CN113972683B - Grid-connected mode switching control method of power electronic voltage conversion device - Google Patents
Grid-connected mode switching control method of power electronic voltage conversion device Download PDFInfo
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- CN113972683B CN113972683B CN202010711207.5A CN202010711207A CN113972683B CN 113972683 B CN113972683 B CN 113972683B CN 202010711207 A CN202010711207 A CN 202010711207A CN 113972683 B CN113972683 B CN 113972683B
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 32
- 230000001276 controlling effect Effects 0.000 claims description 9
- 230000001105 regulatory effect Effects 0.000 claims description 7
- 238000010586 diagram Methods 0.000 description 8
- 230000009466 transformation Effects 0.000 description 4
- 238000011160 research Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002457 bidirectional effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
Classifications
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
-
- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
-
- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
-
- 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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
Abstract
The invention discloses a control method for grid-connected mode switching of a power electronic voltage conversion device, which mainly comprises three steps, namely, the power electronic voltage conversion device is electrified to start, and a power converter valve is unlocked; secondly, controlling the grid-connected side voltage and the to-be-combined side voltage to be within an allowable deviation range, and operating a grid-connected circuit switch according to a set time sequence to realize grid connection of the conversion device; and thirdly, selecting a corresponding mode switching strategy by the conversion device according to the type of the grid-connected port, and adjusting the output of the conversion device to ensure that the conversion device stably transits to steady operation. The grid-connected circuit and the port grid-connected time sequence flow of the power electronic voltage conversion device ensure the smoothness and the non-disturbance of the whole starting grid-connected process, and the control method is simple and feasible, is convenient for automatic realization and improves the operation reliability of the whole process.
Description
Technical Field
The invention relates to the field of flexible power distribution networks, in particular to a grid-connected control method suitable for a power electronic voltage conversion device.
Background
Along with upgrading and transformation of a power distribution network and large-scale access of distributed new energy sources, research of a flexible power grid is paid attention to gradually, controllability of the power grid can be improved, tide is optimized and overall operation efficiency of a regional power grid is improved through mass use of power electronic equipment, meanwhile, an intelligent control unit installed on the power electronic equipment can be flexibly networked to realize upper-layer rapid coordination control, so that diversity of operation modes is improved, and rapid and flexible switching of the operation modes can be completed.
As core equipment of a flexible power distribution network, researches on body design and control methods of power electronic voltage conversion devices have been fully conducted. The power electronic voltage conversion device can be integrated into a traditional alternating current power grid, can also run off-grid, and establishes an off-grid micro-grid through photovoltaic, energy storage and other equipment. With gradual access of new energy, power electronics of a power distribution network is rapidly developed, and an off-grid power grid established by power electronic equipment or a traditional alternating current power grid accessed by a large number of power electronic equipment is generally small in short-circuit capacity, so that impact on a system when a load or new energy equipment is accessed to the power grid through a power electronic conversion circuit is required to be strictly controlled. The control system of the conversion device of the existing power electronic equipment is complex, and a unified and feasible starting grid-connected method is not formed for a starting time sequence part, so that a simple and effective rapid grid-connected control method needs to be researched, grid-connected operation of the power electronic equipment is rapidly realized under the condition that the system is stable, and meanwhile, bidirectional starting, forward grid-connected operation and reverse grid-connected operation of the equipment are required to be realized in special application occasions.
Disclosure of Invention
The invention aims to provide a unified and feasible grid-connected mode switching control method of power electronic voltage conversion devices, so that smooth starting and flexible grid connection of different power electronic conversion devices are realized, impact on a power distribution network caused by starting and grid connection of power electronic equipment is reduced, and stable operation of the power distribution network containing multiple power electronic equipment is improved.
In order to achieve the above effects, the present invention adopts the following technical scheme:
the grid-connected mode switching control method of the power electronic voltage transformation device comprises the steps that an output port of the power electronic voltage transformation device is connected in series with a set of grid-connected circuits, and the grid-connected circuits comprise grid-connected side power electronic voltage transformation device output end voltage transformers, grid-connected starting circuits and bus equipment to be combined;
the grid-connected starting circuit comprises a grid-connected switch, a grid-connected starting resistor and a starting resistor bypass switch, wherein one end of the grid-connected switch is used as an output end of the grid-connected starting circuit to be connected with an input end of the bus equipment to be combined, the other end of the grid-connected switch is connected with one end of the grid-connected starting resistor, the other end of the grid-connected starting resistor is used as an input end of the grid-connected starting circuit to be connected with an output end of the power electronic voltage conversion device through a voltage transformer at an output end of the grid-connected side conversion device, and the starting resistor bypass switch is connected with the grid-connected starting resistor in parallel;
the device for the bus to be combined comprises a bus to be combined side switch and a bus to be combined side voltage transformer, wherein one end of the bus to be combined side switch is used as an input end of the bus to be combined side device, the other end of the bus to be combined side switch is connected with a bus to be combined side, and the bus to be combined side voltage transformer is connected with the bus to be combined side;
the control method for grid-connected mode switching of the power electronic voltage conversion device comprises the following steps:
s1: when the bus side switch is switched on, the power supply side of the power electronic voltage conversion device is electrified;
s2: unlocking a power converter valve in the topology of the power electronic voltage conversion device;
s3: the voltage transformer on the side of the bus to be combined detects the voltage on the side of the bus to be combined, and the power electronic voltage conversion device on the side of the grid connection controls the voltage on the side of the grid connection within the allowable range of the voltage deviation between the voltage transformer on the side of the bus to be combined and the voltage transformer on the side of the bus to be combined;
s4: the grid-connected switch is switched on, and the grid-connected side and the to-be-combined side are electrically connected through a grid-connected starting resistor;
s5: starting a resistor bypass switch to switch on;
s6: after the power electronic voltage conversion device is electrically connected with the bus to be parallel through the grid-connected switch and the bypass switch, the power electronic voltage conversion device performs control mode switching, and the power electronic voltage conversion device comprises the following two conditions:
if the bus to be combined is a direct current bus, regulating a voltage reference value according to a set value of a voltage mode or switching a control mode into constant power operation according to a set rate;
if the bus to be combined is an alternating current bus, regulating a direct current side voltage reference value or an active power reference value according to a set value of an active regulation mode at a set rate; and according to the reactive power regulation mode set value, switching the control mode into a reactive power mode or regulating the alternating current side voltage reference value according to a set rate.
Further, the power electronic voltage conversion device comprises N ports, wherein N is more than or equal to 1; according to whether the output voltage of the port is alternating current or direct current, the port is divided into an alternating current port and a direct current port (the voltage and the power of each port are controllable (the power can flow bidirectionally)); the ports are divided into power ports and load ports according to the type of devices to which the ports are connected.
Further, in the step S3, if the bus to be combined is an ac bus, the amplitude and the frequency of the grid-connected side voltage are controlled within the deviation range with the grid to be combined; and if the bus to be parallel connected is a direct current bus, controlling the amplitude of the voltage at the grid-connected side within the deviation range with the power grid to be parallel connected.
Further, in the steps S3 to S5, if the bus to be connected is out of power, the grid-connected starting resistor is connected to the grid first, and then the starting resistor is switched on by a bypass switch to realize grid connection of the grid-connected side power electronic voltage conversion device; if the voltage deviation of the two sides (the grid-connected side and the to-be-combined side) of the grid-connected starting circuit is in the allowable range, the grid connection of the grid-connected side power electronic voltage conversion device is realized through directly switching on the grid-connected switch and the bypass switch.
Furthermore, in the grid connection process of the power electronic voltage conversion device, a certain port of the voltage conversion device is connected into one bus of an external power grid system through a set operation time sequence.
Further, in the step S4 and the step S5 of the grid-connected mode switching method, if one of the voltages collected by the voltage transformers at the two sides of the grid-connected switch is zero, grid connection is performed according to the ports of the direct-current voltage conversion device in the step S4 and the step S5; if the voltages acquired by the voltage transformers at the two sides of the grid-connected switch are within the S3 description deviation range, the bypass switch can be closed first, and then the grid-connected switch is closed, so that zero current impact grid connection of the power electronic voltage conversion device can be realized.
And S6, if the direct current port is connected, the initial control mode is to control the direct current port voltage, and after the connection is successful, the control mode is switched to a power mode or a voltage mode is maintained according to the control mode set by an operator, and the setting speed is set according to a reference value and is changed from adjustment before connection to the operator setting value.
Further, S6 step of the grid-connected mode switching method, if the AC side port is grid-connected, the initial control mode is to control the AC port voltage, and after the grid-connection is successful, the DC side voltage reference value or the active power reference value is gradually increased at a set rate according to the set value of the active regulation mode; switching to a reactive power mode or slowly adjusting an alternating-current side voltage reference value at a set rate according to a reactive power adjustment mode set value;
the beneficial effects are that: the invention provides a grid-connected mode switching method of a power electronic voltage conversion device, and provides a unified time sequence flow of grid connection of a direct current port and an alternating current port of the conversion device. The grid-connected process is divided into two stages, wherein the first stage is a disturbance-free grid-connected process of a grid-connected circuit, zero current impact on a grid side is realized, the second stage is a mode switching process, and the function of gradually switching the voltage conversion device from zero current output to a final steady-state operation mode is automatically realized; the invention provides a general flow, which automatically realizes the grid-connected stable operation of the voltage conversion device, ensures the non-disturbance and full-automatic operation of the whole process and improves the reliability of each operation step.
Drawings
FIG. 1 is a schematic topology of a grid-connected system of a power electronic voltage conversion device of the present invention;
FIG. 2 is a flow chart of the grid-connected mode switching control of the power electronic voltage conversion device of the present invention;
FIG. 3 is a schematic diagram of an embodiment of voltage regulation during a grid-connected start-up phase of the power electronic voltage conversion device of the present invention, wherein (a) is an AC port grid-connection and (b) is a DC port grid-connection;
fig. 4 is a schematic diagram of mode switching after ac port and dc port of the power electronic voltage conversion device are connected in grid, wherein (a) is ac port connection and (b) is dc port connection.
Detailed Description
The technical scheme of the invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 is a schematic topology of an exemplary system for grid-tie mode switching of the present invention. Fig. 2 is a flowchart of a method for controlling port grid-connected mode switching of a power electronic voltage conversion device. The topology of the power electronic voltage conversion device in fig. 1 is a common topology and is not described here.
A port grid-connected mode switching method for a power electronic voltage conversion device is characterized in that a set of grid-connected circuits are connected in series to an output port of the power electronic voltage conversion device, and each grid-connected circuit comprises bus equipment to be combined, a voltage transformer Ts at the output end of the power electronic voltage conversion device at the grid-connected side and a grid-connected starting circuit. The bus equipment comprises a bus side switch Ks and a bus side voltage transformer Tv; the grid-connected starting circuit comprises a grid-connected switch K1, a grid-connected starting resistor R and a starting resistor bypass switch K2, wherein the grid-connected switch K1 is connected with the grid-connected starting resistor R in series, and the starting resistor bypass switch K2 is connected with the starting resistor R in parallel.
The circuit in fig. 1 is an ac port grid-connected typical topology circuit of the power electronic voltage conversion device, the grid-connected starting circuit, the to-be-combined side bus device and the conversion device side voltage transformer are all configured in a three-phase structure, and if the dc port of the power electronic voltage conversion device is grid-connected, the grid-connected starting circuit, the to-be-combined side bus device and the conversion device side voltage transformer are configured in a bipolar structure.
In this embodiment, only the ac-side port grid connection of the voltage conversion device will be described as an example.
The grid-connected control method of the power electronic voltage conversion device (electric energy conversion device) comprises the following steps:
s1: the power supply side is electrified;
s2: unlocking a power converter valve in the topology of the power electronic voltage conversion device;
s3: the voltage transformer on the side of the bus to be combined detects the voltage on the side of the bus to be combined, and adjusts the voltage on the grid-connected side of the power electronic voltage conversion device so as to control the voltage within the allowable range of the voltage deviation of the voltage on the side of the bus to be combined;
s4: the grid-connected switch is switched on, and two sides (a grid-connected side and a to-be-combined side) of the grid-connected starting circuit are electrically connected through a starting resistor;
s5: a closing bypass switch cuts off the grid-connected starting resistor from the grid-connected loop;
s6: after grid connection detection is completed, mode switching is performed:
if the voltage reference value is the direct current side grid connection, the voltage reference value is adjusted or switched to be in constant power operation according to the voltage mode set value;
if the voltage is the AC side grid connection, gradually increasing a DC side voltage reference value or an active power reference value according to an active regulation mode set value; and switching to a reactive power mode or slowly adjusting the alternating-current side voltage reference value according to the reactive power adjustment mode set value.
S3, after the direct current side of the voltage conversion device is electrified, regulating the voltage U_port of the grid-connected alternating current port of the voltage conversion device, controlling the amplitude and the frequency of the port voltage of the grid-connected side within the allowable deviation range with the voltage U_BUS of the grid to be combined, controlling the frequency within 0.1Hz deviation, and controlling the voltage amplitude within 5% deviation; FIG. 3 shows a voltage converter grid-tied port voltage and bus side voltage vector diagram (wherein (a) is an AC port grid-tied voltage control vector diagram and (b) is a DC port grid-tied voltage control vector diagram)
Step S4 and step S5 of the grid-connected mode switching method, if one of the voltages collected by the voltage transformers at the two sides of the grid-connected switch is zero, grid connection is performed according to the ports of the direct current voltage conversion device in the step S4 and step S5; if the voltage acquired by the voltage transformers at the two sides of the grid-connected switch K1 is within the S3 description deviation range and the voltage phase is within 5deg, the bypass switch K2 can be closed first, and then the grid-connected switch K1 is closed, so that zero current impact grid connection of the alternating current port of the power electronic voltage conversion device can be realized.
In step S6 of the grid-connected mode switching method, for the ac port grid connection of the power electronic conversion device of fig. 1, the ac port starting process is controlled to be in an ac side voltage control mode (uac_ctlmode), the active current is controlled to be in a zero power control mode (p_ctlmode), the initial ac side voltage reference value is set to be the bus voltage to be combined, and the output voltage frequency is controlled within the frequency deviation range with the bus voltage to be combined. After the grid connection is successful, the reactive current control keeps constant voltage control or is switched to a reactive power control mode (Q_ctlmode), and the active current control keeps the power reference value step by step or is switched to a constant direct current side voltage control mode (udc_ctlmode). A schematic diagram of mode switching after grid-tie is identified in fig. 4 (where (a) is an ac port grid-tie mode switching schematic diagram and (b) is a dc port grid-tie mode switching schematic diagram).
The mode switching control principle is as follows: and after grid connection, the reactive power active operation mode and the power output are gradually adjusted from zero power to the final operation.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the technical solution of the present invention; it should be noted that: the technical solutions described in the foregoing embodiments are modified or some of the technical features thereof are replaced by equivalents, so that the essence of the corresponding technical solutions does not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. The control method for the grid-connected mode switching of the power electronic voltage conversion device is characterized in that an output port of the power electronic voltage conversion device is connected in series with a set of grid-connected circuit, and the grid-connected circuit comprises a voltage transformer at the output end of the grid-connected side power electronic voltage conversion device, a grid-connected starting circuit and bus equipment to be combined;
the grid-connected starting circuit comprises a grid-connected switch, a grid-connected starting resistor and a starting resistor bypass switch, wherein one end of the grid-connected switch is used as an output end of the grid-connected starting circuit to be connected with an input end of the bus equipment to be combined, the other end of the grid-connected switch is connected with one end of the grid-connected starting resistor, the other end of the grid-connected starting resistor is used as an input end of the grid-connected starting circuit to be connected with an output end of the power electronic voltage conversion device through a voltage transformer at an output end of the grid-connected side conversion device, and the starting resistor bypass switch is connected with the grid-connected starting resistor in parallel;
the device for the bus to be combined comprises a bus to be combined side switch and a bus to be combined side voltage transformer, wherein one end of the bus to be combined side switch is used as an input end of the bus to be combined side device, the other end of the bus to be combined side switch is connected with a bus to be combined side, and the bus to be combined side voltage transformer is connected with the bus to be combined side;
the control method for grid-connected mode switching of the power electronic voltage conversion device comprises the following steps:
s1: when the bus side switch is switched on, the power supply side of the power electronic voltage conversion device is electrified;
s2: unlocking a power converter valve in the topology of the power electronic voltage conversion device;
s3: the voltage transformer on the side of the bus to be combined detects the voltage on the side of the bus to be combined, and the power electronic voltage conversion device on the side of the grid connection controls the voltage on the side of the grid connection within the allowable range of the voltage deviation between the voltage transformer on the side of the bus to be combined and the voltage transformer on the side of the bus to be combined;
s4: the grid-connected switch is switched on, and the grid-connected side and the to-be-combined side are electrically connected through a grid-connected starting resistor;
s5: starting a resistor bypass switch to switch on;
s6: after the power electronic voltage conversion device is electrically connected with the bus to be parallel through the grid-connected switch and the bypass switch, the power electronic voltage conversion device performs control mode switching, and the power electronic voltage conversion device comprises the following two conditions:
if the bus to be combined is a direct current bus, regulating a voltage reference value according to a set value of a voltage mode or switching a control mode into constant power operation according to a set rate;
if the bus to be combined is an alternating current bus, regulating a direct current side voltage reference value or an active power reference value according to a set value of an active regulation mode at a set rate; and according to the reactive power regulation mode set value, switching the control mode into a reactive power mode or regulating the alternating current side voltage reference value according to a set rate.
2. The method for controlling grid-connected mode switching of a power electronic voltage conversion device according to claim 1, wherein the power electronic voltage conversion device comprises N ports, and N is more than or equal to 1; according to whether the output voltage of the port is alternating current or direct current, the port is divided into an alternating current port and a direct current port; the ports are divided into power ports and load ports according to the type of devices to which the ports are connected.
3. The method for controlling grid-connected mode switching of a power electronic voltage conversion device according to claim 1 or 2, wherein in S3, if the bus to be connected is an ac bus, the amplitude and frequency of the voltage on the grid-connected side are controlled within a deviation range from the grid on the side to be connected; and if the bus to be parallel connected is a direct current bus, controlling the amplitude of the voltage at the grid-connected side within the deviation range with the power grid to be parallel connected.
4. The method for controlling grid-connected mode switching of a power electronic voltage conversion device according to claim 1 or 2, wherein in S3-S5, if the parallel bus loses power, grid connection is performed through a grid-connected starting resistor, and then the starting resistor is bypassed through a bypass switch to realize grid connection of the power electronic voltage conversion device at the grid-connected side; and if the voltage deviation of the two sides of the grid-connected starting circuit is in the allowable range, the grid connection of the grid-connected side power electronic voltage conversion device is realized through a direct-closing grid-connected switch and a bypass switch.
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| CN202010711207.5A CN113972683B (en) | 2020-07-22 | 2020-07-22 | Grid-connected mode switching control method of power electronic voltage conversion device |
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| CN202010711207.5A CN113972683B (en) | 2020-07-22 | 2020-07-22 | Grid-connected mode switching control method of power electronic voltage conversion device |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108649606A (en) * | 2018-05-25 | 2018-10-12 | 易事特集团股份有限公司 | And off-network switching device |
| CN110690731A (en) * | 2019-08-20 | 2020-01-14 | 东南大学 | Power electronic transformer applicable to hybrid micro-grid and coordination control and mode switching method thereof |
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2020
- 2020-07-22 CN CN202010711207.5A patent/CN113972683B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108649606A (en) * | 2018-05-25 | 2018-10-12 | 易事特集团股份有限公司 | And off-network switching device |
| CN110690731A (en) * | 2019-08-20 | 2020-01-14 | 东南大学 | Power electronic transformer applicable to hybrid micro-grid and coordination control and mode switching method thereof |
Non-Patent Citations (1)
| Title |
|---|
| 虚拟同步发电机并离网无缝切换控制策略研究;唐酿 等;可再生能源;20161120(第11期);1665-1673 * |
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