Flexible direct-current double-commutation circuit and control method and device thereof

Abstract

The invention relates to the technical field of flexible direct-current power transmission, and discloses a flexible direct-current double-commutation circuit and a control method and device thereof. The circuit comprises a first input source, a second input source, a first commutation module, a second commutation module, a first positive pole output end, a first negative pole output end, a second positive pole output end, a second pole output end, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch and a tenth switch. The ninth switch and the tenth switch are connected with the homopolar output lines of the two current conversion modules, so that various circuit faults can be flexibly adapted by adjusting the opening and closing conditions of the switches, the availability and reliability of the circuit are improved, and mutual power assistance is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current power transmission, and in particular to a flexible direct current double-commutation circuit and a control method and device thereof. Background Art

[0002] Flexible DC transmission is a new type of transmission technology based on voltage source converters, turn-off switching devices and pulse width modulation (PWM) technology. It is a new generation of DC transmission technology and the most advanced power electronics technology currently in engineering application. Compared with conventional DC transmission methods, flexible DC transmission has strong technical advantages and broad application prospects in the fields of large-capacity clean energy grid connection, distributed generation grid connection, large-area power grid interconnection, island power supply, and capacity expansion and transformation of urban distribution networks. It can solve the safety and stability risks of the receiving power grid caused by multiple DC centralized landing points.

[0003] However, currently flexible DC projects usually use single-circuit line transmission, which has low flexibility. The current double-circuit line transmission also transmits power separately according to their respective DC conversion units, and there is no connection between the same-pole output lines. The circuit stability is low and it is easy to fail, resulting in power loss. Summary of the invention

[0004] The present invention provides a flexible direct current double-commutation circuit and a control method and device thereof, which can solve circuit faults by flexibly adjusting the opening and closing conditions of switches, thereby improving the availability and reliability of the circuit.

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a flexible DC double-commutation circuit, including: a first input source, a second input source, a first conversion module, a second conversion module, a first positive output terminal, a first negative output terminal, a second positive output terminal, a second negative output terminal, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch and a tenth switch;

[0006] The first input source is electrically connected to the input end of the first converter module;

[0007] The first output end of the first converter module is electrically connected to the first end of the first switch; the second end of the first switch is electrically connected to the first end of the second switch;

[0008] The second end of the second switch is electrically connected to the first positive output end;

[0009] The second output end of the first converter module is electrically connected to the first end of the third switch;

[0010] The second end of the third switch is electrically connected to the first end of the fourth switch;

[0011] The second end of the fourth switch is electrically connected to the first negative output end;

[0012] The second input source is electrically connected to the input end of the second converter module;

[0013] The first output end of the second converter module is electrically connected to the first end of the fifth switch;

[0014] The second end of the fifth switch is electrically connected to the first end of the sixth switch;

[0015] The second end of the sixth switch is electrically connected to the second positive output end;

[0016] The second output end of the second converter module is electrically connected to the first end of the seventh switch;

[0017] The second end of the seventh switch is electrically connected to the first end of the eighth switch;

[0018] The second end of the eighth switch is electrically connected to the first negative output end;

[0019] A first end of the ninth switch is electrically connected to a common connection point of the first switch and the second switch, and a second end of the ninth switch is electrically connected to a common connection point of the fifth switch and the sixth switch;

[0020] A first end of the tenth switch is electrically connected to a common connection point of the third switch and the fourth switch, and a second end of the tenth switch is electrically connected to a common connection point of the seventh switch and the eighth switch.

[0021] Furthermore, the first current conversion module includes: a plurality of first current conversion units and a plurality of second current conversion units;

[0022] The first end of each of the first current conversion units is electrically connected to the first input source;

[0023] The second end of each of the first current conversion units is electrically connected to the first end of the first switch;

[0024] The first end of each of the second current conversion units is electrically connected to the first input source;

[0025] The second end of each of the second current conversion units is electrically connected to the first end of the third switch.

[0026] Furthermore, the second converter module includes: a plurality of third converter units and a plurality of fourth converter units;

[0027] The first end of each of the third current conversion units is electrically connected to the first input source;

[0028] The second end of each of the third commutation units is electrically connected to the first end of the fifth switch;

[0029] The first end of each of the fourth current conversion units is electrically connected to the first input source;

[0030] The second end of each of the fourth converter units is electrically connected to the first end of the seventh switch.

[0031] A second aspect of the present invention provides a flexible DC double-commutation circuit control method, which is used to control the flexible DC double-commutation circuit as described in the first aspect of the present invention, comprising:

[0032] Respectively monitoring the module states of the first converter module and the second converter module in the circuit;

[0033] Respectively monitor the line states of a first DC line and a second DC line in the circuit; wherein the first DC line is a line section between a first positive output terminal and a first negative output terminal; and the second DC line is a line section between a second positive output terminal and a second negative output terminal;

[0034] The output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal in the circuit are respectively monitored;

[0035] The opening and closing conditions of each switch in the flexible DC double-commutation circuit are adjusted according to the module status, the line status and the output power.

[0036] Furthermore, the step of adjusting the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0037] When the module states of the first converter module and the second converter module are normal, the line states of the first DC line and the second DC line are normal, and the output powers of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal are not zero, it is determined that the current circuit operates normally, and the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch and the eighth switch are controlled to be closed, and the ninth switch and the tenth switch are controlled to be opened.

[0038] Furthermore, the step of adjusting the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0039] When the line state of the first DC line is a fault state, the first switch, the third switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch and the fourth switch are controlled to be opened;

[0040] When the line state of the second DC line is a fault state, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the sixth switch and the eighth switch are controlled to be opened.

[0041] Furthermore, the step of adjusting the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0042] When the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch and the third switch are controlled to be opened;

[0043] When the module state of the second converter module is a fault state, the first switch, the second switch, the third switch, the fourth switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the fifth switch and the seventh switch are controlled to be opened.

[0044] Furthermore, the step of adjusting the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0045] When the line state of the first DC line is a fault state and the module state of the second converter module is a fault state, the first switch, the third switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the fifth switch and the seventh switch are controlled to be opened;

[0046] When the line state of the second DC line is a fault state and the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch, the third switch, the sixth switch and the eighth switch are controlled to be opened.

[0047] Furthermore, the step of adjusting the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0048] When the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal is zero, the first switch, the third switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the sixth switch and the eighth switch are controlled to be opened.

[0049] Accordingly, the third aspect of the present invention provides a flexible DC double-commutation circuit control device, which is used to control the flexible DC double-commutation circuit as described in the first aspect of the present invention, including: a first monitoring module, a second monitoring module, a third monitoring module and a regulating module;

[0050] The first monitoring module is used to monitor the module states of the first converter module and the second converter module in the circuit respectively;

[0051] The second monitoring module is used to monitor the line status of the first DC line and the second DC line in the circuit respectively; wherein the first DC line is the line section between the first positive output terminal and the first negative output terminal; the second DC line is the line section between the second positive output terminal and the second negative output terminal;

[0052] The third monitoring module is used to monitor the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal in the circuit respectively;

[0053] The regulating module is used to regulate the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power.

[0054] The present invention provides a flexible DC dual-commutation circuit and a control method and device thereof. Based on the organic combination of modules, a cascade switch is added in the circuit to connect the same-pole output lines of two conversion modules, and the opening and closing conditions of each switch in the circuit are adjusted when a circuit fault occurs, thereby flexibly adjusting the power output condition in the circuit, improving the availability and reliability of the circuit, and realizing power mutual assistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A circuit diagram of an embodiment of a flexible DC double-commutation circuit provided by the present invention;

[0056] Figure 2 A schematic flow chart of an embodiment of a flexible DC dual-commutation circuit control method provided by the present invention;

[0057] Figure 3 A schematic structural diagram of an embodiment of a flexible DC dual-commutation circuit control device provided by the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0059] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0060] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0061] See also Figure 1 , is a circuit diagram of an embodiment of the flexible DC double-commutation circuit provided by the present invention, the circuit comprising a first input source, a second input source, a first commutation module, a second commutation module, a first positive output terminal, a first negative output terminal, a second positive output terminal, a second negative output terminal, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch and a tenth switch;

[0062] The first input source is electrically connected to the input end of the first converter module;

[0063] The first output end of the first converter module is electrically connected to the first end of the first switch; the second end of the first switch is electrically connected to the first end of the second switch;

[0064] The second end of the second switch is electrically connected to the first positive output end;

[0065] The second output end of the first converter module is electrically connected to the first end of the third switch;

[0066] The second end of the third switch is electrically connected to the first end of the fourth switch;

[0067] The second end of the fourth switch is electrically connected to the first negative output end;

[0068] The second input source is electrically connected to the input end of the second converter module;

[0069] The first output end of the second converter module is electrically connected to the first end of the fifth switch;

[0070] The second end of the fifth switch is electrically connected to the first end of the sixth switch;

[0071] The second end of the sixth switch is electrically connected to the second positive output end;

[0072] The second output end of the second converter module is electrically connected to the first end of the seventh switch;

[0073] The second end of the seventh switch is electrically connected to the first end of the eighth switch;

[0074] The second end of the eighth switch is electrically connected to the first negative output end;

[0075] A first end of the ninth switch is electrically connected to a common connection point of the first switch and the second switch, and a second end of the ninth switch is electrically connected to a common connection point of the fifth switch and the sixth switch;

[0076] A first end of the tenth switch is electrically connected to a common connection point of the third switch and the fourth switch, and a second end of the tenth switch is electrically connected to a common connection point of the seventh switch and the eighth switch.

[0077] In the embodiment of the present invention, the flexible DC power transmission system is generally composed of a converter module and a DC output line circuit. In the existing flexible DC project with two circuits, the power output of the two circuits is sent out from the respective DC converter modules respectively, and the same-pole output lines are not connected and are independent of each other. The present invention introduces a cascade switch between the two converter modules of the flexible DC dual-conversion circuit to connect the same-pole output lines of the two converter modules, thereby improving the stability of the circuit, being able to flexibly adapt to a variety of circuit faults, and reducing power loss.

[0078] Further, in an embodiment of the present invention, the first converter module includes: a plurality of first converter units and a plurality of second converter units;

[0079] The first end of each of the first current conversion units is electrically connected to the first input source;

[0080] The second end of each of the first current conversion units is electrically connected to the first end of the first switch;

[0081] The first end of each of the second current conversion units is electrically connected to the first input source;

[0082] The second end of each of the second current conversion units is electrically connected to the first end of the third switch.

[0083] Further, in an embodiment of the present invention, the second converter module includes: a plurality of third converter units and a plurality of fourth converter units;

[0084] The first end of each of the third current conversion units is electrically connected to the first input source;

[0085] The second end of each of the third commutation units is electrically connected to the first end of the fifth switch;

[0086] The first end of each of the fourth current conversion units is electrically connected to the first input source;

[0087] The second end of each of the fourth converter units is electrically connected to the first end of the seventh switch.

[0088] In the embodiment of the present invention, the first converter module and the second converter module are composed of a plurality of converter units with the same structure and independent states in cascade connection, and the internal component parameters of each converter unit are the same. The combined output between each converter unit can realize AC-DC conversion.

[0089] See also Figure 2 , is a flow chart of an embodiment of the flexible DC dual-commutation circuit provided by the present invention, the method includes steps 101 to 104, each step is specifically as follows:

[0090] Step 101: respectively monitor the module states of a first converter module and a second converter module in a circuit.

[0091] Step 102: respectively monitor the line status of a first DC line and a second DC line in the circuit; wherein the first DC line is a line section between a first positive output terminal and a first negative output terminal; and the second DC line is a line section between a second positive output terminal and a second negative output terminal.

[0092] Step 103: respectively monitor the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal in the circuit.

[0093] Step 104: adjusting the opening and closing status of each switch in the flexible DC dual-commutation circuit according to the module status, the line status and the output power.

[0094] In the embodiment of the present invention, the flexible DC dual-commutation circuit not only adds cascade switches to the commutation module, but also adds multiple switches on the DC line side to minimize power loss and improve circuit stability when a circuit fault occurs.

[0095] In the embodiment of the present invention, the module status of the commutation module is monitored to identify whether the commutation module is faulty; the line status of the DC line in the circuit is monitored to identify whether the DC line is faulty; and the output power of the DC output terminal is monitored to determine whether the output power is zero. According to the monitored module status, line status and output power, the opening and closing conditions of each switch in the flexible DC dual commutation circuit can be flexibly adjusted to improve the commutation efficiency of the circuit.

[0096] Optionally, the module status of the converter module can be monitored using the current and voltage measuring device; the line status of the DC line can be monitored using the current and voltage measuring device; the output power of the DC output terminal can also be monitored using the current and voltage measuring device.

[0097] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0098] When the module states of the first converter module and the second converter module are normal, the line states of the first DC line and the second DC line are normal, and the output powers of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal are not zero, it is determined that the current circuit operates normally, and the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch and the eighth switch are controlled to be closed, and the ninth switch and the tenth switch are controlled to be opened.

[0099] In an embodiment of the present invention, when it is monitored that both the module status and the line status are normal, the ninth switch and the tenth switch between the two converter modules are controlled to be disconnected, and the other switches are closed, so that each converter module corresponds to a DC line and independently completes power output.

[0100] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0101] When the line state of the first DC line is a fault state, the first switch, the third switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch and the fourth switch are controlled to be opened;

[0102] When the line state of the second DC line is a fault state, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the sixth switch and the eighth switch are controlled to be opened.

[0103] In an embodiment of the present invention, if it is monitored that the line state of any DC line is a fault state, the DC line is judged to be faulty. At this time, the switches between the two output ends corresponding to the DC line and the corresponding converter modules are adjusted. There are two switches between the two output ends and the converter modules. At this time, the two switches close to the output ends are disconnected, and the ninth switch and the tenth switch between the two converter modules are closed, so that the converter module corresponding to the faulty line outputs power through another DC line in a normal state.

[0104] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0105] When the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch and the third switch are controlled to be opened;

[0106] When the module state of the second converter module is a fault state, the first switch, the second switch, the third switch, the fourth switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the fifth switch and the seventh switch are controlled to be opened.

[0107] In an embodiment of the present invention, if it is monitored that the line state of any converter module is a fault state, the converter module is judged to be faulty. At this time, the switch between the converter module and its corresponding two output terminals is adjusted. There are two switches between the two output terminals and the converter module. At this time, the two switches close to the converter module are disconnected, and the ninth switch and the tenth switch between the two converter modules are closed, so that the other converter module in normal state can output power through two DC lines to reduce line impedance and loss.

[0108] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0109] When the line state of the first DC line is a fault state and the module state of the second converter module is a fault state, the first switch, the third switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the fifth switch and the seventh switch are controlled to be opened;

[0110] When the line state of the second DC line is a fault state and the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch, the third switch, the sixth switch and the eighth switch are controlled to be opened.

[0111] In the embodiment of the present invention, if a fault is detected in any DC line and another converter module, it is necessary to adjust the switches between the two output terminals corresponding to the faulty DC line and the converter module corresponding thereto, and to adjust the switches between the faulty converter module and the two output terminals corresponding thereto. Specifically, two switches close to the DC output terminals corresponding to the faulty DC line are disconnected, and two switches close to the faulty converter module are disconnected, and the ninth switch and the tenth switch between the two converter modules are closed, so that the converter module in a normal state outputs power through the DC line in a normal state.

[0112] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0113] When the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal is zero, the first switch, the third switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the sixth switch and the eighth switch are controlled to be opened.

[0114] In an embodiment of the present invention, when the output power monitored at the output end is zero, it is determined that the DC power received at this time is zero. At this time, the switches close to the first positive output end, the first negative output end, the second positive output end and the second negative output end are disconnected, and the ninth switch and the tenth switch between the two converter modules are closed. This can realize back-to-back interconnection of the AC systems corresponding to the two converter modules, and send the surplus power of one AC system to another AC system to achieve mutual assistance.

[0115] In the embodiment of the present invention, when any DC line fails, the power of the corresponding normally operating converter module can flow out through another connected DC line; when any converter module fails, the power of the other normally operating converter module is sent out in parallel using two lines, thereby reducing line impedance and loss; when one of the two DC lines fails and the other converter module fails, only 50% of the power is lost by adjusting the switch of the circuit; by adjusting the switch of the circuit, back-to-back interconnection of the AC systems corresponding to the two converter modules is achieved, thereby realizing power mutual assistance.

[0116] See also Figure 3 , is a schematic structural diagram of an embodiment of a flexible DC double-commutation circuit control device provided by the present invention, the device includes a first monitoring module 201, a second monitoring module 202, a third monitoring module 203 and a regulating module 204;

[0117] The first monitoring module 201 is used to monitor the module states of the first converter module and the second converter module in the circuit respectively;

[0118] The second monitoring module 202 is used to monitor the line status of the first DC line and the second DC line in the circuit respectively; wherein the first DC line is the line section between the first positive output terminal and the first negative output terminal; the second DC line is the line section between the second positive output terminal and the second negative output terminal;

[0119] The third monitoring module 203 is used to monitor the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal in the circuit respectively;

[0120] The regulating module 204 is used to regulate the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power.

[0121] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0122] When the module states of the first converter module and the second converter module are normal, the line states of the first DC line and the second DC line are normal, and the output powers of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal are not zero, it is determined that the current circuit operates normally, and the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch and the eighth switch are controlled to be closed, and the ninth switch and the tenth switch are controlled to be opened.

[0123] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0124] When the line state of the first DC line is a fault state, the first switch, the third switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch and the fourth switch are controlled to be opened;

[0125] When the line state of the second DC line is a fault state, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the sixth switch and the eighth switch are controlled to be opened.

[0126] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0127] When the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch and the third switch are controlled to be opened;

[0128] When the module state of the second converter module is a fault state, the first switch, the second switch, the third switch, the fourth switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the fifth switch and the seventh switch are controlled to be opened.

[0129] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0130] When the line state of the first DC line is a fault state and the module state of the second converter module is a fault state, the first switch, the third switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the fifth switch and the seventh switch are controlled to be opened;

[0131] When the line state of the second DC line is a fault state and the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch, the third switch, the sixth switch and the eighth switch are controlled to be opened.

[0132] Furthermore, in an embodiment of the present invention, adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes:

[0133] When the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal is zero, the first switch, the third switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the sixth switch and the eighth switch are controlled to be opened.

[0134] In summary, the present invention provides an embodiment of a flexible DC dual-commutation circuit and a control method and device thereof, which is based on the organic combination of modules, by adding cascade switches in the circuit to connect the same-pole output lines of two conversion modules, and adjusting the opening and closing conditions of each switch in the circuit when a circuit fault occurs, thereby flexibly adjusting the power output condition in the circuit, improving the availability and reliability of the circuit, and realizing power mutual assistance.

[0135] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flexible DC double-commutation circuit, characterized in that: include: A first input source, a second input source, a first inverter module, a second inverter module, a first positive output terminal, a first negative output terminal, a second positive output terminal, a second negative output terminal, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch, and a tenth switch; The first input source is electrically connected to the input end of the first converter module; The first output end of the first converter module is electrically connected to the first end of the first switch; the second end of the first switch is electrically connected to the first end of the second switch; The second end of the second switch is electrically connected to the first positive output end; The second output end of the first converter module is electrically connected to the first end of the third switch; The second end of the third switch is electrically connected to the first end of the fourth switch; The second end of the fourth switch is electrically connected to the first negative output end; The second input source is electrically connected to the input end of the second converter module; The first output end of the second converter module is electrically connected to the first end of the fifth switch; The second end of the fifth switch is electrically connected to the first end of the sixth switch; The second end of the sixth switch is electrically connected to the second positive output end; The second output end of the second converter module is electrically connected to the first end of the seventh switch; The second end of the seventh switch is electrically connected to the first end of the eighth switch; The second end of the eighth switch is electrically connected to the first negative output end; A first end of the ninth switch is electrically connected to a common connection point of the first switch and the second switch, and a second end of the ninth switch is electrically connected to a common connection point of the fifth switch and the sixth switch; A first end of the tenth switch is electrically connected to a common connection point of the third switch and the fourth switch, and a second end of the tenth switch is electrically connected to a common connection point of the seventh switch and the eighth switch.

2. The flexible DC double-commutation circuit according to claim 1, characterized in that: The first current conversion module includes: a plurality of first current conversion units and a plurality of second current conversion units; The first end of each of the first current conversion units is electrically connected to the first input source; The second end of each of the first current conversion units is electrically connected to the first end of the first switch; The first end of each of the second current conversion units is electrically connected to the first input source; The second end of each of the second current conversion units is electrically connected to the first end of the third switch.

3. The flexible DC double-commutation circuit according to claim 1, characterized in that: The second current conversion module comprises: a plurality of third current conversion units and a plurality of fourth current conversion units; The first end of each of the third current conversion units is electrically connected to the first input source; The second end of each of the third commutation units is electrically connected to the first end of the fifth switch; The first end of each of the fourth current conversion units is electrically connected to the first input source; The second end of each of the fourth converter units is electrically connected to the first end of the seventh switch.

4. A flexible DC double-commutation circuit control method, characterized in that: Used to control the flexible DC double-commutation circuit according to any one of claims 1 to 3, comprising: Respectively monitoring the module states of the first converter module and the second converter module in the circuit; Respectively monitor the line states of a first DC line and a second DC line in the circuit; wherein the first DC line is a line section between a first positive output terminal and a first negative output terminal; and the second DC line is a line section between a second positive output terminal and a second negative output terminal; The output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal in the circuit are respectively monitored; The opening and closing conditions of each switch in the flexible DC double-commutation circuit are adjusted according to the module status, the line status and the output power.

5. The flexible DC double-commutation circuit control method according to claim 4, characterized in that: The step of adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes: When the module states of the first converter module and the second converter module are normal, the line states of the first DC line and the second DC line are normal, and the output powers of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal are not zero, it is determined that the current circuit operates normally, and the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch and the eighth switch are controlled to be closed, and the ninth switch and the tenth switch are controlled to be opened.

6. The flexible DC double-commutation circuit control method according to claim 4, characterized in that: The step of adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes: When the line state of the first DC line is a fault state, the first switch, the third switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch and the fourth switch are controlled to be opened; When the line state of the second DC line is a fault state, the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the sixth switch and the eighth switch are controlled to be opened.

7. The flexible DC double-commutation circuit control method according to claim 4, characterized in that: The step of adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes: When the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch and the third switch are controlled to be opened; When the module state of the second converter module is a fault state, the first switch, the second switch, the third switch, the fourth switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the fifth switch and the seventh switch are controlled to be opened.

8. The flexible DC double-commutation circuit control method according to claim 4, characterized in that: The step of adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes: When the line state of the first DC line is a fault state and the module state of the second converter module is a fault state, the first switch, the third switch, the sixth switch, the eighth switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the fifth switch and the seventh switch are controlled to be opened; When the line state of the second DC line is a fault state and the module state of the first converter module is a fault state, the second switch, the fourth switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the first switch, the third switch, the sixth switch and the eighth switch are controlled to be opened.

9. The flexible DC double-commutation circuit control method according to claim 4, characterized in that: The step of adjusting the on / off status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power further includes: When the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal is zero, the first switch, the third switch, the fifth switch, the seventh switch, the ninth switch and the tenth switch are controlled to be closed, and the second switch, the fourth switch, the sixth switch and the eighth switch are controlled to be opened.

10. A flexible DC double-commutation circuit control device, characterized in that: Used to control the flexible DC double-commutation circuit according to any one of claims 1 to 3, comprising: a first monitoring module, a second monitoring module, a third monitoring module and a regulating module; The first monitoring module is used to monitor the module states of the first converter module and the second converter module in the circuit respectively; The second monitoring module is used to monitor the line status of the first DC line and the second DC line in the circuit respectively; wherein the first DC line is the line section between the first positive output terminal and the first negative output terminal; the second DC line is the line section between the second positive output terminal and the second negative output terminal; The third monitoring module is used to monitor the output power of the first positive output terminal, the first negative output terminal, the second positive output terminal and the second negative output terminal in the circuit respectively; The regulating module is used to regulate the opening and closing status of each switch in the flexible DC double-commutation circuit according to the module status, the line status and the output power.

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