Index droop control method and system for autonomous networking inverter based on frequency stability

Abstract

The invention discloses an autonomous networking inverter exponential droop control method and system based on frequency stability. The method comprises the following steps: acquiring an input electric signal required by an inverter; an inverter autonomous synchronization phase is generated through an exponential droop controller and an auxiliary autonomous power response controller; generating a reference amplitude of the inverter through the sampled input electrical signal; and a pulse modulation signal of the inverter is generated according to the phase and the reference amplitude generated by the control module. Compared with a traditional linear droop control method, by establishing the nonlinear relation between power output and frequency, the frequency stability and the power utilization rate of the system are remarkably improved, the power output is naturally limited near the maximum power output, higher damping capacity is provided, and the dynamic performance of the system frequency is improved.

Description

Technical Field

[0001] The present invention relates to the field of smart grid control technology, and in particular to an exponential droop control method and system for an autonomous grid-connected inverter based on frequency stability. Background Art

[0002] With the transformation of the global energy structure, the proportion of renewable energy, especially wind power and solar photovoltaic power generation, continues to rise. However, compared with the traditional power system based on synchronous generators, the power generation characteristics of these renewable energy sources are significantly different, mainly reflected in the volatility and unpredictability of output power. These characteristics have brought new challenges to the frequency stability of the power system.

[0003] Traditional power systems rely on synchronous generators to provide inertia and frequency regulation services to ensure system frequency stability. However, renewable energy is usually connected to the grid through power electronic converters. Unlike synchronous generators, they lack inherent mechanical inertia, resulting in reduced system inertia, making the frequency more susceptible to disturbances. Existing linear droop control methods show limitations when dealing with high-penetration renewable energy and cannot effectively deal with frequency fluctuations and high-frequency oscillations. Power electronic converters adopt linear droop control strategies to achieve synchronization and load sharing with the grid by adjusting the active power output response frequency deviation. However, this linear relationship has the following problems in high-penetration renewable energy systems: 1. Poor frequency stability. Linear droop control will cause unstable system frequency response, frequency fluctuations and oscillations in extreme cases of high power output or low power output; 2. High frequency change rate. Due to the lack of mechanical inertia, the system has a high frequency change rate when disturbed, increasing the risk of system instability; 3. Low power utilization. When dealing with the volatility of renewable energy generation, linear droop control cannot fully utilize the system's power headroom, resulting in poor frequency control. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: an exponential droop control method for an autonomous grid-connected inverter based on frequency stability, comprising:

[0006] Obtain the input electrical signal required by the inverter;

[0007] Generates inverter autonomous synchronization phase through exponential droop controller and auxiliary autonomous power response controller;

[0008] generating a reference amplitude of the inverter by sampling the input electrical signal;

[0009] A pulse modulation signal for the inverter is generated according to the phase and reference amplitude generated by the control module.

[0010] As a preferred solution of the frequency stabilization-based exponential droop control method for autonomous grid-connected inverters described in the present invention, the electrical signal includes the voltage and current of the grid-connected point.

[0011] As a preferred solution of the frequency-stabilized autonomous grid-connected inverter exponential droop control method described in the present invention, the exponential droop controller generates the inverter autonomous synchronization phase, including performing a logical judgment on the filtered active power p to obtain a power signal p out1 ;

[0012] If |p| <p max , then p out1 =p; if |p|≥p max , then p out1 =p max ;

[0013] Among them, p max is the inverter output power limit;

[0014] Power signal p out1 Through absolute value inversion processing, the power output is mirror-inverted at the origin, and the exponential signal E is obtained based on the exponential function. I (p out1 );

[0015]

[0016] Among them, α and β are exponential function parameters.

[0017] As a preferred solution of the frequency-stabilized autonomous grid-connected inverter exponential droop control method of the present invention, wherein: the inverter output power limit includes, when the power does not exceed the limit, the derivative of the exponential signal EI(p) with respect to p is;

[0018]

[0019] Make the index signal E I The derivative of (p) with respect to p is equal to D max , so the power limit p max It is expressed as;

[0020]

[0021] As a preferred solution of the frequency-stabilized autonomous grid-connected inverter exponential droop control method described in the present invention, the exponential droop controller generates the inverter autonomous synchronization phase, including an additional power over-limit linearization processing module, through a logical judgment of the filtered active power p, to the power signal p out2 ;

[0022] If |p|≥p max , then p out2 =p; if |p| <p max , then p out2 =p max ;

[0023] The obtained power signal p out2 With power limit p max Subtract and linearize the parameter D max Multiply them to get the additional amount D when the power exceeds the limit max (|p|-p max ), by introducing D max To limit the maximum droop value to ensure stable operation at high power output; additional amount D max (|p|-p max ) and the index signal E I (p out1 ) and then multiplied by the reflection function S(p);

[0024] Finally, the exponential droop module generates a frequency signal D exp ;

[0025]

[0026] Due to D exp The nonlinear droop characteristics of (p) need to be adjusted by the frequency setting value ω set (p set ) to add an additional frequency offset, considering the frequency setting value ω set At different power settings p set Calculation, if |p set |<p max , it is determined that the power limit is not exceeded, the additional amount is equal to 0, and the power signal p in the exponential signal out1 =p; if |p set |≥p max , it is judged as exceeding the power limit, and the additional amount p out2 =p max , the power signal p in the exponential signal out1 =p max ; expressed as:

[0027]

[0028] As a preferred solution of the frequency stabilization-based index droop control method for autonomous grid-connected inverters of the present invention, the auxiliary autonomous power response controller includes adding a frequency offset ω after a disturbance occurs. ps Respond to system frequency fluctuations;

[0029] The frequency deviation of linear droop is;

[0030] ω MD =(p set -p)M D

[0031] Among them, ω MD is the frequency deviation, p set is the power setting value, M D is the linear droop parameter;

[0032] Frequency deviation signal ω MD With exponential droop signal D exp and signal frequency offset ω ps Perform the calculation and get the error ω e ;

[0033] ω e =ω MD +D exp -ω ps

[0034] When the error ω e When the logical judgment conditions are met and recorded; output error ω e,out for;

[0035]

[0036] Among them, ε p and ε dp Both are disturbance tolerance parameters, Δp=pp max , represents the derivative of p with respect to time t;

[0037] When the power fluctuation meets the interference standard, the error ω e,out The frequency offset ω will be generated by an integrator with a gain of k ps ; When e When driven to 0 by the integrator, the converter will be able to achieve M D Specified power output value.

[0038] As a preferred solution of the frequency-stabilized autonomous grid-connected inverter exponential droop control method described in the present invention, wherein: the inverter pulse modulation signal includes an auxiliary autonomous power response control signal ω ps With the exponential droop control signal D exp The difference is calculated and compared with the frequency setting value ω set and nominal frequency setting value ω nom Added and then compared with the frequency reference value ω b Get the actual generation frequency ω I , and then the inverter autonomous synchronization phase δ is obtained through the integrator I ;

[0039] The total output signal of exponential droop control is:

[0040]

[0041] As a preferred solution of the frequency-stabilized autonomous grid-connected inverter index droop control method described in the present invention, it includes: 1. a first inertia link; 2. a first logic judgment module; 3. a first function operation module; 4. a second logic judgment module; 5. a first proportion link; 6. a second function operation module; 7. a first constant module; 8. a first inverting adder; 9. a second inverting adder; 10. a second constant module; 11. a second proportion link; 12. a third proportion link; 13. a first positive adder; 14. a third function operation module; 15. a third inverting adder; 16. a fourth function operation module; 17. a second positive adder; 18. a third positive adder; 19. a fourth proportion link; 20. a third constant module; 21. a first integral link; 22. a fourth constant module; 23. a fourth inverting adder; 24. a fifth proportion link; 25. a fifth inverting adder; 26. a third logic judgment module; 27. a second integral link;

[0042] The measured instantaneous power output p meas The filtered active power p is obtained through the first inertia link, and after the limiting processing is performed by the first logic judgment module, the absolute value inversion processing is performed, and then the exponential signal E is obtained through the first proportional link, the second function operation module, the second inverting adder, the second constant module and the third proportional link. i (p out1 ).

[0043] The filtered active power p is judged by the second logic judgment module, and then combined with the first constant module through the first inverting adder and the second proportional link to obtain the additional amount when the power exceeds the limit. The linearization occurs at the power limit p max where the droop value is equal to D max The control channel is achieved by introducing a constant D max To limit the maximum drop value, the exponential function is limited by this parameter to ensure stable operation at high power output.

[0044] The auxiliary autonomous power response controller sets the power reference value through the fourth constant module, and after the filtered active power passes through the fourth inverting adder, the signal ω is obtained through the fifth proportional link. MD , and the signal ω Δ The frequency error ω is obtained by the fifth inverting adder e , and then the third logic judgment module performs signal logic judgment. When the error meets the logic judgment condition, the output error ω is obtained.e,out After the second integral link, the frequency offset ω is obtained ps .

[0045] Index signal E i (p) and the additional amount of power exceeding the limit pass through the first positive phase adder, and then pass through the third function operation module to obtain the exponential droop control signal D exp , and then the frequency deviation ω obtained by the auxiliary autonomous power response controller ps After passing through the third inverting adder, the signal output by the fourth function operation module passes through the second positive adder, and then passes through the third positive adder with the third constant module to obtain the per-unit autonomously generated angular velocity, and then passes through the fourth proportional link to obtain the actual autonomously generated angular velocity, and finally passes through the first integral link to obtain the inverter autonomous synchronous phase δ I .

[0046] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein: the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0047] A computer-readable storage medium stores a computer program, wherein: when the computer program is executed by a processor, the steps of any one of the methods of the present invention are implemented.

[0048] Beneficial effects of the invention: Compared with the traditional linear droop control method, the exponential droop control method of the autonomous grid-connected inverter based on frequency stability provided by the invention significantly improves the frequency stability and power utilization of the system by establishing a nonlinear relationship between power output and frequency, naturally limits the power output near the maximum power output, provides higher damping capacity, and improves the frequency dynamic performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0050] Figure 1 An overall flow chart of an exponential droop control method for an autonomous grid-connected inverter based on frequency stabilization provided by the first embodiment of the present invention;

[0051] Figure 2 This is a principle block diagram of a phase generation module in an exponential droop control method for an autonomous grid-connected inverter based on frequency stabilization provided in a second embodiment of the present invention.

[0052] Figure 3 A block diagram of an amplitude generation module in an exponential droop control method for an autonomous grid-connected inverter based on frequency stabilization provided in a second embodiment of the present invention.

[0053] Figure 4 A block diagram of a pulse modulation module in an exponential droop control method for an autonomous grid-connected inverter based on frequency stability provided in a second embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0055] Example 1, reference Figure 1 , is an embodiment of the present invention, and provides an exponential droop control method for an autonomous grid-connected inverter based on frequency stability, comprising:

[0056] S1: Get the input electrical signal required by the inverter.

[0057] Furthermore, the electrical signal includes the voltage and current of the grid connection point.

[0058] S2: Generate inverter synchronization phase through exponential droop controller and auxiliary autonomous power response controller.

[0059] Exponential droop controller part:

[0060] Perform logical judgment on the filtered active power p to obtain the power signal p out1 . If |p| <p max , then p out1 =p; if |p|≥p max , then p out1 =p max .

[0061] Among them, p max is the inverter output power limit.

[0062] Power signal p out1 Through absolute value inversion processing, the power output is mirror-inverted at the origin, and the exponential signal E is obtained based on the exponential function. I (p out1 ).

[0063]

[0064] Among them, α and β are exponential function parameters.

[0065] The inverter output power limit is calculated as follows: When the power does not exceed the limit, the derivative of the exponential signal EI(p) with respect to p is:

[0066]

[0067] Make the index signal E I The derivative of (p) with respect to p is equal to D max , so the power limit p max It is expressed as:

[0068]

[0069] The filtered active power p is determined by the following logic to obtain the power signal p out2 .

[0070] If |p|≥p max , then p out2 =p; if |p| <p max , then p out2 =p max The power signal p out2 With power limit p max Subtract and linearize with the linearization parameter D max Multiply them to get the additional amount D when the power exceeds the limit max (|p|-p max ), by introducing D max To limit the maximum droop value to ensure stable operation at high power output; additional amount D max (|p|-p max ) and the index signal E I (p out1 ) and then multiplied by the reflection function S(p). Finally, the exponential droop module generates a frequency signal D exp :

[0071]

[0072] Due to D exp The nonlinear droop characteristics of (p) need to be adjusted by the frequency setting value ω set (p set ) to add an additional frequency offset, considering the frequency setting value ω set At different power settings p set Calculation, if |p set |<p max , it is determined that the power limit is not exceeded, the additional amount is equal to 0, and the power signal p in the exponential signal out1 =p; if |p set |≥p max , it is judged as exceeding the power limit, and the additional amount pout2 =p max , the power signal p in the exponential signal out1 =p max ; expressed as:

[0073]

[0074] Auxiliary autonomous power response controller part:

[0075] Add a frequency offset ω after the perturbation occurs ps Respond to system frequency fluctuations. The frequency deviation of linear droop is:

[0076] ω MD =(p set -p)M D

[0077] Among them, ω MD is the frequency deviation, p set is the power setting value, M D is the linear droop parameter.

[0078] Frequency deviation signal ω MD With exponential droop signal D exp and signal frequency offset ω ps Perform the calculation and get the error ω e .

[0079] ω e =ω MD +D exp -ω ps

[0080] When the error ω e When the logical judgment conditions are met and recorded; output error ω e,out for;

[0081]

[0082] Among them, ε p and ε dp Both are disturbance tolerance parameters, Δp=pp max , represents the derivative of p with respect to time t;

[0083] When the power fluctuation meets the interference standard, the error ω e,out The frequency offset ω will be generated by an integrator with a gain of k ps ; When e When driven to 0 by the integrator, the converter will be able to achieve M D Specified power output value.

[0084] Inverter autonomous synchronization phase part:

[0085] Auxiliary autonomous power response control signal ω ps With the exponential droop control signal D exp The difference is calculated and compared with the frequency setting value ω set and nominal frequency setting value ω nom Added and then compared with the frequency reference value ω b Get the actual generation frequency ω I , and then the inverter autonomous synchronization phase δ is obtained through the integrator I The total output signal of exponential droop control is:

[0086]

[0087] S3: Generate an inverter reference amplitude by sampling the input electrical signal.

[0088] The amplitude generation module adopts voltage reactive power droop control, and collects the voltage V at the grid connection point. abc and current I abc , the instantaneous reactive output Q can be calculated e , voltage V abc The effective value calculation module RMS is used to calculate the difference between the rated phase voltage and the droop coefficient k q Multiply them together to get the voltage droop component, and the reactive output Q e With reactive reference Q ref The difference is added to the voltage droop component, and the inverter reference amplitude E is obtained after passing through the integration link.

[0089] S4: Generate an inverter pulse modulation signal according to the autonomous phase and reference amplitude generated by the control module.

[0090] The autonomous phase obtained by the phase generation module and the reference amplitude obtained by the amplitude generation module are used for space vector modulation to generate 6 pulse modulation signals S 1 -S 6 , used to control the opening and closing of the inverter switching devices.

[0091] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0092] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0093] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0094] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0095] Example 2, reference Figure 2-Figure 4 , which is an embodiment of the present invention, provides an exponential droop control method for an autonomous grid-connected inverter based on frequency stability. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0096] Figure 2 The basic block diagram of the index droop control method of the autonomous grid-connected inverter based on frequency stability of the present invention is shown, including: 1. a first inertia link; 2. a first logic judgment module; 3. a first function operation module; 4. a second logic judgment module; 5. a first proportion link; 6. a second function operation module; 7. a first constant module; 8. a first inverting adder; 9. a second inverting adder; 10. a second constant module; 11. a second proportion link; 12. a third proportion link; 13. a first positive adder; 14. a third function operation module; 15. a third inverting adder; 16. a fourth function operation module; 17. a second positive adder; 18. a third positive adder; 19. a fourth proportion link; 20. a third constant module; 21. a first integral link; 22. a fourth constant module; 23. a fourth inverting adder; 24. a fifth proportion link; 25. a fifth inverting adder; 26. a third logic judgment module; and 27. a second integral link.

[0097] Among them, p meas is the measured instantaneous power, p is the filtered active power, and p set is the external power setting value, M D is the droop gain, ω MD is the linear droop output angular velocity, D exp is the angular velocity output by the exponential droop control channel, ω ps is the deviation angular velocity output by the auxiliary autonomous power response controller, ω Δ Yes ps Right D exp The difference signal, ω set is the angular velocity setting value, which is calculated by setting different power setting values, ω nom is the nominal angular velocity setting, ωb is the reference angular velocity of the system.

[0098] Figure 3 The amplitude generation module is shown, where the input is the grid voltage V abc and rated phase voltage V n , through the voltage and reactive power droop, the inverter reference amplitude E is obtained.

[0099] Figure 4 The pulse modulation module is demonstrated. The inverter autonomous synchronization phase obtained by the phase generation module and the inverter reference amplitude E obtained by the amplitude generation module are output through the space vector modulation module S1-S6 pulse signals.

[0100] The measured instantaneous power output p meas The filtered active power p is obtained through the first inertia link, and after the limiting processing is performed by the first logic judgment module, the absolute value inversion processing is performed by the first function operation module, and then the core index signal E that can be mirror-inverted at the origin is obtained through the first proportional link, the second function operation module, the second inverting adder, the second constant module, the third proportional link and other parts. i (p).

[0101] By introducing the parameter D max The maximum drop is limited by , which limits the exponential function to ensure stable operation at high power outputs. Linearization occurs at power output p l where the drop value is equal to D max .

[0102] The filtered active power p is judged by the second logic judgment module, and then passes through the first constant module, the first inverting adder, and the second proportional link to obtain the droop expression when the power exceeds the limit. The linearization occurs at the power output p l where the drop value is equal to D max The control channel is achieved by introducing a constant D max To limit the maximum drop value, the exponential function is limited by this parameter to ensure stable operation at high power output.

[0103] Linearization is performed at the parameter limit; the filtered active power p is determined by another logic and is calculated by parameter D max The power exceeding the limit is linearized to obtain D exp (p).

[0104] The auxiliary autonomous power sharing controller adds a frequency offset ω during the stable period after the disturbance ps The droop index control cannot achieve the transient power contribution of inertia support and main frequency response cycle. The autonomous power sharing controller adds an offset component ωps To achieve fair power sharing after transient, the droop index control is based on D exp (p) provides damping for the system, while the increased offset ω ps Change l , responds to system frequency fluctuations. Ignoring the frequency setting value, the frequency deviation of linear droop is,

[0105]

[0106] This frequency is related to D exp and the current power sharing component ω ps Perform the calculation and get the error ω e ,

[0107]

[0108] When the disturbance meets the logic judgment condition and is recorded, the error is calculated by the module and the error is output. The auxiliary autonomous power sharing controller sets the power reference value through the fourth constant module, and after the filtered active power passes through the fourth inverting adder, the fifth proportional link obtains ω MD , and ω Δ The frequency error ω is obtained by the fifth inverting adder e , and then the third logic judgment module performs signal logic judgment. When the disturbance meets the logic judgment condition, the operation is performed to obtain the output error ω e,out After the second integral link, the frequency offset ω is obtained ps .

[0109] Core Index Signal E i (p) and the additional amount when the power exceeds the limit pass through the first positive phase adder, and then pass through the third function operation module to obtain the droop index control signal D exp , and then the frequency deviation ω obtained by the auxiliary autonomous power sharing controller ps After passing through the third inverting adder, the signal output by the fourth function operation module passes through the second positive adder, and then passes through the third positive adder with the third constant module to obtain the per-unit autonomously generated angular velocity, and then passes through the fourth proportional link to obtain the actual autonomously generated angular velocity, and finally passes through the first integral link to obtain the electrical angle δ I .

[0110] Embodiment 3 is an embodiment of the present invention, which provides an exponential droop control method for an autonomous grid-connected inverter based on frequency stability.

[0111] To verify the beneficial effects of the present invention, it can be verified on the IEEE 39-node test system. By comparing case (1), all the generators in the system are synchronous generators, case (2) replaces three of the synchronous generators with traditional linear droop grid-forming inverters, and case (3) replaces three of the synchronous generators with exponential droop control grid-forming inverters with the functions of the present invention. And apply a disturbance, the disturbance is to cut off one of the synchronous generators. The average frequency response of case 1 is that the lowest frequency point is 49.60Hz, the frequency change rate is 0.64Hz / s, and the damping is 0.1N·m·s; the average frequency response of case 2 is that the lowest frequency point is 49.66Hz, the frequency change rate is 0.83Hz / s, and the damping is 0.14N·m·s; the average frequency response of case 3 is that the lowest frequency point is 49.78Hz, the frequency change rate is 0.64Hz / s, and the damping is 0.15N·m·s

[0112] Case (1) is the frequency response of the power system dominated by synchronous generators. The frequency response of case (2) is improved compared with case (1), and the lowest frequency point rises to 49.66, but the frequency change rate is higher at 0.83Hz / s. In case (3), i.e. the exponential droop control proposed by the present invention, its frequency response is the best among the three cases, and its lowest frequency point is 49.78Hz, which is improved compared with cases (1) and (2). At the moment of disturbance, the grid-forming device using exponential droop control can provide more power output for the system and slow down the frequency drop faster than the traditional linear droop control.

[0113] 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 preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An exponential droop control method for autonomous grid-connected inverters based on frequency stability, characterized in that: include: Obtain the input electrical signal required by the inverter; Generates inverter autonomous synchronization phase through exponential droop controller and auxiliary autonomous power response controller; generating a reference amplitude of the inverter by sampling the input electrical signal; A pulse modulation signal for the inverter is generated according to the phase and reference amplitude generated by the control module.

2. The method for controlling exponential droop of an autonomous grid-connected inverter based on frequency stabilization according to claim 1, characterized in that: The electrical signal includes the voltage and current of the grid connection point.

3. The method for controlling exponential droop of an autonomous grid-connected inverter based on frequency stabilization according to claim 2, characterized in that: The exponential droop controller is used to generate the inverter autonomous synchronization phase, including performing a logical judgment on the filtered active power p to obtain a power signal p out1 ; If |p| <p max , then p out1 =p; if |p|≥p max , then p out1 =p max ; Among them, p max is the inverter output power limit; Power signal p out1 Through absolute value inversion processing, the power output is mirror-inverted at the origin, and the exponential signal E is obtained based on the exponential function. I (p out1 ); Among them, α and β are exponential function parameters.

4. The method for controlling exponential droop of an autonomous grid-connected inverter based on frequency stabilization according to claim 3, characterized in that: The inverter output power limit includes that when the power does not exceed the limit, the derivative of the exponential signal EI(p) with respect to p is: Make the index signal E I The derivative of (p) with respect to p is equal to D max , so the power limit p max It is expressed as; 5. The method for controlling exponential droop of an autonomous grid-connected inverter based on frequency stabilization according to claim 4, characterized in that: The exponential droop controller generates the inverter autonomous synchronization phase, including an additional power over-limit linearization processing module, through a logical judgment of the filtered active power p, to a power signal p out2 ; If |p|≥p max , then p out2 =p; if |p| <p max , then p out2 =p max ; The obtained power signal p out2 With power limit p max Subtract and linearize the parameter D max Multiply them to get the additional amount D when the power exceeds the limit max (|p|-p max ), by introducing D max To limit the maximum droop value to ensure stable operation at high power output; additional amount D max (|p|-p max ) and the index signal E I (p out1 ) and then multiplied by the reflection function S(p); Finally, the exponential droop module generates a frequency signal D exp ; Due to D exp The nonlinear droop characteristics of (p) need to be adjusted by the frequency setting value ω set (p set ) to add an additional frequency offset, considering the frequency setting value ω set At different power settings p set Calculation, if |p set |<p max , it is determined that the power limit is not exceeded, the additional amount is equal to 0, and the power signal p in the exponential signal out1 =p; if |p set |≥p max , it is judged as exceeding the power limit, and the additional amount p out2 =p max , the power signal p in the exponential signal out1 =p max ; expressed as:

6. The method for controlling exponential droop of an autonomous grid-connected inverter based on frequency stabilization according to claim 5, characterized in that: The auxiliary autonomous power response controller includes adding a frequency offset ω after a disturbance occurs. ps Respond to system frequency fluctuations; The frequency deviation of linear droop is; ω MD =(p set -p)M D Among them, ω MD is the frequency deviation, p set is the power setting value, M D is the linear droop parameter; Frequency deviation signal ω MD With exponential droop signal D exp and signal frequency offset ω ps Perform the calculation and get the error ω e ; oh e =ω MD +D exp -oh ps When the error ω e When the logical judgment conditions are met and recorded; output error ω e,out for; Among them, ε p and ε dp Both are disturbance tolerance parameters, Δp=pp max , represents the derivative of p with respect to time t; When the power fluctuation meets the interference standard, the error ω e,out The frequency offset ω will be generated by an integrator with a gain of k ps ; When e When driven to 0 by the integrator, the converter will be able to achieve M D Specified power output value.

7. The method for controlling exponential droop of an autonomous grid-connected inverter based on frequency stabilization according to claim 6, characterized in that: The inverter pulse modulation signal includes an auxiliary autonomous power response control signal ω ps With the exponential droop control signal D exp The difference is calculated and compared with the frequency setting value ω set and nominal frequency setting value ω nom Added and then compared with the frequency reference value ω b Get the actual generation frequency ω I , and then the inverter autonomous synchronization phase δ is obtained through the integrator I ; The total output signal of exponential droop control is:

8. An exponential droop control system for an autonomous grid-connected inverter based on frequency stabilization using the method according to any one of claims 1 to 7, characterized in that: It includes:

1. a first inertia link; 2. a first logic judgment module; 3. a first function operation module; 4. a second logic judgment module; 5. a first proportion link; 6. a second function operation module; 7. a first constant module; 8. a first inverting adder; 9. a second inverting adder; 10. Second constant module; 11. Second proportional link; 12. Third proportional link; 13. First positive phase adder; 14. Third function operation module; 15. Third negative phase adder; 16. Fourth function operation module; 17. Second positive phase adder; 18. Third positive phase adder; 19. Fourth proportional link; 20. Third constant module; 21. First integral link; 22. Fourth constant module; 23. The fourth inverting adder; 24. The fifth proportional link; 25. The fifth inverting adder; 26. The third logic judgment module; 27. Second points round; The measured instantaneous power output p meas The filtered active power p is obtained through the first inertia link, and after the limiting processing is performed by the first logic judgment module, the absolute value inversion processing is performed, and then the exponential signal E is obtained through the first proportional link, the second function operation module, the second inverting adder, the second constant module and the third proportional link. i (p out1 ); The filtered active power p is judged by the second logic judgment module, and then combined with the first constant module through the first inverting adder and the second proportional link to obtain the additional amount when the power exceeds the limit. The linearization occurs at the power limit p max where the droop value is equal to D max The control channel is achieved by introducing a constant D max To limit the maximum drop value, the exponential function is limited by this parameter to ensure stable operation under high power output; The auxiliary autonomous power response controller sets the power reference value through the fourth constant module, and after the filtered active power passes through the fourth inverting adder, the signal ω is obtained through the fifth proportional link. MD , and the signal ω Δ The frequency error ω is obtained by the fifth inverting adder e , and then the third logic judgment module performs signal logic judgment. When the error meets the logic judgment condition, the output error ω is obtained. e,out After the second integral link, the frequency offset ω is obtained ps ; Index signal E i (p) and the additional amount of power exceeding the limit pass through the first positive phase adder, and then pass through the third function operation module to obtain the exponential droop control signal D exp , and then the frequency deviation ω obtained by the auxiliary autonomous power response controller ps After passing through the third inverting adder, the signal output by the fourth function operation module passes through the second positive adder, and then passes through the third positive adder with the third constant module to obtain the per-unit autonomously generated angular velocity, and then passes through the fourth proportional link to obtain the actual autonomously generated angular velocity, and finally passes through the first integral link to obtain the inverter autonomous synchronous phase δ I .

9. A computer device comprising: Memory and processor; The memory stores a computer program, characterized in that: when the processor executes the computer program, the steps of the exponential droop control method of the autonomous grid-connected inverter based on frequency stability are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for exponential droop control of an autonomous grid-connected inverter based on frequency stabilization are implemented.

Images