New energy hydrogen production power supply modularization control method

Abstract

The invention discloses a new energy hydrogen production power supply modularization control method, and belongs to the technical field of new energy hydrogen production. The control method comprises the following steps: firstly, determining a voltage reference value of a next switching period by judging a voltage reference initial value and an actual voltage sampling value; through dynamic design of a starting voltage reference value curve, modular parallel synchronous starting of a new energy hydrogen production power supply without a communication line is realized, and meanwhile, the problem of current surge in the system starting process is inhibited. According to the invention, the problem of asynchronous parallel starting of the new energy hydrogen production power supply modularization can be effectively solved, the dynamic ring current generated during parallel operation is reduced, the current surge problem in the system starting process is inhibited, and the transient performance and the stability of the new energy hydrogen production power supply modularization parallel system are further improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy hydrogen production, and in particular relates to a modular control method for a new energy hydrogen production power supply. Background Art

[0002] The development of hydrogen energy is of strategic significance, and green hydrogen is the ultimate goal of hydrogen energy development. Green hydrogen, as a hydrogen produced by electrolysis of water using new energy, has the characteristics and advantages of zero carbon emissions, high energy density, and flexible storage and transportation. It is considered to be an important part of the future energy system and the carrier of the fourth energy revolution. New energy hydrogen production power supply is the core equipment for green hydrogen production, which can be divided into voltage-type hydrogen production power supply and current-type hydrogen production power supply. Compared with voltage-type hydrogen production power supply, current-type hydrogen production power supply has broad application prospects due to its advantages such as adjustable power factor, wide voltage output range, and fast system response speed. However, in view of the needs of large-scale industrial applications, although the current-type hydrogen production power supply has superior performance, it still faces problems such as complex process, high cost and reduced energy efficiency in the process of expanding the capacity of a single system. Therefore, multi-module parallel technology has gradually become a current research hotspot. It is worth noting that for parallel systems, especially non-communication linear parallel systems, startup is accompanied by module startup failure and current surge. At present, the solutions to this problem can be divided into three categories: hardware-based startup control method, feedback / feedforward-based startup control method, and startup control method based on the idea of ​​slowly adjusting the static operating point. Among the above control methods, the hardware-based startup control method is more commonly used, but it usually leads to an increase in system volume and energy consumption, so it is easily restricted in practical applications. In addition, although the feedback / feedforward-based startup control method can achieve low-loss startup, its algorithm is complex and difficult to implement. Therefore, it is urgent to develop a startup control method for modular parallel systems of new energy hydrogen production power sources. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a modular control method for a new energy hydrogen production power supply, which can realize the modular parallel synchronous starting of a new energy hydrogen production power supply without a communication line through the dynamic design of the starting reference voltage value curve, while suppressing the current surge problem during the system startup process.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A modular control method for a new energy hydrogen production power source comprises the following steps:

[0006] S1: Sample the grid-side voltage and perform phase locking through a phase-locked loop. When the phase-locked angle θ reaches a preset value, the control method is enabled.

[0007] S2: Performing logic operation on the voltage reference initial value and the voltage sampling value to obtain the voltage reference value for the next switching cycle;

[0008] S3: Perform mathematical operations on the voltage reference value of the next switching cycle obtained in S2, the actual voltage sampling value, and the droop amount to generate a voltage error signal; after the voltage error signal passes through the PI proportional integral regulator, the DC side reference current value is obtained through the limiting link;

[0009] S4: The reference current value of the DC side is subtracted from the sampled current value to obtain a current error signal; the current error signal passes through the PI regulator and then through the limiter link, and is calculated with the phase-locked loop output to obtain a pre-modulation signal;

[0010] S5: When the CLA wave enable bit is 0, θ is determined; When k = 1, 2, 3, ..., CLA is enabled, and the pre-modulated signal is logically operated with the DC side sampling current value to generate a drive signal through the EPWM module.

[0011] The further improvement of the technical solution of the present invention is that: in S1, the phase-locked loop used is specifically a three-phase voltage phase-locked loop; the enabling judgment condition is that the phase-locked loop output θ satisfies When k = 1, 2, 3, ..., the startup control method is enabled.

[0012] A further improvement of the technical solution of the present invention is that in S2, the operation of performing a logical operation on the voltage reference initial value and the voltage sampling value is: the voltage reference initial value of the next switching cycle is calculated according to formula (1); when the current voltage reference value is greater than or equal to the actual voltage sampling value, the voltage reference initial value of the next switching cycle is the current voltage reference value; when the current voltage reference value is less than the actual voltage sampling value, the voltage reference initial value of the next switching cycle is the actual voltage sampling value:

[0013]

[0014] in, is the initial value of the reference voltage for the next switching cycle, is the reference voltage value of the current switching cycle, v o (T) is the actual sampled voltage value of the current switching cycle;

[0015] The final reference voltage value is calculated according to formula (2):

[0016]

[0017] Where λ is the slope of the startup curve and satisfies L dc is the DC side inductance, I max is the maximum current value allowed by the system, Em is the peak value on the network side, i dc is the DC output current value, T control To control the cycle.

[0018] The further improvement of the technical solution of the present invention is that in S3, the parameters of PI adjustment are designed as follows:

[0019] The transfer function expression of PI regulator is:

[0020]

[0021] Set the voltage outer loop bandwidth to 1 / 15 of the switching frequency, and obtain the PI regulator parameters according to formula (3):

[0022] 20lgG u (jω)|=-3dB (3)

[0023] Among them, G u (jω) is the closed-loop transfer function of the system;

[0024] The specific limiting range of the limiting link in the voltage outer loop controller is: max ~I max .

[0025] A further improvement of the technical solution of the present invention is that in S4, the parameters of PI adjustment are designed as follows:

[0026] The transfer function expression of PI regulator is:

[0027]

[0028] Set the current inner loop bandwidth value to 1 / 3 of the switching frequency. According to formula (4), the PI regulator parameters are obtained:

[0029] 20lg|G i (jω)|=-3dB (4)

[0030] Among them, G i (jω) is the system current inner loop transfer function after removing the voltage outer loop;

[0031] The specific limiting range of the limiting link in the current inner loop controller is: 0~I max ;

[0032] The premodulated signal is calculated according to formula (5):

[0033]

[0034] Among them, m x is the premodulation signal, x=a,b,c,I ref is the reference current amplitude.

[0035] A further improvement of the technical solution of the present invention is that: the pre-modulation signal is divided by the DC side current sampling value to obtain a modulation signal, and the modulation signal is input to the EPWM module to compare with the triangular carrier to generate a drive signal.

[0036] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0037] 1. The present invention effectively suppresses the surge current generated when the system starts up and ensures the smoothness of the system startup through the reasonable design of the startup timing and the startup curve.

[0038] 2. The present invention realizes the synchronous startup of each module in the parallel system without communication lines by dynamically adjusting the initial value of the system startup reference voltage, effectively reducing the dynamic circulating current when the parallel system is started. It improves the transient performance of the parallel system of new energy hydrogen production power supply and further improves the system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the modular control method of the new energy hydrogen production power supply of the present invention;

[0040] Figure 2 It is a flow chart of the control method of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and embodiments:

[0042] A startup control method for a modular parallel system of a new energy hydrogen production power source comprises the following steps:

[0043] S1: Determine the startup method enable state according to the phase-locked loop output;

[0044] The three-phase voltage phase-locked loop is used to phase-lock the grid voltage. When the phase-locked loop output θ meets the preset value, that is, , enables the startup control method.

[0045] S2: Performing logic operation on the voltage reference initial value and the sampling value to obtain the voltage reference value for the next switching cycle;

[0046] First, calculate the initial value of the voltage reference for the next switching cycle:

[0047]

[0048] Current voltage reference value Greater than or equal to the actual voltage sampling value v o (T), the voltage of the next switching cycle refers to the initial value is the current voltage reference value Current voltage reference value Less than the actual voltage sampling value v o (T), the voltage of the next switching cycle refers to the initial value is the actual voltage sampling value v o (T);

[0049] Calculate the voltage reference value for the next switching cycle:

[0050]

[0051] Where λ is the slope of the startup curve and satisfies L dc is the DC side inductance, I max is the maximum current value allowed by the system, E m is the peak value on the network side, i dc is the DC output current value, T control To control the cycle.

[0052] S3: using the voltage reference value of the next switching cycle obtained in S2 to obtain a DC side reference current value;

[0053] The process of generating the DC side reference current is as follows: the voltage reference value of the next switching cycle obtained in S2 is subtracted from the actual voltage sampling value and the droop amount to generate a voltage error signal; the voltage error signal is then calculated by a PI regulator with a bandwidth of 1 / 15 of the switching frequency and then limited to -I max ~I max The limiting link is completed, and finally the DC side reference current value is obtained.

[0054] S4: using the phase angle obtained in S1, obtaining a premodulated signal;

[0055] The process of generating the premodulation signal is as follows: subtract the DC side reference current value from the sampled current value to obtain the current error signal; then the current error signal passes through a PI regulator with a bandwidth of 1 / 3 of the switching frequency and is limited to a range of 0 to I max The limiting link generates the reference current amplitude; then, the pre-modulation signal is calculated according to the formula:

[0056]

[0057] Among them, m a 、m b 、m c is the premodulation signal, I ref is the reference current amplitude.

[0058] S5: Determine the CLA (Control Logic Accelerator) wave enabling state and obtain the driving signal;

[0059] The process of generating the driving signal is as follows: when the CLA wave enable bit is 0, θ is determined. CLA is enabled; under this premise, the pre-modulated signal is divided by the DC side sampling current value and the absolute value is taken, and then compared with the three-phase carrier through the EPWM (Enhance Pulse Width Modualtion) module to generate a driving signal.

[0060] Example

[0061] Figure 1 This is a schematic diagram of the modular control method of the new energy hydrogen production power supply based on the present invention. The basic principle of the present invention is shown in the dotted box. According to the output of the phase-locked loop, the enabling state of the startup method is determined. After the control method is enabled, the drive signal is obtained by determining the enabling state of the CLA wave. The modulation scheme adopted by this system is a discontinuous modulation method, but it is not limited to this modulation method. All existing modulation schemes can be used in conjunction with the startup control method proposed in the present invention. Here, a discontinuous modulation scheme is taken as an example to further illustrate the basic working principle and structure of the control method proposed in the present invention.

[0062] Figure 1 In the figure, L and C are the inductance and capacitance of the AC side filter respectively, and the two form an LC filter to attenuate the high-frequency harmonics in the bridge arm current. n (n=1,…,6) and D n (n=1,…,6) are switch tube and diode respectively, which are connected in series to form the basic switch unit of the system to ensure the bidirectional control of the system on voltage. dc It is a DC side diode, which can effectively ensure that i dc The continuity of the system can also improve the system efficiency to a certain extent. dc is the DC side energy storage inductor, C dc is the load capacitance. In this example, the implementation steps of the control method specifically include:

[0063] S1: Use the three-phase voltage phase-locked loop to phase-lock the grid voltage. When the phase-locked loop output θ satisfies When , enable the startup control method;

[0064] S2: Calculate the initial value of the voltage reference for the next switching cycle:

[0065]

[0066] When the current voltage reference value is greater than or equal to the actual voltage sampling value, the voltage reference initial value of the next switching cycle is the current voltage reference value; when the current voltage reference value is less than the actual voltage sampling value, the voltage reference initial value of the next switching cycle is the actual voltage sampling value.

[0067] Calculate the voltage reference value for the next switching cycle:

[0068]

[0069] S3: Subtract the voltage reference value of the next switching cycle from the actual voltage sampling value and the droop value to generate a voltage error signal. The voltage error signal is passed through a PI regulator with a bandwidth of 1 / 15 of the switching frequency to obtain a voltage outer loop output signal. The voltage outer loop output signal is passed through a limiting link with a limiting range of -15.5 to 15.5 to obtain a DC side reference current value.

[0070] S4: Subtract the DC side reference current value from the sampled current value to obtain a current error signal. The current error signal is passed through a PI regulator with a bandwidth of 1 / 3 of the switching frequency to obtain a current inner loop output signal. The current inner loop output signal passes through a limiting link to obtain a reference current amplitude.

[0071] Calculate and generate the premodulated signal:

[0072]

[0073] Step S5: When the CLA wave enable bit is 0, θ is determined. When CLA is enabled, the pre-modulation signal is divided by the DC side sampling current value and the absolute value is taken to obtain the modulation signal. The modulation signal is input to the EPWM module and compared with the three-phase carrier to generate a drive signal.

[0074] Figure 2 The control method flow chart of the present invention is shown. First, the ADC (Analog Digital Conversion) interrupt is triggered and the start is officially started. After the interrupt is triggered, the context save operation is immediately executed. Subsequently, the system enters the stage of calculating the reference voltage for the next switching cycle. When the current voltage reference value is greater than or equal to the actual voltage sampling value, the initial voltage reference value for the next switching cycle is the current voltage reference value; when the current voltage reference value is less than the actual voltage sampling value, the initial voltage reference value for the next switching cycle is the actual voltage sampling value.

[0075] Substitute the initial value of the voltage reference for the next switching cycle into the formula to calculate the voltage reference value for the next switching cycle:

[0076]

[0077] Finally, the context recovery operation is performed, and the obtained voltage reference value is output to the control system.

[0078] In the traditional startup control method, the setting of the system startup curve only considers the startup logic pre-set in this module. In this case, when a module is activated first, it is easy to cause the voltage reference value of the next cycle of the subsequently activated module to be less than the actual voltage sampling value, resulting in the phenomenon that the later activated module cannot be effectively started. In the present invention, the setting process of the startup curve takes into account the coupling relationship of other modules of the system to this module in real time. When the current voltage reference value is greater than or equal to the actual voltage sampling value, the initial value of the voltage reference of the next switching cycle is set to the current voltage reference value; when the current voltage reference value is less than the actual voltage sampling value, the initial value of the voltage reference of the next switching cycle is the actual voltage sampling value. Further, the initial value of the voltage reference of the next switching cycle is superimposed with the basic increment to obtain the voltage reference value of the next switching cycle, so that the voltage reference value of the next cycle is always greater than or equal to the actual voltage sampling value. On the basis of ensuring the effective suppression of the surge current during the system startup process, the phenomenon that the module cannot be effectively started when the traditional startup control method is adopted due to inconsistent parameters between modules is successfully avoided.

[0079] Aiming at the startup problem of the modular parallel system of hydrogen production power sources from new energy, the present invention proposes a control method without communication lines, which effectively solves the surge current and the asynchronism problems between modules during the startup of the system, reduces the dynamic circulating current during the startup of the system, and improves the transient performance and stability of the modular parallel system of hydrogen production power sources from new energy.

[0080] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those skilled in the art in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here. The specific implementation methods described above further explain the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A modular control method for a new energy hydrogen production power source, characterized in that: The steps include: S1: Sample the grid-side voltage and perform phase locking through a phase-locked loop. When the phase-locked angle θ reaches a preset value, the control method is enabled. S2: Performing logic operation on the voltage reference initial value and the voltage sampling value to obtain the voltage reference value for the next switching cycle; S3: Perform mathematical operations on the voltage reference value of the next switching cycle obtained in S2, the actual voltage sampling value, and the droop amount to generate a voltage error signal; after the voltage error signal passes through the PI proportional integral regulator, the DC side reference current value is obtained through the limiting link; S4: The reference current value of the DC side is subtracted from the sampled current value to obtain a current error signal; the current error signal passes through the PI regulator and then through the limiter link, and is calculated with the phase-locked loop output to obtain a pre-modulation signal; S5: When the CLA wave enable bit is 0, θ is determined; When k = 1, 2, 3, ..., CLA is enabled, and the pre-modulated signal is logically operated with the DC side sampling current value to generate a drive signal through the EPWM module.

2. A modular control method for a new energy hydrogen production power source according to claim 1, characterized in that: In S1, the phase-locked loop used is specifically a three-phase voltage phase-locked loop; the enabling condition is that the phase-locked loop output θ satisfies When k = 1, 2, 3, ..., the startup control method is enabled.

3. A modular control method for a new energy hydrogen production power source according to claim 1, characterized in that: In S2, the operation of performing a logical operation on the voltage reference initial value and the voltage sampling value is: calculating the voltage reference initial value of the next switching cycle according to formula (1); when the current voltage reference value is greater than or equal to the actual voltage sampling value, the voltage reference initial value of the next switching cycle is the current voltage reference value; When the current voltage reference value is less than the actual voltage sampling value, the initial voltage reference value of the next switching cycle is the actual voltage sampling value: in, is the initial value of the reference voltage for the next switching cycle, is the reference voltage value of the current switching cycle, v o (T) is the actual sampled voltage value of the current switching cycle; The final reference voltage value is calculated according to formula (2): Where λ is the slope of the startup curve and satisfies L dc is the DC side inductance, I max is the maximum current value allowed by the system, E m is the peak value on the network side, i dc is the DC output current value, T control To control the cycle.

4. A modular control method for a new energy hydrogen production power source according to claim 1, characterized in that: In S3, the parameters of PI regulation are designed as follows: The transfer function expression of PI regulator is: Set the voltage outer loop bandwidth to 1 / 15 of the switching frequency, and obtain the PI regulator parameters according to formula (3): 20lg|G u (jω)|=-3dB (3) Where, G u (jω) is the closed-loop transfer function of the system; The specific limiting range of the limiting link in the voltage outer loop controller is: max ~I max .

5. A modular control method for a new energy hydrogen production power source according to claim 1, characterized in that: In S4, the parameters of PI regulation are designed as follows: The transfer function expression of PI regulator is: Set the current inner loop bandwidth value to 1 / 3 of the switching frequency. According to formula (4), the PI regulator parameters are obtained: 20lg|G i (jω)|=-3dB (4) Where, G i (jω) is the system current inner loop transfer function after removing the voltage outer loop; The specific limiting range of the limiting link in the current inner loop controller is: 0~I max ; The premodulated signal is calculated according to formula (5): Among them, m x is the premodulation signal, x=a,b,c,I ref is the reference current amplitude.

6. A modular control method for a new energy hydrogen production power source according to claim 1, characterized in that: The pre-modulation signal is divided by the DC side current sampling value to obtain the modulation signal, which is input into the EPWM module and compared with the triangular carrier to generate the drive signal.

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