VSG inertia and damping adaptive coordination control method and device

Abstract

The invention provides a VSG inertia and damping adaptive coordination control method, and belongs to the technical field of virtual synchronous generator control. Research finds that the oscillation process can be segmented, and in each segment, the inertia and damping coefficient requirements are different. Based on the relevance between the rotational inertia / damping coefficient and the system angular frequency offset / angular frequency change rate, the arctan function is used in the control strategy provided by the invention to participate in adjusting the system inertia and damping change, and the advantage that the rotational inertia and damping coefficient parameters of the virtual synchronous machine are flexible and adjustable is fully utilized; the relevance between the angular frequency change rate / angular frequency offset and the rotational inertia / damping coefficient is studied. Through cooperative control of the rotational inertia and the damping coefficient, when the system is disturbed, sufficient inertia support can be provided, the frequency change of the system is stabilized, and the transient process of the frequency and the active power during system load disturbance is effectively improved.

Description

Technical Field

[0001] This application relates to the technical field of virtual synchronous machine control, and particularly to an inertia and damping adaptive coordination control method and device for VSG. Background Technique

[0002] The use of fossil fuels such as coal has promoted the development of social economy. However, the exploitation and utilization of fossil fuels have had a serious impact on local natural resources, bringing a series of environmental problems, such as the emission of greenhouse gases such as carbon dioxide and the generation of haze problems, which pose a great threat to human life safety. Therefore, while ensuring the rapid development of human society and economy, we should protect the environment and adjust the resource structure. So more and more countries have begun to seek environmentally friendly and renewable alternative energy sources. The future development trend is to use clean energy to replace traditional fossil fuels.

[0003] The application of clean energy such as photovoltaic and wind power has become an important trend in the development of future power systems. Since a large number of power electronic devices are used when new energy is connected to the grid, the overall inertia level of the power grid system is reduced, affecting the stability of the system, and the system shows the characteristics of low inertia. Virtual Synchronous Generator (VSG), as a new type of inverter technology, can improve the stability of the system by providing inertia and damping to the microgrid, but excessive frequency change rate and frequency deviation during the response process may affect the normal operation of the system and cause adverse effects.

[0004] Application Content

[0005] To solve the above technical problems, this application proposes an inertia and damping adaptive coordination control method and device for VSG.

[0006] The technical solution adopted in this application is: an inertia and damping adaptive coordination control method for VSG, including the following steps:

[0007] Step S1: Construct an inverter model based on VSG that includes moment of inertia and damping coefficient and obtain the rotor motion equation of the virtual synchronous generator according to the classical second-order model of the synchronous generator, construct the active power-frequency characteristic control equation of VSG, and derive the angular frequency change rate and angular frequency offset according to the rotor motion equation and the active power-frequency characteristic control equation;

[0008] Step S2: Divide the oscillation process into four intervals according to the angular frequency oscillation curve;

[0009] Step S3: Based on the correlation between the moment of inertia / damping coefficient and the angular frequency offset / angular frequency change rate, determine the adjustment direction and adjustment amount of the moment of inertia and the damping coefficient;

[0010] Step S4: Introduce the arctan function to participate in the adaptive adjustment strategy of the moment of inertia and the damping coefficient.

[0011] Furthermore, the rotor motion equation of the virtual synchronous generator is as follows:

[0012] ;

[0013] In the formula, is the moment of inertia of the VSG; is the damping coefficient of the VSG; is the power angle; is the mechanical power; is the actual output power of the VSG; is the output angular frequency of the VSG; is the reference angular frequency of the VSG; is the angular frequency offset;

[0014] The active - frequency characteristic control equation of the VSG is:

[0015] ;

[0016] In the formula, is the droop coefficient; is the reference value of the active power;

[0017] Let and , then the active - frequency control equation of the VSG can be further obtained as:

[0018] .

[0019] Furthermore, through the study of the correlation between the system active - frequency control equation and the rotor motion equation, the influence of the system frequency offset factor is deduced, and the study and on the system dynamic regulation leads to:

[0020] ;

[0021] ;

[0022] In the formula, is the difference between the reference value of the active power and the output power of the VSG.

[0023] Furthermore, the four intervals divided in Step S2 are:

[0024] The first interval: The output power of the VSG in this interval is less than the given power , such that it accelerates, and the rate of change of the angular frequency first increases and then slowly decreases to zero, but is always non - negative;

[0025] The second interval: The output power of the VSG is greater than the given power , it is in a gradually decreasing state, and also becomes smaller, but it is still greater than 0;

[0026] The third interval: The output power of the VSG is greater than the given power , , , ;

[0027] The fourth interval: , it increases and approaches the rated frequency, , .

[0028] Furthermore, the adjustment method and adjustment amount of the moment of inertia and damping coefficient in the first interval are: The moment of inertia and the damping coefficient need to be positive values, and increasing the moment of inertia and the damping coefficient ;

[0029] The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the second interval are: Decreasing the moment of inertia , increasing the damping coefficient ;

[0030] The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the third interval are: Increasing the moment of inertia , increasing the damping coefficient ;

[0031] The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the fourth interval are: Decreasing the moment of inertia , increasing the damping coefficient .

[0032] Furthermore, the adaptive adjustment strategy of introducing the arctan function into the virtual moment of inertia in step S4 is:

[0033] ;

[0034] In the formula, is the initial value of the inertia; is the maximum inertia; is the minimum inertia; is the set threshold; is the value positive and negative function.

[0035] Furthermore, the adaptive strategy of introducing the arctan function into the damping coefficient is as follows:

[0036] ;

[0037] In the formula, is the initial damping value; is the proportionality coefficient; is the set threshold.

[0038] Furthermore, it also includes: performing simulation operation and analysis, verifying the effectiveness of the adaptive strategy, and adjusting and optimizing the adaptive strategy according to the simulation results.

[0039] A computer device includes a memory, a processor, and a computer program stored on the memory, and the processor executes the computer program to implement the steps of the method.

[0040] A computer-readable storage medium stores a computer program / instructions, and when the computer program / instructions are executed by a processor, the steps of the method are implemented.

[0041] The beneficial effects of this application compared with the prior art are as follows: The adaptive parameter strategy of this application can better smooth the change, reduce the amount, improve the stability and anti-disturbance ability of the system, enable the system to have good inertia support when being disturbed, and make the system have good robustness.

[0042] This application first conducts a relational analysis on the rotor motion equation and the active power frequency characteristic equation, thereby deriving the active power frequency equation, and can obtain the relationship between and and the virtual moment of inertia and damping coefficient. Analyze the influence of the moment of inertia, damping coefficient, and droop coefficient on the system angular frequency change rate and angular frequency deviation, then divide the system oscillation period according to the characteristics of the angular frequency oscillation and power oscillation, and formulate corresponding adaptive inertia and damping control strategies according to the change characteristics of the system angular frequency offset and angular frequency change rate in each partition and the influence of the virtual inertia and damping coefficient on the angular frequency deviation and angular frequency change rate. Description of the Drawings

[0043] The following further describes this application with reference to the drawings:

[0044] Figure 1It is the flowchart of the method given in the embodiments of the present application.

[0045] Figure 2 It is the overall structure diagram of the virtual synchronous generator for the power grid system given in the embodiments of the present application.

[0046] Figure 3 It is the frequency change diagram of the sudden change of the active power reference value in the present application.

[0047] Figure 4 It is the active power change diagram of the sudden change of the active power reference value in the present application.

[0048] Figure 5 It is the moment of inertia under the adaptive control strategy of the change curve graph.

[0049] Figure 6 It is the damping coefficient under the adaptive control strategy of the change curve graph. Specific implementation manners

[0050] As Figures 1 to 6 shown, the present application provides an inertia and damping adaptive coordinated control method for VSG, which is an adaptive inertia damping control strategy. The entire VSG has a power calculation module, an active frequency control module, a reactive voltage control module, a voltage and current double closed-loop control module, etc. These modules are linked according to the logical relationship and are used to output various required physical quantities. The implementation steps of the method are as follows:

[0051] Step S1: Based on the control idea of the virtual synchronous generator (VSG), construct an inverter model including the moment of inertia and the damping coefficient , and introduce the parameters and into the inverter control by establishing the VSG active loop equation and the VSG reactive loop equation; as Figure 2 shown, where the inverter model includes a power calculation module, an active frequency control module, a reactive voltage control module, and a voltage and current double closed-loop control module.

[0052] According to the inverter model of the virtual synchronous generator, the rotor motion equation of the virtual synchronous generator can be obtained as:

[0053] ;

[0054] In the formula, is the moment of inertia of the VSG; is the damping coefficient of the VSG; is the power angle; is the mechanical power; is the actual output power of the VSG; is the output angular frequency of the VSG; is the reference angular frequency of the VSG; is the angular frequency offset, , which can also be called the angular frequency deviation.

[0055] The active-power - frequency characteristic control equation of the VSG is:

[0056] ;

[0057] In the formula, is the droop coefficient; is the reference value of the active power.

[0058] Let and , then the active-power - frequency control equation of the VSG can be further obtained as:

[0059] ;

[0060] By studying the correlation between the active-power - frequency control equation of the system and the rotor motion equation, the influence on the system frequency offset factor can be deduced. Studying and on the dynamic regulation of the system, it can be concluded that:

[0061] ;

[0062] ;

[0063] In the formula, is the difference between the reference value of the active power and the output power of the VSG;

[0064] When the numerator on the right side is constant, increasing the rotational correlation of the VSG, will decrease accordingly, and thus the frequency change will be smoother; it can also be known that when the numerator on the right side of the equation is constant, the sum of the damping coefficient and the droop coefficient is inversely proportional to the frequency deviation. Increasing or can both reduce the angular frequency change amount, that is, reduce the overshoot during frequency dynamic regulation.

[0065] The magnitudes of the moment of inertia and damping coefficient of the VSG will affect the anti-disturbance performance of the system frequency. Therefore, this characteristic can be utilized to improve the dynamic response characteristic of the system frequency by adjusting relevant control parameters.

[0066] Step S2: Study the law of the angular frequency offset and change rate output by the VSG, and divide the oscillation process into four intervals according to the angular frequency oscillation curve; in this embodiment, the first oscillation period after the angular frequency oscillates and then decays and recovers can be divided into four intervals.

[0067] Step S3: Based on the correlation between the moment of inertia / damping coefficient and the angular frequency offset / angular frequency change rate, determine the adjustment direction and adjustment amount of the moment of inertia and the damping coefficient;

[0068] ① The first interval: The output power of the VSG in this interval is less than the given power , so that accelerates, and the angular frequency change rate first increases and then slowly decreases to zero, but is always non - negative. Therefore, the primary task in this interval is to suppress the sudden increase in the angular frequency change rate; in this region, the moment of inertia and the damping coefficient need to be positive, and since the frequency offset and power offset are positive, the values of and need to be appropriately increased to suppress the change of ; similarly, due to the increase of and , the maximum value of the frequency deviation amount is also suppressed.

[0069] ② The second interval: Since the output power of the VSG is greater than the given power , is in a gradually decreasing state, also decreases accordingly, but the deviation amount is still greater than 0; in this interval, the value of should be appropriately reduced and the value of should be appropriately increased to accelerate the recovery of the system frequency and reduce the frequency offset amount.

[0070] ③ The third interval: The output power of the VSG is greater than the given power , , , ; in this interval shifts in the negative direction, and the frequency change rate needs to be reduced. Therefore, the moment of inertia and the damping coefficient should be appropriately increased, which not only slows down the angular frequency change rate but also reduces the angular frequency offset amount.

[0071] ④ The fourth interval: , and increases and approaches the rated frequency, , , so in this interval, it should be appropriately reduced Take the value of and appropriately increase it to reduce the deviation of

[0072] and at the same time suppress the angular frequency change rate.

[0073] Table 1 Adjustment rules for inertia and damping coefficient are as follows:

[0074] .

[0075] Table 1 shows the change trends of and in each interval of the angular frequency oscillation period during the dynamic regulation process of the system. For each interval, according to the oscillation change trend and the corresponding system requirements, there are different adjustment rules for and . According to the rules shown in Table 1, this application studies the control strategy of adaptive inertia damping.

[0076] Step S4: Introduce the arctan function to participate in the adaptive adjustment strategy of virtual moment of inertia and damping coefficient;

[0077] Based on the characteristics of the physical quantities in several divided intervals, the corresponding moment of inertia adaptive strategy is:

[0078] ;

[0079] In the formula, is the initial value of inertia; is the maximum value of inertia; is the minimum value of inertia; is the set threshold; is the positive and negative value function.

[0080] The adaptive strategy of damping coefficient is:

[0081] ;

[0082] In the formula, is the initial value of damping; is the proportional coefficient; is the set threshold.

[0083] When the angular frequency change reaches the corresponding set threshold, the adaptive inertia damping strategy starts to act, dynamically adjusting the magnitudes of and to meet the system stability requirements and improve the stability and robustness of the power system.

[0084] To verify the effectiveness of this application, the initial operating parameter of the system, the active power reference, is set. It jumps from 2 kW to 10 kW at t = 1 s and returns to 2 kW at t = 2 s. A simulation experiment is carried out under the adaptive control strategy proposed in this application.

[0085] Figure 3 It is the curve graph of the frequency change when the active power reference jumps from 2 kW to 10 kW at 1 s in Example 1 and returns to 2 kW at 2 s. Figure 4 It is the curve graph of the active power output.

[0086] Figure 5 It is the curve graph of the damping change of the adaptive strategy proposed in this example. Figure 6 It is the curve graph of the inertia change of the adaptive strategy proposed in this example.

[0087] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of this application, rather than to limit it; although this application 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 recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An inertia and damping adaptive coordinated control method for VSG, characterized in that: It includes the following steps: Step S1: Construct an inverter model based on VSG that includes moment of inertia and damping coefficient , obtain the rotor motion equation of the virtual synchronous generator according to the classical second-order model of the synchronous generator, construct the active power-frequency characteristic control equation of VSG, and derive the angular frequency change rate and angular frequency offset according to the rotor motion equation and the active power-frequency characteristic control equation; Step S2: Divide the oscillation process into four intervals according to the angular frequency oscillation curve; Step S3: Based on the correlation between the moment of inertia / damping coefficient and the angular frequency offset / angular frequency change rate, determine the adjustment direction and adjustment amount of the moment of inertia and the damping coefficient; Step S4: Introduce the arctan function to participate in the adaptive adjustment strategy of the moment of inertia and the damping coefficient.

2. The inertia and damping adaptive coordinated control method of a VSG according to claim 1, characterized in that: The rotor motion equation of the virtual synchronous generator is as follows: ； Wherein, is the moment of inertia of the VSG; is the damping coefficient of the VSG; is the power angle; is the mechanical power; is the actual output power of the VSG; is the output angular frequency of the VSG; is the reference angular frequency of the VSG; is the angular frequency offset; The active-power / frequency characteristic control equation of the VSG is: ； In the formula, is the sag coefficient; is the reference value of active power; Let and , then the active-power - frequency control equation of the VSG can be further obtained as follows: 。 3. The inertia and damping adaptive coordinated control method of a VSG according to claim 2, characterized in that: Through the study of the correlation between the system active power-frequency control equation and the rotor motion equation, the influence of the system frequency deviation factor is deduced, and the research and The influence on the system dynamic regulation is obtained as follows: ； ； wherein, is the difference between the reference value of the active power and the output power of the VSG.

4. A method for inertia and damping adaptive coordinated control of a VSG according to claim 3, characterized in that: The four intervals divided in Step S2 are: First interval: The output power of the VSG in this interval is less than the given power , such that it accelerates, and the angular frequency change rate first increases and then slowly decreases to zero, but is always non-negative; Second interval: The output power of the VSG is greater than the given power , in a gradually decreasing state, also becomes smaller accordingly, but still remains greater than 0; Third interval: The output power of the VSG is greater than the given power , , , ; Fourth interval: , increases and approaches the rated frequency, , .

5. The inertia and damping adaptive coordinated control method of a VSG according to claim 4, characterized in that: The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the first interval are as follows: the moment of inertia and the damping coefficient need to be positive values, and increasing the moment of inertia and the damping coefficient ; The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the second interval are: reducing the moment of inertia , increasing the damping coefficient ; The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the third interval are as follows: increase the moment of inertia , increase the damping coefficient ; The adjustment method and adjustment amount of the moment of inertia and damping coefficient in the fourth interval are: reduce the moment of inertia , increase the damping coefficient .

6. The inertia and damping adaptive coordinated control method of a VSG according to claim 5, characterized in that: The adaptive adjustment strategy for introducing the arctan function to participate in the virtual moment of inertia in Step S4 is: ； In the formula, is the initial inertia value; is the maximum inertia value; is the minimum inertia value; is the set threshold value; is the positive / negative value-taking function.

7. A method for inertia and damping adaptive coordinated control of a VSG according to claim 5, characterized in that: The adaptive strategy for introducing the arctan function to participate in the damping coefficient is: ； In the formula, is the initial damping value; is the proportionality coefficient; is the set threshold value.

8. A method for inertia and damping adaptive coordinated control of a VSG according to any one of claims 1-7, characterized in that: It also includes: Carry out simulation operation and analysis to verify the effectiveness of the adaptive strategy, and adjust and optimize the adaptive strategy according to the simulation results.

9. A computer device, comprising a memory, a processor, and a computer program stored on the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1-8.

10. A computer-readable storage medium having computer programs / instructions stored thereon, characterized in that: When the computer program / instructions are executed by the processor, the steps of the method according to any one of claims 1-8 are implemented.

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