Alkaline electrolytic water hydrogen production power supply system

Abstract

The invention relates to the technical field of hydrogen production power supplies, in particular to an alkaline water electrolysis hydrogen production power supply system. Comprising an energy storage battery, a first DC / DC converter, a second DC / DC converter, an AC / DC converter, a first switch, a second switch, a third switch and a series compensation capacitor, the AC / DC converter realizes a function of converting alternating current of a power grid into direct current, the first DC / DC converter realizes a function of converting direct current into direct current, the second DC / DC converter realizes a function of converting direct current into direct current, and the series compensation capacitor realizes a function of converting direct current into direct current. And the series compensation capacitor realizes an additional reactive compensation function. Reactive power compensation is realized by adding the series compensation capacitor, rapid drop of power grid voltage is avoided, and stability of system voltage is guaranteed. The DC / DC is bypassed by closing the isolating switch, and the hydrogen production electrolytic bath is directly driven by the AC / DC, so that the utilization efficiency of electric energy is improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production power supply, in particular to an alkaline water electrolysis hydrogen production power supply system. Background Art

[0002] Most of the existing hydrogen production power supply systems are composed of wind power generation systems, photovoltaic power generation systems, AC / DC converters, and DC / DC converters. The power source of the hydrogen production tank consists of two parts. The first part: the photovoltaic power generation system, wind power generation system, and energy storage system use string AC / DC ( Figure 1 AC / DC in), DC / DC ( Figure 1 DC / DC2) connected to a centralized DC / DC ( Figure 1 The input end of the DC / DC1 in the figure; the second part uses AC / DC to connect the grid to the input end of the centralized DC / DC; the output end of the centralized DC / DC is connected to the electrolyzer to electrolyze water to obtain hydrogen. This system generally uses an AC / DC converter connected to the grid to manage reactive power, but due to the capacity of the AC / DC converter itself, its ability to output reactive power is weak. When the grid has a large reactive power demand, such as a voltage drop, the AC / DC converter is difficult to provide sufficient reactive power to support grid voltage recovery.

[0003] The reactive power compensation capability of the existing hydrogen production power supply system is limited by the capacity of the AC / DC converter. To improve the compensation capability, the capacity of the converter must be increased, which is costly. In addition, the existing hydrogen production power supply system usually uses centralized DC / DC to directly drive the hydrogen production electrolyzer and complete the cold start, which has a low power utilization rate. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides an alkaline water electrolysis hydrogen production power supply system, which optimizes the existing hydrogen production power supply scheme by adding a series compensation capacitor, realizes reactive power compensation, avoids rapid drop of grid voltage, and ensures system voltage stability.

[0005] In order to solve the technical problem, the technical solution adopted by the present invention is: an alkaline water electrolysis hydrogen production power supply system, including an energy storage battery, a first DC / DC converter, a second DC / DC converter, an AC / DC converter, a first switch, a second switch, a third switch and a series compensation capacitor; The AC / DC converter has an AC side connected to the AC bus of the power grid, and a DC side connected to the DC bus, and is used to convert the AC power of the power grid into DC power; The series compensation capacitor is connected to the DC bus through a first switch. When additional reactive power is required, the first switch is closed to achieve additional reactive power compensation. The input end of the first DC / DC converter is connected to the DC bus, and the output end is connected to the electrolyzer through the second switch, so as to realize the cold start of the electrolyzer; The third switch is connected in parallel between the input end and the output end of the first DC / DC converter. When the electrolytic cell is started, the third switch is closed, the first DC / DC converter stops running, and the DC bus directly drives the electrolytic cell. The input end of the second DC / DC converter is connected to the energy storage battery, and the output end is connected to the DC bus, so as to realize the mutual conversion between electrical energy and chemical energy.

[0006] Furthermore, the process of the system working in the hydrogen production mode is as follows: the AC / DC module detects the voltage and current of the AC bus of the power grid, calculates the active power P and reactive power Q of the AC bus of the power grid, and if it is determined based on the active power P and reactive power Q that the grid voltage is normal and the energy storage battery does not need to be charged / discharged, the electrolyzer is turned on to produce hydrogen; The steps to achieve hydrogen production mode are: S11, disconnecting the first switch connected to the series compensation capacitor; S12, operating the second DC / DC converter to charge the energy storage battery, and after the battery is fully charged, the second DC / DC converter stops operating; S13, closing the second switch connected to the hydrogen production electrolyzer, starting the first DC / DC converter, the electric energy flows from the DC bus to the hydrogen production electrolyzer through the first DC / DC converter, the output voltage of the first DC / DC converter starts to rise from 0V to the rated voltage of the electrolyzer, and the electrolyzer is cold started; S14, the first DC / DC converter stops running, the third switch is closed, and the electric energy flows directly to the hydrogen production electrolyzer through the third switch, so that the DC bus directly drives the electrolyzer.

[0007] Furthermore, when the reactive power Q is less than or equal to the set threshold T and meets the grid dispatching requirements, it is considered that the grid voltage is normal and there is no need to charge / discharge the energy storage battery.

[0008] Furthermore, the process of the system working in the reactive support mode is as follows: the AC / DC module detects the voltage and current of the AC bus of the power grid, calculates the active power P and reactive power Q of the AC bus of the power grid, and if it is found that the voltage drop depth of the power grid is high according to the active power P and reactive power Q, the electrolytic cell is turned off and the series compensation capacitor is switched on; The steps to achieve reactive support mode are: S21, the hydrogen production electrolyzer stops operating; S22, disconnect the second switch; S23, disconnect the third switch; S24, the second DC / DC converter stops running; S25. Determine the compensation capacity according to the active power P and reactive power Q of the AC bus of the power grid. If the compensation capacity is greater than the capacity of the AC / DC converter, close the first switch and put the series compensation capacitor into operation. Additional reactive power compensation is added through the series compensation capacitor. The reactive current flows from the series compensation capacitor through the DC bus to the AD / DC converter, and then flows from the AC / DC converter to the power grid.

[0009] Furthermore, if Q is greater than the set threshold T, it is considered that the grid voltage drop depth is high.

[0010] Furthermore, when it is necessary to meet the power grid flow control requirements, the system works in the dispatching mode, and the energy storage battery transmits electric energy to the grid through the second DC / DC converter and the AC / DC converter; The process of implementing the scheduling mode is: S31, the hydrogen production electrolyzer stops operating; S32, disconnect the second switch; S33, disconnect the third switch; S34, starting the second DC / DC converter, and releasing electric energy from the energy storage battery to the DC bus; S35, start the AC / DC converter, and transfer energy from the DC bus to the AC bus of the power grid.

[0011] Furthermore, the set threshold T is 30% of the capacity of the AC / DC converter.

[0012] Furthermore, the first switch, the second switch and the third switch are all isolating switches.

[0013] Beneficial effects of the present invention: The present invention provides an alkaline water electrolysis hydrogen production power supply system, which optimizes the existing hydrogen production power supply scheme by adding a series compensation capacitor, realizes reactive power compensation, avoids the rapid drop of the grid voltage, and ensures the stability of the system voltage. The present invention calculates the active power and reactive power of the system by detecting the voltage and current of the AC / DC grid connection point connected to the grid. When the grid voltage is normal and there is no need to charge / discharge the energy storage, the electrolyzer can be turned on to produce hydrogen; when it is necessary to meet the grid flow control requirements, the energy storage battery transmits electricity to the grid through DC / DC and AC / DC, and the hydrogen production electrolyzer is turned off at this time. When the grid needs to provide a large reactive support (such as a high grid voltage drop depth), and AC / DC can hardly meet the reactive power required to be provided, the hydrogen production electrolyzer is turned off, and the series compensation capacitor is switched on to provide additional reactive support to maintain the stability of the grid voltage. The present invention realizes the cold start of the hydrogen production electrolyzer through the first DC / DC converter, bypasses the first DC / DC converter by closing the third switch, uses AC / DC to directly drive the hydrogen production electrolyzer, stops the first DC / DC converter from running, and improves the efficiency of electric energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the principle block diagram of the alkaline water electrolysis hydrogen production power supply system; Figure 2 It is a schematic diagram of the hydrogen production power supply system in the hydrogen production mode; Figure 3 It is a schematic diagram of the hydrogen production power supply system in reactive power support mode; Figure 4 Schematic diagram of the hydrogen production power system in scheduling mode. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0016] Example 1 This embodiment discloses an alkaline water electrolysis hydrogen production power supply system, such as Figure 1 As shown, it includes an energy storage battery, a first DC / DC converter, a second DC / DC converter, an AC / DC converter, a first switch, a second switch, a third switch and a series compensation capacitor. In Figure 1, the first DC / DC converter is represented by DC / DC1, the second DC / DC converter is represented by DC / DC2, the first switch is an isolating switch, represented by K1, the second switch is an isolating switch, represented by K2, the third switch is an isolating switch, represented by K3, the AC / DC converter is represented by AC / DC, and the AC bus of the power grid is represented by PCC.

[0017] The AC / DC converter realizes the function of converting the AC power of the power grid into DC power, the first DC / DC converter realizes the function of converting DC power into DC power, the second DC / DC converter realizes the function of converting DC power into DC power, and the series compensation capacitor realizes the function of additional reactive power compensation.

[0018] The connection relationship between the components is: The AC side of the AC / DC converter is connected to the AC busbar PCC of the power grid, and the DC side is connected to the DC busbar, and is used to convert the AC power of the power grid into DC power; The series compensation capacitor is connected to the DC bus through the first switch. When additional reactive power is needed, the first switch is closed to achieve additional reactive power compensation; the additional power refers to the reactive power in the power grid minus the maximum reactive power that the AC / DC can output. In other words, the AC / DC converter cannot compensate the reactive power in the power grid to 0, and additional reactive power is required to compensate. Additional reactive power is a concept that can be directly derived by people in this field in this context, so it is not described in the claims.

[0019] The input end of the first DC / DC converter is connected to the DC bus, and the output end is connected to the electrolyzer through the second switch, so as to realize the cold start of the electrolyzer; The third switch is connected in parallel between the input end and the output end of the first DC / DC converter. When the electrolytic cell is started, the third switch is closed, the first DC / DC converter stops running, and the DC bus directly drives the electrolytic cell. The input end of the second DC / DC converter is connected to the energy storage battery, and the output end is connected to the DC bus, so as to realize the mutual conversion between electrical energy and chemical energy.

[0020] The operation strategy of the hydrogen production power supply system described in this embodiment is: (1) Hydrogen production mode. The power flow and switch status are as follows: Figure 2 The AC / DC converter detects the voltage and current of the PCC and calculates the active power P and reactive power Q of the PCC. If Q is less than or equal to 30% of the AC / DC capacity, the following steps are performed while meeting the grid dispatch requirements: S11, disconnecting the isolating switch K1 connected to the series compensation capacitor; S12, running DC / DC2 to charge the energy storage battery, that is, consuming the power of the power grid to charge the energy storage battery. After the battery is fully charged, DC / DC2 stops running; S13, close the isolating switch K2 connected to the hydrogen production electrolyzer, start DC / DC1, and the electric energy flows from the DC bus to the hydrogen production electrolyzer through DC / DC1. The output voltage of DC / DC1 starts to rise from 0V to the rated voltage of the electrolyzer; S14, DC / DC1 stops running, and the disconnector K3 is closed. The electric energy flows directly to the hydrogen production electrolyzer through the disconnector K3, thereby improving the utilization efficiency of the electric energy.

[0021] In this embodiment, the grid dispatching requirements are met when the grid dispatching instruction requires the system to send a specific power to the grid, the system will immediately respond to the grid dispatching instruction, adjust the system working state according to the instruction requirements, and meet the grid requirements. Grid dispatching instructions generally include: sending fixed active power to the grid, absorbing fixed active power of the grid, and providing capacitive reactive power support to the grid.

[0022] (2) Reactive power support mode. The power flow direction and switch status are as follows: Figure 3 The AC / DC converter detects the voltage and current of the PCC and calculates the active power P and reactive power Q of the PCC. If Q is greater than 30% of the AC / DC capacity, the following steps are performed: S21, the hydrogen production electrolyzer stops operating; S22, disconnect the isolating switch K2; S23, disconnect the isolating switch K3; S24, DC / DC2 stops running; S25. Determine the compensation capacity according to the active power P and reactive power Q of the PCC. If the compensation capacity is greater than the capacity of the AC / DC converter, close the isolating switch K1, put the series compensation capacitor into operation, increase the additional reactive compensation, and the reactive current flows from the AC / DC to the grid.

[0023] In this embodiment, the process of determining the compensation capacity according to the active power P and reactive power Q of the PCC is as follows: Assuming that the power factor of the power grid is to be Controlled to 0.97, and the reactive power in the current power grid is inductive, Calculate the reactive power when the power factor is 0.97 , the required compensation capacity is capacitive reactive power, which is the absolute value of Q1-Q. Calculating the compensation capacity is a conventional technical means in the art, and this embodiment is only used as an example.

[0024] (3) Dispatching mode. The power flow and switch status are as follows: Figure 4 As shown, the power grid increases active output due to scheduling needs and performs the following steps: S31, the hydrogen production electrolyzer stops operating; S32, disconnect the isolating switch K2; S33, disconnect the isolating switch K3; S34, start DC / DC2, and release electric energy from the energy storage battery to the DC bus; S35, start AC / DC, and transfer energy from DC bus to PCC bus.

[0025] The present invention provides an alkaline water electrolysis hydrogen production power supply system, which optimizes the existing hydrogen production power supply scheme by adding a series compensation capacitor, realizes reactive power compensation, avoids the rapid drop of the grid voltage, and ensures the stability of the system voltage. The technical problems to be solved by this patent are as follows: by detecting the voltage and current of the AC / DC grid connection point connected to the grid, the active power and reactive power of the system are calculated. When the grid voltage is normal and there is no need to charge / discharge the energy storage, the electrolyzer can be turned on to produce hydrogen; when it is necessary to meet the grid flow control requirements, the energy storage battery transmits electricity to the grid through DC / DC and AC / DC, and the hydrogen production electrolyzer is turned off at this time. When the grid needs to provide a large reactive support (such as a high grid voltage drop depth), and AC / DC is difficult to meet the reactive power required, the hydrogen production electrolyzer is turned off, and the series compensation capacitor is switched on to provide additional reactive support to maintain the grid voltage stability.

[0026] The above description is only the basic principle and preferred embodiments of the present invention. Improvements and substitutions made by those skilled in the art based on the present invention belong to the protection scope of the present invention.

Claims

1. An alkaline water electrolysis hydrogen production power supply system, characterized in that: It includes an energy storage battery, a first DC / DC converter, a second DC / DC converter, an AC / DC converter, a first switch, a second switch, a third switch and a series compensation capacitor; The AC / DC converter has an AC side connected to the AC bus of the power grid, and a DC side connected to the DC bus, and is used to convert the AC power of the power grid into DC power; The series compensation capacitor is connected to the DC bus through a first switch. When additional reactive power is required, the first switch is closed to achieve additional reactive power compensation. The input end of the first DC / DC converter is connected to the DC bus, and the output end is connected to the electrolyzer through the second switch, so as to realize the cold start of the electrolyzer; The third switch is connected in parallel between the input end and the output end of the first DC / DC converter. When the electrolytic cell is started, the third switch is closed, the first DC / DC converter stops running, and the DC bus directly drives the electrolytic cell. The input end of the second DC / DC converter is connected to the energy storage battery, and the output end is connected to the DC bus, so as to realize the mutual conversion between electrical energy and chemical energy.

2. The alkaline water electrolysis hydrogen production power supply system according to claim 1, characterized in that: The process of this system working in hydrogen production mode is as follows: the AC / DC module detects the voltage and current of the AC bus of the power grid, calculates the active power P and reactive power Q of the AC bus of the power grid, and if it is determined based on the active power P and reactive power Q that the grid voltage is normal and the energy storage battery does not need to be charged / discharged, the electrolyzer is turned on to produce hydrogen; The steps to achieve hydrogen production mode are: S11, disconnecting the first switch connected to the series compensation capacitor; S12, operating the second DC / DC converter to charge the energy storage battery, and after the battery is fully charged, the second DC / DC converter stops operating; S13, closing the second switch connected to the hydrogen production electrolyzer, starting the first DC / DC converter, the electric energy flows from the DC bus to the hydrogen production electrolyzer through the first DC / DC converter, the output voltage of the first DC / DC converter starts to rise from 0V to the rated voltage of the electrolyzer, and the electrolyzer is cold started; S14, the first DC / DC converter stops running, the third switch is closed, and the electric energy flows directly to the hydrogen production electrolyzer through the third switch, so that the DC bus directly drives the electrolyzer.

3. The alkaline water electrolysis hydrogen production power supply system according to claim 2, characterized in that: When the reactive power Q is less than or equal to the set threshold T and meets the grid dispatching requirements, the grid voltage is considered normal and there is no need to charge / discharge the energy storage battery.

4. The alkaline water electrolysis hydrogen production power supply system according to claim 1, characterized in that: The process of this system working in reactive support mode is as follows: the AC / DC module detects the voltage and current of the AC bus of the power grid, calculates the active power P and reactive power Q of the AC bus of the power grid, and if it is found that the voltage drop depth of the power grid is high according to the active power P and reactive power Q, the electrolytic cell is turned off and the series compensation capacitor is switched on; The steps to achieve reactive support mode are: S21, the hydrogen production electrolyzer stops operating; S22, disconnect the second switch; S23, disconnect the third switch; S24, the second DC / DC converter stops running; S25. Determine the compensation capacity according to the active power P and reactive power Q of the AC bus of the power grid. If the compensation capacity is greater than the capacity of the AC / DC converter, close the first switch and put the series compensation capacitor into operation. Additional reactive power compensation is added through the series compensation capacitor. The reactive current flows from the series compensation capacitor through the DC bus to the AD / DC converter, and then flows from the AC / DC converter to the power grid.

5. The alkaline water electrolysis hydrogen production power supply system according to claim 4, characterized in that: If Q is greater than the set threshold T, it is considered that the grid voltage drop depth is high.

6. The alkaline water electrolysis hydrogen production power supply system according to claim 1, characterized in that: When the power grid flow control requirements need to be met, the system works in the dispatching mode, and the energy storage battery transmits electric energy to the grid through the second DC / DC converter and the AC / DC converter; The process of implementing the scheduling mode is: S31, the hydrogen production electrolyzer stops operating; S32, disconnect the second switch; S33, disconnect the third switch; S34, starting the second DC / DC converter, and releasing electric energy from the energy storage battery to the DC bus; S35, start the AC / DC converter, and transfer energy from the DC bus to the AC bus of the power grid.

7. The alkaline water electrolysis hydrogen production power supply system according to claim 3 or 5, characterized in that: The set threshold T is 30% of the capacity of the AC / DC converter.

8. The alkaline water electrolysis hydrogen production power supply system according to any one of claims 1 to 6, characterized in that: The first switch, the second switch and the third switch are all isolating switches.

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