CN114172203A - Control method for parallel power supply system of generator-network type MMC converter station - Google Patents

Control method for parallel power supply system of generator-network type MMC converter station Download PDF

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CN114172203A
CN114172203A CN202111520402.0A CN202111520402A CN114172203A CN 114172203 A CN114172203 A CN 114172203A CN 202111520402 A CN202111520402 A CN 202111520402A CN 114172203 A CN114172203 A CN 114172203A
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mmc
network
controller
generator
control method
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CN114172203B (en
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项中明
倪秋龙
李振华
徐建平
周正阳
周靖皓
吕勤
胡济恒
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State Grid Zhejiang Electric Power Co Ltd
Jinhua Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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State Grid Zhejiang Electric Power Co Ltd
Jinhua Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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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
    • 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
    • H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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]

Abstract

The invention discloses a control method for a parallel power supply system of a generator-network-type MMC converter station, which adopts an improved constant alternating voltage amplitude and frequency control strategy and adds an advanced correction auxiliary control link to an outer ring constant voltage controller of the network-type MMC so as to inhibit the low-frequency oscillation instability phenomenon of the system caused by the access of the traditional network-type MMC converter station and ensure the synchronous and stable operation of the power supply system and a power grid. The invention adopts parallel feedforward control, and ensures that the fault transient operation characteristic of the network-type MMC is unchanged by arranging an amplitude limiting link on an additional branch. After the method is used, the low-frequency oscillation instability phenomenon of the system is successfully inhibited, the advanced auxiliary controller has good robustness, and the method is applicable to the constant voltage controller parameters of the network-structured MMC within a certain range.

Description

Control method for parallel power supply system of generator-network type MMC converter station
Technical Field
The invention belongs to the technical field of power transmission and distribution of a power system, and particularly relates to a control method for a parallel power supply system of a generator-network type MMC converter station.
Background
With the rapid development of power electronic devices, a voltage source converter based flexible direct current (VSC-HVDC) technology is also widely used. Compared with a traditional direct current system based on a semi-controlled device, the VSC-HVDC has the advantages of flexible control, no need of providing phase-change voltage for a power grid, independent control of active power and reactive power, capability of providing synchronous alternating current power supply support for a passive network and the like, has the advantages of supplying power to the passive network, independent control of the active power and the reactive power, capability of flexibly realizing power flow reversal and the like, is widely applied to scenes such as new energy grid connection, interconnection among alternating current large power grids, offshore wind power access, a direct current power distribution network and the like, and has a huge development prospect; the modular multilevel converter MMC has the advantages that harmonic components are few, the power device series connection technology is not needed, and the like, and becomes a preferred voltage source converter in large-scale new energy base grid connection. Meanwhile, MMC-HVDC is used as an important asynchronous machine power supply, and can replace a synchronous machine power supply to supply power to a system in a future power system.
When the MMC-HVDC is used as an asynchronous machine power supply, two typical control strategies of a network following type and a network construction type are mainly adopted. The network following MMC usually adopts current vector control, an outer loop controller realizes decoupling control of active/passive quantity, an active control loop usually fixes active power, a reactive loop can adopt a fixed reactive power/alternating voltage control strategy, and a Phase Locked Loop (PLL) is adopted to track voltage of a grid-connected point so as to realize synchronization with an active power grid. The core idea of the network-forming MMC is to control the amplitude and the phase of the voltage of a grid-connected point, so that the inertia and the damping characteristic of a generator can be simulated, and the unique advantage is played when the passive network is supplied with power.
With the increase of the demand of electric energy and the increase of environmental protection pressure, the demand of clean energy is continuously increased, and the leading position of the power supply of the traditional synchronous machine is broken in the future. With the gradual replacement of the synchronous machine power supply by the non-synchronous machine power supply, the power supply system with the generator and the MMC converter station connected in parallel becomes an important power supply mode, compared with a network control strategy, the network-forming type MMC can operate as an independent voltage source and can provide inertial support for the system, and therefore the 100% replacement of the synchronous machine power supply can be realized theoretically. For the parallel power supply system of the generator-network-type MMC converter station shown in FIG. 1, a generator is connected with a grid-connected point of a network-type MMC through an alternating current transmission line, and the generator and the network-type MMC are connected in parallel to transmit power to a power grid through the alternating current transmission line. Under this scene, the outer loop voltage controller of network-forming MMC can produce the influence to the damping characteristic of generator, leads to the generator to produce low frequency oscillation, when voltage controller's parameter was selected unreasonablely, the unstable phenomenon of oscillation probably appeared in the system, is unfavorable for the steady operation of system. Therefore, additional research into control strategies for network-type MMC converter stations for power supply systems in parallel with generators is needed to achieve future stable and reliable power supply to the grid with generator-network-type MMC parallel power supply systems.
Disclosure of Invention
In view of the above, the present invention provides a control method for a parallel power supply system of a generator-network-type MMC converter station, which can eliminate negative damping torque of a generator caused by the access of a network-type MMC, ensure that the system does not have low-frequency oscillation instability, have good robustness, and simultaneously, do not affect the transient operation characteristics of the power supply system during a fault period.
A control method for a generator-network-type MMC converter station parallel power supply system is characterized in that a control strategy of constant alternating voltage amplitude and frequency is adopted for a network-type MMC in the system, and an advanced correction auxiliary control link is added into an outer ring constant voltage controller, namely, the maximum advanced phase provided by the auxiliary control link is determined according to the dominant low-frequency oscillation frequency of a generator, the advance time constant, the lag time constant and the gain constant of the outer ring constant voltage controller are determined according to the maximum advanced phase, the auxiliary control link is changed into a parallel connection mode, and an amplitude limiting link is added on an additional branch to ensure that the performance of the network-type MMC is kept unchanged during the fault transient state.
Furthermore, the d axis in the outer ring constant voltage controller adopts US ref-usdThe result is sequentially subjected to an advanced correction auxiliary control link and an outer ring PI controller to obtain an MMC output current d-axis instruction value isdrefQ axis is 0-usqThe result is sequentially subjected to an advanced correction auxiliary control link and an outer ring PI controller to obtain an MMC output current q-axis instruction value isqrefAnd then i will besdrefAnd isqrefAs a reference value for the MMC inner-loop current controller, where US refTo the grid-connected point voltage reference value, usdAnd usqThe component of the MMC grid-connected point is the d-axis component and the q-axis component of the MMC grid-connected point voltage respectively.
Further, the transfer function expression of the advanced correction auxiliary control link is as follows:
Figure BDA0003407093120000031
wherein: gC(s) is the transfer function of the lead correction auxiliary control element, KcIs a gain constant, T1And T2Respectively a lead time constant and a lag time constant, and s is a laplace operator.
Further, the advanced correction auxiliary control link is formed by connecting an original branch and an additional controller in parallel, namely GC(s)＝GX(s)+1，GC(s) is the transfer function of the lead corrected auxiliary control element, GX(s) transfer function of additional controller, table thereofThe expression is as follows:
Figure BDA0003407093120000032
wherein: kcIs a gain constant, T1And T2Respectively a lead time constant and a lag time constant, and s is a laplace operator.
Further, the lead time constant T1Hysteresis time constant T2And a gain constant KcThe calculation expression of (a) is as follows:
Figure BDA0003407093120000033
Figure BDA0003407093120000034
Figure BDA0003407093120000035
wherein: omegacIs the dominant angular frequency of oscillation of the generator,
Figure BDA0003407093120000036
the most advanced phase.
Further, the maximum advance phase
Figure BDA0003407093120000037
The calculation expression of (a) is as follows:
Figure BDA0003407093120000038
Figure BDA0003407093120000039
wherein:fcis the dominant oscillation frequency of the generator, KEAnd TERespectively a proportional coefficient and an integral coefficient of the outer loop PI controller,
Figure BDA00034070931200000310
for outer loop PI controllers at fcLagging phase provided at the frequency point.
Further, the clipping element is used for clipping the additional controller, and the output of the additional controller is limited to be between-0.05 p.u. and 0.05p.u.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the invention provides a feasible control strategy for the parallel power supply system of the generator-network-type MMC converter station, can avoid the phenomenon of low-frequency oscillation instability caused by the access of the network-type MMC, ensures the synchronous and stable operation of the power supply system and a power grid, and plays a certain guiding role in the design of future engineering.
2. The invention introduces an advanced correction auxiliary controller in an outer ring constant voltage controller of a network-structured MMC, the design of the controller is only related to the dominant oscillation frequency of the system and the constant voltage controller parameters of the MMC, and the controller is not influenced by the generator parameters and the network parameter structure; the method of the invention does not need to add extra devices, is simple to implement and has good economic benefit.
3. When the parameters of the constant voltage controller of the network-structured MMC change, the dominant oscillation frequency of the system also changes, and the set advanced correction auxiliary controller is kept unchanged, so that the low-frequency oscillation instability phenomenon of the system can not occur when the parameters of the constant voltage controller change within a certain range; therefore, the method has strong robustness, wide application range and extremely high engineering value.
4. When the output power instruction value of the network-type MMC changes, the output power of the network-type MMC can follow the instruction value, the power change is smooth, and the network-type MMC has an inertial response characteristic; therefore, the invention can ensure that the system does not generate low-frequency oscillation instability, has strong applicability and has great practical engineering significance.
5. When a short-circuit fault occurs at a grid-connected bus of the network-structured MMC, the parallel power supply system can realize fault ride-through, the system can recover stable operation after the fault is cleared, and the transient characteristic of the network-structured MMC is kept unchanged compared with the condition that an auxiliary control strategy is not adopted; therefore, the method is simple to implement, has strong applicability under various working conditions, and has great practical engineering significance.
Drawings
Fig. 1 is a schematic diagram of a topology structure of a generator-network type MMC converter station parallel power supply system.
FIG. 2 is a schematic diagram of a network-forming MMC outer-loop control using an advanced calibration auxiliary controller according to the present invention.
Fig. 3 is a waveform diagram of rotor angular frequency of the generator under the condition of changing an integral constant of a network type MMC constant voltage controller when an auxiliary controller is not adopted.
FIG. 4 is a waveform of the rotor angular frequency of the generator when the constant voltage controller parameters are changed while the auxiliary controller parameters remain unchanged after the control method of the present invention is employed.
FIG. 5 is a waveform diagram of power delivered by an MMC converter station when a power command value of a network-type MMC converter station is changed by using the control method of the present invention.
FIG. 6 is a waveform diagram of currents of d and q axes of an MMC under the condition that a three-phase metallic grounding short-circuit fault occurs at a grid-connected point bus of a grid-connected MMC converter station after the control method of the present invention is adopted.
Detailed Description
In order to more specifically describe the present invention, the following detailed description is provided for the technical solution of the present invention with reference to the accompanying drawings and the specific embodiments.
As shown in fig. 2, the control strategy for the parallel power supply system of the generator-grid type MMC converter station of the present invention includes the following steps:
(1) for the network-forming MMC current converter, an improved control strategy of constant alternating voltage amplitude and frequency is adopted, and an advanced correction auxiliary control link is added into a constant voltage controller.
Setting a network-forming MMC outer-loop controller to respectively determine d-axis and q-axis reference voltages of a grid-connected point, wherein the transfer function form of the additional feedforward advanced correction controller is as follows:
Figure BDA0003407093120000051
(2) for a generator-network type MMC parallel power supply system, the maximum leading phase provided by an auxiliary controller is firstly determined according to the dominant low-frequency oscillation frequency of a generator.
If feedforward control is not adopted, the dominant oscillation frequency of the generator is fcAnd network-forming type MMC outer ring constant voltage controller GERespectively, is KE、TEIf the network-forming type MMC outer ring controller is in fcAt the provided lagging phase
Figure BDA0003407093120000052
Comprises the following steps:
Figure BDA0003407093120000053
accordingly, the lead correction controller G is determinedc(s) maximum lead phase provided
Figure BDA0003407093120000054
Comprises the following steps:
Figure BDA0003407093120000055
(3) and for the network-structured MMC current converter, the lead time constant, the lag time constant and the gain constant of the controller are determined according to the maximum lead phase.
Let advance correct the controller Gc(s) has lead and lag time constants of T1、T2Gain factor K of the controllercAccording to the maximum lead phase
Figure BDA0003407093120000056
And dominant oscillation angular frequency ωcSeparately calculating the parameter T1、T2And Kc：
Figure BDA0003407093120000061
Figure BDA0003407093120000062
Figure BDA0003407093120000063
(4) For the network type MMC current converter, an advanced correction controller is changed into a parallel connection mode, and an amplitude limiting link is added on an additional branch to ensure that the performance of the network type MMC is kept unchanged during the fault transient state.
The calculated lead correction controller Gc(s) is changed into a parallel form, and the two parallel branches are respectively an original branch and an additional branch GX(s), namely:
GC(s)＝GX(s)+1
Figure BDA0003407093120000064
in the additional controller GXThe limiting link is arranged on the(s), and the maximum output and the minimum output of the limiting link are limited to 0.05p.u. and-0.05 p.u., so that the G is ensured to be in case of serious system failureX(s) will soon reach the clipping value.
The output result of the outer ring voltage controller is used as the reference value of the MMC inner ring current controller, the design method of the inner ring current controller is basically the same as that of the inner ring current controller of the traditional MMC, and the maximum output and the minimum output of the MMC inner ring current amplitude limiting link can be limited to be near 1.2p.u. and-1.2 p.u.
The generator-network-construction-type MMC parallel power supply system adopted in the embodiment is shown in fig. 1, wherein a generator is connected with a grid-connected point of an MMC through an alternating current transmission line and is connected to a power grid through another transmission line in a parallel mode; the rated capacity of the generator is 400MVA, the rated direct-current voltage of the MMC converter station is 400kV, the rated transmission power is 400MW, and the specific parameters of a main loop of the system are shown in Table 1.
TABLE 1
Figure BDA0003407093120000065
Figure BDA0003407093120000071
(1) Under the steady state operation state, the network-building type MMC adopts the control mode of the amplitude and the phase of the alternating voltage of the fixed grid-connected point. As shown in FIG. 2, wherein Us refTo the grid-connected point voltage reference value, usd、usqThe voltage components of the grid-connected point d-axis and q-axis, isdref、isqrefRespectively representing d-axis component reference values and q-axis component reference values of MMC output current; the output active power of the generator is 200MW, the MMC operates as an inverter station, and the output active power is 200 MW. In the initial state, the proportion/integral constant of the MMC constant voltage controller is selected as KE＝2，TEWhen the frequency is 0.03, the system generates a low-frequency oscillation phenomenon with the dominant frequency of 1.25 Hz; on the basis of the traditional control strategy, the advanced correction auxiliary control shown in figure 2 is adopted, and G is obtained through parameter settingcThe expression of(s) is:
Figure BDA0003407093120000072
(2) adopting parallel type lead correction control, adding branch GX(s) the expression is:
Figure BDA0003407093120000073
in the additional controller GXAnd(s) a limiting link is arranged, and the maximum output and the minimum output of the limiting link are limited to 0.05p.u. and-0.05 p.u.. Will be outsideThe output result of the ring voltage controller is used as the reference value of the MMC inner ring current controller, the design method of the inner ring current controller is basically the same as that of the inner ring current controller of the traditional MMC, and the maximum output and the minimum output of the MMC inner ring current amplitude limiting link are limited to be near 1.2p.u. and-1.2 p.u.
(3) Under the condition of adopting a traditional control strategy, the network-structured MMC adopts fixed grid-connected point alternating-current voltage amplitude and phase control, and at the moment, the integral constant T of the MMC fixed voltage controller is changedE0.025, 0.05 and 0.15 respectively, and the rotor angular frequency waveform of the generator is shown in fig. 3.
(4) Under the condition of adopting the control strategy of the invention, the fixed voltage controller of the network-structured MMC is added with the advanced correction auxiliary control, and the parameters of the controller are set according to the steps (1) to (2). At the moment, the integral constant T of the MMC constant voltage controller is changedE0.025, 0.05 and 0.15, respectively, and T is equal to T when a conventional control strategy is adoptedEIn a 0.05-hour formation-type MMC comparison, the rotor angular frequency waveform of the generator is shown in fig. 4.
(5) And the simulation of the power step is carried out under the condition of adopting the control strategy of the invention. At the 15 th s, the power command value of the network-type MMC is set to be increased from 0.5p.u. to 0.55p.u., and at the 30 th s, the power command value of the MMC is set to be decreased from 0.55p.u. to 0.5p.u., and the power reference value is selected to be 400MW, so that the actual output power waveform of the MMC is as shown in fig. 5.
(6) Under the condition of adopting the control strategy, for the simulation of the fault, the three-phase metallic grounding short circuit fault at the grid-connected point of the network-structured MMC is set, and the fault duration is 0.1 s; compared with the network-structured MMC adopting the traditional control strategy, the waveforms of d-axis and q-axis components per unit of output current are shown in FIG. 6.
For the above example, it can be seen from fig. 3 and 4 that when the conventional control method is adopted, the generator rotor has low-frequency oscillation phenomenon, when T isEAt 0.03, 0.05 and 0.15, the damping torque of the generator is negative and the system may exhibit low frequency oscillation instability. When the control strategy of the invention is adopted, the damping torque of the generator is changed from negative to positive, and the low-frequency oscillation instability phenomenon of the system can not occur, thereby proving that the auxiliary control adopted by the inventionThe strategy is effective in inhibiting low-frequency oscillation of the system and ensuring stable operation of the system. And the simulation result of fig. 4 shows that under the condition that the parameters of the advanced correction auxiliary controller which is well defined and remains unchanged are adopted, the parameters of the network-forming type MMC constant voltage loop are changed within a certain range, and the low-frequency oscillation instability of the system can be avoided by adopting an auxiliary control strategy, so that the control method has good robustness and adaptability. The simulation result of fig. 5 illustrates that when the MMC power command value changes, its output power can change smoothly and track the command value, and has an inertial response characteristic on the basis of keeping stable operation, so that it can provide an inertia support for the system. The simulation results of fig. 6 illustrate that the generator-MMC parallel power supply system is able to ride through the most severe three-phase metallic short-circuit fault, and it can be seen that the MMC employing the conventional control method and the inventive control strategy has almost the same response characteristics during the fault transient, indicating that the advanced corrective auxiliary control strategy does not affect the response characteristics during the system fault transient. The above simulation results illustrate the effectiveness of the present invention.
The embodiments described above are presented to enable a person having ordinary skill in the art to make and use the invention. It will be readily apparent to those skilled in the art that various modifications to the above-described embodiments may be made, and the generic principles defined herein may be applied to other embodiments without the use of inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications to the present invention based on the disclosure of the present invention within the protection scope of the present invention.

Claims (8)

1. A control method for a generator-network type MMC converter station parallel power supply system is characterized by comprising the following steps: a control strategy of fixing alternating voltage amplitude and frequency is adopted for a network-forming type MMC in a system, and an advanced correction auxiliary control link is added into an outer ring constant voltage controller, namely, the maximum advanced phase provided by the auxiliary control link is firstly determined according to the leading low-frequency oscillation frequency of a generator, the advance time constant, the lag time constant and the gain constant of the outer ring constant voltage controller are then determined according to the maximum advanced phase, finally, the auxiliary control link is changed into a parallel connection mode, and an amplitude limiting link is added on an additional branch to ensure that the performance of the network-forming type MMC is kept unchanged during the fault transient state.
2. The control method according to claim 1, characterized in that: the d axis in the outer ring constant voltage controller adopts US ref-usdThe result is sequentially subjected to an advanced correction auxiliary control link and an outer ring PI controller to obtain an MMC output current d-axis instruction value isdrefQ axis is 0-usqThe result is sequentially subjected to an advanced correction auxiliary control link and an outer ring PI controller to obtain an MMC output current q-axis instruction value isqrefAnd then i will besdrefAnd isqrefAs a reference value for the MMC inner-loop current controller, where US refTo the grid-connected point voltage reference value, usdAnd usqThe component of the MMC grid-connected point is the d-axis component and the q-axis component of the MMC grid-connected point voltage respectively.
3. The control method according to claim 1, characterized in that: the transfer function expression of the lead correction auxiliary control link is as follows:
Figure FDA0003407093110000011
wherein: gC(s) is the transfer function of the lead correction auxiliary control element, KcIs a gain constant, T1And T2Respectively a lead time constant and a lag time constant, and s is a laplace operator.
4. The control method according to claim 1, characterized in that: the advanced correction auxiliary control link is formed by connecting an original branch and an additional controller in parallel, namely GC(s)＝GX(s)+1，GC(s) is the transfer function of the lead corrected auxiliary control element, GX(s) is the transfer function of the additional controller, expressed as follows：
Figure FDA0003407093110000012
Wherein: kcIs a gain constant, T1And T2Respectively a lead time constant and a lag time constant, and s is a laplace operator.
5. The control method according to claim 3 or 4, characterized in that: the lead time constant T1Hysteresis time constant T2And a gain constant KcThe calculation expression of (a) is as follows:
Figure FDA0003407093110000021
Figure FDA0003407093110000022
Figure FDA0003407093110000023
wherein: omegacIs the dominant angular frequency of oscillation of the generator,
Figure FDA0003407093110000024
the most advanced phase.
6. The control method according to claim 5, characterized in that: the maximum lead phase
Figure FDA0003407093110000025
The calculation expression of (a) is as follows:
Figure FDA0003407093110000026
Figure FDA0003407093110000027
wherein: f. ofcIs the dominant oscillation frequency of the generator, KEAnd TERespectively a proportional coefficient and an integral coefficient of the outer loop PI controller,
Figure FDA0003407093110000028
for outer loop PI controllers at fcLagging phase provided at the frequency point.
7. The control method according to claim 4, characterized in that: the amplitude limiting link is used for limiting the amplitude of the additional controller, and the output of the additional controller is limited to be between-0.05 p.u. and 0.05p.u.
8. The control method according to claim 1, characterized in that: the control method adopts an improved constant alternating voltage amplitude and frequency control strategy, and adds an advanced correction auxiliary control link to an outer ring constant voltage controller of the network-structured MMC, so that the low-frequency oscillation instability phenomenon of a system caused by the access of a converter station of the traditional network-structured MMC is inhibited, and the synchronous and stable operation of a power supply system and a power grid is ensured; meanwhile, parallel feedforward control is adopted, and an amplitude limiting link is arranged on an additional branch, so that the fault transient operation characteristic of the networking MMC is guaranteed to be unchanged.
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CN114583743A (en) * 2022-03-23 2022-06-03 国网经济技术研究院有限公司 Control method of offshore wind power uncontrolled rectification direct current transmission system
CN114583743B (en) * 2022-03-23 2022-11-22 国网经济技术研究院有限公司 Control method of offshore wind power uncontrolled rectification direct current transmission system
CN115800340A (en) * 2022-10-28 2023-03-14 中国电力科学研究院有限公司 Amplitude limiting control method and system for enhancing transient stability of network-type VSC (Voltage Source converter)

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