CN-122026400-A - Frequency support control method and system for grid-connected direct current coupling hydrogen production system

CN122026400ACN 122026400 ACN122026400 ACN 122026400ACN-122026400-A

Abstract

The invention discloses a frequency support control method and a frequency support control system of a grid-connected direct current coupling hydrogen production system, which are realized through the following strategies that firstly, self-adaptive virtual thermistor control is combined with alkali liquor electrolytic cells to dynamically adjust control parameters in real time to realize power balance of a plurality of alkali liquor electrolytic cells within a wide temperature range, secondly, a frequency response mechanism maps a power grid frequency signal into a direct current bus voltage signal to drive the alkali liquor electrolytic cells to have no communication response to the power grid frequency requirement, thirdly, a virtual inertia response mechanism improves the response speed in frequency mutation by dynamically correcting a frequency-voltage mapping coefficient and the control parameters, thirdly, voltage safety protection is realized to avoid damage to equipment due to voltage overrun at the ends of the alkali liquor electrolytic cells, and thirdly, air pressure detection protection is used to prevent air pressure jump caused by power consumption mutation from being forward to bad. The invention can realize the decentralization control, improves the hydrogen production efficiency and the frequency modulation performance of the power grid, and is suitable for a renewable energy driven large-scale hydrogen production base.

Inventors

XIA YANGHONG
LI LIMIN
WEI WEI
XU GUIZHI
TENG YUE
WU ZIQIANG

Assignees

浙江大学
国网安徽省电力有限公司

Dates

Publication Date: 20260512
Application Date: 20260413

Claims (10)

1. The frequency support control method of the grid-connected direct current coupling hydrogen production system is characterized by comprising an alternating current-direct current rectifier, a direct current bus and a plurality of alkali liquor electrolytic tank units which are connected in parallel, wherein each alkali liquor electrolytic tank unit is formed by connecting an alkali liquor electrolytic tank with a voltage-reducing direct current-direct current converter in series, and the control method comprises the following steps: (1) The control parameters of each alkali liquor electrolysis cell unit are dynamically adjusted by combining the real-time temperature of each alkali liquor electrolysis cell unit, and the power balance distribution without communication among a plurality of alkali liquor electrolysis cell units is realized within the range of the wide temperature range of the work permitted by the alkali liquor electrolysis cell; (2) The system comprises a frequency response mechanism, an alternating current-direct current rectifier, each alkali liquor electrolysis cell unit, a power control unit and a power control unit, wherein the alternating current-direct current rectifier linearly maps a power grid frequency signal into a direct current bus voltage reference value, and enables the direct current bus voltage to track the reference value through closed loop control; (3) The virtual inertial response mechanism is used for monitoring the frequency change rate of the power grid in real time, dynamically correcting the frequency-voltage mapping coefficient of the alternating current-direct current rectifier and the control parameters of the alkaline electrolysis cell unit so as to improve the response speed of the system to frequency abrupt change; (4) Monitoring terminal voltage of each alkali liquor electrolytic tank in real time, when the terminal voltage exceeds a preset voltage safety threshold value, adjusting down a power reference value of a corresponding alkali liquor electrolytic tank unit, and gradually raising power after the terminal voltage is recovered to be normal; (5) And the air pressure detection protection is to monitor the internal air pressure of each alkali liquor electrolytic tank in real time, when the internal air pressure exceeds a preset air pressure safety threshold value, the power reference value of the corresponding alkali liquor electrolytic tank unit is adjusted downwards, and the power is gradually increased after the internal air pressure is recovered to be normal.
2. The method for controlling the frequency support of the grid-connected direct current coupling hydrogen production system according to claim 1, wherein in the step (1), the wide temperature range is the allowable operating temperature range of the alkaline electrolyzer, and the adjustment of the control parameters is based on the temperature-power coupling characteristic of the alkaline electrolyzer, and increases the electrolysis power when the temperature increases and decreases the electrolysis power when the temperature decreases.
3. The method for controlling frequency support of grid-connected dc-coupled hydrogen production system according to claim 1, wherein in the step (2), the linear mapping of the grid frequency signal to the dc bus voltage reference value specifically includes: when the power grid frequency is in a preset normal interval, the reference value of the DC bus voltage in a steady state linearly changes along with the power grid frequency, and when the power grid frequency exceeds the normal interval, the reference value of the DC bus voltage is fixed to be a preset upper limit value and a preset lower limit value.
4. The method for controlling the frequency support of the grid-connected direct current coupled hydrogen production system according to claim 1, wherein in the step (3), the dynamic correction is realized by setting a sensitivity coefficient and an amplitude limit, the sensitivity coefficient characterizes the response degree of the control parameter correction to the frequency change rate, and the amplitude limit is used for avoiding excessive correction of the control parameter and ensuring the stable and non-overshoot correction process.
5. The method according to claim 4, wherein the frequency-voltage mapping coefficient of the ac-dc rectifier is automatically adjusted according to the change of the frequency change rate of the power grid to map the frequency change rate of the power grid to the dc bus voltage change, the control parameter of the alkaline electrolyzer unit is automatically adjusted according to the dc bus voltage change rate, and the sensitivity coefficient is related to the response degree of the frequency change rate of the power grid and the dc bus voltage change rate during the correction of the frequency-voltage mapping coefficient of the ac-dc rectifier and the control parameter of the alkaline electrolyzer unit, and the amplitude limit is used for preventing the dc bus voltage and the electrolytic power from being out of limit during the response.
6. The method for controlling frequency support of grid-connected direct current coupled hydrogen production system according to claim 1, wherein in the step (4), the voltage safety threshold is set based on rated voltage of the alkaline electrolyzer, and the down-regulating amplitude of the power reference value is matched with the overvoltage degree of the alkaline electrolyzer.
7. The method for controlling the frequency support of a grid-connected direct current coupled hydrogen production system according to claim 1, wherein in the step (5), the air pressure safety threshold is set based on the allowable pressure of the alkaline electrolyzer body, and the down-regulation amplitude of the power reference value is matched with the over-air pressure degree of the alkaline electrolyzer.
8. The method for controlling frequency support of grid-connected direct current coupled hydrogen production system according to claim 1, wherein an ac side of the ac-dc rectifier is connected to a power grid, a dc side of the ac-dc rectifier is connected to a dc bus, a plurality of lye electrolyzer units are connected in parallel to the dc bus, and the step-down dc-dc converter is connected to the dc bus in each of the lye electrolyzer units.
9. The frequency support control method of the grid-connected direct current coupling hydrogen production system according to claim 1, wherein the alkaline electrolyzer is provided with a temperature sensor, a voltage sensor and a pressure sensor, wherein the temperature sensor is used for collecting real-time temperature of the alkaline electrolyzer, the voltage sensor is used for collecting terminal voltage of the alkaline electrolyzer, and the pressure sensor is used for collecting internal pressure of the alkaline electrolyzer.
10. A frequency support control system for implementing the control method of any one of claims 1-9, comprising: The alternating current-direct current rectifier control module is correspondingly connected with the alternating current-direct current rectifier and has the functions of power grid frequency acquisition, frequency-voltage mapping and direct current bus voltage closed-loop control; each alkali liquor electrolysis cell control module is correspondingly connected with one alkali liquor electrolysis cell and a voltage reduction type direct current-direct current converter connected in series with the alkali liquor electrolysis cell, and the alkali liquor electrolysis cell control modules are used for generating control signals based on the real-time temperature and the direct current bus voltage of the alkali liquor electrolysis cell so as to adjust the duty ratio of the voltage reduction type direct current-direct current converter and realize the autonomous adjustment of electrolysis power; the power grid simulation equipment is used for simulating power grid frequency fluctuation and low inertia power grid working conditions and providing a test environment for system frequency support performance verification.

Description

Frequency support control method and system for grid-connected direct current coupling hydrogen production system Technical Field The invention relates to the technical field of new energy hydrogen production and frequency modulation control intersection of an electric power system, in particular to a frequency support control method and system of a grid-connected direct current coupling hydrogen production system. Background The hydrogen energy is used as clean secondary energy, the large-scale preparation of the hydrogen energy becomes a key direction, and the grid-connected direct current coupling hydrogen production system becomes an important supporting device of a high-proportion renewable energy power grid because the hydrogen energy production and the power grid regulation can be simultaneously realized. The alkaline solution electrolyzer is a main stream choice for large-scale hydrogen production due to lower cost and mature technology, but the control strategy of the existing grid-connected direct current coupling hydrogen production system has obvious defects, and is difficult to meet the actual application requirements: (1) The centralized control reliability is insufficient, the cooperative control of the plurality of alkaline solution electrolytic tanks is mostly dependent on a unified control center, single-point fault risks exist, once the control center fails, the whole hydrogen production system is paralyzed, when the hydrogen production base is expanded in scale, a control framework is required to be reconstructed, the flexibility is poor, and the large-scale application scene cannot be adapted. (2) The suitability of the wide temperature range is lacking, that is, the electrolysis capacity (maximum running current) of the alkaline electrolysis tank is strongly related to the temperature, the capacity is increased in a nonlinear way when the temperature is increased and the capacity is reduced when the temperature is reduced within the allowable working temperature range. In the prior art, a control strategy is designed based on the assumption that the temperature of the alkaline solution electrolyzer is constant, and parameters are not dynamically adjusted, so that the alkaline solution electrolyzer is easy to overload and damage at low temperature, the alkaline solution electrolyzer is lightly loaded and has a waste capacity at high temperature, and the hydrogen production efficiency is greatly reduced. (3) The frequency response dynamic performance is weak, the existing grid-connected direct current coupling hydrogen production system mainly adopts pure droop control in the frequency modulation of the power grid, lacks an inertial support mechanism, has large frequency change rate and obvious steady-state deviation when facing sudden change of the frequency of the power grid (such as load switching and renewable energy power fluctuation), cannot meet the requirement of the power grid on the frequency modulation dynamic index, does not establish a communication-free mapping mechanism of frequency-direct current bus voltage-alkali liquid electrolytic tank current, and has the defects that a plurality of alkali liquid electrolytic tanks cannot synchronously respond to the frequency requirement and the frequency modulation efficiency is low. (4) The existing control strategy does not design special protection for the voltage safety of the alkaline electrolytic tank, and when the voltage of the alkaline electrolytic tank end exceeds a rated value due to fluctuation of electrolytic power, faults such as electrode ablation, diaphragm damage and the like are easily caused, so that the service life of equipment is shortened, and the operation and maintenance cost is increased. (5) In addition, the existing collaborative optimization method of a plurality of alkaline solution electrolytic tanks focuses on an energy management level, aims at long-term matching of source side power and hydrogen production requirements, omits the bottom control problems of cold start, wide temperature fluctuation and the like, and meanwhile, traditional frequency modulation resource research focuses on photovoltaic and energy storage systems, and a self-adaptive adjustment mechanism aiming at capacity change of the alkaline solution electrolytic tanks is still blank. Therefore, a control scheme of a grid-connected direct current coupling hydrogen production system with decentralization, wide temperature range adaptation, high dynamic response and safety protection is needed, the power distribution of a power grid frequency support and a plurality of alkaline electrolytic tanks is balanced, and the reliability and the operation efficiency of the system are improved. Disclosure of Invention The invention aims to provide a frequency support control method and system for a grid-connected direct current coupling hydrogen production system, aiming at the defects of the prior art. The grid-connected direct current couplin