Grid-connected control method and grid-connected controller of hydrogen fuel cell energy supply system
By adopting the grid-connected control method of second-order orthogonal transformation and coordinate conversion in the hydrogen fuel cell energy supply system, the frequency fluctuation problem when the inverter and grid power frequency is different is solved, and more accurate phase locking and more Efficient grid-connected control extends the life of hydrogen fuel cells.
Patent Information
- Application Number
- CN202411633058.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-02-07
AI Technical Summary
In hydrogen fuel cell power generation system, when the inverted alternating alternating current is different from the alternating current frequency in the power grid, it will cause fluctuations in the alternating current frequency in the power grid, damage substation facilities and power consumption equipment, and affect the long-term performance of hydrogen fuel cells.
A grid-connected control method for hydrogen fuel cell energy supply system is adopted to obtain the phase of the grid voltage through second-order orthogonal transformation and coordinate conversion, and phase lock is realized by closed-loop control, and the proportional integral controller and quasi-PR controller are combined. The network voltage and current are regulated to ensure that they are consistent with the low phase of the grid voltage.
It improves the phase locking accuracy, reduces the damage to hydrogen fuel cells, extends the service life of hydrogen fuel cells, and enhances the matching degree of voltage and anti-interference ability when connected to the grid.
Smart Images
Figure CN119401553A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of new energy power supply, and in particular to a grid-connected control method and a grid-connected controller for a hydrogen fuel cell energy supply system. Background Art
[0002] In the hydrogen fuel cell power generation system, the hydrogen fuel cell outputs direct current, while the power grid transmits alternating current. Therefore, the direct current output by the hydrogen fuel cell needs to be converted into alternating current through an inverter before it can be connected to the power grid. When the frequency of the inverted alternating current is different from that of the alternating current in the power grid, the frequency of the alternating current in the power grid will fluctuate, which will not only damage the substation facilities and electrical equipment in the power grid, but also affect the long-term performance of the hydrogen fuel cell. Therefore, how to ensure that the inverted alternating current maintains the same frequency as the alternating current in the power grid is the primary issue to be solved in order to extend the life of the hydrogen fuel cell.
[0003] The basic function of the phase-locked loop is to lock the phase of the detected signal. It is a feedback system that enables the oscillator phase to accurately track the applied phase signal. The phase-locked loop phase-locks the grid voltage and can provide the phase signal to the grid-connected current in real time, which is beneficial to the control of the grid-connected current. There are two basic implementation methods of the phase-locked loop: zero crossing and multiplication. Zero crossing is an open-loop phase-locked method, and multiplication is a closed-loop phase-locked method. The first two phase-locked methods have unsatisfactory results in the harmonics and distortion process of the system. Therefore, there is an urgent need for an accurate phase-locked method to meet the needs of extending the life of hydrogen fuel cells. Summary of the invention
[0004] In order to improve the accuracy of phase locking and thus extend the life of hydrogen fuel cells, the present invention provides a grid-connected control method and a grid-connected controller for a hydrogen fuel cell energy supply system.
[0005] In a first aspect, the present invention provides a grid-connected control method for a hydrogen fuel cell energy supply system, which adopts the following technical solution: A grid-connected control method for a hydrogen fuel cell energy supply system comprises the following steps: Orthogonal transformation: Transform the grid voltage Input value second-order orthogonal signal generator, output two phase difference is Two sinusoidal signals and , , and The relationship is as follows: ; ; Coordinate transformation: Transform the rotating coordinate system into the stationary coordinate system. The coordinate transformation relationship is as follows: ; In the formula, is the component of the virtual voltage on vector d, is the component of the virtual voltage on the vector q, Phase lock: Through closed loop control , at this time, the phase of the grid voltage is obtained , complete the phase locking of the grid voltage; Grid connection: The inverter is controlled according to the phase-locked result to make the phase of the grid-connected voltage consistent with the low phase of the grid voltage, thereby achieving grid connection.
[0006] Optionally, a DC bus voltage regulation step is further provided between the phase locking step and the grid connection step; DC bus voltage control: Based on the crystal oscillator circuit and the proportional integral controller, the grid-connected voltage is closed-loop controlled, where the grid-connected voltage outer loop transfer function is as follows: ; In the formula, is the equivalent proportional parameter of the current inner loop, is the proportional parameter of the proportional-integral controller, is the integral gain of the proportional-integral controller.
[0007] Optionally, a DC bus current regulation step is further provided between the phase locking step and the grid connection step; DC bus current control: Based on the crystal oscillator circuit and the quasi-PR controller, the grid-connected current is closed-loop controlled, where the transfer function of the grid-connected current in the quasi-PR controller is as follows: ; In the formula, is the proportionality coefficient, is the resonance coefficient, is the resonant frequency, s is the complex frequency operator, is the acceptable gain bandwidth.
[0008] Optionally, the acceptable gain bandwidth is 5-10.
[0009] In a second aspect, the present invention provides a grid-connected controller for a hydrogen fuel cell energy supply system, which adopts the following technical solution: A grid-connected controller for a hydrogen fuel cell energy supply system applies the grid-connected control method for a hydrogen fuel cell energy supply system as described in the first aspect.
[0010] In summary, the present invention includes at least one of the following beneficial technical effects: 1. By using two-phase orthogonal variables to perform single-phase phase locking, the phase locking is more accurate, reducing damage to hydrogen fuel cells and extending the service life of hydrogen fuel cells.
[0011] 2. By using the proportional integral method to perform closed-loop control of the grid-connected voltage, the DC signal can be well tracked without static error, thereby improving the matching degree of the voltage when connected to the grid.
[0012] 3. By using a quasi-PR controller to perform closed-loop control of the grid-connected current, a certain amplitude gain can be maintained, thereby effectively coping with the influence of device parameter errors and limited word length, and having strong anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is the grid connection flow chart of the hydrogen fuel cell functional system; Figure 2 This is the control system diagram when phase locked; Figure 3 This is the control system diagram when the DC bus voltage is regulated; Figure 4 This is the control system diagram for DC bus current regulation. DETAILED DESCRIPTION
[0014] The following combination Figures 1 to 4 The present invention is described in further detail.
[0015] Embodiment 1: This embodiment discloses a grid-connected control method for a hydrogen fuel cell energy supply system, referring to Figure 1 The grid-connected control method of the hydrogen fuel cell energy supply system comprises the following steps: S1: Orthogonal transformation: refer to Figure 2 , the grid voltage Input value second-order orthogonal signal generator, output two phase difference is Two sinusoidal signals and , , and The relationship is as follows: ; .
[0016] S2: Coordinate transformation: reference Figure 2 , the rotating coordinate system and the stationary coordinate system are transformed, and the coordinate transformation relationship is as follows: ; In the formula, is the component of the virtual voltage on vector d, is the component of the virtual voltage on the vector q.
[0017] S3: Phase lock: Reference Figure 2 , through closed-loop control , at this time, the phase of the grid voltage is obtained , completing the phase locking of the grid voltage.
[0018] Specifically, when phase-locking, the grid voltage is used as input, and the orthogonal transformation and coordinate conversion are first used to obtain the components on the vector q, and then As the reference input of the control system, it is tracked by a PI controller, so that the phase of the grid voltage can be obtained. .
[0019] The expression function of the PI controller is as follows: ; In the formula, is the proportional parameter of the proportional-integral controller, is the integral gain of the proportional-integral controller.
[0020] S4: DC bus voltage control: refer to Figure 3 , according to the crystal oscillator circuit and the proportional integral controller, the grid-connected voltage is closed-loop regulated, where the grid-connected voltage outer loop transfer function is as follows: ; In the formula, is the equivalent proportional parameter of the current inner loop, is the proportional parameter of the proportional-integral controller, is the integral gain of the proportional-integral controller.
[0021] Specifically, when the DC bus voltage is regulated, the grid voltage is used as input and the transfer function of the voltage outer loop PI controller is adopted. Tracking and closed-loop transfer function of the inner current loop The output voltage is obtained by regulation.
[0022] S5: DC bus current control: refer to Figure 4 , according to the crystal oscillator circuit and the quasi-PR controller, the grid-connected current is closed-loop regulated, where the transfer function of the grid-connected current in the quasi-PR controller is as follows: ; In the formula, is the proportional coefficient of the proportional-integral controller, is the resonance coefficient of the proportional-integral controller, is the resonant frequency, s is the complex frequency operator, is the acceptable gain bandwidth, The value range is 5-10rad / s.
[0023] Specifically, when the DC bus current is regulated, the grid current is used as input, and a second-order orthogonal signal generator is used to convert it into a DC quantity in a synchronously rotating dq coordinate system. The phase of the grid voltage is obtained during the conversion. As a reference, the dq axis DC signal is tracked by the quasi-PR controller, and then the current is converted into an AC quantity in the αβ coordinate system by a second-order orthogonal signal generator. The phase of the grid voltage is obtained during the conversion. As a reference.
[0024] S6: Grid connection: The inverter is controlled according to the phase-locked result, so that the phase of the grid-connected voltage is consistent with the low phase of the grid voltage, and the grid-connected voltage and grid-connected current are consistent with the grid voltage and grid current, thereby achieving grid connection.
[0025] The implementation principle of the grid-connected control method of the hydrogen fuel cell energy supply system of this embodiment is: The DC virtual voltage is obtained by performing a second-order orthogonal transformation according to the grid voltage, and then the component on the vector q is controlled. Make it equal to 0 as the reference input of the control system and use PI controller to track it, so that the phase of the grid voltage can be obtained Then, the grid voltage is used as input and the transfer function of the voltage outer loop PI controller is adopted. Tracking and closed-loop transfer function of the inner current loop The output voltage is obtained by regulation. At the same time, the grid current is used as input and a second-order orthogonal signal generator is used to convert it into a DC quantity in a synchronously rotating dq coordinate system. The phase of the grid voltage is obtained during the conversion. As a reference, the dq axis DC signal is tracked by the quasi-PR controller, and then the current is converted into an AC quantity in the αβ coordinate system by a second-order orthogonal signal generator. The phase of the grid voltage is obtained during the conversion. As a reference, the output current is obtained. The output of the grid-connected energy supply system obtained in this way is more matched with the input required by the power grid, which can reduce the damage to the substation facilities and power equipment in the power grid, and also improve the long-term performance of hydrogen fuel cells; and the matching is fast, the calculation amount is small, and the response is sensitive.
[0026] Embodiment 2: This embodiment discloses a grid-connected controller for a hydrogen fuel cell energy supply system, which is used to apply and implement the grid-connected control method for the hydrogen fuel cell energy supply system described in Embodiment 1.
[0027] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A grid-connected control method for a hydrogen fuel cell energy supply system, characterized in that: The following steps are involved: Orthogonal transformation: Transform the grid voltage Input value second-order orthogonal signal generator, output two phase difference is Two sinusoidal signals and , , and The relationship is as follows: ； ； Coordinate transformation: Transform the rotating coordinate system into the stationary coordinate system. The coordinate transformation relationship is as follows: ； In the formula, is the component of the virtual voltage on vector d, is the component of the virtual voltage on the vector q, Phase lock: Through closed loop control , at this time, the phase of the grid voltage is obtained , complete the phase locking of the grid voltage; Grid connection: The inverter is controlled according to the phase-locked result to make the phase of the grid-connected voltage consistent with the low phase of the grid voltage, thereby achieving grid connection.
2. The grid-connected control method of a hydrogen fuel cell energy supply system according to claim 1, characterized in that: A DC bus voltage regulation step is also provided between the phase locking step and the grid connection step; DC bus voltage control: Based on the crystal oscillator circuit and the proportional integral controller, the grid-connected voltage is closed-loop controlled, where the grid-connected voltage outer loop transfer function is as follows: ； In the formula, is the equivalent proportional parameter of the current inner loop, is the proportional parameter of the proportional-integral controller, is the integral gain of the proportional-integral controller.
3. The grid-connected control method of a hydrogen fuel cell energy supply system according to claim 1, characterized in that: A DC bus current control step is further provided between the phase locking step and the grid connection step; DC bus current control: Based on the crystal oscillator circuit and the quasi-PR controller, the grid-connected current is closed-loop controlled, where the transfer function of the grid-connected current in the quasi-PR controller is as follows: ； In the formula, is the proportionality coefficient, is the resonance coefficient, is the resonant frequency, s is the complex frequency operator, is the acceptable gain bandwidth.
4. The grid-connected control method of a hydrogen fuel cell energy supply system according to claim 3, characterized in that: The acceptable gain bandwidth is 5-10.
5. A grid-connected controller for a hydrogen fuel cell energy supply system, characterized in that: A grid-connected control method for a hydrogen fuel cell energy supply system as described in any one of claims 1 to 4 is applied.