CN115912450A - Flexible direct-current power transmission system control method and device based on virtual synchronous control - Google Patents
Flexible direct-current power transmission system control method and device based on virtual synchronous control Download PDFInfo
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Abstract
The invention belongs to the technical field of flexible direct current transmission, and particularly relates to a control method and device of a flexible direct current transmission system based on virtual synchronous control. Firstly, calculating the virtual synchronous voltage of the converter according to the virtual rotor angle of the converter and the virtual internal potential of the converter; then when the system runs in a fault, calculating to obtain a three-phase voltage reference value of the current converter through virtual circuit control and current inner loop control; finally, calculating the reference voltage of each bridge arm of the converter according to the three-phase voltage reference value of the converter and the modulation relation of the bridge arm voltage of the converter; and controlling the converter by using the obtained reference voltage of each bridge arm. The invention completes the regulation of the flexible direct current transmission control system and improves the transient and steady state active and reactive support capability and the fault resistance capability of the flexible direct current converter to the alternating current system.
Description
Technical Field
The invention belongs to the technical field of flexible direct current transmission, and particularly relates to a control method and device of a flexible direct current transmission system based on virtual synchronous control.
Background
Under the aim of 'double carbon', the construction of a novel power system taking new energy as a main body is accelerated, and the method is a necessary way for supporting 'carbon emission reduction' of the whole society in the power industry. Along with the construction of a novel power system, the installed proportion of new energy is gradually increased.
The stable operation of the power system is not separated from the inertia support of the synchronous power supply. Compared with a synchronous power generation system, the new energy power generation system basically has no inertia supporting capacity. With the increase of the proportion of new energy installation, the system inertia is continuously reduced, and the challenge is brought to the safe and stable operation of the power grid. Compared with a new energy power generation system, the flexible direct current power transmission system is larger in capacity and higher in controllability, and has the supporting capacity of providing larger virtual inertia for the system through technical transformation.
Meanwhile, the existing flexible direct current transmission control system is based on classical current vector P/Q control, and has the following problems: the system is less involved in active regulation of the power grid during steady-state operation, and the transient reactive power supporting capability is limited and does not play a role in supporting the power grid during the fault of the alternating current power grid; when the high-capacity flexible direct current converter is connected to a power grid, the frequency modulation capability of a system is weakened, and the frequency can fluctuate greatly and even collapse when the power is stepped; when the alternating current power grid is weak, the system instability is easily caused, the risk can be avoided only through locking, and the system operation reliability is reduced; when large-scale new forms of energy are accessed through flexible direct current, high-frequency oscillation, low-frequency oscillation, subsynchronous resonance risk increase. Due to the problems, the flexible direct current transmission system cannot exert the supporting capacity on a novel power system.
Disclosure of Invention
The invention aims to provide a method and a device for controlling a flexible direct-current power transmission system based on virtual synchronous control, which are used for solving the problem that the direct-current power transmission system cannot support a power system due to the adoption of the method in the prior art.
In order to solve the technical problem, the invention provides a flexible direct current transmission system control method based on virtual synchronous control, which comprises the following steps:
1) Calculating to obtain a converter virtual rotor angle theta through virtual rotor control; calculating to obtain the virtual internal potential E of the converter through virtual excitation control q (ii) a According to the converter virtual rotor angle theta and the converter virtual internal potential E q Calculating the virtual synchronous voltage U of the converter abcref ；
2) When the system is in fault operation, the virtual circuit controls the system to virtually synchronize the voltage U according to the current converter abcref Calculating to obtain an active current reference value and a reactive current reference value required by current inner loop control; then, respectively and correspondingly carrying out active current inner loop control and reactive current inner loop control according to the active current reference value and the reactive current reference value, and calculating to obtain a three-phase voltage reference value of the current converter;
3) Calculating reference voltage of each bridge arm of the converter according to the three-phase voltage reference value of the converter and the modulation relation of the bridge arm voltage of the converter; and controlling the converter by using the obtained reference voltage of each bridge arm.
The beneficial effects are as follows: the invention applies the virtual synchronous generator technology to a flexible direct current transmission system, under the condition of system fault operation, firstly, virtual rotor angle and virtual inner potential are respectively obtained by utilizing virtual rotor control and virtual excitation control, further, virtual synchronous voltage is obtained, then, fault current is limited by utilizing a current control link through virtual circuit control and current inner ring control, so that a current converter is protected from being damaged, a three-phase voltage reference value of the current converter is obtained, finally, the reference voltage of each bridge arm is calculated, the current converter in the system is controlled by utilizing the bridge arm reference voltage calculated by the method, the regulation of the flexible direct current transmission control system is completed, and the transient steady state active and reactive support capability and the fault resisting capability of the flexible direct current converter to an alternating current system are improved.
Further, the control mode of the virtual rotor control in the step 1) includes constant direct-current voltage control and constant active power control, and an active power feedback value is obtained by using a network side voltage and a network side current during the constant active power control.
The beneficial effects are as follows: according to different conditions, any one of constant direct-current voltage control and constant active power control can be selected to complete virtual rotor control, and the control means is flexible.
Further, the control mode of the virtual excitation control in the step 1) includes constant alternating voltage control and constant reactive power control, and a reactive power feedback value is obtained by using network side voltage and network side current during the constant reactive power control.
The beneficial effects are as follows: according to different conditions, any one of the constant alternating voltage control and the constant reactive power control can be selected to complete the virtual rotor control, and the control means is flexible.
Further, the converter virtual synchronous voltage U in the step 1) abcref The calculation formula of (c) is:
in the formula of U aref 、U bref And U cref Respectively, three phases of virtual synchronous voltages.
Further, if the virtual impedance of the virtual circuit in the virtual circuit control in step 2) is R + jX, the calculation formula of the active current reference value and the reactive current reference value required by the current inner loop control is as follows:
in the formula, idref and Iqref are an active current reference value and a reactive current reference value respectively; usd and Usq are dq conversion values of the network side alternating voltage respectively, and Ucd and Ucq are dq conversion values of the virtual synchronous voltage respectively; r and X are the real and imaginary parts of the virtual impedance, respectively.
Further, the following method is adopted in the step 2) to judge whether the system is in fault operation: if the amplitude Us of the alternating voltage on the network side falls or rises beyond a normal operation range, d-axis current Id in a dq conversion value of valve side current exceeds a limit amplitude, or q-axis current Iq in the dq conversion value of the valve side current exceeds the limit amplitude, judging that the system is in fault operation; otherwise, judging that the system operates without faults.
The beneficial effects are as follows: and whether the system operates in a fault or not is judged according to the alternating voltage amplitude and the alternating current of the network side, the method is simple, and the calculation efficiency is high.
Further, when the system runs without faults, the voltage U is virtually synchronized according to the converter abcref Calculating the reference voltage of each bridge arm of the converter according to the modulation relation of the bridge arm voltages of the converter; and controlling the converter by using the obtained reference voltage of each bridge arm.
Further, the obtained reference voltage of each bridge arm is sent to a valve control system through an optical fiber.
The beneficial effects are as follows: the data transmission rate and accuracy can be improved by sending the data to the valve control system through the optical fiber.
In order to solve the technical problem, the present invention further provides a flexible direct current power transmission system control device based on virtual synchronous control, which includes a memory and a processor, where the processor is configured to execute program instructions stored in the memory to implement the above-described flexible direct current power transmission system control method based on virtual synchronous control, and achieve the same beneficial effects as the method.
Drawings
Fig. 1 is a control block diagram of a flexible direct current power transmission system control method based on virtual synchronous control according to the invention;
FIG. 2 is a logic block diagram of the flexible DC power transmission system control method based on virtual synchronous control of the invention;
FIG. 3 is a flow chart of a flexible DC power transmission system control method based on virtual synchronous control according to the invention;
FIG. 4 is a control block diagram of the virtual rotor control of the present invention;
FIG. 5 is a control block diagram of the virtual excitation control of the present invention;
fig. 6 is a block diagram of a flexible dc power transmission system control device based on virtual synchronization control according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The method comprises the following steps:
in the embodiment of the method for controlling the flexible direct-current power transmission system based on the virtual synchronous control, a corresponding control block diagram is shown in fig. 1, a logic block diagram is shown in fig. 2, and a flow chart is shown in fig. 3, which specifically includes the following steps:
step one, acquiring a direct current voltage signal, a valve side current signal, a network side voltage and a current signal through an electric quantity acquisition module, and completing A/D conversion of the electric quantity signal to obtain a direct current voltage U dc Valve side current Iv abc Network side voltage U abc And net side current I abc (ii) a And using the network side voltage U abc And net side current I abc And calculating to obtain active P and reactive Q.
And step two, selecting constant direct current voltage or constant active power control according to a control method through virtual rotor control as shown in fig. 4, simulating rotor mechanical motion control of the synchronous generator, and calculating a converter virtual rotor angle theta.
Step three, finishing constant alternating voltage or constant reactive power control through virtual excitation control as shown in figure 5, simulating excitation control of the synchronous generator to obtain a converter virtual internal potential E q 。
Step four, the virtual synchronous voltage control module controls the virtual rotor angle theta and the virtual internal potential E according to the converter q Calculating the virtual synchronous voltage U of the current converter according to the following formula abcref ：
Step five, judging the alternating voltage amplitude Us and the current Idq on the network side to judge whether the system operates in a fault mode: if the amplitude Us of the alternating voltage on the network side falls or rises beyond the normal operation range, or the dq conversion values Id and Iq of the current on the valve side exceed the amplitude limit value, namely: if the system is judged to be in fault operation, executing a sixth step; otherwise, judging that the system runs without faults, and directly executing the step nine.
And step six, when the system is in fault operation, calculating an active current reference value and a reactive current reference value required by current inner loop control by using a stator reactance circuit of the analog synchronous generator through the virtual circuit control module, and executing step seven. The virtual impedance of a virtual circuit in the virtual circuit control is R + jX, and the calculation formula of the active current reference value and the reactive current reference value required by the current inner loop control is as follows:
in the formula, idref and Iqref are an active current reference value and a reactive current reference value respectively; usd and Usq are dq conversion values of the network side alternating voltage respectively, and Ucd and Ucq are dq conversion values of the virtual synchronous voltage respectively; r and X are the real and imaginary parts of the virtual impedance, respectively.
And step seven, calculating the reference value of the three-phase voltage of the current converter by using the active current and reactive current closed-loop controller of the valve side current through the current inner-loop control module, and executing the step eight.
Step eight, calculating 6 bridge arm reference voltages Uv of the current converter by utilizing a three-phase voltage reference value of the current converter and a modulation relation of the bridge arm voltage of the current converter through a current converter bridge arm reference voltage operation module abcp_ref And Uv abcn_ref And step ten is performed.
Step nine, directly obtaining the virtual synchronous voltage U of the converter in the step four through a converter bridge arm reference voltage operation module abcref And calculating the reference voltage Uv of 6 bridge arms of the converter by using the modulation relation of the bridge arm voltage of the converter abcp_ref And Uv abcn_ref And step ten is performed.
Step ten, sending the calculated 6 bridge arm reference voltages of the current converter to a valve control system through optical fibers.
The invention adopts different control strategies for the condition of system failure or not, namely: when the bridge arm is not in fault, the virtual synchronous three-phase voltage is equal to the voltage of the current converter, and the reference value of the bridge arm voltage can be directly calculated by the virtual synchronous three-phase voltage; when the converter fails, a current control link is required to be added to limit the fault current, and the required converter voltage is inversely transformed by dq after the inner loop current control, so that the converter is protected from being damaged. And when the system operates in a fault, the virtual synchronous voltage is controlled by the virtual circuit and the inner ring current to finally obtain the converter bridge arm reference voltage and send the converter bridge arm reference voltage to the valve control system, and when the system operates normally, the virtual synchronous voltage is directly converted into the converter bridge arm reference voltage and sent to the valve control system, so that the adjustment of the flexible direct current power transmission system is completed.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on a number of computer-usable storage media having computer-usable program code embodied in the media, including but not limited to disk storage, CD-ROM, optical storage, and the like.
The embodiment of the device is as follows:
an embodiment of the flexible direct-current power transmission system control device based on virtual synchronous control according to the invention is shown in fig. 6 and comprises a memory, a processor and an internal bus, wherein the processor and the memory complete mutual communication and data interaction through the internal bus. The memory comprises at least one software functional module stored in the memory, and the processor executes various functional applications and data processing by running the software programs and modules stored in the memory, so as to realize the flexible direct current power transmission system control method based on virtual synchronous control introduced in the method embodiment of the invention.
The processor can be a microprocessor MCU, a programmable logic device FPGA and other processing devices. The memory can be various memories for storing information by using an electric energy mode, such as RAM, ROM and the like; various memories for storing information by magnetic energy, such as hard disk, floppy disk, magnetic tape, magnetic core memory, bubble memory, U disk, etc.; various memories for storing information optically, such as CDs, DVDs, etc.; of course, other forms of memory are possible, such as quantum memory, graphene memory, and the like.
The specific embodiments are given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention lies in the above basic scheme, and it is obvious to those skilled in the art that no creative effort is needed to design various modified models, formulas and parameters according to the teaching of the present invention. Variations, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the invention, and still fall within the scope of the invention.
Claims (9)
1. A control method of a flexible direct current power transmission system based on virtual synchronous control is characterized by comprising the following steps:
1) Calculating to obtain a converter virtual rotor angle theta through virtual rotor control; calculating to obtain the virtual internal potential E of the converter through virtual excitation control q (ii) a According to the converter virtual rotor angle theta and the converter virtual internal potential E q Calculating the virtual synchronous voltage U of the converter abcref ；
2) When the system is in fault operation, the virtual circuit controls the system to virtually synchronize the voltage U according to the current converter abcref Calculating to obtain an active current reference value and a reactive current reference value required by current inner ring control; then, respectively and correspondingly carrying out active current inner loop control and reactive current inner loop control according to the active current reference value and the reactive current reference value, and calculating to obtain a three-phase voltage reference value of the current converter;
3) Calculating reference voltage of each bridge arm of the converter according to the three-phase voltage reference value of the converter and the modulation relation of the bridge arm voltage of the converter; and controlling the converter by using the obtained reference voltage of each bridge arm.
2. The method according to claim 1, wherein the control mode of the virtual rotor control in step 1) comprises constant direct current voltage control and constant active power control, and the active power feedback value in the constant active power control is obtained by using grid-side voltage and grid-side current.
3. The method according to claim 1, wherein the control mode of the virtual excitation control in step 1) includes constant ac voltage control and constant reactive power control, and the reactive power feedback value in the constant reactive power control is obtained by using grid-side voltage and grid-side current.
4. The flexible direct-current power transmission system control method based on virtual synchronous control according to claim 1, characterized in that the converter virtual synchronous voltage U in step 1) is abcref The calculation formula of (2) is as follows:
in the formula of U aref 、U bref And U cref Respectively, a virtual synchronous voltage of three phases.
5. The method for controlling the flexible direct current transmission system based on the virtual synchronous control according to claim 1, wherein the virtual impedance of the virtual circuit in the virtual circuit control in step 2) is R + jX, and the calculation formula of the active current reference value and the reactive current reference value required by the current inner loop control is as follows:
in the formula, idref and Iqref are an active current reference value and a reactive current reference value respectively; usd and Usq are dq conversion values of a grid side alternating voltage respectively, and Ucd and Ucq are dq conversion values of a virtual synchronous voltage respectively; r and X are the real and imaginary parts of the virtual impedance, respectively.
6. The method for controlling the flexible direct current transmission system based on the virtual synchronous control according to claim 1, wherein the following method is adopted in the step 2) to judge whether the system is in fault operation: if the amplitude Us of the alternating voltage on the network side falls or rises beyond a normal operation range, d-axis current Id in the dq conversion value of the current on the valve side exceeds a limit amplitude, or q-axis current Iq in the dq conversion value of the current on the valve side exceeds a limit amplitude, judging that the system is in fault operation; otherwise, judging that the system runs without faults.
7. The method according to any one of claims 1 to 6, wherein the method comprises, when the system is operating without a fault, determining the virtual synchronous voltage U according to the converter abcref Calculating the reference voltage of each bridge arm of the converter according to the modulation relation of the bridge arm voltages of the converter; and controlling the converter by using the obtained reference voltage of each bridge arm.
8. The method for controlling the flexible direct-current transmission system based on the virtual synchronous control according to any one of claims 1 to 6, wherein the obtained reference voltage of each bridge arm is sent to a valve control system through an optical fiber.
9. A flexible direct current power transmission system control device based on virtual synchronous control, characterized by comprising a memory and a processor, wherein the processor is used for executing program instructions stored in the memory to realize the flexible direct current power transmission system control method based on virtual synchronous control according to any one of claims 1 to 8.
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| CN117353338A (en) * | 2023-12-06 | 2024-01-05 | 广东电网有限责任公司珠海供电局 | M3C-based active support control system and device for virtual synchronous machine |
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| CN117353338A (en) * | 2023-12-06 | 2024-01-05 | 广东电网有限责任公司珠海供电局 | M3C-based active support control system and device for virtual synchronous machine |
| CN117353338B (en) * | 2023-12-06 | 2024-04-02 | 广东电网有限责任公司珠海供电局 | M3C-based active support control system and device for virtual synchronous machine |
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