CN114498776A - Reactive overload judgment and control method and device for flexible direct current island converter station - Google Patents
Reactive overload judgment and control method and device for flexible direct current island converter station Download PDFInfo
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- CN114498776A CN114498776A CN202011153564.0A CN202011153564A CN114498776A CN 114498776 A CN114498776 A CN 114498776A CN 202011153564 A CN202011153564 A CN 202011153564A CN 114498776 A CN114498776 A CN 114498776A
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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
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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Abstract
The application discloses an island converter station reactive overload judgment control method, and belongs to the field of flexible direct current transmission. The method comprises the following steps: the island converter station adopts island alternating current voltage control; calculating actual active power and actual reactive power of the island converter station in real time; calculating a corresponding reactive power operation interval under the current actual active power according to a PQ operation interval of the island converter station; and comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, changing the alternating voltage instruction value to adjust the reactive power of the system by adjusting the alternating voltage so as to enable the reactive power to return to the power interval range. The technical scheme can avoid the damage to the system caused by the fact that the long-term reactive power of the island station exceeds the PQ operation range, and ensure the safe and stable operation of the system.
Description
Technical Field
The application belongs to the technical field of flexible direct current transmission of a power system, and particularly relates to a reactive overload judgment and control method and device for an island converter station.
Background
The flexible direct current transmission technology is a new generation of high-voltage direct current transmission technology, and is characterized in that independent control of active power and reactive power can be realized, and phase commutation is supported without short-circuit capacity of an alternating current power grid, so that the problem that clean energy such as wind power, photovoltaic and the like is connected into the power grid is solved, and the flexible direct current transmission technology has a good development prospect. Due to the limitation of the converter and the conversion variable capacity, active power and reactive power must be limited within a specific range of a PQ plane in the same converter station, otherwise, the capacity limit of equipment can be exceeded, so that the equipment is damaged, and the safe operation of the system is threatened.
An island alternating voltage control strategy is generally adopted for an offshore wind power flexible direct current transmission project offshore converter station as a sending end converter station, alternating voltage on a grid side of the converter station is taken as a control target, active power of the offshore converter station is provided by a wind power plant, when reactive power sent by the wind power plant is excessive or a flexible direct current system has large reactive load, the reactive power of the converter station is large and possibly exceeds a PQ interval of system operation, the safe and stable operation of the system is threatened, and at the moment, certain overload control strategy is required to be adopted to reduce the reactive power of the system. At present, overload control strategies of the flexible direct current converter station mainly aim at active power overload of a system, the correction of active power out-of-limit is realized by adjusting the output of a generator and cutting off load, and the control strategies have limited reactive power regulation capacity of the system.
At present, documents only relate to a control strategy aiming at reactive overload of an island system, and the stable operation of an island converter station is an important premise of the internet access and consumption of renewable energy sources, so that an overload control strategy suitable for the island station is needed to be found, and when the island station generates reactive overload, the overload is actively adjusted to return to a PQ operation interval again, so that the safe and stable operation of the system is ensured, and the important practical requirement is met.
Disclosure of Invention
The application aims to overcome the defects in the prior art, and provides the overload control method and device for the island station of the flexible direct current transmission system, so that the damage to the system caused by the fact that the long-term reactive power of the island station exceeds the PQ operation range can be avoided, and the safe and stable operation of the system is ensured.
In order to achieve the purpose, the technical scheme adopted by the application is as follows:
on one hand, the application provides an island converter station reactive overload judgment control method, which comprises the following steps:
the island converter station adopts island alternating current voltage control;
calculating actual active power and actual reactive power of the island converter station in real time;
calculating a corresponding reactive power operation interval under the current actual active power according to a PQ operation interval of the island converter station;
and comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, changing the alternating voltage instruction value to adjust the reactive power of the system by adjusting the alternating voltage so as to enable the reactive power to return to the power interval range.
In an optimal scheme, if the actual reactive power is not within the reactive power operation interval, changing the ac voltage command value to adjust the reactive power of the system by adjusting the ac voltage, specifically: when the positive direction of the reactive power is positive for absorbing inductive reactive power, if the actual reactive power is higher than the upper limit of the reactive power operation interval, increasing the alternating voltage instruction value, and reducing the reactive power by increasing the alternating voltage; and if the actual reactive power is lower than the lower limit of the reactive power operation interval, reducing the alternating voltage instruction value, increasing the reactive power by reducing the alternating voltage, and when the actual reactive power returns to the reactive power operation interval, stopping increasing the alternating voltage, wherein the alternating voltage instruction value is kept at the current value. If the positive reactive power direction is defined to be opposite, the voltage regulation direction is also opposite.
In a preferred embodiment, the voltage can only be adjusted within the range of the upper limit and the lower limit of the ac voltage, and the ac voltage does not increase or decrease any more when the ac voltage reaches the allowable upper limit and lower limit.
In the preferred scheme, when the alternating voltage is regulated to the upper and lower voltage limits and the actual reactive power is still not in the reactive power operation interval, the system stops regulating the alternating voltage, and at the moment, the system judges that the reactive power exceeds the limit and processes the reactive power.
In a preferred scheme, the method for processing by the system comprises the following steps: and locking the current converter after delaying the preset time, and tripping off the AC incoming line switch.
In a preferred scheme, the method for processing by the system comprises the following steps: and requesting a fan cutter to reduce reactive load, or only giving a background alarm to remind an operator to process.
In a preferred aspect, the method of changing the ac voltage command value includes: and adjusting the alternating voltage command value at a preset rate, or adjusting the alternating voltage command value in a segmented rate division manner, or adjusting the alternating voltage command value in a step manner, or calculating the deviation between the reactive power limit target value and the actual reactive power to obtain a voltage deviation value to be superposed on the alternating voltage command value.
In a preferred embodiment, the island converter station adopts island ac voltage control, that is: the outer loop control generates an active current instruction, a reactive current instruction and a reference phase instruction according to the deviation of the alternating voltage instruction and the actual alternating voltage; the inner ring obtains a reference value of the modulation voltage by adopting current control.
In a preferred scheme, the PQ operation interval of the island converter station is provided by a converter station set design.
On the other hand, the application provides an island converter station reactive overload judgment control device which comprises a power calculation module, a reactive power operation interval calculation module, a reactive power regulation module and a closed-loop control module which are connected in sequence; wherein:
the power calculation module is used for calculating the actual active power and the actual reactive power of the island converter station in real time;
the reactive power operation interval calculation module is used for calculating a corresponding reactive power operation interval under the current actual active power according to a PQ operation interval of the island converter station;
the reactive power adjusting module is used for comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, the reactive power of the system is adjusted by changing the alternating voltage instruction value of the closed-loop control module and adjusting the alternating voltage so as to return to the power interval range;
and the closed-loop control module is used for controlling the island converter station by adopting an island alternating-current voltage control method.
In a preferred embodiment, in the reactive power adjusting module: when the positive direction of the reactive power is positive for absorbing inductive reactive power, if the actual reactive power is higher than the upper limit of the reactive power operation interval, increasing the alternating voltage instruction value, and reducing the reactive power by increasing the alternating voltage; and if the actual reactive power is lower than the lower limit of the reactive power operation interval, reducing the alternating voltage instruction value, increasing the reactive power by reducing the alternating voltage, and when the actual reactive power returns to the reactive power operation interval, stopping increasing the alternating voltage, wherein the alternating voltage instruction value is kept at the current value. If the positive reactive power direction is defined to be opposite, the voltage regulation direction is also opposite
In a preferred scheme, the voltage can only be adjusted within the range of the upper limit and the lower limit of the alternating voltage by changing the alternating voltage instruction value in the reactive power adjusting module, and the alternating voltage does not continuously increase or decrease when the alternating voltage reaches the allowable upper limit and lower limit.
In a preferred scheme, the overload judgment and control device for the island converter station further includes a reactive power out-of-limit processing module. In the reactive power adjusting module, when the alternating voltage is adjusted to the upper limit and the lower limit of the voltage and the actual reactive power is still not in the reactive power operation interval, the adjustment of the alternating voltage is stopped, the reactive power out-of-limit is judged, and the reactive power out-of-limit processing module is triggered. And the reactive power out-of-limit processing module is used for processing the reactive power out-of-limit condition of the system.
In a preferred scheme, the reactive out-of-limit processing module: the switch is used for locking the current converter after delaying preset time and tripping the AC inlet switch.
In a preferred scheme, the reactive out-of-limit processing module: for requesting the fan cutter to reduce the reactive load.
In a preferred scheme, the reactive out-of-limit processing module: the alarm device is used for triggering background alarm to remind operators to process.
In a preferred embodiment, the method for changing the ac voltage command value in the reactive power regulation module includes: and adjusting the alternating voltage command value at a preset rate, or adjusting the alternating voltage command value in a segmented rate division manner, or adjusting the alternating voltage command value in a step manner, or calculating the deviation between the reactive power limit target value and the actual reactive power to obtain a voltage deviation value to be superposed on the alternating voltage command value.
In a preferred scheme, the closed-loop control module comprises an outer loop control and an inner loop control, wherein the outer loop control generates an active current instruction, a reactive current instruction and a reference phase instruction according to the deviation of an alternating voltage instruction and actual alternating voltage; the inner ring obtains a reference value of the modulation voltage by adopting current control.
The beneficial effect of this application does:
(1) according to the technical scheme, the reactive power is actively controlled, and the alternating voltage changes smoothly, so that the damage to the safe operation of the system caused by the long-term exceeding of the PQ operation range of an island station is avoided, and a better alternating current control characteristic can be obtained;
(2) according to the technical scheme, when the PQ operation interval crossing cannot be avoided by adjusting the voltage, the system is actively tripped or a request fan is cut off, so that damage to the system caused by long-term overload of an island station is avoided.
Drawings
FIG. 1 is a schematic diagram of a flexible DC power transmission system;
FIG. 2 is a closed loop control block diagram of an island station;
fig. 3 is a flowchart of an island converter station reactive overload determination control method according to an embodiment of the present application;
FIG. 4 is a reactive overload control block diagram of an island station;
FIG. 5 is a schematic diagram of an island station PQ operation interval;
fig. 6 is a flowchart of a reactive overload determination control method for an island converter station according to another embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application more clearly understood, the technical solutions of the present application will be described in detail below with reference to the accompanying drawings and specific embodiments.
The schematic diagram of the two-end flexible direct-current transmission system is shown in fig. 1, and mainly comprises an island operation converter station and a constant direct-current voltage operation converter station. As shown in fig. 2, after the island station is unlocked, island alternating-current voltage control is adopted, an active current instruction Idref, a reactive current instruction Iqref and a reference phase instruction θ are generated by outer-loop control according to the deviation between an alternating-current voltage instruction and actual alternating-current voltage, a modulation voltage reference value Udref and a modulation voltage reference value Uqref are obtained by inner-loop control through current control, and a three-phase modulation voltage reference value is obtained through dq/abc conversion.
As shown in fig. 3, an embodiment of a reactive overload determination and control method for an island converter station according to the present application includes the following steps:
and S101, adopting island alternating current voltage control for the island converter station.
And S102, calculating the actual active power and the actual reactive power of the island converter station in real time.
And S103, calculating a corresponding reactive power operation interval under the current actual active power according to the PQ operation interval of the island converter station. Wherein the PQ operation interval of the island converter station can be provided by a converter station set design.
And S104, comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, changing the alternating voltage instruction value to adjust the reactive power of the system by adjusting the alternating voltage so as to enable the reactive power to return to the power interval range. As shown in the islanding station reactive overload control block diagram shown in fig. 4.
Specifically, when the positive direction of the reactive power is positive for absorbing inductive reactive power, if the actual reactive power is higher than the upper limit of the reactive power operation interval, the alternating voltage instruction value is increased, and the reactive power is reduced by increasing the alternating voltage; and if the actual reactive power is lower than the lower limit of the reactive power operation interval, reducing the alternating voltage instruction value, increasing the reactive power by reducing the alternating voltage, and when the actual reactive power returns to the reactive power operation interval, stopping increasing the alternating voltage, wherein the alternating voltage instruction value is kept at the current value. If the positive reactive power direction is defined to be opposite, the voltage regulation direction is also opposite.
In a preferred embodiment, the voltage can only be adjusted within the range of the upper limit and the lower limit of the alternating voltage by changing the alternating voltage command value, and the alternating voltage does not continue to be increased or decreased when the alternating voltage reaches the allowable upper limit and lower limit.
In a preferred embodiment, on the basis of the first embodiment, when the ac voltage is adjusted to the upper and lower voltage limits and the actual reactive power is still not within the reactive power operation interval, the system stops adjusting the ac voltage, and at this time, the system determines that the reactive power is out of limit and performs processing. The system processing method comprises the steps of locking the current converter after delaying preset time and tripping off the alternating current incoming line switch. The system processing method can also reduce reactive load by requesting a fan cutter, or only give an alarm at a background to remind operators to process.
In a preferred embodiment, the method of changing the alternating voltage command value includes: and adjusting the alternating voltage command value at a preset rate, or adjusting the alternating voltage command value in a segmented rate division manner, or adjusting the alternating voltage command value in a step manner, or calculating the deviation between the reactive power limit target value and the actual reactive power to obtain a voltage deviation value to be superposed on the alternating voltage command value.
Fig. 6 shows another embodiment of the island converter station reactive overload judgment control method according to the present application. According to the basic characteristics of the power grid, the reactive power absorbed or sent by the converter station can be controlled by adjusting the alternating voltage of the flexible direct current converter station, and the reactive power can be increased by reducing the alternating voltage and can be reduced by increasing the alternating voltage by taking the inductive reactive power as positive. The concrete implementation process of the method is described below by taking an island alternating-current voltage control converter station as an example.
(1) Acquiring three-phase voltage actual values Usa, Usb and Usc and three-phase current actual values Isa, Isb and Isc at the alternating current side of the island station; and obtaining the synchronous rotation angle theta through a phase-locked loop.
(2) D and q axis components Usd and Usq of the alternating voltage and d and q axis components Isd and Isq of the alternating current are obtained through dq coordinate transformation.
(3) And calculating to obtain an active power real-time value Ps and a reactive power real-time value Qs through d and q axis components Usd and Usq of the alternating voltage and d and q axis components Isd and Isq of the alternating current.
(4) The schematic diagram of the operation interval of the island station PQ is shown in fig. 5, wherein the horizontal axis represents active power, and the vertical axis represents reactive power. And calculating the operation range of reactive power according to the current active power real-time value Ps of the island converter station, and obtaining the maximum value Qs _ max and the minimum value Qs _ min of the reactive power allowed by the system according to the PQ operation interval.
(5) Setting the AC voltage operating range from Us _ min to Us _ max according to the actual operating requirement, wherein the AC voltage command value is Us during normal operation*。
(6) And (4) comparing the reactive power real-time value Qs calculated in the step (3) with the reactive power operation range obtained in the step (4), if Qs _ min is less than or equal to Qs _ max, namely the reactive power falls in the PQ operation interval, not adjusting the alternating voltage, and ending the flow, otherwise, entering the step (7).
(7) Comparing the real-time value Qs of the reactive power calculated in the step (3) with the reactive operation range obtained in the step (4), and if Qs is larger than Qs _ max, namely the reactive power exceeds the upper limit value of a PQ operation interval, entering a step (8); and (5) if Qs is less than Qs _ min, namely the reactive power is less than the lower limit value of the PQ operation interval, entering the step (11).
(8) The reactive power is reduced by raising the AC voltage command value at a rate of alpha kV/s, specifically, the AC voltage adjustment amount delta Us is increased from 0 at a rate of alpha kV/sIncreased and then compared with the command value Us of the alternating voltage*And (6) superposing.
(9) And detecting the value of the reactive power of the current converter station in real time, and if the reactive power returns to the PQ operation interval, stopping increasing the alternating voltage, and keeping the alternating voltage command value at the current value.
(10) When the alternating voltage is increased to Us _ max, the alternating voltage is not increased any more, if the reactive power is still out of limit, the system trips after delaying for a period of time, and the action result is
a. Blocking current converter
b. Tripping the AC inlet switch;
the reactive overload adjustment is finished.
(11) Reducing the AC voltage command value at a rate of alpha kV/s, raising the reactive power by reducing the AC voltage, specifically, reducing the AC voltage regulation amount delta Us from 0 at a rate of alpha kV/s, and then comparing the AC voltage regulation amount delta Us with the AC voltage command value Us*And (6) superposing.
(12) And detecting the value Qs of the reactive power of the current converter station in real time, and stopping reducing the alternating voltage if the reactive power Qs returns to the PQ operation interval, namely Qs _ min is less than or equal to Qs and less than or equal to Qs _ max, and keeping the alternating voltage command value at the current value.
(13) When the alternating voltage is reduced to Us _ min, the alternating voltage is not reduced continuously, if the reactive power is still out of limit, the system trips after delaying for a period of time, and the action result is
a. Blocking current converter
b. Tripping the AC inlet switch;
the reactive overload adjustment is finished.
The application provides an embodiment of an island converter station reactive overload judgment control device, which comprises a power calculation module, a reactive power operation interval calculation module, a reactive power regulation module and a closed-loop control module which are connected in sequence; wherein:
the power calculation module is used for calculating the actual active power and the actual reactive power of the island converter station in real time;
the reactive power operation interval calculation module is used for calculating a corresponding reactive power operation interval under the current actual active power according to a PQ operation interval of the island converter station;
the reactive power adjusting module is used for comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, the reactive power of the system is adjusted by changing the alternating voltage instruction value of the closed-loop control module and adjusting the alternating voltage so as to return to the power interval range;
and the closed-loop control module is used for controlling the island converter station by adopting an island alternating-current voltage control method.
In a preferred embodiment, in the reactive power regulating module: when the positive direction of the reactive power is positive for absorbing inductive reactive power, if the actual reactive power is higher than the upper limit of the reactive power operation interval, increasing the alternating voltage instruction value, and reducing the reactive power by increasing the alternating voltage; and if the actual reactive power is lower than the lower limit of the reactive power operation interval, reducing the alternating voltage instruction value, increasing the reactive power by reducing the alternating voltage, and when the actual reactive power returns to the reactive power operation interval, stopping increasing the alternating voltage, wherein the alternating voltage instruction value is kept at the current value. If the positive reactive power direction is defined to be opposite, the voltage regulation direction is also opposite
In a preferred embodiment, the voltage can only be adjusted within the range of the upper limit and the lower limit of the alternating voltage by changing the alternating voltage command value in the reactive power adjusting module, and the alternating voltage does not increase or decrease any more when the alternating voltage reaches the allowable upper limit and lower limit.
In a preferred embodiment, the island converter station overload judgment and control device further includes a reactive power out-of-limit processing module. In the reactive power adjusting module, when the alternating voltage is adjusted to the upper limit and the lower limit of the voltage and the actual reactive power is still not in the reactive power operation interval, the adjustment of the alternating voltage is stopped, the reactive power out-of-limit is judged, and the reactive power out-of-limit processing module is triggered. And the reactive power out-of-limit processing module is used for processing the reactive power out-of-limit condition of the system.
In a preferred embodiment, the reactive out-of-limit processing module: the switch is used for locking the current converter after delaying preset time and tripping the AC inlet switch.
In a preferred embodiment, the reactive out-of-limit processing module: for requesting the fan cutter to reduce the reactive load.
In a preferred embodiment, the reactive out-of-limit processing module: the alarm device is used for triggering background alarm to remind operators to process.
In a preferred embodiment, the method for changing the command value of the alternating voltage in the reactive power regulation module comprises the following steps: and adjusting the alternating voltage command value at a preset rate, or adjusting the alternating voltage command value in a segmented rate division manner, or adjusting the alternating voltage command value in a step manner, or calculating the deviation between the reactive power limit target value and the actual reactive power to obtain a voltage deviation value to be superposed on the alternating voltage command value.
In a preferred embodiment, the closed-loop control module comprises an outer loop control and an inner loop control, wherein the outer loop control generates an active current instruction, a reactive current instruction and a reference phase instruction according to the deviation between an alternating voltage instruction and actual alternating voltage; the inner ring obtains a reference value of the modulation voltage by adopting current control.
The above embodiments are only for illustrating the technical idea of the present application, and the protection scope of the present application is not limited thereby, and any modifications made on the basis of the technical solution according to the technical idea presented in the present application fall within the protection scope of the present application.
Claims (18)
1. A reactive overload judgment and control method for an island converter station is characterized in that,
the island converter station adopts island alternating current voltage control;
calculating actual active power and actual reactive power of the island converter station in real time;
calculating a corresponding reactive power operation interval under the current actual active power according to a PQ operation interval of the island converter station;
and comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, changing the alternating voltage instruction value to adjust the reactive power of the system by adjusting the alternating voltage so as to enable the reactive power to return to the power interval range.
2. The island converter station overload judgment and control method according to claim 1, wherein if the actual reactive power is not within the reactive power operation interval, the system reactive power is adjusted by changing the ac voltage command value and adjusting the ac voltage, specifically:
when the positive direction of the reactive power is positive for absorbing inductive reactive power, if the actual reactive power is higher than the upper limit of the reactive power operation interval, increasing the alternating voltage instruction value, and reducing the reactive power by increasing the alternating voltage; if the actual reactive power is lower than the lower limit of the reactive power operation interval, reducing the alternating voltage instruction value, increasing the reactive power by reducing the alternating voltage, and when the actual reactive power returns to the reactive power operation interval, stopping increasing the alternating voltage, wherein the alternating voltage instruction value is kept at the current value;
if the positive reactive power direction is defined to be opposite, the voltage regulation direction is also opposite.
3. An island converter station overload judgment and control method according to claim 1, wherein the alternating voltage command value is changed to adjust the voltage only within the range of the upper limit and the lower limit of the alternating voltage, and when the alternating voltage reaches the allowable upper limit and lower limit, the alternating voltage is not increased or decreased.
4. The island converter station overload judgment control method according to claim 3, wherein when the alternating voltage is regulated to the upper and lower voltage limits and the actual reactive power is still not in the reactive power operation interval, the system stops regulating the alternating voltage, and the system judges that the reactive power is out of limit and processes the reactive power.
5. An island converter station overload judgment and control method according to claim 4, characterized in that the system processing method comprises: and locking the current converter after delaying the preset time, and tripping off the AC incoming line switch.
6. An island converter station overload judgment and control method according to claim 4, characterized in that the system processing method comprises: and requesting a fan cutter to reduce reactive load, or only giving a background alarm to remind an operator to process.
7. An island converter station overload judgment and control method according to claim 1, wherein the method for changing the alternating voltage command value comprises the following steps: and adjusting the alternating voltage command value at a preset rate, or adjusting the alternating voltage command value in a segmented rate division manner, or adjusting the alternating voltage command value in a step manner, or calculating the deviation between the reactive power limit target value and the actual reactive power to obtain a voltage deviation value to be superposed on the alternating voltage command value.
8. The island converter station overload judgment and control method according to claim 1, wherein the island converter station adopts island alternating voltage control, namely: the outer loop control generates an active current instruction, a reactive current instruction and a reference phase instruction according to the deviation of the alternating voltage instruction and the actual alternating voltage; the inner ring obtains a reference value of the modulation voltage by adopting current control.
9. The method for judging and controlling overload of the island converter station according to claim 1, wherein the PQ operation interval of the island converter station is provided by a converter station set design.
10. A reactive overload judgment and control device for an island converter station is characterized by comprising a power calculation module, a reactive power operation interval calculation module, a reactive power regulation module and a closed-loop control module which are connected in sequence;
the power calculation module is used for calculating the actual active power and the actual reactive power of the island converter station in real time;
the reactive power operation interval calculation module is used for calculating a corresponding reactive power operation interval under the current actual active power according to a PQ operation interval of the island converter station;
the reactive power adjusting module is used for comparing the actual reactive power with the reactive power operation interval, and if the actual reactive power is not in the reactive power operation interval, the reactive power of the system is adjusted by changing the alternating voltage instruction value of the closed-loop control module and adjusting the alternating voltage so as to return to the power interval range;
and the closed-loop control module is used for controlling the island converter station by adopting an island alternating-current voltage control method.
11. An island converter station overload judgment and control apparatus according to claim 10, wherein in the reactive power regulation module: when the positive direction of the reactive power is positive for absorbing inductive reactive power, if the actual reactive power is higher than the upper limit of the reactive power operation interval, increasing the alternating voltage instruction value, and reducing the reactive power by increasing the alternating voltage; if the actual reactive power is lower than the lower limit of the reactive power operation interval, reducing the alternating voltage instruction value, increasing the reactive power by reducing the alternating voltage, and when the actual reactive power returns to the reactive power operation interval, stopping increasing the alternating voltage, wherein the alternating voltage instruction value is kept at the current value; if the positive reactive power direction is defined to be opposite, the voltage regulation direction is also opposite.
12. An island converter station overload judgment and control device according to claim 10, wherein the reactive power regulation module changes the alternating voltage command value to regulate the voltage only within the range of the upper limit and the lower limit of the alternating voltage, and when the alternating voltage reaches the allowable upper limit and lower limit, the alternating voltage is not increased or decreased.
13. The island converter station overload judgment and control device according to claim 12, further comprising a reactive power violation processing module,
in the reactive power adjusting module, when the alternating voltage is adjusted to the upper limit and the lower limit of the voltage and the actual reactive power is still not in the reactive power operation interval, the adjustment of the alternating voltage is stopped, the reactive power violation is judged, and the reactive power violation processing module is triggered;
and the reactive power out-of-limit processing module is used for processing the reactive power out-of-limit condition of the system.
14. An island converter station overload judgment and control apparatus according to claim 13, wherein the reactive power off-limit processing module: the switch is used for locking the current converter after delaying preset time and tripping the AC inlet switch.
15. The island converter station overload judgment control device according to claim 13, wherein the reactive power violation processing module is configured to: for requesting fan cutter to reduce reactive load.
16. An island converter station overload judgment and control apparatus according to claim 13, wherein the reactive power off-limit processing module: and the alarm device is used for triggering background alarm to remind operating personnel to process.
17. The island converter station overload judgment and control device according to claim 10, wherein the method for changing the alternating voltage command value in the reactive power regulation module comprises the following steps: and adjusting the alternating voltage command value at a preset rate, or adjusting the alternating voltage command value in a segmented rate division manner, or adjusting the alternating voltage command value in a step manner, or calculating the deviation between the reactive power limit target value and the actual reactive power to obtain a voltage deviation value to be superposed on the alternating voltage command value.
18. The island converter station overload judgment and control device according to claim 10, wherein the closed-loop control module comprises an outer loop control and an inner loop control, the outer loop control generates an active current command, a reactive current command and a reference phase command according to a deviation of the ac voltage command and an actual ac voltage; the inner ring obtains a reference value of the modulation voltage by adopting current control.
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