Intelligent calculation center direct-current power transmission system based on offshore wind power and control method

Abstract

According to the intelligent calculation center direct-current power transmission system based on offshore wind power and the control method, offshore wind power serves as a power supply of an offshore intelligent calculation center, wind power output fluctuation is stabilized through an energy storage system, and residual electric energy is transmitted to an onshore power grid through a flexible direct-current power transmission system; the flexible direct-current power transmission system can be used for reversely supplying power to the offshore intelligent computing system under the working condition that the wind power plant stops running; through cooperative control of the wind power system, the flexible direct-current power transmission system, the energy storage system, the diesel generator and other systems, stable operation of the offshore intelligent calculation center under different working conditions can be achieved, a solution is provided for electrical system design of the remote offshore intelligent calculation center, and remarkable economic benefits and good application prospects are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy power generation, and particularly relates to a DC power transmission system and a control method of an intelligent computing center based on far-sea wind power. BACKGROUND

[0002] With the vigorous development of the new energy industry, wind power generation gradually moves from land to sea and moves towards the deep sea. The rapid development of offshore wind power will conflict with the lagging land power transmission capacity. In the future, as more offshore wind farms are completed, the offshore wind power transmission channel will face a shortage problem.

[0003] The intelligent computing center is a new type of infrastructure focusing on artificial intelligence and big data computing. In recent years, the artificial intelligence industry has developed rapidly and started to grow in size explosively, and the computing power demand has surged. The intelligent computing center develops towards specialization and scale. The construction of the intelligent computing center at sea not only can locally consume green power and reduce the pressure on the power transmission channel, but also can effectively reduce the system energy consumption by using the large seawater flow to cool the data cabin.

[0004] Flexible DC power transmission has the advantages of flexible control and no limitation on transmission distance, and is suitable as a power transmission scheme of the intelligent computing center system based on far-sea wind power. The offshore intelligent computing center belongs to a load with high demand for power stability. If the power grid stability is poor and frequent fluctuations occur, it will affect the service life and operating performance of the intelligent computing center equipment. However, due to the very complex environmental conditions faced by offshore wind power, the power generation output has strong randomness and volatility, and the stability of the conventional offshore wind power DC transmission scheme of the offshore AC power grid completely relies on the offshore MMC converter, so it is difficult to ensure that the offshore wind power DC transmission scheme meets the requirements of the intelligent computing center system on power transmission stability under different working conditions. In summary, there is a certain contradiction between the high reliability requirement of the offshore intelligent computing center for the power supply system and the fluctuating output of the wind power and the existing offshore wind power DC transmission scheme. At present, there is still a lack of effective solutions. SUMMARY

[0005] The purpose of the present application is to provide a DC power transmission system and a control method of an intelligent computing center based on far-sea wind power, to solve the problem of contradiction between the high reliability requirement of the offshore intelligent computing center for the power supply system and the fluctuating output of the offshore wind power and the existing offshore wind power DC transmission scheme, to improve the reliability of offshore wind power as a power supply for a far-sea offshore intelligent computing center, and to enable the offshore intelligent computing center to operate stably under different working conditions of offshore wind power.

[0006] To achieve the above-mentioned purpose of the application, according to the first aspect of the present application, the present application adopts the following technical scheme:

[0007] The application discloses a DC power transmission system of an intelligent calculation center based on far-sea wind power, and relates to the technical field of power transmission.

[0008] The offshore wind power generator is connected with the wind turbine transformer through the wind turbine side converter and the wind turbine grid side converter, is connected with the offshore AC bus through the offshore collection submarine cable after being boosted, the energy storage battery is connected with the energy storage transformer through the energy storage grid-connected converter, is connected with the offshore AC bus after being boosted through the energy storage transformer, the diesel generator and the offshore intelligent calculation center power supply system and the offshore station power supply system are connected with the offshore intelligent calculation center bus, are connected with the offshore AC bus after being boosted through the offshore intelligent calculation center transformer, and the offshore intelligent calculation center buses are connected through the offshore intelligent calculation center bus tie switch.

[0009] To achieve the above-mentioned application purposes, according to the second aspect of the application, the application adopts the following technical scheme.

[0010] A control method of a DC power transmission system of an intelligent calculation center based on far-sea wind power, and relates to the technical field of power transmission.

[0011] Under the normal operation condition of the DC power transmission system of the intelligent calculation center, the onshore MMC converter station adopts the constant DC bus voltage and reactive power control strategy, and the control target is to keep the DC transmission submarine cable voltage stable; the offshore MMC converter station adopts the constant AC grid voltage control strategy, and is responsible for controlling the offshore AC bus voltage; the energy storage grid-connected converter adopts the following control strategy: when the wind power generation power is greater than the sum of the offshore intelligent calculation center power consumption load and the offshore station power consumption load, the energy storage battery is charged at the rated power until it is fully charged, when the wind power generation power is less than the sum of the offshore intelligent calculation center power consumption load and the offshore station power consumption load, active power is output according to the power shortage to supply power for the offshore intelligent calculation center power consumption load and the offshore station power consumption load; the wind turbine side converter adopts the maximum power tracking control strategy, the wind speed is detected in real time, and the maximum power generation curve is tracked, so that the wind power generator can track the maximum power point operation under different wind speeds; the wind turbine grid side converter adopts the constant DC bus voltage and reactive power control strategy, and the control target is to maintain the wind turbine DC bus voltage stable.

[0012] When the wind farm is shut down and the flexible DC transmission system is operating normally, both the wind turbine-side converter and the grid-side converter are shut down. The onshore MMC converter station adopts a constant DC bus voltage and reactive power control strategy, with the control objective being to maintain a stable DC transmission cable voltage. The offshore MMC converter station adopts a constant AC grid voltage control strategy, responsible for controlling the offshore AC bus voltage. The energy storage grid-connected converter adopts a constant power control strategy, controlling the energy storage battery output power to be zero. Under this condition, the power load of the offshore intelligent computing center and the offshore station is supplied through the flexible DC transmission system.

[0013] Under the condition that the flexible DC transmission system is shut down and the wind farm is operating normally, both the onshore MMC converter station and the offshore MMC converter station are shut down; the energy storage grid-connected converter adopts a virtual synchronous machine control strategy to control the offshore AC bus voltage; the wind turbine-side converter adopts a constant power control strategy, and its active power command is given according to the power load of the offshore intelligent computing center and the offshore station; the wind turbine grid-side converter adopts a constant DC bus voltage and reactive power control strategy, and the control objective is to maintain the stability of the wind turbine DC bus voltage;

[0014] When both the wind farm and the flexible DC transmission system are shut down, the wind turbine-side converter, grid-side converter, onshore MMC converter station, and offshore MMC converter station are all shut down. The energy storage grid-connected converter adopts a virtual synchronous machine control strategy to control the offshore AC bus voltage. If the energy storage battery is depleted and insufficient to support the normal operation of the offshore intelligent computing center and offshore station's power load, the diesel generator will be put into operation to supply power to the offshore intelligent computing center and offshore station's power load.

[0015] Furthermore, the control system for implementing the virtual synchronous machine control strategy of the energy storage grid-connected converter includes: a virtual synchronous machine mechanical module, a virtual synchronous machine excitation module, a voltage outer loop controller, a current inner loop controller, a Park inverse transformation module, and a modulation module; in the virtual synchronous machine mechanical module, the reference phase θ is calculated according to the following method. b :

[0016] θ b (k+1)=∫ω b (k+1)dt

[0017]

[0018] Where, θ b (k+1) is the reference phase for the next sampling period, ω b (k+1) is the angular frequency of the next sampling period, ω b (k) is the angular frequency of this sampling period, ω n P is the rated angular frequency. bref P is the active power reference value. b(k) is the active power of the present sampling period, J is the virtual rotor moment of inertia, D p is the active damping coefficient;

[0019] In the virtual synchronous machine excitation module, the d-axis voltage reference value u bdref is calculated according to the following method:

[0020]

[0021] wherein u bdref (k+1) is the d-axis voltage reference value of the next sampling period, |U b (k) | is the voltage amplitude of the present sampling period, U ref is the voltage amplitude reference value, Q bref is the reactive power reference value, Q b (k) is the reactive power of the present sampling period, K is the virtual excitation coefficient, D q is the reactive damping coefficient.

[0022] By adopting the technical scheme of the present application, offshore wind power is used as the power supply of the offshore intelligent computing center, the energy storage system is used to suppress wind power output fluctuation, the diesel generator is used as the standby power supply, the flexible DC power transmission system is used to transmit the remaining power to the onshore power grid, and the flexible DC power transmission system can also be used to supply power to the offshore intelligent computing system in reverse in the shutdown condition of the wind farm; through the collaborative control of the wind power system, the flexible DC power transmission system, the energy storage system and the diesel generator, the stable operation of the offshore intelligent computing center in different conditions can be realized, and a solution is provided for the electrical system design of the long-distance offshore intelligent computing center. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a typical topology diagram of the DC power transmission system of the intelligent computing center based on offshore wind power of the present application.

[0024] Figure 2 is a typical topology diagram of the wind turbine side converter in the present application.

[0025] Figure 3 is a typical topology diagram of the wind turbine side converter, the energy storage grid-connected converter in the present application.

[0026] Figure 4 is a typical topology diagram of the offshore MMC converter station and the onshore MMC converter station in the present application.

[0027] Figure 5 is a specific example system principle diagram of the onshore MMC converter station control method in the present application.

[0028] Figure 6 is a specific example system principle diagram of the offshore MMC converter station control method in the present application.

[0029] Figure 7 This is a schematic diagram of a specific example system of the virtual synchronous machine control method used in the energy storage grid-connected converter of the present invention. Detailed Implementation

[0030] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] In this embodiment of the invention, the intelligent computing center DC transmission system based on offshore wind power is as follows: Figure 1 As shown, it includes an offshore wind turbine 1, a wind turbine-side converter 2, a wind turbine grid-side converter 3, a wind turbine transformer 4, an offshore collection cable 5, an offshore AC busbar 6, an energy storage transformer 7, an energy storage grid-connected converter 8, an energy storage battery 9, an offshore intelligent computing center transformer 10, a diesel generator 11, an offshore intelligent computing center power supply system 12, an offshore station power supply system 13, an offshore intelligent computing center busbar 14, an offshore intelligent computing center bus tie switch 15, an offshore connection transformer 16, an offshore MMC converter station 17, a DC transmission cable 18, an onshore MMC converter station 19, an onshore connection transformer 20, and an onshore AC power grid 21.

[0032] In this embodiment of the invention, the offshore wind turbine 1 is connected to the wind turbine transformer 4 via the turbine-side converter 2 and the wind turbine grid-side converter 3. After voltage boosting, it is connected to the offshore AC bus 6 via the offshore collection cable 5. The energy storage battery 9 is connected to the energy storage transformer 7 via the energy storage grid-connected converter 8. After voltage boosting by the energy storage transformer 7, it is connected to the offshore AC bus 6. The diesel generator 11, the offshore intelligent computing center power supply system 12, and the offshore station power supply system 13 are all connected to the offshore intelligent computing center bus 14. After being stepped up by transformer 10, the voltage is connected to the offshore AC bus 6. The two sets of offshore intelligent computing center buses 14 are connected by offshore intelligent computing center bus tie switch 15. The AC side of the offshore MMC converter station 17 is connected to the offshore AC bus 6 after being transformed by offshore connection transformer 16, and the DC side is connected to the DC transmission submarine cable 18. The DC transmission submarine cable 18 is connected to the DC side of the onshore MMC converter station 19 on the land side. The AC side of the onshore MMC converter station 19 is connected to the onshore AC power grid 21 after being transformed by onshore connection transformer 20.

[0033] In this embodiment of the invention, the energy storage grid-connected converter 8 adopts the following... Figure 3The diagram shows a three-phase six-arm bridge topology. Under normal operating conditions, the energy storage grid-connected converter 8 employs the following control strategy: when the wind farm's power generation exceeds the load of the offshore intelligent computing center and offshore station, it charges the energy storage battery at rated power until fully charged; when the wind farm's power generation is less than the load of the offshore intelligent computing center and offshore station, it outputs active power according to the power deficit to supply power to the load of the offshore intelligent computing center and offshore station. When the wind farm is out of service and the flexible DC transmission system is operating normally, the energy storage grid-connected converter 8 employs a constant power control strategy, controlling the energy storage battery's output power to zero; when the flexible DC transmission system is out of service, the energy storage grid-connected converter 8 employs a virtual synchronous machine control strategy, responsible for controlling the offshore AC bus voltage, such as... Figure 7 As shown, the control system for implementing the virtual synchronous machine control strategy includes: a virtual synchronous machine mechanical module 301, a virtual synchronous machine excitation module 302, a voltage outer loop controller 303, a current inner loop controller 304, a Park inverse transformation module 305, and a modulation module 306.

[0034] In the virtual synchronizer mechanical module 301, the reference phase θ is calculated according to the following method. b :

[0035] θ b (k+1)=∫ω b (k+1)dt

[0036]

[0037] Where, θ b (k+1) is the reference phase for the next sampling period, ω b (k+1) is the angular frequency of the next sampling period, ω b (k) is the angular frequency of this sampling period, ω n P is the rated angular frequency. bref P is the active power reference value. b (k) represents the active power in this sampling period, J represents the virtual rotor moment of inertia, and D... p This is the active damping coefficient.

[0038] In the virtual synchronous machine excitation module 302, the d-axis voltage reference value u is calculated according to the following method. bdref :

[0039]

[0040] Among them, u bdref (k+1) is the d-axis voltage reference value for the next sampling period, |U b (k)| represents the voltage amplitude during this sampling period, U ref Q is the reference value for voltage amplitude. brefQ is the reactive power reference value b (k) is the reactive power of the current sampling period, k is the virtual excitation coefficient, D q is the reactive power damping coefficient.

[0041] In the embodiment of the application, the onshore MMC converter station 19 adopts a symmetric monopolar MMC topology structure, a topology diagram of which is shown in Figure 4 The onshore MMC converter station 19 adopts a constant DC bus voltage and reactive power control strategy, and the control target is to maintain the stability of the DC outgoing submarine cable voltage. As shown in Figure 5 In the embodiment of the application, the control system of the onshore MMC converter station 19 includes: an onshore converter station DC bus voltage and reactive power control module 101, an onshore converter station current control module 102, an onshore converter station Park inverse transformation module 103, an onshore converter station internal circulating current control module 104, and an onshore converter station bridge arm voltage calculation module 105.

[0042] The onshore converter station DC bus voltage and reactive power control module 101 is implemented as follows:

[0043]

[0044] Wherein: F PI1 (s) is the transfer function of the first PI controller, k p1 is the proportional coefficient, k i1 is the integral coefficient, i gdref2 , i gqref2 correspond to the d-axis and q-axis components of the current vector I gdqref2 , U dc2ref is the DC bus voltage reference value, U dc2 is the DC bus voltage, Q g2ref is the reactive power reference value, Q g2 is the reactive power.

[0045] The onshore converter station current control module 102 is implemented as follows:

[0046]

[0047] Wherein: F PI2 (s) is the transfer function of the second PI controller, k p2 is the proportional coefficient, k i2 is the integral coefficient, u difd2 , u difq2 correspond to the d-axis and q-axis components of the voltage vector U difdq2 , u gd , u gq correspond to the d-axis and q-axis components of the voltage vector U gdqd-axis, q-axis components of the current vector I gd2 , gq2 correspond to the d-axis, q-axis components of the voltage vector U gdq2 g correspond to the d-axis, q-axis components of the voltage vector U g L is the filter inductance.

[0048] The implementation of the onshore converter station internal circulating current control module 104 is as follows:

[0049]

[0050] wherein F SOGI (s) is the transfer function of the second-order generalized integrator, k g is the gain coefficient, and ω c is the cutoff frequency, in the embodiment of the application, the resonance frequency of the second-order generalized integrator is selected as ±100Hz, and the cutoff frequency is selected as 12Hz; u coma2 , comb2 and u comc2 correspond to the a-axis, b-axis and c-axis components of the voltage vector U comabc2 ca2 , cb2 and i cc2 correspond to the a-axis, b-axis and c-axis components of the current vector I cabc2 .

[0051] In the embodiment of the application, the offshore MMC converter station 17 adopts a symmetric monopolar MMC topology structure, the topology diagram of which is shown in Figure 4 , and is divided into three-phase upper and lower, i.e., six bridge arms, each of which contains a plurality of sub-modules in series. The offshore MMC converter station 17 adopts a fixed AC grid voltage control strategy. As shown in Figure 6 , in the embodiment of the application, the control system of the offshore MMC converter station 17 includes: an offshore converter station voltage control module 201, an offshore converter station current control module 202, an offshore converter station Park inverse transformation module 203, an offshore converter station internal circulating current control module 204, and an offshore converter station bridge arm voltage calculation module 205.

[0052] The implementation of the offshore converter station voltage control module 201 is as follows:

[0053]

[0054] wherein F PI3 (s) is the transfer function of the third PI controller, k p3 is the proportional coefficient, and k i3 is the integral coefficient, i gdref3 , gqref3 correspond to the a-axis, b-axis and c-axis components of the current vector I gdqref3 ​​d-axis, q-axis components of the voltage reference vector U gdref3 d-axis, q-axis components of the voltage reference vector U gqref3 d-axis, q-axis components of the voltage reference vector U gdqref3 d-axis, q-axis components of the voltage reference vector U gd3 d-axis, q-axis components of the voltage reference vector U gq3 d-axis, q-axis components of the voltage reference vector U gdq3 d-axis, q-axis components of the voltage reference vector U

[0055] The specific implementation manners of the offshore converter station current control module 202 and the offshore converter station internal circulating current control module 204 are consistent with those of the onshore converter station current control module 102 and the onshore converter station internal circulating current control module 104.

[0056] In the embodiment of the application, the fan machine-side converter 2 adopts a three-phase six-bridge-arm topological structure as shown in Figure 2 The control strategy of the fan machine-side converter 2 adopts double-loop control of a power outer loop and a current inner loop, and the output of the power outer loop is taken as the current reference value of the current inner loop after being subjected to an amplitude limiting link. Under the normal operation condition of the entire system, the fan machine-side converter 2 adopts a maximum power tracking control strategy, tracks the maximum power generation curve by detecting the wind speed in real time, and enables the wind driven generator to track the maximum power point to operate under different wind speeds; under the normal operation condition of the wind farm when the flexible DC power transmission system is shut down, the fan machine-side converter 2 adopts a constant power control strategy, and the active power instruction is given according to the offshore intelligent calculation center and the offshore station power load.

[0057] In the embodiment of the application, the fan grid-side converter 3 adopts a three-phase six-bridge-arm topological structure as shown in Figure 3 The control strategy of the fan grid-side converter 3 adopts double-loop control of a DC bus voltage and reactive power control outer loop and a current inner loop, and the output of the DC bus voltage and reactive power outer loop is taken as the current reference value of the current inner loop after being subjected to an amplitude limiting link. Under different operation modes, the fan grid-side converter 3 adopts a constant DC bus voltage and reactive power control strategy, and the control target is to maintain the stability of the fan DC bus voltage.

[0058] In the embodiment of the application, under the condition that the wind farm and the flexible DC power transmission system are both shut down, if the energy storage battery is depleted and cannot support the normal operation of the offshore intelligent calculation center and the offshore station power load, the diesel generator is put into operation to supply power to the offshore intelligent calculation center and the offshore station power load.

[0059] The above description of the embodiments is to assist those of ordinary skill in the art to understand and apply the present application. Those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments, and improvements and modifications made to the present application by those skilled in the art based on the disclosure of the present application should be within the scope of protection of the present application.

Claims

1. A DC power transmission system based on an intelligent center for far sea wind power, characterized in that, Comprise: Offshore wind turbine, wind turbine side converter, wind turbine grid side converter, wind turbine transformer, offshore collection submarine cable, offshore AC bus, energy storage transformer, energy storage grid-connected converter, energy storage battery, offshore intelligent center transformer, diesel generator, offshore intelligent center power supply system, offshore station power supply system, offshore intelligent center bus, offshore intelligent center bus tie switch, offshore coupling transformer, offshore MMC converter station, DC transmission submarine cable, onshore MMC converter station, onshore coupling transformer, onshore AC power grid; The offshore wind turbine is connected with the wind turbine transformer through the wind turbine side converter and the wind turbine grid side converter, is connected into the offshore AC bus through the offshore collection submarine cable after being boosted, the energy storage battery is connected into the energy storage transformer through the energy storage grid-connected converter, is connected into the offshore AC bus after being boosted through the energy storage transformer, the diesel generator and the offshore intelligent center power supply system, the offshore station power supply system are connected into the offshore intelligent center bus, are connected into the offshore AC bus after being boosted through the offshore intelligent center transformer, and the offshore intelligent center bus ties are connected through the offshore intelligent center bus tie switch between groups of offshore intelligent center buses;The AC side of the offshore MMC converter station is connected with the offshore AC bus after being boosted through the offshore coupling transformer, the DC side is connected with the DC transmission submarine cable, the DC transmission submarine cable is connected with the DC side of the onshore MMC converter station on the onshore side, and the AC side of the onshore MMC converter station is connected into the onshore AC power grid after being boosted through the onshore coupling transformer.

2. The control method of the offshore wind power-based intelligent center DC transmission system according to claim 1, characterized in that: Under the normal operation condition of the intelligent center DC transmission system, the onshore MMC converter station adopts the constant DC bus voltage and reactive power control strategy, and the control target is to keep the DC transmission submarine cable voltage stable;The offshore MMC converter station adopts the constant AC grid voltage control strategy and is responsible for controlling the offshore AC bus voltage;The energy storage grid-connected converter adopts the following control strategy: when the wind farm power generation power is greater than the sum of the offshore intelligent center power load and the offshore station power load, the energy storage battery is charged at the rated power until it is fully charged, when the wind farm power generation power is less than the sum of the offshore intelligent center power load and the offshore station power load, the active power is output according to the power shortage to supply power for the offshore intelligent center power load and the offshore station power load;The wind turbine side converter adopts the maximum power tracking control strategy, detects the wind speed in real time, and tracks the maximum power generation curve, so that the wind turbine can track the maximum power point operation under different wind speeds;The wind turbine grid side converter adopts the constant DC bus voltage and reactive power control strategy, and the control target is to maintain the wind turbine DC bus voltage stable. In the case that the wind farm is shut down and the flexible HVDC system is in normal operation, both the wind turbine side converter and the grid side converter are shut down; the onshore MMC converter station adopts the constant DC bus voltage and reactive power control strategy, and the control target is to keep the DC voltage of the submarine cable stable; the offshore MMC converter station adopts the constant AC grid voltage control strategy, and is responsible for controlling the offshore AC bus voltage; the energy storage grid-connected converter adopts the constant power control strategy, and controls the output power of the energy storage battery to be zero; in this case, the offshore intelligent computing center and the offshore station power load are powered through the flexible HVDC system; In the case that the flexible HVDC system is shut down and the wind farm is in normal operation, both the onshore MMC converter station and the offshore MMC converter station are shut down; the energy storage grid-connected converter adopts the virtual synchronous machine control strategy, and is responsible for controlling the offshore AC bus voltage; the wind turbine side converter adopts the constant power control strategy, and the active power instruction is given according to the offshore intelligent computing center and the offshore station power load; the wind turbine grid side converter adopts the constant DC bus voltage and reactive power control strategy, and the control target is to maintain the stability of the wind turbine DC bus voltage; In the case that both the wind farm and the flexible HVDC system are shut down, the wind turbine side converter, the grid side converter, the onshore MMC converter station and the offshore MMC converter station are all shut down; the energy storage grid-connected converter adopts the virtual synchronous machine control strategy, and is responsible for controlling the offshore AC bus voltage; if the energy storage battery is depleted and cannot support the normal operation of the offshore intelligent computing center and the offshore station power load, the diesel generator is put into operation to supply power to the offshore intelligent computing center and the offshore station power load.

3. The control method of claim 2, wherein: The control system for realizing the virtual synchronous machine control strategy of the energy storage grid-connected converter comprises a virtual synchronous machine mechanical module, a virtual synchronous machine excitation module, a voltage outer loop controller, a current inner loop controller, a Park inverse transformation module and a modulation module; in the virtual synchronous machine mechanical module, a reference phase θ is calculated according to the following method b : θ b (k+1) = ∫ω b (k+1)dt where θ b (k+1) is the reference phase of the next sampling period, ω b (k+1) is the angular frequency of the next sampling period, ω b (k) is the angular frequency of the current sampling period, ω n is the rated angular frequency, P bref is the active power reference value, P b (k) is the active power of the current sampling period, J is the virtual rotor moment of inertia, D p is the active damping coefficient; In the virtual synchronous machine excitation module, the d-axis voltage reference value u is calculated according to the following method bdref : wherein, u bdref (k+1) is the d-axis voltage reference value of the next sampling period, |U b (k) is the voltage amplitude of the current sampling period, U ref is the voltage amplitude reference value, Q bref is the reactive power reference value, Q b (k) is the reactive power of the current sampling period, K is the virtual excitation coefficient, D q is the reactive power damping coefficient.

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