Network-constructing and network-following type inverter hybrid grid-connected power oscillation suppression method and system

Abstract

The application discloses a network-constructing and network-following type inverter hybrid grid-connected power oscillation suppression method and system. The network-following type inverter is controlled by a current control type virtual synchronous generator, and the network-constructing type inverter is controlled by a voltage control type virtual synchronous generator and double mutual damping control combining frequency mutual damping and power mutual damping, so as to offset the interaction of the network-following type inverter on the network-constructing type inverter and control the network-constructing type inverter grid-connected power. The method can simultaneously suppress the power oscillation of the network-constructing and network-following type inverter hybrid grid-connected system under weak power grid and strong power grid, reduce the grid-connected point voltage and current harmonics, and improve the power quality.

Description

Technical Field

[0001] This invention relates to the field of power oscillation suppression in hybrid grid-connected inverters that combine grid-connected and grid-following inverters, and in particular to a method and system for suppressing power oscillations in hybrid grid-connected inverters that combine grid-connected and grid-following inverters. Background Technology

[0002] In recent years, the rapid development of renewable energy and power electronic conversion technologies has led to a significant increase in the penetration rate of grid-connected inverters in power systems. Grid-connected inverters can be divided into grid-connected inverters and grid-connected inverters. Compared with traditional grid-connected inverters, grid-connected inverters have stronger stability under weak grid conditions and can actively support the voltage and frequency of the grid. Therefore, traditional grid-connected systems dominated by grid-connected inverters are gradually shifting to hybrid grid-connected systems using both grid-connected and grid-connected inverters.

[0003] Although grid-connected inverters possess grid support capabilities similar to synchronous generators, they also introduce the risk of power oscillations. When grid-connected and grid-connected inverters operate in parallel, their differing control methods can lead to more complex interactions and couplings, further exacerbating the power oscillation problem. Therefore, studying the power oscillation mechanism in hybrid grid-connected and grid-connected inverter systems and proposing corresponding strategies to suppress interactive effects and power oscillations are critical technical issues that urgently need to be addressed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for suppressing power oscillations in hybrid grid-connected inverters that combine grid-connected and grid-following inverters, thereby suppressing power oscillations in hybrid grid-connected systems under both weak and strong grid conditions, in order to address the shortcomings of existing technologies.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for suppressing grid-connected power oscillations of hybrid grid-connected inverters, comprising the following steps:

[0006] Construct the following interactive pass function: Where, ΔP e1 For the small-signal value of active power output by the grid-connected inverter, ΔP n1 and ΔP n2 The small-signal disturbances to the reference power of grid-connected and grid-followed inverters are Δω, respectively. g For small-signal disturbances at the power grid frequency, Y P1h =-H w1 Y b1 / (Y a1h +Y b1 ), Y P2 =Y a2 Y b2 / (Y a2 +Y b2), Y g =K g / s, Y a1h =ω n J1s+ω n D p1 +K w1 +ω n K h1 Y b1 =K1 / s, Y a2 =D p2 +J2s, Y b2 =3(V buso ) 2 / (2X t2 ·s), K g =3V g V buso / (2X g K1 = 3V 1o V buso / (2X t1 ), φ 1h =Y b1 / (Y a1h +Y b1 ), φ 2h =H p1 Y b1 / (Y a1h +Y b1 ), φ2=Y b2 / (Y a2 +Y b2 ), H p1 =-ω n K h2 +ω n K h2 φ2+ω n K h1 φ 2w H w1 =-ω n K h2 Y p2 +ω n K h1 Y p2w -Y a1h ω n J1 and D represent the angular frequency reference values ​​for grid-connected inverters. p1 K w1 These are the inertia coefficient, damping coefficient, and primary frequency regulation coefficient of the grid-connected inverter, J2 and D. p2 These are the inertia coefficient and damping coefficient of the grid-connected inverter, V. 1o V g V buso These represent the steady-state voltage values ​​of the grid-connected inverter, the power grid, and the PCC, respectively.t1 X t2 X g These represent the line impedance of the grid-connected inverter, the line impedance of the grid-connected inverter, and the grid impedance, respectively. K h1 and K h2 These are the frequency mutual damping coefficient and the power mutual damping coefficient, respectively, and s is a complex variable;

[0007] Based on the aforementioned interactive transfer function, the critical mutual damping coefficient K is obtained. h1 and K h2 Changes in the root locus of the interaction transfer function and the step response during the change;

[0008] Based on K h1 and K h2 The change in ΔP e1 The principle of the root locus being furthest from the imaginary axis and ΔP e1 The key cross-damping coefficient K is obtained by minimizing the oscillations in the step response. h1 and K h2 .

[0009] In this invention, K h1 ∈[120,140], K h2 ∈[0.005,0.02].

[0010] As an inventive concept, the present invention also provides a hybrid grid-connected power oscillation suppression system for grid-connected and grid-linked inverters, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0011] As an inventive concept, the present invention also provides a computer-readable storage medium having a computer program / instructions stored thereon; when the computer program / instructions are executed by a processor, they implement the steps of the above-described method.

[0012] As an inventive concept, the present invention also provides a computer program product, including a computer program / instructions; when the computer program / instructions are executed by a processor, they implement the steps of the above-described method.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows: The power oscillation suppression method for hybrid grid-connected inverters based on dual mutual damping control provided by this invention involves the grid-connected inverter controlling its grid-connected power through a current-controlled virtual synchronous generator, while the grid-connected inverter controls its grid-connected power through a voltage-controlled virtual synchronous generator and dual mutual damping control combining frequency and power mutual damping. This counteracts the interactive influence of the grid-connected inverter on the grid-connected inverter, thereby controlling the grid-connected power of the grid-connected inverter. This method can simultaneously suppress power oscillations in hybrid grid-connected inverter systems under both weak and strong grid conditions, reduce voltage and current harmonics at the grid connection point, and improve power quality. Attached Figure Description

[0014] Figure 1 The flowchart below shows the method and system for suppressing grid-connected power oscillations of hybrid grid-connected inverters based on dual mutual damping control, as described in this embodiment of the invention.

[0015] Figure 2 This is a main circuit diagram of the grid-connected power suppression method and system based on dual mutual damping control for grid-connected and grid-following inverters, as described in an embodiment of the present invention.

[0016] Figure 3 This is a control block diagram of the power oscillation suppression method and system for hybrid grid-connected inverters based on dual mutual damping control according to an embodiment of the present invention.

[0017] Figure 4 This is a root locus diagram showing the power oscillation suppression method for hybrid grid-connected inverters based on dual mutual damping control in an embodiment of the present invention, and the changes in key system parameters; (a) shows K h1 (a) shows the root locus changes when J1 changes; (b) shows the changes when K changes. h2 The root locus changes when J1 changes;

[0018] Figure 5 The diagram shows the step response variation of the hybrid grid-connected power oscillation suppression method based on dual mutual damping control of grid-connected and grid-following inverters in this invention, as well as the variation of key system parameters; (a) shows K h1 (b) shows the step response variation under varying conditions; K is... h2 A graph showing the change in step response under varying conditions;

[0019] Figure 6 The following diagrams illustrate the active power response of the hybrid grid-connected system under strong grid conditions using different control methods according to an embodiment of the present invention: (a) Active power response of the grid-connected inverter under strong grid conditions using different control methods according to an embodiment of the present invention; (b) Active power response of the grid-connected inverter under strong grid conditions using different control methods according to an embodiment of the present invention.

[0020] Figure 7 (a) is the active power response diagram of the hybrid grid-connected system of the present invention under different control methods under weak grid conditions; (b) is the active power response diagram of the grid-type inverter of the hybrid grid-connected system of the present invention under different control methods under weak grid conditions. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] Embodiment 1 of this invention provides a method for suppressing grid-connected power oscillations in hybrid grid-connected inverters based on dual mutual damping control, such as... Figure 1 As shown, the method includes:

[0024] S1: Obtain voltage data for the grid-connected inverter and voltage and power data for the network-connected inverter.

[0025] The system samples voltage data from both grid-connected and grid-connected inverters, as well as voltage and power data from grid-connected inverters. It can monitor the voltage, current, voltage, active power, and reactive power data of grid-connected and grid-connected inverters in real time to assess the system's operating status and performance. It provides baseline data for current, voltage, active power, and reactive power during normal system operation.

[0026] S2: The grid-connected inverter controls the grid-connected power through phase-locked loop control of voltage data input and current control type virtual synchronous generator control.

[0027] It should be noted that, Figure 2 The diagram shows the main circuit structure of a hybrid grid-connected power suppression method and system based on dual-mutual damping control for grid-connected and grid-linked inverters. This hybrid grid-connected system consists of grid-connected and grid-linked inverters connected in parallel. Typically, the grid-connected inverter is represented as an ideal voltage source, and the grid-linked inverter as an ideal current source. The grid-connected and grid-linked inverters are connected through the line impedance Z. t1 and Z t2Connect to the point-of-common-coupling (PCC). g V represents the mains impedance. g =V g ∠δ g V bus =V bus ∠δ bus V1 = V1∠δ1 and V2 = V2∠δ2 represent the grid voltage vector, PCC voltage vector, grid-connected inverter output voltage vector, and grid-connected inverter output voltage vector, respectively. Figure 3 The diagram shows the control block diagram of a hybrid grid-connected power oscillation suppression method and system based on dual mutual damping control for grid-connected and grid-linked inverters. The grid-connected inverter uses a voltage-controlled virtual synchronization generation (VVSG), while the grid-linked inverter uses a current-controlled virtual synchronization generation (CVSG).

[0028] The control section of a grid-connected inverter mainly includes an active power control outer loop, a reactive power control outer loop, a phase-locked loop (PLL), a current control inner loop, and a PWM generation stage. The active power control outer loop of a grid-connected inverter consists of an active power reference value and a primary frequency regulation control loop. The reactive power control outer loop is calculated by dividing the actual reactive power value by 1.5e. 2q The q-axis current reference value is obtained, and the phase-locked loop (PLL) uses PI control. The active power control loop and PLL principles of the grid-connected inverter are as follows:

[0029]

[0030] Where ω2,P e2 ,v 2q θ2 and θ2 represent the phase-locked loop angular frequency, active power, q-axis voltage, and phase of the grid-connected inverter output, respectively, while P n2 Indicates the reference active power. J2 and D p2 These correspond to the inertia coefficient and damping coefficient of active power control, respectively, and J2=ω n J′2,D p2 =ω n D′ p2 +K′ w2 Among them, J′2 and D′ p2 and K′ w2 K is consistent with the inertia parameters, damping coefficient, and primary frequency regulation coefficient of the grid-type inverter. f2 This represents the differential filter coefficients. Furthermore, G...pll2 (s) represents the PI controller of the phase-locked loop, and its expression is G. pll2 (s)=(K p_pll2 +K i_pll2 ) / s, where K p_pll2 and K i_pll2 These represent the proportional coefficient and the integral coefficient, respectively.

[0031] Based on the active power control loop principle of grid-connected inverters, the small-signal value of the output angular frequency Δω2 of the grid-connected inverter and the small-signal value of the output active power ΔP of the grid-connected inverter are related. e2 The relationship can be derived as follows:

[0032]

[0033] Among them, the small-signal value ΔP of the active power output of the grid-connected inverter. e2 It is proportional to the small-signal value ΔI2 of the grid-connected inverter output current:

[0034]

[0035] Based on the main circuit equations of a grid-connected inverter in the dq coordinate system of a phase-locked loop, the relationship between the small-signal value of the output current ΔI2 and the small-signal value of the angular frequency Δω2 of the grid-connected inverter can be expressed as:

[0036]

[0037] In summary, considering the above ΔP e2 The relationship between ΔI2 and ΔI2 and Δω2 is related to the small-signal value ΔP of the output power of the grid inverter. e2 The small signal value of its own angular frequency Δω2 and the small signal value of the angular frequency at the PCC point Δω can be used. bus Represented as:

[0038] ΔP e2 =(Y b2 +Y c2 )Δω2-Y b2 Δω bus ;

[0039] in:

[0040]

[0041] Therefore, Δω2 and ΔP e2 Relationship and ΔP e2 With Δω2, Δω bus The relational equations are combined with the small-signal value ΔP of the grid inverter output power. e2 Small signal value Δω at PCC point angular frequency bus The relation is:

[0042]

[0043] S3: The grid-connected inverter uses voltage-controlled virtual synchronous generators and dual-interlocking control based on voltage and power data inputs to offset the interactive effects of the grid-connected inverter on the grid-connected inverter, thereby controlling the grid-connected power of the grid-connected inverter.

[0044] As discussed above, the control algorithm for the grid-connected inverter employs a voltage-controlled virtual synchronous generator (VSR) with the addition of dual-mutual damping control. The voltage-controlled VSR mainly comprises an active power control outer loop, a reactive power control outer loop, a voltage control inner loop, a current control inner loop, and a PWM generation stage. The dual-mutual damping control includes frequency mutual damping and power mutual damping terms. These two mutual damping terms are fed back to the active power control outer loop of the grid-connected inverter to suppress the interactive effects of the grid-connected inverter on the grid-connected inverter.

[0045] The active power control outer loop of the grid-type inverter consists of an active power reference value and a primary frequency regulation control loop, while the reactive power control outer loop consists of a reactive power reference value and a primary voltage regulation control loop. The active power loop outputs a phase angle θ1, and the reactive power loop outputs a voltage amplitude V1. The two together control the grid-type output voltage value.

[0046] Before the introduction of dual mutual damping control, the active power control loop and reactive power control loop principles of the grid-connected inverter were as follows:

[0047] P e1 =(ω n -ω1)(ω n J1s+ω n D p1 +K ω1 )+P n1 ;

[0048]

[0049] Where ω1, V1, P e1 and Q e1 These represent the angular frequency, voltage, active power, and reactive power output of the grid-connected inverter, respectively. n V n1 P n1 and Q n1 This represents the corresponding reference value. K ω1 It is the frequency adjustment coefficient. D p1 and D q1 J1 and J2 represent the damping coefficient and voltage droop coefficient, respectively. v1 These are the inertia coefficients for the active power control outer loop and the reactive power control outer loop, respectively.

[0050] After introducing angular frequency cross-damping and power cross-damping, the active power loop of the grid-connected inverter can be expressed as:

[0051]

[0052] Therefore, the small-signal value of the output angular frequency Δω1 of the grid-connected inverter and the small-signal value of the output active power ΔP of the grid-connected inverter are related. e1 The relationship can be derived as follows:

[0053]

[0054] To simplify the interaction analysis of hybrid systems, the line resistance R is ignored. t1 and R t2 In this case, the small-signal value ΔP of the grid-connected inverter's output power e1 The small signal value of its own angular frequency Δω1 and the small signal value of the angular frequency at the PCC point Δω can be used. bus Represented as:

[0055]

[0056] in:

[0057]

[0058] Therefore, Δω1 and ΔP e1 Relationship and ΔP e1 With Δω1, Δω bus Relationship equations, small-signal value ΔP of grid-connected inverter output power. e1 Small signal value Δω at PCC point angular frequency bus The relation is:

[0059]

[0060] in:

[0061]

[0062] In order to obtain the small signal value Δω of the PCC point angular frequency bus It is necessary to know the power ΔP at PCC. bus With the angular frequency Δω of the power grid bus The relationship between them can be represented as:

[0063] ΔP bus =Y g (Δω bus -Δω g );

[0064] in:

[0065]

[0066] According to the principle of conservation of energy, ΔP bus It can be represented as:

[0067] ΔP e1 +ΔP e2 =ΔP bus ;

[0068] ΔP e1 With Δω bus Relationship, ΔP e2 With Δω bus Relationship and ΔP bus With Δω bus Substituting the relation into the above equation, we can obtain the angular frequency value Δω at PCC. bus :

[0069]

[0070] Δω bus Substitute the value into ΔP e1 With Δω bus The relationship can be used to obtain the output active power value ΔP of the grid-type inverter. e1 :

[0071]

[0072] From the above formula, it can be seen that the output power ΔP of the grid-connected inverter is... e1 Not only is it related to its own active power reference value ΔP n1 It is also related to the active power reference value ΔP of the grid-connected inverter. n2 This is relevant. Therefore, in order to offset the interaction between the active power of the grid inverter and the grid inverter, the ΔP must be satisfied. n2 The numerator of the coefficient is 0.

[0073] S4: Design key control parameters for dual mutual damping control based on root locus graph (Hu Shousong. Automatic Control Principles. Beijing. Science Press. 6th Edition, 2013. 137-150) and step response graph (Hu Shousong. Automatic Control Principles. Beijing. Science Press. 6th Edition, 2013. 66-69).

[0074] When a hybrid system employs a dual-mutual-damping control method combining angular frequency mutual damping and power mutual damping, the grid-connected inverter outputs active power ΔP. e1 The active power reference value ΔP of the grid-connected inverter n2 The interaction transfer function is given above. Based on the interaction transfer function, we can obtain the key parameter K. h1 and K h2 The change in the root locus of the interaction transfer function during change. To rationally design K...h1 and K h2 The value, Figure 4 This demonstrates that under a strong power grid with a short-circuit ratio of 7.7, when J1 varies within the range of [1, 8], K... h1 and K h2 The effect on the dominant pole. When K h1 As K increases from 50 to 140, the dominant pole moves away from the imaginary axis, reducing the amplitude of power oscillations. However, if K... h1 As the power increases further, the dominant pole will move away from the real axis and closer to the imaginary axis, indicating that power oscillations are intensifying. Figure 4 In (b), it can be observed that when K h2 When K = 0.06, pole s1 is far from the imaginary axis, while s2 is close to the imaginary axis. As K... h2 Increasing K to 0.02 moves s2 away from the imaginary axis and makes it symmetrical about the real axis with respect to s1, thus reducing the oscillation. However, if K h2 As the number of s1 and s2 increases further, they will both approach the imaginary axis, leading to intensified oscillations. Based on this analysis, this embodiment of the invention selects K under a strong power grid with a short-circuit ratio of 7.7. h1 =140 and K h2 =0.02. Similarly, based on the root locus method, it can be obtained that K is taken in the weak power grid with a short-circuit ratio of 2.3 in the embodiment of the present invention. h1 =120 and K h2 The oscillation suppression effect is best when the value is 0.005.

[0075] Based on the active power output ΔP of the grid-type inverter e1 The active power reference value ΔP of the grid-connected inverter n2 The interactive transfer function can be obtained when ΔP n2 When a step change occurs, ΔP e1 The response. Figure 5 The system exhibits the mutual damping coefficient K at different angular frequencies under a strong power grid with a short-circuit ratio of 7.7. h1 and power mutual damping coefficient K h2 The step response of the interaction. Figure 5 (a) shows that when K h1 If K is too small, it will lead to a large drop and a long stabilization time; while when K is too small... h1 When K is too large, it will lead to significant overshoot and increase the settling time. h1 When K changes from 0.01 to 300, set K. h1 When the value is 140, the settling time is the shortest and there is no overshoot. Figure 5 (b) shows that when K h2 When K is too small, it leads to significant overshoot and a long settling time; while when K is too small... h2When K is too large, it can lead to a significant drop and a longer stabilization time, and may even cause system instability. In summary, when K... h1 =140 and K h2 When the ratio is 0.02, the embodiment of the present invention exhibits the shortest stabilization time and no overshoot under a strong power grid with a short-circuit ratio of 7.7. This verifies the effectiveness of the method based on... Figure 3 The parameter design is reasonable. Similarly, based on the step response method, it can be obtained that K is taken in this embodiment of the invention under a weak power grid with a short-circuit ratio of 2.3. h1 =120 and K h2 When K = 0.005, the settling time is shortest and there is no overshoot. In summary, to simultaneously suppress power oscillations in hybrid grid-connected systems with both weak and strong grids, K... h1 ∈[120,140], K h2 ∈[0.005,0.02].

[0076] The power oscillation suppression method for hybrid grid-connected inverters based on dual mutual damping control in this invention can simultaneously suppress power oscillations in grid-connected systems under both strong and weak grid conditions. Figure 6 This demonstrates the active power response of grid-connected and grid-attached inverters under strong grid conditions, using different control algorithms. Under conventional control, as shown by the black line, when P... n1 When P changes e1 and P e2 Overshoots of 4.95% and 1.58% occurred, with durations of 0.9 seconds and 0.6 seconds, respectively. When the active power reference value P... n2 When a step signal is applied, P e1 and P e2 Oscillations also occurred, with amplitudes of 3.7% and 1.3%, and durations of 0.9 seconds and 0.6 seconds, respectively.

[0077] Under strong grid conditions, when frequency transdamping control is applied only to grid-connected inverters, Figure 6 The active power is represented by a red line. When P n1 or P n2 When a step change occurs, P e1 and P e2 All stabilized rapidly within 0.3 seconds. However, when P n2 When a step change occurs, P e1 An overshoot of 6.15% was observed. Therefore, angular frequency transdamping effectively suppressed active power oscillations, but a certain degree of overshoot still exists in grid-connected inverters.

[0078] Under strong grid conditions, when power transdamping control is applied only to grid-connected inverters, P e1 and P e2 For Pn1 The response to a step change is similar to that of angular frequency transdamping. However, when P n2 When a step jump occurs, due to the interaction effect, P e1 It dropped sharply by 10.45%, while P e2 It then exhibits slight oscillations. Figure 6 The purple line in the figure represents the active power using the dual-damping control method. e1 and P e2 For P n1 The response to a step change is similar to that of angular frequency cross-damping and power cross-damping methods. However, when P n2 When a step jump occurs, P e1 There was no overshoot, only a slight decrease of about 4.7%, and it quickly returned to a stable state.

[0079] For weak network conditions, such as Figure 7 As shown, compared with traditional control, the angular frequency mutual damping, power mutual damping, and dual mutual damping methods all effectively suppress P e1 and P e2 Power oscillations are suppressed. The dual-mutual-damping control method achieves optimal power oscillation suppression performance. In summary, the control strategy of this invention effectively suppresses power oscillations in hybrid grid-connected systems under both strong and weak power grids.

[0080] On the other hand, this embodiment also provides a power oscillation suppression system for a hybrid grid-connected system of grid-connected and grid-following inverters based on dual mutual damping control, which includes:

[0081] The data acquisition module acquires voltage data from the grid-connected inverter and voltage and power data from the grid-connected inverter.

[0082] The feedback control module controls the grid-connected power of the grid-connected inverter through phase-locked loop control based on voltage data input and current-controlled virtual synchronous generator control. The grid-connected inverter controls the grid-connected power of the grid-connected inverter through voltage-controlled virtual synchronous generator control based on voltage and power data input and dual mutual damping control, thus offsetting the interactive influence of the grid-connected inverter on the grid-connected inverter.

[0083] If the above functions are implemented as 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 this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0084] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0085] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0086] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0087] Example 2

[0088] Embodiment 2 of the present invention provides a terminal device corresponding to Embodiment 1 above. The terminal device can be a processing device for a client, such as a mobile phone, a laptop, a tablet computer, a desktop computer, etc., to execute the method of the above embodiments.

[0089] The terminal device in this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in Embodiment 1 described above.

[0090] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0091] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0092] Example 3

[0093] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to Embodiment 1 above, on which a computer program / instructions are stored. When the computer program / instructions are executed by a processor, they implement the steps of the method of Embodiment 1 above.

[0094] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0095] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0096] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0097] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0098] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0099] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for suppressing grid-connected power oscillations in hybrid grid-connected inverters that combine grid-connected and grid-following inverters, characterized in that, Includes the following steps: Construct the following interactive pass function: Where, ΔP e1 For the small-signal value of active power output by the grid-connected inverter, ΔP n1 and ΔP n2 The small-signal disturbances to the reference power of grid-connected and grid-followed inverters are Δω, respectively. g For small-signal disturbances at the power grid frequency, Y P1h =-H w1 Y b1 / (Y a1h +Y b1 ), Y P2 =Y a2 Y b2 / (Y a2 +Y b2 ), Y g =K g / s, Y a1h =ω n J1s+ω n D p1 +K w1 +ω n K h1 Y b1 =K1 / s, Y a2 =D p2 +J2s, Y b2 =3(V buso ) 2 / (2X t2 ·s), K g =3V g V buso / (2X g K1 = 3V 1o V buso / (2X t1 ), φ 1h =Y b1 / (Y a1h +Y b1 ), φ 2h =H p1 Y b1 / (Y a1h +Y b1 ), φ2=Y b2 / (Y a2 +Y b2 ), H p1 =-ω n K h2 +ω n K h2 φ2+ω n K h1 φ 2w H w1 =-ω n K h2 Y p2 +ω n K h1 Y p2w -Y a1h ω n J1 and D represent the angular frequency reference values ​​for grid-connected inverters. p1 K w1 These are the inertia coefficient, damping coefficient, and primary frequency regulation coefficient of the grid-connected inverter, J2 and D. p2 These are the inertia coefficient and damping coefficient of the grid-connected inverter, V. 1o V g V buso These represent the steady-state voltage values ​​of the grid-connected inverter, the power grid, and the PCC, respectively. t1 X t2 X g These represent the line impedance of the grid-connected inverter, the line impedance of the grid-connected inverter, and the grid impedance, respectively. K h1 and K h2 These are the frequency mutual damping coefficient and the power mutual damping coefficient, respectively, and s is a complex variable; Based on the aforementioned interactive transfer function, the critical mutual damping coefficient K is obtained. h1 and K h2 Changes in the root locus of the interaction transfer function and the step response during the change; Based on K h1 and K h2 The change in ΔP e1 The principle of the root locus being furthest from the imaginary axis and ΔP e1 The key cross-damping coefficient K is obtained by minimizing the oscillations in the step response. h1 and K h2 .

2. The method for suppressing grid-connected power oscillations of hybrid grid-connected inverters according to claim 1, characterized in that, K h1 ∈[120,140],K h2 ∈[0.005,0.02]。 3. A hybrid grid-connected power oscillation suppression system for grid-connected and grid-following inverters, comprising a memory, a processor, and a computer program stored in the memory; characterized in that, The processor executes the computer program to implement the steps of the method described in claim 1 or 2.

4. A computer-readable storage medium having a computer program / instructions stored thereon; characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method described in claim 1 or 2.

5. A computer program product, comprising a computer program / instructions; characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method described in claim 1 or 2 above.

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