A method for controlling automatic backup of a DC distribution network powered by multiple power sources

Abstract

The present invention discloses a method for controlling a DC power distribution network with multiple power supplies, comprising the following steps: S01, when the bus voltage u I <U Lset When the automatic switching device is started, the judgment process of the backup device is started; S02, if the output switch current i dc1 ≤0, it is judged as a fault above the outlet switch, and the process continues; S03, delay t D The time to trip the exit switch, while timing t S time; S04, if the timing time has not expired, continue the process, otherwise end the standby automatic switch judgment process; S05, determine whether the incoming line switch has reached the split state within the timing time, if it has reached, continue the process, otherwise return to the previous step; S06, after the switch is split, if the adjacent bus voltage meets u II ≥U Lset , it is determined that the adjacent bus voltage is normal, and the bus tie switch operation is performed, otherwise the standby automatic switch judgment process ends. The invention provides a DC distribution network standby automatic switch control method with multiple power supplies, which can clarify the standby automatic switch action conditions of multiple power supplies in the DC distribution network and is suitable for the standby automatic switch strategy of the DC distribution network.

Description

Technical Field

[0001] The invention relates to a method for controlling automatic backup of a DC power distribution network powered by multiple power sources, and belongs to the technical field of power system power distribution networks. Background Art

[0002] As a new type of energy network supply and management technology that includes distributed power sources, energy storage devices, electric vehicles and various loads, DC distribution network is receiving more and more attention due to its high energy utilization rate and environmental friendliness. The commutation device is the core of the DC distribution system. Compared with AC transformer equipment, the reliability of the commutation device is weaker due to the fragile power electronic devices inside, but this defect can be compensated by dual or multi-way power supply. The automatic backup device is the abbreviation of the device that automatically puts the backup power into use, and plays an important role in the multi-way power supply system. It is very important to study the automatic backup method of the DC distribution network.

[0003] Traditional AC backup automatic switching devices often use the detection of no voltage and no current to determine whether to perform backup automatic switching. In DC distribution networks, due to the fragility of the converter, when a power grid fault occurs, unless there are special requirements, the converter will take rapid locking measures to protect the safety of its own devices. After the converter is locked, the DC distribution network in the fault state is in a state of no current in the entire network, so it is impossible to determine whether it is a power supply failure by no current. At the same time, whether it is a load converter or a power converter, capacitors are important components. Due to the presence of a large number of capacitors in the DC distribution network, the DC bus voltage does not drop much when the power grid fails, so the no-voltage judgment strategy is not applicable to the DC distribution network. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a DC distribution network backup automatic switching control method that can clarify the action conditions of multiple power supplies in the DC distribution network and is suitable for the DC distribution network backup automatic switching strategy.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for controlling a DC power distribution network with multiple power supplies, characterized in that it comprises the following steps:

[0007] S01, when the bus voltage u I <U Lset When the automatic switching device is started, the judgment process of the automatic switching device is started, where U Lset It is the busbar low voltage setting value;

[0008] S02, if the output switch current i dc1 ≤0, it is judged as a fault above the outlet switch and the process continues, otherwise the standby automatic switching device ends the judgment process;

[0009] S03, delay t D The time to trip the exit switch, while timing t S time;

[0010] S04, if the timing time has not expired, continue the process, otherwise end the standby automatic investment judgment process;

[0011] S05, judging whether the incoming line switch has reached the open position state within the timing time, if so, continuing the process, otherwise returning to the previous step;

[0012] S06, after the switch is opened, if the adjacent bus voltage meets u II ≥U Lset , it is judged that the adjacent bus voltage is normal, and the bus tie switch operation is performed, otherwise the standby automatic switching judgment process is terminated.

[0013] In S01, the busbar low voltage setting value U Lset It is 0.5 to 0.8 times the rated voltage.

[0014] In S03, t S >t D +△T, △T is the inherent action time of the switch.

[0015] t D The time can be set to 3ms~1s.

[0016] In S03, the outlet switch tripped state is connected to the standby automatic switching device through a hard contact.

[0017] In S03, the outlet switch tripping state is connected to the backup automatic switching device via optical fiber.

[0018] Beneficial effects of the present invention: The present invention provides a method for controlling a backup automatic switching of a DC distribution network powered by multiple power sources. Based on the network topology of the DC distribution network and the fault characteristics of the converter device, a backup automatic switching condition suitable for the DC distribution network is given. The backup automatic switching condition is different from the judgment basis of the traditional AC backup automatic switching device based on no voltage and no current. It can identify whether the fault is a fault above the busbar incoming switch within a short time after the DC distribution system fails, thereby quickly and effectively isolating the faulty power supply and reliably switching on the backup power supply, thereby meeting the reliable power supply demand of the DC distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a typical topological diagram of the medium and low voltage DC distribution network of the present invention;

[0020] Figure 2 The present invention is a flow chart of a method for controlling a DC power distribution network with multiple power supplies. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0022] The present invention discloses a method for controlling automatic backup of a DC distribution network powered by multiple power sources. The method is discussed by taking two power sources as an example. The method can be widely applied to a DC distribution network in which multiple power sources serve as backup for each other. The proposed automatic backup scheme for multiple power sources in a DC distribution network can well solve the problem of weak reliability of power converters, provide strong guarantee for a DC distribution network powered by multiple power sources, and has good engineering application value.

[0023] At present, the typical topology of multi-channel power supply in DC distribution network is as follows: Figure 1 As shown in the figure, the two converters are used as two power sources of the DC distribution network, k 1 and k 2 It is the output switch of the commutation device connected to each busbar. Busbar I and busbar II carry the loads connected to both sides respectively. 12 It is the bus tie switch between two bus sections. dc1 and i dc2 are the currents at the two output switches, flowing from the converter into their respective busbars; u I and u II are the bus voltages of the two buses respectively.

[0024] according to Figure 1 In a typical topology, the backup automatic switch will close the bus tie switch when one and only one converter loses its power supply capability. Therefore, the backup automatic switch needs to meet the following three conditions:

[0025] (1) Confirm that one side has a fault and the other side is supplying power normally;

[0026] (2) Confirm that the fault occurs at the output switch k of the converter device 1 or k 2 above;

[0027] (3) Confirm the exit switch k 1 or k 2 Jump open and isolate the fault above.

[0028] The DC distribution network is composed of various types of power conversion devices and load conversion devices. Among the various types of conversion devices, capacitors are important components. During a fault in the DC distribution network, the capacitors in various types of conversion devices discharge to the fault point. Therefore, unlike the AC distribution network, the load of the DC distribution network will also provide a large short-circuit current. This fault characteristic of the DC distribution network will cause the bus voltage in the fault system to not drop too much. At the same time, when a fault occurs above the outlet switch of the converter device, the current flowing through the outlet switch is not zero. Therefore, it is necessary to provide an identification method for the backup automatic switching conditions based on the fault characteristics of the DC distribution network.

[0029] When a fault occurs in the DC distribution network, the DC voltage will still decrease, so the fault can be confirmed by the DC voltage decreasing to a certain value. dc1 The current from the converter to the busbar is positive. When a fault occurs above the converter output switch, i dc1 The current flows from the busbar to the converter, and the current is negative. Therefore, the current direction of the converter output switch can be used to determine whether the fault occurs above the output switch. Therefore, the three conditions that the DC distribution network needs to meet can be identified as follows, taking I bus as the local system as an example:

[0030] (1) Bus voltage u I <U Lset It is judged as a system fault, and the bus voltage u I ≥U Lset The system is judged to be normal, U Lset It is the busbar low voltage setting value, which can be set to 0.5 to 0.8 times the rated voltage value;

[0031] (2) The output switch current i of the converter dc1 If it is positive, it means that there is a fault below the exit switch. dc1 If it is a non-positive value, it is judged that a fault occurs above the outlet switch;

[0032] (3) After the backup automatic start-up is started, it is necessary to delay the tripping of the output switch in the faulty system. The tripped state is connected to the backup automatic start-up device by a hard contact or optical fiber.

[0033] Based on the DC distribution network backup automatic switching conditions, the present invention provides the following Figure 2 The flow chart of the DC distribution network backup automatic switching scheme is shown. According to the flow chart, the steps of the backup automatic switching scheme are described as follows, taking I mother as the local system as an example:

[0034] Step 1: When the bus voltage u I <U Lset When U Lset The busbar low voltage setting value starts the judgment process of the standby automatic transfer device.

[0035] Step 2: If the output switch current i dc1 ≤0, it is judged as a fault above the outlet switch and the process continues; otherwise, the standby automatic transfer device ends the judgment process.

[0036] Step 3: Delay t D The time to trip the exit switch, while timing t S Time, must meet t S >t D +△T, △T is the inherent action time of the switch, t D The time can be set to 3ms~1s.

[0037] Step 4: If the timing time has not expired, continue the process, otherwise end the standby automatic investment judgment process.

[0038] Step 5: Determine whether the incoming line switch has reached the open position within the timing time. If so, continue the process, otherwise return to the previous step.

[0039] Step 6: After the switch is opened, if the adjacent bus voltage satisfies u II ≥U Lset , it is judged that the adjacent bus voltage is normal and the bus tie switch operation is performed, otherwise the standby automatic switching judgment process is terminated.

[0040] According to the above process, it can be correctly judged whether the DC distribution network needs the backup automatic switching device to switch on the bus tie switch, thereby ensuring the correct reliability of the timing of switching on the bus tie switch.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling automatic backup of a DC distribution network powered by multiple power sources, characterized in that: The following steps are involved: S01, when the bus voltage u I <U Lset When the automatic switching device is started, the judgment process of the automatic switching device is started, where U Lset It is the busbar low voltage setting value; S02, if the output switch current i dc1 ≤0, it is judged as a fault above the outlet switch and the process continues, otherwise the standby automatic switching device ends the judgment process; S03, delay t D The time to trip the exit switch, while timing t S time; S04, if the timing time has not expired, continue the process, otherwise end the standby automatic investment judgment process; S05, judging whether the incoming line switch has reached the open position state within the timing time, if so, continuing the process, otherwise returning to the previous step; S06, after the switch is opened, if the adjacent bus voltage meets u II ≥U Lset , it is judged that the adjacent bus voltage is normal, and the bus tie switch operation is performed, otherwise the standby automatic switching judgment process is terminated.

2. A method for controlling automatic backup of a DC distribution network powered by multiple power sources according to claim 1, characterized in that: In S01, the busbar low voltage setting value U Lset It is 0.5 to 0.8 times the rated voltage.

3. The method for controlling the automatic switching of a DC distribution network powered by multiple power sources according to claim 1, characterized in that: In S03, t S >t D +△T, △T is the inherent action time of the switch.

4. The method for controlling automatic backup of a DC distribution network powered by multiple power sources according to claim 3 is characterized in that: t D The time can be set to 3ms~1s.

5. The method for controlling automatic backup of a DC distribution network powered by multiple power sources according to claim 1, characterized in that: In S03, the outlet switch tripped state is connected to the standby automatic switching device through a hard contact.

6. The method for controlling automatic backup of a DC distribution network powered by multiple power sources according to claim 1, characterized in that: In S03, the outlet switch tripping state is connected to the backup automatic switching device via optical fiber.

Images