CN113346473A - Grid-connected control method and grid-connected control device - Google Patents
Grid-connected control method and grid-connected control device Download PDFInfo
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- H—ELECTRICITY
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- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The embodiment of the invention relates to the field of control, and discloses a grid-connected control method and a grid-connected control device. The grid-connected control method is applied to a grid-connected control device in an electric power system, the electric power system comprises first power supply equipment which is already merged into a direct-current public power grid and second power supply equipment which needs to be merged into the direct-current public power grid, the second power supply equipment is connected to the input end of a second voltage conversion unit, and the output end of the second voltage conversion unit is used for being connected with the direct-current public power grid. This application when detecting that the output voltage of second voltage conversion unit is not equal to the voltage of direct current public power grid, can adjust the output voltage of second voltage conversion unit through the power droop curve of dynamic adjustment second voltage conversion unit, and after the output voltage of second voltage conversion unit equals with the voltage of direct current public power grid, incorporate into direct current public power grid with second power supply unit, can effectively reduce the surge current that the operation of being incorporated into the power networks made direct current public power grid produce, and then guarantee boats and ships power supply system's reliable operation.
Description
Technical Field
The embodiment of the invention relates to the field of control, in particular to a grid-connected control method and a grid-connected control device.
Background
With the rapid development of the new energy ship industry in recent years, the concept of a direct current power grid appears in a ship power grid, and the ship power grid has a plurality of advantages compared with a traditional alternating current power grid. In a direct current power grid, a power generation side is composed of power supply equipment such as a generator and a storage battery, energy on the power generation side can be converted through a power electronic conversion device and then transmitted to a direct current public power grid, a load side is composed of other electric equipment such as a propeller motor, and electric energy can be obtained from the direct current public power grid through the power electronic conversion device. The power generation side usually comprises a plurality of power supply devices, and in the process of shipping, the power supply devices do not always transmit electric energy to the direct-current public power grid, and the ship power supply system can control which power supply devices transmit electric energy to the direct-current public power grid according to different power requirements of the load side, so that the power supply devices can have the processes of paralleling and splitting, the power supply devices are combined into the direct-current public power grid in parallel, and the splitting divides the power supply devices from the direct-current public power grid to enable the power supply devices to work independently.
At present, when power supply equipment is merged into a direct current public power grid, surge current can be generated in the direct current public power grid due to the difference between output voltages of different power supply equipment, so that the parallel process of the power supply equipment is influenced, even devices in a ship power supply system can be damaged, and the reliable operation of the ship power supply system is influenced.
Disclosure of Invention
The invention aims to provide a grid-connected control method and a grid-connected control device, which are used for carrying out grid-connected operation after the output voltage of a voltage conversion unit is equal to the voltage of a direct-current public power grid by dynamically adjusting the droop characteristic curve of the voltage conversion unit connected to power supply equipment needing to be merged into the direct-current public power grid, so that surge current generated in the direct-current public power grid by the grid-connected operation is reduced as much as possible, and further the reliable operation of a ship power supply system is effectively ensured.
In order to solve the above technical problem, an embodiment of the present invention provides a grid-connected control method applied to a grid-connected control device in an electric power system, where the electric power system includes a first power supply device already incorporated into a dc public power grid and a second power supply device to be incorporated into the dc public power grid, the first power supply device is connected to the dc public power grid through a first voltage conversion unit, the second power supply device is connected to an input end of a second voltage conversion unit, an output end of the second voltage conversion unit is used for connecting to the dc public power grid, and an output end of the grid-connected control device is connected to the second voltageA first input end of the grid-connected control device is connected to the direct-current public power grid, a second input end of the grid-connected control device is connected to the output end of the second voltage conversion unit, and a third input end of the grid-connected control device is connected to the output end of the second power supply equipment; output voltage V of the second voltage conversion unit2：V2＝Vref-KpIs; wherein Vref is a reference voltage of the second voltage converting unit, KpIs a preset multiple, and Is the output current of the second power supply equipment; the grid-connected control method comprises the following steps: detecting a voltage of the direct current utility grid and an output voltage V of the second voltage converting unit before incorporating the second power supply device into the direct current utility grid2(ii) a At the output voltage V of the second voltage conversion unit2When the voltage is not equal to the voltage of the direct current public power grid, the reference voltage V of the second voltage conversion unit is adjustedrefThe adjusted output voltage V of the second voltage conversion unit2Equal to the voltage of the dc utility grid; at the output voltage V of the second voltage conversion unit2And when the voltage is equal to the voltage of the direct current public power grid, the second power supply equipment is merged into the direct current public power grid.
The embodiment of the invention also provides a grid-connected control device, which is arranged in an electric power system, wherein the electric power system comprises first power supply equipment which is already merged into the direct-current public power grid and second power supply equipment which needs to be merged into the direct-current public power grid, the first power supply equipment is connected to the direct-current public power grid through a first voltage conversion unit, the second power supply equipment is connected to the input end of a second voltage conversion unit, the output end of the second voltage conversion unit is used for connecting the direct-current public power grid, the output end of the grid-connected control device is connected to the control end of the second voltage conversion unit, the first input end of the grid-connected control device is connected to the direct-current public power grid, the second input end of the grid-connected control device is connected to the output end of the second voltage conversion unit, and the third input end of the grid-connected control device is connected to the output end of the second power supply equipment; output voltage V2 of the second voltage conversion unit: V2-Vref-KpIs; wherein Vref is a reference voltage of the second voltage converting unit, KpIs a preset multiple, and Is the output current of the second power supply equipment;the grid-connected control device includes: the device comprises a detection unit, a calculation unit and an adjustment unit; the first input end of the detection unit is used as the first input end of the grid-connected control device, the second input end of the detection unit is used as the second input end of the grid-connected control device, the first output end of the detection unit is connected to the first input end of the calculation unit, the second output end of the detection unit is respectively connected to the second input end of the calculation unit and the first input end of the adjustment unit, the third input end of the calculation unit is used as the third input end of the grid-connected control device, the output end of the calculation unit is connected to the second input end of the adjustment unit, and the output end of the adjustment unit is used as the output end of the grid-connected control device; the detection unit is used for detecting the voltage of the direct current public power grid and the output voltage V of the second voltage conversion unit before the second power supply equipment is merged into the direct current public power grid2And the voltage of the DC public power grid is output from the first output end of the detection unit, and the output voltage V of the second voltage conversion unit2Output from the second output terminal of the detection unit; the computing unit is used for converting the output voltage V of the second voltage conversion unit according to the voltage of the direct current public power grid2And calculating to obtain a target voltage V which needs to be output by the second voltage conversion unit: v ═ Vref' -KpIs; wherein Vref' is a target reference voltage, which is equal to the voltage of the dc utility grid before the second power supply device is incorporated into the dc utility grid; the adjusting unit is used for acquiring the output voltage V of the second voltage conversion unit in real time2The second voltage conversion unit is used as a feedback voltage and is adjusted, and the difference value between the adjusted target voltage and the feedback voltage is 0; and when the difference value between the target voltage and the feedback voltage is 0, the second power supply device is merged into the direct current public power grid.
Compared with the related art, the second power supply device which needs to be incorporated into the dc public power grid is connected to the input end of the second voltage conversion unit, the second voltage conversion unit converts the electric energy output by the second power supply device into the required dc voltage for output, and the output voltage V2 of the second voltage conversion unit: V2-Vref-Kp 2 Is 2; the Vref Is a reference voltage of the second voltage conversion unit, Kp2 Is a preset multiple, Is2 Is an output current of the second power supply device, it can be seen that the second voltage conversion unit has a droop characteristic curve, the grid-connected control device can detect the output voltage of the second voltage conversion unit and the voltage of the dc public power grid, and when the output voltage of the second voltage conversion unit Is not equal to the voltage of the dc public power grid, the Vref in the droop characteristic curve of the second voltage conversion unit Is dynamically adjusted, so that the output voltage V2 of the second voltage conversion unit Is equal to the voltage of the dc public power grid, and then the second power supply device Is incorporated into the dc public power grid. This application when detecting that the output voltage of second voltage conversion unit is not equal to the voltage of direct current public power grid, can adjust the output voltage of second voltage conversion unit through the power droop curve of dynamic adjustment second voltage conversion unit, and after the output voltage of second voltage conversion unit equals with the voltage of direct current public power grid, incorporate into direct current public power grid with second power supply unit, can effectively reduce the surge current that the operation of being incorporated into the power networks made direct current public power grid produce, and then guarantee boats and ships power supply system's reliable operation.
In addition, after the second power supply device is incorporated into the dc public power grid, the method further includes: converting the output voltage V of the second voltage conversion unit2Increasing to a preset threshold; wherein the output power of the first voltage conversion unit decreases with an increase in the output voltage of the first voltage conversion unit. In this embodiment, the larger the preset threshold is, the larger the output power of the second power supply device corresponding to the second voltage conversion unit is, the smaller the output power of the first power supply device corresponding to the first voltage conversion unit is, and therefore, the size of the preset threshold may be adjusted to flexibly allocate the power output by each of the plurality of power supply devices incorporated into the dc public power grid.
In addition, the reference voltage V of the second voltage conversion unit is adjustedrefThe adjusted output voltage V of the second voltage conversion unit2Equal to the voltage of a direct current utility grid, comprising: and calculating a target voltage V needed to be output by the second voltage conversion unit through the following formula: v ═ Vref' -KpIs; wherein Vref 'is a target reference voltage, and the target reference voltage Vref' is obtained by integrating the second power supply device into the DC busBefore the power grid, the voltage is equal to the voltage of the direct current public power grid; obtaining the output voltage V of the second voltage conversion unit in real time2As a feedback voltage; and adjusting the second voltage conversion unit according to the difference value between the feedback voltage and the target voltage, wherein the difference value between the adjusted feedback voltage and the target voltage is 0. In this embodiment, a specific implementation manner for adjusting the output voltage of the second voltage conversion unit is provided.
In addition, the second power supply device is a direct current power supply, and the second voltage conversion unit is a DCDC unit. In this embodiment, the second power supply device may be a direct current power supply, such as a storage battery, and the second voltage conversion unit is a DCDC unit, which may convert a direct current voltage into a direct current voltage with a different voltage.
In addition, the second power supply device is an alternating current power supply, and the second voltage conversion unit is an ACDC unit. In this embodiment, the second power supply device may be an ac power supply, such as a generator, and the second voltage conversion unit may be an ACDC unit, which may convert an ac voltage into a dc voltage.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
FIG. 1 is a block schematic diagram of a power system in accordance with one embodiment;
fig. 2 is a schematic view of droop characteristics of a voltage conversion unit according to a grid-connection control method in one embodiment;
FIG. 3 is a first flowchart of a grid tie control method according to one embodiment;
FIG. 4 is a flow chart two of a grid tie control method according to one embodiment;
FIG. 5 is a flow chart diagram three of a grid tie control method according to one embodiment;
FIG. 6 is a first hardware circuit diagram of a grid tie control apparatus according to one embodiment;
FIG. 7 is a hardware circuit diagram two of a grid tie control apparatus according to one embodiment;
fig. 8 is a hardware circuit diagram three of the grid-connection control apparatus according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that in various embodiments of the invention, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not constitute any limitation to the specific implementation manner of the present invention, and the embodiments may be mutually incorporated and referred to without contradiction.
The embodiment of the invention relates to a grid-connected control method, which is applied to a grid-connected control device in an electric power system and is used for adjusting the output voltage of a second voltage conversion unit when second power supply equipment needs to be merged into a direct-current public power grid according to different power requirements of a load side, and carrying out grid-connected operation after the output voltage is consistent with the voltage of the direct-current public power grid, so that surge current generated in the direct-current public power grid due to the grid-connected operation is reduced as much as possible, and the reliable operation of a ship power supply system can be effectively ensured.
Referring to fig. 1, the power system includes a first power supply device 2 already incorporated in a dc public power grid 1 and a second power supply device 3 to be incorporated in the dc public power grid 1, the first power supply device 2 is connected to the dc public power grid 1 through a first voltage conversion unit 4, the second power supply device 3 is connected to an input terminal 501 of a second voltage conversion unit 5, an output terminal 502 of the second voltage conversion unit 5 is used for connecting the dc public power grid 1, the output terminal 502 of the second voltage conversion unit 5 can be connected to the dc public power grid 1 through a switch unit 6, the switch unit 6 is, for example, a relay, when the second power supply device 3 is not incorporated in the dc public power grid 1, the switch unit 6 is in an off state, and a grid connection control device 7 can control the second power supply device 3 to be incorporated in the dc public power grid 1 by controlling the switch unit 6 to be in an on state.
An output terminal 701 of the grid-connected control device 7 is connected to a control terminal 503 of the second voltage conversion unit 5, a first input terminal 702 of the grid-connected control device 7 is connected to the dc public power grid 1, a second input terminal 703 of the grid-connected control device 7 is connected to the output terminal 502 of the second voltage conversion unit 5, and a third input terminal 704 of the grid-connected control device 7 is connected to the output terminal 301 of the second power supply apparatus 3.
Referring to curve 2 in fig. 2, the output voltage V2 of the second voltage converting unit 5 has a droop characteristic: V2-Vref-KpIs; wherein Vref is a reference voltage of the second voltage converting unit, KpIs the output current of the second power supply device and Is a preset multiple.
A specific flow of the grid-connection control method according to the present embodiment is shown in fig. 3.
And 104, merging the second power supply equipment into the direct current public power grid.
In this embodiment, a second power device that needs to be incorporated into the dc public power grid is connected to an input end of a second voltage conversion unit, the second voltage conversion unit converts electric energy output by the second power device into a required dc voltage for output, and an output voltage V2 of the second voltage conversion unit: V2-Vref-K p2 Is 2; wherein Vref is a reference voltage of the second voltage converting unit, K p2 is a predetermined multiple, Is2Is the output current of the second power supply deviceWhen the second voltage conversion unit has a droop characteristic curve, the grid-connected control device detects the output voltage of the second voltage conversion unit and the voltage of the direct-current public power grid, and dynamically adjusts V in the droop characteristic curve of the second voltage conversion unit when the output voltage of the second voltage conversion unit is not equal to the voltage of the direct-current public power gridrefMake the output voltage V of the second voltage conversion unit2And after the voltage is equal to the voltage of the direct current public power grid, the second power supply equipment is merged into the direct current public power grid. This application when detecting that the output voltage of second voltage conversion unit is not equal to the voltage of direct current public power grid, can adjust the output voltage of second voltage conversion unit through the power droop curve of dynamic adjustment second voltage conversion unit, and after the output voltage of second voltage conversion unit equals with the voltage of direct current public power grid, incorporate into direct current public power grid with second power supply unit, can effectively reduce the surge current that the operation of being incorporated into the power networks made direct current public power grid produce, and then guarantee boats and ships power supply system's reliable operation.
In particular, KpThe current Is a collected output current of the second power supply device, in an embodiment, the second power supply device 3 may be a direct current power supply or an alternating current power supply, when the second power supply device 3 Is a direct current power supply, for example, when the second power supply device Is a storage battery, the second voltage conversion unit 5 Is a DCDC unit, and the DCDC unit may convert a direct current voltage obtained from the second power supply device 3 into a direct current voltage to be output and output the direct current voltage; when the second power supply device 3 is an ac power supply, for example, a generator, the second voltage conversion unit 5 is an ACDC unit, and the ACDC unit may convert an ac voltage obtained from the second power supply device 3 into a dc voltage to be output and output the dc voltage. In one embodiment, the first power supply device 2 may also be a direct current power supply or an alternating current power supply, and the corresponding first voltage conversion unit 4 is also a DCDC unit or an ACDC unit. If the second power supply device 3 is a DC power supply, IsIs the output current of the second power supply device 3; if the second power supply device 3 is an ac power supply, it is necessary to collect a phase angle of a current output from the second power supply device, and the collected three-phase ac current is fed according to the phase anglePerforming three-phase-two-phase conversion to obtain Id and IqTwo-phase current, where Id is the reactive component, IqIs the active component, Is ═ I in this caseq。
In one embodiment, a specific implementation of adjusting the output voltage of the second voltage converting unit is provided. Step 201, step 202 and step 204 are substantially the same as step 101, step 102 and step 104, and are not described herein again, except that step 203 includes sub-steps 2031 to 2033.
Fig. 4 shows a specific flow of the grid-connection control method according to the present embodiment.
In particular, V in the formularefBefore the second power supply device is incorporated into the dc utility grid for the target reference voltage, in particular when the output voltage of the second voltage converting unit is not equal to the voltage of the dc utility grid, Vref' is equal to the voltage of the dc utility grid.
In sub-step 2032, the output voltage of the second voltage conversion unit is obtained in real time as the feedback voltage.
Sub-step 2033, adjusting the second voltage conversion unit according to the difference between the feedback voltage and the target voltage, where the difference between the adjusted feedback voltage and the target voltage is 0.
Specifically, when the output voltage of the second voltage conversion unit is not equal to the voltage of the dc public power grid, since the second power supply device is not yet incorporated into the dc public power grid to supply power to the load at this time, the output power of the second voltage conversion unit is 0, and I at this timesOne is set to 0, so that the voltage of the DC public power grid is taken as V at the momentrefGiven value of (a), V ═ VrefThat is, the calculated target voltage of the second voltage converting unit is equal to the voltage of the dc public power grid, and finally the feedback voltage of the second voltage converting unit needs to be adjusted to make the difference between the target voltage and the feedback voltage of the second voltage converting unit be 0, that is, the output voltage of the second voltage converting unit is adjusted to be equal to the voltage of the dc public power grid, specifically, by adjustingV in output voltage formula of second voltage conversion unitrefTo adjust the magnitude of the output voltage of the second voltage conversion unit. And the grid-connected control device specifically adjusts the difference value between the feedback voltage and the target voltage to be 0 through the combined action of the voltage feedback outer ring and the current feedback inner ring.
Referring to curve 1 in fig. 2, curve 1 shows a droop characteristic curve of the first voltage converting unit, it can be seen that the output power of the first voltage converting unit decreases with the increase of the output voltage of the first voltage converting unit, and curve 2 in fig. 2 shows a droop characteristic curve of the second voltage converting unit when the second power supply device is not incorporated into the dc public power grid, it can be seen that the output power of the second voltage converting unit decreases with the increase of the output voltage of the second voltage converting unit.
Since the first power supply device is already incorporated into the dc public power grid and can provide power to the load side, the first voltage converting unit adjusts the output power of the first voltage converting unit according to the power required by the load side, for example, the output power of the first voltage converting unit is P0, at this time, the first voltage converting unit operates at point W0, it can be seen from curve 1 that the output voltage of the first voltage converting unit is U0, and assuming that only the first power supply device is incorporated into the dc public power grid, the voltage of the dc public power grid is equal to the output voltage U0 of the first voltage converting unit at this time, that is, the voltage of the dc public power grid is U0 at this time.
Since the second power supply device is not yet incorporated into the dc public power grid, the second power supply device cannot provide power to the load side, the output power of the second voltage conversion unit is equal to 0, and as can be seen from curve 2, the second voltage conversion unit operates at point W1, and the output voltage V of the second voltage conversion unit2If the second power supply device is subjected to grid-connection operation, because the output voltage of the second voltage conversion unit is different from the voltage of the dc public power grid, a large surge current may be generated in the dc public power grid, which may cause grid-connection failure of the second power supply device, and even damage to the dc public power gridThe device of (1).
The output voltage V of the second voltage conversion unit is adjusted by dynamically adjusting the power droop curve of the second voltage conversion unit through the grid-connected control device2The output voltage of the second voltage conversion unit is equal to the voltage U0 of the dc public power grid, since the formula V2 is not changed in the process, i.e. Vref-KpK in ISpAnd Is, by changing Vref only and changing Vref to Vref' to U0, V2 to U0-KpIs, see curve 3 specifically, curve 3 Is only to shift curve 2 down in parallel, so that the first voltage conversion unit works at point W2, at this time, the output voltage of the first voltage conversion unit Is U0, which Is equal to the voltage U0 of the dc public power grid, on this basis, the second power supply device Is incorporated into the dc public power grid, and because there Is no difference between the output voltage of the second voltage conversion unit and the voltage of the dc public power grid any more, which Is equal to U0, the surge current generated in the dc public power grid can be effectively reduced, so that the grid connection success rate of the second power supply device Is improved, and the reliable operation of the ship power supply system can be ensured.
In this embodiment, a second power device that needs to be incorporated into the dc public power grid is connected to an input end of the second voltage conversion unit, the second voltage conversion unit converts electric energy output by the second power device into a required dc voltage for output, the grid-connected control device detects an output voltage of the second voltage conversion unit and a voltage of the dc public power grid, and when the output voltage of the second voltage conversion unit is not equal to the voltage of the dc public power grid, dynamically adjusts a power droop curve of the second voltage conversion unit according to a calculated target voltage and a feedback voltage obtained through real-time detection, and finally, after a difference between the target voltage and the feedback voltage is equal to 0, that is, after the output voltage of the second voltage conversion unit is equal to the voltage of the dc public power grid, the second power device is incorporated into the dc public power grid. This application is when detecting the output voltage of second voltage conversion unit not be equal to the voltage of direct current public power grid, can adjust the output voltage of second voltage conversion unit through the power droop curve of dynamic adjustment second voltage conversion unit, and after the output voltage of second voltage conversion unit equals with the voltage of direct current public power grid, merge the second power supply unit into direct current public power grid, because there is no longer the difference between the output voltage of second voltage conversion unit and the voltage of direct current public power grid, so can effectively reduce the surge current that produces in the direct current public power grid, in order to improve second power supply unit and to be incorporated into the power networks the success rate, and then can guarantee the reliable operation of boats and ships power supply system.
Another embodiment of the invention relates to a grid-tie control method. Step 301, step 302, step 303, and step 304 are substantially the same as step 101, step 102, step 103, and step 104, and are not described herein again, except that this embodiment further includes step 305.
Fig. 5 shows a specific flow of the grid-connection control method according to the present embodiment.
In step 305, the output voltage of the second voltage conversion unit is increased to a preset threshold.
Specifically, when the second power supply device is just incorporated into the dc public power grid, the second voltage conversion unit operates at a peak voltage point (corresponding to an output power of 0) of the power droop curve, and at this time, the grid-connected control device adjusts the power droop curve of the second voltage conversion unit according to the target threshold.
In the process that the output voltage of the second voltage conversion unit is increased to the target threshold value, the output voltage is higher than that of the first voltage conversion unit, so that the load is automatically transferred to the second voltage conversion unit. In the process of load transfer, the output power of the first voltage conversion unit is gradually reduced, and the output voltage of the first voltage conversion unit is gradually increased according to the power droop curve of the first voltage conversion unit; the output power of the second voltage converting unit gradually increases, and the output voltage gradually decreases according to the power droop curve of the second voltage converting unit. Finally, the output voltages of the two voltage converting units are pulled to be consistent, the power droop curve Vref of the second voltage converting unit is equal to the target threshold, and V2 is equal to the preset threshold.
Referring to fig. 2, after the curve 2 is shifted down to the curve 3 in parallel, the second power supply device is operated in parallel, and when the second power supply device is initially incorporated into the dc public power grid, the second power supply device is operated at W2It can be seen that the second power supply device is not outputting power to the load side at this time, and the present application adjusts the formula V2 to Vref-KpVref in Is to adjust the output voltage V of the second voltage conversion unit2In particular by adjusting VrefTo increase the output voltage of the second voltage converting unit, when the output power of the second voltage converting unit is equal to 0, the output voltage of the second voltage converting unit is equal to the target threshold, which is exemplified by U1 in fig. 2, then the adjusted droop characteristic curve of the second voltage converting unit returns to curve 2, if the grid-connected control device synchronously controls the output voltages of the first voltage converting unit and the second voltage converting unit to increase to the target threshold U1, the voltage of the dc utility grid may reach the preset threshold U1, but since the grid-connected control device does not synchronously control the output voltage of the second voltage converting unit and the output voltage of the first voltage converting unit to increase to the target threshold U1, the increased voltage of the dc utility grid may not reach the target threshold U1, and if the increased voltage reaches the preset threshold U2 smaller than the target threshold U1, then the output voltages of the first voltage converting unit and the second voltage converting unit are equal and equal to the preset threshold U2, and it can be seen from the graph in fig. 2 that, at this time, the first voltage converting unit operates at the operating point W3, the output power of the first voltage converting unit is equal to P1, the second voltage converting unit operates at the operating point W4, the output power of the second voltage converting unit is equal to P2, and the sum of P1 and P2 is equal to P0. It can be seen that although the power output by the dc utility grid to the load side is still P0, the load side is not only powered by the first power supply device, but also by the second power supply device.
Further, the value of the preset threshold may be adjusted by a ship energy management system (PMS) according to the power required by the load side, specifically, by adjusting the target threshold, so as to distribute the power provided by the first power source device and the power provided by the second power source device to the load side, where the larger the preset threshold is, the smaller the power provided by the first power source device is, and the larger the power provided by the second power source device is; the smaller the preset threshold, the more power is provided by the first power supply device and the less power is provided by the second power supply device.
In this embodiment, flexible power distribution among a plurality of power supply devices incorporated into the dc public power grid can be achieved by adjusting the size of the preset threshold.
The steps of the above methods are divided for clarity, and the implementation may be combined into one step or split some steps, and the steps are divided into multiple steps, so long as the same logical relationship is included, which are all within the protection scope of the present patent; it is within the scope of the patent to add insignificant modifications to the algorithms or processes or to introduce insignificant design changes to the core design without changing the algorithms or processes.
One embodiment of the present invention relates to a grid-connected control device, referring to fig. 1, a grid-connected control device 7 is disposed in an electric power system, the electric power system includes a first power supply device 2 already incorporated into a dc public power grid 1 and a second power supply device 3 to be incorporated into the dc public power grid 1, the first power supply device 2 is connected to the dc public power grid 1 through a first voltage conversion unit 4, the second power supply device 3 is connected to an input terminal 501 of a second voltage conversion unit 5, an output terminal 502 of the second voltage conversion unit 5 is used for connecting to the dc public power grid 1, an output terminal 701 of the grid-connected control device 7 is connected to a control terminal 503 of the second voltage conversion unit 5, a first input terminal 702 of the grid-connected control device 7 is connected to the dc public power grid 1, a second input terminal 703 of the grid-connected control device 7 is connected to the output terminal 502 of the second voltage conversion unit 5, a third input terminal 704 of the grid-connected control device 7 is connected to the output terminal 301 of the second power supply device 3, output voltage V2 of the second voltage conversion unit 5: V2-Vref-KpIs; wherein Vref is a reference voltage of the second voltage converting unit, KpIs the output current of the second power supply device and Is a preset multiple.
Referring to fig. 6, the first power supply device, the first voltage conversion unit, and the switching unit are not shown in fig. 6, and the grid-connection control apparatus 7 includes: a detection unit 71, a calculation unit 72 and an adjustment unit 73.
A first input 711 of the detecting unit 71 serves as a first input 702 of the grid-connected control device 1, a second input 712 of the detecting unit 71 serves as a second input 703 of the grid-connected control device 7, a first output 713 of the detecting unit 71 is connected to a first input 721 of the calculating unit 72, a second output 714 of the detecting unit 71 is respectively connected to a second input 722 of the calculating unit 72 and a first input 731 of the adjusting unit 73, a third input 723 of the calculating unit 72 serves as a third input 704 of the grid-connected control device 7, an output 724 of the calculating unit 72 is connected to a second input 732 of the adjusting unit 73, and an output 733 of the adjusting unit 73 serves as an output 701 of the grid-connected control device 7.
The detection unit 71 will detect the voltage of the dc public power network 1 and the output voltage V of the second voltage conversion unit 5 before the second power supply device 3 is incorporated into the dc public power network 12And outputs the voltage of the dc utility grid 1 from the first output end 713 of the detection unit 71 and the output voltage V of the second voltage conversion unit 52From the second output 714 of the detection unit 71, the calculation unit 72 will calculate the voltage V of the dc public power network 1 and the output voltage V of the second voltage conversion unit 52And calculating to obtain a target voltage V that the second voltage conversion unit 5 needs to output: v ═ Vref' -KpIs, wherein Vref' Is the target reference voltage, the target reference voltage Vref' before the second power supply device 3 is incorporated into the dc public power network 1, equal to the voltage of the dc public power network 1, the adjusting unit 73 obtains the output voltage V of the second voltage converting unit 5 in real time2As a feedback voltage, the second voltage conversion unit 5 is adjusted, and the difference between the adjusted target voltage and the feedback voltage is 0; and when the difference value between the target voltage and the feedback voltage is 0, the second power supply device is merged into the direct current public power grid.
In an embodiment, referring to fig. 6, the second voltage conversion unit 5 includes a conversion circuit, the conversion circuit includes six power electronic switching tubes, the power electronic switching tubes are, for example, IGBT tubes or MOS tubes, each two power electronic switching tubes are connected in series to form a branch, and three branches are formed by the three branches, the conversion circuit is a circuit formed by connecting the three branches in parallel, a connection point between two power electronic switching tubes on each branch is connected to an anode of the second power supply device 3, specifically, a current output from the second power supply device 3 is divided into three parts and is respectively transmitted to connection points between two MOS tubes on the three branches, any one of two parallel points of the three branches is connected to a cathode of the second power supply device 3, and the two parallel points of the three branches are further connected to two ends of the dc public power grid 1. Further, the conversion circuit further comprises a suppression circuit, the suppression circuit comprises a first resistor R1, a second resistor R2, a first capacitor C1 and a second capacitor C2, the first resistor R1 and the second resistor R2 are connected in series to form a first branch, the first capacitor C1 and the second capacitor C2 are connected in series to form a second branch, a first end of the first branch is connected to a first end of the second branch, a second end of the first branch is connected to a second end of the second branch, and a connection point between the first resistor R1 and the second resistor R2 is connected to a connection point between the first capacitor C1 and the second capacitor C2.
In this embodiment, when detecting that the output voltage of the second voltage conversion unit is not equal to the voltage of the dc public power grid, the grid-connected control device may incorporate the second power supply device into the dc public power grid after adjusting that the output voltage of the second voltage conversion unit is equal to the voltage of the dc public power grid, which may effectively reduce the surge current generated by the dc public power grid due to the grid-connected operation, and further ensure the reliable operation of the ship power supply system.
In one embodiment, referring to FIG. 7, the calculation unit 72 includes a comparator 72-1, a detection module 72-2, a proportional amplifier 72-3, and a first adder 72-4.
The first input terminal 72-11 of the comparator 72-1 serves as the first input terminal 721 of the calculating unit 72, the second input terminal 72-12 of the comparator 72-1 serves as the second input terminal 722 of the calculating unit 72, the output terminal 72-13 of the comparator 72-1 is connected to the non-inverting input terminal 72-41 of the first adder 72-4, the input terminal 72-21 of the detecting module 72-2 serves as the third input terminal 723 of the calculating unit 72, the output terminal 72-22 of the detecting module 72-2 is connected to the input terminal 72-31 of the proportional amplifier 72-3, the output terminal 72-32 of the proportional amplifier 72-3 is connected to the inverting input terminal 72-42 of the first adder 72-4, and the output terminal 72-43 of the first adder 72-4 serves as the output terminal 724 of the calculating unit 72.
The comparator 72-1 outputs the voltage of the dc public power grid 1 when the voltage of the dc public power grid 1 is not equal to the output voltage of the second voltage converting unit 5; when the voltage of the direct current utility grid 1 is equal to the output voltage of the second voltage converting unit 5, the output voltage of the second voltage converting unit 5 is output. Specifically, the voltage of the dc public power grid 1 or the output voltage of the second voltage conversion unit 5 may be selectively output by controlling a virtual switch. The detection module 72-2 outputs the detected output current of the second power supply device 3, the proportional amplifier 72-3 amplifies the obtained output current of the second power supply device 3 by a preset multiple and outputs the amplified output current, and a technician can adjust the preset multiple by the proportional amplifier to obtain the required droop characteristic of the second voltage conversion unit. The first adder 72-3 subtracts the data input from the non-inverting input terminal 72-31 from the data input from the inverting input terminal 72-32, and outputs the target voltage.
In one embodiment, when the second power device 3 is a dc power source, the second voltage conversion unit 5 is a DCDC unit, and the detection module 72-2 obtains the dc current output by the second power device 3 as the output current of the second power device 3.
In the above case, the adjusting unit 73 includes: a second adder 73-1, a first proportional-integral regulator 73-2, a third adder 73-3, a second proportional-integral regulator 73-4, and a PWM control module 73-5.
The inverting input terminal 73-12 of the second adder 73-1 serves as the first input terminal 731 of the adjustment unit 73, the non-inverting input terminal 73-11 of the second adder 73-1 serves as the second input terminal 732 of the adjustment unit 73, the output terminal 73-13 of the second adder 73-1 is connected to the input terminal 73-21 of the first proportional integral regulator 73-2, the output terminal 73-22 of the first proportional integral regulator 73-2 is connected to the non-inverting input terminal 73-31 of the third adder 73-3, the output terminal 72-22 of the detection module 72-2 is connected to the inverting input terminal 73-32 of the third adder 73-3, the output terminal 73-33 of the third adder 73-3 is connected to the input terminal 73-41 of the second proportional integral regulator 73-4, and the output terminal 73-42 of the second proportional integral regulator 73-4 is connected to the PWM control module 73-5 and the output 73-52 of the PWM control module 73-5 as the output 733 of the adjustment unit 73.
The second adder 73-1 outputs first data obtained by subtracting the data input from the non-inverting input terminal 73-11 of the second adder 73-1 from the data input from the inverting input terminal 73-12 of the second adder 73-1 to the first proportional integral regulator 73-2, the first proportional integral regulator 73-2 outputs data capable of adjusting the first data up to 0, the third adder 73-3 outputs second data obtained by subtracting the data input from the inverting input terminal 73-32 of the third adder 73-3 from the data input from the non-inverting input terminal 73-31 of the third adder 73-3 to the second proportional integral regulator 73-4, the second proportional integral regulator 73-4 outputs data capable of adjusting the second data up to 0, the PWM control module 73-5 outputs data according to the second proportional integral regulator 73-4, the control voltage is output to the second voltage conversion unit 5.
In this embodiment, a specific hardware implementation form of the grid-connected control device when the second power supply device is a dc power supply is provided.
In one embodiment, when the second power supply device 3 is an ac power supply, the second voltage conversion unit 5 is an ACDC unit.
In the above case, referring to fig. 8, the detection module 72-2 includes a first module and a second module (not shown).
The input of the first module serves as the input 72-21 of the detection module 72-2, the output of the first module is connected to the input of the second module, and the output of the second module serves as the output 72-22 of the detection module 72-2.
The first module can obtain the three-phase alternating current output by the second power supply device 3 in real time and obtain the phase angle of the three-phase alternating current, and the second module can convert the three-phase alternating current into active current and reactive current according to the phase angle and take the active current as the output current of the second power supply device 3.
In one embodiment, referring to fig. 8, the adjusting unit 73 includes: a second adder 73-1, a third adder 73-3, a fourth adder 73-6, a first proportional integral regulator 73-2, a second proportional integral regulator 73-4, a third proportional integral regulator 73-7 and a PWM control module 73-5;
the inverting input terminal 73-12 of the second adder 73-1 serves as the first input terminal 731 of the adjustment unit 73, the non-inverting input terminal 73-11 of the second adder 73-1 serves as the second input terminal 732 of the adjustment unit 73, the output terminal 73-13 of the second adder 73-1 is connected to the input terminal 73-21 of the first proportional integral regulator 73-2, the output terminal 73-22 of the first proportional integral regulator 73-2 is connected to the non-inverting input terminal 73-31 of the third adder 73-3, the output terminal 72-22 of the detection module 72-2 is connected to the inverting input terminal 73-32 of the third adder 73-3, the output terminal 73-33 of the third adder 73-3 is connected to the input terminal 73-41 of the second proportional integral regulator 73-4, and the output terminal 73-42 of the second proportional integral regulator 73-4 is connected to the PWM control module 73-5, a first input 73-51; the output 72-22 of the detection module 72-2 is connected to the inverting input 73-62 of the fourth adder 73-6, the non-inverting input 73-61 of the fourth adder 73-6 is connected to ground, the output 73-62 of the fourth adder 73-6 is connected to the input 73-71 of the third proportional integrator 73-7, the output 73-72 of the third proportional adjusting integrator 73-7 is connected to the second input 73-53 of the PWM control module 73-5, and the output 73-52 of the PWM control module 73-5 serves as the output 733 of the adjustment unit 73.
The second adder 73-1 outputs first data obtained by subtracting the data input from the non-inverting input terminal 73-11 of the second adder 73-1 from the data input from the inverting input terminal 73-12 of the second adder 73-1 to the first proportional integral regulator 73-2, the first proportional integral regulator 73-2 outputs data capable of adjusting the first data to 0, the third adder 73-3 outputs second data obtained by subtracting the data input from the inverting input terminal 73-32 of the third adder 73-3 from the data input from the non-inverting input terminal 73-31 of the third adder 73-3 to the second proportional integral regulator 73-4, the second proportional integral regulator 73-4 outputs data capable of adjusting the second data to 0, and the fourth adder 73-6 is used for adding the data input from the non-inverting input terminal 73-61 of the fourth adder 73-6 The third data obtained by subtracting the data inputted from the inverting input terminal 73-62 of the fourth adder 73-6 is outputted to the third proportional-integral regulator 73-7, the third proportional-integral regulator 73-7 outputs data capable of adjusting the third data to 0, and the PWM control module 73-5 outputs the control voltage to the second voltage converting unit 5 according to the data outputted from the second proportional-integral regulator 73-4 and the third proportional-integral regulator 73-7.
In this embodiment, a specific hardware implementation form of the grid-connected control device when the second power supply device is an ac power supply is provided.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.
Claims (10)
1. A grid-connected control method is characterized in that the grid-connected control method is applied to a grid-connected control device in an electric power system, the power system comprises a first power supply device already incorporated in a direct current utility grid and a second power supply device required to be incorporated in the direct current utility grid, the first power supply device is connected to the direct current public power grid through a first voltage conversion unit, the second power supply device is connected to the input end of the second voltage conversion unit, the output end of the second voltage conversion unit is used for connecting the direct current public power grid, the output end of the grid-connected control device is connected with the control end of the second voltage conversion unit, a first input end of the grid-connected control device is connected to the direct-current public power grid, a second input end of the grid-connected control device is connected to an output end of the second voltage conversion unit, a third input end of the grid-connected control device is connected to an output end of the second power supply equipment; an output voltage V of the second voltage conversion unit2：V2＝Vref-Kp*Is(ii) a Wherein, VrefIs a reference voltage of the second voltage conversion unit, KpTo a predetermined multiple, IsIs the output current of the second power supply device;
the method comprises the following steps:
detecting a voltage of the direct current utility grid and an output power of the second voltage conversion unit before incorporating the second power supply device into the direct current utility gridPressure V2；
At the output voltage V of the second voltage conversion unit2When the voltage of the direct current public power grid is not equal to the voltage of the direct current public power grid, the reference voltage V of the second voltage conversion unit is adjustedrefThe adjusted output voltage V of the second voltage conversion unit2Equal to the voltage of the dc utility grid;
at the output voltage V of the second voltage conversion unit2And when the voltage is equal to the voltage of the direct current public power grid, the second power supply device is incorporated into the direct current public power grid.
2. The grid-tie control method according to claim 1, wherein after the incorporating the second power supply apparatus into the direct-current utility grid, further comprising:
converting the output voltage V of the second voltage conversion unit2Increasing to a preset threshold;
wherein the output power of the first voltage conversion unit decreases as the output voltage of the first voltage conversion unit increases.
3. The grid-connection control method according to claim 1, wherein the adjusting of the reference voltage V of the second voltage conversion unitrefThe adjusted output voltage V of the second voltage conversion unit2Equal to the voltage of the direct current utility grid, comprising:
calculating a target voltage V to be output by the second voltage conversion unit according to the following formula:
V*＝Vref’-Kp*Is；
wherein, Vref' is a target reference voltage, the target reference voltage Vref' prior to incorporating the second power supply device into the direct current utility grid, equaling a voltage of the direct current utility grid;
acquiring the output voltage V of the second voltage conversion unit in real time2As a feedback voltage;
and adjusting the second voltage conversion unit according to the difference value between the feedback voltage and the target voltage, wherein the difference value between the adjusted feedback voltage and the target voltage is 0.
4. The grid-connection control method according to any one of claims 1 to 3, wherein the second power supply device is a direct-current power supply, and the second voltage conversion unit is a DCDC unit.
5. The grid-connection control method according to any one of claims 1 to 3, wherein the second power supply device is an alternating current power supply, and the second voltage conversion unit is an ACDC unit.
6. A grid-connection control device provided in an electric power system, the power system comprises a first power supply device already incorporated in a direct current utility grid and a second power supply device required to be incorporated in the direct current utility grid, the first power supply device is connected to the direct current public power grid through a first voltage conversion unit, the second power supply device is connected to the input end of the second voltage conversion unit, the output end of the second voltage conversion unit is used for connecting the direct current public power grid, the output end of the grid-connected control device is connected with the control end of the second voltage conversion unit, a first input end of the grid-connected control device is connected to the direct-current public power grid, a second input end of the grid-connected control device is connected to an output end of the second voltage conversion unit, a third input end of the grid-connected control device is connected to an output end of the second power supply equipment; an output voltage V of the second voltage conversion unit2：V2＝Vref-Kp*Is(ii) a Wherein, VrefIs a reference voltage of the second voltage conversion unit, KpTo a predetermined multiple, IsIs the output current of the second power supply device;
the grid-connected control device includes: the device comprises a detection unit, a calculation unit and an adjustment unit;
a first input end of the detection unit is used as a first input end of the grid-connected control device, a second input end of the detection unit is used as a second input end of the grid-connected control device, a first output end of the detection unit is connected to a first input end of the calculation unit, a second output end of the detection unit is respectively connected to a second input end of the calculation unit and a first input end of the adjustment unit, a third input end of the calculation unit is used as a third input end of the grid-connected control device, an output end of the calculation unit is connected to a second input end of the adjustment unit, and an output end of the adjustment unit is used as an output end of the grid-connected control device;
the detection unit is used for detecting the voltage of the direct current public power grid and the output voltage V of the second voltage conversion unit before the second power supply equipment is merged into the direct current public power grid2And the voltage of the direct current public power grid is output from the first output end of the detection unit, and the output voltage V of the second voltage conversion unit is output2Output from a second output terminal of the detection unit;
the computing unit is used for converting the output voltage V of the second voltage conversion unit according to the voltage of the direct current public power grid2And calculating to obtain a target voltage V which needs to be output by the second voltage conversion unit: v ═ Vref’-Kp*Is；
Wherein, Vref' is a target reference voltage, the target reference voltage Vref' prior to incorporating the second power supply device into the direct current utility grid, equaling a voltage of the direct current utility grid;
the adjusting unit is used for acquiring the output voltage V of the second voltage conversion unit in real time2As a feedback voltage, adjusting the second voltage conversion unit, wherein the difference between the adjusted target voltage and the feedback voltage is 0; and when the difference value between the target voltage and the feedback voltage is 0, the second power supply device is incorporated into the direct-current public power grid.
7. The grid-connection control device according to claim 6, wherein the calculation unit includes a comparator, a detection module, a proportional amplifier, and a first adder.
A first input end of the comparator is used as a first input end of the computing unit, a second input end of the comparator is used as a second input end of the computing unit, an output end of the comparator is connected to a non-inverting input end of the first adder, an input end of the detection module is used as a third input end of the computing unit, an output end of the detection module is connected to an input end of the proportional amplifier, an output end of the proportional amplifier is connected to an inverting input end of the first adder, and an output end of the first adder is used as an output end of the computing unit;
the comparator is used for outputting the voltage of the direct current public power grid when the voltage of the direct current public power grid is not equal to the output voltage of the second voltage conversion unit; when the voltage of the direct current public power grid is equal to the output voltage of the second voltage conversion unit, outputting the output voltage of the second voltage conversion unit;
the detection module is used for outputting the detected output current of the second power supply equipment;
the proportional amplifier is used for amplifying the output current of the second power supply equipment by preset times and then outputting the amplified output current;
the first adder is configured to subtract the data input from the non-inverting input terminal from the data input from the inverting input terminal, and output the target voltage.
8. The grid-connection control device according to claim 7, wherein the second power supply apparatus is a direct current power supply, and the second voltage conversion unit is a DCDC unit; the detection module is used for acquiring direct current output by the second power supply equipment as output current of the second power supply equipment;
the adjusting unit includes: the second adder, the first proportional-integral regulator, the third adder, the second proportional-integral regulator and the PWM control module;
an inverting input end of the second adder serves as a first input end of the adjusting unit, a non-inverting input end of the second adder serves as a second input end of the adjusting unit, an output end of the second adder is connected to an input end of the first proportional-integral regulator, an output end of the first proportional-integral regulator is connected to a non-inverting input end of the third adder, an output end of the detection module is connected to an inverting input end of the third adder, an output end of the third adder is connected to an input end of the second proportional-integral regulator, an output end of the second proportional-integral regulator is connected to an input end of the PWM control module, and an output end of the PWM control module serves as an output end of the adjusting unit;
the second adder is used for outputting first data obtained by subtracting the data input from the inverting input end of the second adder from the data input from the non-inverting input end of the second adder;
the first proportional integral regulator is used for outputting data for regulating the first data to 0;
the third adder is used for outputting second data obtained by subtracting the data input from the inverting input end of the third adder from the data input from the non-inverting input end of the third adder;
the second proportional-integral regulator is used for outputting data for regulating the second data to 0;
and the PWM control module is used for outputting control voltage to the second voltage conversion unit according to the data output by the second proportional-integral regulator.
9. The grid-connection control device according to claim 7, wherein the second power supply apparatus is an alternating current power supply, and the second voltage conversion unit is an ACDC unit;
the detection module comprises a first module and a second module;
the input end of the first module is used as the input end of the detection module, the output end of the first module is connected to the input end of the second module, and the output end of the second module is used as the output end of the detection module;
the first module is used for acquiring a three-phase alternating current output by the second power supply equipment in real time and acquiring a phase angle of the three-phase alternating current;
the second module is used for converting the three-phase alternating current into active current and reactive current according to the phase angle, and the active current is used as output current of the second power supply device.
10. The grid-connection control device according to claim 9, wherein the adjusting unit includes: the device comprises a second adder, a third adder, a fourth adder, a first proportional-integral regulator, a second proportional-integral regulator, a third proportional-integral regulator and a PWM control module;
an inverting input end of the second adder serves as a first input end of the adjusting unit, a non-inverting input end of the second adder serves as a second input end of the adjusting unit, an output end of the second adder is connected to an input end of the first proportional-integral regulator, an output end of the first proportional-integral regulator is connected to a non-inverting input end of the third adder, an output end of the detection module is connected to an inverting input end of the third adder, an output end of the third adder is connected to an input end of the second proportional-integral regulator, and an output end of the second proportional-integral regulator is connected to a first input end of the PWM control module; the output end of the second module is connected to the inverting input end of the fourth adder, the non-inverting input end of the fourth adder is grounded, the output end of the fourth adder is connected to the input end of the third proportional integrator, the output end of the third proportional regulating integrator is connected to the second input end of the PWM control module, and the output end of the PWM control module is used as the output end of the adjusting unit;
the second adder is used for outputting first data obtained by subtracting the data input from the inverting input end of the second adder from the data input from the non-inverting input end of the second adder;
the first proportional integral regulator is used for outputting data for regulating the first data to 0;
the third adder is used for outputting second data obtained by subtracting the data input from the inverting input end of the third adder from the data input from the non-inverting input end of the third adder;
the second proportional-integral regulator is used for outputting data for regulating the second data to 0;
the fourth adder is configured to output third data obtained by subtracting the data input from the inverting input terminal of the fourth adder from the data input from the non-inverting input terminal of the fourth adder;
the third proportional-integral regulator is used for outputting data for regulating the third data to 0;
the PWM control module is used for outputting control voltage to the second voltage conversion unit according to the data output by the second proportional-integral regulator and the third proportional-integral regulator.
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Application publication date: 20210903 |