Phase-locked loop device, phase locking method of energy storage power supply and storage medium

Abstract

The invention relates to the technical field of phase locking of energy storage power supplies, in particular to a phase-locked loop device, a phase locking method of an energy storage power supply and a storage medium. The phase-locked loop device comprises a phase discriminator, a loop filter, a voltage-controlled oscillator and a compensation network module, the phase discriminator, the loop filter and the voltage-controlled oscillator output an original phase reference angle based on the input power grid voltage and the corrected phase reference angle, the compensation network module obtains a power grid power-down mark, and when the power grid power-down mark is true, the phase-locked loop device outputs the original phase reference angle. And correcting the original phase reference angle based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period to obtain a corrected phase reference angle. According to the phase-locked loop device, the compensation network is additionally arranged, compensation correction is carried out when the power grid is powered off, and the problems of output frequency hopping and phase angle deviation can be effectively solved.

Description

Technical Field

[0001] This application relates to the technical field of phase-locked technology for energy storage power supplies, and particularly to a phase-locked loop device, a phase-locking method for an energy storage power supply, and a storage medium. Background Art

[0002] With the development of society, electricity has become essential in daily life and work. However, a series of problems such as outdoor power consumption, equipment power failure, and excessive load are often encountered. Portable energy storage power supplies are one of the options to solve these problems. The waveform quality of portable energy storage power supplies is crucial, especially when supplying power to important load devices such as precision instruments, and strict requirements are imposed on the waveform quality of the output power supply.

[0003] Traditional grid software phase-locking algorithms have been widely used due to their fast response. In off-grid conditions, the inverter acts as a constant voltage source to output a stable voltage. In grid-connected conditions, the inverter exists in the system as a current source. When the grid power fails, to ensure the stability of detection, the software usually sets 3 milliseconds for power failure detection. During this 3-millisecond power failure process, rapid changes in the phase angle of the phase-locked loop will occur, resulting in problems such as output frequency jumps and phase offsets. Summary of the Invention

[0004] Embodiments of this application aim to provide a phase-locked loop device, a phase-locking method for an energy storage power supply, and a storage medium to solve the problems of output frequency jumps and phase offsets that easily occur when the energy storage power supply uses a conventional software phase-locking scheme in the event of a grid power failure in the prior art.

[0005] To solve the above technical problems, the embodiments of this application provide the following technical solutions: In a first aspect, embodiments of this application provide a phase-locked loop device, including a phase detector (PD), a loop filter (LF), a voltage-controlled oscillator (VCO), and a compensation network module. The phase detector (PD) is configured to obtain the phase error between the energy storage power supply and the grid based on the input grid voltage and the corrected phase reference angle. The loop filter (LF) is configured to process the phase error using a PI controller to obtain a first phase angle correction amount. The voltage-controlled oscillator (VCO) is configured to update the original phase reference angle in the PI controller according to the first phase angle correction amount. The compensation network module is used to obtain the power grid power-off flag and the updated original phase reference angle. When the power grid power-off flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, and the corrected phase reference angle is obtained. The value of N is the phase-locked loop operating frequency divided by the power grid rated frequency.

[0006] Optionally, the compensation network module is further used to set the corrected phase reference angle to the original phase reference angle when the power grid power-off flag is false.

[0007] Optionally, it further includes a phase angle cache module, and the phase angle cache module is used to sequentially and circularly cache the updated original phase reference angles into a preset phase angle cache area.

[0008] Optionally, the calculation formula of the corrected phase reference angle is:

[0009] Where is the corrected phase reference angle, is the second phase angle correction amount, is the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, is the original phase reference angle of the current phase-locked loop period, is the second integral constant, is the second proportionality constant.

[0010] In a second aspect, an embodiment of the present application provides a phase-locking method for an energy storage power supply, and the method includes: Obtaining the phase error between the energy storage power supply and the power grid based on the input power grid voltage and the corrected phase reference angle; Using a PI controller to process the phase error to obtain a first phase angle correction amount; Updating the original phase reference angle in the PI controller according to the first phase angle correction amount; Obtaining the power grid power-off flag and the updated original phase reference angle. When the power grid power-off flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, and the corrected phase reference angle is obtained. The value of N is the phase-locked loop operating frequency divided by the power grid rated frequency.

[0011] Optionally, after updating the original phase reference angle in the PI controller according to the first phase angle correction amount, it further includes: Sequentially and circularly caching the updated original phase reference angles into a preset phase angle cache area.

[0012] Optionally, the method further includes: When the power grid power failure flag is false, setting the corrected phase reference angle to the original phase reference angle.

[0013] Optionally, the calculation formula of the original phase reference angle is:

[0014] where, is the original phase reference angle of the current phase-locked loop period, is the original phase reference angle of the previous phase-locked loop period, is the first phase angle correction amount, is the power grid phase angle step, is the rated power grid frequency, is the phase-locked loop operating frequency.

[0015] Optionally, the calculation formula of the corrected phase reference angle is:

[0016] where, is the corrected phase reference angle, is the second phase angle correction amount, is the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, is the original phase reference angle of the current phase-locked loop period, is the second integral constant, is the second proportionality constant.

[0017] In a third aspect, an embodiment of the present application provides a computer storage medium, which stores instructions or programs. When the instructions or programs are executed by at least one processor, the at least one processor is caused to execute the method described in any one of the above.

[0018] The beneficial effects of the embodiments of the present application are as follows: Different from the prior art, in the embodiments of the present application, a phase-locked loop device is provided, including a phase discriminator, a loop filter, a voltage-controlled oscillator and a compensation network module. The phase discriminator, the loop filter and the voltage-controlled oscillator output an original phase reference angle based on the input grid voltage and the corrected phase reference angle. The compensation network module is used to obtain a power grid power failure flag. When the power grid power failure flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, and a corrected phase reference angle is obtained. The phase-locked loop device of the present application can effectively solve the problems of output frequency jump and phase angle offset by adding a compensation network for compensation and correction when the power grid loses power. Description of the Drawings

[0019] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the drawings in the figures do not constitute a scale limitation.

[0020] Figure 1a is a schematic structural diagram of a conventional phase-locked loop device; Figure 1b is Figure 1a the expanded model of the phase-locked loop device in; Figure 2 is a schematic structural diagram of the phase-locked loop device provided by the embodiment of the present application; Figure 3 is a schematic flowchart of a phase-locking method provided by the embodiment of the present application; Figure 4 is a schematic diagram of the inverter output phase angle and waveform during normal grid operation and grid power failure. Detailed Embodiments

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0022] In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0023] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0024] Please refer to Figure 1a and Figure 1b , Figure 1a is a schematic structural diagram of a conventional phase-locked loop device, Figure 1b is Figure 1a the expanded model of the phase-locked loop device in. As Figure 1a and Figure 1bAs shown, the phase-locked loop device 100 includes a phase detector (PD) 101, a loop filter (LF) 102, and a voltage-controlled oscillator (VCO) 103. Among them, the PD detects the phase difference between the grid voltage and the VCO output signal and generates an error voltage; the LF filters out high-frequency noise and optimizes the loop dynamic response; the VCO adjusts the output frequency according to the filtered error signal, and finally makes the inverter angular frequency ω and phase angle θ synchronized with the grid. The input of the phase-locked loop device 100 is the grid voltage, and the output is the synchronized angular frequency and phase angle.

[0025] When the grid power fails, the control program executes the grid-connected to off-grid switching. Due to the inherent time of power failure detection, within this time, the grid voltage is unstable, resulting in a deviation of the phase angle of the phase-locked loop. When switching to off-grid, frequency jump and phase shift problems are formed. To address the output frequency jump and phase shift problems, this application adds a compensation network module to the conventional phase-locked loop device. The compensation network module corrects the phase shift after the grid power failure, making it return to the normal phase.

[0026] Please refer to Figure 2 , Figure 2 which is the structural schematic diagram of the phase-locked loop device provided by the embodiment of this application. As Figure 2 shown, the phase-locked loop device 100 includes a phase detector (PD) 101, a loop filter (LF) 102, a voltage-controlled oscillator (VCO) 103, and a compensation network module 104. Among them: PD101 is used to obtain the phase error between the energy storage power supply and the grid based on the input grid voltage and the corrected phase reference angle.

[0027] Specifically, PD101 first performs orthogonal decomposition on the input grid voltage to generate a set of orthogonal signals. Among them, for a single-phase grid voltage, the grid voltage can be input into an orthogonal generator to generate a set of orthogonal signals. This orthogonal generator is preferably a second-order generalized integrator. For a three-phase grid voltage, the grid voltage can be subjected to Clarke transformation to generate a set of orthogonal signals. The calculation formula of Clarke transformation is:

[0028] Among them, , and are the three-phase grid voltages collected, and are the generated orthogonal signals.

[0029] Secondly, PD101 performs phase difference detection based on the orthogonal signals and the corrected phase reference angle to obtain the phase error between the energy storage power supply and the grid. In the initial state, the corrected phase reference angle and the original phase reference angle are preset to be the same.

[0030] In one embodiment, the Park transformation is performed based on the orthogonal signal and the corrected phase reference angle to obtain the d-axis component voltage and the q-axis component voltage. When there is a deviation between the corrected phase reference angle and the grid phase angle, the q-axis component voltage is not zero, and the q-axis component voltage is used as the phase error between the energy storage system and the grid. Specifically, the calculation formula of the Park transformation is:

[0031] Where, is the d-axis component voltage, is the q-axis component voltage.

[0032] In other embodiments, first, the grid phase angle is calculated based on the orthogonal signal using the arctangent formula, and then the difference between the grid phase angle and the corrected phase reference angle is used as the phase error between the energy storage system and the grid. Specifically, the calculation formula of the grid phase angle is:

[0033] The calculation formula of the phase error is:

[0034] Where, is the grid phase angle, is the phase error, is the corrected phase reference angle.

[0035] LF102 is used to process the phase error using a PI controller to obtain the first phase angle correction amount, and the calculation formula of the first phase angle correction amount is:

[0036] Where, is the first phase angle correction amount, is the phase error, is the first integral constant, is the first proportional constant.

[0037] VCO103 is used to update the original phase reference angle in the PI controller according to the first phase angle correction amount.

[0038] Specifically, the original phase reference angle is updated according to the first phase angle correction amount obtained by LF102 and the grid phase angle change step, and the calculation formula of the original phase reference angle is:

[0039] Where, is the original phase reference angle of the current PLL cycle, is the original phase reference angle of the previous PLL cycle, is the first phase angle correction amount, is the phase angle step of the power grid, is the rated frequency of the power grid, is the operating frequency of the phase-locked loop. For example, the rated frequency of the power grid is 50Hz, and the operating frequency of the phase-locked loop is 10KHz.

[0040] The compensation network module 104 is used to obtain the power grid power-off flag and the updated original phase reference angle. When the power grid power-off flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period to obtain the corrected phase reference angle; when the power grid power-off flag is false, the corrected phase reference angle is set to the original phase reference angle. Wherein, the value of N is the operating frequency of the phase-locked loop divided by the rated frequency of the power grid.

[0041] Specifically, first calculate the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, then use a PI controller to process the difference to obtain a second phase angle correction amount. Finally, the original phase reference angle is corrected based on the second phase angle correction amount to obtain the corrected phase reference angle. Wherein, the calculation formula for the corrected phase reference angle is:

[0042] Wherein, is the corrected phase reference angle, is the second phase angle correction amount, is the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, is the original phase reference angle of the current phase-locked loop period, is the second integral constant, is the second proportionality constant.

[0043] In one embodiment, the phase-locked loop device 100 further includes a phase angle cache module (not shown in the figure), and this phase angle cache module is used to circularly cache the updated original phase reference angle into a preset phase angle cache area in sequence. Wherein, the size of the phase angle storage area is determined according to the power-off detection duration. As described above, one power grid voltage cycle contains N phase-locked loop periods, that is, one power grid voltage cycle corresponds to N original phase reference angles, then the size of the phase angle storage area can be set to N M, wherein, M = For example, the rated frequency of the power grid is 50Hz (the period is 20ms), and the power-off detection duration is 3ms, then the size of the phase angle storage area can be set to 20. Through the circular caching technology, the original phase reference angles output in the recent N phase-locked loop periods can be stored in the phase angle cache area.

[0044] Please refer to Figure 3 , Figure 3It is a schematic flowchart of a phase-locking method for an energy storage power supply provided by an embodiment of the present application. Among them, the energy storage power supply includes a phase-locked loop device, and this phase-locked loop device can be implemented through the Figure 2 structure shown. The specific implementation process has been described in detail in the above embodiment and will not be elaborated here.

[0045] As Figure 3 shown, the phase-locking method for the energy storage power supply includes: Step S301, obtaining the phase error between the energy storage power supply and the power grid based on the input grid voltage and the corrected phase reference angle.

[0046] Specifically, the energy storage power supply samples the grid voltage, inputs the sampled grid voltage into the phase-locked loop device, and initializes the corrected phase reference angle and the original phase reference angle of the phase-locked loop device. The phase-locked loop device first performs orthogonal decomposition on the input grid voltage to generate a set of orthogonal signals; then, based on the orthogonal signals and the corrected phase reference angle, it performs phase difference detection to obtain the phase error between the energy storage power supply and the power grid.

[0047] Step S302, using a PI controller to process the phase error to obtain a first phase angle correction amount.

[0048] In one embodiment, the calculation formula for the first phase angle correction amount is:

[0049] Among them, is the first phase angle correction amount, is the phase error, is the first integral constant, is the first proportional constant.

[0050] Step S303, updating the original phase reference angle in the PI controller according to the first phase angle correction amount.

[0051] Specifically, the original phase reference angle is updated according to the first phase angle correction amount and the grid phase angle change step. The calculation formula for the original phase reference angle is:

[0052] Among them, is the original phase reference angle of the current phase-locked loop period, is the original phase reference angle of the previous phase-locked loop period, is the first phase angle correction amount, is the grid phase angle step, is the grid rated frequency, is the phase-locked loop operating frequency.

[0053] Step S304: Obtain the power grid power failure flag and the updated original phase reference angle. When the power grid power failure flag is true, correct the original phase reference angle based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth PLL cycle before the current PLL cycle, to obtain the corrected phase reference angle, where the value of N is the operating frequency of the PLL divided by the rated frequency of the power grid.

[0054] In an embodiment, by detecting the output waveform of the energy storage power supply in real time, it is determined whether the power grid has a power failure. When the power grid power failure flag is true, first calculate the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth PLL cycle before the current PLL cycle, then use a PI controller to process this difference to obtain the second phase angle correction amount. Finally, correct the original phase reference angle based on the second phase angle correction amount to obtain the corrected phase reference angle. Among them, the calculation formula for the corrected phase reference angle is:

[0055] Among them, is the corrected phase reference angle, is the second phase angle correction amount, is the original phase reference angle corresponding to the Nth PLL cycle before the current PLL cycle, is the original phase reference angle of the current PLL cycle, is the second integral constant, is the second proportionality constant.

[0056] When the power grid power failure flag is false, set the second phase angle correction amount to 0, that is, set the corrected phase reference angle to the original phase reference angle.

[0057] In an embodiment, after step S303, it further includes: circularly cache the updated original phase reference angle into a preset phase angle buffer in sequence. Among them, the size of the phase angle storage area is determined according to the power failure detection duration. As mentioned above, one power grid voltage cycle contains N PLL cycles, that is, one power grid voltage cycle corresponds to N original phase reference angles, then the size of the phase angle storage area can be set to N M, where M = . For example, if the rated frequency of the power grid is 50 Hz (the period is 20 ms) and the power failure detection duration is 3 ms, the size of the phase angle storage area can be set to 20. Through the circular caching technology, the original phase reference angles output in the recent N PLL cycles can be stored in the phase angle buffer.

[0058] Please refer to Figure 4, where (a) is a schematic diagram of the inverter output phase angle and waveform when the power grid is normal, (b) is a schematic diagram of the inverter output phase angle and waveform obtained based on a conventional phase-locked loop device when the power grid loses power, and (c) is a schematic diagram of the inverter output phase angle and waveform obtained based on the phase-locked loop device of the present application when the power grid loses power.

[0059] As Figure 4 shown, the red waveform is the output voltage, and the green waveform is the output phase angle. When the power grid is normal, the output voltage is the grid voltage. When the power grid is abnormal, the output voltage is the inverter voltage. The duration between two wave peaks is the period of the output voltage. From Figure 4 (b), it can be seen that when the power grid loses power, the voltage drops instantaneously, and the slope of the output phase angle changes, with a very small slope. When the power grid loss is recognized after 3 ms, the inverter switches to the off-grid state, and the output phase angle is output according to the off-grid phase angle, and the slope returns to the normal value, but at this time, a frequency jump occurs, jumping from 50 Hz to 43 Hz, and the output phase angle also shows an offset. From Figure 4 (c), it can be seen that when the power grid loses power and switches to the off-grid state, the output phase angle corrects the phase angle slope through the compensation network, and the slope becomes larger. After a short correction, the normal phase angle can be restored. After correction, the output phase angle is Figure 4 completely consistent with (a), avoiding the problems of frequency hopping and phase shift.

[0060] The phase-locked loop device provided by the present application includes a phase discriminator, a loop filter, a voltage-controlled oscillator, and a compensation network module. The phase discriminator, the loop filter, and the voltage-controlled oscillator output an original phase reference angle based on the input grid voltage and the corrected phase reference angle. The compensation network module is used to obtain a power grid power loss flag. When the power grid power loss flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, and a corrected phase reference angle is obtained. The phase-locked loop device of the present application can effectively solve the problems of output frequency hopping and phase angle offset by adding a compensation network for compensation and correction when the power grid loses power.

[0061] The embodiment of the present application also provides a computer storage medium. The computer storage medium stores instructions or programs, and when the instructions or programs are executed by one or more processors, the above one or more processors can execute the phase-locking method of the energy storage power supply in any of the above method embodiments.

[0062] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution or the part that contributes to the related technology can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0063] As described above, the above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A phase-locked loop device, characterized in that, It includes a phase detector, a loop filter, a voltage-controlled oscillator, and a compensation network module. The phase detector is configured to obtain the phase error between the energy storage power supply and the power grid based on the input grid voltage and the corrected phase reference angle. The loop filter is configured to process the phase error by using a PI controller to obtain a first phase angle correction amount. The voltage-controlled oscillator is configured to update the original phase reference angle in the PI controller according to the first phase angle correction amount. The compensation network module is configured to obtain a power grid power-off flag and the updated original phase reference angle. When the power grid power-off flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period to obtain the corrected phase reference angle, where the value of N is the phase-locked loop operating frequency divided by the grid rated frequency.

2. The device according to claim 1, characterized in that The compensation network module is further configured to set the corrected phase reference angle to the original phase reference angle when the power grid power-off flag is false.

3. The device according to claim 1, characterized in that, It further includes a phase angle cache module, and the phase angle cache module is configured to sequentially and circularly cache the updated original phase reference angle into a preset phase angle cache area.

4. The device according to any one of claims 1 to 3, characterized in that The calculation formula for the corrected phase reference angle is: Wherein, is the corrected phase reference angle, is the second phase angle correction amount, is the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, is the original phase reference angle of the current phase-locked loop period, is the second integral constant, is the second proportionality constant.

5. A phase-locking method for an energy storage power supply, characterized in that, The method includes: Obtaining the phase error between the energy storage power supply and the power grid based on the input grid voltage and the corrected phase reference angle. Processing the phase error by using a PI controller to obtain a first phase angle correction amount. Updating the original phase reference angle in the PI controller according to the first phase angle correction amount. Obtaining a power grid power-off flag and the updated original phase reference angle. When the power grid power-off flag is true, the original phase reference angle is corrected based on the difference between the original phase reference angle and the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period to obtain the corrected phase reference angle, where the value of N is the phase-locked loop operating frequency divided by the grid rated frequency.

6. The method according to claim 5, wherein After updating the original phase reference angle in the PI controller according to the first phase angle correction amount, it further includes: Sequentially and circularly caching the updated original phase reference angle into a preset phase angle cache area.

7. The method according to claim 5, wherein The method further includes: Setting the corrected phase reference angle to the original phase reference angle when the power grid power-off flag is false.

8. The method according to claim 5, characterized in that The calculation formula for the original phase reference angle is: Wherein, is the original phase reference angle of the current PLL cycle, is the original phase reference angle of the previous PLL cycle, is the first phase angle correction amount, is the grid phase angle step, is the grid rated frequency, is the PLL operating frequency.

9. The method according to any one of claims 5 to 8, characterized in that, The calculation formula for the corrected phase reference angle is: Among them, is the corrected phase reference angle, is the second phase angle correction amount, is the original phase reference angle corresponding to the Nth phase-locked loop period before the current phase-locked loop period, is the original phase reference angle of the current phase-locked loop period, is the second integral constant, is the second proportionality constant.

10. A computer storage medium, characterized in that, The computer storage medium stores instructions or programs, and when the instructions or programs are executed by at least one processor, the at least one processor is caused to execute the method according to any one of claims 5 to 9.

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