Converter parallel operation virtual impedance angle adaptive control method and system

Abstract

The invention discloses a converter parallel operation virtual impedance angle self-adaptive control method and system, and relates to the technical field of converter system control, and the method comprises the steps: observing an active mean value and a reactive mean value through a consistency control algorithm; obtaining a trigonometric function value corresponding to the virtual impedance angle through the active mean value and the reactive mean value; obtaining virtual resistance and virtual negative reactance corresponding to each converter; performing power coordinate conversion on active power and reactive power of the converter by using the dynamically changed virtual impedance angle to obtain generalized active power and generalized reactive power; and generalized active power and generalized reactive power are controlled. The method is suitable for occasions where multiple converters operate in parallel, such as a micro-grid, the problem of voltage deviation after virtual impedance is introduced can be remarkably solved by dynamically adjusting the virtual impedance angle in real time, and the voltage quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of converter system control, and in particular to a method and system for adaptively controlling virtual impedance angles of converters running in parallel. Background Art

[0002] The control goal of the parallel operation of converters is to achieve proportional sharing of active and reactive power and reduce frequency and voltage deviations. Virtual impedance technology is widely used in the parallel operation of converters, including but not limited to microgrids. It can reshape the output impedance characteristics of the converter as needed, and decouple active and reactive control under complex line impedance characteristics (such as resistive, or neither resistive nor inductive) to achieve better control effects. However, the addition of virtual impedance will lead to large voltage deviations and deteriorate the power quality. At present, the secondary voltage regulation method based on consistency control is generally used to restore the average voltage (that is, the average voltage of all converters involved in the control) to the rated value. However, the large voltage sag caused by virtual impedance cannot be avoided, and it takes a certain amount of time for the secondary voltage to recover. Summary of the invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the technical problem solved by the present invention is: how to effectively control the sharing of active and reactive power under complex line impedance characteristics, while reducing the voltage deviation and sag caused by virtual impedance to improve power quality and shorten voltage recovery time.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for adaptively controlling virtual impedance angle of converters in parallel operation, comprising the following steps:

[0006] The mean active power and the mean reactive power are observed through the consistency control algorithm; the trigonometric function value corresponding to the virtual impedance angle is obtained through the mean active power and the mean reactive power; the virtual resistance and the virtual negative reactance corresponding to each converter are obtained; the active power and the reactive power of the converter are transformed into power coordinates using the dynamically changing virtual impedance angle to obtain the generalized active power and the generalized reactive power; the generalized active power and the generalized reactive power are controlled.

[0007] As a preferred solution of the virtual impedance angle adaptive control method for parallel operation of converters described in the present invention, wherein: wherein: the active mean value is expressed as,

[0008]

[0009] As a preferred solution of the virtual impedance angle adaptive control method for parallel operation of converters described in the present invention, the reactive mean value is expressed as

[0010]

[0011] The ratio of the active mean to the reactive mean is

[0012] The P ∑ It represents the sum of the active power of N converters, Q ∑ Represents the sum of reactive power of N converters, P i and Q i are the real-time active and reactive power of converter i, are the i-th row and j-th column elements of the active and reactive mean observation communication network adjacency matrix, C Pi and C Qi are active observation coupling coefficient and reactive observation coupling coefficient respectively, and are the mean active and reactive values ​​obtained by the active and reactive observers of converters i and j respectively.

[0013] As a preferred solution of the virtual impedance angle adaptive control method for parallel operation of converters described in the present invention, wherein: Calculate the virtual impedance angle of converter i The corresponding trigonometric function value is expressed as,

[0014]

[0015] in, and They represent the sine, cosine, tangent and cotangent values ​​corresponding to the virtual impedance angle respectively.

[0016] As a preferred solution of the method for adaptively controlling virtual impedance angle of converters in parallel operation described in the present invention, after obtaining the trigonometric function value, the virtual resistance and virtual negative reactance corresponding to each converter are obtained by fixed amplitude method, fixed resistance method and fixed reactance method.

[0017] As a preferred solution of the virtual impedance angle adaptive control method for parallel operation of converters described in the present invention, wherein: the amplitude of the virtual impedance of converter i is fixed in the fixed amplitude method, and the virtual resistance and virtual negative reactance are determined by the virtual impedance trigonometric function, which is expressed as:

[0018]

[0019] Among them, Z vi Expressed as the magnitude of the virtual impedance of fixed converter i, ωL vi Represents virtual negative reactance.

[0020] In the fixed resistance method, the virtual negative reactance is obtained by fixing the virtual resistance of the converter, which is expressed as:

[0021]

[0022] Among them, R vi represents the virtual resistance value of fixed converter i;

[0023] In the fixed reactance method, the virtual negative reactance of the fixed converter is used to obtain the virtual resistance, which is expressed as:

[0024]

[0025] Among them, ωL vi Indicates the virtual reactance value of fixed converter i.

[0026] As a preferred solution of the virtual impedance angle adaptive control method for parallel operation of converters described in the present invention, wherein: the control of generalized active power and generalized reactive power includes: gi and Q gi The converter is controlled using traditional droop control and consistency control algorithms.

[0027] Another object of the present invention is to provide a virtual impedance angle adaptive control system for parallel operation of converters, which can solve the problem of excessive voltage sag and slow voltage recovery caused by fixed virtual impedance in the prior art by dynamically adjusting the virtual impedance angle in real time.

[0028] To solve the above technical problems, the present invention provides the following technical solutions: a virtual impedance angle adaptive control system for converters running in parallel includes an observation module, a calculation and conversion module, an impedance adjustment module, and a power control module.

[0029] The observation module observes the mean values ​​of active power and reactive power of each converter through a consistency control algorithm.

[0030] The calculation and conversion module calculates the trigonometric function value of the virtual impedance angle through the observed active mean value and reactive mean value, calculates the virtual resistance and virtual negative reactance of each converter, and uses the dynamically changing virtual impedance angle to perform power coordinate transformation and convert it into generalized active power and generalized reactive power.

[0031] The impedance adjustment module adjusts the virtual impedance according to a fixed amplitude method, a fixed resistance method, and a fixed reactance method.

[0032] The power control module controls the generalized active power and generalized reactive power obtained through coordinate transformation.

[0033] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the virtual impedance angle adaptive control method for parallel operation of converters as described above are implemented.

[0034] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the virtual impedance angle adaptive control method for parallel operation of converters as described above.

[0035] Beneficial effects of the present invention: The present invention is applicable to occasions where multiple converters are operated in parallel, such as microgrids. By dynamically adjusting the virtual impedance angle in real time, the voltage deviation problem after the introduction of virtual impedance can be significantly improved, and the voltage quality can be improved. In addition, the present invention also enhances the flexibility and stability of the system, optimizes the efficiency of electric energy utilization, supports better integration of renewable energy, and enhances the anti-interference ability of the power grid. Similarly, the present invention not only improves the adaptability and response speed of power grid operation, but also helps to improve the efficiency and reliability of the entire system, which is particularly important in environments with large load fluctuations or unstable energy sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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.

[0037] Figure 1 This is an overall flow chart of the virtual impedance angle adaptive control method for parallel operation of converters provided by the first embodiment of the present invention.

[0038] Figure 2 A schematic diagram of voltage drop caused by virtual impedance in a method for adaptively controlling virtual impedance angle of converters in parallel operation provided by the first embodiment of the present invention.

[0039] Figure 3 A schematic diagram of grid-connected converters in a method for adaptively controlling virtual impedance angles of converters in parallel operation provided by a first embodiment of the present invention.

[0040] Figure 4 This is an overall framework diagram of a virtual impedance angle adaptive control system for parallel operation of converters provided in the second embodiment of the present invention.

[0041] Figure 5 A schematic diagram of a converter system in a method for adaptively controlling virtual impedance angles of converters in parallel operation provided by a third embodiment of the present invention.

[0042] FIG. 6( a ) is a diagram showing active power simulation results generated by a conventional method in a conventional virtual impedance control method for parallel operation of converters provided in a third embodiment of the present invention.

[0043] FIG6( b ) is a diagram showing reactive power simulation results generated by a conventional method in a conventional virtual impedance control method for parallel operation of converters provided in a third embodiment of the present invention.

[0044] FIG. 6( c ) is a diagram showing voltage simulation results generated by a conventional method in a conventional virtual impedance control method for parallel operation of converters provided in a third embodiment of the present invention.

[0045] FIG. 7( a ) is a diagram showing active power simulation results generated by a fixed amplitude method in a method for adaptively controlling virtual impedance angles of converters in parallel operation provided in a third embodiment of the present invention.

[0046] FIG. 7( b ) is a diagram showing reactive power simulation results generated by the fixed amplitude method in the virtual impedance angle adaptive control method for parallel operation of converters provided in the third embodiment of the present invention.

[0047] FIG. 7( c ) is a diagram showing voltage simulation results generated by the fixed amplitude method in the virtual impedance angle adaptive control method for parallel operation of converters provided in the third embodiment of the present invention.

[0048] FIG. 7( d ) is a diagram of a converter (P ) generated by a fixed amplitude method in a method for adaptively controlling a virtual impedance angle of a converter in parallel operation according to a third embodiment of the present invention. ∑ / Q ∑ ) i Observation result diagram.

[0049] FIG8( a ) is a diagram showing active power simulation results generated by a fixed resistance method in a method for adaptively controlling virtual impedance angles of converters in parallel operation provided in a third embodiment of the present invention.

[0050] FIG8( b ) is a diagram showing reactive power simulation results generated by a fixed resistance method in a method for adaptively controlling virtual impedance angles of converters in parallel operation provided by a third embodiment of the present invention.

[0051] FIG8( c ) is a diagram showing voltage simulation results generated by the fixed resistance method in the virtual impedance angle adaptive control method for parallel operation of converters provided in the third embodiment of the present invention.

[0052] FIG. 8( d ) is a diagram of a converter (P ) generated by a fixed resistance method in a method for adaptively controlling a virtual impedance angle of a converter in parallel operation provided by a third embodiment of the present invention. ∑ / Q ∑ ) i Observation result diagram.

[0053] FIG9( a ) is a diagram showing active power simulation results generated by the fixed reactance method in the virtual impedance angle adaptive control method for parallel operation of converters provided in the third embodiment of the present invention.

[0054] FIG9( b ) is a diagram showing reactive power simulation results generated by the fixed reactance method in the virtual impedance angle adaptive control method for parallel operation of converters provided in the third embodiment of the present invention.

[0055] FIG9( c ) is a diagram showing voltage simulation results generated by the fixed reactance method in the virtual impedance angle adaptive control method for parallel operation of converters provided in the third embodiment of the present invention.

[0056] FIG. 9( d ) is a diagram of a converter (P ) generated by a fixed reactance method in a method for adaptively controlling a virtual impedance angle of a converter in parallel operation according to a third embodiment of the present invention. ∑ / Q ∑ ) i Observation result diagram. DETAILED DESCRIPTION

[0057] 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.

[0058] Example 1, reference Figure 1 to Figure 3 , is an embodiment of the present invention, and provides a converter parallel operation control method, characterized in that:

[0059] The technical solutions to supplement the prior art are as follows.

[0060] When multiple converters are operated in parallel, the control of each converter usually includes a power loop and a voltage tracking loop. The goal of the power loop is to use the active and reactive power of the converter to generate voltage amplitude and frequency (phase angle) through a certain algorithm (the commonly used technical solution is a combination of droop control and consistency control algorithm), and then generate a command voltage (virtual impedance may be introduced); the goal of the voltage tracking loop is to control the converter output voltage to track the command voltage, usually using a voltage and current dual closed-loop control method. The present invention is aimed at the power loop, so only the droop control, virtual impedance and consistency control algorithms that are closely related to the power loop are introduced.

[0061] (1) Droop control

[0062] Pf, QV droop control is widely used in the parallel operation control of converters. When the line is inductive (i.e., the line reactance X is much larger than the line resistance R), the converter active power P mainly depends on the frequency, and the converter reactive power Q mainly depends on the voltage V. That is, the converter frequency and voltage are calculated using equations (1) and (2).

[0063] f i =fN -m i P i (1)

[0064] V i =V N -n i Q i (2)

[0065] Active power control can also adopt power angle droop, and the power angle of converter i is calculated by equation (3).

[0066] θ i =θ N -m i P i (3)

[0067] In formula (1) to formula (3), f i 、V i ,θ i 、f N 、V N and θ N Represent the frequency, voltage and power angle of converter i and their rated values, P i and Q i are the active and reactive power of converter i, m i and n i Represents the normalization coefficient of active and reactive power, which is generally selected in inverse proportion to the rated capacity.

[0068] Get f i (or θ i ) and voltage V i After that, the original command voltage of converter i can be synthesized and written into the phase form V without loss of generality. i * ∠δ i .

[0069] (2) Virtual impedance.

[0070] In microgrids and other occasions, the line is neither resistive nor inductive (i.e., the line reactance X and line resistance R are not much different). At this time, P and Q are strongly coupled, and the Pf, QV droop control effect is greatly affected and even difficult to maintain stability. Virtual impedance is an effective means to solve this problem. By subtracting the converter output current in the virtual impedance R from the original converter command voltage, V +jωL V Taking the three-phase three-wire dq rotating coordinate system as an example, the voltage drop of the output current of converter i on the virtual impedance is shown in formula (4):

[0071]

[0072] In formula (4), I oi-d ,I oi-q 、V vi-d and V vi-d are the d-axis and q-axis components of the output current of converter i and its voltage drop across the virtual impedance, R vi and L vi are the virtual resistance and reactance introduced by converter i, ω=2πf i is the angular frequency of the electrical quantity. For simplicity, the rated frequency f can also be used directly when calculating the angular frequency. N .

[0073] The command voltage of converter i is calculated according to formula (5):

[0074]

[0075] In formula (5) are the original command voltage V of converter i i * ∠δ i The d-axis and q-axis components, V di-ref 、V qi-ref They are the d-axis and q-axis components of the actual command voltage of converter i after considering the effect of virtual impedance.

[0076] (3) Consistency Control Algorithm

[0077] The consensus algorithm is a decentralized control algorithm. Each agent (corresponding to each converter in the present invention) forms a consensus protocol by exchanging information with neighboring agents and controls itself according to the consensus protocol to achieve target consistency. In the consensus algorithm, the communication network between N agents can be represented by the adjacency matrix A. G =[a ij ]∈R N×N Indicates that the element a ii =0,a ij represents the communication weight between agents i and j. If agent i can obtain information from agent j, then a ij > 0. All agents that can provide information to agent i form its neighbors, represented by N i If a ij =a ji , then the communication network is called an undirected graph, otherwise it is a directed graph. The Laplacian matrix of the communication network is the N-order matrix L G =[l ij ]∈R N×N , whose diagonal elements are The off-diagonal elements are l ij =-a ij .

[0078] In the consensus algorithm, each agent follows A G Communicate with neighboring agents, learn their state information X, generate a consistency protocol, and update their own state. Taking the linear consistency algorithm as an example, each agent updates its own state according to formula (6).

[0079]

[0080] When the graph G is a connected undirected graph or a strongly connected directed graph, 0 is L G The simple eigenvalue of is , and all other eigenvalues ​​have positive real parts. Therefore, Equation (6) ensures that the states of all agents converge to the same value asymptotically in an exponential manner.

[0081] The consistency control algorithm is mainly used in the parallel operation control of converters to realize the proportional sharing of active and reactive power and restore the average voltage of the converter to the rated value. In order to realize the proportional sharing of reactive power, the consistency protocol shown in formula (7) can be used.

[0082]

[0083] In formula (7), g Q is the reactive power control coupling coefficient, n i and n j is the reactive power normalization coefficient. In order to restore the average voltage of the converter, the voltage mean of all converters needs to be observed according to formula (8).

[0084]

[0085] in, and V i are the mean voltage observation value and voltage measurement value obtained by converter i respectively; is the mean observed value of the voltage of converter j. V is the voltage observation coupling coefficient, is the i-th row and j-th column element of the voltage observation communication network adjacency matrix, N i is the set of neighboring converters of converter i, and s is the Laplace operator. When the algorithm converges, the voltage mean observation values ​​obtained by all converters are equal. The original command voltage amplitude V considering reactive power proportional sharing and average voltage recovery * As shown in formula (9).

[0086]

[0087] In order to realize the proportional sharing of active power, the power angle δ of converter i can be calculated according to formula (10): i Make adjustments.

[0088]

[0089] In formula (10), g P is the active power control coupling coefficient.

[0090] Get V i * and δ i The original command voltage can be synthesized, and the actual command voltage of converter i can be obtained by subtracting the voltage drop of the output current of converter i on the virtual impedance.

[0091] Disadvantages of the prior art.

[0092] The main disadvantages of the existing technology are: adding virtual impedance will lead to large voltage deviation and deteriorate the power quality. Although the secondary voltage regulation method based on consistency control can restore the average voltage to the rated value, it takes a certain amount of time for the secondary voltage to recover, and the large temporary low voltage caused by virtual impedance cannot be avoided.

[0093] To solve the above technical problems, the method principle of the present invention is as follows Figure 2 shown.

[0094] According to the circuit principle, for converter i, a virtual reactance ωL is introduced vi After that, the resulting voltage will mainly include the longitudinal component ΔV and the transverse component δV. The voltage drop caused by the virtual impedance is mainly the longitudinal component ΔV, as shown in formula (11).

[0095]

[0096] It can be seen from equation (11) that if the virtual resistance and virtual negative reactance are selected to satisfy equation (12), the longitudinal component of the voltage drop can be eliminated.

[0097]

[0098] From equation (12), we can see that in order to eliminate the longitudinal component of the voltage drop caused by the virtual impedance, it is necessary to calculate the reactive power Q of the converter i according to i and active power P i The virtual resistance and virtual negative reactance are adjusted by the ratio of . In order to ensure stable control, all converters should use the same virtual resistance and virtual negative reactance ratio. ∑ and total reactive power Q ∑ are the sum of the active and reactive power of N converters respectively. ∑ and Q ∑ In the process of calculating the ratio of virtual resistance and virtual negative reactance of all converters, the following should be used uniformly: To obtain For any converter i, the reactive power and active power observers are used to obtain the active power mean value: and reactive power mean The ratio of the two is pass Realize Estimates.

[0099] S1: Observe the mean active power and mean reactive power through the consistency control algorithm.

[0100] For any converter i, the reactive power observer and active power observer can be obtained by observing equation (13) and equation (14) respectively: and

[0101]

[0102] In formula (13) and formula (14), are the i-th row and j-th column elements of the active and reactive mean observation communication network adjacency matrix, C Pi and C Qi are active observation coupling coefficient and reactive observation coupling coefficient, respectively, i and Q i are the real-time active and reactive power of converter i, and are the mean active and reactive values ​​obtained by the active and reactive observers of converters i and j respectively.

[0103] S2: Obtain the trigonometric function value corresponding to the virtual impedance angle through the active mean value and the reactive mean value.

[0104] Obtained through active power observer and reactive power observer After the ratio is calculated, the virtual impedance angle of converter i is calculated using equation (15): The corresponding trigonometric function values.

[0105]

[0106] in, and They represent the sine, cosine, tangent and cotangent values ​​corresponding to the virtual impedance angle respectively.

[0107] S3: Obtain the virtual resistance and virtual negative reactance corresponding to each converter.

[0108] After obtaining the trigonometric function values, the virtual resistance and virtual negative reactance are obtained by one of the following three methods.

[0109] The methods include fixed amplitude method, fixed resistance method and fixed reactance method.

[0110] Method 1: Fixed amplitude method: Fixed amplitude Z of virtual impedance of converter i vi, the virtual resistance and virtual negative reactance are determined by the virtual impedance trigonometric function, that is, the virtual resistance R is calculated according to equations (16) and (17): vi and virtual negative reactance ωL vi (where ω represents the angular frequency of the electrical quantity)

[0111]

[0112]

[0113] Method 2: Fixed resistance method: fix the virtual resistance R of converter i vi , the virtual negative reactance ωL is obtained by formula (18): vi :

[0114]

[0115] Method 3: Fixed reactance method: Fixed virtual negative reactance ωL of converter i vi , find the virtual resistance R vi , as shown in formula (19):

[0116]

[0117] S4: Use the dynamically changing virtual impedance angle to perform power coordinate transformation on the active and reactive power of the converter to obtain generalized active power and generalized reactive power.

[0118] After obtaining the virtual impedance, the active power P of converter i is i and reactive Q i Perform power coordinate transformation to obtain generalized active power and generalized reactive power, as shown in formula (20).

[0119]

[0120] In formula (20), P gi and Q gi Represent the generalized active power and generalized reactive power of converter i respectively; combined Figure 3 , for any converter i, its active power P i and reactive Q i The expression is shown in (21):

[0121]

[0122] In formula (21), R vi is a virtual resistor, X vi =ωL vi is the virtual reactance, V i ∠δ i is the voltage phasor before the virtual reactance of converter i, V bi∠δ0 is the grid-connected point voltage phasor of converter i (please refer to Figure 3 ).

[0123] After power coordinate transformation, P gi and Q gi The expression of is shown in (22):

[0124]

[0125] In formulas (21) and (22), V i ∠δ i and V bi ∠0 is the voltage before the virtual impedance of converter i and the voltage phasor at the grid connection point, V i and V bi is the effective value. If the voltage tracking error is not considered, V i It is equal to the effective value of the original command voltage of converter i; i is the phase angle difference, i.e. the power angle of converter i, X vi =-ωL vi is the virtual negative reactance introduced.

[0126] S5: Control generalized active power and generalized reactive power.

[0127] P gi and Q gi The converter is controlled by conventional droop control (frequency droop or phase angle droop) and consistency control algorithm, thereby achieving proportional sharing of active and reactive power and recovery of frequency and voltage.

[0128] Example 2, reference Figure 4 , which is an embodiment of the present invention, provides a system for a method for adaptively controlling a virtual impedance angle of converters in parallel operation, characterized in that it includes an observation module 100, a calculation and conversion module 200, an impedance adjustment module 300, and a power control module 400.

[0129] The observation module 100 observes the mean values ​​of active power and reactive power of each converter through a consistency control algorithm.

[0130] The calculation and conversion module 200 calculates the trigonometric function value of the virtual impedance angle through the observed active mean value and reactive mean value, calculates the virtual resistance and virtual negative reactance of each converter, and uses the dynamically changing virtual impedance angle to perform power coordinate transformation and convert it into generalized active power and generalized reactive power.

[0131] The impedance adjustment module 300 adjusts the virtual impedance according to a fixed amplitude method, a fixed resistance method, and a fixed reactance method.

[0132] The power control module 400 controls the generalized active power and generalized reactive power obtained through coordinate transformation.

[0133] If the 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 a computer device (which can be a personal computer, a server, or a 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 code.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] Example 3, reference Figure 5 - Figure 9, in this embodiment, in order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments. This embodiment experiments the existing traditional method and the method of this embodiment respectively.

[0138] In order to verify the effectiveness of the present invention, a simulation was carried out. Figure 5 As shown in FIG. 1 , it includes four three-phase three-wire parallel voltage source converters (VSCs), using LC filtering, with a rated line voltage of 380V (phase voltage of 220V), a rated frequency of 50Hz, and connected to each other through RL lines; loads 1, 2, 3, and 4 are Y-connected series RL constant impedance loads, and the electrical parameters are shown in Table 1. The method in this paper requires that the communication topology is an undirected graph, such as Figure 5 The network is shown in medium grey dashed line.

[0139] Active and reactive consistency control, active and reactive observation, and voltage observation use the same communication network, and the adjacency matrix is ​​shown in (22).

[0140]

[0141] Table 1 System electrical parameters

[0142]

[0143] The ratio of the rated capacities of the four converters VSC1:VSC2:VSC3:VSC4 is 2:1:2:1. The traditional method and the present invention are compared. The traditional method directly introduces virtual reactance and uses a linear consistency algorithm to adjust the voltage to achieve proportional sharing of reactive power and recovery of the voltage mean (such as equations (7) and (9)); the linear consistency algorithm is used to adjust the converter phase angle to achieve proportional sharing of active power, as shown in equation (10). The power loop control parameter settings are shown in Table 2, and a voltage and current double closed loop is used for voltage tracking.

[0144] Table 2 Control parameters

[0145]

[0146]

[0147] Load 1 is switched on at 0.5s and removed at 1s. Since the ratio of the rated capacities of the four converters is: VSC1:VSC2:VSC3:VSC4=2:1:2:1, it is hoped that the ratio of their shared active and reactive power will be 2:1:2:1 respectively. In order to facilitate the analysis of whether the power is shared in proportion, the active power P and reactive power Q of each converter are multiplied by a certain coefficient. In all the following simulation figures, k1=k3=1; k2=k4=2; r1=r3=1; r2=r4=2. The results are shown in Figures 6 to 9. In Figures 6 to 9, P1, P2, P3 and P4 represent the active power of converters 1, 2, 3 and 4 respectively, Q1, Q2, Q3 and Q4 are the reactive power of the four converters, V1, V2, V3, V4 and V avg Represent the phase voltage and phase voltage average of the four converters respectively.

[0148] Traditional method simulation results

[0149] The simulation results of the traditional method are shown in Figure 6, where Figures 6(a), (b) and (c) are the simulation results of active power, reactive power and voltage of the four converters. Figures 6(a) and (b) show that the converter can realize the proportional sharing of active power and reactive power as required; Figure 6(c) shows that the voltage average of the four converters can be restored to the rated value, but due to the effect of virtual reactance, each converter has a large voltage drop, and the recovery process takes a relatively long time.

[0150] Simulation results of the present invention

[0151] Figures 7 to 9 are the simulation results of the present invention, wherein Figure 7 is the simulation result of the fixed amplitude method, Figure 8 is the simulation result of the fixed resistance method, and Figure 9 is the simulation result of the fixed reactance method. It can be seen from Figures 7 to 9 that the present invention can achieve proportional sharing of active and reactive power; by comparing the voltage simulation results of Figures 7(c), 8(c) and 9(c) with the traditional method of Figure 6(c), it can be seen that the voltage sag caused by virtual impedance can be greatly reduced by the present invention: the minimum value of the converter phase voltage is above 205V, while the minimum value of the converter phase voltage using the traditional method is less than 195V; in addition, compared with the traditional method, the voltage recovery time can be significantly shortened by the present invention. Figures 7(d), 8(d) and 9(d) are the three methods for four converters (P ∑ / Q ∑ ) i Observation results,It can be seen from the figure that the observation results of the four converters are highly consistent. The present invention can achieve accurate observation of the active and reactive ratio of the total load.

[0152] 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. A method for adaptively controlling virtual impedance angle of converters in parallel operation, characterized in that: include: Observe the mean active power and mean reactive power through the consistency control algorithm; The trigonometric function value corresponding to the virtual impedance angle is obtained through the active mean value and the reactive mean value; Obtaining virtual resistance and virtual negative reactance corresponding to each converter; The dynamic virtual impedance angle is used to transform the active and reactive power of the converter into power coordinates to obtain generalized active power and generalized reactive power. Control the generalized active power and generalized reactive power.

2. The method for adaptively controlling virtual impedance angle of converters in parallel operation according to claim 1, characterized in that: The active mean value is expressed as, 3. The method for adaptively controlling virtual impedance angle of converters in parallel operation according to claim 2, characterized in that: The reactive power mean value is expressed as The ratio of the active mean to the reactive mean is The P ∑ It represents the sum of the active power of N converters, Q ∑ Represents the sum of reactive power of N converters, P i and Q i are the real-time active and reactive power of converter i, are the i-th row and j-th column elements of the active and reactive mean observation communication network adjacency matrix, C Pi and C Qi are active observation coupling coefficient and reactive observation coupling coefficient respectively, and are the mean active and reactive values ​​obtained by the active and reactive observers of converter i and j respectively.

4. The method for adaptively controlling virtual impedance angle of converters in parallel operation according to claim 3, characterized in that: pass Calculate the virtual impedance angle of converter i The corresponding trigonometric function value is expressed as, in, and They represent the sine, cosine, tangent and cotangent values ​​corresponding to the virtual impedance angle respectively.

5. The method for adaptively controlling virtual impedance angle of converters in parallel operation according to claim 4, characterized in that: After the trigonometric function values ​​are obtained, the virtual resistance and virtual negative reactance corresponding to each converter are obtained by a fixed amplitude method, a fixed resistance method, and a fixed reactance method.

6. The method for adaptively controlling virtual impedance angle of converters in parallel operation according to claim 5, characterized in that: In the fixed amplitude method, the amplitude of the virtual impedance of the converter i is fixed, and the virtual resistance and virtual negative reactance are determined by the virtual impedance trigonometric function, which is expressed as: Among them, Z vi Expressed as the magnitude of the virtual impedance of fixed converter i, ωL vi represents virtual negative reactance; In the fixed resistance method, the virtual negative reactance is obtained by fixing the virtual resistance of the converter, which is expressed as: Among them, R vi represents the virtual resistance value of the fixed converter i; In the fixed reactance method, the virtual negative reactance of the fixed converter is used to obtain the virtual resistance, which is expressed as: Among them, ωL vi Indicates the virtual reactance value of fixed converter i.

7. The method for adaptively controlling virtual impedance angle of converters in parallel operation according to claim 6, characterized in that: The control of generalized active power and generalized reactive power includes: gi and Q gi The converter is controlled using traditional droop control and consistency control algorithms.

8. A system using the method for adaptively controlling virtual impedance angle of converters in parallel operation as claimed in any one of claims 1 to 7, characterized in that: It comprises an observation module (100), a calculation and conversion module (200), an impedance adjustment module (300), and a power control module (400); The observation module (100) observes the mean value of active power and reactive power of each converter through a consistency control algorithm; The calculation and conversion module (200) calculates the trigonometric function value of the virtual impedance angle through the observed active mean value and reactive mean value, calculates the virtual resistance and virtual negative reactance of each converter, and uses the dynamically changing virtual impedance angle to perform power coordinate transformation and convert it into generalized active power and generalized reactive power; The impedance adjustment module (300) adjusts the virtual impedance according to a fixed amplitude method, a fixed resistance method and a fixed reactance method; The power control module (400) controls the generalized active power and generalized reactive power obtained through coordinate transformation.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for adaptively controlling virtual impedance angle of parallel operation of converters according to any one of claims 1 to 7 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 adaptively controlling virtual impedance angle of parallel operation of converters according to any one of claims 1 to 7 are implemented.

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