Method and system for suppressing hybrid grid-connected power oscillation of grid-forming and grid-following inverters

Abstract

The invention discloses a hybrid grid-connected power oscillation suppression method and system for a grid-forming inverter and a grid-following inverter, and the grid-following inverter controls the grid-connected power of the grid-following inverter through a current control type virtual synchronous generator. And the grid-building type inverter counteracts the interaction influence of the grid-building type inverter on the grid-building type inverter through the voltage control type virtual synchronous generator and double mutual damping control combining frequency mutual damping and power mutual damping, and the grid-connected power of the grid-building type inverter is controlled. According to the method, the power oscillation of the grid-forming and grid-following type inverter hybrid grid-connected system under the weak power grid and the strong power grid can be inhibited at the same time, the voltage and current harmonic waves of the grid-connected point are reduced, and the electric energy quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of power oscillation suppression of a hybrid grid-connected inverter of a grid-building and grid-following type, and in particular to a method and system for suppressing power oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type. Background Art

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

[0003] Although grid-connected inverters have similar grid support capabilities as synchronous generators, they also bring the risk of power oscillation. When grid-connected inverters and grid-following inverters are operated in parallel, the difference in their control methods will cause more complex interaction and coupling between the two, further exacerbating the power oscillation problem. Therefore, it is a key technical issue that needs to be solved urgently to study the power oscillation mechanism in the hybrid grid-connected system of grid-connected and grid-following inverters and propose corresponding strategies to suppress interaction and power oscillation. 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 oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type, in view of the deficiencies in the prior art, so as to suppress power oscillation of the hybrid grid-connected system under weak and strong grids.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for suppressing power oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type, comprising the following steps:

[0006] Construct the following interaction transfer function: Among them, ΔP e1 is the small signal value of active power output by the grid-connected inverter, ΔP n1 and ΔP n2 are the reference power small signal disturbances of the grid-building and grid-following inverters, Δω g is the small signal disturbance of 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 Indicates the angular frequency reference value of the grid-connected inverter, J1, D p1 , K w1 are the inertia coefficient, damping coefficient and primary frequency modulation coefficient of the grid-connected inverter, J2, D p2 are the inertia coefficient and damping coefficient of the grid-following inverter, V 1o 、V g 、V buso are the steady-state voltage values ​​of the grid-connected inverter, grid, and PCC, respectively.t1 , X t2 , X g are the line impedance of the grid-building inverter, the line impedance of the grid-following inverter and the grid impedance, K h1 and K h2 are the frequency mutual damping coefficient and the power mutual damping coefficient respectively, and s is a complex variable;

[0007] Based on the interaction transfer function, the key mutual damping coefficient K is obtained. h1 and K h2 Changes in the root locus and step response of the interaction transfer function when changing;

[0008] Based on K h1 and K h2 When the ΔP changes e1 The principle that the root locus is farthest from the imaginary axis and ΔP e1 The key mutual damping coefficient K is obtained by the principle of minimum step response oscillation h1 and K h2 .

[0009] In the present 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 of grid-building and grid-following 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 / instruction stored thereon; the computer program / instruction implements the steps of the above method when executed by a processor.

[0012] As an inventive concept, the present invention also provides a computer program product, including a computer program / instruction; when the computer program / instruction is executed by a processor, the steps of the above method are implemented.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for suppressing power oscillation of a hybrid grid-connected system of grid-building and grid-following inverters based on dual mutual damping control, the grid-following inverter controls the grid-connected power of the grid-following inverter through a current-controlled virtual synchronous generator, and the grid-building inverter offsets the interactive influence of the grid-following inverter on the grid-building inverter through a voltage-controlled virtual synchronous generator and dual mutual damping control combining frequency mutual damping and power mutual damping, thereby controlling the grid-connected power of the grid-building inverter. The method of the present invention can simultaneously suppress the power oscillation of a hybrid grid-connected system of grid-building and grid-following inverters under weak and strong power grids, reduce the voltage and current harmonics at the grid connection point, and improve the quality of electric energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of a method and system for suppressing power oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type based on dual mutual damping control according to an embodiment of the present invention;

[0015] Figure 2 It is a main circuit structure diagram of a hybrid grid-connected power suppression method and system of a grid-building and grid-following inverter based on dual mutual damping control according to an embodiment of the present invention;

[0016] Figure 3 A control block diagram of a method and system for suppressing power oscillations of a hybrid grid-connected inverter of a grid-building and grid-following type based on dual mutual damping control according to an embodiment of the present invention;

[0017] Figure 4 : The root locus variation diagram of the hybrid grid-connected power oscillation suppression method of the grid-building and grid-following inverter based on dual mutual damping control and the key system parameters when the system parameters change; (a) is K h1 and J1 change; (b) is the root locus change diagram when K h2 Root locus variation diagram when J1 changes;

[0018] Figure 5 1 is a diagram showing a step response change when a key parameter of a hybrid grid-connected power oscillation suppression method of a grid-building and grid-following inverter based on dual mutual damping control according to an embodiment of the present invention is changed; (a) is K h1 (b) is the step response change diagram when K h2 Step response change diagram when changing;

[0019] Figure 6 1 is a diagram showing the active power response of the system when the hybrid grid-connected system of the embodiment of the present invention uses different control modes under strong grid conditions; (a) is a diagram showing the active power response of the grid-connected inverter of the system when the hybrid grid-connected system of the embodiment of the present invention uses different control modes under strong grid conditions; (b) is a diagram showing the active power response of the grid-following inverter of the system when the hybrid grid-connected system of the embodiment of the present invention uses different control modes under strong grid conditions;

[0020] Figure 7 (a) is a diagram showing the active power response of the system when the hybrid grid-connected system of the embodiment of the present invention uses different control methods under weak grid conditions; (b) is a diagram showing the active power response of the system when the hybrid grid-connected system of the embodiment of the present invention uses different control methods under weak grid conditions. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] Embodiment 1 of the present invention provides a method for suppressing power oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type based on dual mutual damping control, such as Figure 1 As shown, the method includes:

[0024] S1: Obtain the voltage data of the grid-following inverter and the voltage and power data of the grid-forming inverter.

[0025] The voltage data of the grid-following inverter and the voltage and power data of the grid-forming inverter are sampled. The voltage of the grid-following inverter and the current, voltage, active power and reactive power data of the grid-forming inverter can be monitored in real time to evaluate the operating status and performance of the system. The benchmark data of the current, voltage, active power and reactive power data when the system is operating normally are provided.

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

[0027] It should be noted that Figure 2 The main circuit structure diagram of the hybrid grid-connected power suppression method and system of the grid-connected and grid-following inverter based on dual mutual damping control is shown. The hybrid grid-connected system is composed of a grid-connected inverter and a grid-following inverter in parallel. Usually, the grid-connected inverter is represented as an ideal voltage source, and the grid-following inverter is represented as an ideal current source. The grid-connected inverter and the grid-following inverter are respectively connected through the line impedance Z t1 and Z t2Connect to the point-of-common-coupling (PCC). g Represents the grid impedance, V 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-forming inverter output voltage vector and grid-following inverter output voltage vector respectively. Figure 3 The figure shows a control block diagram of a hybrid grid-connected power oscillation suppression method and system of grid-connected and grid-following inverters based on dual mutual damping control. The grid-connected inverter selects a voltage-controlled virtual synchronization generation (VVSG), while the grid-following inverter selects a current-controlled virtual synchronization generation (CVSG).

[0028] The control part of the grid-following inverter mainly includes the active power control outer loop, reactive power control outer loop, phase-locked loop, current control inner loop and PWM generation link. The active power control outer loop of the grid-following inverter consists of the active power reference value and the primary frequency modulation control loop, and 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 adopts PI control. The active power control loop and phase-locked loop principles of the grid-following inverter are:

[0029]

[0030] Among them, ω2,P e2 ,v 2q and θ2 represent the phase-locked loop angular frequency, active power, q-axis voltage and phase of the grid-following inverter output, respectively, while P n2 Indicates the reference active power. J2 and D p2 They 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, D′ p2 and K′ w2 The inertia parameters, damping coefficient and primary frequency modulation coefficient of the grid-connected inverter are consistent. f2 represents the differential filter coefficient. In addition, Gpll2 (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 Represent the proportional coefficient and integral coefficient respectively.

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

[0032]

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

[0034]

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

[0036]

[0037] In summary, combined with the above ΔP e2 The relationship between ΔI2 and ΔI2 and the relationship between Δω2, the output power small signal value ΔP of the grid-type inverter e2 Available own angular frequency small signal value Δω2 and PCC point angular frequency small signal value Δω bus It is expressed 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 to show the output power small signal value ΔP of the grid-connected inverter. e2 The small signal value of the PCC point angular frequency Δω bus The relationship is:

[0042]

[0043] S3: The grid-connected inverter uses a voltage-controlled virtual synchronous generator and dual mutual damping control inputted with voltage and power data to offset the interactive effects of the grid-connected inverter on the grid-connected inverter, and control the grid-connected power of the grid-connected inverter.

[0044] As can be seen from the above, the control algorithm of the grid-forming inverter adopts voltage-controlled virtual synchronous generator control, and double mutual damping control is added on this basis. The voltage-controlled virtual synchronous generator mainly includes the active power control outer loop, the reactive power control outer loop, the voltage control inner loop, the current control inner loop and the PWM generation link. The double mutual damping control includes the frequency mutual damping term and the power mutual damping term. These two mutual dampings are fed back to the active power control outer loop of the grid-forming inverter to suppress the interactive influence of the grid-following inverter on the grid-forming inverter.

[0045] The active power control outer loop of the grid-forming inverter is composed of an active power reference value and a primary frequency modulation control loop, and the reactive power control outer loop is composed of a reactive power reference value and a primary voltage regulation control loop. The active loop outputs a phase angle θ1, and the reactive loop outputs a voltage amplitude V1, which jointly control the grid-forming 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 are:

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

[0048]

[0049] Among them, ω1, V1, P e1 and Q e1 Respectively represent the angular frequency, voltage, active power and reactive power output by the grid-connected inverter, ω n 、V n1 , P n1 and Q n1 It indicates the corresponding reference value. ω1 is the primary frequency adjustment coefficient. D p1 and D q1 Represent the damping coefficient and voltage droop coefficient, J1 and J v1 are the inertia coefficients of the active power control outer loop and the reactive power control outer loop respectively.

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

[0051]

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

[0053]

[0054] To simplify the interaction analysis of the hybrid system, the line resistance R is neglected. t1 and R t2 In this case, the output power small signal value of the grid-connected inverter ΔP e1 Available own angular frequency small signal value Δω1 and PCC point angular frequency small signal value Δω bus It is expressed as:

[0055]

[0056] in:

[0057]

[0058] Therefore, Δω1 and ΔP e1 Relationship and ΔP e1 With Δω1, Δω bus The relational equations are combined to obtain the small signal value of the grid-type inverter output power ΔP e1 The small signal value of the PCC point angular frequency Δω bus The relationship is:

[0059]

[0060] in:

[0061]

[0062] In order to obtain the small signal value Δω of the PCC point angular frequency bus , we need to know the power ΔP at PCC bus and the grid angular frequency Δω bus The relationship between can be expressed 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 expressed 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 relationship into the above formula, we can get 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 active power value ΔP output by the grid-connected inverter. e1 :

[0071]

[0072] From the above formula, we can know that the grid-type inverter output power ΔP e1 Not only with its own active power reference value ΔP n1 It is also related to the active power reference value ΔP of the grid-following inverter. n2 Therefore, in order to offset the interaction of the active power of the grid-following inverter on the grid-forming inverter, it is necessary to satisfy ΔP n2 The numerator of the coefficient is 0.

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

[0074] When the hybrid system adopts the dual mutual damping control method combining angular frequency mutual damping and power mutual damping, the grid-type inverter outputs active power ΔP e1 and the active power reference value ΔP of the grid-following inverter n2 The interaction transfer function of is given above. Based on the interaction transfer function, the key parameter K can be obtained. h1 and K h2 In order to reasonably design Kh1 and K h2 The value of Figure 4 It shows that when J1 changes in the range of [1,8] under a strong power grid with a power grid short-circuit ratio of 7.7, K h1 and K h2 The influence on the dominant pole. h1 When K increases from 50 to 140, the dominant pole moves away from the imaginary axis, reducing the amplitude of the power oscillation. h1 As it continues to increase, the main pole will move away from the real axis and closer to the imaginary axis, indicating that the power oscillation is intensifying. Figure 4 It can be observed from (b) that when K h2 = 0.06, the pole s1 is far away from the imaginary axis, while s2 is close to the imaginary axis. h2 Increased to 0.02, s2 moves away from the imaginary axis and becomes symmetrical to s1 about the real axis, thus reducing the oscillation. h2 If it increases further, both s1 and s2 will be close to the imaginary axis, resulting in aggravated oscillation. Based on this analysis, the embodiment of the present invention selects K h1 =140 and K h2 =0.02. Similarly, based on the root locus method, it can be obtained that in the embodiment of the present invention, K is taken under a weak power grid with a power grid short-circuit ratio of 2.3. h1 =120 and K h2 When =0.005, the oscillation suppression effect is the best.

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

[0076] The method for suppressing power oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type based on dual mutual damping control in an embodiment of the present invention can simultaneously suppress power oscillations occurring in a grid-connected system in both strong and weak grid conditions. Figure 6 The figure shows the active power response of the grid-forming and grid-following inverters under strong grid conditions using different control algorithms. Under traditional control, as shown by the black line, when P n1 When the change occurs, P e1 and P e2 Overshoots of 4.95% and 1.58% occurred, lasting for 0.9 seconds and 0.6 seconds respectively. 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 and 0.6 seconds, respectively.

[0077] Under strong grid conditions, when frequency mutual damping control is applied only to grid-connected inverters, Figure 6 The red line indicates its active power. n1 or P n2 When a step change occurs, P e1 and P e2 All stabilized quickly within 0.3 seconds. However, when P n2 When a step change occurs, P e1 An overshoot of 6.15% occurs. Therefore, the angular frequency mutual damping effectively suppresses the oscillation of active power, but a certain overshoot still exists in the grid-connected inverter.

[0078] Under strong grid conditions, when only the power mutual damping control is applied to the grid-connected inverter, P e1 and P e2 Pn1 The response of the step change is similar to angular frequency mutual damping. However, when P n2 When a step occurs, due to the interaction effect, P e1 It dropped sharply by 10.45%, while P e2 It shows slight oscillation. Figure 6 The purple line in the figure represents the active power using the double mutual damping control method. e1 and P e2 P n1 The response of the step change is similar to the angular frequency mutual damping and power mutual damping methods. However, when P n2 When a step occurs, P e1 There was no overshoot, only a slight drop of about 4.7% and a quick return to a stable state.

[0079] For weak network conditions, such as Figure 7 As shown in Figure 2, compared with traditional control, the angular frequency mutual damping, power mutual damping and double mutual damping methods all effectively suppress P e1 and P e2 The double mutual damping control method achieves the best power oscillation suppression performance. In summary, the control strategy of the embodiment of the present invention effectively suppresses the power oscillation of the hybrid grid-connected system under strong and weak power grids.

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

[0081] The data acquisition module obtains the voltage data of the grid-following inverter and the voltage and power data of the grid-building inverter.

[0082] Feedback control module, the grid-following inverter controls the grid-connected power of the grid-following inverter through phase-locked loop control with voltage data input and current-controlled virtual synchronous generator control; the grid-building inverter controls the grid-connected power of the grid-building inverter through voltage-controlled virtual synchronous generator and dual mutual damping control with voltage and power data input, thereby offsetting the interactive influence of the grid-following inverter on the grid-building inverter.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] Example 2

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

[0089] The terminal device of 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 the above-mentioned embodiment 1.

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

[0091] In some other implementations, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors of various types, which are not limited herein.

[0092] Example 3

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

[0094] Computer readable storage media can be tangible devices that hold and store instructions used by instruction execution devices. Computer readable storage media can be, for example, but not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any combination thereof.

[0095] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt 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.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0096] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0098] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0099] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for suppressing power oscillation of a hybrid grid-connected inverter of a grid-building and grid-following type, characterized in that: The following steps are involved: Construct the following interaction transfer function: Among them, ΔP e1 is the small signal value of active power output by the grid-connected inverter, ΔP n1 and ΔP n2 are the reference power small signal disturbances of the grid-building and grid-following inverters, Δω g is the small signal disturbance of 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 Indicates the angular frequency reference value of the grid-connected inverter, J1, D p1 , K w1 are the inertia coefficient, damping coefficient and primary frequency modulation coefficient of the grid-connected inverter, J2, D p2 are the inertia coefficient and damping coefficient of the grid-following inverter, V 1o 、V g 、V buso are the steady-state voltage values ​​of the grid-connected inverter, grid, and PCC, respectively. t1 , X t2 , X g are the line impedance of the grid-building inverter, the line impedance of the grid-following inverter and the grid impedance, K h1 and K h2 are the frequency mutual damping coefficient and the power mutual damping coefficient respectively, and s is a complex variable; Based on the interaction transfer function, the key mutual damping coefficient K is obtained. h1 and K h2 Changes in the root locus and step response of the interaction transfer function when changing; Based on K h1 and K h2 When the ΔP changes e1 The principle that the root locus is farthest from the imaginary axis and ΔP e1 The key mutual damping coefficient K is obtained by the principle of minimum step response oscillation h1 and K h2 .

2. The method for suppressing power oscillation of hybrid grid-connected inverters of grid-building and grid-following type 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-building 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 according to claim 1 or 2.

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

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

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