Method and device for controlling power surplus of flexible direct current power transmission and electronic equipment

Abstract

The application provides a flexible direct current power surplus control method and device and electronic equipment. The method comprises the following steps: judging whether a fault occurs in a flexible direct current power transmission system or power emergency regulation is provided; in the case that the fault occurs in the flexible direct current power transmission system or the power emergency regulation is provided, judging whether surplus power is generated in the flexible direct current power transmission system; in the case that the surplus power is generated in the flexible direct current power transmission system, determining a sending end alternating current voltage setting value of the flexible direct current power transmission system, adjusting the sending end alternating current voltage of the flexible direct current power transmission system to the sending end alternating current voltage setting value, so that an external sending end system enters a low voltage ride through mode. When the fault or the emergency power regulation occurs, the flexible direct current power transmission system actively adjusts the sending end alternating current voltage of a converter station, and assists a power generation end to reduce its own power output, so that the fault ride through or the emergency power regulation can be completed without installing a direct current energy consumption device on a high voltage direct current side, and the investment and maintenance cost of the flexible direct current power transmission system is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible HVDC power transmission, in particular to a method and device for controlling surplus power in a flexible HVDC power transmission system and an electronic device. BACKGROUND

[0002] In a high voltage direct current (HVDC) power transmission system, fault ride through is a very important requirement. If the generation end is an inertia source similar to wind power, when a fault occurs at the receiving end, the power cannot be sent out, and energy will accumulate on the DC side, causing the voltage of the DC transmission line to rise, which will harm the safe operation of the equipment.

[0003] Currently, a DC energy consumption device installed on the HVDC line is used to absorb the surplus power; however, the installation of the DC energy consumption device is costly and subsequent maintenance is troublesome.

[0004] The above information disclosed in the background section is only intended to enhance the understanding of the background of the present application, and therefore it can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0005] To solve the above problems, the present application proposes a method and device for controlling surplus power in a flexible HVDC power transmission system and an electronic device.

[0006] According to a first aspect of the present application, a method for controlling surplus power in a flexible HVDC power transmission system is provided, the method comprising:

[0007] determining whether a fault occurs in the flexible HVDC power transmission system or whether power emergency regulation is provided;

[0008] in the case where a fault occurs in the flexible HVDC power transmission system or power emergency regulation is provided, determining whether surplus power is generated in the flexible HVDC power transmission system;

[0009] in the case where surplus power is generated in the flexible HVDC power transmission system, determining a sending end AC voltage set value of the flexible HVDC power transmission system, and adjusting the sending end AC voltage of the flexible HVDC power transmission system to the sending end AC voltage set value, so as to enable an external sending end system to enter a low voltage ride through mode.

[0010] According to some embodiments, the determination of whether surplus power is generated in the flexible HVDC power transmission system in the case where a fault occurs in the flexible HVDC power transmission system or power emergency regulation is provided comprises:

[0011] in the case where a first index of the flexible HVDC power transmission system is higher than a first threshold value, determining that surplus power is generated in the flexible HVDC power transmission system;

[0012] The first index includes one or more of a DC voltage of the HVDC power transmission system, a voltage of any one of the sub-modules in the HVDC power transmission system, and an average voltage of the sub-modules.

[0013] According to some embodiments, the determining whether the HVDC power transmission system generates surplus power in the case that the HVDC power transmission system fails or provides emergency power regulation comprises:

[0014] calculating surplus power of the HVDC power transmission system;

[0015] determining that the HVDC power transmission system generates surplus power in the case that the surplus power is greater than zero.

[0016] According to some embodiments, the calculating surplus power of the HVDC power transmission system comprises:

[0017] in the case that the first power is greater than the second power, the surplus power is a difference between the first power and the second power;

[0018] in the case that the first power is less than or equal to the second power, the surplus power is zero;

[0019] wherein the first power is a power delivered to the HVDC power transmission system by an external sending-end system before power of the HVDC power transmission system is limited or emergency power regulation is provided, the second power is a power allowed to be delivered by the HVDC power transmission system in the case that power of the HVDC power transmission system is limited or emergency power regulation is provided, and the second power does not exceed a maximum power outputtable by a receiving end of the HVDC power transmission system or an external emergency power regulation target value.

[0020] According to some embodiments, the maximum power outputtable by the receiving end of the HVDC power transmission system is:

[0021]

[0022] wherein: P invmax is the maximum power outputtable by the receiving end of the HVDC power transmission system, U inv is a voltage effective value of the receiving end of the HVDC power transmission system, I invmax is a maximum operating current allowed by an electrical device of the receiving end of the HVDC power transmission system, and I invq is a reactive current value outputtable by the receiving end of the HVDC power transmission system according to a demand of an external receiving-end system.

[0023] According to some embodiments, the determining the sending-end AC voltage setting value of the HVDC power transmission system comprises:

[0024] determining the sending-end AC voltage setting value of the HVDC power transmission system according to a low-voltage ride-through characteristic of an external sending-end system and a sending-end allowed transmission power of the HVDC power transmission system;

[0025] The low-voltage ride-through characteristic of the external sending-end system can be derived from a dynamic reactive current characteristic or an active current characteristic of the external sending-end system. The sending-end allowed transmission power is less than or equal to a sum of a flexible HVDC loss, a line loss, and a power allowed to be transmitted by the HVDC power transmission system in a case that the HVDC power transmission system is power-limited or provides emergency power regulation.

[0026] According to some embodiments, the low-voltage ride-through characteristic of the external sending-end system is derived from the dynamic reactive current characteristic, and includes:

[0027]

[0028] wherein f recu2p is the low-voltage ride-through characteristic of the external sending-end system, U rec is a sending-end AC voltage effective value of the HVDC power transmission system, I sacm is a maximum current of the wind farm during low-voltage ride-through, is the dynamic reactive current characteristic.

[0029] According to some embodiments, the low-voltage ride-through characteristic of the external sending-end system is derived from the active current characteristic, and includes:

[0030]

[0031] wherein f recu2p is the low-voltage ride-through characteristic of the external sending-end system, U rec is the sending-end AC voltage effective value of the HVDC power transmission system, is the active current characteristic.

[0032] According to some embodiments, the determining the sending-end AC voltage setting value of the HVDC power transmission system includes:

[0033] controlling a first state quantity to obtain the sending-end AC voltage setting value of the HVDC power transmission system;

[0034] The first state quantity includes at least one of an input power, a DC voltage, a voltage of any one of sub-modules in the HVDC power transmission system, and an average voltage of the sub-modules. The control mode includes at least one of a PI control, a PID control, and a PR control.

[0035] According to some embodiments, in the case that the first state quantity is input power of the HVDC power transmission system, the controlling the first state quantity to obtain the sending-end AC voltage set value of the HVDC power transmission system comprises:

[0036] switching the sending end of the HVDC power transmission system to a power control mode;

[0037] measuring input power of the HVDC power transmission system;

[0038] determining the sending-end AC voltage set value according to the input power and a sending-end allowable transmission power.

[0039] According to some embodiments, in the case that the first state quantity is DC voltage of the HVDC power transmission system, the controlling the first state quantity to obtain the sending-end AC voltage set value of the HVDC power transmission system comprises:

[0040] switching the sending end of the HVDC power transmission system to a DC voltage control mode;

[0041] measuring DC voltage of the HVDC power transmission system;

[0042] determining the sending-end AC voltage set value according to the DC voltage and a DC voltage instruction value.

[0043] According to some embodiments, in the case that the first state quantity is average voltage of each sub-module of the HVDC power transmission system, the controlling the first state quantity to obtain the sending-end AC voltage set value of the HVDC power transmission system comprises:

[0044] switching the sending end of the HVDC power transmission system to a sub-module voltage control mode;

[0045] measuring sub-module average voltage of the HVDC power transmission system;

[0046] determining the sending-end AC voltage set value according to the sub-module average voltage and a sub-module voltage instruction value.

[0047] According to some embodiments, the adjusting the sending-end AC voltage of the HVDC power transmission system to the sending-end AC voltage set value comprises:

[0048] synchronously controlling magnitudes of three-phase AC voltage amplitudes of the HVDC power transmission system, or

[0049] controlling magnitudes of the three-phase AC voltage amplitudes respectively.

[0050] According to some embodiments, the method further comprises:

[0051] in the case that the surplus power is eliminated, judging whether the HVDC power transmission system is in fault ride-through or power emergency regulation completion;

[0052] In the case that the fault ride-through or the power emergency regulation of the flexible DC power transmission system is completed, the AC voltage of the sending end is adjusted from the sending end AC voltage setting value to the voltage value before the adjustment.

[0053] According to a second aspect of the present application, a control device for surplus power of a flexible DC power transmission system is provided, and the control device comprises:

[0054] a fault judging unit, configured to judge whether a fault occurs in the flexible DC power transmission system or power emergency regulation is provided, and in the case that the fault occurs in the flexible DC power transmission system or the power emergency regulation is provided, judge whether surplus power is generated in the flexible DC power transmission system;

[0055] an adjusting unit, configured to, in the case that the surplus power is generated in the flexible DC power transmission system, determine a sending end AC voltage setting value of the flexible DC power transmission system, and adjust the sending end AC voltage of the flexible DC power transmission system to the sending end AC voltage setting value, so that an external sending end system enters a low voltage ride-through mode.

[0056] According to a third aspect of the present application, an electronic device is provided, and the electronic device comprises:

[0057] a processor; and

[0058] a memory, which stores computer instructions, and when the computer instructions are executed by the processor, the processor executes the method of any one of the first aspect.

[0059] According to a fourth aspect of the present application, a non-transitory computer storage medium is provided, which stores a computer program, and when the computer program is executed by a plurality of processors, the processors execute the method of any one of the first aspect.

[0060] The present application provides a control method and device for surplus power of a flexible DC power transmission system, and an electronic device, when a fault or emergency power regulation occurs, the flexible DC power transmission system actively adjusts the AC voltage of a sending end converter station, and assists a power generation end to reduce its own power output, without the need of installing a DC energy consumption device on the high voltage DC side to complete the fault ride-through or the emergency power regulation, thereby greatly reducing the investment and maintenance cost of the flexible DC power transmission system.

[0061] It should be understood that the foregoing general description and the following detailed description are only examples, and are not limiting to the present application. BRIEF DESCRIPTION OF DRAWINGS

[0062] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[0063] Figure 1 A schematic diagram of a flexible HVDC transmission system according to an example embodiment is shown;

[0064] Figure 2 A method of controlling a surplus of HVDC power in a flexible HVDC transmission system according to an example embodiment is shown;

[0065] Figure 3 A schematic diagram of a control device for controlling a surplus of HVDC power in a flexible HVDC transmission system according to an example embodiment is shown;

[0066] Figure 4 A structural diagram of an electronic device is shown. DETAILED DESCRIPTION

[0067] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings; however, the example embodiments can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the several views and embodiments. Like components will not be described repeatedly with like reference numerals.

[0068] The described features, structures, or characteristics can be combined in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, methods, devices, implementations, materials, and operations are not shown or described in detail.

[0069] The flow diagrams shown in the various figures, which consist of blocks representing operations / acts, are merely illustrative and not necessarily the complete set of operations / acts required by the described implementations. For example, one or more of the illustrated operations / acts can be combined or partitioned into smaller operations / acts, and other operations / acts can be added or removed. In this manner, the order and / or specific arrangement of operations / acts can depend on the implementation.

[0070] The terms "first", "second", third", "fourth" etc. that are used in the description and in the claims of the present specification are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and are not intended to limit the examples to a given embodiment or implementation. Furthermore, the terms "comprise", "comprising", "include", "including", and the like are to be construed in a non-exclusive manner when employed in the description and in the claims of the present specification, unless otherwise noted. For example, the phrases "comprising", "including", and the like, when used in the specification and / or claims, should not be construed as meaning that the described steps, elements or components are the only ones that can be employed in the implementations; on the contrary, not all of the steps, elements or components described in the specification and / or claims are required, and other steps, elements or components can be employed in the implementations. It is also to be understood that the terminology used herein is for the purpose of describing the example embodiments only and is not intended to be limiting; thus, the scope of the present disclosure should be governed by the claims.

[0071] Those skilled in the art can understand that the drawings are only schematic views of the example embodiments, and the modules or flows in the drawings are not necessarily essential for implementing the present application, and therefore cannot be used to limit the protection scope of the present application.

[0072] Figure 1 A schematic diagram of a flexible HVDC transmission system according to an example embodiment is shown.

[0073] As shown in Figure 1 , the flexible HVDC transmission system includes an external sending-end system 101, a flexible HVDC transmission system 201, and an external receiving-end system 301, wherein the flexible HVDC transmission system 201 includes a sending end 2011 and a receiving end 2012. The sending end 2011 receives AC power input from the external sending-end system 101, converts the AC power into DC power, and transmits the DC power to the receiving end 2012. The receiving end 2012 converts the DC power into AC power, and outputs the AC power to the external receiving-end system 301.

[0074] According to some embodiments, the external sending-end system 101 includes a pure new energy system or a new energy-containing sending-end system, wherein the new energy system includes, for example, a wind power system, a photovoltaic system, or a wind-solar hybrid system; the new energy-containing sending-end system includes a bundled system composed of wind power and conventional power sources or energy storage systems, a bundled system composed of photovoltaic and conventional power sources or energy storage systems, or a bundled system composed of wind-solar hybrid and conventional power sources or energy storage systems; and the conventional power sources include thermal power units and hydroelectric power units; and the energy storage systems include chemical energy storage, compressed air energy storage systems, pumped storage, flywheel, and other rotational energy storage systems.

[0075] Figure 2 A method for controlling surplus power in a flexible HVDC transmission system in a flexible HVDC transmission system according to an example embodiment is shown.

[0076] S1, determining whether a fault occurs in the flexible HVDC transmission system or power emergency regulation is required.

[0077] According to the example embodiment, in the case where the flexible HVDC transmission system suffers from a fault, resulting in limited transmission power of the flexible HVDC transmission system 201 or the external need for power emergency regulation of the flexible HVDC transmission system 201, go to S2.

[0078] S2, determining whether surplus power is generated in the flexible HVDC transmission system.

[0079] According to the example embodiment, the flexible HVDC transmission system 201 determines the power surplus state of itself in real time during operation.

[0080] According to some embodiments, in the event of a fault in the flexible DC transmission system or the provision of emergency power regulation, and after the flexible DC transmission system 201 generates surplus power, the indicators of the flexible DC transmission system will change. It can be determined whether a power surplus occurs by checking whether the corresponding indicator is higher than the corresponding threshold. In the case of surplus power generated by the flexible DC transmission system, the process proceeds to S3.

[0081] According to some embodiments, the indicators include one or more of the following: the DC voltage of the flexible DC transmission system 201, the voltage of any submodule in the flexible DC transmission system 201, and the average voltage of the submodules.

[0082] According to some exemplary embodiments, if the DC voltage of the flexible DC transmission system 201 rises to a corresponding threshold, or if the voltage of any sub-module in the flexible DC transmission system 201 or the average voltage of all sub-modules exceeds the corresponding threshold, it is determined that the flexible DC transmission system 201 generates surplus power, and the process proceeds to S3.

[0083] According to the example embodiment, the surplus power P can also be obtained by calculation. spls In the surplus power P spls When the value is greater than zero, it is determined that the flexible DC transmission system 201 generates surplus power:

[0084]

[0085] In P src0 Greater than P invalo In the case of surplus power P spls For P src0 With P invalo The difference; in P src0 Less than or equal to P invalo In the case of surplus power P spls It is zero.

[0086] Among them, P src0 Before the power of the flexible DC transmission system 201 is limited or before emergency power regulation is provided, the power P transmitted from the external sending-end system 101 to the flexible DC transmission system 201 is... invalo The power that the flexible DC transmission system 201 is allowed to transmit in the event of power limitation or emergency power regulation.

[0087] According to the example embodiment, P invalo The maximum power P that can be output from the receiving end 2012 of the flexible DC transmission system 201 shall not exceed invmax Or the target value of external emergency power regulation P epc .

[0088] According to some embodiments, the maximum power that the receiving end 2012 of the flexible DC transmission system 201 can output is:

[0089]

[0090] P invmax is the maximum power that the receiving end 2012 of the HVDC power transmission system 201 can output, U inv is the voltage effective value of the receiving end 2012 of the HVDC power transmission system, I invmax is the maximum operating current allowed by the electrical equipment of the receiving end 2012 of the HVDC power transmission system 201, generally 1.0-10.0 times the rated current; I invq is the reactive current value that the receiving end 2012 of the HVDC power transmission system 201 sends out according to the demand of the external receiving end system 301.

[0091] S3, determining the sending end AC voltage setting value of the HVDC power transmission system, and adjusting the sending end AC voltage of the HVDC power transmission system to the sending end AC voltage setting value.

[0092] According to the example embodiment, when the HVDC power transmission system 201 has surplus power, the flexible HVDC transmission system can force the external sending end system 301 to enter the low-voltage current limiting mode by adjusting the sending end 2011 AC voltage to the sending end AC voltage setting value, thereby limiting the power input to the receiving end 2012 of the HVDC power transmission system 201 from the external sending end system 101, reducing the active power transmission of the sending end 2011, thereby eliminating the surplus power of the HVDC power transmission system 201, and going to S4.

[0093] According to some embodiments, the sending end 2011 AC voltage setting value U recset may be obtained by direct calculation, or by controlling the state quantity capable of reflecting the power surplus state, including at least one of the input power of the HVDC power transmission system 201, the DC voltage, the voltage of any one sub-module in the HVDC power transmission system 201, and the average voltage of each sub-module; the control mode used includes at least one of PI control, PID control and PR control.

[0094] According to some embodiments, the sending end 2011 AC voltage setting value U recset is obtained by direct calculation: according to the low-voltage ride-through characteristics of the external sending end system 101 and the sending end allowed power transmission P rec_targ of the HVDC power transmission system 201, the sending end AC voltage setting value U recset is determined:

[0095] P rec_targ = f recu2p (U recset )

[0096] Wherein, the sending end allowed power transmission P rec_targ is less than or equal to the flexible HVDC loss P conloss , the line loss P linelossand in the case of power limitation of the HVDC power transmission system 201 or emergency power regulation, the HVDC power transmission system 201 allows the power P invalo to be delivered

[0097] P rec_targ ≤P invalo +P conloss +P lineloss

[0098] According to some embodiments, P conloss and P lineloss may be all or partially ignored, P rec_targ =P invalo .

[0099] According to some embodiments, the sending end AC voltage set value U recset is to be adapted to the characteristics of the external receiving end system 301; the present application is described by taking a wind farm as an example, and other energy system embodiments or implementation manners thought of by those skilled in the art on the basis of these embodiments also belong to the scope covered by the present application. In the present application, the voltage on the wind turbine side is required to be greater than or equal to the continuous ride-through voltage specified in the wind farm access power system technology.

[0100] According to some embodiments, the active power characteristic f recu2p of the wind farm during low-voltage ride-through can be derived through the dynamic reactive current characteristic of the wind farm, can be derived through the active current characteristic of the wind farm , or directly obtained from the manufacturer or relevant experimental data.

[0101] According to some embodiments, the active power characteristic f recu2p of the wind farm during low-voltage ride-through is derived through the dynamic reactive current characteristic of the wind farm as follows:

[0102] When the voltage satisfies 0.2U recrate ≤U rec ≤0.9U recrate , the dynamic reactive current characteristic of the wind farm is :

[0103]

[0104] wherein U recrate is the sending end AC voltage rated value of the HVDC power transmission system 201, U rec is the sending end AC voltage effective value of the HVDC power transmission system 201, I sacq0 is the reactive current before entering the low-voltage ride-through mode, K1 is the dynamic reactive current proportional coefficient, and I sN is the rated current of the wind farm.

[0105] According to the dynamic reactive current characteristic of the wind farm deriving an active current characteristic f of the wind farm during low voltage ride through recu2p :

[0106]

[0107] wherein I sacm is the maximum current of the wind farm during low voltage ride through, I sacm = 1.1 I sN , I sN is the rated current of the wind farm.

[0108] According to some embodiments, the active current characteristic f of the wind farm is derived by the active current characteristic f is derived by

[0109]

[0110] According to some embodiments, in the case that the state variable is the input power of the flexible DC transmission system 201, when power surplus occurs, the sending end 2011 of the flexible DC transmission system 201 is switched to the power control mode; the input power of the flexible DC transmission system 201 is measured; the sending end AC voltage set value U recset is determined according to the input power and the sending end allowed transmission power; the sending end real-time measured input power P src is controlled to the sending end allowed transmission power P rec_targ , and the sending end AC voltage is controlled to the set value U recset . The sending end AC voltage set value U recset of the present embodiment is controlled in the form of PI control, but is not limited thereto:

[0111]

[0112] wherein U recrate is the sending end AC voltage rated value of the flexible DC transmission system 201, K p1 is the proportional adjustment coefficient, K i1 is the integral adjustment coefficient, is the integrator operator.

[0113] According to some embodiments, in the case that the state variable is the DC voltage of the flexible DC transmission system 201, when power surplus occurs, the sending end 2011 of the flexible DC transmission system 201 is switched to the DC voltage control mode; the DC voltage of the flexible DC transmission system 201 is measured; the sending end AC voltage set value U recset is determined according to the DC voltage and the DC voltage instruction value; the flexible DC transmission system 201 real-time measured DC voltage U dc is controlled to the DC voltage instruction value U dfrset , and the sending end AC voltage is controlled to the sending end AC voltage set value U recsetThis embodiment controls the AC voltage setting value U at the sending end. recset Taking PID control as an example, but not limited to this:

[0114]

[0115] Among them, K p2 K is the proportional adjustment coefficient. i2 K is the integral adjustment coefficient. d2 The differential adjustment coefficient is... This is the integrator operator.

[0116] According to some embodiments, when the state variable is the average voltage of each submodule of the flexible DC transmission system 201, and a power surplus occurs, the sending end 2011 of the flexible DC transmission system 201 is switched to submodule voltage control mode; the average voltage of the submodules of the flexible DC transmission system 201 is measured; and the sending end AC voltage setpoint U is determined based on the average submodule voltage and the submodule voltage command value. recset The average voltage U of the real-time measurement submodule of the flexible DC transmission system 201 smavg And control it to the submodule voltage command value U smfrset And control the AC voltage at the sending end to the set value U at the sending end. recset This embodiment controls the AC voltage setting value U at the sending end. recset This example uses PR (Public Relations) control, but it is not a limitation:

[0117]

[0118] Where: K p K r ω c For controller parameters, For the integrator operator, ω0 = 314 rad / s.

[0119] According to some embodiments, adjusting the sending-end AC voltage of the flexible DC transmission system 201 to the sending-end AC voltage set value includes: synchronously controlling the magnitude of the three-phase AC voltage amplitude of the flexible DC transmission system, or separately controlling the magnitude of the three-phase AC voltage amplitude to achieve adjustment of the effective value of the AC voltage.

[0120] S4 determines whether the flexible DC transmission system has completed fault ride-through or emergency power regulation.

[0121] According to the example embodiment, if the fault ride-through or emergency power regulation of the flexible DC transmission system is completed, the process proceeds to S5; otherwise, it proceeds to S2.

[0122] S5 adjusts the AC voltage at the sending end from the set value to the value before adjustment.

[0123] The application provides a control method for surplus power of a flexible HVDC power transmission system. When a fault occurs or emergency power regulation is needed, the HVDC power transmission system actively regulates the AC voltage of the sending end converter station to assist the power generation end to reduce its own power output. The fault ride-through or emergency power regulation can be completed without installing a DC energy consumption device on the HVDC side, thereby greatly reducing the investment and maintenance cost of the flexible HVDC power transmission system.

[0124] Figure 3 A control device for surplus power of a flexible HVDC power transmission system is shown in the schematic diagram of an exemplary embodiment.

[0125] As shown in Figure 3 , the control device comprises:

[0126] A fault judging unit 401 is configured to judge whether a fault occurs in the HVDC power transmission system or power emergency regulation is needed, and to judge whether surplus power is generated in the HVDC power transmission system according to the surplus power value provided by the calculating unit 404 or the index provided by the measuring unit 403 when the flexible HVDC transmission system is subjected to a fault leading to limited power transmission of the HVDC power transmission system or external power emergency regulation is needed.

[0127] According to some embodiments, when a fault occurs in the HVDC power transmission system or power emergency regulation is needed, and surplus power is generated in the HVDC power transmission system, the index of the HVDC power transmission system changes, and the fault judging unit 401 can judge whether the power surplus occurs by judging whether the corresponding index provided by the measuring unit 403 is higher than the corresponding threshold value.

[0128] According to some embodiments, the index comprises one or more of the DC voltage of the HVDC power transmission system, the voltage of any one of the sub-modules in the HVDC power transmission system and the average voltage of the sub-modules.

[0129] According to the exemplary embodiment, when the DC voltage of the HVDC power transmission system rises to the corresponding threshold value, or the voltage of any one of the sub-modules in the HVDC power transmission system or the average voltage of the sub-modules exceeds the corresponding threshold value, the fault judging unit 401 determines that the HVDC power transmission system 201 generates surplus power.

[0130] According to some embodiments, the surplus power P spls can also be obtained by calculation. The calculating unit 404 is configured to calculate the surplus power of the HVDC power transmission system and send it to the fault judging unit 401. When the surplus power is greater than zero, the fault judging unit 401 determines that the HVDC power transmission system 201 generates surplus power.

[0131] According to an example embodiment, the measurement unit 403 is further configured to acquire a state quantity, the state quantity comprising input power of the HVDC power transmission system, DC voltage of the HVDC power transmission system, voltage of any one sub-module in the HVDC power transmission system, or average voltage of each sub-module.

[0132] According to an example embodiment, the calculation unit 404 is further configured to calculate or directly calculate the sending-end AC voltage set value of the HVDC power transmission system according to the state quantity.

[0133] According to an example embodiment, the adjustment unit 402 is configured to, in the case that the HVDC power transmission system generates surplus power, determine the sending-end AC voltage set value of the HVDC power transmission system provided by the calculation unit 404, and adjust the sending-end AC voltage of the HVDC power transmission system to the sending-end AC voltage set value so as to make the external sending-end system enter a low-voltage ride-through mode.

[0134] According to some embodiments, the control device further comprises a control mode switching unit 405 configured to, in the case that the calculation unit 404 calculates the sending-end AC voltage set value of the HVDC power transmission system according to the state quantity, switch the corresponding control mode of the sending end of the HVDC power transmission system.

[0135] According to some embodiments, in the case that the state quantity is input power of the HVDC power transmission system, the control mode switching unit 405 switches the sending end of the HVDC power transmission system to a power control mode, the measurement unit 403 measures the input power of the HVDC power transmission system, the calculation unit 404 calculates the sending-end AC voltage set value according to the input power and sending-end allowable transmission power, and the adjustment unit 402 adjusts the sending-end input power to control it to the sending-end allowable transmission power and controls the sending-end AC voltage to the sending-end AC voltage set value.

[0136] According to an example embodiment, the control method adopted by the adjustment unit in the present application comprises at least one of PI control, PID control and PR control.

[0137] According to some embodiments, in the case that the state quantity is DC voltage of the HVDC power transmission system, the control mode switching unit 405 switches the sending end of the HVDC power transmission system to a DC voltage control mode, the measurement unit 403 measures the DC voltage of the HVDC power transmission system, the calculation unit 404 calculates the sending-end AC voltage set value according to the DC voltage and a DC voltage instruction value, and the adjustment unit 402 adjusts the DC voltage to control it to the DC voltage instruction value and controls the sending-end AC voltage to the sending-end AC voltage set value.

[0138] According to some embodiments, in the case that the state quantity is a DC voltage of the HVDC power transmission system, the control mode switching unit 405 switches the sending end of the HVDC power transmission system 201 to the submodule voltage control mode; the measurement unit 403 measures the average voltage of the submodule of the HVDC power transmission system 201; the calculation unit 404 determines the sending end AC voltage set value according to the average voltage of the submodule and the submodule voltage instruction value; and the adjustment unit 402 adjusts the average voltage of the submodule to the submodule voltage instruction value and controls the sending end AC voltage to the sending end AC voltage set value.

[0139] According to some embodiments, the adjustment unit 402 adjusts the sending end AC voltage of the HVDC power transmission system to the sending end AC voltage set value, including: synchronously controlling the size of the three-phase AC voltage amplitude of the HVDC power transmission system or respectively controlling the size of the three-phase AC voltage amplitude to realize the adjustment of the effective value of the AC voltage.

[0140] According to the example embodiments, the fault judgment unit 401 is further configured to judge whether the HVDC power transmission system is in the fault ride-through or the power emergency regulation is completed in the case that the surplus power is eliminated; and the adjustment unit 402 is further configured to adjust the sending end AC voltage from the sending end AC voltage set value to the voltage value before the adjustment in the case that the HVDC power transmission system is in the fault ride-through or the power emergency regulation is completed.

[0141] Figure 4 A structural diagram of an electronic device provided by the present application is shown.

[0142] Referring to Figure 4 , Figure 4 An electronic device is provided, including a processor and a memory. The memory stores computer instructions, which, when executed by the processor, cause the processor to execute the computer instructions to implement the method and detailed solutions shown in Figure 2 .

[0143] It should be understood that the above-mentioned device embodiments are only illustrative, and the device disclosed by the present application can also be implemented in other ways. For example, the division of the units / modules in the above-mentioned embodiments is only a logical functional division, and another division mode can be used in actual implementation. For example, multiple units / modules or components can be combined, or can be integrated into another system, or some features can be ignored or not executed.

[0144] In addition, unless specifically stated, each functional unit / module in each embodiment of the present application can be integrated in one unit / module, or each unit / module can exist physically, or two or more units / modules can be integrated together. The above-mentioned integrated unit / module can be realized in the form of hardware or in the form of a software program module.

[0145] The integrated units / modules, if implemented in the form of hardware, can be digital circuits, analog circuits, etc. The physical implementation of the hardware structure includes, but is not limited to, transistors, memristors, etc. Unless otherwise specified, the processor or chip can be any appropriate hardware processor, such as a CPU, a GPU, an FPGA, a DSP, an ASIC, etc. Unless otherwise specified, the on-chip cache, off-chip memory, storage can be any appropriate magnetic storage medium or magneto-optical storage medium, such as resistive random access memory (RRAM), dynamic random access memory (DRAM), static random access memory (SRAM), enhanced dynamic random access memory (EDRAM), high-bandwidth memory (HBM), hybrid memory cube (HMC), etc.

[0146] If the integrated units / modules are implemented in the form of software program modules and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for making a computer device (which can be a personal computer, a server or a network device, etc.) execute all or part of the steps of the method described in various embodiments of the present disclosure. The aforementioned storage medium includes: a U disk, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk, and various program code storage media.

[0147] The embodiments of the present application also provide a non-transitory computer storage medium storing a computer program, which, when executed by a plurality of processors, causes the processors to perform the method and detailed solutions shown in the embodiments of the present application. Figure 2 The embodiments of the present application also provide a non-transitory computer storage medium storing a computer program, which, when executed by a plurality of processors, causes the processors to perform the method and detailed solutions shown in the embodiments of the present application.

[0148] It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. On the contrary, based on the teachings of the disclosure, these principles can be applied to many other embodiments.

[0149] Furthermore, it is noted that the aforementioned figures are only schematic representations of processes included in the method according to the exemplary embodiments of the present application, and are not intended to limit the present application. It is readily appreciated that the processes depicted in the aforementioned figures do not necessarily indicate or imply the timing of the processes. Additionally, it is readily appreciated that the processes can be executed in a synchronous or asynchronous manner, for example, in multiple modules.

[0150] The exemplary embodiments of the present application are specifically shown and described above. It is to be understood that the present application is not limited to the detailed construction, arrangements, or implementation methods described herein; on the contrary, the present application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for controlling the power surplus of flexible DC transmission in a flexible DC transmission system, characterized in that, The control method includes: Determine whether the flexible DC transmission system has malfunctioned or needs to provide emergency power regulation; In the event of a fault in the flexible DC transmission system or the provision of emergency power regulation, determine whether the flexible DC transmission system generates surplus power; When the flexible DC transmission system generates surplus power, determining the sending-end AC voltage setpoint of the flexible DC transmission system includes: The AC voltage setting value of the sending end is determined based on the low-voltage ride-through characteristics of the external sending end system and the allowable transmission power of the sending end of the flexible DC transmission system. The low-voltage ride-through characteristics of the external sending-end system can be derived from its dynamic reactive current characteristics or active current characteristics, including: The low-voltage ride-through characteristics of the external sending-end system are derived from the dynamic reactive current characteristics of the external sending-end system, including: The low-voltage ride-through characteristics of the external sending-end system are derived from the active current characteristics, including: in, For the low-voltage ride-through characteristics of the external sending-end system, The effective value of the AC voltage at the sending end of the flexible DC transmission system. This represents the maximum current in the wind farm during low-voltage ride-through. For dynamic reactive current characteristics, The active current characteristic is described above. The power that the sending end is allowed to transmit is less than or equal to the sum of the flexible DC loss, the line loss, and the power that the flexible DC transmission system is allowed to transmit when the power of the flexible DC transmission system is limited or when emergency power regulation is provided; Adjust the AC voltage at the sending end of the flexible DC transmission system to the set value of the AC voltage at the sending end, so that the external sending end system enters the low-voltage ride-through mode.

2. The control method as described in claim 1, characterized in that, In the event of a fault in the flexible DC transmission system or the provision of emergency power regulation, determining whether the flexible DC transmission system generates surplus power includes: If a first indicator of the flexible DC transmission system is higher than a first threshold, it is determined that the flexible DC transmission system generates surplus power. The first indicator includes one or more of the following: the DC voltage of the flexible DC transmission system, the voltage of any submodule in the flexible DC transmission system, and the average voltage of each submodule.

3. The control method as described in claim 1, characterized in that, In the event of a fault in the flexible DC transmission system or the provision of emergency power regulation, determining whether the flexible DC transmission system generates surplus power includes: Calculate the surplus power of the flexible DC transmission system; When the surplus power is greater than zero, it is determined that the flexible DC transmission system generates surplus power.

4. The control method as described in claim 3, characterized in that, The calculation of the surplus power of the flexible DC transmission system includes: When the first power is greater than the second power, the surplus power is the difference between the first power and the second power; When the first power is less than or equal to the second power, the surplus power is zero; Wherein, the first power is the power transmitted from the external sending-end system to the flexible DC transmission system before the power of the flexible DC transmission system is limited or before emergency power regulation is provided; the second power is the power that the flexible DC transmission system is allowed to transmit when the power of the flexible DC transmission system is limited or before emergency power regulation is provided; the second power does not exceed the maximum output power of the receiving end of the flexible DC transmission system or the target value of external emergency power regulation.

5. The control method as described in claim 4, characterized in that, The maximum power that the receiving end of the flexible DC transmission system can output is: in: This represents the maximum output power that the receiving end of the flexible DC transmission system can achieve. The effective value of the receiving-end voltage of the flexible DC transmission system is given. This refers to the maximum permissible operating current of the receiving-end electrical equipment in the flexible DC transmission system. The reactive current value generated by the receiving end of the flexible DC transmission system according to the needs of the external receiving end system.

6. The control method as described in claim 1, characterized in that, Determining the sending-end AC voltage setpoint of the flexible DC transmission system includes: Control the first state variable to obtain the AC voltage setpoint at the sending end of the flexible DC transmission system; The first state quantity includes at least one of the input power of the flexible DC transmission system, DC voltage, voltage of any submodule in the flexible DC transmission system, and average voltage of each submodule; the control method used includes at least one of PI control, PID control, and PR control.

7. The control method as described in claim 6, characterized in that, When the first state variable is the input power of the flexible DC transmission system, controlling the first state variable to obtain the sending-end AC voltage setpoint of the flexible DC transmission system includes: Switch the sending end of the flexible DC transmission system to power control mode; Measure the input power of the flexible DC transmission system; The AC voltage setting value of the sending end is determined based on the input power and the allowable power to be transmitted at the sending end.

8. The control method as described in claim 6, characterized in that, When the first state variable is the DC voltage of the flexible DC transmission system, controlling the first state variable to obtain the sending-end AC voltage setpoint of the flexible DC transmission system includes: Switch the sending end of the flexible DC transmission system to DC voltage control mode; Measure the DC voltage of the flexible DC transmission system; The AC voltage setting value at the sending end is determined based on the DC voltage and the DC voltage command value.

9. The control method as described in claim 6, characterized in that, When the first state variable is the average voltage of each submodule of the flexible DC transmission system, controlling the first state variable to obtain the sending-end AC voltage setpoint of the flexible DC transmission system includes: Switch the sending end of the flexible DC transmission system to submodule voltage control mode; Measure the average voltage of the sub-modules of the flexible DC transmission system; The AC voltage setting value of the sending end is determined based on the average voltage of the submodule and the voltage command value of the submodule.

10. The control method as described in claim 1, characterized in that, Adjusting the sending-end AC voltage of the flexible DC transmission system to the set value of the sending-end AC voltage includes: The magnitude of the three-phase AC voltage amplitude of the flexible DC transmission system is synchronously controlled, or The magnitudes of the three-phase AC voltages are controlled respectively.

11. The control method as described in claim 1, characterized in that, Also includes: In the event that the surplus power is eliminated, it is determined whether the flexible DC transmission system has undergone fault ride-through or emergency power regulation has been completed. In the event of a fault ride-through or emergency power regulation completed in the flexible DC transmission system, the AC voltage at the sending end will be adjusted from the set value to the value before regulation.

12. A control device for the power surplus of flexible DC transmission in a flexible DC transmission system, characterized in that, The control device is used to perform the control method as described in any one of claims 1-11, the control device comprising: The fault determination unit is used to determine whether the flexible DC transmission system has experienced a fault or provides emergency power regulation; and in the event that the flexible DC transmission system has experienced a fault or provides emergency power regulation, to determine whether the flexible DC transmission system generates surplus power. The regulating unit is used to determine the sending-end AC voltage setpoint of the flexible DC transmission system when the flexible DC transmission system generates surplus power, and to regulate the sending-end AC voltage of the flexible DC transmission system to the sending-end AC voltage setpoint so that the external sending-end system enters the low-voltage ride-through mode.

13. An electronic device, characterized in that, include: processor; as well as A memory storing computer instructions that, when executed by the processor, cause the processor to perform the method according to any one of claims 1-11.

14. A non-transitory computer storage medium storing a computer program that, when executed by a plurality of processors, causes the processors to perform the method of any one of claims 1-11.

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