Control method for parallel operation of synchronous power supply and networking flexible direct-current power supply

Abstract

The invention provides a control method for parallel operation of a synchronous power supply and a networked flexible direct-current power supply, and relates to the technical field of power electronic control. The method comprises the following steps: determining frequency characteristics of a synchronous power supply and a networking flexible direct-current power supply; according to the difference between the frequency characteristic of the synchronous power supply and the frequency characteristic of the networking flexible direct-current power supply, adding a first-order inertia link in a primary frequency modulation branch of the networking flexible direct-current power supply to obtain the adjusted frequency characteristic of the networking flexible direct-current power supply; the first-order inertia link is used for simulating speed regulator inertia of the synchronous power supply; and performing power distribution of the synchronous power supply and the networking flexible direct-current power supply according to the adjusted frequency characteristics of the networking flexible direct-current power supply. The method provided by the embodiment of the invention effectively solves the problems of work grabbing and power oscillation caused by too fast active change of the network construction power supply, and improves the quality and safety of parallel operation of the synchronous power supply and the network construction flexible direct current power supply.

Description

Technical Field

[0001] The present invention relates to the field of power electronics control technology, and particularly to a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply. Background Art

[0002] With the rapid development of new energy in China, a new power system mainly based on new energy will be formed in the future. New energy power generation is connected to the power system through a power electronic converter, resulting in a reduction in system inertia and damping, and at the same time affecting the frequency and voltage regulation capabilities.

[0003] In related technologies, when a synchronous power supply and a network-forming flexible DC power supply are operated in parallel, due to the difference in their frequency characteristics, a power oscillation problem occurs. Therefore, there is an urgent need to provide an efficient and stable parallel operation control method to improve the reliability and operation efficiency of the power system. Summary of the Invention

[0004] The present invention provides a control method for parallel operation of a synchronous power supply and a network-forming flexible DC power supply. By comparing the differences in the frequency characteristics of the two types of power supplies, a first-order inertia link is added to the primary frequency modulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous machine, thereby completing the reshaping of the frequency characteristics of the network-forming power supply, effectively reducing the differences in the frequency characteristics of the two types of power supplies, effectively solving the problems of power snatching and power oscillation caused by the too-fast change of the active power of the network-forming power supply, and improving the quality and safety of the parallel operation of the synchronous power supply and the network-forming 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 DC power supply, including the following steps.

[0006] Determine 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, add a first-order inertia link to 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 governor inertia of the synchronous power supply; According to the adjusted frequency characteristics of the network-forming flexible DC power supply, perform power distribution between the synchronous power supply and the network-forming flexible DC power supply.

[0007] 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 synchronous power supply include:

[0008] Wherein, is the primary frequency regulation coefficient of the synchronous power supply; M is the inertia time constant of the synchronous power supply; s is a variable in the complex plane; is the damping coefficient of the synchronous power supply; is the governor inertia time constant; The frequency characteristics of the network-forming flexible DC power supply include:

[0009] Among them, is the virtual inertia; and are angular frequencies; s is a variable in the complex plane; D is the virtual damping; is the primary frequency regulation coefficient.

[0010] 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 first-order inertia link includes:

[0011] Among them, T is the first-order inertia time constant; s is a variable in the complex plane.

[0012] 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 adjusted frequency characteristics of the network-forming flexible DC power supply include:

[0013] Among them, is the angular frequency; T is the governor inertia time constant; s is a variable in the complex plane; is the virtual inertia; D is the virtual damping; is the primary frequency regulation coefficient of the synchronous power supply.

[0014] 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 virtual damping is set to zero.

[0015] 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 to the primary frequency regulation branch of the network-forming flexible DC power supply to obtain the adjusted frequency characteristics of the network-forming flexible DC power supply, the method further includes: Determine the corresponding relationship between the network-forming power supply capacity and the governor inertia time constant; Determine the governor inertia time constant according to the corresponding relationship between the network-forming power supply capacity and the governor inertia time constant.

[0016] 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 capacity of the network-forming power supply and the inertia time constant of the governor includes:

[0017] wherein, H is the inertia time constant of the synchronous machine; S is the capacity of the network-forming power supply; T is the inertia time constant of the governor; is the damping ratio of the network-forming power supply; is the primary frequency modulation coefficient of the synchronous power supply; is the angular frequency.

[0018] The present invention also provides a control device for parallel operation of a synchronous power supply and a network-forming flexible DC power supply, including the following modules: A determination module, configured to determine the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply; An adjustment module, configured to add a first-order inertia link to the primary frequency modulation branch of 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, so as to obtain the adjusted frequency characteristics of the network-forming flexible DC power supply; the first-order inertia link is used to simulate the governor inertia of the synchronous power supply; A control module, configured to perform power distribution between the synchronous power supply and the network-forming flexible DC power supply according to the adjusted frequency characteristics of the network-forming flexible DC power supply.

[0019] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the processor executes the program, the control method for parallel operation of the synchronous power supply and the network-forming flexible DC power supply as described in any one of the above is implemented.

[0020] The present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the control method for parallel operation of the synchronous power supply and the network-forming flexible DC power supply as described in any one of the above is implemented.

[0021] The present invention also provides a computer program product, including a computer program, and when the computer program is executed by a processor, the control method for parallel operation of the synchronous power supply and the network-forming flexible DC power supply as described in any one of the above is implemented.

[0022] 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 compares the differences in the frequency characteristics of the two types of power supplies, and adds a first-order inertia link to the primary frequency regulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous machine, thereby completing the reshaping of the frequency characteristics of the network-forming power supply, effectively reducing the differences in the frequency characteristics of the two types of power supplies, effectively solving the problems of power snatching and power oscillation caused by the too-fast change of the active power of the network-forming power supply, and improving the quality and safety of the parallel operation of the synchronous power supply and the network-forming flexible DC power supply. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is one of the flow schematic diagrams 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.

[0025] Figure 2 It is the second flow schematic diagram 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.

[0026] Figure 3 It is the system topology diagram of the parallel connection of the synchronous machine and the network-forming flexible DC power supply in the embodiment of the present invention.

[0027] Figure 4a and Figure 4b It is the control structure diagram of the synchronous machine and the conventional network-forming flexible DC power supply in the embodiment of the present invention.

[0028] Figure 5 It is the active power loop control structure diagram after the frequency characteristics of the network-forming flexible DC power supply are reshaped in the embodiment of the present invention.

[0029] Figure 6 It is the power response comparison diagram of the two types of power supplies before and after improvement in the embodiment of the present invention.

[0030] Figure 7 It is the structure schematic diagram of 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.

[0031] Figure 8 It is the structure schematic diagram of the electronic device provided by the present invention. Detailed Embodiments

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0033] The following will describe Figures 1-8 the control method for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply of the present invention.

[0034] To facilitate a clearer understanding of the technical solutions of the embodiments of the present application, some technical contents related to the embodiments of the present application will be introduced first.

[0035] With the rapid development of domestic new energy, a new power system with new energy as the main body will be formed in the future. New energy power generation is connected to the power system through a power electronic converter, resulting in a reduction in system inertia and damping, and at the same time affecting the frequency and voltage regulation capabilities. To ensure the stable operation of the new power system, the control of network-forming converters with voltage and frequency support functions has become a research hotspot for current research institutions and universities. Virtual synchronous machine control is applicable to the scenarios of inverter grid connection and island operation, and is one of the most widely used network-forming strategies.

[0036] Network-forming flexible DC power supplies generally adopt the virtual synchronous (VSG) control strategy to simulate the inertial characteristics of synchronous power supplies (as described in the patent CN 112636395A). Its core simulates the rotor mechanical inertia through a second-order differential equation. However, this strategy only reproduces the rotor motion equation of the synchronous power supply and does not include the first-order inertial characteristics of the governor (time constant Tg = 0.2 - 0.5 s). According to the measured data in the 5th issue of "IEEE Trans. Power Electronics" in 2023, the dynamic response deviation between the traditional VSG and the synchronous power supply in the 0.5 - 2 Hz frequency band can reach more than 15 dB, resulting in a 2 - 5 Hz low-frequency oscillation (peak value up to 30% of the rated power) in the system when the load changes suddenly. The prior art (such as the patent CN 113328468A) introduces a virtual damping coefficient in the VSG control to suppress the oscillation, but this parameter directly interferes with the P / f slope characteristic of the droop control. The experimental report of the China Electric Power Research Institute in 2024 shows that when two VSGs with a capacity ratio of 2:1 are connected in parallel, the virtual damping difference will increase the power distribution error from the theoretical value of 3% to more than 12%, seriously violating the regulation of the power sharing error ≤ 5% in the "GB / T 34120 - 2017 Technical Requirements for Energy Storage Converters".

[0037] Although the virtual synchronous machine control draws on the control mechanism of synchronous power sources, there are still differences in control strategies. 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 the dynamic and static characteristics of frequency. Under the condition of parallel operation, this characteristic difference will cause the transient power distribution imbalance among distributed power sources. In severe cases, it may even cause the inverter-type power source to trip due to overload, triggering the cascading collapse of the system and posing a serious threat to the safe and stable operation of the power system.

[0038] In summary, aiming at the power oscillation problem caused by the frequency characteristic difference between synchronous power sources and network-forming flexible DC power sources during parallel operation, it is urgent to provide an efficient and stable parallel operation control method to improve the reliability and operation efficiency of the power system.

[0039] Figure 1 It is one of the schematic flowcharts of the control method for the parallel operation of synchronous power sources and network-forming flexible DC power sources provided by the present invention. As Figure 1 shown, this method includes the following: Step 101: Determine the frequency characteristics of the synchronous power source and the network-forming flexible DC power source.

[0040] 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 the dynamic and static characteristics of frequency. Under the condition of parallel operation, this characteristic difference will cause the transient power distribution imbalance among distributed power sources. In severe cases, it may even cause the inverter-type power source to trip due to overload, triggering the cascading collapse of the system and posing a serious threat to the safe and stable operation of the power system.

[0041] To solve the above problems, in the embodiments of the present application, first, a mathematical model of the synchronous machine and the network-forming flexible DC power source is established. Among them, the frequency response model of the synchronous machine type power source is the mathematical model of a second-order system, and the frequency response model of the network-forming flexible DC power source is the mathematical model of a first-order system. There are significant differences in mathematical expressions. The network-forming control does not consider the governor inertia of traditional synchronous machine type power sources, which easily leads to a large mismatch transient process when the two types of power sources are paralleled.

[0042] Step 102: According to the difference between the frequency characteristics of the synchronous power source and the frequency characteristics of the network-forming flexible DC power source, add a first-order inertia link to the primary frequency regulation branch of the network-forming flexible DC power source to obtain the adjusted frequency characteristics of the network-forming flexible DC power source; the first-order inertia link is used to simulate the governor inertia of the synchronous power source.

[0043] Specifically, after establishing the mathematical models of the synchronous generator and the network-forming flexible DC power supply, in the embodiments of the present application, by comparing the frequency characteristic differences between the two types of power supplies, a first-order inertia link is added to the primary frequency regulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous generator, thereby completing the reshaping of the frequency characteristics of the network-forming power supply and effectively reducing the frequency characteristic differences between the two types of power supplies.

[0044] Step 103: Perform power distribution between the synchronous power supply and the network-forming flexible DC power supply according to the adjusted frequency characteristics of the network-forming flexible DC power supply.

[0045] Specifically, in the embodiments of the present application, after adding a first-order inertia link to the primary frequency regulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous generator, the frequency response model of the network-forming power supply is upgraded to the mathematical model of a second-order system, significantly reducing the frequency characteristic differences between the synchronous generator and the network-forming power supply. It can effectively avoid the problems of power snatching and power oscillation caused by the too-fast change of the active power of the network-forming power supply, and does not affect the power distribution between the power supplies, without the need to increase additional hardware costs. Optionally, the frequency difference of the network-forming flexible DC power supply is used to simulate and calculate the mechanical power increment through the primary frequency regulation coefficient and the first-order inertia link, and is added to the active power reference value to obtain the mechanical power of the network-forming power supply.

[0046] The method of the above embodiments, by comparing the frequency characteristic differences between the two types of power supplies, adds a first-order inertia link to the primary frequency regulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous generator, thereby completing the reshaping of the frequency characteristics of the network-forming power supply, effectively reducing the frequency characteristic differences between the two types of power supplies, effectively solving the problems of power snatching and power oscillation caused by the too-fast change of the active power of the network-forming power supply, and improving the quality and safety of the parallel operation of the synchronous power supply and the network-forming flexible DC power supply.

[0047] In some embodiments, the frequency characteristics of the synchronous power supply include:

[0048] wherein, is the primary frequency regulation 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 governor inertia time constant; The frequency characteristics of the network-forming flexible DC power supply include:

[0049] wherein, is the virtual inertia; and are angular frequencies; s is a variable on the complex plane; D is the virtual damping; is the primary frequency regulation coefficient.

[0050] Specifically, according to the generator rotor motion equation, the frequency characteristic expression of the synchronous machine is:

[0051] where is the governor inertia time constant of the synchronous machine; M is the inertia time constant of the synchronous machine; is the damping coefficient of the synchronous machine; is the primary frequency regulation coefficient of the synchronous machine.

[0052] The frequency characteristic expression of the network-forming flexible DC power supply is:

[0053] where is the virtual inertia; D is the virtual damping; is the primary frequency regulation coefficient.

[0054] That is, by comparing the frequency characteristics of the two types of power supplies, the frequency response model of the synchronous machine type power supply is a mathematical model of a second-order system, and the frequency response model of the network-forming flexible DC power supply is a mathematical model of a first-order system. There are significant differences in mathematical expressions. The network-forming control does not consider the governor inertia of the traditional synchronous machine type power supply, which easily leads to a large mismatched transient process when the two types of power supplies are paralleled.

[0055] After establishing the mathematical models of the synchronous machine and the network-forming flexible DC power supply, the method of the above embodiment can accurately reshape the frequency characteristics of the network-forming power supply by comparing the frequency characteristic differences between the two types of power supplies, thereby reducing the frequency characteristic differences between the two types of power supplies and reducing the transient power oscillation of the two types of power supplies when the load changes.

[0056] In one embodiment, the first-order inertia link includes:

[0057] where T is the first-order inertia time constant; s is a variable on the complex plane.

[0058] Specifically, in the embodiment of the present application, a first-order inertia link is added to the primary frequency regulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous machine, thereby completing the reshaping of the frequency characteristics of the network-forming power supply and effectively reducing the frequency characteristic differences between the two types of power supplies. Optionally, the expression of the first-order inertia link is:

[0059] where T is the first-order inertia time constant.

[0060] In some embodiments, the frequency characteristics of the adjusted network-forming flexible DC power supply include:

[0061] Among them, is the angular frequency; T is the governor inertia time constant; s is a variable in the complex plane; is the virtual inertia; D is the virtual damping; is the primary frequency regulation coefficient of the synchronous power supply.

[0062] Specifically, after the reshaping of the frequency characteristics, the mechanical power increment caused by the primary frequency regulation link of the network-forming power supply is:

[0063] The mechanical power of the network-forming power supply is:

[0064] The rotor motion equation of the network-forming power supply is:

[0065] Furthermore, after the reshaping of the frequency characteristics of the network-forming power supply, the frequency characteristic expression is:

[0066] That is, after considering the governor inertia in this application, the frequency response model of the network-forming power supply is upgraded to the mathematical model of a second-order system, significantly reducing the frequency characteristic difference between the synchronous machine and the network-forming power supply, and effectively avoiding the problems of power snatching and power oscillation caused by too rapid change of the active power of the network-forming power supply.

[0067] For the method of the above embodiment, after reshaping the frequency characteristics of the network-forming power supply by considering the governor inertia, the frequency response model of the network-forming power supply is upgraded to the mathematical model of a second-order system, thereby significantly reducing the frequency characteristic difference between the synchronous machine and the network-forming power supply, and solving the problems of power snatching and power oscillation caused by too rapid change of the active power of the network-forming power supply.

[0068] In some embodiments, after obtaining the frequency characteristics of the adjusted network-forming flexible DC power supply, the method further includes: Setting the virtual damping to zero.

[0069] Specifically, in the embodiments of this application, to further eliminate the influence of the virtual damping coefficient on the primary frequency regulation characteristics of the network-forming flexible DC power supply, the virtual damping in the frequency characteristics of the adjusted network-forming flexible DC power supply is set to zero. Exemplarily, in the case where the virtual damping is set to zero, as shown below, when the load changes, the power distribution between the synchronous power supply and the network-forming flexible DC power supply is only related to the primary frequency regulation, and the influence on the primary frequency regulation characteristics can be effectively avoided.

[0070]

[0071] For the method of the above embodiment, setting the virtual damping to zero can effectively eliminate the influence of the virtual damping coefficient on the primary frequency regulation characteristics of the network-forming flexible DC power supply, making the power distribution between the synchronous power supply and the network-forming flexible DC power supply only related to primary frequency regulation, and effectively avoiding the influence on the primary frequency regulation characteristics.

[0072] In some embodiments, before adding a first-order inertia link to the primary frequency regulation branch of the network-forming flexible DC power supply to obtain the adjusted frequency characteristics of the network-forming flexible DC power supply, the method further includes: Determine the correspondence between the network-forming power supply capacity and the governor inertia time constant; According to the correspondence between the network-forming power supply capacity and the governor inertia time constant, determine the governor inertia time constant.

[0073] Specifically, in the embodiments of the present application, a functional relationship is established between the network-forming power supply capacity and the governor inertia parameter based on the damping ratio method, providing a basis for the parameter design of network-forming flexible DC power supplies with different capacities.

[0074] Optionally, the damping ratio expression of the network-forming power supply is:

[0075] Based on the automatic control theory, the damping ratio interval can be set to [0.707, 1], and at this time, it has better dynamic performance.

[0076] Furthermore, for network-forming flexible DC power supplies with different capacities, the virtual inertia and the primary frequency regulation coefficient kw have different values. Among them:

[0077] When the virtual inertia and the primary frequency regulation coefficient are selected, for the network-forming governor inertia time constant, the following functional relationship can be used for design:

[0078] For the method of the above embodiment, a functional relationship is established between the network-forming power supply capacity and the governor inertia parameter based on the damping ratio method, thereby providing a basis for the parameter design of network-forming flexible DC power supplies with different capacities; and then, according to the correspondence between the network-forming power supply capacity and the governor inertia time constant, the governor inertia time constant under different capacities can be accurately determined, effectively improving the dynamic performance.

[0079] Exemplarily, an embodiment of the present application further provides a control system for parallel connection of a synchronous machine and a network-forming flexible DC power supply. Among them, the traditional synchronous machine power supply and the network-forming flexible DC power supply are connected in parallel for power generation, and the network-forming flexible DC power supply adopts virtual synchronous machine control; the governor inertia module of the network-forming flexible DC power supply is used to simulate the governor inertia of the synchronous machine and reduce the frequency characteristic difference between the two types of power supplies; the primary frequency modulation calculation module of the network-forming flexible DC power supply is used to calculate the primary frequency modulation compensation power according to the frequency difference of the network-forming power supply; the angular frequency calculation module of the network-forming flexible DC power supply is used to calculate the angular frequency and power angle of the network-forming flexible DC power supply through the difference between the mechanical power and the electromagnetic power of the system via the virtual inertia and damping links; the virtual impedance control module of the network-forming flexible DC power supply is used for current limiting of the converter after a transient fault occurs in the system; the voltage and current control module of the network-forming flexible DC power supply is used to calculate the power decoupling of the network-forming flexible DC power supply to obtain the reference voltage of the network-forming converter; the converter PWM control module of the network-forming flexible DC power supply is used to generate the control switch signal of the network-forming converter. That is, the network-forming flexible DC power supply obtains the switch control signal of the network-forming flexible DC power supply converter through the primary frequency modulation and voltage regulation module, the power loop control module, the virtual impedance module, the voltage and current control module, and the PWM modulation module.

[0080] Exemplarily, as Figure 2 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 as follows: Establish a mathematical model of the synchronous power supply and the network-forming flexible DC power supply and compare the frequency characteristic differences between the two types of power supplies. Subsequently, improve the primary frequency modulation control link of the network-forming flexible DC power supply, add a first-order inertia link in the primary frequency modulation branch to simulate the governor inertia of the synchronous power supply, and reduce the frequency characteristic difference between the synchronous power supply and the network-forming flexible DC power supply; at the same time, cancel the virtual damping control link to prevent the virtual damping coefficient of the network-forming power supply from affecting power distribution. Finally, establish the functional relationship between the capacity of the network-forming power supply and the governor inertia parameter to provide a basis for the parameter design of network-forming flexible DC power supplies with different capacities.

[0081] Through the reshaping of the frequency characteristics of the network-forming flexible DC power supply, the present application can effectively suppress the active power oscillation when the synchronous power supply and the network-forming flexible DC are connected in parallel, without affecting the power distribution between the power supplies, and without increasing additional hardware costs.

[0082] Exemplarily, to verify the power oscillation suppression method and system for parallel connection of the synchronous machine and the network-forming flexible DC power supply in the present application, a regional power grid model as Figure 3 shown is built using the MATLAB / Simulink simulation platform. The converter of the network-forming flexible DC power supply adopts virtual synchronous machine control, and the output of the converter is connected to the bus through a filter and a transmission line.

[0083] First, set the relevant simulation parameters. In this embodiment, the relevant parameters in the control strategy are set as follows: Synchronous generator: diesel engine set model, rated power 80 kW, rated voltage 380 V, moment of inertia M = 5 s, governor time constant Tg = 0.2 s, primary frequency regulation coefficient Kdroop = 105 kW / Hz.

[0084] Grid-forming flexible DC power supply: the energy storage converter adopts double-loop VSG control, rated power 80 kW, DC bus voltage 800 V, virtual inertia Jvsg = 4 s, primary frequency regulation coefficient Kdroop = 105 kW / Hz, cancel the virtual damping coefficient (Dvsg = 0), and add a first-order inertia link (time constant Tvsg = 0.2 s).

[0085] Grid connection: filter parameters Lf = 2 mH, Cf = 50 μF, transmission line impedance Zline = 0.02 Ω + 0.2 mH, bus voltage 380 V / 50 Hz.

[0086] Among them, the control structure diagrams of the synchronous machine and the conventional grid-forming flexible DC power supply in the related technology are as shown in Figure 4a and Figure 4b shown. The control block diagram of the grid-forming flexible DC power supply in the embodiment of the present application (as shown in Figure 5 shown) includes: Power calculation module: generate active power Pvsg based on the instantaneous power theory; First-order inertia link: transfer function G(s) = 1 / (1 + 0.2s), simulating the governor characteristics of the synchronous machine; Rotor motion equation: Jvsg(dω / dt) = Pref - Pvsg, outputting the frequency command fvsg.

[0087] Next, set the simulation conditions. In the initial stable state, each of the two types of power supplies undertakes a 40 kW load; at 4 s, an 80 kW load is connected at the bus, and the simulation ends at 7 s. The changes in the active power of the two types of power supplies before and after the improvement of the grid-forming flexible DC power supply control are as shown in Figure 6 shown. The output power of the power supply is represented in per-unit with 80 kW as the base value.

[0088] From Figure 6It can be seen from the simulation results that when the conventional network-forming flexible DC power supply operates in parallel with the traditional synchronous machine type power supply, due to the large differences in the frequency characteristics of the two types of power supplies, when encountering external load disturbances, the active power oscillations in the transient processes of the two types of power supplies are obvious, with an obvious peak at t = 4.5 s, and then the oscillations gradually weaken and tend to be stable at t = 5.5 s. After reshaping the frequency characteristics of the network-forming flexible DC power supply, the differences in the frequency characteristics of the two types of power supplies are reduced. When encountering external load disturbances, the power distribution between the two types of power supplies is significantly improved during the transient process. There is no obvious peak in the entire transition process, the transition process is stable, and the parallel operation characteristics are greatly improved.

[0089] Optionally, the quantization index verification is shown in Table 1: Table 1

[0090] In summary, the solution of the present application can be directly applied to the converter of the network-forming flexible DC power supply based on virtual synchronous control. Add a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power supply to simulate the governor inertia of the synchronous machine, complete the reshaping of the frequency characteristics of the network-forming flexible DC power supply, reduce the difference in the frequency characteristics between the synchronous machine and the network-forming flexible DC power supply, thereby effectively reducing the transient power oscillations of the two types of power supplies when the load changes, and improving its parallel operation quality and safety. Further, to prevent the virtual damping coefficient of the network-forming flexible DC power supply from affecting power distribution, eliminate the virtual damping control link; on this basis, establish a functional relationship between the network-forming power supply capacity and the governor inertia parameter based on the damping ratio method, providing a basis for the parameter design of network-forming flexible DC power supplies with different capacities. At the same time, this system does not rely on communication and does not require additional hardware circuits, improving the flexibility and economy of the system.

[0091] Next, 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 will be described. The control device for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply described below can be mutually referred to the control method for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply described above. The control device for the parallel operation of the synchronous power supply and the network-forming flexible DC power supply in the embodiment of the present application is as Figure 7 shown and includes: A determination module 710, configured to determine the frequency characteristics of the synchronous power supply and the network-forming flexible DC power supply; An adjustment module 720, configured to add a first-order inertia link to the primary frequency modulation branch of 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, to obtain the adjusted frequency characteristics of the network-forming flexible DC power supply; the first-order inertia link is used to simulate the governor inertia of the synchronous power supply; A control module 730 is configured to perform power distribution between the synchronous power source and the network-forming flexible DC power source according to the adjusted frequency characteristics of the network-forming flexible DC power source.

[0092] Figure 8 FIG. shows a schematic physical structure diagram of an electronic device, which may include: a processor 810, a communication interface 820, a memory 830, and a communication bus 840. Among them, the processor 810, the communication interface 820, and the memory 830 communicate with each other through the communication bus 840. The processor 810 can call the logical instructions in the memory 830 to execute a control method for parallel operation of a synchronous power source and a network-forming flexible DC power source. The method includes: determining the frequency characteristics of the synchronous power source and the network-forming flexible DC power source; adding a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power source according to the difference between the frequency characteristics of the synchronous power source and the network-forming flexible DC power source to obtain the adjusted frequency characteristics of the network-forming flexible DC power source; the first-order inertia link is used to simulate the governor inertia of the synchronous power source; performing power distribution between the synchronous power source and the network-forming flexible DC power source according to the adjusted frequency characteristics of the network-forming flexible DC power source.

[0093] In addition, when the logical instructions in the above-mentioned memory 830 are implemented in the form of software function units and sold or used as an independent product, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs that can store program codes.

[0094] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program 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 a synchronous power source and a network-forming flexible DC power source provided by the above-mentioned various methods. The method includes: determining the frequency characteristics of the synchronous power source and the network-forming flexible DC power source; adding a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power source according to the difference between the frequency characteristics of the synchronous power source and the network-forming flexible DC power source to obtain the adjusted frequency characteristics of the network-forming flexible DC power source; the first-order inertia link is used to simulate the governor inertia of the synchronous power source; and performing power distribution between the synchronous power source and the network-forming flexible DC power source according to the adjusted frequency characteristics of the network-forming flexible DC power source.

[0095] In another aspect, the present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it realizes the control method for parallel operation of a synchronous power source and a network-forming flexible DC power source provided by the above-mentioned various methods. The method includes: determining the frequency characteristics of the synchronous power source and the network-forming flexible DC power source; adding a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power source according to the difference between the frequency characteristics of the synchronous power source and the network-forming flexible DC power source to obtain the adjusted frequency characteristics of the network-forming flexible DC power source; the first-order inertia link is used to simulate the governor inertia of the synchronous power source; and performing power distribution between the synchronous power source and the network-forming flexible DC power source according to the adjusted frequency characteristics of the network-forming flexible DC power source.

[0096] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0097] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence, or the part that contributes to the prior art can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disc, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0098] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A control method for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply, characterized in that, Including: Determine the frequency characteristics of the synchronous power source and the network-forming flexible DC power source; wherein, the frequency characteristics of the synchronous power source include: ； Among them, is the primary frequency regulation coefficient of the synchronous power source; M is the inertia time constant of the synchronous power source; s is a variable on the complex plane; is the damping coefficient of the synchronous power source; is the governor inertia time constant; The frequency characteristics of the network-forming flexible DC power source include: ； Among them, is the virtual inertia; and are the angular frequencies; s is a variable in the complex plane; D is the virtual damping; is the primary frequency regulation coefficient; According to the difference between the frequency characteristics of the synchronous power source and the frequency characteristics of the network-forming flexible DC power source, add a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power source to obtain the adjusted frequency characteristics of the network-forming flexible DC power source; the first-order inertia link is used to simulate the governor inertia of the synchronous power source; According to the adjusted frequency characteristics of the network-forming flexible DC power source, perform power distribution between the synchronous power source and the network-forming flexible DC power source.

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: ; Wherein, T is the first-order inertia time constant; 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, wherein The adjusted frequency characteristics of the network-forming flexible DC power source include: ; Among them, is the angular frequency; T is the governor inertia time constant; s is a variable in the complex plane; is the virtual inertia; D is the virtual damping; is the primary frequency regulation 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 network-forming flexible DC power source, the method further includes: Set the 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 to the primary frequency modulation branch of the network-forming flexible DC power source to obtain the adjusted frequency characteristics of the network-forming flexible DC power source, the method further includes: Determine the corresponding relationship between the network-forming power source capacity and the governor inertia time constant; According to the corresponding relationship between the network-forming power source capacity and the governor inertia time constant, determine the governor inertia time constant.

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-forming power source capacity and the governor inertia time constant includes: ; Among them, H is the inertia time constant of the synchronous machine; S is the capacity of the network-forming power source; T is the inertia time constant of the governor; is the damping ratio of the network-forming power source; is the primary frequency regulation coefficient of the synchronous power source; is the angular frequency.

7. A control device for the parallel operation of a synchronous power supply and a network-forming flexible DC power supply, characterized in that, Including: A determination module, configured to determine the frequency characteristics of the synchronous power source and the network-forming flexible DC power source; wherein, the frequency characteristics of the synchronous power source include: ； Among them, is the primary frequency regulation 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 governor inertia time constant; The frequency characteristics of the network-forming flexible DC power source include: ； Among them, is the virtual inertia; and are the angular frequencies; s is a variable in the complex plane; D is the virtual damping; is the primary frequency regulation coefficient; An adjustment module, configured to add a first-order inertia link to the primary frequency modulation branch of the network-forming flexible DC power source according to the difference between the frequency characteristics of the synchronous power source and the frequency characteristics of the network-forming flexible DC power source, to obtain the adjusted frequency characteristics of the network-forming flexible DC power source; the first-order inertia link is used to simulate the governor inertia of the synchronous power source; A control module, configured to perform power distribution between the synchronous power source and the network-forming flexible DC power source according to the adjusted frequency characteristics of the network-forming flexible DC power source.

8. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the control method for parallel operation of the synchronous power source and the network-forming flexible DC power source according to 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 the processor, it implements the control method for parallel operation of the synchronous power source and the network-forming flexible DC power source according to any one of claims 1 to 6.

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