in the DC system provided by the present invention, by setting two capacitor discharge circuits (the first capacitor discharge circuit is composed of a second capacitor Cx1, M second power devices Txz1-TxzM, and a second energy dissipation resistor R2; the second capacitor discharge circuit is composed of a first capacitor Cx1, M second static voltage-equalizing resistors Rxz1-RxzM, and a second energy dissipation resistor R2), an energy dissipation circuit (the energy dissipation circuit is composed of M second power devices Txz1-TxzM and a second energy dissipation resistor R2), and a voltage-equalizing circuit (the voltage-equalizing circuit is composed of M second static voltage-equalizing resistors Rxz1-RxzM), the capacitor discharge circuit, the voltage-equalizing circuit, and the DC energy dissipation circuit are normalized, and the three circuits are combined and designed into the DC system, and the resistances of the above-mentioned capacitor discharge circuit, voltage-equalizing circuit, and DC energy dissipation circuit are uniformly considered, the energy dissipation resistor is used as both a capacitor discharge circuit and a voltage-equalizing circuit, and the resistance values ​​of the voltage-equalizing resistor and the energy dissipation resistor are reduced so that they can meet the requirements of the discharge circuit. Reducing resistance also leads to lower costs, and lower resistance values ​​further reduce costs.

[0093] Continue to refer Figure 3 , Optionally, the second dynamic voltage balancing module includes: a second dynamic voltage balancing resistor and a second dynamic voltage balancing capacitor;

[0094] The second dynamic voltage balancing resistor is connected in series with the second dynamic voltage balancing capacitor.

[0095] Specifically, Figure 3The M second dynamic voltage balancing modules 51-5M are composed of M second dynamic voltage balancing resistors Rxx1-RxxM and M second dynamic voltage balancing capacitors Cxx1-CxxM. The M second dynamic voltage balancing resistors Rxx1-RxxM and the M second dynamic voltage balancing capacitors Cxx1-CxxM are used to absorb the peak overvoltage generated by the M second power devices Txz1-TxzM when they are turned off.

[0096] Continue to refer Figure 3 Optionally, when the first DC support capacitor branch includes a first capacitor Cs1, the second DC support capacitor branch 40 includes a second capacitor Cx1. For example, in a three-level circuit, the DC system may include a first capacitor Cs1 and a second capacitor Cx1.

[0097] Specifically, Figure 3 It is exemplarily shown that in the case where the first DC support capacitor branch includes a first capacitor Cs1, the second DC support capacitor branch 40 includes a second capacitor Cx1, wherein the second capacitor Cx1 plays the role of voltage stabilization and filtering in the circuit.

[0098] Figure 4 is a schematic diagram of another DC system provided according to an embodiment of the present invention, referring to Figure 4 Optionally, when the first DC support capacitor branch includes N first capacitors connected in series, the second DC support capacitor branch 40 includes M second capacitors connected in series, where M is an integer greater than or equal to 2.

[0099] In some embodiments, Figure 4 The DC system structure shown can also be applied to three-level circuits.

[0100] Specifically, Figure 4 It is exemplarily shown that when the first DC support capacitor branch includes N first capacitors Cs1-CsN connected in series, the DC system includes M second capacitors Cx1-CxM, and the M second capacitors Cx1-CxM play the role of voltage stabilization and filtering in the circuit.

[0101] In some embodiments, N=M. When M=N, the upper and lower bus voltages can be balanced and the DC system is more stable.

[0102] Continue to refer Figure 4 , Optionally, the DC system further includes M second regulating resistors Rxc1-Rxcm;

[0103] Two ends of each second regulating resistor are respectively connected to the second capacitor and the second power device to form a discharge loop of the second capacitor.

[0104] As an example, Figure 4 The second capacitor Cx1 shown has three discharge circuits, namely the first discharge circuit (second capacitor Cx1, M second power devices Txz1-TxzM, second energy dissipation resistor R2); the second capacitor discharge circuit (second capacitor Cx1, M second static equalizing resistors Rxz1-RxzM, second energy dissipation resistor R2); and the third capacitor discharge circuit (second capacitor Cx1, second power device Txz1, second adjustment resistor Rxc1).

[0105] Specifically, the M second regulating resistors Rxc1-Rxcm are used to release the excess electricity of the DC system into the loop, and at the same time, when the DC system is under maintenance, the safety of on-site personnel can be ensured.

[0106] The technical solution of the present invention utilizes the regulating function of M second regulating resistors Rxc1-Rxcm to release the excess electricity in the DC system into the loop. It can not only meet the demand for DC energy consumption, but also ensure the safety of on-site maintenance personnel during DC system maintenance. The present invention solves the problem that the existing DC energy consumption circuit and the DC support capacitor discharge circuit are designed separately, that is, the design does not consider how the DC support capacitor is discharged or the design problem of the DC energy consumption circuit is not considered when designing the discharge resistor.

[0107] like Figure 4 As shown, in the DC system provided by the embodiment of the present invention, three capacitor discharge circuits are set (the first capacitor discharge circuit is composed of the second capacitor Cx1, M second power devices Txz1-TxzM, and the second energy dissipation resistor R2; the second capacitor discharge circuit is composed of the second capacitor Cx1, M second static voltage-equalizing resistors Rxz1-RxzM, and the second energy dissipation resistor R2; the third capacitor discharge circuit is composed of M second capacitors Cx1-CxM, M second power devices Txz1-TxzM, and M first adjustment resistors Rxc1-Rxcm), an energy dissipation circuit (The energy consumption circuit is composed of M second power devices Txz1-TxzM and a second energy consumption resistor R2), a voltage equalizing circuit (the voltage equalizing circuit is composed of M second static voltage equalizing resistors Rxz1-RxzM), the capacitor discharge circuit, the voltage equalizing circuit, and the DC energy consumption circuit are normalized, and the three circuits are combined and designed into the DC system. The resistance of the above capacitor discharge circuit, the voltage equalizing circuit, and the DC energy consumption circuit are uniformly considered. The energy consumption resistor is used as both a capacitor discharge circuit and a voltage equalizing circuit, and the voltage equalizing resistor and the energy consumption resistor are reduced in resistance so that they can meet the requirements of the discharge circuit. Reducing resistance also leads to cost reduction. In addition, the reduction in resistance further reduces costs.

[0108] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A DC system, characterized in that: include: A power module, a first DC support capacitor branch, a first switch branch and a first energy dissipation resistor; A first end of the first DC support capacitor branch is connected to a first end of the power module, and a second end of the first DC support capacitor branch is connected to a second end of the power module; The first switch branch and the first energy dissipation resistor form a first series structure; The first series structure is connected in parallel to the two ends of the first DC support capacitor branch; wherein the first end of the first switch branch is connected to the first end of the first DC support capacitor branch, the second end of the first switch branch is connected to the first end of the first energy dissipation resistor, and the second end of the first energy dissipation resistor is connected to the second end of the first DC support capacitor branch; The first switch branch includes at least two first switch modules, and the at least two first switch modules are connected in series in sequence; Wherein, the first switch module includes: a first power device, a first diode, a first static voltage balancing resistor and a first dynamic voltage balancing module; The first electrode of the first power device is connected to the cathode of the first diode, and the second electrode of the first power device is connected to the anode of the first diode; The first static voltage-equalizing resistor is connected in parallel at both ends of the first diode; and the first dynamic voltage-equalizing module is connected in parallel at both ends of the first static voltage-equalizing resistor.

2. The DC system according to claim 1, characterized in that: The first dynamic voltage balancing module includes: a first dynamic voltage balancing resistor and a first dynamic voltage balancing capacitor; Wherein, the first dynamic balancing resistor is connected in series with the first dynamic balancing capacitor.

3. The DC system according to claim 1, characterized in that: The first DC support capacitor branch includes a first capacitor.

4. The DC system according to claim 1, characterized in that: The first DC support capacitor branch includes N first capacitors connected in series in sequence, wherein N is an integer greater than or equal to 2.

5. The DC system according to claim 4, characterized in that: Also includes N first adjustment resistors; Two ends of each first regulating resistor are respectively connected to the first capacitor and the first power device to form a discharge loop of the first capacitor.

6. The DC system according to claim 1, characterized in that: Also includes: A second DC support capacitor branch, a second switch branch and a second energy dissipation resistor; The first end of the second DC support capacitor branch is connected to the second end of the power module, and the second end of the second DC support capacitor branch is connected to the third end of the power module; The second switch branch and the second energy dissipation resistor form a second series structure; The second series structure is connected in parallel to the two ends of the second DC support capacitor branch; wherein the first end of the second switch branch is connected to the first end of the second DC support capacitor branch, the second end of the second switch branch is connected to the first end of the second energy dissipation resistor, and the second end of the second energy dissipation resistor is connected to the second end of the second DC support capacitor branch; The second switch branch includes at least two second switch modules, and the at least two second switch modules are connected in series in sequence; Wherein, the second switch module includes: a second power device, a second diode, a second static voltage balancing resistor and a second dynamic voltage balancing module; The first electrode of the second power device is connected to the cathode of the second diode, and the second electrode of the second power device is connected to the anode of the second diode; The second static voltage-equalizing resistor is connected in parallel at both ends of the second diode; and the second dynamic voltage-equalizing module is connected in parallel at both ends of the second static voltage-equalizing resistor.

7. The DC system according to claim 6, characterized in that: The second dynamic voltage balancing module includes: a second dynamic voltage balancing resistor and a second dynamic voltage balancing capacitor; Wherein, the second dynamic balancing resistor is connected in series with the second dynamic balancing capacitor.

8. The DC system according to claim 6, characterized in that: In the case where the first DC support capacitor branch includes one first capacitor, the second DC support capacitor branch includes one second capacitor.

9. The DC system according to claim 6, characterized in that: In the case where the first DC support capacitor branch includes N first capacitors connected in series, the second DC support capacitor branch includes M second capacitors connected in series, where M is an integer greater than or equal to 2.

10. The DC system according to claim 9, characterized in that: Also includes M second adjustment resistors; Two ends of each second regulating resistor are respectively connected to the second capacitor and the second power device to form a discharge loop of the second capacitor.

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