Fault component compensation type low voltage ride through control method and system of distributed power generation system and storage medium

Abstract

The invention discloses a fault component compensation type low-voltage ride-through control method and system of a distributed power generation system and a storage medium, and the method comprises the steps: introducing a difference value between a d-axis voltage instantaneous component of a common coupling point and a system rated voltage into a quadrature-axis voltage compensation branch during the voltage drop period of a power grid, and obtaining a quadrature-axis voltage compensation amount through compensation coefficient calculation, the calculation result is added to the phase-locked loop control link, the q-axis voltage of the common coupling point tracked by the phase-locked loop is adjusted in real time, and the problem that the phase angle of the distributed power generation system is prone to loss stability during the transient state is effectively solved without any additional control information. And the low-voltage ride-through capability of the distributed power generation system under the extreme working condition is obviously enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of reliable operation and stable control of micro-grid, and particularly to a fault component compensation type low voltage ride through control method and system of a distributed power generation system and a storage medium. BACKGROUND

[0002] Unlike the traditional synchronous generator which relies on the rotor inertia to achieve natural synchronization characteristics, the renewable energy generation system based on voltage source converter (VSC) lacks physical inertia and must track the voltage phase of the PCC point in real time through the phase-locked loop (PLL) to achieve accurate synchronization with the grid, which fundamentally changes the synchronization mechanism.

[0003] In a weak grid environment, the voltage amplitude and phase at the PCC point are affected by the coupling of grid impedance and injected current, and show strong sensitivity to external disturbances. Studies have shown that when VSC is connected to a weak grid, the additional feedback loop formed by the phase-locked loop and the high line impedance will significantly affect the dynamic characteristics of the system, causing the grid-connected inverter to easily lose synchronization under large disturbances, which seriously threatens the safe and stable operation of the power system. Therefore, it is of great significance to study the transient synchronization stability mechanism of the grid-connected inverter based on PLL under weak grid conditions and improve the transient stability of the system to ensure the safe and reliable operation of the grid with high proportion of new energy.

[0004] Currently, to avoid the loss of synchronization of VSC based on PLL, various control methods have been proposed. Some studies dynamically adjust the active current of the distributed power generation system to improve the transient stability under large grid disturbances. Another study detects the grid voltage and grid impedance and adds a transient damping loop after the PI controller of the SRF-PLL, which can adaptively inject damping during disturbances. However, the above methods rely on accurate estimation of the grid impedance. Given the close relationship between the transient stability of the distributed power generation system and the PLL, scholars directly freeze the PLL when the grid fails, thereby improving the transient stability of the VSC, but freezing the PLL makes it difficult to achieve accurate synchronization with the grid; in addition, the parameters of the PLL can be adjusted and optimized in real time to enhance the transient damping of the inverter under severe disturbances. However, due to the short duration of the transient state and the nonlinear characteristics of the transient damping, strategies based on adjusting active power and optimizing PI parameters in real time are often difficult to implement in engineering practice. In summary, the existing transient stability enhancement strategies are generally complex and lack engineering applicability. With the advancement of related technologies, there is an urgent need for a new type of distributed low voltage ride through suppression strategy that is simple and efficient, does not require additional line impedance measurement, and can directly perform compensation control on the distributed power generation system side to improve the transient stability and power supply reliability of the distributed power generation system.

[0005] The low-voltage ride-through comprehensive control method of the virtual synchronous machine proposed in the patent CN114069709B can achieve current balance and power pulsation suppression through positive and negative sequence component control during voltage drop, but its control structure has multiple levels and complex algorithm, relies on positive and negative sequence separation and fixed virtual resistance parameters, has response lag and is difficult to adapt to different power grid conditions, especially without considering that the phase angle of the distributed power generation system containing a phase-locked loop (PLL) is easy to diverge and the control is unstable under extreme conditions. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a fault component compensation type low-voltage ride-through control method, system and storage medium for a distributed power generation system, which retains the distributed control characteristics of new energy power generation without detecting the line impedance parameters and without the system providing any additional control information, solves the problem of poor low-voltage ride-through capability caused by the easy divergence and instability of the phase angle of the distributed power generation system under the voltage drop scenario of the power grid, and realizes the low-voltage ride-through of the distributed power generation system under the transient scenario, thereby ensuring the safe and stable operation of the system.

[0007] To solve the above technical problems, the technical solution adopted by the present application is as follows: a fault component compensation type low-voltage ride-through control method for a distributed power generation system, comprising the following steps:

[0008] Sampling the three-phase output voltage and three-phase output current of the distributed power generation system, performing Park transformation on the three-phase output voltage to obtain the d-axis voltage component U d and the q-axis voltage component U q of the output of the distributed power generation system, and performing Park transformation on the three-phase output current to obtain the d-axis current component I d and the q-axis current component I q of the output of the distributed power generation system;

[0009] According to the d-axis component U d of the output voltage of the distributed power generation system and the rated voltage U N of the system, a transient quadrature-axis voltage feedforward compensation component U C is calculated;

[0010] According to the q-axis voltage component U q of the output of the distributed power generation system and the transient quadrature-axis voltage feedforward compensation component U C , a current phase θ GFL is calculated;

[0011] According to the d-axis voltage component U d , the q-axis voltage component U q , the d-axis current component I d , and the q-axis current component I qd-axis current reference I dn q-axis current reference I qn and current phase θ GFL Calculate the d-axis electromotive force e of the generator terminal voltage of a distributed generation system. d and q-axis electromotive force e q ;

[0012] d-axis electromotive force e d and q-axis electromotive force e q Performing the inverse Park transform, the output three-phase electromotive force of the distributed generation system is obtained, based on the current phase θ. GFL and output three-phase electromotive force e abc The grid-connected converter is modulated with PWM to obtain the switching drive signal PWM for the distributed generation system.

[0013] This invention introduces a transient quadrature-axis voltage feedforward compensation component related to the d-axis voltage component and the rated voltage into the phase-locked loop (PLL) control stage of a distributed generation system (DRG). This effectively suppresses the inherent hysteresis characteristic of the PLL control stage under low-voltage ride-through scenarios, enhances the DRG's low-voltage ride-through capability, and ensures reliable and stable system operation. By introducing a quadrature-axis voltage feedforward compensation based on the difference between the d-axis voltage and the rated voltage into the PLL control stage, this invention directly corrects the dynamic hysteresis characteristic of the PLL, achieving rapid suppression of transient phase angle shifts. This method requires no positive-negative sequence separation or additional hardware support; parameters are adaptively adjustable; the control structure is simple and responsive; and it significantly improves the low-voltage ride-through capability and engineering feasibility of the DRG while ensuring system synchronization and stability.

[0014] Transient quadrature-axis voltage feedforward compensation component U C The calculation formula is:

[0015] ;

[0016] Wherein, λ is the quadrature-axis voltage feedforward compensation coefficient, and its value range needs to be matched with the degree of grid voltage drop. It should be flexibly selected between 0 and 30 to avoid the situation where a small compensation coefficient cannot meet the system requirements when the grid voltage drop is large, so that the system has a better transient stability margin and improves the reliability of system operation.

[0017] Current phase θ GFL The calculation formula is:

[0018] ;

[0019] Among them, K p and K p These are the proportional and integral coefficients of the phase-locked loop PI controller, respectively.

[0020] d-axis current component I d q-axis current component I q The calculation formula is:

[0021]

[0022] Among them, i a i b i c This refers to the three-phase output current of the distributed generation system.

[0023] d-axis electromotive force e d and q-axis electromotive force e q The calculation formula is:

[0024] ;

[0025] Among them, K p_i and K i_i L represents the proportional coefficient and integral coefficient of the current control, respectively. f and ω n These represent the output filter inductance value and rated angular frequency of the distributed generation system, respectively.

[0026] As an inventive concept, the present invention also provides a fault component compensation type low voltage ride-through control system for a distributed generation system under extreme operating conditions, including one or more processors and a memory; the memory stores one or more programs, which, when executed by the one or more processors, cause the one or more processors to implement the steps of the above method.

[0027] 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.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention introduces a transient quadrature-axis voltage feedforward compensation component related to the d-axis voltage component and the rated voltage into the phase-locked loop control loop of a distributed generation system. This effectively suppresses the inherent hysteresis characteristics of the phase-locked loop control loop of the distributed generation system under low-voltage ride-through scenarios, enhances the low-voltage ride-through capability of the distributed generation system, and ensures the reliable and stable operation of the system.

[0030] 2. The voltage and current data used in this invention can be directly detected by the voltage and current data acquisition module and processed in real time by the control chip, resulting in simple implementation and low operational complexity. Furthermore, this invention retains the distributed control characteristics of the new energy power generation system without requiring the detection of line impedance parameters or any additional control information from the system. No interconnection communication between the converter and the system is required, thus eliminating the need to consider potential data loss and transmission delays during information interconnection.

[0031] 3. During steady-state operation of the system, due to the d-axis voltage component u d and rated voltage U N They are approximately equal, i.e., u d ≈U N Therefore, the transient quadrature-axis voltage feedforward compensation component U C Its value is 0 when the system is in steady state, therefore this invention does not affect the steady-state operating point of the distributed generation system. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the distributed generation grid-connected system structure under extreme operating conditions in an embodiment of the present invention;

[0033] Figure 2 This is a block diagram of a phase-locked loop control based on quadrature-axis voltage feedforward compensation in an embodiment of the present invention;

[0034] Figure 3 This is a graph showing the relationship between the compensation coefficient λ and the grid voltage drop in this embodiment of the invention.

[0035] Figure 4 This is a control block diagram of the dq decoupling control in a distributed generation grid-connected system according to an embodiment of the present invention;

[0036] Figure 5 (a) and (b) in the embodiments of the present invention are comparison diagrams of the simulated waveforms of the three-phase voltage, three-phase current, phase angle and frequency of the phase-locked loop output by the distributed generation system before and after the introduction of the proposed low voltage ride-through control method. Detailed Implementation

[0037] 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.

[0038] Example 1

[0039] likeFigure 1 As shown, the distributed generation system structure of this embodiment includes a distributed generation system using dq decoupling control. The output of the distributed generation system is connected to a filter inductor and then connected to the AC bus.

[0040] exist Figure 1 In the middle, L f Z is the output filter inductor for a distributed generation system. line U is the line impedance on the power grid side. abc The three-phase voltage output by the distributed generation system; I abc The three-phase current output by the distributed generation system; e abc The three-phase electromotive force output by the distributed generation system is PWM, which is the drive signal for the switching transistors of the distributed generation system.

[0041] like Figure 2 and Figure 4 As shown, the specific implementation steps of the low-voltage ride-through control method and system for distributed generation systems under extreme operating conditions in this embodiment of the invention include:

[0042] Step 1: Sampling and Power Calculation

[0043] The three-phase output voltage and three-phase output current of the distributed generation system are sampled, and the d-axis voltage component U of the distributed generation system output is obtained by performing Park transform on the three-phase output voltage. d and q-axis voltage component U q The d-axis current component I of the distributed generation system is obtained by performing Park transformation on the three-phase output current. d and q-axis current component I q ;

[0044] Step 2: Generation of transient quadrature-axis voltage feedforward compensation component

[0045] Based on the d-axis component U of the output voltage of the distributed generation system d and the system's rated voltage U N The transient quadrature-axis voltage feedforward compensation component U is calculated. C The specific formula is as follows:

[0046] ;

[0047] Where λ is the quadrature-axis voltage feedforward compensation coefficient. The relationship between the compensation coefficient λ and the grid voltage drop is as follows: Figure 3 As shown.

[0048] Step 3: Current Phase Calculation

[0049] Based on the q-axis voltage component U of the distributed generation system calculated in step 1 qThe transient quadrature-axis voltage feedforward compensation component U calculated in step 2 C Calculate the current phase θ GFL The specific formula is as follows:

[0050] ;

[0051] Among them, K p and K p These are the proportional and integral coefficients of the phase-locked loop PI controller, respectively.

[0052] Step 4: Modulation voltage generation

[0053] Based on the d-axis voltage component U of the distributed generation system calculated in step 1 d q-axis voltage component U q d-axis current component I d and q-axis current component I q The current phase θ calculated in step 3 GFL and the d-axis current reference I of the distributed generation system dn and q-axis current reference I qn Calculate the d-axis electromotive force e of the generator terminal voltage of a distributed generation system. d and q-axis electromotive force e q The specific formula is as follows:

[0054] ;

[0055] Among them, K p_i and K i_i L represents the proportional coefficient and integral coefficient of the current control, respectively. f and ω n These represent the output filter inductance value and rated angular frequency of the distributed generation system, respectively.

[0056] Step 5: Generation of drive signals

[0057] The d-axis electromotive force e calculated in step 4 d and q-axis electromotive force e q The inverse Park transform is performed to obtain the output three-phase electromotive force of the distributed generation system, based on the current phase θ. GFL and output three-phase electromotive force e abc The distributed generation system is modulated with PWM to obtain the switching transistor drive signal PWM of the distributed generation system.

[0058] like Figure 5As shown in (a) and 4(b) of the figure, the simulation waveforms of the three-phase voltage, three-phase current, and phase angle and frequency of the phase-locked loop (PLL) output of the distributed generation system before and after the introduction of the proposed low-voltage ride-through control method are compared in this embodiment of the invention. The distributed generation system follows the grid specifications: during grid voltage dips, the distributed generation system must withstand 1.2 times the rated current and provide 2% reactive current for every 1% voltage deviation. Based on this, the simulation is set so that the grid voltage drops by 0.4 pu at 0.4 s and recovers to 1.0 pu at 1.6 s. When the proposed low-voltage ride-through control method is not used (λ=0), due to the inherent response lag of the PLL control unit in the distributed generation system, it is difficult to capture the dynamic changes in voltage. During the transient period, the three-phase voltage and phase angle output by the distributed generation system oscillate over a wide range, the PLL frequency continues to increase, and the system cannot stabilize during the transient period. Moreover, because the system continues to be out of control during the transient period, even if the grid voltage recovers at 1.6 s, the system cannot return to stable operation. When the proposed low-voltage ride-through control method is adopted (λ=10), the output three-phase voltage of the distributed generation system, as well as the phase angle and frequency of the phase-locked loop (PLL) control unit, only experience brief oscillations during the instantaneous voltage drop and recovery of the grid. Furthermore, after the grid voltage recovers in 1.6 seconds, the output three-phase voltage, output three-phase current, and phase angle of the PLL control unit of the distributed generation system can quickly recover to the system's steady-state operating point. When the proposed low-voltage ride-through control method is adopted, the peak-to-valley difference of the phase angle fluctuation in the PLL control unit of the distributed generation system is approximately 0.36 rad; the peak-to-valley difference of the frequency fluctuation is approximately 0.487 Hz. The oscillation and divergence of the phase angle and frequency of the PLL control unit during the transient period are effectively suppressed, indicating that the embodiments of the present invention can effectively enhance the transient stability of the distributed generation system, improve its low-voltage ride-through capability, and achieve stable and reliable operation of the distributed generation system.

[0059] Example 2

[0060] Embodiment 2 of the present invention provides a control system corresponding to Embodiment 1 above, including 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 of Embodiment 1 above.

[0061] 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.

[0062] 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.

[0063] Example 3

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 fault component compensation type low voltage ride-through control method for a distributed generation system, characterized in that, Includes the following steps: The three-phase output voltage and three-phase output current of the distributed generation system are sampled, and the three-phase output voltage is transformed by Park to obtain the d-axis voltage component U of the distributed generation system. d and q-axis voltage component U q By performing a Park transformation on the three-phase output current, the d-axis current component I of the distributed generation system's output current is obtained. d and q-axis current component I q ; Based on the d-axis component U of the output voltage of the distributed generation system d and the rated voltage U of the distributed generation system N The transient quadrature-axis voltage feedforward compensation component U is calculated. C ; Based on the q-axis voltage component U of the distributed generation system q and transient quadrature-axis voltage feedforward compensation component U C Calculate the current phase θ GFL ; Based on the d-axis voltage component U of the distributed generation system d q-axis voltage component u q d-axis current component I d and q-axis current component I q d-axis current reference I dn q-axis current reference I qn and current phase θ GFL Calculate the d-axis electromotive force e of the output terminal voltage of the distributed generation system. d and q-axis electromotive force e q ; The d-axis electromotive force e d and q-axis electromotive force e q Performing the inverse Park transform, the output three-phase electromotive force of the distributed generation system is obtained, based on the current phase θ. GFL and output three-phase electromotive force e abc PWM modulation is applied to the distributed generation system to obtain the switching transistor drive signal of the distributed generation system.

2. The fault component compensation type low voltage ride-through control method for distributed generation systems according to claim 1, characterized in that, Transient quadrature-axis voltage feedforward compensation component U C The calculation formula is: ； Where λ is the quadrature-axis voltage feedforward compensation coefficient.

3. The fault component compensation type low voltage ride-through control method for distributed generation systems according to claim 1, characterized in that, Current phase θ GFL The calculation formula is: ； Among them, K p and K p These are the proportional and integral coefficients of the phase-locked loop PI controller, respectively.

4. The fault component compensation type low voltage ride-through control method for distributed generation systems according to claim 1, characterized in that, d-axis electromotive force e d and q-axis electromotive force e q The calculation formula is: ； Among them, K p_i and K i_i L represents the proportional coefficient and integral coefficient of the current control, respectively. f and ω n These represent the output filter inductance value and rated angular frequency of the distributed generation system, respectively.

5. A fault component compensation type low voltage ride-through control system for a distributed generation system, comprising one or more processors and a memory; characterized in that, The memory stores one or more programs, which, when executed by the one or more processors, cause the one or more processors to perform the steps of the method according to any one of claims 1 to 4.

6. 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 according to any one of claims 1 to 4.

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