Virtual synchronous generator multi-machine parallel power distribution method

Abstract

The invention provides a virtual synchronous generator multi-machine parallel power distribution method, which belongs to the field of motors and power electronics, and comprises the following steps: 1, initializing necessary parameters, and monitoring the state of a power grid in real time; 2, predicting and controlling the dynamic response of the VSG by establishing a small signal model of VSG parallel operation; step 3, dynamically adjusting operation parameters of the VSG; and 4, executing a power distribution strategy by the system, distributing the calculated power to each VSG, and monitoring the process to ensure the uniformity of power distribution. According to the method, power distribution is carried out by preferentially utilizing photovoltaic output, the utilization rate of renewable energy sources is remarkably improved, meanwhile, optimal distribution of loads between the parallel virtual synchronous generators is achieved, the inertia and damping of the system are optimized, and the optimal distribution of the loads between the parallel virtual synchronous generators is achieved through a self-adaptive adjustment control strategy. And the advantage of parameter adjustability of the virtual synchronous generator is fully exerted, so that the control effect is further improved, and the stability of the power grid is enhanced.

Description

Technical Field

[0001] The present invention mainly relates to the field of motors and power electronics, and in particular to a method for distributing power of multiple virtual synchronous generators in parallel. Background Art

[0002] With the development of new energy generation technology, especially the widespread application of wind and solar energy, the power system is facing unprecedented challenges. With the popularization of new energy generation methods such as wind and solar energy, the proportion of traditional synchronous generators in the power grid is decreasing, which leads to a decrease in the frequency regulation and peak regulation capabilities of the power grid.

[0003] Although these new energy power generation devices are environmentally friendly and renewable, they lack the ability to respond quickly to changes in grid frequency and voltage compared to traditional synchronous generators, which limits their supporting role for grid stability and reliability. Summary of the invention

[0004] The present invention mainly provides a virtual synchronous generator multi-machine parallel power distribution method to solve the technical problems raised in the above background technology.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A virtual synchronous generator multi-machine parallel power distribution method comprises the following steps:

[0007] Step 1: Initialize necessary parameters and monitor the grid status and load demand, as well as the status of photovoltaic output and energy storage units in real time;

[0008] Step 2: Predict and control the dynamic response of VSG by establishing a small signal model of VSG parallel operation;

[0009] Step 3: Dynamically adjust the operating parameters of the VSG according to the status of the power grid and other units monitored in step 1;

[0010] Step 4: The system executes the power allocation strategy, allocates the calculated power to each VSG, and monitors the process to ensure the uniformity of power distribution.

[0011] Furthermore, in the present invention, the allocation method further comprises the following steps:

[0012] Step 5: Perform different steps according to the power distribution uniformity monitored in step 4.

[0013] If the power distribution is uneven, proceed to step 2 again;

[0014] If the power distribution is uniform, the current power distribution is maintained.

[0015] Furthermore, in the present invention, the allocation method further comprises the following steps:

[0016] Step 6: In step 5, when the power distribution is uniform, the system continuously monitors the operating status.

[0017] If the system operates stably, record the relevant data during stable operation;

[0018] If the system cannot operate stably, proceed to step 1 again.

[0019] Furthermore, in the present invention, in the step 2, the small signal model of VSG parallel operation can obtain the transfer function between the output power of each virtual synchronous generator and the load power, and obtain the parameter matching constraints by making the parameters of each virtual synchronous generator operating in parallel proportional. Using these constraints, the control parameters of each virtual synchronous generator are obtained under different working modes of the microgrid system, thereby realizing reasonable power distribution.

[0020] Furthermore, in the present invention, in step four, the power allocation strategy needs to ensure that the inverter outputs the photovoltaic output on the DC side first by adjusting the power allocation coefficient and the power reference value under different working modes, and the remaining load power is allocated according to the remaining capacity of the inverter, so as to maximize the use of renewable energy.

[0021] Furthermore, in the present invention, voltage compensation is added to the reactive loop of each virtual synchronous generator.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention significantly improves the utilization rate of renewable energy by giving priority to photovoltaic output for power distribution. This method not only optimizes the system inertia and damping, but also gives full play to the advantage of adjustable parameters of virtual synchronous generators through adaptive adjustment control strategy, thereby further improving the control effect and enhancing the stability of the power grid;

[0024] (2) This method reduces the charging and discharging frequency of the energy storage system through a reasonable power allocation mechanism, which not only improves the efficiency of the energy storage system but also extends its service life. In the event of a sudden power change in the power grid, this technology can effectively reduce power fluctuations, optimize the transient process of the system, and provide a more stable and reliable power supply.

[0025] (3) The method also exhibits strong adaptability and can adapt to different working modes. It can also achieve optimal load distribution among parallel virtual synchronous generators by dynamically adjusting the controller parameters of the virtual synchronous generators. This flexibility solves the limitations of existing virtual synchronous generator control methods in utilizing renewable energy and ensures the stable operation of the power grid when a high proportion of new energy is connected to the grid.

[0026] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a control flow chart of the allocation method of the present invention;

[0028] Figure 2 It is the voltage and current waveform diagram of the single unit output of the virtual synchronous generator;

[0029] Figure 3 It is a comparison diagram of active and reactive power output of a single virtual synchronous generator;

[0030] Figure 4 It is a curve diagram of the changes in system frequency and voltage caused by load changes during the simulation process;

[0031] Figure 5 This is a comparison diagram of the active power output difference of the two virtual synchronous generators during the simulation process. DETAILED DESCRIPTION

[0032] To facilitate understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings, but the present invention can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the content disclosed in the present invention more thorough and comprehensive.

[0033] It should be noted that when an element is referred to as being "fixed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are for illustrative purposes only.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0035] For examples, please refer to the attached Figure 1 , a virtual synchronous generator multi-machine parallel power distribution method, comprising the following steps:

[0036] Step 1: Initialize necessary parameters and monitor the grid status and load demand, as well as the status of photovoltaic output and energy storage units in real time;

[0037] Step 2: Predict and control the dynamic response of VSG by establishing a small signal model of VSG parallel operation;

[0038] Step 3: Dynamically adjust the operating parameters of the VSG according to the status of the power grid and other units monitored in step 1;

[0039] Step 4: The system executes the power allocation strategy, allocates the calculated power to each VSG, and monitors the process to ensure the uniformity of power distribution.

[0040] Furthermore, the allocation method further comprises the following steps:

[0041] Step 5: Perform different steps according to the power distribution uniformity monitored in step 4.

[0042] If the power distribution is uneven, proceed to step 2 again;

[0043] If the power distribution is uniform, the current power distribution is maintained.

[0044] Furthermore, the allocation method further comprises the following steps:

[0045] Step 6: In step 5, when the power distribution is uniform, the system continuously monitors the operating status.

[0046] If the system operates stably, record the relevant data during stable operation;

[0047] If the system cannot operate stably, proceed to step 1 again.

[0048] It should be noted that, in this embodiment, the entire control logic forms a closed loop, aiming to achieve efficient and stable operation of the VSG multi-machine parallel system.

[0049] Furthermore, in the step 2, the small signal model of VSG parallel operation can obtain the transfer function between the output power of each virtual synchronous generator and the load power, and obtain the parameter matching constraints by making the parameters of each virtual synchronous generator operating in parallel proportional. Using these constraints, the control parameters of each virtual synchronous generator are obtained under different working modes of the microgrid system, thereby realizing reasonable power distribution.

[0050] Furthermore, in step 4, the power allocation strategy needs to ensure that the inverter outputs the photovoltaic power on the DC side first by adjusting the power allocation coefficient and the power reference value in different working modes, and the remaining load power is allocated according to the remaining capacity of the inverter, so as to maximize the use of renewable energy;

[0051] It should be noted that, in this embodiment, this step considers the integration of the DC-side photovoltaic output and the energy storage unit to maintain a constant DC bus voltage and compensate for the random volatility of the primary energy output, thereby maximizing the use of renewable energy.

[0052] Furthermore, voltage compensation is added to the reactive loop of each virtual synchronous generator.

[0053] It should be noted that, in this embodiment, voltage compensation is used to ensure the consistency of output voltages of various virtual synchronous generators, reduce system circulating current, and improve the accuracy of power distribution.

[0054] In this embodiment, the research method of power allocation of multiple virtual synchronous generators in parallel is as follows:

[0055] A. Establishing a mathematical model

[0056] First, mathematical models of virtual synchronous generators (VSGs) are needed, including active-frequency control and reactive-voltage control. These models draw on the frequency regulation, voltage regulation, and rotor motion equations of synchronous generators to design VSG models that can simulate the characteristics of synchronous generators.

[0057] B. Control Strategy Development

[0058] Design a control strategy that includes virtual impedance and virtual power control to achieve efficient power distribution among multiple VSGs, including adaptive virtual impedance droop control, which is a common grid-connected inverter control strategy for coordinated operation of multiple inverters;

[0059] C. Parameter Optimization

[0060] Determine VSG characteristic parameters such as inertia, damping coefficient and droop coefficient to optimize the system dynamic performance. The design criteria of these parameters are to achieve inertia matching when multiple VSGs are operated in parallel, thereby suppressing power oscillations and reducing frequency changes.

[0061] The VSG model can simulate the dynamic characteristics of traditional synchronous generators, provide the inertia and damping required by the power grid, and enhance the stability of the system; dynamically adjust the output through adaptive control strategies to achieve reasonable power distribution; and have strong adaptability and intelligent control capabilities to optimize the dynamic performance of the power grid and improve its responsiveness to various working conditions;

[0062] The control strategy of virtual impedance and virtual power control can realize the decoupling of power control, improve the dynamic response speed and power distribution effect of the system by adaptively adjusting the virtual impedance and droop coefficient, and introduce virtual inertia control to simulate the inertia and damping characteristics of traditional generators, enhance the stability and reliability of the power grid, effectively suppress power oscillation, and realize accurate power distribution when multiple machines are operated in parallel.

[0063] Moreover, the optimization of the VSG characteristic parameters can dynamically adjust the virtual inertia (J), damping coefficient (D) and droop coefficient (Kω) through adaptive control strategies to improve the dynamic response and stability of the system; the optimization of these parameters can simulate the inertia and damping characteristics of traditional synchronous generators, thereby providing the necessary frequency and voltage support for the power grid. The kinetic energy reserve represented by the virtual inertia J determines the dynamic response speed when disturbed; the damping coefficient D is used to consume excess energy in the system and help the system return to a stable state faster. By reasonably configuring these parameters, power oscillations can be effectively suppressed, frequency changes can be reduced, and the stability and controllability of the system can be improved.

[0064] For details, please refer to the attached Figure 2 and attached Figure 3 , a simulation example of two VSGs in parallel is conducted. Two 40kW and 10kvar loads are set in the line. The simulation time is 1s. A 40kW and 10kvar load is added at 0.5s. The power absorbed by the load is evenly divided by the two VSG devices. Therefore, after 0.5s, the active power and reactive power output by the two machines increase by 20kW and 5kvar respectively. It can be seen from the voltage and current waveforms of the single machine output that the voltage output of the single machine is basically stable at 311V during stable operation. The voltage will drop slightly when the load is put into use, but it will quickly recover to 311V. In addition, the addition of the load increases the current output by the VSG at 0.5s.

[0065] Attached Figure 4 The curve of the system frequency and voltage changes caused by load changes during the simulation process. The changes in the VSG active and reactive power instructions will cause the system frequency and voltage to drop or rise. In the simulation example of the present invention, the active and reactive power instructions increase, so the system frequency and voltage will decrease;

[0066] The power of the load in the simulation example of the present invention is evenly distributed by two VSGs. Before 0.5s, the two VSGs each provide 40kW of active power and 10kvar of reactive power to the load. After 0.5s, a load of 40kW and 10kvar is put into use. At this time, the active power and reactive power output by the two VSGs increase by 20kW and 5kvar respectively. Figure 5It can be seen from the image of the active power output difference of the two machines that the output active power of the two machines is different when the system starts and the load changes suddenly, so the difference curve will oscillate. However, as the operating state of the system tends to be stable, the output difference of the two machines is close to 0, which verifies the effectiveness of the patented method of this invention.

[0067] The development of virtual synchronous generator technology enables new energy power generation equipment to be better integrated into the power grid, providing primary frequency and voltage regulation functions similar to traditional generators. This technological advancement not only improves the power grid's ability to accept new energy, but also enhances the grid's ability to absorb fluctuating energy. In addition, the development of grid-building new energy power generation technology, through appropriate control algorithms, gives new energy power generation equipment more autonomy, enabling it to autonomously maintain the frequency and voltage of the power grid, further promoting the application of new energy technologies.

[0068] The emergence of virtual power plant technology provides a new approach to the frequency regulation of power grids. It aggregates distributed power sources, demand-side response resources and energy storage devices to participate in the dispatch of power grids as a whole, demonstrating fast and accurate dynamic response capabilities. The application of this technology not only improves the flexibility and reliability of the power grid, but also provides strong support for the stable operation of the power grid.

[0069] In the UPS power supply and photovoltaic storage multi-machine parallel system, high-precision load distribution technology quickly adjusts the voltage, frequency and phase parameters through digital algorithms to ensure the stability of the parallel system. The application of these technologies enables the parallel system to operate reliably in the face of parameter deviations, improving the flexibility and reliability of the system. The common goal of these technologies is to improve the grid's ability to accept new energy, ensure the stable operation of the grid, and provide a solid technical foundation for the widespread application of new energy power generation.

[0070] The above is an exemplary description of the present invention in combination with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as such non-substantial improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for allocating power of multiple virtual synchronous generators in parallel, characterized in that: The following steps are involved: Step 1: Initialize necessary parameters and monitor the grid status and load demand, as well as the status of photovoltaic output and energy storage units in real time; Step 2: Predict and control the dynamic response of VSG by establishing a small signal model of VSG parallel operation; Step 3: Dynamically adjust the operating parameters of the VSG according to the status of the power grid and other units monitored in step 1; Step 4: The system executes the power allocation strategy, allocates the calculated power to each VSG, and monitors the process to ensure the uniformity of power distribution.

2. A virtual synchronous generator multi-machine parallel power distribution method according to claim 1, characterized in that: The allocation method further comprises the following steps: Step 5: Perform different steps according to the uniformity of power distribution monitored in step 4. If the power distribution is uneven, perform step 2 again; If the power distribution is uniform, the current power distribution is maintained.

3. A method for allocating power of multiple virtual synchronous generators in parallel according to claim 1, characterized in that: The allocation method further comprises the following steps: Step 6: In step 5, when the power distribution is uniform, the system continuously monitors the operating status. If the system operates stably, record the relevant data during stable operation; If the system cannot operate stably, proceed to step 1 again.

4. A method for allocating power of multiple virtual synchronous generators in parallel according to claim 1, characterized in that: In the step 2, the small signal model of VSG parallel operation can obtain the transfer function between the output power of each virtual synchronous generator and the load power. By making the parameters of each virtual synchronous generator operating in parallel proportional, the constraint conditions for parameter matching are obtained. Using these constraints, the control parameters of each virtual synchronous generator are obtained under different working modes of the microgrid system, thereby achieving reasonable power distribution.

5. The method for allocating power of multiple virtual synchronous generators in parallel according to claim 1, characterized in that: In step 4, the power allocation strategy needs to adjust the power allocation coefficient and the power reference value in different working modes to ensure that the inverter outputs the photovoltaic power on the DC side first, and the remaining load power is allocated according to the remaining capacity of the inverter, so as to maximize the use of renewable energy.

6. A method for allocating power of multiple virtual synchronous generators in parallel according to claim 1, characterized in that: Voltage compensation is added to the reactive loop of each virtual synchronous generator.

Images