CN111786375A - DC power grid reconstruction method and device - Google Patents

Abstract

The invention discloses a method and a device for reconstructing a direct current power grid, wherein the method comprises the following steps: respectively obtaining voltage values on the first direct current bus and the second direct current bus; respectively calculating target output voltages of the power electronic transformers on the first direct current bus and the second direct current bus according to the voltage values, so that the terminal voltage of the first direct current bus and the terminal voltage of the second direct current bus are adjusted to be equal; adjusting the output voltages to target output voltages respectively; and closing the tail end of the first direct current bus and the tail end of the second direct current bus. By adopting the technical scheme, the flexible loop closing equipment can be replaced, the equipment cost is lower, nearly one hundred percent power transfer between different direct current power distribution networks can be realized, the impact of the closing operation of the direct current switch is very small, the overload situation of the power electronic transformer is avoided, and the normal and stable operation of the equipment can be ensured.

Description

DC power grid reconstruction method and device

technical field

The invention relates to the field of DC power grids, and in particular, to a method and a device for reconstructing a DC power grid.

Background technique

In recent years, the penetration rate of distributed power generation in the distribution network has gradually increased, which has brought severe challenges to the distribution network. At present, the construction and application of the DC power grid is still in its infancy, and the scale of the DC distribution network is relatively small.

In the prior art, the cost of the flexible loop closure equipment used to reconstruct the connection between different DC distribution networks is high, and the conversion rate of power transfer is low, and the output of the power electronic transformers on each bus after the DC distribution network is reconstructed The power imbalance is relatively large, and in severe cases, the overload of the power electronic transformer will occur, affecting the normal and stable operation of the equipment.

SUMMARY OF THE INVENTION

Purpose of the invention: The present invention provides a method and device for reconfiguring a DC power grid, which aims to solve the problem that the conversion rate of power transfer for reconstruction between different DC power grids is low, and the output power of the power electronic transformers on each DC power grid after reconstruction is unbalanced. The degree of severity is relatively large, which affects the normal and stable operation of the equipment.

Technical solution: The present invention provides a method for reconfiguring a DC power grid, comprising: acquiring voltage values on the first DC bus and on the second DC bus respectively; the voltage values include the output voltage of the power electronic transformer on the DC bus, and the terminal voltage of the DC bus; according to the voltage value, calculate the target output voltage of the power electronic transformer on the first DC bus and the second DC bus respectively, so that the terminal voltage of the first DC bus and the terminal of the second DC bus are The voltages are adjusted to be equal; the output voltages of the power electronic transformers on the first DC bus and the second DC bus are respectively adjusted to the target output voltage; the end of the first DC bus and the end of the second DC bus are closed.

Specifically, the terminal voltage of the first DC bus and the terminal voltage of the second DC bus are adjusted to be equal, and the deviation between the target output voltage of the power electronic transformer and the rated voltage of the DC bus where the power electronic transformer is located is minimal.

Specifically, the following formula is used to calculate:

Wherein, when f takes the minimum value, the target output voltage U bus1_T of the power electronic transformer on the first DC bus and the target output voltage U _{bus2_T} of the power electronic transformer on the second DC bus _are as follows:

Wherein, U _N is the rated voltage of the DC bus, U _LK1 is the terminal voltage of the first DC bus, U _LK2 is the terminal voltage of the second DC bus, and U _bus1 is the output voltage of the power electronic transformer on the first DC bus , U _bus2 is the output voltage of the power electronic transformer on the second DC bus, ΔU ₁ =U _{bus1_T} −U _bus1 , and ΔU ₂ =U _{bus2_T} −U _bus2 .

Specifically, the adjusted terminal voltage of the first DC bus and the terminal voltage of the second DC bus are obtained respectively. If they are not equal, the target output of the power electronic transformers on the first DC bus and the second DC bus is obtained. The voltage is recalculated and adjusted.

Specifically, the power electronic transformers with larger capacity on the DC bus are operated according to the voltage control mode, and the remaining power electronic transformers are operated according to the power control mode.

The present invention also provides a DC power grid reconstruction device, comprising: a voltage value acquisition unit, a target voltage calculation unit, a control adjustment unit and a closing unit, wherein:

the voltage value obtaining unit is used to obtain the voltage values on the first DC bus and the second DC bus respectively; the voltage values include the output voltage of the power electronic transformer on the DC bus and the terminal voltage of the DC bus;

The target voltage calculation unit is used to calculate the target output voltages of the power electronic transformers on the first DC bus and the second DC bus respectively according to the voltage value, so that the terminal voltage of the first DC bus and the second DC bus are The terminal voltage is adjusted to be equal;

The control and adjustment unit is used to adjust the output voltages of the power electronic transformers on the first DC bus and on the second DC bus respectively to the target output voltage;

The closing unit is used to close the end of the first DC bus and the end of the second DC bus.

Specifically, the target voltage calculation unit is used to adjust the terminal voltage of the first DC bus and the terminal voltage of the second DC bus to be equal, and the target output voltage of the power electronic transformer is equal to the rated value of the DC bus where the power electronic transformer is located. The deviation between voltages is minimal.

Specifically, the target voltage calculation unit is used to calculate the target output voltages of the power electronic transformers on the first DC bus and on the second DC bus, respectively, and use the following formula to calculate:

Wherein, when f takes the minimum value, the target output voltage U bus1_T of the power electronic transformer on the first DC bus and the target output voltage U _{bus2_T} of the power electronic transformer on the second DC bus _are as follows:

Wherein, U _N is the rated voltage of the DC bus, U _LK1 is the terminal voltage of the first DC bus, U _LK2 is the terminal voltage of the second DC bus, and U _bus1 is the output voltage of the power electronic transformer on the first DC bus , U _bus2 is the output voltage of the power electronic transformer on the second DC bus, ΔU ₁ =U _{bus1_T} −U _bus1 , and ΔU ₂ =U _{bus2_T} −U _bus2 .

Specifically, the control and adjustment unit is further configured to obtain the adjusted terminal voltage of the first DC bus and the terminal voltage of the second DC bus respectively. The target output voltage of the power electronic transformer on the bus is recalculated and adjusted.

Specifically, the closing unit is also used to operate the power electronic transformers with larger capacity on the DC bus according to the voltage control mode, and the remaining power electronic transformers to operate according to the power control mode.

Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: instead of flexible loop closing equipment, the equipment cost is lower, and nearly 100% power transfer between different DC distribution networks can be realized, and the DC switch is closed for operation. The impact is very small, avoiding the overload of the power electronic transformer, and ensuring the normal and stable operation of the equipment.

Description of drawings

1 is a schematic flowchart of a DC power grid reconstruction method provided by the present invention;

FIG. 2 is a structural diagram of the DC power grid provided by the present invention.

Detailed ways

The technical solutions of the present invention will be further described below with reference to the accompanying drawings.

Referring to FIG. 1 and FIG. 2 , it is a schematic flowchart of a DC power grid reconstruction method provided by the present invention, and a structural diagram of the DC power grid provided by the present invention, respectively.

Step S101: Obtain voltage values on the first DC bus and on the second DC bus respectively; the voltage values include the output voltage of the power electronic transformer on the DC bus and the terminal voltage of the DC bus.

In a specific implementation, the voltage value specifically includes the output voltage U _bus1 of the power electronic transformer on the first DC bus, the output voltage U _bus2 of the power electronic transformer on the second DC bus, and the terminal voltage U of the first DC bus _LK1 , the terminal voltage U _LK2 of the second DC bus.

Step S102, according to the voltage value, calculate the target output voltages of the power electronic transformers on the first DC bus and the second DC bus respectively, so that the terminal voltage of the first DC bus and the terminal voltage of the second DC bus are adjusted to be equal .

In a specific implementation, PET1 (power electronic transformer on the first DC bus) and PET2 (power electronic transformer on the second DC bus) (PET, Power Electronic Transformer) are respectively connected to the first DC bus and the second DC bus , There is a tie switch LK between the ends of the DC bus, and the power electronic transformer can accurately control the DC bus voltage (terminal voltage) in real time. The initial output power of _PET1 and _PET2 are P _out1 and P _out2 respectively, and RT1 and RT2 are DC The resistance value on the bus, after the loop closing operation (the tie switch LK is closed), the output currents i _p1 (t) and i _p2 (t) of PET1 and PET2 are:

In a steady state, the output currents I _p1 and I _p2 of PET1 and PET2 are:

It can be seen that in the closed loop state, the output currents of PET1 and PET2 are affected by the voltage on both sides of the loop closure point; when the voltage difference between the two sides U _LK1 -U _LK2 is large, the output power of PET1 and PET2 is unbalanced. In severe cases, the overload of the power electronic transformer will occur, affecting the normal and stable operation of the equipment.

In a specific implementation, the terminal voltage of the first DC bus and the terminal voltage of the second DC bus are adjusted to be equal to achieve nearly 100% power transfer between different DC distribution networks, and the impact of the closing operation of the DC switch is very high. It can avoid the overload situation of the power electronic transformer and ensure the normal and stable operation of the equipment.

In the embodiment of the present invention, the terminal voltage of the first DC bus and the terminal voltage of the second DC bus are adjusted to be equal, and the deviation between the target output voltage of the power electronic transformer and the rated voltage of the DC bus where the power electronic transformer is located is the smallest .

In a specific implementation, on the premise that the terminal voltage U _LK1 of the first DC bus and the terminal voltage U _LK2 of the second DC bus are adjusted to be equal, the target output voltage of the power electronic transformer is increased, which is equal to that of the DC bus where the power electronic transformer is located. The deviation between the rated voltages is the smallest, that is, the target output voltage of the power electronic transformer on the first DC bus has the smallest difference with the rated voltage of the first DC bus, and the second DC bus and the corresponding power electronic transformer are the same. reason. Accordingly, the operation stability of the DC power grid and power grid-related equipment can be further improved.

In the embodiment of the present invention, the following formula is used to calculate the target output voltage of the power electronic transformers on the first DC bus and the second DC bus:

Wherein, when f takes the minimum value, the target output voltage U bus1_T of the power electronic transformer on the first DC bus and the target output voltage U _{bus2_T} of the power electronic transformer on the second DC bus _are as follows:

Wherein, U _N is the rated voltage of the DC bus, U _LK1 is the terminal voltage of the first DC bus, U _LK2 is the terminal voltage of the second DC bus, and U _bus1 is the output voltage of the power electronic transformer on the first DC bus , U _bus2 is the output voltage of the power electronic transformer on the second DC bus, ΔU ₁ =U _{bus1_T} −U _bus1 , and ΔU ₂ =U _{bus2_T} −U _bus2 .

In a specific implementation, the rated voltage of the first DC bus and the rated voltage of the second DC bus may both be U _N , and according to different actual application scenarios, the rated voltage of the first DC bus and the rated voltage of the second DC bus can also be different.

In a specific implementation, for the adjusted target output voltages U _{bus1_T} and U _{bus2_T} , there are:

Wherein, ΔU ₁ -ΔU ₂ =U _LK2 -U _LK1 =ΔU, then the function f is further constructed.

Step S103: Adjust the output voltages of the power electronic transformers on the first DC bus and on the second DC bus to the target output voltages respectively.

In the embodiment of the present invention, after the output voltage of the power electronic transformer is adjusted to the target output voltage, the adjusted terminal voltage of the first DC bus and the terminal voltage of the second DC bus are respectively obtained. The target output voltages of the power electronic transformers on the DC bus and on the second DC bus are recalculated and adjusted.

In a specific implementation, since the DC grid may remain in the operating state of providing power to the user load during the voltage adjustment process, since the load may vary, it may cause the output voltage of the power electronic transformer to be adjusted to the target output even when After the voltage is applied, the terminal voltage of the first DC bus is not equal to the terminal voltage of the second DC bus. Therefore, recalculating and adjusting according to the above steps can further ensure the conversion rate of power transfer, the stability of equipment operation, and avoid the impact of switch closing operation.

Step S104, closing the end of the first DC bus and the end of the second DC bus.

In the embodiment of the present invention, after closing, the power electronic transformer with larger capacity on the DC bus can also be operated in the voltage control mode, and the remaining power electronic transformers can be operated in the power control mode.

In a specific implementation, the closing may be the closing of the tie switch LK. Operating in the voltage control mode and the power control mode respectively, it is easier to control the power electronic transformer, and further ensure the stable operation of the DC grid after reconstruction. The capacity of a transformer is the product of its rated voltage and rated current.

An embodiment of the present invention also provides a DC power grid reconfiguration device, which is characterized by comprising: a voltage value acquisition unit, a target voltage calculation unit, a control adjustment unit, and a closing unit, wherein:

the voltage value obtaining unit is used to obtain the voltage values on the first DC bus and the second DC bus respectively; the voltage values include the output voltage of the power electronic transformer on the DC bus and the terminal voltage of the DC bus;

The target voltage calculation unit is used to calculate the target output voltages of the power electronic transformers on the first DC bus and the second DC bus respectively according to the voltage value, so that the terminal voltage of the first DC bus and the second DC bus are The terminal voltage is adjusted to be equal;

The control and adjustment unit is used to adjust the output voltages of the power electronic transformers on the first DC bus and on the second DC bus respectively to the target output voltage;

The closing unit is used to close the end of the first DC bus and the end of the second DC bus.

In the embodiment of the present invention, the target voltage calculation unit is used to adjust the terminal voltage of the first DC bus and the terminal voltage of the second DC bus to be equal, and the target output voltage of the power electronic transformer is the same as the DC voltage where the power electronic transformer is located. The deviation between the rated voltages of the busbars is minimal.

In the embodiment of the present invention, the target voltage calculation unit is used to calculate the target output voltages of the power electronic transformers on the first DC bus and the second DC bus respectively, and use the following formula to calculate:

Wherein, when f takes the minimum value, the target output voltage U bus1_T of the power electronic transformer on the first DC bus and the target output voltage U _{bus2_T} of the power electronic transformer on the second DC bus _are as follows:

Wherein, U _N is the rated voltage of the DC bus, U _LK1 is the terminal voltage of the first DC bus, U _LK2 is the terminal voltage of the second DC bus, and U _bus1 is the output voltage of the power electronic transformer on the first DC bus , U _bus2 is the output voltage of the power electronic transformer on the second DC bus, ΔU ₁ =U _{bus1_T} −U _bus1 , and ΔU ₂ =U _{bus2_T} −U _bus2 .

In the embodiment of the present invention, the control and adjustment unit is further configured to obtain the adjusted terminal voltage of the first DC bus and the terminal voltage of the second DC bus respectively. The target output voltage of the power electronic transformer on the second DC bus is recalculated and adjusted.

In the embodiment of the present invention, the closing unit is further configured to operate the power electronic transformer with larger capacity on the DC bus in the voltage control mode, and the remaining power electronic transformers in the power control mode.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications or equivalent replacements are made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. a DC power grid reconstruction method, is characterized in that, comprises: respectively acquiring voltage values on the first DC bus and on the second DC bus; the voltage values include the output voltage of the power electronic transformer on the DC bus and the terminal voltage of the DC bus; According to the voltage value, the target output voltages of the power electronic transformers on the first DC bus and the second DC bus are respectively calculated, so that the terminal voltage of the first DC bus and the terminal voltage of the second DC bus are adjusted to be equal; adjusting the output voltages of the power electronic transformers on the first DC bus and the second DC bus to the target output voltage respectively; Close the end of the first DC bus and the end of the second DC bus. 2 . The DC power grid reconstruction method according to claim 1 , wherein the adjusting the terminal voltage of the first DC bus and the terminal voltage of the second DC bus to be equal comprises: 2 . The terminal voltage of the first DC bus and the terminal voltage of the second DC bus are adjusted to be equal, and the deviation between the target output voltage of the power electronic transformer and the rated voltage of the DC bus where the power electronic transformer is located is minimal. 3. The method for reconfiguring a DC power grid according to claim 2, wherein the calculation of the target output voltages of the power electronic transformers on the first DC bus and the second DC bus, respectively, is performed by using the following formula:

Wherein, when f takes the minimum value, the target output voltage U bus1_T of the power electronic transformer on the first DC bus and the target output voltage U _{bus2_T} of the power electronic transformer on the second DC bus _are as follows:

Wherein, U _N is the rated voltage of the DC bus, U _LK1 is the terminal voltage of the first DC bus, U _LK2 is the terminal voltage of the second DC bus, and U _bus1 is the output voltage of the power electronic transformer on the first DC bus , U _bus2 is the output voltage of the power electronic transformer on the second DC bus, ΔU ₁ =U _{bus1_T} −U _bus1 , and ΔU ₂ =U _{bus2_T} −U _bus2 . 4 . The DC power grid reconstruction method according to claim 1 , wherein after adjusting the output voltages of the power electronic transformers on the first DC bus and on the second DC bus to the target output voltage respectively ,Also includes: Obtain the adjusted terminal voltage of the first DC bus and the terminal voltage of the second DC bus respectively. If they are not equal, perform a new operation on the target output voltages of the power electronic transformers on the first DC bus and the second DC bus. Calculate and adjust. 5 . The DC power grid reconstruction method according to claim 1 , wherein after the end of the first DC bus and the end of the second DC bus are closed, the method further comprises: 6 . The power electronic transformers with larger capacity on the DC bus are operated according to the voltage control mode, and the remaining power electronic transformers are operated according to the power control mode. 6. A DC power grid reconstruction device, comprising: a voltage value acquisition unit, a target voltage calculation unit, a control adjustment unit and a closing unit, wherein: the voltage value obtaining unit is used to obtain the voltage values on the first DC bus and the second DC bus respectively; the voltage values include the output voltage of the power electronic transformer on the DC bus and the terminal voltage of the DC bus; The target voltage calculation unit is used to calculate the target output voltages of the power electronic transformers on the first DC bus and the second DC bus respectively according to the voltage value, so that the terminal voltage of the first DC bus and the second DC bus are The terminal voltage is adjusted to be equal; The control and adjustment unit is used to adjust the output voltages of the power electronic transformers on the first DC bus and on the second DC bus respectively to the target output voltage; The closing unit is used to close the end of the first DC bus and the end of the second DC bus. 7 . The DC power grid reconstruction device according to claim 6 , wherein the target voltage calculation unit is used to adjust the terminal voltage of the first DC bus and the terminal voltage of the second DC bus to be equal, and the power The target output voltage of the electronic transformer with the smallest deviation from the rated voltage of the DC bus where the power electronic transformer is located. 8 . The DC power grid reconstruction device according to claim 7 , wherein the target voltage calculation unit is configured to calculate the target output voltages of the power electronic transformers on the first DC bus and the second DC bus respectively. 9 . , which is calculated using the following formula:

Wherein, when f takes the minimum value, the target output voltage U bus1_T of the power electronic transformer on the first DC bus and the target output voltage U _{bus2_T} of the power electronic transformer on the second DC bus _are as follows:

Wherein, U _N is the rated voltage of the DC bus, U _LK1 is the terminal voltage of the first DC bus, U _LK2 is the terminal voltage of the second DC bus, and U _bus1 is the output voltage of the power electronic transformer on the first DC bus , U _bus2 is the output voltage of the power electronic transformer on the second DC bus, ΔU ₁ =U _{bus1_T} −U _bus1 , and ΔU ₂ =U _{bus2_T} −U _bus2 . 9 . The DC power grid reconstruction device according to claim 6 , wherein the control and adjustment unit is further configured to obtain the adjusted terminal voltage of the first DC bus and the terminal voltage of the second DC bus, respectively, 9 . If they are not equal, recalculate and adjust the target output voltages of the power electronic transformers on the first DC bus and on the second DC bus. 10 . The DC power grid reconstruction device according to claim 6 , wherein the closing unit is further configured to operate the power electronic transformers with larger capacity on the DC bus in a voltage control mode, and the remaining power electronic transformers Operates in power control mode.

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