Method and system for adaptive suppression of broadband oscillations in grid-connected new energy systems

Abstract

The application discloses a new energy grid-connected system wideband oscillation adaptive suppression method and system. The method comprises the following steps: monitoring the grid-connected point current of the new energy grid-connected system; when the system oscillates, taking the oscillation component in the grid-connected point current as the control reference signal of the wideband oscillation adaptive suppression device; and making the wideband oscillation adaptive suppression device output a signal opposite to the oscillation component to offset the oscillation component in the grid-connected point current, so as to realize the adaptive suppression of the wideband oscillation of the new energy grid-connected system. The application can be applied to the wideband oscillation suppression scene of the high-proportion new energy grid-connected system, can run in the energy-saving mode and the full operation mode, and has the advantages of convenient operation, simple control and adaptive suppression of the wideband oscillation of the system.

Description

Technical Field

[0001] This invention relates to the field of stability control technology in new energy power generation, and in particular to a broadband oscillation adaptive suppression method and system for new energy grid-connected systems. Background Technology

[0002] The continuous integration of a high proportion of renewable energy sources poses a significant challenge to the safe and stable operation of the power grid. The interactions between multiple power electronic devices and between the renewable energy grid-connected system and the AC grid can easily trigger broadband oscillations ranging from several hertz to hundreds of hertz. These broadband oscillations exhibit time-varying frequency and multi-frequency aliasing characteristics, and are severely affected by the dynamic characteristics of the power electronic devices and the system's operating conditions. Existing oscillation suppression strategies are not well-suited to all operating conditions, posing a significant challenge to broadband oscillation suppression in renewable energy grid-connected systems and severely restricting the efficient absorption of renewable energy.

[0003] CN112736982A discloses a wideband oscillation suppression method and system for grid-connected inverters of new energy sources. It is designed for traditional voltage and current dual closed-loop control controllers of grid-connected inverters of new energy sources. When the control mode of grid-connected inverters of new energy sources changes, this solution is no longer applicable and a new design and improvement solution is required. This solution is also not applicable to grid-connected inverters of new energy sources whose controllers are not open to the public. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for adaptive suppression of broadband oscillation in new energy grid-connected systems, which addresses the shortcomings of existing technologies and achieves adaptive suppression of broadband oscillation in new energy grid-connected systems.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a broadband oscillation adaptive suppression method for new energy grid-connected systems, comprising the following steps:

[0006] 1) At the beginning of each sampling period, the grid connection point voltage u of the new energy grid-connected system is... a u b u c , grid connection point current i a i b i c Wideband oscillation adaptive suppression device output current i a_s i b_s i c_s Sampling is performed separately; the wideband oscillation adaptive suppression device includes a DC-side capacitor, which is connected in parallel with the three-phase full-bridge inverter. An output filter inductor is connected to the midpoint of each bridge arm of the three-phase full-bridge inverter, and the output filter inductor is connected in parallel between the power grid and the new energy power generation system.

[0007] 2) The grid connection point voltage u of the new energy grid-connected system a u b u c After abc / dq transformation, the d-axis component u of the grid connection point voltage of the new energy grid-connected system is obtained. d q-axis component u q Wideband oscillation adaptive suppression device output current i a_s i b_s i c_s After abc / dq transformation, the d-axis component i of the output current is obtained. d_s q-axis component i q_s ;

[0008] 3) The grid connection point current i of the new energy grid-connected system a i b i c After the second-order generalized integrator G SOGI Obtain the fundamental component i of the grid connection point current. a_1 i b_1 i c_1 ;

[0009] 4) Fundamental component of grid connection current i a_1 i b_1 i c_1 Current i at the grid connection point of the new energy grid-connected system a i b i c After subtraction, the oscillation component Δi in the grid connection point current of the new energy grid-connected system is obtained. a , Δi b , Δi c oscillation component Δi a , Δi b , Δi c After abc / dq transformation, the d-axis component i of the control reference signal is obtained. d_ref q-axis component i q_ref ;

[0010] 5) The d-axis component i of the control reference signal d_ref q-axis component i q_ref The output current d-axis component i is respectively d_s q-axis component i q_s The difference is calculated, and after being controlled by a PI current controller, the d-axis component c of the modulated wave signal is obtained. d q-axis component c q ;

[0011] 6) d-axis component c of the modulated wave signal d With the q-axis component c of the modulated wave signal qAfter inverse abc / dq transformation, the duty cycle signal of the switching transistor of the wideband oscillation adaptive suppression device is obtained through PWM modulation, which controls the switching transistor to turn on and off.

[0012] This invention provides a broadband oscillation adaptive suppression device that suppresses broadband oscillations by being connected in parallel to a renewable energy grid-connected system. When system oscillation occurs, the oscillation component in the grid connection point current is used as the control reference signal for the broadband oscillation adaptive suppression device. This causes the device to output a signal inversely phase to the oscillation component, canceling it out and thus achieving adaptive suppression of broadband oscillations in the renewable energy grid-connected system. This invention does not require changes to the control structure of the renewable energy grid-connected inverter, nor does it require knowledge of the inverter's control mechanism. The reference command for the broadband oscillation adaptive suppression device's output signal can be obtained solely from the grid connection point current of the renewable energy grid-connected system.

[0013] In this invention, the second-order generalized integrator G SOGI The expression is: Where k is the controller bandwidth, ω is the resonant frequency, and s is the complex frequency.

[0014] In this invention, the broadband oscillation adaptive suppression device operates in two modes: an energy-saving mode and a full-operation mode. In energy-saving mode, when the new energy grid-connected system is running stably, the current controller input control reference signal of the broadband oscillation adaptive suppression device is 0, and the device is in standby mode. When the new energy grid-connected system experiences oscillation, the current controller G... PI The input control reference signal is i d_ref i q_ref The broadband oscillation adaptive suppression device is in operation; in full operation mode, the control reference signal for the broadband oscillation adaptive suppression device is i. d_ref i q_ref The broadband oscillation adaptive suppression device is in operation.

[0015] As an inventive concept, the present invention also provides a broadband oscillation adaptive suppression system for a new energy grid-connected system, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the method described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are: the present invention is convenient to operate, simple to control, and can achieve wideband oscillation adaptive suppression. Attached Figure Description

[0017] Figure 1 This is a block diagram of a broadband oscillation adaptive suppression device and its control method for a new energy grid-connected system, according to an embodiment of the present invention.

[0018] Figure 2 This is a waveform diagram of the grid connection point current of a new energy grid-connected system according to an embodiment of the present invention;

[0019] Figure 3 The waveform diagram shows the output current and control reference signal of the wideband oscillation adaptive suppression device according to an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] like Figure 1 As shown, this embodiment of the invention includes a wideband oscillation adaptive suppression device and a control system for the wideband oscillation adaptive suppression device. The wideband oscillation adaptive suppression device is powered by a DC power supply on its DC side and includes a DC-side capacitor, a three-phase full-bridge inverter, and an output filter inductor. The wideband oscillation adaptive suppression device is connected to the renewable energy grid-connected system in parallel. By monitoring the grid connection point current of the renewable energy grid-connected system, when oscillation occurs in the system, the oscillation component in the grid connection point current is used as the control reference signal for the wideband oscillation adaptive suppression device. This causes the wideband oscillation adaptive suppression device to output a signal inversely phase to the oscillation component, thus canceling the oscillation component in the grid connection point current and achieving adaptive suppression of wideband oscillation in the renewable energy grid-connected system. The control system for the wideband oscillation adaptive suppression device includes a signal acquisition and monitoring unit, a signal processing unit, a trigger signal generation unit, and a control unit for the wideband oscillation adaptive suppression device. line For line inductance, R line Let u be the line resistance. At the beginning of each sampling period, the grid connection point voltage u of the new energy grid-connected system is... a u b u c , grid connection point current i a i b i c Wideband oscillation adaptive suppression device output current i a_s i b_s i c_s Samples are taken separately; the grid connection point voltage u of the new energy grid-connected system is recorded. a u b u c After abc / dq transformation, the d-axis component u of the grid connection point voltage of the new energy grid-connected system is obtained.d q-axis component u q Wideband oscillation adaptive suppression device output current i a_s i b_s i c_s After abc / dq transformation, the d-axis component i of the device output current is obtained. d_s q-axis component i q_s ; q-axis component of grid connection point voltage in new energy grid-connected systems q After passing through the phase-locked loop controller G PLL The phase angle θ is obtained PLL This provides a reference phase angle for the abc / dq transformation and the inverse abc / dq transformation; the grid connection point current i of the new energy grid-connected system a i b i c After the second-order generalized integrator G SOGI Obtain the fundamental component i of the grid connection point current a_1 i b_1 i c_1 The fundamental component of the grid connection point current and the grid connection point current i of the new energy grid-connected system a i b i c The oscillation component Δi in the grid connection point current of the new energy grid-connected system is obtained by subtraction. a , Δi b , Δi c oscillation component Δi a , Δi b , Δi c After abc / dq transformation, the d-axis component i of the control reference signal for the broadband oscillation adaptive suppression device is obtained. d_ref q-axis component i q_ref The control reference signal d-axis component i of the broadband oscillation adaptive suppression device d_ref q-axis component i q_ref With respect to the d-axis component of the device output current i d_s q-axis component i q_s The d-axis component c of the modulated wave signal is obtained after PI control by the current controller. d q-axis component c q ; d-axis component c of the modulated wave signal d With the q-axis component c of the modulated wave signal q After inverse abc / dq transformation, the duty cycle signals Q1, Q2...Q6 of the wideband oscillation adaptive suppression device switching transistors are obtained through PWM modulation, which control the switching transistors to turn on and off.

[0023] The transfer function expression for the second-order generalized integrator (SOGI) is:

[0024]

[0025] Where k is the bandwidth of the second-order generalized integrator (in this embodiment, k is taken around 1.414), and ω is the resonant frequency.

[0026] The broadband oscillation adaptive suppression device can operate in energy-saving mode and full-operation mode within the system. In energy-saving mode, the system's stability is determined by detecting harmonic components through signal acquisition and monitoring, and the signal processing unit. When the system is operating stably, the broadband oscillation adaptive suppression device's current controller G... PI When the input control reference signal is 0, the device is in standby mode; when the system oscillates, a trigger signal is generated and input to the current controller G of the wideband oscillation adaptive suppression device. PI Current controller G PI The input control reference signal is i d_ref i q_ref The device is in operation. Full operating mode: Wideband oscillation adaptive suppression device current controller G PI The input control reference signal is i d_ref i q_ref The device is in operation.

[0027] Figure 2 The simulation waveform of the grid connection point current of the renewable energy grid-connected system demonstrates the suppression effect of the broadband oscillation adaptive suppression device on system oscillation after its operation. After the device is activated, system oscillation is quickly and effectively suppressed. In the simulation, the grid impedance is adjusted to simulate oscillation in the renewable energy grid-connected system. The system is in an oscillating state for 1.6 seconds (1.4s–1.6s shown in the figure). At 1.6s, the broadband oscillation adaptive suppression device is connected in parallel to the renewable energy grid-connected system and begins operation. After the device is activated, system oscillation is suppressed, and the system returns to stable operation.

[0028] Figure 3 The simulation waveforms of the output current and control reference signal of the broadband oscillation adaptive suppression device are shown, demonstrating the control effect of the output current of the device. After the broadband oscillation adaptive suppression device is put into operation, the output current of the device can quickly track the control reference signal. In the simulation, the grid impedance is adjusted to simulate oscillation in the renewable energy grid-connected system. The system is in an oscillating state for 1.6 seconds (the figure shows 1.4s to 1.6s, during which the broadband oscillation adaptive suppression device is not in operation to demonstrate system oscillation). At 1.6s, the broadband oscillation adaptive suppression device is connected in parallel to the renewable energy grid-connected system and starts operating. The output signal i of the broadband oscillation adaptive suppression device... d_s Quickly track the reference signal i d ref The system oscillations were suppressed, and the system returned to stable operation.

[0029] Example 2

[0030] Embodiment 2 of the present invention provides a suppression system corresponding to Embodiment 1 above, including a memory, a processor and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method of Embodiment 1 above.

[0031] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0032] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0033] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0034] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A broadband oscillation adaptive suppression method for a new energy grid-connected system, characterized in that, Includes the following steps: 1) At the beginning of each sampling period, the grid connection point voltage u of the new energy grid-connected system is... a u b u c , grid connection point current i a i b i c Wideband oscillation adaptive suppression device output current i a_s i b_s i c_s Sampling is performed separately; the wideband oscillation adaptive suppression device includes a DC-side capacitor, which is connected in parallel with the three-phase full-bridge inverter. An output filter inductor is connected to the midpoint of each bridge arm of the three-phase full-bridge inverter, and the output filter inductor is connected in parallel between the power grid and the new energy power generation system. 2) The grid connection point voltage u of the new energy grid-connected system a u b u c After abc / dq transformation, the d-axis component u of the grid connection point voltage of the new energy grid-connected system is obtained. d q-axis component u q Wideband oscillation adaptive suppression device output current i a_s i b_s i c_s After abc / dq transformation, the d-axis component i of the output current is obtained. d_s q-axis component i q_s ; 3) The grid connection point current i of the new energy grid-connected system a i b i c After the second-order generalized integrator G SOGI Obtain the fundamental component i of the grid connection point current. a_1 i b_1 i c_1 ; 4) Fundamental component of grid connection current i a_1 i b_1 i c_1 Current i at the grid connection point of the new energy grid-connected system a i b i c After subtraction, the oscillation component Δi in the grid connection point current of the new energy grid-connected system is obtained. a , Δi b , Δi c oscillation component Δi a , Δi b , Δi c After abc / dq transformation, the d-axis component i of the control reference signal is obtained. d_ref q-axis component i q_ref ; 5) The d-axis component i of the control reference signal d_ref q-axis component i q_ref The output current d-axis component i d_s q-axis component i q_s The difference is calculated, and after being controlled by a PI current controller, the d-axis component c of the modulated wave signal is obtained. d q-axis component c q ; 6) d-axis component c of the modulated wave signal d With the q-axis component c of the modulated wave signal q After inverse abc / dq transformation, the duty cycle signal of the switching transistor of the wideband oscillation adaptive suppression device is obtained through PWM modulation, which controls the switching transistor to turn on and off.

2. The adaptive suppression method for broadband oscillation in a new energy grid-connected system according to claim 1, characterized in that, Second-order generalized integrator G SOGI The expression is: Where k is the bandwidth of the second-order generalized integrator, ω is the resonant frequency, and s is the complex frequency.

3. The adaptive suppression method for broadband oscillation in a new energy grid-connected system according to claim 2, characterized in that, k takes the value 1.

414.

4. The adaptive suppression method for broadband oscillation in a new energy grid-connected system according to claim 1, characterized in that, The broadband oscillation adaptive suppression device operates in two modes: an energy-saving mode and a full-operation mode. In energy-saving mode, when the new energy grid-connected system is running stably, the current controller input control reference signal of the broadband oscillation adaptive suppression device is 0, and the device is in standby mode. When the new energy grid-connected system experiences oscillation, the current controller G... PI The input control reference signal is i d_ref i q_ref The broadband oscillation adaptive suppression device is in operation; In full operation mode, the control reference signal for the wideband oscillation adaptive suppression device is i. d_ref i q_ref The broadband oscillation adaptive suppression device is in operation.

5. A broadband oscillation adaptive suppression system for a new energy grid-connected system, comprising a memory, a processor, and a computer program stored in the memory; characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 4.

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