CN113612257A - Virtual synchronous generator control system and control method thereof - Google Patents
Virtual synchronous generator control system and control method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/40—Synchronising a generator for connection to a network or to another generator
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention provides a virtual synchronous generator control system and a control method thereof. The system comprises a unit voltage upper limit control module, a unit voltage lower limit control module, a frequency control module, an active current instruction switching module, an active current control module, a power grid synchronization module, an alternating voltage control module, a reactive current control module, an active current virtual impedance module, a reactive current virtual impedance module and a coordinate transformation module. The method adopts active current error to adjust the phase of the output voltage of the converter, adds a damping impedance link in a current control loop, can switch the average voltage control of the capacitor of the constant power unit during the transient fault of the AC/DC side, and can stably operate under the conditions of off-grid and grid-connected of the converter.
Description
Technical Field
The invention relates to the technical field of flexible direct current transmission, in particular to a virtual synchronous generator control system and a control method thereof.
Background
The flexible direct-current transmission technology is rapidly developed, the voltage grade and the capacity are continuously improved, an application occasion covers a power distribution network and a backbone network, a converter becomes one of national core power equipment, and the converter control technology is also one of research hotspots in the field in recent years. The domestic and foreign flexible direct-current engineering mainly adopts a double-end back-to-back connection and multi-end direct-current interconnection structure, the operation mode of the current converter at each end can be automatically switched according to the operation requirement, and the operation mode comprises the passive load independent operation of a separation net belt, and the networking constant-voltage control or constant-power operation. The traditional vector control technology based on grid voltage orientation relies on the synchronization of a phase-locked loop and a power grid, the stability is poor when a weak alternating current system is accessed, the control structures adopted during the off-grid operation and the on-grid operation are different, the off-grid and on-grid control mode switching logic is complex, and the smooth switching is difficult to realize. The control method of the traditional converter virtual synchronous machine is based on the control idea of a synchronous generator, the output voltage frequency of the converter is adjusted by adopting active deviation, the self-synchronization of the converter and a power grid is realized, the influence of a phase-locked loop on a system is eliminated, and meanwhile, based on the synchronization mechanism, the control structure of the virtual synchronous machine can stably run under the working conditions of off-grid and on-grid, so that the switching of the control structure is not needed in the off-grid and on-grid conversion process.
The virtual synchronous machine control is one of the research hotspots in the control direction of the current converter recently, and a typical current converter virtual synchronous generator control structure is provided in the literature 'a multi-inverter microgrid frequency non-difference regulation strategy based on a virtual synchronous generator', an inertia link is adopted in an active control loop to simulate the natural inertia of the synchronous generator, a pure integral module is used for calculating the alternating voltage phase of the current converter, the self-synchronization with the power grid is realized, the current converter virtual synchronous generator can stably run under the working conditions of off-grid and grid-connection, but due to the serial connection structure of the virtual inertia link, the integral module and the pure integral module, the structure has limited active power regulation speed, no direct control link for introducing current, and slow current response speed.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a virtual synchronous generator control system and a control method thereof. In order to achieve the purpose of the invention, the technical scheme of the invention is as follows.
A virtual synchronous generator control system comprises a unit voltage upper limit control module, a unit voltage lower limit control module, a frequency control module, an active current instruction switching module, an active current control module, a power grid synchronization module, an alternating voltage control module, a reactive current control module, an active current virtual impedance module, a reactive current virtual impedance module and a coordinate transformation module; the unit voltage upper limit control module, the unit voltage lower limit control module and the frequency control module are connected with the active current instruction switching module; the active current instruction switching module, the active current control module and the power grid synchronization module are sequentially connected in series; the alternating voltage control module is connected with the reactive current control module in series; the active current instruction switching module comprises a maximum operation module and a minimum operation module.
Preferably, the input of the minimum operation module comprises a first active current given value Idref1And a second active current setpoint value Idref2The input of the maximum operation module comprises a third active current given value Idref3The output end of the minimum operation module is connected with the other input end of the maximum operation module.
Preferably, the output current of the active current instruction switching module and the output voltage phase θ of the power grid synchronization module are respectively input to an active current set value input end of the active current virtual impedance module and a phase control input end of the coordinate transformation module;
the active current control module transmits the deviation of an active current given value Idref and an active current feedback value Idfbk to the input end of a low-pass filtering module, the low-pass filtering module is connected with a proportional regulator in series, and the output of the proportional regulator is a converter voltage angular frequency regulating quantity delta omega;
the reactive current control module sets a reactive current set value IqrefAnd a reactive current feedback value IqfbkThe deviation is transmitted to the input end of a low-pass filter, the output of the low-pass filter is connected with a reactive current proportion regulator, and the reactive current proportion regulator outputs the amplitude adjustment quantity delta E of the alternating voltage of the converter.
Preferably, the voltage upper limit control module is used for setting the voltage average value upper limit set value vc _ max and the actual average value vc _ av of the converter unitgIs fed to the input of a first proportional integral regulator whose output is a first active current set signal Idref1；
The frequency control module sets the frequency f of the alternating voltagerefFrequency feedback value f of AC voltage of inverterfbkThe deviation is transmitted to the input end of a second proportional-integral regulator, and the output of the second proportional-integral regulator is a second active current given signal Iderf2；
The voltage lower limit control module sets the voltage average value lower limit set value v of the converter unitc_minWith the actual average value vc_avgThe deviation is transmitted to the input end of a third proportional-integral regulator, and the output of the third proportional-integral regulator is a third active current given signal Idref3；
The AC voltage control module sets the voltage amplitude value to be ErefAnd a voltage amplitude feedback value EfbkIs connected with the input end of a fourth proportional-integral regulator, and the fourth proportional-integral regulator outputs a reactive current set value Iqref。
Preferably, the grid synchronization module adjusts the voltage angular frequency by a voltage angular frequency adjustment amount Δ ω and a voltage angular frequency nominal value ω0Adding to obtain a converter voltage angular frequency given value omega, connecting the converter angular frequency given value omega with an input end of an integration module, and outputting a converter voltage phase given signal theta by the integration module; the power grid synchronization module converts the frequency signal f of the converter voltagefbkAnd the phase given signal theta output is respectively connected with the corresponding input ends of the frequency control module and the coordinate transformation module.
The virtual synchronous generator control method based on the virtual synchronous generator control system comprises the following steps
Setting the active current value IdrefAnd the active current feedback value IdfbkObtaining an active current error signal delta I by calculating deviationdActive current error signal Δ IdAnd the low-pass filtered signal DeltaIdlObtaining high-frequency component delta I of active current error by calculating deviationdhObtaining the control component delta E of the virtual impedance of the active current after proportion adjustmentd；
Setting the reactive current value IqrefAnd a reactive current feedback value IqfbkObtaining a reactive current error signal delta I by calculating deviationqError signal Δ I of reactive currentqObtaining the high-frequency component delta I of the reactive current error by calculating the deviation with the signal after low-pass filteringqhObtaining a reactive current virtual impedance control component delta E after proportional adjustmentq；
Converting signals of a d-axis input end, a q-axis input end and a phase control input end into a rotating coordinate three-phase static coordinate system, wherein the phase input end of the d-axis input end is a converter d-axis control component VdrefOutput of delta E by an active current virtual impedance moduledThe output delta E of the reactive current control module and the rated alternating voltage amplitude E0Stacking; the q-axis input end is a converter q-axis control component VqrefOutput of Delta E by a reactive current virtual impedance moduleqAnd a rated alternating voltage q-axis component Eq0And (4) overlapping.
Preferably, the q-axis component E of the rated alternating voltageq0And the output delta E of the reactive current virtual impedance moduleqObtaining the q-axis control component V of the converter by calculating the deviationqref(ii) a Output delta E of reactive current control module and output delta E of active current virtual impedance moduledDeviation from nominal ac voltage amplitude E0Adding to obtain d-axis control component V of converterdref.。
Preferably, during transient fault, if alternating current/direct current transient fault working condition causes power unit capacitor voltage average value vc_avgHigher than the upper limit set value of the average value of the unit voltagevc_maxThe first proportional integral regulator output exits the upper bound and continues to decrease and when its value is less than Idref2And in the transient process, the control target of the converter is switched to be the control of the average value of the capacitor voltage of the constant power unit.
Compared with the prior art, the invention has the beneficial technical effects that: 1. the invention utilizes the active current error to adjust the output voltage phase of the converter to realize the synchronization function with the power grid, avoids the stability problem caused by a phase-locked loop in the vector control strategy of the converter, and improves the stability of the high-capacity flexible direct current converter when the high-capacity flexible direct current converter is connected into a weak alternating current system. 2. The damping impedance link is added in the current control loop, so that the current control characteristic of the current converter is improved, the response speed of the current control loop is increased, and the response speed of active power and reactive power of the current converter is increased. 3. The invention can switch the average voltage control of the capacitor of the constant power unit during the transient fault of the AC/DC side, keep the power balance of the AC and DC sides of the converter to the maximum extent and improve the fault ride-through performance of the converter. 4. The invention does not depend on the synchronization with a phase-locked loop and a power grid, can stably operate under the conditions of the off-grid and on-grid of the converter, and has higher reliability of the off-grid and on-grid operation of the converter.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a diagram of a control method of an improved virtual synchronous machine of a current converter;
FIG. 2 is a schematic diagram of a cell upper voltage limit control module
FIG. 3 is a block diagram of a unit voltage lower limit control module
FIG. 4 is a schematic diagram of a frequency control module
FIG. 5 is a schematic diagram of an active current command switch module
FIG. 6 is a schematic diagram of an active current control module
FIG. 7 schematic diagram of a grid synchronization module
FIG. 8 A.C. voltage control module schematic
FIG. 9 schematic diagram of a reactive current control module
FIG. 10 is a schematic diagram of an active current virtual impedance block
FIG. 11 reactive current virtual impedance block schematic
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, 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 the embodiments.
As shown in fig. 1, the virtual synchronous generator control system of the present embodiment includes an active control and voltage amplitude control section. Active current instruction switching module output I of active control partdrefAnd the output voltage phase theta of the power grid synchronization module is respectively connected with the active current set value input end of the active current virtual impedance module in the voltage amplitude control part and the phase control input end of the coordinate transformation module. The active control part comprises a unit voltage upper limit control module, a unit voltage lower limit control module, a frequency control module, an active current instruction switching module, an active current control module and a power grid synchronization module. The unit voltage upper limit control module, the unit voltage lower limit control module and the frequency control module are connected with the active current instruction switching module. The active current instruction switching module, the active current control module and the power grid synchronization module are sequentially connected in series. Final frequency signal f output by the grid synchronization modulefbkAnd feeding back to the corresponding input end of the frequency control module. The voltage amplitude control part comprises an alternating voltage control module, a reactive current control module, an active current virtual impedance module, a reactive current virtual impedance module and a coordinate transformation (dq/abc) module. The alternating voltage control module is connected with the reactive current control module in series, and the reactive current control module outputs delta E and the active current virtual impedance module outputs delta EdMake a difference and then cross with the rated valueAmplitude of the current voltage E0Adding to obtain d-axis control component V of converterdrefAnd the input end of the coordinate transformation module is connected with the d-axis input end of the coordinate transformation module. Q-axis component E of rated AC voltageq0And the output delta E of the reactive current virtual impedance moduleqMaking difference to obtain q-axis control component V of current converterqrefAnd then connected with the q-axis input end of the coordinate transformation module.
As shown in fig. 2 to 11, the virtual synchronous generator control method of the present embodiment includes a voltage upper limit control module for setting an upper limit set value v of an average value of the voltage of the converter unitc_maxWith the actual average value vc_avgAnd performing difference, wherein the difference value is connected with the input end of a first proportional-integral regulator PI1, and the output of the PI1 is a first active current given signal I output by the voltage upper limit control moduledref1. Wherein the output of PI1 has amplitude limiting function, and the upper and lower amplitude limits are IdmaxAnd Idmin。
The voltage lower limit control module is used for setting the lower limit set value v of the average value of the voltage of the converter unitc_minWith the actual average value vc_avgAnd performing difference, wherein the difference value of the first and second positive current signals is connected with the input end of a third proportional-integral regulator PI3, and the output of the PI3 is a third active current given signal I output by the voltage lower limit control moduledref3. Wherein the output of PI3 has amplitude limiting function, and the upper and lower amplitude limits are IdmaxAnd Idmin。
The frequency control module sets the frequency f of the alternating voltagerefFrequency feedback value f of AC voltage of inverterfbkMaking a difference, wherein the difference value is connected with the input end of a second proportional-integral regulator PI2, and the output of the PI2 is a second active current given signal I output by the frequency control modulederf2. Wherein the frequency feedback value f of the alternating voltagefbkAnd calculating by a power grid synchronization module.
The active current instruction switching module comprises a module for taking maximum Max and minimum operation Min, and the input of the minimum operation Min is the first active current given Idref1And the second active current gives Idref2Setting I by taking the output of the minimum operation and the third active currentdref3To take the input of the maximum operation, the maximum operation output is taken asFinal active current given IdrefNamely, the output is the output of the active instruction switching module. Wherein Idref1Output from the cell voltage upper limit control module, Idref2Output from the frequency control module, Idref3An output from the cell voltage lower limit control module. Under steady-state operating conditions, Idref1>Idref2>Idref3I.e. the mean value of the voltage of the power cell is the nominal value in the steady state, Idref1The value is the upper limit amplitude I of the first proportional integral regulator PI1dref1＝IdmaxAnd I isdref3The value is the lower limit amplitude I of the third proportional-integral regulator PI3dref3＝IdminTherefore, after Max and Min operation, I is outputdref＝Idref2Namely, the inverter control target is constant frequency control at the steady state. During transient fault, the average value v of the capacitor voltage of the power unit is assumed to be caused by AC/DC transient fault working conditionc_avgHigher than the upper limit set value v of the average value of the unit voltagec_maxThen the first proportional-integral regulator PI1 output exits upper bound and continues to decrease when its value is less than Idref2Then, finally, after Max and Min operation, I is outputdref＝Idref1Namely, the inverter control target is switched to be the constant power unit capacitor voltage average value control in the transient process. On the contrary, if the transient fault working condition causes the average value v of the capacitor voltage of the power unitc_avgLower than the lower limit set value v of the average value of the unit voltagec_minThe regulation process is similar and the final output I isdref＝Idref3Further reduction of the power cell voltage may be limited.
The active current control module gives an active current given value IdrefAnd an active current feedback value IdfbkMaking difference, the difference and low-pass filtering link
Input end connection, low-pass filtering link and proportional regulator KfSeries, proportional regulator KfThe output is the converter voltage angular frequency regulating quantity delta omega, namely the output of the active current control module. Wherein the given value of active current IdrefFrom active powerAnd the current instruction switches the output of the module. The time constant T of the low-pass filtering link1And the value can be the same magnitude as the power frequency period of 0.02 s.
The power grid synchronization module adjusts the voltage angular frequency adjustment quantity delta omega and the voltage angular frequency rated value omega0Adding to obtain a converter voltage angular frequency given value omega, a converter angular frequency given value omega sum and an integral module
The input ends are connected, and the integration module outputs a given signal theta of the voltage phase of the converter. The converter angular frequency given value omega is simultaneously multiplied by the angular frequency unit transformation coefficient 50/(100 x pi), and the angular frequency omega dimension is converted from radian/s into Hz output ffbk. The power grid synchronization module converts the frequency signal f of the converter voltagefbkAnd the phase given signal theta is output and is respectively connected with the corresponding input ends of the frequency control module and the coordinate transformation module.
The alternating voltage control module sets a voltage amplitude value to be ErefWith its feedback value EfbkMaking difference, connecting the difference value with input end of fourth proportional-integral regulator PI4, PI4 outputting reactive current set value IqrefI.e. the output of the ac voltage control module.
The reactive current control module sets a reactive current set value IqrefWith its feedback value IqfbkMaking a difference, the difference and a low-pass filter
Input end connection, low-pass filtering output and reactive current proportional regulator KvConnecting, proportional regulator KvAnd outputting the AC voltage amplitude adjustment quantity delta E of the converter, namely the output of the reactive current control module. The time constant T of the low-pass filtering link1And the same magnitude value as the power frequency period of 0.02s can be taken as the same magnitude value.
The active current virtual impedance module is used for setting an active current set value IdrefWith its feedback value IdfbkObtaining an active current error signal delta I by performing a differencedActive current error signal deltaIdItself and low-pass filtered
The signal Δ I afterdlMaking difference to obtain high-frequency component delta I of active current errordhThen is mixed with a proportion module KidThe connection obtains the control component delta E of the virtual impedance of the active currentdI.e. the output of the active current virtual impedance module. The low-pass filter time constant T2It may be taken as a large value, such as a 0.2s equivalent magnitude value, filtered to provide a steady state dc component of the signal.
The reactive current virtual impedance module is used for setting a reactive current set value IqrefWith its feedback value IqfbkObtaining a reactive current error signal delta I by differenceqError signal Δ I of reactive currentqItself and low-pass filtered
The difference is made to the latter signals to obtain the high-frequency component delta I of the reactive current errorqhThen is mixed with a proportion module KiqThe reactive current virtual impedance control component Delta E is obtained by connectionqI.e. the output of the reactive current virtual impedance module. The low-pass filter time constant T2It may also be a larger value, such as a 0.2s equivalent magnitude value, filtered to provide a steady state dc component of the signal.
The coordinate transformation module transforms signals of a d-axis input end, a q-axis input end and a phase control input end into a rotating coordinate-three-phase static coordinate system, wherein the phase input end of the d-axis input end is a converter d-axis control component VdrefOutput of delta E by an active current virtual impedance moduledThe output delta E of the reactive current control module and the rated alternating voltage amplitude E0The three parts are superposed. The q-axis input end is a converter q-axis control component VqrefOutput of Delta E by a reactive current virtual impedance moduleqAnd a rated alternating voltage q-axis component Eq0Two parts superposed to form, at steady state Eq0The value is 0. The phase input end is an inverter phase control signal theta. Three-phase static seat with output of coordinate transformation module as current converterControl signal V under the markabcref。
The above-mentioned embodiments are only specific embodiments of the present application, and are used for illustrating the technical solutions of the present application, but not limiting the same, and the scope of the present application is not limited thereto, and although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope disclosed in the present application; such modifications, changes or substitutions do not depart from the spirit and scope of the present disclosure, which should be construed in light of the above teachings. Are intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (8)
1. A virtual synchronous generator control system is characterized by comprising a unit voltage upper limit control module, a unit voltage lower limit control module, a frequency control module, an active current instruction switching module, an active current control module, a power grid synchronization module, an alternating voltage control module, a reactive current control module, an active current virtual impedance module, a reactive current virtual impedance module and a coordinate transformation module; the unit voltage upper limit control module, the unit voltage lower limit control module and the frequency control module are connected with the active current instruction switching module; the active current instruction switching module, the active current control module and the power grid synchronization module are sequentially connected in series; the alternating voltage control module is connected with the reactive current control module in series; the active current instruction switching module comprises a maximum operation module and a minimum operation module.
2. The virtual synchronous generator control system of claim 1, wherein the input of the min-taking module comprises a first active current setpoint Idref1And a second active current setpoint value Idref2The input of the maximum operation module comprises a third active currentGiven value Idref3The output end of the minimum operation module is connected with the other input end of the maximum operation module.
3. The virtual synchronous generator control system according to claim 2, wherein the output current of the active current command switching module and the output voltage phase of the grid synchronization module are respectively input to an active current set value input terminal of the active current virtual impedance module and a phase control input terminal of the coordinate transformation module;
the active current control module gives an active current given value IdrefAnd an active current feedback value IdfbkThe deviation is transmitted to the input end of a low-pass filtering module, the low-pass filtering module is connected with a proportional regulator in series, and the output of the proportional regulator is the voltage angular frequency regulating quantity delta omega of the current converter;
the reactive current control module sets a reactive current set value IqrefAnd a reactive current feedback value IqfbkThe deviation is transmitted to the input end of a low-pass filter, the output of the low-pass filter is connected with a reactive current proportion regulator, and the reactive current proportion regulator outputs the amplitude adjustment quantity delta E of the alternating voltage of the converter.
4. The virtual synchronous generator control system of claim 3, wherein the voltage upper limit control module sets the converter cell voltage average upper limit set value vc_maxWith the mean value vc_avgIs fed to the input of a first proportional integral regulator whose output is a first active current set signal Idref1；
The frequency control module sets the frequency f of the alternating voltagerefFrequency feedback value f of AC voltage of inverterfbkThe deviation is transmitted to the input end of a second proportional-integral regulator, and the output of the second proportional-integral regulator is a second active current given signal Iderf2；
The voltage lower limit control module sets the voltage average value lower limit set value v of the converter unitc_minWith the mean value vc_avgThe deviation is fed to the input of a third proportional-integral regulator, the third ratioExample output of integral regulator for third active current given signal Idref3；
The AC voltage control module sets the voltage amplitude value to be ErefAnd a voltage amplitude feedback value EfbkIs connected with the input end of a fourth proportional-integral regulator, and the fourth proportional-integral regulator outputs a reactive current set value Iqref。
5. The virtual synchronous generator control system of claim 4, wherein the grid synchronization module adjusts the voltage angular frequency by an amount Δ ω and a voltage angular frequency nominal value ω0Adding to obtain a converter voltage angular frequency given value omega, connecting the converter angular frequency given value omega with an input end of an integration module, and outputting a converter voltage phase given signal theta by the integration module; the power grid synchronization module converts the frequency signal f of the converter voltagefbkAnd the phase given signal theta output is respectively connected with the corresponding input ends of the frequency control module and the coordinate transformation module.
6. A virtual synchronous generator control method based on the virtual synchronous generator control system according to any one of claims 1 to 5, characterized by comprising:
setting the active current value IdrefAnd the active current feedback value IdfbkObtaining an active current error signal delta I by calculating deviationdActive current error signal Δ IdAnd the low-pass filtered signal DeltaIdlObtaining high-frequency component delta I of active current error by calculating deviationdhObtaining the control component delta E of the virtual impedance of the active current after proportion adjustmentd；
Setting the reactive current value IqrefAnd a reactive current feedback value IqfbkObtaining a reactive current error signal delta I by calculating deviationqError signal Δ I of reactive currentqObtaining the high-frequency component delta I of the reactive current error by calculating the deviation with the signal after low-pass filteringqhObtaining a reactive current virtual impedance control component delta E after proportional adjustmentq；
Combining d-axis input end, q-axis input end and phaseThe signal of the bit control input end is used for converting a three-phase static coordinate system of a rotating coordinate, wherein the phase input end of the d-axis input end is a d-axis control component V of the current converterdrefOutput of delta E by an active current virtual impedance moduledThe output delta E of the reactive current control module and the rated alternating voltage amplitude E0Stacking; the q-axis input end is a converter q-axis control component VqrefOutput of Delta E by a reactive current virtual impedance moduleqAnd a rated alternating voltage q-axis component Eq0And (4) overlapping.
7. The virtual synchronous generator control method according to claim 6, wherein the rated alternating voltage q-axis component Eq0And the output delta E of the reactive current virtual impedance moduleqObtaining the q-axis control component V of the converter by calculating the deviationqref(ii) a Output delta E of reactive current control module and output delta E of active current virtual impedance moduledDeviation from nominal ac voltage amplitude E0Adding to obtain d-axis control component V of converterdref.。
8. The virtual synchronous generator control method of claim 7, wherein during transient faults, if the AC/DC transient fault condition results in the average value v of the capacitor voltage of the power unitc_avgHigher than the upper limit set value v of the average value of the unit voltagec_maxThe first proportional integral regulator output exits the upper bound and continues to decrease and when its value is less than Idref2And in the transient process, the converter control target is switched to be controlled by the constant power unit capacitor voltage average value.
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