A vector power synchronization control method without phase-locked loop

Abstract

This invention proposes a phase-locked loop-free vector power synchronization control method, which achieves self-synchronization with the power grid through power synchronization control, and utilizes a cross-decoupling control structure of vector current control to achieve active and reactive power decoupling and elimination of conjugate poles. In the vector power synchronization controller used, the open-loop control part is used to maintain the stability of the system and track the reference signal, while the closed-loop control part is used to eliminate the influence of small signal disturbances in the open-loop control part.

Description

Technical Field

[0001] This invention belongs to the technical fields of vector current control and power synchronization control, and in particular relates to a vector power synchronization control method without phase-locked loop. Background Technology

[0002] With the transformation of the global energy structure, the rapid development of renewable energy and its large-scale grid integration have posed new challenges to the stability of power systems. In traditional power systems, generator synchronization with the grid is typically achieved through vector current control (VCC). VCC relies on phase-locked loops (PLLs) to track the phase information of the grid, thereby achieving precise control of active and reactive power. This method performs well in terms of stability and control performance and is widely used in power system control, especially under strong AC system conditions. However, with the widespread application of distributed energy resources, the proportion of weak grids in power systems is increasing, which places higher demands on the performance of VCC. PLLs are sensitive to fluctuations in grid frequency and phase. In weak grids, changes in grid impedance and harmonic interference can cause PLLs to fail to track accurately, leading to system oscillations or even instability. Furthermore, the traditional VCC architecture has limited flexibility and robustness when dealing with complex grid conditions, especially in scenarios with weak grids and a high proportion of renewable energy integration.

[0003] To overcome these challenges, Power Synchronous Control (PSC), as a novel grid-connected control strategy independent of PLLs, has gradually attracted attention from academia and industry. PSC avoids dependence on PLLs by directly utilizing the natural synchronization mechanism of the power grid, thereby improving the system's disturbance rejection capability and stability. However, PSC has two prominent problems: 1) There is significant coupling between active and reactive power control in PSC, which increases the complexity of controller design and debugging and may degrade system performance under certain operating conditions. 2) The PSC control loop contains two conjugate poles at the fundamental frequency, posing stability challenges when the system operates under strong AC grid conditions, especially under large external disturbances, which may lead to suboptimal dynamic response or even oscillations. Summary of the Invention

[0004] To address the problems of existing technologies, this invention proposes a phase-locked loop-free control method—Vector Power Synchronization Control (VPSC). This invention utilizes the power synchronization concept of PSC to achieve self-synchronization with the power grid. Furthermore, it employs the cross-decoupling control structure of VCC to achieve active and reactive power decoupling and the elimination of conjugate poles, thereby improving the system's stability and dynamic response performance in strong AC power grids. The proposed vector power synchronization controller design consists of two parts: 1) open-loop control; 2) closed-loop control. Open-loop control effectively maintains system stability and tracks the reference signal; closed-loop control effectively eliminates the influence of small-signal disturbances. The combination of these two components enables the proposed controller design to not only meet the requirements of a grid-connected (GFM) controller but also possess excellent dynamic performance and robustness, providing a new solution for the stable operation of future power systems.

[0005] The present invention specifically adopts the following technical solution:

[0006] A phase-locked loop-free vector power synchronization control method is proposed. It achieves self-synchronization with the power grid through power synchronization control and utilizes a cross-decoupling control structure of vector current control to achieve active and reactive power decoupling and elimination of conjugate poles. In the vector power synchronization controller used, the open-loop control part is used to maintain the stability of the system and track the reference signal, while the closed-loop control part is used to eliminate the influence of small signal disturbances in the open-loop control part.

[0007] Furthermore, by introducing a decoupling matrix C into the control system dec-vcc This eliminates the cross-coupling terms between active and reactive power, enabling independent control of active and reactive power. In the power control loop, it ensures that the active control loop only affects active power, and the reactive control loop only affects reactive power.

[0008] Furthermore, the open-loop control section adopts a network control structure, and obtains the voltage amplitude V of the converter through the power angle equation. c0 and phase θ vc0 :

[0009]

[0010] Where, q ref and p ref These are active power and reactive power references, respectively. For grid voltage V g The initial phase angle, For V c and V g The phase difference, Vc is the voltage of the voltage source converter; ω1 is the fundamental angular frequency, V g0 t represents the grid voltage amplitude, L represents the converter inductance, and t represents time.

[0011] Furthermore, the control characteristics of the closed-loop control section are as follows:

[0012]

[0013] in The controlled object in a network control system;

[0014] C p-vcc and C dec-vcc These represent the control matrix and decoupling matrix of the vector power synchronization controller, respectively. and These are the reference values ​​for the phase disturbance and amplitude disturbance of the voltage of the voltage source converter, respectively.

[0015] The loop gain is:

[0016]

[0017] Where H s (s)=k ps +k is / s is a PI controller; and The loop gains for active and reactive power control are respectively; the PI regulator parameters are designed based on the cutoff frequency and phase margin of the closed-loop gain:

[0018]

[0019] Where ω sb and PM s These are the cutoff frequency and phase margin of the VPSC, respectively.

[0020] Furthermore, active power-frequency droop control and grid voltage amplitude control are achieved through the following slow outer loop control:

[0021] set up and These are the inherent reference values ​​for active power and reactive power, respectively. and These are the additional reference values ​​generated by the outer loop; then... and New reference value for vector power controller

[0022] The active power control loop consists of a frequency detection section and an active power-frequency droop control section; the droop coefficient k fd The magnitude depends on the dynamic characteristics of the power grid; the reactive power control loop consists of an amplitude detection part implemented by Clark transformation and a voltage droop control part implemented by PI controller.

[0023] Furthermore, the loop gain of the voltage amplitude controller used is:

[0024]

[0025] In the formula L g Vg0 is the equivalent grid inductance, and Vg0 is the rated grid voltage; δ g The power angle of the grid inductance;

[0026] Voltage amplitude regulator H v The parameters of (s) are determined by the following rules:

[0027]

[0028] Where ω vb and PM v These are the cutoff frequency and phase margin for voltage amplitude control, respectively; the reference values ​​for active and reactive power should meet the apparent power constraint.

[0029]

[0030] Among them, S vpsc This represents the rated apparent power for the vector power synchronization control method.

[0031] Furthermore, a vector power synchronization control device without a phase-locked loop is provided. Based on the above control method, its control system module is a vector power synchronization controller. The open-loop control part is used to maintain the stability of the system and track the reference signal, while the closed-loop control part is used to eliminate the influence of small signal disturbances in the open-loop control part, so as to control the voltage source converter.

[0032] Furthermore, the system includes a converter module, a signal acquisition module, a data processing module, and a control system module; the converter module receives signals from the control system module to control the switching of power electronic devices and to control the amplitude v of the output voltage. cmag and phase The converter's active and reactive power outputs are adjusted; the signal acquisition module monitors electrical quantity signals, including voltage and current, in real time, and acquires the amplitude v of the grid voltage. gmag and phase The system receives the collected signal data and transmits it to the data processing module to calculate the signal, including power and frequency, and performs data conversion through Clark and Park transforms. The data processing module then transmits the processed control target reference signal to the control system module. The control system module receives the control target reference signal from the data processing module, and after processing by the controller, generates corresponding switching signals and transmits them to the converter module.

[0033] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of a phase-locked loop-free vector power synchronization control method as described above.

[0034] A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a phase-locked loop-free vector power synchronization control method as described above.

[0035] Compared with the prior art, the present invention and its preferred embodiments have at least the following outstanding advantages:

[0036] (1) Eliminate the cross-coupling terms between active and reactive power to achieve independent power control.

[0037] In traditional power control, active and reactive power are often cross-coupled. This coupling leads to the following problems: when controlling active power, reactive power may also be affected; coupling complicates control, especially making it difficult to accurately control power output during dynamic responses. The vector power synchronization control method proposed in this invention introduces a decoupling matrix C into the control system. dec-vcc This method eliminates the cross-coupling between active and reactive power, allowing them to be controlled independently. In the power control loop, it ensures that the active power control loop affects only active power, and the reactive power control loop affects only reactive power. This eliminates the uncertainty caused by the coupling between the two in traditional methods, improving the system's control accuracy and response speed, especially its stability in complex power grid environments.

[0038] (2) Eliminate the conjugate poles at the fundamental frequency to improve the robustness of the system.

[0039] In traditional VSC control strategies, conjugate poles at the fundamental frequency can easily cause system resonance and instability. The vector power synchronization control method proposed in this invention can eliminate conjugate poles, reduce system oscillations, avoid system instability caused by them, and enhance system stability under various operating conditions. Furthermore, this invention can improve the system's dynamic response capability and robustness, enabling it to maintain good operating performance even when facing dynamic loads or grid fluctuations. Attached Figure Description

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] Figure 1 This is the circuit topology diagram of a voltage source converter;

[0042] Figure 2 It is a GFM control structure;

[0043] Figure 3 This is a vector power synchronization control structure according to an embodiment of the present invention;

[0044] Figure 4 This is the equivalent vector power synchronization control loop in an embodiment of the present invention;

[0045] Figure 5 This invention relates to active power-frequency droop control and grid voltage amplitude control in embodiments of the present invention.

[0046] Figure 6 A preferred embodiment of the apparatus provided to implement the method of the present invention is shown in the structural diagram. Detailed Implementation

[0047] In the following, specific embodiments of this application will be described in detail with reference to the accompanying drawings. Based on these detailed descriptions, those skilled in the art will be able to clearly understand and implement this application. Without departing from the principles of this application, features from various embodiments can be combined to obtain new implementations, or certain features from some embodiments can be substituted to obtain other preferred implementations.

[0048] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below, along with accompanying drawings, for detailed explanation:

[0049] The purpose of this invention is to solve two significant problems in the application of power synchronization control in grid technology: 1) the coupling problem between active and reactive power; and 2) the conjugate pole problem in the control system. To address these problems, the proposed VPSC combines the advantages of vector current control and power synchronization control, presenting a novel GFM control scheme. The control scheme and controller parameter design principles of the proposed vector power synchronization control method are as follows:

[0050] This invention first analyzes the voltage source converter (VSC) topology, which consists of two parts: a physical system and a control system, such as... Figure 1 As shown, VSC is connected to the AC power grid through inductor L, and the voltage V is changed. c The output power of the VSC is controlled by its magnitude. The GFM (Grid Forming Control) associated with this invention does not rely on PLL-based grid voltage phase detection. A typical GFM control structure consists of a power calculation module and a power controller module, such as... Figure 2 As shown. The power calculation module outputs power by measuring voltage and current signals, which simultaneously contain the amplitude and phase information of the grid voltage. Therefore, the output power of the VSC can also be expressed by the power angle equation of the inductor:

[0051]

[0052] Where ω1 is the fundamental angular frequency, V g0 V represents the voltage amplitude of the power grid. cmag and These represent the initial amplitude and phase of the VSC voltage, respectively. According to the above formula, by adjusting v... cmag and The output power of the VSC can be directly controlled.

[0053] Secondly, by comparing the controlled object under GFM control and the controlled object under vector current control, in order to ensure that the network control can have similar dynamic characteristics to the vector current control, this invention proposes a novel control scheme, such as... Figure 3 As shown, it consists of two parts: 1) open-loop control and 2) closed-loop control.

[0054] The designed open-loop controller is a typical grid controller structure, which directly obtains the voltage amplitude V of the converter through the power angle equation. c0 and phase θ vc0 :

[0055]

[0056] Where, q ref and p ref These are active power and reactive power references, respectively. For grid voltage V g The initial phase angle, For V c and V g The phase difference is approximately equal to 0.

[0057] For infinitely large AC systems, open-loop control can effectively maintain system stability and track the reference signal. However, real-world power systems are not ideal, and their dynamic characteristics depend on operating conditions. This means that the amplitude and phase of the grid voltage are not fixed and may vary. Furthermore, there may be errors between the actual and theoretical values ​​of the converter inductance L, which can cause the output power of the VSC in open-loop control to deviate from the reference value. Generally, these errors are within 10%, which can be considered small-signal disturbances. Therefore, only a small-signal closed-loop controller is needed to compensate for these differences.

[0058] To compensate for the shortcomings of open-loop control, this invention proposes a method such as... Figure 3 The closed-loop control vector power synchronous controller shown has the following control characteristics:

[0059]

[0060] in The controlled object of GFM.

[0061] C p-vcc and C dec-vcc These represent the control matrix and decoupling matrix of the vector power synchronization controller, respectively. and These are the reference values ​​for the phase disturbance and amplitude disturbance of the VSC voltage, respectively. From the above equation, the equivalent vector power synchronization control loop can be obtained as follows: Figure 4 As shown, the active and reactive power control loops are decoupled, from which the loop gain can be derived as follows:

[0062]

[0063] Where H s (s)=k ps +k is / s is the PI controller. and The loop gain for active and reactive power control is determined. Then, the PI regulator parameters are designed based on the cutoff frequency and phase margin of the closed-loop gain.

[0064]

[0065] Where ω sb and PM s These are the cutoff frequency and phase margin of the VPSC, respectively.

[0066] In addition to rapid active / reactive power control, active power-frequency droop control and grid voltage amplitude control are also required in certain special cases. To achieve these requirements, a slower outer-loop control can be implemented, such as... Figure 5 As shown.

[0067] and These are the inherent reference values ​​for active power and reactive power. and This is an additional reference value generated for the outer loop. and This is the new reference value for the vector power controller (e.g.) Figure 3 ).

[0068] The active power control loop consists of a frequency detection section and an active power-frequency droop control section. The droop coefficient k... fdThe magnitude of the reactive power depends on the dynamic characteristics of the power grid. Similarly, the reactive power control loop consists of an amplitude detection section and a voltage droop control section. The former can be implemented using a Clark converter, and the latter using a PI controller. To ensure good dynamic characteristics of the outer loop controller, the voltage amplitude control bandwidth should be designed to be much lower than that of the inner loop control (generally 5% to 10% of the inner loop). Then, the actual reactive power will be very close to its reference value q within its outer loop bandwidth. ref Therefore, the loop gain of the voltage amplitude controller can be appropriately estimated:

[0069]

[0070] In the formula L g δ is the equivalent grid inductance, and Vg0 is the rated grid voltage. g The power angle of the grid inductance is typically close to 0 and can be ignored to simplify the design of the voltage amplitude controller. Then, the voltage amplitude regulator H... v The parameters of (s) can be determined by the following rules:

[0071]

[0072] Where ω vb and PM v These are the cutoff frequency and phase margin for voltage amplitude control, respectively. Generally, ω vb It can be designed to be 0.05~0.1ω sb PM v It can be set at around π / 4. Furthermore, the reference values ​​for active and reactive power should satisfy the apparent power constraint:

[0073]

[0074] Where S vpsc This is the rated apparent power of the VPSC.

[0075] The following provides a preferred device design for implementing the above scheme:

[0076] The device structure diagram of the control method proposed in this embodiment is as follows: Figure 6 As shown, it mainly consists of four parts: a converter module, a signal acquisition module, a data processing module, and a control system module. The converter module receives signals from the control system to control the switching of power electronic devices, thereby controlling the amplitude v of the output voltage. cmag and phase The converter adjusts its active and reactive power output. The signal acquisition module monitors electrical signals such as voltage and current in real time, and acquires the amplitude v of the grid voltage. gmag and phase The system receives and transmits the collected signal data to the data processing module, which calculates power, frequency, and other signals, and performs data conversion using Clark and Park transforms. The data processing module then transmits the processed control target reference signal to the control system module. The control system module receives the control target reference signal from the data processing module, processes it through the controller to generate corresponding switching signals, and transmits them to the converter module. This enables precise control of the power conversion process, thereby achieving closed-loop control of the entire system. The following is a detailed description of each part.

[0077] (1) Voltage Source Converter Module: The main function of the converter module is to convert DC power to AC power. It typically uses power electronic devices (IGBTs, etc.) for efficient power conversion. This module is the core component of the entire device and is directly responsible for the conversion and transmission of electrical energy.

[0078] (2) Signal acquisition module: The signal acquisition module is used to monitor the output signal of the voltage source converter module in real time, including parameters such as voltage and current.

[0079] (3) Data Processing Module: The main task of the data processing module is to analyze and process the raw signal data from the signal acquisition module. This includes operations such as filtering, signal transformation, and parameter calculation. The processed data will be used to generate reference signals for the control system.

[0080] (4) Control System Module: The control system module is the "brain" of the entire device, responsible for generating control signals to ensure that the voltage source converter module operates as expected. It consists of two parts: open-loop control and closed-loop control. Open-loop control can effectively maintain the stability of the system and track the reference signal; closed-loop control can effectively eliminate the influence of small signal disturbances.

[0081] The modules work together to achieve efficient conversion and control of electrical energy.

[0082] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

[0084] This patent is not limited to the above-described preferred embodiment. Anyone can derive other forms of vector power synchronization control method without phase-locked loops based on the inspiration of this patent. All equivalent changes and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A method of lock-range-free vector power synchronization control, characterized in that: The self-synchronization with the power grid is realized by power synchronization control, the active power and reactive power are decoupled and the conjugate pole is eliminated by using the cross-decoupling control structure of vector current control; in the vector power synchronization controller, the open-loop control part is used for maintaining the stability of the system and tracking the reference signal, and the closed-loop control part is used for eliminating the influence of small signal disturbance in the open-loop control part; The open-loop control part adopts a network control structure, and obtains the voltage amplitude V c0 and phase θ vc0 of the converter through a power angle equation. where q ref and p ref are active and reactive power references, respectively, is the initial phase angle of the grid voltage V g , is the phase difference between V c and V g , Vc is the voltage source converter voltage; ω1 is the fundamental angular frequency, V g0 is the grid voltage amplitude, L is the converter inductance, and t represents time. The control characteristics of the closed-loop control part are as follows: wherein a controlled object of network configuration control; C p-vcc and C dec-vcc denote the control matrix and the decoupling matrix of the vector power synchronous controller, respectively; and are the reference values of the phase disturbance and the amplitude disturbance of the voltage source converter voltage, respectively; The loop gain is: where H s (s) = k ps + k is / s is the PI regulator; and are the loop gains for active and reactive control respectively; the PI regulator parameters are designed according to the cut-off frequency and phase margin of the closed loop gain: where ω sb and PM s are the cut-off frequency and phase margin of the VPSC, respectively. The active power-frequency droop control and the grid voltage amplitude control are realized by the following slow outer loop control: Let and are the intrinsic reference values of active and reactive power, respectively, and are the additional reference values generated by the outer loop; then and are the new reference values of the vector power controller. The active power control loop consists of a frequency detection part and an active power-frequency droop control part; the droop coefficient k fd depends on the dynamic characteristics of the power grid; the reactive power control loop consists of an amplitude detection part realized by Clark transformation and a voltage droop control part realized by a PI controller; The loop gain of the voltage amplitude controller is: where L g is the equivalent grid inductance, δ g is the power angle of the grid inductance; Voltage amplitude regulator H v The parameters of (s) are determined by the following rules: where ω vb and PM v are the cut-off frequency and phase margin of the voltage magnitude control, respectively; the active and reactive power references should satisfy the apparent power constraint: where S vpsc is the rated apparent power of the vector power synchronization control method.

2. The method according to claim 1, wherein: By introducing a decoupling matrix C dec-vcc in the control system to eliminate the cross-coupling term between active power and reactive power, so that active power and reactive power are independently controlled; in the power control loop, it is ensured that the active control loop only has an impact on active power, and the reactive control loop only has an impact on reactive power.

3. A lock-range-free vector power synchronization control device, characterized by: The control method according to claim 1 or 2, wherein the control system module is a vector power synchronization controller, wherein the open-loop control part is used for maintaining the stability of the system and tracking the reference signal, and the closed-loop control part is used for eliminating the influence of small signal disturbance in the open-loop control part, so as to control the voltage source converter.

4. The loop-free vector power synchronization control device according to claim 3, characterized in that, Comprise: The converter module, the signal acquisition module, the data processing module and the control system module; the converter module receives signals from the control system module to control the switch of the power electronic device and controls the amplitude v cmag and phase of the output voltage The output of the regulating converter active and reactive power; the signal acquisition module monitors the electrical quantity signals including voltage and current in real time, acquires the amplitude v gmag and phase of the grid voltage Information, the collected signal data is transmitted to the data processing module to calculate the signals including power and frequency, and the data conversion is carried out through Clark transformation and Park transformation; the data processing module transmits the control target reference signal after calculation and processing to the control system module; the control system module receives the control target reference signal from the data processing module, generates the corresponding switch signal after the reference signal is processed by the controller, and transmits it to the converter module.

5. An electronic device comprising a memory, a processor, and a computer program stored on the memory and capable of running on the processor, characterized in that, The processor executes the program to realize the steps of the vector power synchronization control method without phase-locked loop according to claim 1 or 2.

6. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the vector power synchronization control method without phase-locked loop according to claim 1 or 2.

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