CN112803440A - VSG control method, device, equipment and medium - Google Patents
VSG control method, device, equipment and medium Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The application discloses a VSG control method, a VSG control device, VSG control equipment and VSG control media, wherein the VSG control method comprises the following steps: a receiving end converter station of the multi-end direct current transmission system is equivalent to a virtual synchronous generator; establishing a calculation model of mechanical power and active power instructions of the VSG control system and frequency deviation of the access point: and introducing a high/low voltage controller for regulating the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval. According to the active power control method and device, active power can be accurately transmitted to the alternating current system according to the active instruction reference value, so that inertial support is provided for a power grid, and meanwhile, the power grid actively participates in power grid frequency regulation. And the active current can be quickly adjusted according to the deviation value of the voltage, so that the fluctuation of the direct-current voltage is reduced.
Description
Technical Field
The present disclosure relates to the field of multi-terminal dc power transmission control technologies, and in particular, to a VSG control method, apparatus, device, and medium.
Background
With the rapid development of high-power electronic devices, the multi-terminal direct current transmission (VSC-MTDC) based on a voltage source type converter becomes an effective way for offshore wind power grid connection due to the advantages of high controllability, easiness in networking, capability of supplying power to a passive network and the like. The existing flexible direct current transmission system mainly adopts a vector control technology, has high dynamic response speed and can independently control active power and reactive power. After a coastal new energy cluster and large-scale offshore wind power are differentially accessed into a power grid through a power electronic conversion device, the traditional power closed-loop control enables the flexible direct current converter station to represent a low-damping power supply with zero inertia to a system, and the system cannot respond to the frequency change like a synchronous machine. With the gradual increase of the duty ratio of the output of the distributed energy, the equivalent moment of inertia and the primary frequency modulation capability of the synchronous power grid are continuously reduced, and the operation stability of the power system is seriously threatened.
The VSC-MTDC system mainly adopts a parallel connection mode, and the key of the safe and stable operation of the system is to effectively control the voltage of a direct current bus in an allowed interval. In the prior art, the frequency of an alternating current system and the voltage of a direct current system can be coordinately controlled, but droop control has the inherent defect that power cannot be accurately controlled.
Disclosure of Invention
The embodiment of the application provides a VSG control method, a VSG control device, VSG control equipment and VSG control media, so that active power can be accurately transmitted to an alternating current system according to an active instruction reference value, inertial support is provided for a power grid, and meanwhile, the active power control method actively participates in power grid frequency adjustment. And the active current can be quickly adjusted according to the deviation value of the voltage, so that the fluctuation of the direct-current voltage is reduced.
In view of the above, a first aspect of the present application provides a VSG control method, including:
a receiving end converter station of the multi-end direct current transmission system is equivalent to a virtual synchronous generator;
establishing a calculation model of mechanical power and active power instructions of the VSG control system and frequency deviation of the access point:
Pm＝Pref+kf(f0-f)
in the formula, PmTo simulate the mechanical power of a synchronous generator, PrefFor virtual active power commands, kfIs the frequency modulation coefficient, f0-f is the frequency offset of the access point;
and introducing a high/low voltage controller for regulating the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval.
Optionally, the equivalent of the receiving-end converter station of the multi-end dc transmission system to a virtual synchronous generator includes:
and the potential of the converter is equivalent to the internal potential of the virtual synchronous generator, the inductance value of the converter reactor is equivalent to the synchronous inductance of the virtual synchronous generator, the internal resistance of the converter reactor is equivalent to the synchronous resistance of the virtual synchronous generator, and the direct-current end of the converter is equivalent to the prime motor of the virtual synchronous generator.
Optionally, the method further includes: the reactive instruction output by the VSG control system is compared with a reactive output value, a machine end reference voltage of the virtual synchronous generator is calculated, the machine end reference voltage is compared with the measured voltage of the virtual synchronous generator end, and the comparison result is input into a PI controller to obtain a virtual potential amplitude of the virtual synchronous generator, so that reactive power regulation is completed;
the calculation formula of the generator-end reference voltage of the virtual synchronous generator is as follows:
Uref＝E0+ΔE＝E0+kq(Qref-Q)
in the formula, E0Is the effective value of no-load electromotive force, k, of the virtual synchronous machineqTo adjust the coefficient of reactive power, QrefAnd Q is a reactive instruction and a reactive output value output by the VSG control system respectively.
Optionally, the introducing a high/low voltage controller is configured to adjust an active current output by the VSG control system, so that the active current value input to the ac network is kept in a preset interval, including:
when the direct current voltage is greater than the preset upper limit voltage or the direct current voltage is less than the preset lower limit voltage, the high/low voltage controller generates bias current to be superposed on active current output by the VSG control system, and the superposed active current is as follows:
in the formula udcIs a direct voltage udc_hAnd udc_lRespectively a preset upper limit voltage and a preset lower limit voltage; Δ ih，ΔilFor bias current, id_refAnd controlling the active current output by the system for the VSG.
A second aspect of the present application provides a VSG control apparatus, the apparatus comprising:
the equivalent unit is used for equivalent the receiving end converter station of the multi-end direct current transmission system into a virtual synchronous generator;
the establishing unit is used for establishing a calculation model of the mechanical power and active power instruction of the VSG control system and the frequency deviation of the access point:
Pm＝Pref+kf(f0-f)
in the formula, PmTo simulate the mechanical power of a synchronous generator, PrefFor virtual active power commands, kfIs the frequency modulation coefficient, f0-f is the frequency offset of the access point;
and the adjusting unit is used for introducing a high/low voltage controller for adjusting the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval.
Optionally, the equivalent unit is further configured to equate the potential of the converter to an internal potential of the virtual synchronous generator, equate an inductance value of the converter reactor to a synchronous inductance of the virtual synchronous generator, equate an internal resistance of the converter reactor to a synchronous resistance of the virtual synchronous generator, and equate the dc end of the converter to a prime mover of the virtual synchronous generator.
Optionally, the reactive power adjusting unit is configured to calculate a machine-side reference voltage of the virtual synchronous generator by comparing a reactive instruction output by the VSG control system with a reactive output value, compare the machine-side reference voltage with a measured voltage of the virtual synchronous generator, and input a comparison result to the PI controller to obtain a virtual potential amplitude of the virtual synchronous generator, thereby completing reactive power adjustment;
the calculation formula of the generator-end reference voltage of the virtual synchronous generator is as follows:
Uref＝E0+ΔE＝E0+kq(Qref-Q)
in the formula, E0Is the effective value of no-load electromotive force, k, of the virtual synchronous machineqTo adjust the coefficient of reactive power, QrefAnd Q is a reactive instruction and a reactive output value output by the VSG control system respectively.
Optionally, the adjusting unit is further configured to introduce a high/low voltage controller for adjusting an active current output by the VSG control system, so that the active current value input to the ac network is maintained at a preset interval, including:
when the direct current voltage is greater than the preset upper limit voltage or the direct current voltage is less than the preset lower limit voltage, the high/low voltage controller generates bias current to be superposed on active current output by the VSG control system, and the superposed active current is as follows:
in the formula udcIs a direct voltage udc_hAnd udc_lRespectively a preset upper limit voltage and a preset lower limit voltage; Δ ih，ΔilFor bias current, id_refAnd controlling the active current output by the system for the VSG.
A third aspect of the present application provides a VSG control apparatus, the apparatus comprising a processor and a memory:
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the steps of the VSG control method according to the first aspect, according to instructions in the program code.
A fourth aspect of the present application provides a computer-readable storage medium for storing program code for performing the method of the first aspect.
According to the technical scheme, the method has the following advantages:
the application provides a VSG control method, which is characterized in that a receiving end converter station of a multi-end direct-current transmission system is equivalent to a virtual synchronous generator; establishing a calculation model of mechanical power and active power instructions of the VSG control system and frequency deviation of the access point: and introducing a high/low voltage controller for regulating the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval.
The receiving end converter station of the multi-end direct current transmission system is equivalent to a virtual synchronous generator, so that the converter can show the inertia and damping action of the virtual synchronous generator; by establishing a calculation model of a mechanical power and active power instruction of a VSG control system and a frequency deviation of an access point, the converter station accurately transmits active power to an alternating current system according to an active power instruction reference value in a normal operation state, provides inertial support for a power grid and actively participates in power grid frequency adjustment. By introducing the high/low voltage controller for adjusting the active current output by the VSG control system, when the main station exits from operation due to a fault, the system can quickly respond when monitoring the voltage deviation, so that the fluctuation of the direct-current voltage is reduced.
Drawings
FIG. 1 is a method flow of one embodiment of a VSG control method of the present application;
FIG. 2 is a device configuration diagram of one embodiment of a VSG control device of the present application;
fig. 3 is an equivalent circuit diagram of a receiving end converter station and a virtual synchronous generator of a multi-terminal direct-current transmission system in an embodiment of the present application;
FIG. 4 is an equivalent circuit diagram of a power control process of the VSG control system in the embodiment of the present application;
FIG. 5 is an equivalent circuit diagram of a VSG control system in an embodiment of the present application;
fig. 6 is a schematic diagram of a VSG control system incorporating dc voltage control in an embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Fig. 1 is a flowchart of a method of an embodiment of a VSG control method according to the present application, as shown in fig. 1, where fig. 1 includes:
101. a receiving end converter station of the multi-end direct current transmission system is equivalent to a virtual synchronous generator;
it should be noted that, the PCC point in fig. 3 may be set as a reference point, and a Virtual Synchronous Generator (VSG) ac side bus voltage and a virtual synchronous generator terminal voltage may be set as E ≧ δ0The bus voltage at PCC is U < 00. A mathematical model of the converter station in the three-phase stationary coordinate system can be obtained according to kirchhoff's theorem. Namely, a mathematical model of a receiving end converter station of the multi-end direct current transmission system under a three-phase static coordinate system is as follows:
in the formula: l issAn inductance value of the converter reactor; i.e. iabcIs three-phase alternating side current; e.g. of the typeabcThe three-phase voltage is the alternating-current side three-phase voltage of the converter; u. ofabcOutputting three-phase voltage for the alternating current filter; rsThe internal resistance of the converter reactor.
In an abc three-phase coordinate system, when the loss of a converter reactor is neglected, the active power P and the reactive power Q transmitted between an alternating current network and a converter station are respectively as follows:
in the formula of UmThe effective value of the phase voltage at the PCC is obtained; e is the effective value of the alternating-current side phase voltage of the converter; xsIs the sum of the impedances between the converter station and the PCC; delta is UmAnd E.
According to the formula, the active power injected into the network can be adjusted by changing the phase angle difference delta, and the phase voltage effective value U at the PCC is changedmThe reactive power can be regulated.
The corresponding relationship between the converter station and the synchronous generator, converter potential e, will be further explained in connection with fig. 3abcCan be equivalent to the internal potential, L, of a synchronous generatorsCan be equivalent to the synchronous inductance, R of a synchronous generatorsMay be equivalent to the synchronous resistance of a synchronous generator. The DC side provides the mechanical power P of VSG in analogy to the prime movermOutput electromagnetic power at outlet is Pe。
It should be noted that the virtual synchronous generator includes a VSG body model and a control system, the body model mainly simulates the electromagnetic relationship and mechanical movement of the synchronous generator in terms of mechanism, and the control system mainly simulates the characteristics of the synchronous generator, such as active frequency modulation and reactive voltage regulation, in terms of external characteristics.
102. Establishing a calculation model of a mechanical power and active power instruction of a VSG control system and a frequency deviation of an access point;
it should be noted that, in the second-order model of the synchronous motor considering rotor inertia and damping factors, the mechanical equation and the electromagnetic equation can be respectively expressed as:
in the formula, J is the rotational inertia of the synchronous generator, kg.m 2; d is the damping coefficient of the synchronous generator; omega is the mechanical angular velocity when the pole pair number is 1, namely the electrical angular velocity, rad/s; omegaNFor a nominal angular velocity, rad/s, θ isAngular displacement of the generator rotor, rad.
In the above formula, the introduction of two coefficients, i.e. J and D, causes the converter to externally exhibit the inertia and damping effect of the synchronous generator.
The mechanical power P of the VSGmBy virtual active power command PrefAnd the system frequency deviation obtained by active droop comprises:
Pm＝Pref+kf(f0-f)
in the formula, kfIs a frequency modulation coefficient; f. of0-f is the frequency offset of the access point.
From the above equation, the active-frequency control of the VSG can provide inertia and damping for the system, and also can be based on the deviation (f) of the frequency of the access point0-f) making an active regulation response.
In a specific embodiment, the synchronous generator regulates the reactive output by regulating the excitation, and similarly, the virtual synchronous generator can regulate the terminal voltage and reactive power by regulating the virtual potential.
As shown in fig. 4, the terminal reference voltage U of the virtual synchronous generatorrefCan be expressed as:
Uref＝E0+ΔE＝E0+kq(Qref-Q)
in the formula: e0Is the effective value of no-load electromotive force, k, of the virtual synchronous machineqTo adjust the coefficient of reactive power, QrefAnd Q are the reactive command and reactive output values of the VSG, respectively.
Specifically, in order to realize the closed-loop control of the voltage, the reactive instruction output by the VSG control system is compared with the reactive output value, the machine end reference voltage of the virtual synchronous generator is calculated, the machine end reference voltage is compared with the measured voltage of the virtual synchronous generator, and the comparison result is input into the PI controller to obtain the virtual potential amplitude of the virtual synchronous generator, so that the reactive power regulation is completed.
103. And introducing a high/low voltage controller for regulating the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval.
It should be noted that, when the dc voltage is greater than the preset upper limit voltage or the dc voltage is less than the preset lower limit voltage, the high/low voltage controller generates a bias current to be superimposed on the active current output by the VSG control system, and the superimposed active current is:
in the formula udcIs a direct voltage udc_hAnd udc_lRespectively a preset upper limit voltage and a preset lower limit voltage; Δ ih，ΔilFor bias current, id_refAnd controlling the active current output by the system for the VSG.
Fig. 5 shows an equivalent circuit diagram of the VSG control system, fig. 6 shows a schematic diagram of the VSG control system combined with dc voltage control according to the present application, and fig. 6 includes a high voltage controller and a low voltage controller, which are respectively used for generating a bias current Δ i when the dc voltage is greater than a preset upper limit voltagehGenerating a bias current Δ i when the DC voltage is less than a preset lower limit voltagel。
The calculation formula of the bias current obtained by the adjustment of the high-voltage controller and the low-voltage controller is as follows:
wherein k isp、kiAre the parameters of the high-pressure controller and the low-pressure controller, respectively.
Because the upper limit value and the lower limit value of the active current output by the receiving end converter station correspond to the maximum inversion power and the maximum rectification power, the two values are equal in size and opposite in direction, and the relationship is as follows:
ilim＝PM/ud
in the formula: pMIs the maximum transmission power, u, of the converter stationdIs the d-axis voltage component of the ac power grid.
In addition, when the upper limit voltage and the pre-set voltage are presetThe lower limit voltage is too close to the steady-state value u of the direct-current voltage of the receiving end converter stationdc_refMay cause the VSG control system of the present application to perform unnecessary actions within the normal voltage fluctuation range of the system. If the preset upper limit voltage and the preset lower limit voltage are too far away from the steady-state value u of the direct-current voltage of the receiving end converter stationdc_refMay cause the VSG control system to experience overvoltage or sustained undervoltage problems in the event of a power imbalance. In order to avoid unnecessary actions of the controller, maintain the direct current voltage of the system in a reasonable range under the condition of power unbalance, and enable all converters to participate in power coordination together when the power is unbalanced, the selection formula of the preset upper limit voltage and the preset lower limit voltage is as follows:
in the formula: Δ u is a voltage margin, and a typical value Δ u may be 0.05 pu.
The receiving end converter station of the multi-end direct current transmission system is equivalent to a virtual synchronous generator, so that the converter can show the inertia and damping action of the virtual synchronous generator; by establishing a calculation model of a mechanical power and active power instruction of a VSG control system and a frequency deviation of an access point, the converter station accurately transmits active power to an alternating current system according to an active power instruction reference value in a normal operation state, provides inertial support for a power grid and actively participates in power grid frequency adjustment. By introducing the high/low voltage controller for adjusting the active current output by the VSG control system, when the main station exits from operation due to a fault, the system can quickly respond when monitoring the voltage deviation, so that the fluctuation of the direct-current voltage is reduced.
In a specific embodiment, when the VSG control system of the present application operates normally, the power fluctuation of the system is balanced by using the converter station in the dc voltage control mode as a balance node, and the stable operation of the multi-terminal dc system is maintained. DC voltage udcBetween a preset upper limit voltage udc_hAnd a preset lower limit voltage udc_lIn between, the output of high and low voltage controllersThe output is 0. When P is presentin＞PoutWhen the DC voltage is shifted upwards, the DC voltage u is shifted upwardsdcExceeds udc_hWhen the high voltage controller outputs a positive bias current delta ihSuperimposed on the active current id_refThus, the absolute value of the d-axis current command value of the rectifying station is increased. The active current output of a current converter at the receiving end is increased to promote the balance of the active power flow at the transmitting end and the receiving end of the direct current system, and finally the direct current voltage is controlled to be stabilized at udc_hTo (3). In the same way, when Pin＜PoutWhen the DC voltage is shifted down, when udcLower than udc_lThe low-voltage controller will output a negative Δ ilIs superimposed on id_refTherefore, the active current output of the receiving end converter is reduced, and the direct-current voltage is prevented from further falling.
Therefore, when the multi-terminal direct current transmission system is normal, the receiving-terminal converter operates in a traditional VSG control mode and participates in power grid frequency modulation control; when the direct current voltage is abnormal, the high-voltage and low-voltage coordination controller plays a role, and realizes the rebalancing of the direct current system tide while participating in the primary frequency modulation of the system.
The above is an embodiment of the method of the present application, and the present application also includes an embodiment of a VSG control apparatus, as shown in fig. 2, where fig. 2 includes:
an equivalence unit 201, configured to equivalence a receiving-end converter station of a multi-end direct current transmission system into a virtual synchronous generator;
a building unit 202, configured to build a calculation model of the mechanical power and active power commands of the VSG control system and the frequency deviation of the access point:
Pm＝Pref+kf(f0-f)
in the formula, PmMechanical power, P, for virtually synchronous machinesrefFor virtual active power commands, kfF0-f is the frequency deviation of the access point;
and the adjusting unit 203 is used for introducing a high/low voltage controller for adjusting the active current output by the VSG control system, so that the active current value input to the AC network is kept in a preset interval.
In a specific embodiment, the equivalence unit 201 is further configured to equate the converter potential to an internal potential of the virtual synchronous generator, the inductance value of the converter reactor to a synchronous inductance of the virtual synchronous generator, the internal resistance of the converter reactor to a synchronous resistance of the virtual synchronous generator, and the dc terminal of the converter to a prime mover of the virtual synchronous generator.
In a specific drop embodiment, the system further comprises a reactive power adjusting unit, which is used for calculating a machine end reference voltage of the virtual synchronous generator by comparing a reactive instruction output by the VSG control system with a reactive output value, comparing the machine end reference voltage with a measured voltage of the virtual synchronous generator, and inputting a comparison result into the PI controller to obtain a virtual potential amplitude of the virtual synchronous generator, thereby completing reactive power adjustment;
the calculation formula of the generator-end reference voltage of the virtual synchronous generator is as follows:
Uref＝E0+ΔE＝E0+kq(Qref-Q)
in the formula, E0Is the effective value of no-load electromotive force, k, of the virtual synchronous machineqTo adjust the coefficient of reactive power, QrefAnd Q is a reactive instruction and a reactive output value output by the VSG control system respectively.
In a specific drop embodiment, the adjusting unit 203 is further configured to introduce a high/low voltage controller for adjusting the active current output by the VSG control system, so that the active current value input to the ac network is maintained in a preset interval, including:
when the direct current voltage is greater than the preset upper limit voltage or the direct current voltage is less than the preset lower limit voltage, the high/low voltage controller generates bias current to be superposed on active current output by the VSG control system, and the superposed active current is as follows:
in the formula udcIs a direct voltage udc_hAnd udc_lAre respectively provided withA preset upper limit voltage and a preset lower limit voltage; Δ ih，ΔilFor bias current, id_refAnd controlling the active current output by the system for the VSG.
The present application further provides an embodiment of a VSG control apparatus, the apparatus comprising a processor and a memory: the memory is used for storing the program codes and transmitting the program codes to the processor; the processor is configured to execute an embodiment of a VSG control method of the present application according to instructions in the program code.
The present application also provides a computer-readable storage medium for storing program code for performing embodiments of a VSG control method of the present application.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The terms "first," "second," "third," "fourth," and the like in the description of the present application and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A VSG control method, comprising:
a receiving end converter station of the multi-end direct current transmission system is equivalent to a virtual synchronous generator;
establishing a calculation model of mechanical power and active power instructions of the VSG control system and frequency deviation of the access point:
Pm＝Pref+kf(f0-f)
in the formula, PmTo simulate the mechanical power of a synchronous generator, PrefFor virtual active power commands, kfIs the frequency modulation coefficient, f0-f is the frequency offset of the access point;
and introducing a high/low voltage controller for regulating the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval.
2. The VSG control method of claim 1, wherein the equating a receiving end converter station of the multi-terminal dc transmission system to a virtual synchronous generator comprises:
and the potential of the converter is equivalent to the internal potential of the virtual synchronous generator, the inductance value of the converter reactor is equivalent to the synchronous inductance of the virtual synchronous generator, the internal resistance of the converter reactor is equivalent to the synchronous resistance of the virtual synchronous generator, and the direct-current end of the converter is equivalent to the prime motor of the virtual synchronous generator.
3. The VSG control method according to claim 1, further comprising: the reactive instruction output by the VSG control system is compared with a reactive output value, a machine end reference voltage of the virtual synchronous generator is calculated, the machine end reference voltage is compared with the measured voltage of the virtual synchronous generator end, and the comparison result is input into a PI controller to obtain a virtual potential amplitude of the virtual synchronous generator, so that reactive power regulation is completed;
the calculation formula of the generator-end reference voltage of the virtual synchronous generator is as follows:
Uref＝E0+ΔE＝E0+kq(Qref-Q)
in the formula, E0Is the effective value of no-load electromotive force, k, of the virtual synchronous machineqTo adjust the coefficient of reactive power, QrefAnd Q is a reactive instruction and a reactive output value output by the VSG control system respectively.
4. The VSG control method of claim 1, wherein the introducing of the high/low voltage controller is used for adjusting an active current output by the VSG control system so that an active current value input to the AC network is maintained at a preset interval, and comprises:
when the direct current voltage is greater than the preset upper limit voltage or the direct current voltage is less than the preset lower limit voltage, the high/low voltage controller generates bias current to be superposed on active current output by the VSG control system, and the superposed active current is as follows:
in the formula udcIs a direct voltage udc_hAnd udc_lRespectively a preset upper limit voltage and a preset lower limit voltage; Δ ih，ΔilFor bias current, id_refAnd controlling the active current output by the system for the VSG.
5. A VSG control apparatus, comprising:
the equivalent unit is used for equivalent the receiving end converter station of the multi-end direct current transmission system into a virtual synchronous generator;
the establishing unit is used for establishing a calculation model of the mechanical power and active power instruction of the VSG control system and the frequency deviation of the access point:
Pm＝Pref+kf(f0-f)
in the formula, PmMechanical power, P, for virtually synchronous machinesrefFor virtual active power commands, kfIs the frequency modulation coefficient, f0-f is the frequency offset of the access point;
and the adjusting unit is used for introducing a high/low voltage controller for adjusting the active current output by the VSG control system, so that the active current value input to the alternating current network is kept in a preset interval.
6. The VSG control device according to claim 5, wherein the equivalence unit is further configured to equivalence a converter potential to an internal potential of the virtual synchronous generator, an inductance value of a converter reactor to a synchronous inductance of the virtual synchronous generator, an internal resistance of the converter reactor to a synchronous resistance of the virtual synchronous generator, and a DC end of the converter to a prime mover of the virtual synchronous generator.
7. The VSG control device of claim 5, further comprising:
the reactive power adjusting unit is used for comparing a reactive instruction output by the VSG control system with a reactive output value, calculating a machine end reference voltage of the virtual synchronous generator, comparing the machine end reference voltage with the measured voltage of the virtual synchronous generator end, and inputting a comparison result into the PI controller to obtain a virtual potential amplitude of the virtual synchronous generator so as to complete reactive power adjustment;
the calculation formula of the generator-end reference voltage of the virtual synchronous generator is as follows:
Uref＝E0+ΔE＝E0+kq(Qref-Q)
in the formula, E0Is the effective value of no-load electromotive force, k, of the virtual synchronous machineqTo adjust the coefficient of reactive power, QrefAnd Q is a reactive instruction and a reactive output value output by the VSG control system respectively.
8. The VSG control device of claim 5, wherein the regulating unit is further configured to introduce a high/low voltage controller for regulating an active current output by the VSG control system such that the active current value input to the AC network is maintained at a preset interval, and comprises:
when the direct current voltage is greater than the preset upper limit voltage or the direct current voltage is less than the preset lower limit voltage, the high/low voltage controller generates bias current to be superposed on active current output by the VSG control system, and the superposed active current is as follows:
in the formula, udcIs a direct voltage udc_hAnd udc_lRespectively a preset upper limit voltage and a preset lower limit voltage; Δ ih，ΔilFor bias current, id_refAnd controlling the active current output by the system for the VSG.
9. A VSG control apparatus, the apparatus comprising a processor and a memory:
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the VSG control method of any of claims 1-4 according to instructions in the program code.
10. A computer-readable storage medium for storing program code for executing the VSG control method of any one of claims 1-4.
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