A control method and device for parallel operation of a synchronous power supply and a network-forming flexible DC power supply

Abstract

The present invention provides a control method and device for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply, and relates to the field of power electronic control technology. The method includes: determining the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply; according to the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the network-forming flexible DC power supply, adding a first-order inertia link in the primary frequency modulation branch of the network-forming flexible DC power supply to obtain the adjusted frequency characteristics of the network-forming flexible DC power supply; the first-order inertia link is used to simulate the inertia of the speed regulator of the synchronous power supply; according to the adjusted frequency characteristics of the network-forming flexible DC power supply, power distribution of the synchronous power supply and the network-forming flexible DC power supply is performed. The method of the embodiment of the present application effectively solves the problems of power grabbing and power oscillation caused by too fast changes in the active power of the network-forming flexible DC power supply, and improves the quality and safety of the parallel operation of the synchronous power supply and the network-forming flexible DC power supply.

Description

Technical Field

[0001] The present invention relates to the field of power electronic control technology, and in particular to a control method and device for parallel operation of a synchronous power supply and a grid-forming flexible direct current power supply. Background Art

[0002] With the rapid development of renewable energy in China, a new power system dominated by renewable energy will emerge in the future. Renewable energy generation is connected to the power system through power electronic converters, which reduces system inertia and damping, while also impacting frequency and voltage regulation capabilities.

[0003] In related technologies, when synchronous power supplies and grid-flexible DC power supplies are operated in parallel, power oscillations can occur due to differences in their frequency characteristics. Therefore, there is an urgent need for an efficient and stable parallel operation control method to improve the reliability and efficiency of power systems. Summary of the Invention

[0004] The present invention provides a control method for the parallel operation of a synchronous power supply and a network-building flexible DC power supply. By comparing the frequency characteristic differences between the two types of power supplies, a first-order inertia link is added to the primary frequency modulation branch of the network-building flexible DC power supply to simulate the inertia of the speed regulator of the synchronous machine, thereby completing the frequency characteristic reshaping of the network-building power supply, effectively reducing the frequency characteristic differences between the two types of power supplies, and effectively solving the problems of power grabbing and power oscillation caused by excessively rapid changes in the active power of the network-building power supply, thereby improving the quality and safety of the parallel operation of the synchronous power supply and the network-building flexible DC power supply.

[0005] The present invention provides a control method for parallel operation of a synchronous power supply and a network-forming flexible direct current power supply, comprising the following steps.

[0006] Determine the frequency characteristics of synchronous power supply and grid-connected flexible DC power supply;

[0007] According to the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the networked flexible DC power supply, a first-order inertia link is added to the primary frequency modulation branch of the networked flexible DC power supply to obtain an adjusted frequency characteristic of the networked flexible DC power supply; the first-order inertia link is used to simulate the inertia of the speed regulator of the synchronous power supply;

[0008] Power distribution between the synchronous power supply and the networking flexible DC power supply is performed according to the adjusted frequency characteristics of the networking flexible DC power supply.

[0009] According to a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply provided by the present invention,

[0010] The frequency characteristics of the synchronous power supply include:

[0011]

[0012] in, is the primary frequency modulation coefficient of the synchronous power supply; M is the inertia time constant of the synchronous power supply; s is a variable on the complex plane; is the damping coefficient of the synchronous power supply; is the inertia time constant of the speed regulator;

[0013] The frequency characteristics of the network-building flexible DC power supply include:

[0014]

[0015] in, is the virtual inertia; and is the angular frequency; s is a variable on the complex plane; D is the virtual damping; is the primary frequency modulation coefficient.

[0016] According to a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply provided by the present invention,

[0017] The first-order inertia link includes:

[0018]

[0019] Where T is the first-order inertia time constant and s is a variable on the complex plane.

[0020] According to a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply provided by the present invention, the frequency characteristics of the network-forming flexible DC power supply after adjustment include:

[0021]

[0022] in, is the angular frequency; T is the inertia time constant of the speed regulator; s is a variable on the complex plane; is the virtual inertia; D is the virtual damping; is the primary frequency modulation coefficient of the synchronous power supply.

[0023] According to a control method for parallel operation of a synchronous power supply and a grid-forming flexible DC power supply provided by the present invention, the virtual damping is set to zero.

[0024] According to a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply provided by the present invention, before adding a first-order inertia link in the primary frequency modulation branch of the network-forming flexible DC power supply and obtaining the adjusted frequency characteristics of the network-forming flexible DC power supply, the method further includes:

[0025] Determine the corresponding relationship between the grid power capacity and the inertia time constant of the speed regulator;

[0026] The inertia time constant of the speed regulator is determined according to the corresponding relationship between the network power capacity and the inertia time constant of the speed regulator.

[0027] According to a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply provided by the present invention, the corresponding relationship between the network-forming power supply capacity and the inertia time constant of the speed regulator includes:

[0028]

[0029] Wherein, H is the inertia time constant of the synchronous machine; S is the power capacity of the network; T is the inertia time constant of the speed regulator; is the damping ratio of the grid power supply; is the primary frequency modulation coefficient of the synchronous power supply; is the angular frequency.

[0030] The present invention also provides a control device for parallel operation of a synchronous power supply and a network-forming flexible DC power supply, comprising the following modules:

[0031] A determination module, used to determine the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply;

[0032] an adjustment module, configured to add a first-order inertia link to a primary frequency modulation branch of the networked flexible DC power supply based on a difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the networked flexible DC power supply, thereby obtaining an adjusted frequency characteristic of the networked flexible DC power supply; the first-order inertia link is configured to simulate the inertia of the speed regulator of the synchronous power supply;

[0033] The control module is used to distribute power between the synchronous power supply and the networking flexible DC power supply according to the adjusted frequency characteristics of the networking flexible DC power supply.

[0034] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and runnable on the processor. When the processor executes the program, it implements a control method for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply as described in any one of the above.

[0035] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the control method for the parallel operation of the synchronous power supply and the grid-forming flexible DC power supply as described in any one of the above is implemented.

[0036] The present invention also provides a computer program product, comprising a computer program, which, when executed by a processor, implements a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply as described in any one of the above.

[0037] The control method for the parallel operation of a synchronous power supply and a network-building flexible DC power supply provided by the present invention compares the frequency characteristic differences between the two types of power supplies, adds a first-order inertia link to the primary frequency modulation branch of the network-building flexible DC power supply to simulate the inertia of the speed regulator of the synchronous machine, thereby completing the frequency characteristic reshaping of the network-building power supply, effectively reducing the frequency characteristic differences between the two types of power supplies, and effectively solving the power grabbing and power oscillation problems caused by the rapid change of the active power of the network-building power supply, thereby improving the quality and safety of the parallel operation of the synchronous power supply and the network-building flexible DC power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is one of the flow charts of the control method for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply provided by the present invention.

[0040] Figure 2 This is the second flow chart of the control method for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply provided by the present invention.

[0041] Figure 3 This is a system topology diagram of the synchronous machine and the grid-forming flexible DC power supply in parallel in an example of the present invention.

[0042] Figure 4a and Figure 4b This is a control structure diagram of the synchronous machine and the conventional grid-forming flexible DC power supply in the example of the present invention.

[0043] Figure 5 This is a diagram of the active loop control structure after the frequency characteristics of the network-forming flexible DC power supply in the example of the present invention are reshaped.

[0044] Figure 6 This is a comparison diagram of the power responses of two types of power supplies before and after improvement in an example of the present invention.

[0045] Figure 7 It is a structural schematic diagram of a control device for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply provided by the present invention.

[0046] Figure 8 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0048] The following combination Figures 1-8 The present invention describes a control method for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply.

[0049] In order to facilitate a clearer understanding of the technical solutions of the various embodiments of the present application, some technical contents related to the various embodiments of the present application are first introduced.

[0050] With the rapid development of renewable energy in China, a new power system dominated by renewable energy will emerge in the future. Renewable energy generation is connected to the power system via power electronic converters, reducing system inertia and damping while also impacting frequency and voltage regulation capabilities. To ensure the stable operation of this new power system, grid-connected converter control with voltage and frequency support capabilities has become a hot topic among research institutions and universities. Virtual synchronous generator control is suitable for both grid-connected inverter and isolated grid operation scenarios and is one of the most widely used grid-connected strategies.

[0051] Grid-connected flexible DC power supplies commonly use a virtual synchronous (VSG) control strategy to simulate the inertial characteristics of synchronous power supplies (as described in patent CN 112636395A). Its core approach simulates the rotor's mechanical inertia using a second-order differential equation. However, this strategy only replicates the synchronous power supply's rotor motion equations and does not incorporate the first-order inertial characteristics of the speed regulator (time constant Tg = 0.2-0.5s). According to measured data from IEEE Trans. Power Electronics, Issue 5, 2023, the dynamic response deviation between traditional VSGs and synchronous power supplies in the 0.5-2Hz frequency band can exceed 15dB, resulting in low-frequency oscillations of 2-5Hz (peak values ​​reaching 30% of the rated power) in the system during sudden load changes. Existing technologies (such as patent CN 113328468A) introduce a virtual damping coefficient into VSG control to suppress oscillations, but this parameter directly interferes with the P / F slope characteristics of droop control. The 2024 experimental report of the China Electric Power Research Institute shows that when two VSGs with a capacity ratio of 2:1 are connected in parallel, the difference in virtual damping will cause the power distribution error to expand from the theoretical value of 3% to more than 12%, seriously violating the power sharing error ≤ 5% stipulated in the "GB / T 34120-2017 Technical Requirements for Energy Storage Converters".

[0052] While virtual synchronous generator control draws on the control mechanisms of synchronous power supplies, differences in control strategies exist. When synchronous power supplies and inverter-type power supplies participate in system frequency regulation, the two types of power supplies exhibit significant differences in dynamic and static frequency characteristics. Under parallel operation, these differences can lead to transient power imbalances among distributed power sources. In severe cases, overloads can even cause inverter-type power supplies to disconnect, triggering a cascading system failure and posing a serious threat to the safe and stable operation of the power system.

[0053] In summary, in order to solve the power oscillation problem caused by the difference in frequency characteristics between the synchronous power supply and the grid-connected flexible DC power supply when they are operated in parallel, it is urgent to provide an efficient and stable parallel operation control method to improve the reliability and operation efficiency of the power system.

[0054] Figure 1 This is one of the flow charts of the control method for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply provided by the present invention, such as Figure 1 As shown, the method includes the following:

[0055] Step 101: Determine the frequency characteristics of the synchronous power supply and the grid-forming flexible DC power supply.

[0056] Specifically, when synchronous power sources and inverter-type power sources jointly participate in system frequency regulation, the two types of power sources exhibit significant differences in their dynamic and static frequency characteristics. Under parallel operation, these differences can lead to transient power imbalances among distributed power sources. In severe cases, this can even cause inverter-type power sources to be disconnected due to overload, triggering a cascading system failure and posing a serious threat to the safe and stable operation of the power system.

[0057] To address the aforementioned issues, in the embodiments of this application, mathematical models of synchronous generators and grid-connected flexible DC power supplies are first established. The frequency response model of synchronous generators is a second-order system, while the frequency response model of grid-connected flexible DC power supplies is a first-order system. These differences in mathematical expression are significant, and grid-connected control fails to account for the inertia of the speed regulators of traditional synchronous generators, which can easily lead to significant mismatches during the transition process when the two types of power supplies are connected in parallel.

[0058] Step 102: Based on the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the network-forming flexible DC power supply, a first-order inertia link is added to the primary frequency modulation branch of the network-forming flexible DC power supply to obtain an adjusted frequency characteristic of the network-forming flexible DC power supply; the first-order inertia link is used to simulate the inertia of the speed regulator of the synchronous power supply.

[0059] Specifically, after establishing the mathematical models of the synchronous machine and the grid-forming flexible DC power supply, in the embodiment of the present application, by comparing the frequency characteristics differences of the two types of power supplies, a first-order inertia link is added to the primary frequency modulation branch of the grid-forming flexible DC power supply to simulate the speed regulator inertia of the synchronous machine, thereby completing the frequency characteristics reshaping of the grid-forming power supply and effectively reducing the frequency characteristics differences between the two types of power supplies.

[0060] Step 103: Power distribution between the synchronous power supply and the networking flexible DC power supply is performed according to the adjusted frequency characteristics of the networking flexible DC power supply.

[0061] Specifically, in the embodiment of the present application, by adding a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power supply to simulate the inertia of the synchronous machine's speed regulator, the frequency response model of the network-forming power supply is upgraded to a mathematical model of a second-order system, which significantly reduces the difference in frequency characteristics between the synchronous machine and the network-forming power supply. This can effectively avoid the power grabbing and power oscillation problems caused by the rapid change in the active power of the network-forming power supply, without affecting the power distribution between the power supplies and without adding additional hardware costs. Optionally, the frequency difference of the network-forming flexible DC power supply is simulated by calculating the mechanical power increment through the primary frequency modulation coefficient and the first-order inertia link, and the mechanical power of the network-forming power supply is obtained by adding it to the active power reference value.

[0062] The method of the above embodiment compares the frequency characteristic differences between the two types of power supplies, adds a first-order inertia link to the primary frequency modulation branch of the grid-forming flexible DC power supply to simulate the inertia of the speed regulator of the synchronous machine, thereby completing the frequency characteristic reshaping of the grid-forming power supply, effectively reducing the frequency characteristic differences between the two types of power supplies, and effectively solving the power grabbing and power oscillation problems caused by the rapid change of the active power of the grid-forming power supply, thereby improving the quality and safety of the parallel operation of the synchronous power supply and the grid-forming flexible DC power supply.

[0063] In some embodiments, the frequency characteristics of the synchronous power supply include:

[0064]

[0065] in, is the primary frequency modulation coefficient of the synchronous power supply; M is the inertia time constant of the synchronous power supply; s is a variable on the complex plane; is the damping coefficient of the synchronous power supply; is the inertia time constant of the speed regulator;

[0066] The frequency characteristics of the grid-connected flexible DC power supply include:

[0067]

[0068] in, is the virtual inertia; and is the angular frequency; s is a variable on the complex plane; D is the virtual damping; is the primary frequency modulation coefficient.

[0069] Specifically, based on the generator rotor motion equation, the synchronous machine frequency characteristic expression is:

[0070]

[0071] in, is the inertia time constant of the synchronous machine's speed regulator; M is the inertia time constant of the synchronous machine; is the damping coefficient of the synchronous machine; is the primary frequency modulation coefficient of the synchronous machine.

[0072] The frequency characteristic expression of the grid-connected flexible DC power supply is:

[0073]

[0074] in, is the virtual inertia; D is the virtual damping; is the primary frequency modulation coefficient.

[0075] That is, by comparing the frequency characteristics of the two types of power supplies, the frequency response model of the synchronous machine power supply is a mathematical model of a second-order system, and the frequency response model of the grid-forming flexible DC power supply is a mathematical model of a first-order system. There are large differences in mathematical expressions. The grid-forming control does not take into account the inertia of the speed regulator of the traditional synchronous machine power supply, which easily leads to a large mismatch transition process when the two types of power supplies are connected in parallel.

[0076] The method of the above embodiment, after establishing the mathematical models of the synchronous machine and the grid-forming flexible DC power supply, can accurately reshape the frequency characteristics of the grid-forming power supply by comparing the frequency characteristics differences of the two types of power supplies, thereby reducing the frequency characteristics differences of the two types of power supplies and reducing the transient power oscillations of the two types of power supplies when the load changes.

[0077] In one embodiment, the first-order inertia link includes:

[0078]

[0079] Where T is the first-order inertia time constant and s is a variable on the complex plane.

[0080] Specifically, the embodiment of the present application adds a first-order inertia link to the primary frequency modulation branch of the networked flexible DC power supply to simulate the inertia of the synchronous machine speed regulator, thereby completing the frequency characteristic reshaping of the networked power supply and effectively reducing the frequency characteristic difference between the two types of power supplies. Optionally, the first-order inertia link expression is:

[0081]

[0082] Where T is the first-order inertia time constant.

[0083] In some embodiments, the frequency characteristics of the adjusted grid-connected flexible DC power supply include:

[0084]

[0085] in, is the angular frequency; T is the inertia time constant of the speed regulator; s is a variable on the complex plane; is the virtual inertia; D is the virtual damping; is the primary frequency modulation coefficient of the synchronous power supply.

[0086] Specifically, the mechanical power increment caused by the primary frequency modulation link of the grid power supply after the frequency characteristics are reshaped is:

[0087]

[0088] The mechanical power of the grid power supply is:

[0089]

[0090] The rotor motion equation of the grid power supply is:

[0091]

[0092] Furthermore, after the frequency characteristics of the grid power supply are reshaped, the frequency characteristic expression is:

[0093]

[0094] That is, after considering the inertia of the speed regulator in this application, the frequency response model of the grid power supply is upgraded to a mathematical model of a second-order system, which significantly reduces the frequency characteristic difference between the synchronous machine and the grid power supply, and can effectively avoid the power grabbing and power oscillation problems caused by the rapid change of the active power of the grid power supply.

[0095] The method of the above embodiment reshapes the frequency characteristics of the grid power supply by taking into account the inertia of the speed regulator. The frequency response model of the grid power supply is upgraded to a mathematical model of a second-order system, thereby significantly reducing the frequency characteristic difference between the synchronous machine and the grid power supply, and solving the problems of power grabbing and power oscillation caused by excessively rapid changes in the active power of the grid power supply.

[0096] In some embodiments, after obtaining the adjusted frequency characteristics of the grid-connected flexible DC power supply, the method further includes:

[0097] Set virtual damping to zero.

[0098] Specifically, in an embodiment of the present application, to further eliminate the impact of the virtual damping coefficient on the primary frequency modulation characteristics of the grid-forming flexible DC power supply, the virtual damping in the adjusted frequency characteristics of the grid-forming flexible DC power supply is set to zero. Exemplarily, when the virtual damping is set to zero, as shown below, when the load changes, the power distribution between the synchronous power supply and the grid-forming flexible DC power supply is related only to the primary frequency modulation, effectively avoiding the impact on the primary frequency modulation characteristics.

[0099]

[0100] The method of the above embodiment sets the virtual damping to zero, which can effectively eliminate the influence of the virtual damping coefficient on the primary frequency modulation characteristics of the grid-forming flexible DC power supply, so that the power distribution between the synchronous power supply and the grid-forming flexible DC power supply is only related to the primary frequency modulation, effectively avoiding the influence on the primary frequency modulation characteristics.

[0101] In some embodiments, before adding a first-order inertia link to the primary frequency modulation branch of the grid-forming flexible DC power supply and obtaining the adjusted frequency characteristics of the grid-forming flexible DC power supply, the method further includes:

[0102] Determine the corresponding relationship between the grid power capacity and the inertia time constant of the speed regulator;

[0103] The inertia time constant of the speed regulator is determined based on the corresponding relationship between the network power capacity and the inertia time constant of the speed regulator.

[0104] Specifically, in the embodiment of the present application, a functional relationship is established between the grid power capacity and the inertia parameters of the speed regulator based on the damping ratio method, providing a basis for the parameter design of grid flexible DC power supplies of different capacities.

[0105] Optionally, the damping ratio expression of the grid power supply is:

[0106]

[0107] Based on automatic control theory, the damping ratio interval can be set to [0.707, 1], which has better dynamic performance.

[0108] Furthermore, for grid-connected flexible DC power supplies of different capacities, the virtual inertia The value of the primary frequency modulation coefficient kw is different.

[0109]

[0110] After the virtual inertia and primary frequency modulation coefficient are selected, the inertia time constant of the network-type speed regulator can be designed using the following functional relationship:

[0111]

[0112] The method of the above embodiment establishes a functional relationship between the grid power capacity and the inertia parameters of the speed regulator based on the damping ratio method, thereby providing a basis for the parameter design of grid flexible DC power supplies of different capacities; furthermore, based on the correspondence between the grid power capacity and the inertia time constant of the speed regulator, the inertia time constant of the speed regulator under different capacities can be accurately determined, thereby effectively improving the dynamic performance.

[0113] Exemplarily, an embodiment of the present application also provides a control system for a synchronous machine and a grid-connected flexible DC power supply in parallel, wherein a traditional synchronous machine power supply and a grid-connected flexible DC power supply generate electricity in parallel, and the grid-connected flexible DC power supply adopts a virtual synchronous machine control; a grid-connected flexible DC power supply speed regulator inertia module is used to simulate the inertia of the synchronous machine speed regulator and reduce the difference in frequency characteristics of the two types of power supplies; a grid-connected flexible DC power supply primary frequency modulation calculation module is used to calculate the primary frequency modulation compensation power according to the frequency difference of the grid-connected power supply; a grid-connected flexible DC power supply angular frequency calculation module is used to calculate the angular frequency and power angle of the grid-connected flexible DC power supply through the virtual inertia and damping link of the difference between the system mechanical power and electromagnetic power; a grid-connected flexible DC power supply virtual impedance control module is used to limit the converter current after a transient fault occurs in the system; a grid-connected flexible DC power supply voltage and current control module is used to calculate the power decoupling of the grid-connected flexible DC power supply and obtain the reference voltage of the grid-connected converter; a grid-connected flexible DC power supply converter PWM control module is used to generate a control switch signal for the grid-connected converter. That is, the grid-forming flexible DC power supply obtains the switching control signal of the grid-forming flexible DC power supply converter through the primary frequency and voltage regulation module, the power loop control module, the virtual impedance module, the voltage and current control module, and the PWM modulation module.

[0114] For example, Figure 2 As shown, an embodiment of the present application provides a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply, which is specifically as follows:

[0115] Mathematical models of synchronous power supplies and grid-flexible DC power supplies were established, and the frequency characteristics of the two types of power supplies were compared. Subsequently, the primary frequency regulation control link of the grid-flexible DC power supply was improved by adding a first-order inertia link to the primary frequency regulation branch to simulate the inertia of the synchronous power supply's speed regulator, reducing the frequency characteristic differences between the synchronous power supply and the grid-flexible DC power supply. Furthermore, the virtual damping control link was eliminated to prevent the grid-flexible DC power supply's virtual damping coefficient from affecting power distribution. Finally, a functional relationship between the grid-flexible DC power supply capacity and the speed regulator inertia parameters was established, providing a basis for parameter design of grid-flexible DC power supplies of varying capacities.

[0116] This application can effectively suppress the active oscillation when the synchronous power supply and the grid-type flexible DC are connected in parallel by reshaping the frequency characteristics of the grid-forming flexible DC power supply, without affecting the power distribution between the power supplies and without increasing additional hardware costs.

[0117] For example, in order to verify the power oscillation suppression method and system of the synchronous machine and the grid-connected flexible DC power supply in parallel in this application, the following simulation platform is built using MATLAB / Simulink: Figure 3 The regional power grid model is shown in Figure 1. The grid-flexible DC power converter is controlled by a virtual synchronous machine, and the converter output is connected to the busbar through a filter and a transmission line.

[0118] First, set the relevant simulation parameters. In this embodiment, the relevant parameters in the control strategy are set as follows:

[0119] Synchronous generator: diesel generator set model, rated power 80kW, rated voltage 380V, moment of inertia M=5s, governor time constant Tg=0.2s, primary frequency modulation coefficient Kdroop=105kW / Hz.

[0120] Grid-connected flexible DC power supply: The energy storage converter adopts dual closed-loop VSG control, with a rated power of 80kW, a DC bus voltage of 800V, a virtual inertia Jvsg=4s, a primary frequency modulation coefficient Kdroop=105kW / Hz, the virtual damping coefficient is cancelled (Dvsg=0), and a first-order inertia link is added (time constant Tvsg=0.2s).

[0121] Grid connection: filter parameters Lf=2mH, Cf=50μF, transmission line impedance Zline=0.02Ω+0.2mH, bus voltage 380V / 50Hz.

[0122] Among them, the control structure diagram of the synchronous machine and conventional grid-connected flexible DC power supply in the related technology is as follows: Figure 4a and Figure 4b As shown, the control block diagram of the network-forming flexible DC power supply in the embodiment of the present application (as shown in FIG. Figure 5 shown) contains:

[0123] Power calculation module: generates active power Pvsg based on instantaneous power theory;

[0124] First-order inertia link: transfer function G(s) = 11 + 0.2s, simulating the characteristics of the synchronous machine speed regulator;

[0125] Rotor motion equation: Jvsgdωdt=Pref−Pvsg, output frequency command fvsg.

[0126] Next, the simulation conditions are set. In the initial stable state, the two types of power sources each bear a 40kW load. At 4 seconds, the load at the busbar is connected to 80kW, and the simulation ends at 7 seconds. The active power changes of the two types of power sources before and after the improvement of the flexible DC power supply control are as follows: Figure 6 As shown in the figure, the power output power is expressed per unit with 80kW as the reference value.

[0127] Depend on Figure 6 Simulation results show that when a conventional grid-connected flexible DC power supply operates in parallel with a traditional synchronous generator, the two power sources experience significant active power oscillations during transients when subjected to external load disturbances, due to significant differences in their frequency characteristics. This oscillation peaks at t=4.5s, then gradually weakens, reaching a plateau at t=5.5s. Reshaping the frequency characteristics of the grid-connected flexible DC power supply reduces the difference in frequency characteristics between the two power sources. When subjected to external load disturbances, power distribution between the two power sources is significantly improved during transients, with no significant peaks throughout the transition process, resulting in a smooth transition and significantly improved parallel operation characteristics.

[0128] Optionally, the quantitative indicator verification is shown in Table 1:

[0129] Table 1

[0130]

[0131] In summary, the solution of the present application can be directly applied to the converter based on virtual synchronous control of the networked flexible DC power supply. A first-order inertia link is added to the primary frequency modulation branch of the networked flexible DC power supply to simulate the inertia of the speed regulator of the synchronous machine, thereby completing the frequency characteristic reshaping of the networked flexible DC power supply and reducing the difference in frequency characteristics between the synchronous machine and the networked flexible DC power supply. This effectively reduces the transient power oscillation of the two types of power supplies when the load changes, and improves the quality and safety of their parallel operation. In order to further prevent the virtual damping coefficient of the networked flexible DC power supply from affecting the power distribution, the virtual damping control link is eliminated; on this basis, a functional relationship is established between the networked power supply capacity and the speed regulator inertia parameters based on the damping ratio method, providing a basis for the parameter design of networked flexible DC power supplies of different capacities. At the same time, the system does not rely on communication and does not require the addition of additional hardware circuits, thereby improving the flexibility and economy of the system.

[0132] The following describes the control device for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply provided by the present invention. The control device for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply described below and the control method for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply described above can be referred to each other. Figure 7 Shown, including:

[0133] A determination module 710 is configured to determine frequency characteristics of the synchronous power supply and the grid-forming flexible DC power supply;

[0134] Adjustment module 720 is configured to add a first-order inertia link to the primary frequency modulation branch of the networked flexible DC power supply based on the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the networked flexible DC power supply, thereby obtaining an adjusted frequency characteristic of the networked flexible DC power supply; the first-order inertia link is configured to simulate the inertia of the speed regulator of the synchronous power supply;

[0135] The control module 730 is configured to distribute power between the synchronous power supply and the networking flexible DC power supply according to the adjusted frequency characteristics of the networking flexible DC power supply.

[0136] Figure 8 A schematic diagram of the physical structure of an electronic device is provided. The electronic device may include: a processor 810, a communications interface 820, a memory 830, and a communications bus 840. The processor 810, the communications interface 820, and the memory 830 communicate with each other via the communications bus 840. The processor 810 may invoke logic instructions in the memory 830 to execute a control method for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply. The method includes: determining the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply; adding a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power supply based on the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the network-forming flexible DC power supply to obtain an adjusted frequency characteristic of the network-forming flexible DC power supply; the first-order inertia link is used to simulate the inertia of the synchronous power supply's speed regulator; and distributing power between the synchronous power supply and the network-forming flexible DC power supply based on the adjusted frequency characteristics of the network-forming flexible DC power supply.

[0137] Furthermore, the logic instructions in the aforementioned memory 830 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product, stored in a storage medium, includes instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical disks.

[0138] On the other hand, the present invention also provides a computer program product, which includes a computer program, which can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the control method for parallel operation of the synchronous power supply and the grid-forming flexible DC power supply provided by the above methods, the method including: determining the frequency characteristics of the synchronous power supply and the grid-forming flexible DC power supply; according to the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the grid-forming flexible DC power supply, adding a first-order inertia link in the primary frequency modulation branch of the grid-forming flexible DC power supply to obtain the adjusted frequency characteristics of the grid-forming flexible DC power supply; the first-order inertia link is used to simulate the inertia of the speed regulator of the synchronous power supply; and according to the adjusted frequency characteristics of the grid-forming flexible DC power supply, power distribution between the synchronous power supply and the grid-forming flexible DC power supply is performed.

[0139] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the control method for parallel operation of the synchronous power supply and the networked flexible DC power supply provided by the above methods, the method including: determining the frequency characteristics of the synchronous power supply and the networked flexible DC power supply; adding a first-order inertia link in the primary frequency modulation branch of the networked flexible DC power supply according to the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the networked flexible DC power supply to obtain the adjusted frequency characteristics of the networked flexible DC power supply; the first-order inertia link is used to simulate the inertia of the speed regulator of the synchronous power supply; and performing power distribution between the synchronous power supply and the networked flexible DC power supply according to the adjusted frequency characteristics of the networked flexible DC power supply.

[0140] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0141] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply, characterized in that: include: Determine the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply; wherein the frequency characteristics of the synchronous power supply include: in, is the primary frequency modulation coefficient of the synchronous power supply; M is the inertia time constant of the synchronous power supply; s is a variable on the complex plane; is the damping coefficient of the synchronous power supply; is the inertia time constant of the speed regulator; The frequency characteristics of the network-building flexible DC power supply include: in, is the virtual inertia; and is the angular frequency; s is a variable on the complex plane; D is the virtual damping; is the primary frequency modulation coefficient; According to the difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the networked flexible DC power supply, a first-order inertia link is added to the primary frequency modulation branch of the networked flexible DC power supply to obtain an adjusted frequency characteristic of the networked flexible DC power supply; the first-order inertia link is used to simulate the inertia of the speed regulator of the synchronous power supply; The method further comprises: distributing power between the synchronous power supply and the networked flexible DC power supply according to the adjusted frequency characteristics of the networked flexible DC power supply; distributing power between the synchronous power supply and the networked flexible DC power supply according to the adjusted frequency characteristics of the networked flexible DC power supply, comprising: When the load changes, the power distribution between the synchronous power source and the grid-connected flexible DC power source is only related to the primary frequency regulation, as follows: ； in, is the primary frequency modulation coefficient of the synchronous power supply; is the primary frequency modulation coefficient of the grid-connected flexible DC power supply; and Indicates the power distribution value of the synchronous power supply and the grid-forming flexible DC power supply; is the angular frequency.

2. The control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply according to claim 1, characterized in that: The first-order inertia link includes: Where T is the first-order inertia time constant and s is a variable on the complex plane.

3. The control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply according to claim 2, characterized in that: The frequency characteristics of the network-building flexible DC power supply after adjustment include: in, is the angular frequency; T is the inertia time constant of the speed regulator; s is a variable on the complex plane; is the virtual inertia; D is the virtual damping; is the primary frequency modulation coefficient of the synchronous power supply.

4. The control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply according to claim 3, characterized in that: After obtaining the adjusted frequency characteristics of the grid-forming flexible DC power supply, the method further includes: Set virtual damping to zero.

5. The control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply according to claim 3, characterized in that: Before adding a first-order inertia link in the primary frequency modulation branch of the networked flexible DC power supply to obtain the adjusted frequency characteristics of the networked flexible DC power supply, the method further includes: Determine the corresponding relationship between the network power capacity and the inertia time constant of the speed regulator; The inertia time constant of the speed regulator is determined according to the corresponding relationship between the network power capacity and the inertia time constant of the speed regulator.

6. The control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply according to claim 5, characterized in that: The corresponding relationship between the network power capacity and the speed regulator inertia time constant includes: Wherein, H is the inertia time constant of the synchronous machine; S is the power capacity of the network; T is the inertia time constant of the speed regulator; is the damping ratio of the grid power supply; is the primary frequency modulation coefficient of the synchronous power supply; is the angular frequency.

7. A control device for parallel operation of a synchronous power supply and a network-forming flexible DC power supply, characterized in that: include: A determination module is used to determine the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply; wherein the frequency characteristics of the synchronous power supply include: in, is the primary frequency modulation coefficient of the synchronous power supply; M is the inertia time constant of the synchronous power supply; s is a variable on the complex plane; is the damping coefficient of the synchronous power supply; is the inertia time constant of the speed regulator; The frequency characteristics of the network-building flexible DC power supply include: in, is the virtual inertia; and is the angular frequency; s is a variable on the complex plane; D is the virtual damping; is the primary frequency modulation coefficient; an adjustment module configured to add a first-order inertia link to the primary frequency modulation branch of the networked flexible DC power supply based on a difference between the frequency characteristics of the synchronous power supply and the frequency characteristics of the networked flexible DC power supply, thereby obtaining an adjusted frequency characteristic of the networked flexible DC power supply; the first-order inertia link is configured to simulate the inertia of the speed regulator of the synchronous power supply; A control module, configured to distribute power between a synchronous power supply and a networked flexible DC power supply according to the adjusted frequency characteristics of the networked flexible DC power supply; the power distribution between the synchronous power supply and the networked flexible DC power supply according to the adjusted frequency characteristics of the networked flexible DC power supply, comprising: When the load changes, the power distribution between the synchronous power source and the grid-connected flexible DC power source is only related to the primary frequency regulation, as follows: ； in, is the primary frequency modulation coefficient of the synchronous power supply; is the primary frequency modulation coefficient of the grid-connected flexible DC power supply; and Indicates the power distribution value of the synchronous power supply and the grid-forming flexible DC power supply; is the angular frequency.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, it implements the control method for parallel operation of the synchronous power supply and the grid-forming flexible DC power supply as described in any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the control method for parallel operation of a synchronous power supply and a grid-connected flexible DC power supply as described in any one of claims 1 to 6 is implemented.

Images