A photovoltaic energy storage control system for damping power grid oscillations under frequency disturbances

Abstract

The application discloses a kind of photovoltaic energy storage control systems for inhibiting power grid oscillation under frequency disturbance, belong to photovoltaic energy storage power generation field.The present application includes photovoltaic half-wave damping controller and energy storage full-wave damping controller, photovoltaic half-wave damping controller is used to collect power grid frequency, through a proportional amplifier, high pass filter and phase compensator after forming photovoltaic active power compensation signal, simultaneously photovoltaic active power compensation signal is delivered to photovoltaic active controller;Energy storage full-wave damping controller is used to collect power grid frequency in real time, also through, through a proportional amplifier, high pass filter and phase compensator after forming energy storage active power compensation signal, simultaneously energy storage active power compensation signal is delivered to energy storage active controller.The present application can effectively inhibit the low-frequency oscillation of power system under frequency disturbance excitation, enhance the small signal stability of power system.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic energy storage power generation, and more specifically, relates to a photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances. Background Technology

[0002] Low-frequency oscillations in power systems are low-frequency oscillations caused by the relative swaying of generator rotors, resulting in approximately equal or increasing amplitudes in certain electrical quantities. Their frequency range is generally 0.1-2.5 Hz. These low-frequency oscillations significantly impact the safety and stability of power systems, directly or indirectly causing inconvenience to daily life and production, thus becoming a hot research topic for many scholars. Based on the different generating units involved, low-frequency oscillations can be divided into local oscillations and regional oscillations: Local oscillations refer to oscillations occurring between generators in the same area or power plant. Due to the small number of synchronous generators involved, the corresponding oscillation frequency is relatively high, generally above 0.7 Hz. Regional oscillations refer to oscillations between generator groups in two areas, with the oscillation power propagating to the entire system through tie lines. Due to the larger number of participating generating units, the frequency of regional oscillations is lower, generally 0.1-0.7 Hz. Relatively speaking, regional oscillations are more harmful.

[0003] Currently, the most common method to suppress low-frequency oscillations in power systems is to install power system stabilizers in the excitation system. Although power system stabilizers are effective in suppressing low-frequency oscillations, they still have some limitations. For example, the parameter design of power system stabilizers needs to be coordinated with each other and adapted to the oscillation mode of the system in order to effectively suppress low-frequency oscillations. If high-frequency local oscillations or interval oscillations involving many units occur, a small number of power system stabilizers will not be able to suppress the oscillations. On the contrary, they may even lead to a deterioration of the system operating environment. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances. Its purpose is to suppress low-frequency oscillations of the power system in the frequency range of 0.1 to 2.5 Hz, so as to improve system damping and enhance the stability of power system operation.

[0005] To achieve the above objectives, the present invention provides a photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances, comprising: a photovoltaic / energy storage damping controller, a control system, and a photovoltaic grid-connected controller;

[0006] The photovoltaic / energy storage damping controller includes a photovoltaic half-wave damping controller, an energy storage full-wave damping controller, and a working mode selector; the control system includes a photovoltaic active power controller, an energy storage active power controller, and a drive signal generator.

[0007] The photovoltaic half-wave damping controller is used to obtain the compensation signal for photovoltaic active power based on the collected grid frequency;

[0008] The energy storage full-wave damping controller is used to obtain the compensation signal of the energy storage active power based on the collected grid frequency;

[0009] The operating mode selector receives the compensation signal of photovoltaic active power and the compensation signal of energy storage active power, selects the corresponding operating mode accordingly, and outputs the final compensation signal.

[0010] The photovoltaic active power controller collects the power signal of the photovoltaic power station and combines it with the photovoltaic active power compensation signal output by the photovoltaic / energy storage damping controller. It then generates the corresponding photovoltaic active power controller modulation signal through power decoupling control and proportional-integral (PI) control.

[0011] The energy storage active power controller collects the power signal of the energy storage system and combines it with the energy storage active power compensation signal output by the photovoltaic / energy storage damping controller. It then generates the corresponding energy storage active power controller modulation signal through power decoupling control and proportional-integral (PI) control.

[0012] The drive signal generator is used to receive the modulation signals output by the photovoltaic active power controller and the energy storage active power controller, obtain the PWM drive signal through PWM control, and send the PWM drive signal to the corresponding grid-connected inverter.

[0013] A photovoltaic grid-connected controller is used to control the waveform, frequency, and power of the grid-connected current, so that the power delivered by the photovoltaic power station to the public grid is its maximum operating power.

[0014] Furthermore, the photovoltaic half-wave damping controller includes a dead-zone detector, a proportional regulator, a high-pass filter, a phase compensation regulator, and a limiter;

[0015] The dead-time detector determines the grid frequency and outputs the grid frequency corresponding to a specific time period.

[0016] A proportional regulator is used to acquire the power grid frequency corresponding to a specific time period in real time, and to obtain a conditioning signal by calculation and amplification based on the acquired value;

[0017] A high-pass filter is used to detect the frequency signal of low-frequency oscillations in a conditioned signal;

[0018] A phase compensation regulator is used to adjust and process the phase of a low-frequency oscillation signal to obtain an initial photovoltaic active power compensation signal.

[0019] A limiter is used to limit the initial photovoltaic active power compensation signal before outputting the photovoltaic active power compensation signal.

[0020] Furthermore, the compensation signal P1 for photovoltaic active power is:

[0021] or

[0022] f is the system frequency, Δf is the system frequency change, k1 is the proportional amplifier parameter, k2 and k3 are the high-pass filter parameters, s is the microoperator, and f N This indicates a rated grid frequency of 50Hz.

[0023] Furthermore, the photovoltaic active power compensation signal is greater than 0 and less than 10% of the photovoltaic capacity itself.

[0024] Furthermore, the energy storage full-wave damping controller includes a dead-zone detector, a proportional regulator, a high-pass filter, a phase compensation regulator, and a limiter;

[0025] The dead-time detector is used to determine the grid frequency f and then output the grid frequency corresponding to a specific time period.

[0026] A proportional regulator is used to acquire the power grid frequency corresponding to a specific time period in real time, and to obtain a conditioning signal by calculation and amplification based on the acquired value;

[0027] A high-pass filter is used to detect the frequency signal of low-frequency oscillations in a conditioning signal;

[0028] The phase compensation regulator is used to adjust and process the phase of the low-frequency oscillation signal to obtain the initial energy storage active power compensation signal.

[0029] A limiter is used to limit the initial energy storage active power compensation signal before outputting the energy storage active power compensation signal.

[0030] Furthermore, the compensation signal P2 for the active power of energy storage is:

[0031] or

[0032] Where f is the system frequency, Δf is the system frequency change, k4 is the proportional amplifier parameter, k5 and k6 are the high-pass filter parameters, s is the micro-operator, and f N This indicates a rated grid frequency of 50Hz.

[0033] Furthermore, the active power compensation signal for energy storage is within ±10% of the energy storage capacity.

[0034] Furthermore, the operating mode selector receives the compensation signals for photovoltaic active power and energy storage active power, and outputs four operating modes according to system requirements: Mode 1: When both the photovoltaic and energy storage active power compensation signals are 0, no damping controller is added; Mode 2: When the energy storage active power compensation signal is 0, a photovoltaic half-wave damping controller is added, and the photovoltaic active power compensation signal is output according to the actual output; Mode 3: When the photovoltaic active power compensation signal is 0, an energy storage full-wave damping controller is added, and the energy storage active power compensation signal is output according to the actual output; Mode 4: When both the photovoltaic and energy storage active power compensation signals are greater than 0, both a photovoltaic half-wave damping controller and an energy storage full-wave damping controller are added, and both the photovoltaic and energy storage active power compensation signals are output according to the actual output.

[0035] Overall, the above-described technical solutions conceived by this invention can achieve the following beneficial effects compared with the prior art.

[0036] This invention proposes a photovoltaic energy storage control system. Utilizing the active power modulation capability of photovoltaic / energy storage, it adjusts its output by real-time monitoring of system frequency changes, thereby increasing the damping ratio of the power system. In practical applications, the output of the photovoltaic system is significantly affected by ambient light; in the absence of sunlight, the energy storage system can adjust its output to suppress frequency oscillations. The energy storage system is small in size, has low requirements for installation location and environment, is unaffected by oscillation modes, and exhibits minimal voltage fluctuations when the energy storage battery's state of charge is between 20% and 80%. Therefore, the system has strong anti-interference capabilities, can output power rapidly, effectively suppress low-frequency oscillations, and improve the small-disturbance stability of the power system. Attached Figure Description

[0037] Figure 1 This is a topology diagram of a photovoltaic / energy storage grid-connected system in a specific embodiment of the present invention;

[0038] Figure 2 This is a block diagram of the control structure of the photovoltaic / energy storage grid-connected system in a specific embodiment of the present invention;

[0039] Figure 3 This is a structural block diagram of the damping controller in a specific embodiment of the present invention;

[0040] Figure 4 This is a structural block diagram of the photovoltaic half-wave damping controller in a specific embodiment of the present invention;

[0041] Figure 5 This is a structural block diagram of the energy storage full-wave damping controller in a specific embodiment of the present invention;

[0042] Figure 6 This is a structural block diagram of the working mode selector in a specific embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] Figure 1 This is a structural diagram of a photovoltaic (PV) energy storage grid-connected system, consisting of PV panels (1), a DC / DC converter (2), a PV grid-connected controller (3), a power grid (7), a PV / energy storage damping controller (8), a control system (9), an energy storage battery (10), an energy storage grid-connected inverter (11), and filter inductors (4, 12), and line impedances (5, 6, 13). The DC / DC converter (2) controls the PV power station's maximum power point tracking (MPPT). The PV grid-connected controller (3) controls the waveform, frequency, and power of the grid-connected current, ensuring that the power delivered by the PV power station to the public grid is its maximum operating power. The energy storage battery (10) outputs DC voltage, which is converted to AC power by the energy storage grid-connected inverter (11) for grid connection. The PV / energy storage damping controller (8) receives the grid frequency f and outputs an active power compensation signal to the control system, enabling the PV-energy storage system to suppress low-frequency grid oscillations. The control system (9) receives the active power from the PV / energy storage system and, combined with the active power compensation signal output from the PV / energy storage damping controller, outputs a drive signal to drive the PV grid-connected controller (3) and the energy storage grid-connected inverter (11).

[0045] like Figure 2 As shown, the connection relationship between the photovoltaic / energy storage damping controller 8 and the control system 9 can be obtained. The control system 9 includes a photovoltaic active power controller 92, an energy storage active power controller 93, and a drive signal generator 94.

[0046] The photovoltaic / energy storage damping controller 8 receives the grid frequency f and outputs the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1 to the control system 9, so that the photovoltaic-energy storage system can suppress low-frequency oscillations of the grid.

[0047] In the photovoltaic active power controller 92, the photovoltaic power station power signal 92.1 is acquired and combined with the photovoltaic active power compensation signal 81.1 output by the photovoltaic / energy storage damping controller. The output d-axis current reference signal i is obtained through power decoupling control. d1 According to this current reference signal i d1 The photovoltaic active power controller modulation signal 92.2 is determined by proportional-integral (PI) control and then sent to the drive signal generator 94.

[0048] In the energy storage active power controller 93, the energy storage active power signal 93.1 is acquired and combined with the energy storage active power compensation signal 82.1 output by the photovoltaic / energy storage damping controller. The output d-axis current reference signal i is obtained through power decoupling control. d2 According to this current reference signal i d2 The modulated signal 93.2 of the energy storage active power controller is determined by proportional-integral (PI) control, and the modulated signal 93.2 of the energy storage active power controller is sent to the drive signal generator 94.

[0049] Subsequently, the drive signal generator 94 receives the modulation signals 92.2 and 93.2 from the photovoltaic / energy storage active power controller to obtain drive signals 901 and 902. Drive signal 901 is sent to the photovoltaic grid-connected controller 3, and drive signal 902 is sent to the energy storage grid-connected inverter 11.

[0050] like Figure 3 As shown, the photovoltaic / energy storage damping controller 8 includes a photovoltaic half-wave damping controller 81, an energy storage full-wave damping controller 82, and a working mode selector 83.

[0051] The photovoltaic half-wave damping controller 81 is used to acquire the grid frequency f. After passing through a proportional regulator, a high-pass filter, and a phase compensation regulator, the calculated compensation signal P1 for the photovoltaic active power is:

[0052]

[0053] Where f is the system frequency, Δf is the system frequency change, k1 is the proportional amplifier parameter, k2 and k3 are the high-pass filter parameters, and s is the micro-operator. Based on this compensation signal P1, a photovoltaic active power compensation signal 81.1 is formed, and the photovoltaic active power compensation signal 81.1 is simultaneously sent to the working mode selector 83.

[0054] The energy storage full-wave damping controller 82 is used to acquire the grid frequency f. After passing through a proportional regulator, a high-pass filter, and a phase compensation regulator, the calculated compensation signal P2 for the energy storage active power is:

[0055]

[0056] Where f is the system frequency, Δf is the system frequency change, k4 is the proportional amplifier parameter, k5 and k6 are the high-pass filter parameters, and s is the micro-operator. Based on this compensation signal P2, the energy storage active power compensation signal 82.1 is formed, and the energy storage active power compensation signal 82.1 is sent to the working mode selector 83.

[0057] The operating mode selector 83 receives the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1 and selects the corresponding operating mode accordingly. After processing the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1, they are respectively sent to the photovoltaic active power controller 92 and the energy storage active power controller 93.

[0058] like Figure 4 As shown, the photovoltaic half-wave damping controller 81 includes a dead zone detector 810, a proportional regulator 811, a high-pass filter 812, a phase compensation regulator 813, and a limiter 814.

[0059] The grid frequency f is determined by the dead-zone detector 810 and outputs the grid frequency 810.1 corresponding to a specific time period. The proportional regulator 811 is used to collect the grid frequency 810.1 in real time, and calculates and amplifies the collected value to obtain the conditioning signal 811.1, which is then output to the high-pass filter 812. The high-pass filter 812 is used to receive the conditioning signal 811.1 and detect the low-frequency oscillation frequency signal 812.1 in it, and then outputs this frequency signal 812.1 to the phase compensation regulator 813. The phase compensation regulator 813 is used to receive the low-frequency oscillation frequency signal 812.1, and adjusts and processes its phase to obtain the initial photovoltaic active power compensation signal 813.1, which is then sent to the limiter 814. The limiter 814 receives the initial photovoltaic active power compensation signal 813.1, limits it, and then outputs the photovoltaic active power compensation signal 81.1.

[0060] The high-pass filter 812 is used to isolate the DC link, ensuring that the compensation control only functions during dynamic processes. The filter time constant is selected to ensure sufficient attenuation of DC and ultra-low frequency band signals without affecting the low-frequency oscillation band signal. The filter time constant ranges from 0.5 to 1 second. The phase compensator 813 is used to modulate the phase shift of the entire damping control loop at the low-frequency oscillation frequency to ensure that the damping control loop provides a positive damping effect. The limiter 814 is used to limit the photovoltaic active power compensation signal 81.1 from being greater than 0 to being less than 10% of the photovoltaic's own capacity.

[0061] like Figure 5 As shown, the energy storage full-wave damping controller 82 includes a dead zone detector 820, a proportional regulator 821, a high-pass filter 822, a phase compensation regulator 823, and a limiter 824.

[0062] The dead-zone detector is used to acquire the grid frequency and determine whether the grid frequency is outside the dead zone. If the determination is yes, the damping controller is not activated; otherwise, it is activated and the input grid frequency is output to the proportional controller. The grid frequency f is output by the dead-zone detector for a specific time period. The dead zone range is ±0.05Hz, meaning the grid frequency fluctuation is greater than 0.05Hz. The advantage of the dead zone is that it avoids frequent controller operation; it can be deactivated when the grid frequency change is small, and activated when the change is large.

[0063] The grid frequency f is determined by the dead-zone detector 820, which outputs the grid frequency 820.1 corresponding to a specific time period. The proportional regulator 821 is used to collect the grid frequency 820.1 in real time, and calculates and amplifies the collected value to obtain the conditioning signal 821.1, which is then output to the high-pass filter 822. The high-pass filter is used to receive the conditioning signal 821.1, detect the low-frequency oscillation frequency signal 822.1 in it, and output this frequency signal 822.1 to the phase compensation regulator 823. The phase compensation regulator 823 is used to receive the low-frequency oscillation frequency signal 822.1, and adjust and process its phase to obtain the initial energy storage active power compensation signal 823.1, which is then sent to the limiter 824. The limiter 824 receives the initial energy storage active power compensation signal 823.1, limits it, and outputs the energy storage active power compensation signal 82.1.

[0064] The high-pass filter 822 is used to isolate the DC link, ensuring that the compensation control only functions during dynamic processes. The filter time constant is selected to ensure sufficient attenuation of DC and ultra-low frequency band signals without affecting the low-frequency oscillation band signal. The filter time constant range is 0.5–1s. The phase compensator 823 is used to modulate the phase shift of the entire damping control loop at the low-frequency oscillation frequency to ensure that the damping control loop provides a positive damping effect. The limiter 824 is used to limit the energy storage active power compensation signal 82.1 to within ±10% of the energy storage capacity.

[0065] like Figure 6As shown, the operating mode selector 83 receives the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1, and outputs four operating modes according to system requirements: Mode 1: When both the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1 are 0, no damping controller is added; Mode 2: When the energy storage active power compensation signal 82.1 is 0, a photovoltaic half-wave damping controller is added, and the photovoltaic active power compensation signal 81.1 is output according to the actual output; Mode 3: When the photovoltaic active power compensation signal 81.1 is 0, an energy storage full-wave damping controller is added, and the energy storage active power compensation signal 82.1 is output according to the actual output; Mode 4: When both the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1 are greater than 0, a photovoltaic half-wave damping controller and an energy storage full-wave damping controller are added, and both the photovoltaic active power compensation signal 81.1 and the energy storage active power compensation signal 82.1 are output according to the actual output.

[0066] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances, characterized in that, include: Photovoltaic / energy storage damping controllers, control systems, and photovoltaic grid-connected controllers; The photovoltaic / energy storage damping controller includes a photovoltaic half-wave damping controller, an energy storage full-wave damping controller, and a working mode selector; the control system includes a photovoltaic active power controller, an energy storage active power controller, and a drive signal generator. The photovoltaic half-wave damping controller is used to obtain the compensation signal for photovoltaic active power based on the collected grid frequency; The energy storage full-wave damping controller is used to obtain the compensation signal of the energy storage active power based on the collected grid frequency; The operating mode selector receives the compensation signals for both photovoltaic (PV) and energy storage active power and selects the corresponding operating mode accordingly, outputting the final compensation signal. The operating mode selector receives the compensation signals for both PV and energy storage active power and outputs four operating modes based on system requirements: Mode 1: When both PV and energy storage active power compensation signals are 0, no damping controller is applied; Mode 2: When the energy storage active power compensation signal is 0, a PV half-wave damping controller is applied, and the PV active power compensation signal is output according to the actual output; Mode 3: When the PV active power compensation signal is 0, a energy storage full-wave damping controller is applied, and the energy storage active power compensation signal is output according to the actual output; Mode 4: When both PV and energy storage active power compensation signals are greater than 0, both a PV half-wave damping controller and an energy storage full-wave damping controller are applied, and both PV and energy storage active power compensation signals are output according to the actual output. The photovoltaic active power controller collects the power signal of the photovoltaic power station and combines it with the photovoltaic active power compensation signal output by the photovoltaic / energy storage damping controller. It then generates the corresponding photovoltaic active power controller modulation signal through power decoupling control and proportional-integral (PI) control. The energy storage active power controller collects the power signal of the energy storage system and combines it with the energy storage active power compensation signal output by the photovoltaic / energy storage damping controller. It then generates the corresponding energy storage active power controller modulation signal through power decoupling control and proportional-integral (PI) control. The drive signal generator is used to receive the modulation signals output by the photovoltaic active power controller and the energy storage active power controller, obtain the PWM drive signal through PWM control, and send the PWM drive signal to the corresponding grid-connected inverter. A photovoltaic grid-connected controller is used to control the waveform, frequency, and power of the grid-connected current, so that the power delivered by the photovoltaic power station to the public grid is its maximum operating power.

2. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances according to claim 1, characterized in that, The photovoltaic half-wave damping controller includes a dead-zone detector, a proportional regulator, a high-pass filter, a phase compensation regulator, and a limiter; The dead-time detector determines the grid frequency and outputs the grid frequency corresponding to a specific time period. A proportional regulator is used to acquire the power grid frequency corresponding to a specific time period in real time, and to obtain a conditioning signal by calculation and amplification based on the acquired value; A high-pass filter is used to detect the frequency signal of low-frequency oscillations in a conditioned signal; A phase compensation regulator is used to adjust and process the phase of a low-frequency oscillation signal to obtain an initial photovoltaic active power compensation signal. A limiter is used to limit the initial photovoltaic active power compensation signal before outputting the photovoltaic active power compensation signal.

3. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances according to claim 2, characterized in that, Compensation signal for photovoltaic active power for: or f is the system frequency, Δf is the system frequency change, k1 is the proportional amplifier parameter, k2 and k3 are the high-pass filter parameters, and s is the microoperator. This indicates a rated grid frequency of 50Hz.

4. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances according to claim 2, characterized in that, The photovoltaic active power compensation signal is greater than 0 and less than 10% of the photovoltaic capacity itself.

5. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances according to claim 3, characterized in that, The energy storage full-wave damping controller includes a dead-zone detector, a proportional regulator, a high-pass filter, a phase compensation regulator, and a limiter; The dead-time detector is used to determine the grid frequency f and then output the grid frequency corresponding to a specific time period. A proportional regulator is used to acquire the power grid frequency corresponding to a specific time period in real time, and to obtain a conditioning signal by calculation and amplification based on the acquired value; A high-pass filter is used to detect the frequency signal of low-frequency oscillations in a conditioning signal; The phase compensation regulator is used to adjust and process the phase of the low-frequency oscillation signal to obtain the initial energy storage active power compensation signal. A limiter is used to limit the initial energy storage active power compensation signal before outputting the energy storage active power compensation signal.

6. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances according to claim 4, characterized in that, Compensation signal for active power of energy storage for: or Where f is the system frequency, Δf is the system frequency change, k4 is the proportional amplifier parameter, k5 and k6 are the high-pass filter parameters, and s is the microoperator. This indicates a rated grid frequency of 50Hz.

7. A photovoltaic energy storage control system for suppressing grid oscillations under frequency disturbances according to claim 4, characterized in that, The active power compensation signal for energy storage is within ±10% of the energy storage capacity.

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