CN106099974A - For realizing the HVDC flywheel sychronising control method of wind field frequency response - Google Patents

Abstract

The invention discloses a kind of HVDC flywheel sychronising control method for realizing wind field frequency response, including receiving end current conversion station and the control of sending end current conversion station: use for reference the synchronized mechanism of synchrodrive, HVDC busbar voltage is equivalent to synchrodrive rotor frequency, the modulation degree of HVDC is equivalent to synchrodrive air gap flux linkage, under this control thought, HVDC will be presented as the synchrodrive with bus capacitor true inertia size by end station, while guaranteeing synchronism stability, realize busbar voltage and electrical network a-c cycle real-time linkage, can be set up from mains frequency on the bank to the Mirroring Mapping of marine wind field a-c cycle by the cooperation of sending end current conversion station again, wind field is enable to learn mains frequency information on the bank in time, and then it is greatly improved wind field inertia response quality.Meanwhile, the present invention controls lower HVDC and be can also be embodied as voltage source electrical characteristic by end station, overcomes the stability problem that current source weak net exist, a-c cycle is undistorted mirror image, has the strongest weak net stable operation ability.

Description

For realizing the HVDC flywheel sychronising control method of wind field frequency response

Technical field

The present invention relates to the control of flexible direct current power transmission system, a kind of HVDC for realizing wind field frequency response Flywheel sychronising control method, is applied to the flexible direct current power transmission system that remote marine wind field is grid-connected, including receiving end current conversion station with Meritorious/idle the control strategy of sending end current conversion station.

Background technology

Marine wind field is shown in Fig. 1 through the grid-connected basic topology of flexible DC power transmission, and system is mainly by wind field part and flexible direct current Transmission of electricity (the most soft straight) part composition, flexible direct current part include sending end current conversion station (SEC), receiving end current conversion station (REC) with And the structure such as direct current cables.

Under under traditional control method, receiving end current conversion station is operated in current source vector controlled pattern, realized same by phaselocked loop The structures such as walking grid-connected, it controls target is stable DC voltage, controls loop and includes DC voltage outer shroud, current inner loop, have The advantages such as grid-connected current quality is high, and response is quick, decoupled active and reactive.And sending end current conversion station task is for controlling its AC voltage Amplitude is stablized with frequency, in order to the access of blower fan.

But, the flexible direct current under the vector controlled of conventional current source can bring both sides problem, on the one hand solves due to it Coupling effect, blower fan cannot perceive the frequency change of electrical network on the bank, it is impossible to provides inertia for electrical network, therefore can reduce electrical network regulation Ability；On the other hand under Current Vector Control, electrical network is presented as current source electrical characteristic by VSC-HVDC, when electrical network is stronger not There will be stable problem.But along with wind-powered electricity generation accounting in electrical network increases, electrical network equivalence dies down, and traditional vector controlled is unable to maintain that Comparatively ideal current source characteristic, current response characteristic deteriorates, thus causes a series of mutual stability such as harmonic oscillation such as to ask Topic..

From the perspective of avoiding current source characteristic, controlling in current conversion station applied voltage source is to improve its weak network operation ability A solution.By removing phaselocked loop, the rotor equation using analogy synchronous generator instead completes motor synchronizing process, not only Can solve conventional current vector controlled in the best problem of weak control performance off the net, its virtual inertia can also realize electrical network Frequency change from main response.But this mode is being applied to regenerative resource, such as marine wind electric field through flexible DC power transmission also During the occasion netted, the current source characteristic of wind field can cause receiving end current conversion station cannot therefrom extract inertia, and virtual inertia will be from direct current Electric capacity extracts, the big ups and downs of DC voltage can be caused.

Through retrieving, the Chinese invention patent application of Publication No. CN105429183A, application number: 201610006597.X, Disclosing a kind of permanent magnet direct-drive type offshore grid-connected wind farm system topology and control method thereof, wherein control method includes machine Side rectifier uses rotating speed outer shroud and the double-closed-loop control of current inner loop, in wind field net side current conversion station uses outer voltage and electric current The double-closed-loop control of ring, marine converting plant uses and determines alternating voltage and determine FREQUENCY CONTROL, and Inverter Station uses and determines DC voltage on the bank With the double-closed-loop control determining reactive power.

Wind field under above-mentioned control program brings both sides problem through the grid-connected meeting of flexible DC power transmission, on the one hand due to soft Property direct current transportation decoupling function, blower fan cannot perceive electrical network on the bank frequency change, it is provided that frequency response, this can reduce system Inertia, jeopardizes mains frequency stability；Additionally due to wind electric converter and the buffer action of flexible DC power transmission, Wind turbines Electrical network provides short circuit current hardly, and therefore wind-powered electricity generation accesses at high proportion and is equivalent to make electrical network die down, and reduces system short-circuit ratio.Should Control program designs for ideal voltage source according to electrical network, but under conditions of light current net, traditional vector controlled is unable to maintain that relatively Preferably current source characteristic, current response characteristic deteriorates, thus causes such as a series of mutual stability problems such as harmonic oscillations.

Summary of the invention

For deficiencies of the prior art, it is an object of the invention to provide a kind of for realizing wind field frequency response HVDC flywheel sychronising control method, on the one hand can improve wind field and enter the stability of light current net through soft direct join, the most also Need to be transferred to wind field side by mains frequency change information on the bank by soft lineal system, assist wind field to participate in frequency regulation.

For realizing object above, the invention provides a kind of HVDC flywheel sychronising for realizing wind field frequency response and control Method, including receiving end current conversion station and the control mode of sending end current conversion station: the method uses for reference the synchronized mechanism of synchrodrive, will HVDC busbar voltage is equivalent to synchrodrive rotor frequency, and the modulation degree of HVDC is equivalent to synchrodrive breath magnetic linkage, this control thought Under, HVDC by end station by being presented as the synchrodrive with bus capacitor true inertia size, while guaranteeing synchronism stability, real Existing busbar voltage and electrical network a-c cycle real-time linkage, then can be set up from mains frequency on the bank by the cooperation of sending end current conversion station To the Mirroring Mapping of marine wind field a-c cycle, enable wind field to learn mains frequency information on the bank in time, and then be greatly improved Wind field inertia response quality.

Concrete, a kind of flexible DC power transmission receiving end current conversion station flywheel sychronising controlling party being applicable to offshore grid-connected wind farm Method, described method, using capacitor direct current voltage and reactive power as reference quantity, controls receiving end current conversion station output AC voltage Frequency and amplitude, thus regulate its grid-connected power, and it is grid-connected to realize voltage source control；Wherein: in receiving end current conversion station, described side Method, on the basis of existing virtual synchronous controls, replaces virtual inertia with the inertia of HVDC electric capacity, HVDC busbar voltage is equivalent to Synchrodrive rotor frequency, the modulation degree of HVDC is equivalent to synchrodrive air gap flux linkage, makes HVDC be presented as by end station and has bus electricity Hold the synchrodrive of true inertia size, while guaranteeing synchronism stability, it is achieved busbar voltage is real-time with electrical network a-c cycle Link, i.e. DC voltage amplitude can follow the change of mains frequency, and in addition, under this control, HVDC be can also be embodied as electricity by end station Potential source electrical characteristic, overcomes the stability problem that current source weak net exist.

A kind of flexible DC power transmission sending end current conversion station frequency mirror image control method for coordinating being applicable to offshore grid-connected wind farm, Described method, in sending end current conversion station, is changed using capacitor direct current voltage and AC voltage magnitude as reference quantity, control sending end The frequency of stream station output AC voltage and amplitude, thus maintain the wind field top-cross stream stabilization of power grids, it is simple to wind field accesses, wherein: Existing determine alternating voltage and control method for frequency on the basis of, add from DC voltage to the mapping of AC frequency, by with upper State the cooperation of receiving end current conversion station flywheel sychronising control method, the frequency of AC network on the bank is reflected wind field side rapidly and accurately On a-c cycle, auxiliary wind field participates in frequency response.

Compared with prior art, the present invention has a following beneficial effect:

In the present invention, HVDC will be presented as the synchrodrive with bus capacitor true inertia size by end station, is guaranteeing together While step is stable, it is achieved busbar voltage and electrical network a-c cycle, and busbar voltage is the most real-time with wind field a-c cycle Linkage, and then it is greatly improved wind field inertia response quality.Meanwhile, under flywheel sychronising controls, HVDC be can also be embodied as electricity by end station Potential source electrical characteristic, overcomes the stability problem that current source weak net exist.Therefore, under flywheel sychronising controls, HVDC system has A-c cycle is undistorted mirror image, the feature such as voltage source electrical characteristic, have the strongest weak net stable operation ability.

Accompanying drawing explanation

By the detailed description non-limiting example made with reference to the following drawings of reading, the further feature of the present invention, Purpose and advantage will become more apparent upon:

Fig. 1 is that marine wind field is through flexible DC power transmission grid-connected system basic topology；

Fig. 2 is the receiving end current conversion station flywheel sychronising control principle drawing of one embodiment of the invention；

Fig. 3 is that the sending end current conversion station of one embodiment of the invention coordinates control principle drawing；

Fig. 4 is the overall control principle drawing of one embodiment of the invention；

Fig. 5 is the one embodiment of the invention response simulation waveform figure to wind power swing, and wherein (a) is wind power swing, B () is DC voltage control effect；

Fig. 6 is the response simulation waveform figure that mains frequency is fluctuated by one embodiment of the invention, and wherein (a) is unidirectional current Pressure, (b) is wind field side a-c cycle.

Specific embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.Following example will assist in the technology of this area Personnel are further appreciated by the present invention, but limit the present invention the most in any form.It should be pointed out that, the ordinary skill to this area For personnel, without departing from the inventive concept of the premise, it is also possible to make some deformation and improvement.These broadly fall into the present invention Protection domain.

As it is shown in figure 1, be existing marine wind field through flexible DC power transmission grid-connected basic topology figure, system is mainly by wind field portion Dividing and flexible DC power transmission (hereinafter flexible direct current) part composition, flexible direct current part includes sending end current conversion station (SEC), is subject to The structures such as end current conversion station (REC) and direct current cables.Traditional vector controlled is unable to maintain that comparatively ideal current source characteristic, electric current Response characteristic deteriorates, thus causes such as a series of mutual stability problems such as harmonic oscillations.

The present invention is directed to existing marine wind field through flexible DC power transmission grid-connected system, use flywheel sychronising at receiving end current conversion station Control grid-connected mode, on the basis of original voltage source controls, replace virtual inertia with DC capacitor inertia, simplify control While ring, responded by the inertia of DC capacitor and make when mains frequency changes DC voltage amplitude can promptly and accurately follow it Change, transmits mains frequency information.Then in the Collaborative Control of sending end current conversion station again by the change of DC voltage amplitude again It is changed into the change of its AC frequency, it is achieved from mains frequency on the bank to the Mirroring Mapping of wind field side a-c cycle.

Illustrate implementing ins and outs below:

1) flywheel sychronising of receiving end current conversion station controls

In traditional virtual Synchronization Control, the control of DC voltage generally comprises DC voltage outer shroud, by hypothetical rotor equation The labyrinths such as the power internal ring constituted (such as: Lv Zhipeng etc., virtual synchronous electromotor and the application [J] in micro-capacitance sensor thereof. Proceedings of the CSEE, 2014, (16): 2591-2603).But understanding through analyzing, DC capacitor voltage becomes with AC frequency Negative correlativing relation, the i.e. rising of AC frequency can make grid-connected power become big, and DC voltage reduces, for utilize DC capacitor from Right inertia realizes voltage source control and synchronizes grid-connected, and flywheel sychronising method the most of the present invention can define a coefficient of coup K, binds together AC frequency with DC capacitor voltage.Concrete methods of realizing is the deviation ratio of detection DC voltage, It is multiplied by the deviation ratio directly as output frequency after K:

Wherein ω_recFor receiving end current conversion station output AC frequency, ω_nomFor rated frequency (typically taking 314rad/s), △ ω Rec is the deviation of output AC frequency and rated frequency；U_dcFor DC bus-bar voltage, U_{dc_nom}For DC voltage rated value, Δ U_dcDeviation for DC bus-bar voltage Yu rated value.

Mains frequency changes at ± 0.5Hz (± 1%) under normal circumstances, and DC voltage fluctuation, ± 5%, the most typically takes K=0.2.

For dc bus, either wind power or the change of mains frequency all can cause the nature of DC capacitor voltage Response:

$P_{WF}-P_{grid}={\mathrm{CU}}_{dc}\frac{{\mathrm{dU}}_{dc}}{dt}---\left(2\right)$

Wherein P_WFFor wind power, P_gridFor the grid-connected power of current conversion station on the bank, C is Equivalent DC electric capacity.

When wind power occurs fluctuation, have:

${\mathrm{\ΔP}}_{WF}={\mathrm{CU}}_{dc}\frac{{\mathrm{d\ΔU}}_{dc}}{dt}+{\mathrm{\ΔP}}_{grid}---\left(3\right)$

ΔP_WFFor wind power waves momentum；ΔP_gridFor grid-connected power variation；ΔU_dcFor DC voltage change amount.

Design idle ring speed relatively slow, i.e. short time internal modulation is more constant than m, and the energy regenerative of AC can be subject to by receiving end current conversion station To impact:

${\mathrm{\ΔP}}_{grid}=\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}---\left(4\right)$

Wherein: m is modulation ratio, Reactive Power Control ring determine, δ is merit angle, is in operation by current conversion station output frequency Together decide on mains frequency, U_gridFor grid ac voltage, X is grid-connected reactance；

Therefore DC voltage for the natural response of wind changed power is:

${\mathrm{\ΔP}}_{WF}={\mathrm{CU}}_{dc}\frac{{\mathrm{d\ΔU}}_{dc}}{dt}+\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}---\left(5\right)$

Control strategy in (1) formula of employing, by △ U_dcReplace with △ ω_rec:

${\mathrm{\ΔP}}_{WF}=\frac{1}{K}({\mathrm{CU}}_{dc\_nom}^2-\frac{{\mathrm{d\Δ\ω}}_{rec}}{dt}+\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\Δ\ω}}_{rec})---\left(6\right)$

Δ δ is merit angle variable quantity；Δω_gFor mains frequency variable quantity.

On the other hand, if mains frequency is ω_g, when mains frequency fluctuates, ignore the fluctuation of short time endogenous wind power, i.e. △P_WF=0, have:

${\mathrm{\ΔP}}_{grid}=\frac{{\mathrm{mU}}_{dc\_nom}{U}_g}{X}\mathrm{\Δ}\mathrm{\δ}+\frac{{\mathrm{mU}}_g\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}---\left(7\right)$

$\frac{d\mathrm{\Δ}\mathrm{\δ}}{dt}=({\mathrm{\Δ\ω}}_{rec}-{\mathrm{\Δ\ω}}_g)---\left(8\right)$

Substitute in (3), have:

$\frac{{\mathrm{mU}}_{dc\_nom}{U}_g}{X}\∫({\mathrm{\Δ\ω}}_{rec}-{\mathrm{\Δ\ω}}_g)dt+\frac{{\mathrm{mU}}_g\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}=-{\mathrm{CU}}_{dc}\frac{{\mathrm{d\ΔU}}_{dc}}{dt}---\left(9\right)$

Therefore the frequency fluctuation of AC network can cause the natural response of DC voltage, and the present invention is by controlling in (1) formula Strategy utilizes this natural response and makes it controlled, allows the automatic Tracking Frequency of Power Grids of DC voltage amplitude change, by formula (9) △U_dcReplace with △ ω_rec, its closed loop transfer function is:

Δω_rec=G (s) Δ ω_g (10)

Wherein:

$G\left(s\right)=\frac{K\left(\frac{P_{grid}}{{\mathrm{CU}}_{dc\_nom}^2}\right)\frac{\mathrm{\ω}}{\mathrm{\δ}}}{s^2+\frac{P_{grid}}{{\mathrm{CU}}_{dc\_nom}^2}s+K\left(\frac{P_{grid}}{{\mathrm{CU}}_{dc\_nom}^2}\right)\frac{\mathrm{\ω}}{\mathrm{\δ}}}---\left(11\right)$

In like manner can obtain:

${\mathrm{\ΔU}}_{dc}=\frac{U_{dc\_nom}}{{\mathrm{K\ω}}_{nom}}G\left(s\right){\mathrm{\Δ\ω}}_g---\left(12\right)$

In formula, s is Laplace operator, is used for transmitting function；

Understood receiving end current conversion station response under this control mode by (6) formula and be similar to the synchronous generator of a little inertia Machine, its inertia is determined by capacitance size, typically not over 0.1s.Simultaneously by formula (12), it is subject to when mains frequency changes The DC voltage that end current conversion station is controlled can change therewith.

In addition, using the deviation of reactive power Q rec and given Qref through a pi regulator as alternating voltage Given, to realize the operation of current conversion station unity power factor.

2) sending end current conversion station controls

For the information of mains frequency on the bank representated by DC voltage amplitude is reflected in its AC frequency again, sending end Current conversion station FREQUENCY CONTROL strategy is identical with receiving end current conversion station, as shown in Figure 3, it may be assumed that

$\frac{{\mathrm{\ω}}_{\sec }-{\mathrm{\ω}}_{nom}}{{\mathrm{\ω}}_{nom}}=K\frac{U_{dc}-U_{dc\_nom}}{U_{dc\_nom}}---\left(13\right)$

Unlike receiving end current conversion station, the wind field that sending end current conversion station AC connects is by its frequency of phase locked loop fast lock Rate and phase angle, therefore the change of sending end current conversion station frequency will not directly influence the power of wind field output, only serves transmission information Effect.DC voltage change can be again converted to frequency change in this way, and identical owing to converting ratio, The Mirroring Mapping from the frequency of AC network on the bank to wind field side a-c cycle can be realized, i.e. have ω_sec*=KU_dc*=ω_g* (asterisk represents deviation ratio), as shown in Figure 4.

Being more than the control of sending end current conversion station output frequency, output AC voltage is then by wind field side alternating voltage U_WFWith give The deviation determining Uref determines through a pi regulator.

For verifying the effectiveness of control method of the present invention, according to ginseng shown in table 1 in PSCAD/EMTDC simulation software Number builds the switch models of flexible direct current converter station, and wind field side is replaced by current source, and electrical network is connected with inductance by equivalent voltage source Replacing, different its equivalent inductances of strong and weak electrical network are different.

Table 1 simulation system parameters

Operating mode one: mains frequency keeps 50Hz constant, and in wind power such as Fig. 5, (a) fluctuates between 0.75pu-0.95pu, point Not short-circuit ratio SCR=2,20 time observe the change of DC voltage.

In Fig. 5, (b) is DC bus-bar voltage, it appeared that the little inertia feature of receiving end current conversion station can follow the tracks of rapidly wind Power swing, and under weak grid conditions, also can maintain DC voltage stability.

Operating mode two: wind power takes 0.7pu, when t=3s mains frequency from 50Hz saltus step to 49.5Hz, respectively in short-circuit ratio SCR=2,20 time observe DC voltage and the change of wind field side a-c cycle.

In Fig. 6, (a) is DC voltage, and in Fig. 6, (b) is wind field side a-c cycle, changes wind field from mains frequency The response time of top-cross stream this change of frequency response is about about 120ms, and overshoot is less than 10%, and electrical network dies down to it Response time does not affect.

Above the specific embodiment of the present invention is described.It is to be appreciated that the invention is not limited in above-mentioned Particular implementation, those skilled in the art can make various deformation or amendment within the scope of the claims, this not shadow Ring the flesh and blood of the present invention.

Claims (5)

1. one kind for realizing the HVDC flywheel sychronising control method of wind field frequency response, it is adaptable to offshore grid-connected wind farm soft Property direct current transportation, it is characterised in that: use flywheel sychronising control method at receiving end current conversion station, with capacitor direct current voltage and idle Power, as reference quantity, controls frequency and the amplitude of receiving end current conversion station output AC voltage, thus regulates its grid-connected power, and real Existing voltage source controls grid-connected；Wherein:

In receiving end current conversion station, described method, on the basis of existing virtual synchronous controls, replaces virtual with the inertia of HVDC electric capacity Inertia, is equivalent to synchrodrive rotor frequency by HVDC busbar voltage, and the modulation degree of HVDC is equivalent to synchrodrive air gap flux linkage, makes HVDC is presented as the synchrodrive with bus capacitor true inertia size by end station, while guaranteeing synchronism stability, it is achieved female Line voltage and the real-time linkage of electrical network a-c cycle, i.e. DC voltage amplitude can follow the change of mains frequency, in addition, are somebody's turn to do Control lower HVDC and be can also be embodied as voltage source electrical characteristic by end station, overcome the stability problem that current source weak net exist.

HVDC flywheel sychronising control method for realizing wind field frequency response the most according to claim 1, its feature exists In: described in receiving end current conversion station employing flywheel sychronising control method, refer to:

Define a coefficient of coup K, AC frequency is bound together with DC capacitor voltage, the deviation of DC voltage is taken advantage of As the deviation of AC output frequency after K, there is a formula (1):

Or

Wherein ω_recFor receiving end current conversion station output AC frequency, ω_nomFor rated frequency, △ ω rec is output AC frequency and volume Determine the deviation of frequency；U_dcFor DC bus-bar voltage, U_{dc_nom}For DC voltage rated value, Δ U_dcFor DC bus-bar voltage with specified The deviation of value；

For dc bus, either wind power or the change of mains frequency all can cause naturally ringing of DC capacitor voltage Should:

$P_{WF}-P_{grid}={\mathrm{CU}}_{dc}\frac{{\mathrm{dU}}_{dc}}{dt}---\left(2\right)$

Wherein P_WFFor wind power, P_gridFor the grid-connected power of current conversion station on the bank, C is Equivalent DC electric capacity；

When wind power occurs fluctuation, have:

${\mathrm{\ΔP}}_{WF}={\mathrm{CU}}_{dc}\frac{{\mathrm{d\ΔU}}_{dc}}{dt}+{\mathrm{\ΔP}}_{grid}---\left(3\right)$

ΔP_WFFor wind power waves momentum, Δ P_gridFor the variable quantity of grid-connected power, Δ U_dcFor HVDC busbar voltage variable quantity；

Design idle ring speed relatively slow, i.e. short time internal modulation is more constant than m, and receiving end current conversion station can be by shadow to the energy regenerative of AC Ring:

${\mathrm{\ΔP}}_{grid}=\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}---\left(4\right)$

Wherein: m is modulation ratio, Reactive Power Control ring determine, δ is merit angle, it is in operation by current conversion station output frequency and electricity Net frequency together decides on, U_gridFor grid ac voltage, X is grid-connected reactance；

Therefore DC voltage for the natural response of wind changed power is:

${\mathrm{\ΔP}}_{WF}={\mathrm{CU}}_{dc}\frac{{\mathrm{d\ΔU}}_{dc}}{dt}+\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}---\left(5\right)$

Control strategy in (1) formula of employing, by △ U_dcReplace with △ ω_rec:

${\mathrm{\ΔP}}_{WF}=\frac{1}{K}({\mathrm{CU}}_{dc\_nom}^2\frac{{\mathrm{d\Δ\ω}}_{rec}}{dt}+\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\Δ\ω}}_{rec})---\left(6\right)$

On the other hand, if mains frequency is ω_g, when mains frequency fluctuates, ignore the fluctuation of short time endogenous wind power, i.e. △ P_WF =0, have:

${\mathrm{\ΔP}}_{grid}=\frac{{\mathrm{mU}}_{dc\_nom}{U}_{grid}}{X}\mathrm{\Δ}\mathrm{\δ}+\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}---\left(7\right)$

$\frac{d\mathrm{\Δ}\mathrm{\δ}}{dt}=({\mathrm{\Δ\ω}}_{rec}-{\mathrm{\Δ\ω}}_g)---\left(8\right)$

Δ δ is merit angle variable quantity, Δ ω_gFor mains frequency variable quantity；

Substitute in (3), have:

$\frac{{\mathrm{mU}}_{dc\_nom}{U}_{grid}}{X}\∫\left({\mathrm{\Δ\ω}}_{rec}-{\mathrm{\Δ\ω}}_g\right)dt+\frac{{\mathrm{mU}}_{grid}\mathrm{\δ}}{X}{\mathrm{\ΔU}}_{dc}=-{\mathrm{CU}}_{dc}\frac{{\mathrm{d\ΔU}}_{dc}}{dt}---\left(9\right)$

Therefore the frequency fluctuation of AC network can cause the natural response of DC voltage, utilizes this by control strategy in (1) formula Plant natural response and make it controlled, allowing the automatic Tracking Frequency of Power Grids of DC voltage amplitude change, by △ U in formula (9)_dcReplace with △ω_rec, its closed loop transfer function is:

Δω_rec=G (s) Δ ω_g (10)

Wherein:

$G\left(s\right)=\frac{K\left(\frac{P_{grid}}{{\mathrm{CU}}_{dc\_nom}^2}\right)\frac{{\mathrm{\ω}}_{nom}}{\mathrm{\δ}}}{s^2+\frac{P_{grid}}{{\mathrm{CU}}_{dc\_nom}^2}s+K\left(\frac{P_{grid}}{{\mathrm{CU}}_{dc\_nom}^2}\right)\frac{{\mathrm{\ω}}_{nom}}{\mathrm{\δ}}}---\left(11\right)$

In like manner can obtain:

${\mathrm{\ΔU}}_{dc}=\frac{U_{dc\_nom}}{{\mathrm{K\ω}}_{nom}}G\left(s\right){\mathrm{\Δ\ω}}_g---\left(12\right)$

In formula, s is Laplace operator, is used for transmitting function；

Understood receiving end current conversion station response under this control mode by (6) formula and be similar to the synchronous generator of a little inertia, its Inertia is determined by capacitance size, simultaneously by formula (12), the unidirectional current that receiving end current conversion station is controlled when mains frequency changes Pressure can change therewith.

A kind of HVDC flywheel sychronising control method for realizing wind field frequency response the most according to claim 2, it is special Levy and be: K value is: K=0.2.

4. according to a kind of HVDC flywheel sychronising controlling party for realizing wind field frequency response described in any one of claim 1-3 Method, it is characterised in that: described method uses frequency mirror image control method for coordinating at sending end current conversion station further, it may be assumed that change in sending end Using capacitor direct current voltage and AC voltage magnitude as reference quantity in stream station, control sending end current conversion station output AC voltage Frequency and amplitude, thus maintain the wind field top-cross stream stabilization of power grids, it is simple to wind field accesses；Wherein:

Described method, on the basis of existing control method, is added from DC voltage to the mapping of AC frequency, by with described The cooperation of receiving end current conversion station flywheel sychronising control method, reflects wind field top-cross rapidly and accurately by the frequency of AC network on the bank In stream frequency, auxiliary wind field participates in frequency response.

HVDC flywheel sychronising control method for realizing wind field frequency response the most according to claim 4, its feature exists In: for the information of mains frequency on the bank representated by DC voltage amplitude is reflected in its AC frequency again, the sending end change of current FREQUENCY CONTROL of standing strategy is identical with receiving end current conversion station, it may be assumed that

$\frac{{\mathrm{\ω}}_{\sec }-{\mathrm{\ω}}_{nom}}{{\mathrm{\ω}}_{nom}}=K\frac{U_{dc}-U_{dc\_nom}}{U_{dc\_nom}}---\left(13\right)$

Wherein ω_secFor sending end current conversion station output AC frequency, ω_nomFor rated frequency, U_dcFor DC bus-bar voltage, U_{dc_n}Om is DC voltage rated value；

Unlike receiving end current conversion station, sending end current conversion station AC connect wind field by its frequency of phase locked loop fast lock with Phase angle, therefore the change of sending end current conversion station frequency will not directly influence the power of wind field output, only serves the work of transmission information With, in this way DC voltage change is again converted to frequency change, and identical owing to converting ratio, it is achieved from bank The frequency of upper AC network, to the Mirroring Mapping of wind field side a-c cycle, i.e. has ω_sec*=KU_dc*=ω_g*, asterisk represents deviation Rate.