A control method for participating in deep peak regulation of power grid by hydrogen production through alkaline solution electrolysis

Abstract

The present invention provides a control method for alkaline liquid electrolysis hydrogen production to participate in deep peak regulation of the power grid. The present invention can achieve frequency response, and its mechanism is droop control, which can serve as a frequency support resource for the power grid. The present invention can also ensure that the maximum efficiency of hydrogen production can be achieved under different working conditions, solving the problems of narrow operating range and low efficiency under low-load conditions in traditional hydrogen production strategies. Using the present invention, wide-range and high-efficiency hydrogen production of alkaline liquid electrolyzers can be achieved to achieve frequency response of a wider range of power for the power grid. And at the rectifier level, the droop coefficient of Pf is larger, so as to participate more deeply in peak regulation.

Description

Technical Field

[0001] The invention relates to a control method for participating in deep peak regulation of a power grid by hydrogen production through electrolysis of alkaline solution, belonging to the operation control technology of a hydrogen-electricity coupling system in the field of new energy. Background Art

[0002] On the one hand, the hydrogen energy industry has made great progress, and vigorously developing hydrogen energy has become the development trend of the future energy industry. Compared with traditional fossil energy, hydrogen energy has the advantages of high calorific value and only water as a reaction product, making it an ideal alternative energy source. From the perspective of the type of electrolyzer used, electrolytic hydrogen production technology is divided into proton exchange membrane (PEM) electrolysis, solid oxide (Solid Oxide) electrolysis, proton ceramic electrolysis cell (PCEC) electrolysis and alkaline water electrolysis (AWE). Among the listed electrolytic hydrogen production technologies, alkaline water electrolysis hydrogen production technology is the most mature.

[0003] On the other hand, the trend of power electronics in the power grid is becoming more and more obvious. In order to improve the inertia of the power grid, it is imperative to use different frequency support resources in the source-grid-load-storage direction to improve frequency stability. Although the traditional alkaline liquid electrolyzer hydrogen production control strategy is also based on droop control, from the perspective of safe production, there is a relatively large minimum operating power. In other words, the traditional frequency droop control of the alkaline liquid electrolyzer hydrogen production control strategy has the disadvantages of a narrow operating range and insufficient frequency support resources, and cannot participate more deeply in the peak regulation of the power grid. Summary of the invention

[0004] The purpose of the present invention is to provide a control method for the participation of alkaline solution electrolysis hydrogen production in deep peak regulation of the power grid in view of the deficiencies of the prior art. The present invention solves the problem that the power regulation range of the traditional alkaline solution electrolyzer hydrogen production circuit based on the droop control side is narrow and cannot participate more deeply in the peak regulation of the power grid. Under the premise of ensuring the purity of hydrogen production, the present invention effectively expands the frequency support resources of the power system, so that the hydrogen production equipment can participate more deeply in the peak regulation of the power grid.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A control method for participating in deep peak regulation of a power grid by electrolyzing alkali liquid hydrogen, wherein the hydrogen production equipment for electrolyzing alkali liquid hydrogen is connected to an external power grid through a circuit, wherein the circuit comprises a rectifier circuit, a Buck converter circuit and a pulse generator circuit connected in sequence; the electric energy of the external power grid is used to electrolyze alkali liquid hydrogen, and the power of the electrolyzing alkali liquid hydrogen is controlled to participate in deep peak regulation of the power grid, as follows:

[0007] Real-time collection of the frequency f and output current of the external power grid;

[0008] The reference value of the rectifier circuit is determined based on the frequency of the external power grid, and the rectifier circuit adopts i based on the obtained reference value. d -f or Pf droop control, where i d is the current of the rectifier circuit, P is the active power; when the external grid frequency f min , set the reference input current i of the rectifier circuit dref =0, reference active power P ref =0, the hydrogen production equipment is cut off from the power grid; when the system frequency f max , set the reference input current i of the rectifier circuit dref =i max , reference active power P ref =P N ;i max It indicates the current input from the external power grid to the rectifier circuit under the rated operating conditions of the hydrogen production equipment. min <f<f mdx When the reference current i of the rectifier circuit is set dref =i0+k*(ff N ), reference active power P ref =P N +k*(ff N ), where i0 is equal to i max , P N is the rated power of the electrolyzer, f N Indicates the rated frequency of the external power grid, f min Indicates the lowest frequency allowed for the hydrogen production equipment to operate, f max Indicates the maximum frequency allowed for the operation of the hydrogen production equipment, f max Equal to the rated frequency; min Indicates frequency f min Under the condition, the current input from the external power grid to the rectifier circuit;

[0009] The control strategy of the Buck converter circuit is determined based on the frequency of the external power grid, and the Buck converter circuit is controlled. When the power grid frequency f set3 , f set3 is the frequency reference value, f min <f set3 <f max , f set3 The reference current I is generated by the hysteresis circuit. set1 =-k p (u set1 -u), u represents the voltage on both sides of the polar capacitor C, uset1 It represents the reference value of the voltage u on both sides of the polar capacitor C under the control strategy of constant current of the DC inductor L, which is reasonably selected according to the maximum voltage that the voltage on both sides of the polar capacitor C can withstand; then the current loop control strategy is used to adjust the duty cycle D of the field effect tube d1 in the Buck converter circuit in real time. set1 =k l (I set1 -I), k l represents the proportional control parameter of the current loop of the Buck converter circuit, I represents the current of the inductor L in the Buck converter circuit; when the grid frequency f set4 , f min <f set4 <f set3 By adopting the control strategy of constant current of DC inductor L, I set1 =I op , I op Indicates the pulse current amplitude corresponding to the maximum efficiency, and adjusts the duty cycle D of the field effect tube d1 in the Buck converter circuit in real time set1 =k l (I set1 -I).

[0010] The control strategy of the pulse generating circuit is determined based on the frequency of the external power grid, and the pulse generating circuit is controlled, wherein: when the power grid frequency f set3 When the second-stage pulse generating circuit adopts a constant duty cycle control strategy, the duty cycle D of the field effect tube d2 in the pulse generating circuit is controlled. set2 =0, when the grid frequency f set4 The second-stage pulse generating circuit adopts a control strategy of constant voltage of capacitor C, and controls the duty cycle of field effect transistor d2 in the pulse generating circuit to be D set2 =k ll (u set2 -u);u set2 It represents the reference value of u under the control strategy of constant voltage of capacitor C, which is reasonably selected according to the maximum voltage that the voltage on both sides of the polar capacitor C can withstand.

[0011] Compared with the traditional large-scale power grid hydrogen production technology, the present invention has two outstanding advantages. First, it can achieve frequency response, and its mechanism is droop control, which can serve as a frequency support resource for the power grid. The second is multi-modal self-optimization technology, which has the advantage of being able to ensure maximum efficiency hydrogen production under different working conditions, solving the problems of narrow operating range and low efficiency under low-load conditions in traditional hydrogen production strategies. Using the present invention, wide-range and high-efficiency hydrogen production in alkaline liquid electrolyzers can be achieved to achieve a wider range of power frequency response for the power grid. And at the rectifier level, the droop coefficient of Pf is larger, so that it can participate more deeply in peak regulation.

[0012] Furthermore, the circuit includes six bridge arm switch tubes d3, inductors L s , inductor L, polar capacitor C, fast recovery diode D1, field effect transistor d1, fast recovery diode D2 and field effect transistor d2; the external power grid and inductor L s The first end of the inductor L s The second end is connected to the AC port of the six-arm switch tube d3, the DC output side of the bridge arm switch tube d3 is connected in parallel with the polar capacitor C, the polar capacitor C is connected in series with the field effect tube d1, the source side of the field effect tube d1 is connected in parallel with the fast recovery diode D1, the cathode side of the fast recovery diode D1 is connected in series with the inductor L, and the inductor L is connected in parallel with the field effect tube d2. The field effect tube d2 is connected in series with the fast recovery diode D2.

[0013] Further, the rectifier circuit adopts i based on the obtained reference value d The droop control is performed in any of the droop control modes of -f or Pf, and the modulation wave output after the droop control is divided by the DC side capacitor voltage u in the Buck converter circuit to obtain a modulation wave as a control signal of the rectifier circuit.

[0014] Furthermore, the value range of the period T2 of the PWM control signal of the field effect transistor d2 in the pulse generating circuit is [0.05s, 0.5s].

[0015] Furthermore, the PWM control signal of the field effect transistor d1 in the rectifier circuit and the Buck converter circuit adopts a high-frequency modulated carrier.

[0016] The beneficial effects of the present invention are as follows: the present invention designs a control method for alkaline solution electrolysis hydrogen production participating in deep peak regulation of the power grid. The traditional droop control electrolysis hydrogen production circuit allows a higher minimum output power and a lower active power adjustment range, resulting in lower frequency support resources that can be provided. The circuit topology and control method adopted by the present invention can efficiently electrolyze hydrogen production under different working conditions, and can improve the active power adjustment range without changing the power quality. At the same time, the modulation wave is divided by the DC side capacitor voltage to further suppress interharmonics and improve the power quality of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a control method for participating in deep peak regulation of a power grid by electrolyzing hydrogen produced by alkaline solution provided in an embodiment of the present application;

[0018] Figure 2 A voltage and current waveform diagram of a hydrogen production electrolyzer connected to the output side of the circuit provided in an embodiment of the present application;

[0019] Figure 3This is a comparison chart of the efficiency of the hydrogen production electrolyzer connected to the output side of the circuit provided in the embodiment of the present application under the proposed pulse electrolysis control method and the direct current electrolysis control method. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0021] In order to thoroughly understand the present invention, detailed structures and steps will be presented in the following description, and the application will be further explained in conjunction with the accompanying drawings and specific implementation methods so as to illustrate the technical solutions proposed by the present invention.

[0022] A control method for participating in deep peak regulation of power grid by electrolysis of alkali solution hydrogen of the present invention, wherein an external power grid is connected to a DC circuit via a rectifier circuit, and the output end of the DC circuit is connected to an electrolyzer, and the electric energy of the external power grid is used to perform electrolysis of alkali solution hydrogen production, and the power of electrolysis of alkali solution hydrogen production is controlled to participate in deep peak regulation of power grid. Wherein, the DC circuit topology adopts a structure of two-stage sub-circuits connected in series, including a Buck converter circuit and a pulse generating circuit, wherein the DC output side of the rectifier circuit is connected to the Buck converter circuit, and the Buck converter circuit achieves the purpose of outputting a constant current to supply the next-level DC circuit. At the same time, in order to suppress the grid current ripple caused by the DC side pulse electrolysis current working mode, a capacitor voltage buffering method is adopted. The Buck converter circuit is connected to a pulse generating circuit after the Buck converter circuit, and the pulse generating circuit adopts the topological form of a Boost circuit, and the DC power output by the Buck converter circuit is converted into a pulse wave form to power the electrolyzer. Figure 1 The figure shows the circuit topology and control strategy block diagram of the present invention using Buck converter as the first-stage Buck converter circuit. Figure 1 As shown, the rectifier circuit includes six bridge arm switch tubes d3 and inductors L s The Bick converter circuit includes an inductor L, a polar capacitor C, a fast recovery diode D1, and a field effect transistor d1; the pulse generator circuit includes an inductor L, a fast recovery diode D2, and a field effect transistor d2. The Bick converter circuit and the pulse generator circuit are connected and the inductor is combined so that they share the same inductor. Specifically, the external power grid and the inductor L s The first end of the inductor L sThe second end is connected to the AC port of the six-arm switch tube d3, the DC port of the six-arm switch tube d3 is connected in parallel with the polar capacitor C, the negative electrode of the polar capacitor C is connected to the ground, the positive electrode of the polar capacitor C is connected to the collector of the field effect tube d1, the gate of the field effect tube d1 is connected to the control signal, the source of the field effect tube d1 is connected to the cathode of the fast recovery diode D1, the anode of the fast recovery diode D1 is connected to the ground, the cathode of D1 is also connected to the first end of the inductor L, the second end of the inductor L is connected to the collector of the field effect tube d2 and the anode of the fast recovery diode D2, the source of the field effect tube d2 is connected to the ground, the gate is connected to the control signal, the positive electrode of the hydrogen production equipment-electrolyzer is connected to the cathode of the fast recovery diode D2, and the cathode of the electrolyzer is connected to the ground.

[0023] The present invention discloses a control method for the deep peak regulation of the power grid by using alkaline solution electrolysis to produce hydrogen. The droop control rectifier circuit can realize the frequency response of the power grid and adjust the hydrogen production power. The input current is then converted into a direct current by a Buck converter circuit. In the case of low input power, the input power is minimized to increase the power regulation range, and the electrolyzer is regarded as a load. The power fluctuation of the electrolyzer will profoundly affect the change of the power grid frequency, thereby achieving the purpose of deep peak regulation. Finally, a pulse generating circuit is used to convert the direct current of the inductor L into an output pulse current.

[0024] Specifically, it includes:

[0025] The droop control rectifier circuit is used to achieve frequency response to the power grid and adjust the hydrogen production power:

[0026] When the external grid frequency f≤f min , set the reference input current i of the rectifier circuit dref =0, reference active power P ref =0, the hydrogen production equipment is cut off from the power grid; when the system frequency f≥f max , set the reference input current i of the rectifier circuit dref =i max , reference active power P ref =P N ;i max It indicates the current input from the external power grid to the rectifier circuit under the rated operating conditions of the electrolyzer. min <f<f max When the reference current i of the rectifier circuit is set dref =i0+k*(ff N ), reference active power P ref =P N +k*(ff N ). Among them, i0 is equal to i max , P N is the rated power of the electrolyzer, fN Indicates the rated frequency of the external power grid, f min Indicates the lowest frequency allowed for the hydrogen production circuit to operate, which is determined by the requirements of the external power grid for the grid frequency in various places. max Indicates the maximum frequency allowed for the operation of the hydrogen production equipment, f max Equal to the rated frequency; min Indicates frequency f min Under the condition, the current input from the external power grid to the rectifier circuit. The rectifier circuit adopts i based on the reference value of the rectifier circuit obtained. d -f or Pf droop control. d is the input current of the rectifier circuit, P is the active power, i d Proportional to active power. d -f droop control is an example. Droop control refers to adjusting the power output according to the frequency. Figure 1 As shown, the frequency f and output current of the external power grid are collected in real time. The external grid voltage is maintained at a constant value according to Represents the current input from the external power grid to the electrolyzer, and the active power P can be calculated. PARK transformation is performed. PARK transformation refers to the transformation of phase quantities into d-axis, q-axis and 0-axis variables. Generally, d-axis current represents active current, q-axis current represents reactive current, and 0-axis current represents unbalanced current. Generally, 0-axis current is not considered. In the case of pure active power hydrogen production in the power grid, the output active power P is related to the d-axis input current i d Proportional. d and given i dref After the droop control link, the frequency w and voltage amplitude U can be obtained, and the synthesized three-phase voltage coordinates are transformed to the dq axis to obtain Udref and Uqref. Finally, for the voltage and current double closed-loop control, SPWM generates the driving control signal s3 required for the control of the six-bridge arm switch tube d3, which is input to the six-bridge arm switch tube d3.

[0027] Furthermore, the interharmonics are further suppressed by dividing the modulation wave by the DC side capacitor voltage u, thereby improving the power quality of the power grid. Among them, s3 represents the modulation wave output after droop control, and s'3 represents the modulation wave after being divided by the DC side capacitor voltage u.

[0028] When the external grid frequency is too low, resulting in low active power output, if the traditional DC hydrogen production scheme based on droop control is used, under such low input power, for safety reasons, the electrolyzer needs to be disconnected from the grid. However, the present invention adopts a two-stage DC circuit, such as Figure 1 As shown, the first stage is a Buck converter circuit. When the grid frequency f>f set3 , f set3 is the frequency reference value, f min <f set3 <f max , f set3 Generated by a hysteresis circuit, which generates a reference current I set1 =-k p (u set1 -u), k p represents the control parameter of the proportional link of the Buck converter circuit, u represents the voltage on both sides of the polar capacitor C, and u set1 It represents the reference value of the voltage u on both sides of the polar capacitor C under the control strategy of constant current of the DC inductor L, which is reasonably selected according to the maximum voltage that the voltage on both sides of the polar capacitor C can withstand. Then the current loop control strategy is used to adjust the duty cycle D of the field effect tube d1 in real time. set1 =k l (I set1 -I) as the control signal of field effect transistor d1, k l represents the proportional control parameter of the current loop of the Buck converter circuit, I represents the current of the inductor L, I set1 The reference value indicated; when the grid frequency f<f set4 , f min <f set4 <f set3 By adopting the control strategy of constant current of DC inductor L, I set1 =I op , I op Indicates the pulse current amplitude corresponding to the maximum efficiency, and adjusts the duty cycle D of the field effect tube d1 in real time set1 =k l (I set1 -I). Similarly, when the grid frequency f>f set3 When the second-stage pulse generation circuit adopts a constant duty cycle control strategy, D sset2 =0, when the grid frequency f<f set4 The second-stage pulse generation circuit adopts a control strategy of constant voltage of capacitor C, where the duty cycle of field effect transistor d2 is D set2 =k ll (u set2 -u) as the control signal of field effect transistor d2. ll represents the control parameter of the proportional link of the pulse generating circuit, uset2 It represents the reference value of u under the control strategy of constant voltage of capacitor C, which is reasonably selected according to the maximum voltage that the voltage on both sides of polar capacitor C can withstand, and u represents the voltage on both sides of polar capacitor C. Among them, the switching period of d2 is T2, and the value range of T2 is [0.05s, 0.5s].

[0029] Real-time acquisition of electrolytic cell voltage U ele , at this time, the grid output power is equal to the electrolyzer input power,

[0030] The present invention utilizes the electric energy of an external power grid to produce hydrogen through electrolysis of alkali solution, and participates in the deep peak regulation of the power grid by controlling the power of the hydrogen produced through electrolysis of alkali solution.

[0031] Furthermore, the PWM control signal of the rectifier circuit and the field effect tube d1 adopts a high-frequency modulated carrier, and its switching period is 10 μs.

[0032] Figure 2 The waveform diagram of the input current and voltage of the electrolyzer under the low frequency (48.5Hz) involved in this application shows that under the low frequency condition, the input current and voltage of the electrolyzer appear in the form of pulse waves. In this way, the hydrogen production current of the electrolyzer can be greatly improved.

[0033] Figure 3 The efficiency curve comparison diagram of pulse electrolysis hydrogen production and direct current electrolysis hydrogen production used in this application shows that under low input power conditions, the efficiency of pulse electrolysis is much higher than that of direct current electrolysis, thereby greatly improving the operating range of the electrolyzer, thereby realizing alkaline solution electrolysis hydrogen production to participate in deep peak regulation of the power grid.

[0034] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A control method for participating in deep peak regulation of power grid by hydrogen production through alkaline solution electrolysis, characterized in that: The hydrogen production equipment for producing hydrogen by electrolysis of alkali solution is connected to the external power grid through a circuit, wherein the circuit includes a rectifier circuit, a Buck converter circuit and a pulse generator circuit connected in sequence; the electric energy of the external power grid is used to produce hydrogen by electrolysis of alkali solution, and the power of the hydrogen production by electrolysis of alkali solution is controlled to participate in the deep peak regulation of the power grid, as follows: Real-time collection of the frequency f and output current of the external power grid; The reference value of the rectifier circuit is determined based on the frequency of the external power grid, and the rectifier circuit adopts i based on the obtained reference value. d -f or Pf droop control, where i d is the current of the rectifier circuit, P is the active power; when the external grid frequency f min , set the reference input current i of the rectifier circuit dref =0, reference active power P ref =0, the hydrogen production equipment is cut off from the power grid; when the system frequency f max , set the reference input current i of the rectifier circuit dref =i max , reference active power P ref =P N ;i max It indicates the current input from the external power grid to the rectifier circuit under the rated operating conditions of the hydrogen production equipment. min <f<f max When the reference current i of the rectifier circuit is set dref =i0+k*(ff N ), reference active power P ref =P N +k*(ff N ), where i0 is equal to i max , P N is the rated power of the electrolyzer, f N Indicates the rated frequency of the external power grid, f min Indicates the lowest frequency allowed for the hydrogen production equipment to operate, f max Indicates the maximum frequency allowed for the operation of the hydrogen production equipment, f max Equal to rated frequency; min Indicates frequency f min Under the condition, the current input from the external power grid to the rectifier circuit; The control strategy of the Buck converter circuit is determined based on the frequency of the external power grid, and the Buck converter circuit is controlled. When the power grid frequency f set3 , f set3 is the frequency reference value, f min <f set3 <f max , f set3 The reference current I is generated by the hysteresis circuit. set1 =-k p (u set1 -u), k p represents the control parameter of the proportional link of the Buck converter circuit, u represents the voltage on both sides of the polar capacitor C, and u set1 It represents the reference value of the voltage u on both sides of the polar capacitor C under the control strategy of constant current of the DC inductor L, which is reasonably selected according to the maximum voltage that the voltage on both sides of the polar capacitor C can withstand; then the current loop control strategy is used to adjust the duty cycle D of the field effect tube d1 in the Buck converter circuit in real time. set1 =k l (I set1 -I), k l represents the proportional control parameter of the current loop of the Buck converter circuit, I represents the current of the inductor L in the Buck converter circuit; when the grid frequency f set4 , f min <f set4 <f set3 By adopting the control strategy of constant current of DC inductor L, I set1 =I op , I op Indicates the pulse current amplitude corresponding to the maximum efficiency, and adjusts the duty cycle D of the field effect tube d1 in the Buck converter circuit in real time set1 =k l (I set1 -I); The control strategy of the pulse generating circuit is determined based on the frequency of the external power grid, and the pulse generating circuit is controlled, wherein: when the power grid frequency f set3 When the second-stage pulse generating circuit adopts a constant duty cycle control strategy, the duty cycle D of the field effect tube d2 in the pulse generating circuit is controlled. set2 =0, when the grid frequency f set4 The second-stage pulse generating circuit adopts a control strategy of constant voltage of capacitor C, and controls the duty cycle of field effect transistor d2 in the pulse generating circuit to be D set2 =k ll (u set2 -u); k ll represents the control parameter of the proportional link of the pulse generating circuit, u set2 It represents the reference value of u under the control strategy of constant voltage of capacitor C, which is reasonably selected according to the maximum voltage that the voltage on both sides of the polar capacitor C can withstand.

2. The method according to claim 1, characterized in that The circuit includes six bridge arm switch tubes d3, inductors L s , inductor L, polar capacitor C, fast recovery diode D1, field effect transistor d1, fast recovery diode D2 and field effect transistor d2; the external power grid and inductor L s The first end of the inductor L s The second end is connected to the AC port of the six-arm switch tube d3, the DC output side of the six-arm switch tube d3 is connected in parallel with the polarity capacitor C, the polarity capacitor C is connected in series with the field effect tube d1, the source side of the field effect tube d1 is connected in parallel with the fast recovery diode D1, the cathode side of the fast recovery diode D1 is connected in series with the inductor L, the inductor L is connected in parallel with the field effect tube d2, and the field effect tube d2 is connected in series with the fast recovery diode D2.

3. The method according to claim 1, characterized in that The rectifier circuit uses i based on the reference value obtained d The droop control is performed in any of the droop control modes of -f or Pf, and the modulation wave output after the droop control is divided by the DC side capacitor voltage u in the Buck converter circuit to obtain a modulation wave as a control signal of the rectifier circuit.

4. The method according to claim 1, characterized in that The value range of the period T2 of the PWM control signal of the field effect transistor d2 in the pulse generating circuit is [0.05s, 0.5s].

5. The method according to claim 1, characterized in that The PWM control signal of the field effect tube d1 in the rectifier circuit and the Buck converter circuit adopts a high-frequency modulated carrier.

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