CN117713547B - Bidirectional reversible new energy hydrogen production system based on phase-shifting transformer - Google Patents
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- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 65
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 64
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 37
- 230000002457 bidirectional effect Effects 0.000 title claims abstract description 25
- 230000002441 reversible effect Effects 0.000 title claims abstract description 15
- 238000010248 power generation Methods 0.000 claims abstract description 51
- 238000004146 energy storage Methods 0.000 claims abstract description 43
- 230000005540 biological transmission Effects 0.000 claims abstract description 7
- 230000001105 regulatory effect Effects 0.000 claims description 25
- 238000004804 winding Methods 0.000 claims description 15
- 239000000446 fuel Substances 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 10
- 238000003860 storage Methods 0.000 claims description 9
- 230000005611 electricity Effects 0.000 claims description 7
- 230000008859 change Effects 0.000 claims description 4
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- 238000011217 control strategy Methods 0.000 abstract description 12
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
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- 239000003990 capacitor Substances 0.000 description 2
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- 239000002699 waste material Substances 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
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- 230000002708 enhancing effect Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
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Abstract
The invention discloses a bidirectional reversible new energy hydrogen production system based on a phase-shifting transformer, which relates to the technical field of new energy, and comprises a grid-connected unit, a direct current bus, a new energy power generation unit and an energy storage unit, wherein the grid-connected unit is used for carrying out power exchange between the direct current bus and a power grid, the new energy power generation unit supplies power for the direct current bus, the energy storage unit is used for preparing and storing hydrogen by utilizing the electric energy of the direct current bus in a hydrogen production mode, and the stored hydrogen is used for generating power for the direct current bus in a power generation mode; and defining a working interval based on the rated voltage of the direct current bus, and selecting a control strategy of a grid-connected unit, a new energy power generation unit and an energy storage unit in the system according to the working interval where the voltage value of the current direct current bus is located. The system has the characteristics of high grid-connected transmission quality, small internal voltage fluctuation and high transmission efficiency, realizes the on-site consumption of new energy power generation, stabilizes the load fluctuation of the power grid, and is convenient for popularization and application of new energy and renewable energy power generation.
Description
Technical Field
The invention relates to the technical field of new energy, in particular to a bidirectional reversible new energy hydrogen production system based on a phase-shifting transformer.
Background
The new energy and renewable energy are used for generating electricity, and the method has important significance for enhancing the energy supply capability, relieving the energy demand pressure, optimizing the energy structure, protecting the natural environment and promoting the sustainable development of economy and society.
However, the existing new energy power generation technologies, such as wind power generation, solar power generation and the like, generally have geographic distribution non-uniformity, inherent intermittence and fluctuation of power generation output, and generally cause the problem of power generation and absorption of new energy sources such as 'waste wind and waste light'; in addition, the inherent self-regulation capability of new energy power generation is insufficient, and the frequency stability and the voltage stability of grid connection are also insufficient, so that the stable operation of the existing power grid is greatly impacted.
Therefore, how to realize the on-site consumption of new energy power generation and stabilize the load fluctuation of the power grid is a problem which needs to be solved by the technicians in the field.
Disclosure of Invention
In view of the above, the invention provides a bidirectional reversible new energy hydrogen production system based on a phase-shifting transformer, which is connected with a new energy power generation unit, an energy storage unit and a power grid by adopting a phase-shifting rectification technology, and is internally used for carrying out power transmission based on a direct current bus and regulating and controlling the new energy power generation unit, the energy storage unit and the grid connection unit according to the voltage of the direct current bus, so that the on-site absorption of new energy power generation is realized and the load fluctuation of the power grid is stabilized.
In order to achieve the above object, the present invention provides the following technical solutions:
The invention discloses a bidirectional reversible new energy hydrogen production system based on a phase-shifting transformer, which comprises: the system comprises a grid-connected unit, a direct current bus, a new energy power generation unit and an energy storage unit;
The AC end of the grid-connected unit is connected with a power grid, and the DC end of the grid-connected unit is connected with the direct current bus and is used for exchanging electric energy between the direct current bus and the power grid;
The output end of the new energy power generation unit is connected with the direct current bus to provide electric energy for the direct current bus;
The energy storage unit is connected with the direct current bus, hydrogen is prepared by using electric energy of the direct current bus and stored in the hydrogen production mode of the energy storage unit, and the stored hydrogen is used for generating electricity to provide electric energy for the direct current bus in the electricity generation mode of the energy storage unit;
And defining a working interval based on the rated voltage of the direct current bus, and selecting a control strategy of a grid-connected unit, a new energy power generation unit and an energy storage unit in the system according to the working interval where the voltage value of the current direct current bus is located.
Further, the grid-connected unit comprises a phase shifting transformer and an NPC three-level rectifier;
the phase-shifting transformer main winding is connected with a power grid, the auxiliary winding is connected with the AC end of the NPC three-level rectifier, and the phase difference between the main winding and the auxiliary winding is controlled by adjusting the connection mode of the auxiliary winding or the coupling magnetic flux of the phase-shifting converter, so that the power flow direction and the voltage are controlled;
The NPC three-level rectifier DC end is connected with the direct current bus, and the NPC three-level rectifier logically controls a power switch device according to a switch sequence to generate three phase voltage levels, and synthesizes alternating current at an AC end.
Further, the new energy power generation unit comprises a photovoltaic unit and a wind power unit, wherein the photovoltaic unit is connected with the direct current bus through a DC/DC converter, and the wind power unit is connected with the direct current bus through an NPC three-level converter.
Further, the DC/DC converter is a Boost converter; the photovoltaic unit adopts an MPPT control method to control electric energy output, and comprises the following steps:
Step 1: obtaining output voltage U PV 0 and output current i PV 0 at the initial moment of the photovoltaic array, and inputting the output voltage U PV 0 and the output current i PV 0 into an MPPT algorithm module;
Step 2: the MPPT algorithm module calculates initial output power P 0 of the photovoltaic array, randomly generates disturbance voltage delta U 0, and outputs a reference value U ref of voltage to a PI regulator according to U PV 0 and delta U 0, wherein the absolute value of delta U 0 is smaller than 0.5% of U PV;
Step 3: the PI regulator outputs a switching signal of a power switching tube of the Boost converter after passing through a PWM modulator according to the U ref, so as to regulate the electric energy output of the photovoltaic array;
Step 4: obtaining output voltage U PV and output current i PV of the photovoltaic array at the current moment, and inputting the output voltage U PV and the output current i PV into an MPPT algorithm module;
Step 5: the MPPT algorithm module calculates the output power P of the photovoltaic array at the current moment and the change delta P of the power P-of the photovoltaic array at the previous moment, determines the application of a tiny disturbance voltage delta U to the U PV according to the disturbance voltage delta U-applied at the previous moment, and outputs a reference value U ref of the voltage to the PI regulator according to U PV and delta U;
step 6: and repeatedly executing the steps 3-5.
Further, in the step 5,
When the delta P >0, delta U- >0 is delta U >0, and delta U- <0 is delta U <0;
When Δp <0, Δu - >0 is Δu <0, and Δu - <0 is Δu >0.
Further, the energy storage unit includes: a bidirectional DC/DC converter, an electrolytic tank, a compressor, a storage tank and a fuel cell;
The front stage of the bidirectional DC/DC converter is the direct current bus, and the rear stage is the electrolytic tank or the hydrogen fuel cell; in the hydrogen production mode, the electrolyzer electrolyzes and generates hydrogen by utilizing the electric energy provided by the bidirectional DC/DC converter, and stores the hydrogen into the storage tank through the compressor; in the power generation mode, the hydrogen fuel cell generates power using hydrogen in the storage tank and supplies power to the bidirectional DC/DC converter.
Further, the voltage and power transmission control strategy of the direct current bus is as follows:
Setting the rated voltage value of the direct current bus as U bus when the system operates normally, setting the voltage value of the direct current bus as U now, setting the state of charge of the fuel cell as SOC, setting the power generation power of the new energy power generation unit as PPV and setting the power consumed by hydrogen production as PL;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit when the SOC is 1.05U bus<Unow≤1.1Ubus, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid, wherein the new energy power generation unit adopts a constant power mode; if SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the energy storage unit to work in a hydrogen production mode to charge at constant current and constant voltage;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit when the SOC is 1.02U bus<Unow≤1.05Ubus, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid, wherein the new energy power generation unit adopts an MPPT working mode; the SOC is less than 0.1, the new energy unit is used for regulating the voltage of the direct current bus, and the energy storage unit works in a hydrogen production mode and is charged with constant current and constant voltage;
when the voltage of the direct current bus is 0.98U bus<Unow≤1.02Ubus, the voltage of the direct current bus is basically kept unchanged, the grid-connected unit regulates the voltage of the direct current bus, and the photovoltaic unit is switched to an MPPT control mode;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit, releasing power to the direct current bus in a constant voltage mode, enabling the grid-connected unit to absorb grid-connected power from the direct current bus to a power grid, and enabling the new energy power generation unit to adopt an MPPT working mode; if SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the energy storage unit to work in a hydrogen production mode to charge at constant current and constant voltage;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid, wherein the new energy power generation unit adopts an MPPT working mode; and if the SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid.
Compared with the prior art, the bidirectional reversible new energy hydrogen production system based on the phase-shifting transformer is provided, and the hydrogen production system and the power grid are connected by adopting a phase-shifting rectification technology, so that the bidirectional reversible new energy hydrogen production system has the advantages of high power factor and small harmonic wave, and improves the output power quality of the system; the system adopts a direct current common bus, the voltage fluctuation of the bus is small, the frequency of electric energy conversion is small, the equipment investment is low, and the transmission efficiency is high; compared with the existing hydrogen production system, the invention has low cost and small loss, and the electric energy conversion efficiency can reach more than 96 percent; the system meets the grid-connected power generation requirement of the hydrogen fuel cell, realizes the on-site consumption of new energy power generation, stabilizes the load fluctuation of the power grid, and is convenient for popularization and application of new energy and renewable energy power generation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a system according to the present invention.
Fig. 2 is an NPC converter topology.
Fig. 3 is a bi-directional DC/DC converter topology.
Fig. 4 is a photovoltaic DC/DC converter topology.
Fig. 5 is a schematic diagram of a photovoltaic MPPT control strategy.
Fig. 6 is a schematic diagram of a charge-discharge control strategy for a bi-directional DC/DC converter.
Fig. 7 is a schematic diagram of a control strategy of the phase-shifting rectification grid-connected system.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention discloses a bidirectional reversible new energy hydrogen production system based on a phase-shifting transformer, which is shown in figure 1 and comprises the following steps: the system comprises a grid-connected unit, a direct current bus, a new energy power generation unit and an energy storage unit;
the AC end of the grid-connected unit is connected with the power grid, and the DC end of the grid-connected unit is connected with a direct current bus and is used for exchanging electric energy between the direct current bus and the power grid;
the output end of the new energy power generation unit is connected with the direct current bus to provide electric energy for the direct current bus;
The energy storage unit is connected with the direct current bus, hydrogen is prepared and stored by using the electric energy of the direct current bus in the hydrogen production mode, and the stored hydrogen is used for generating electricity to provide electric energy for the direct current bus in the electricity generation mode of the energy storage unit;
and defining a working interval based on the rated voltage of the direct current bus, and selecting a control strategy of a grid-connected unit, a new energy power generation unit and an energy storage unit in the system according to the working interval where the voltage value of the current direct current bus is located.
In a specific embodiment, the grid-connected unit comprises a phase shifting transformer and an NPC three-level rectifier;
the main winding of the phase-shifting transformer is connected with a power grid, the auxiliary winding is connected with the AC end of the NPC three-level rectifier, and the phase difference between the main winding and the auxiliary winding is controlled by adjusting the connection mode of the auxiliary winding or the coupling magnetic flux of the phase-shifting converter, so that the power flow direction and the voltage are controlled;
The DC end of the NPC three-level rectifier is connected with a direct current bus, the NPC three-level rectifier logically controls a power switch device according to a switch sequence to generate three phase voltage levels, and the three phase voltage levels are combined into alternating current at an AC end.
In a specific embodiment, the new energy power generation unit comprises a photovoltaic unit and a wind power unit, wherein the photovoltaic unit is connected with the direct current bus through a DC/DC converter, and the wind power unit is connected with the direct current bus through an NPC three-level converter.
In a specific embodiment, the DC/DC converter is a Boost converter; the photovoltaic unit adopts an MPPT control method to control electric energy output, and comprises the following steps:
Step 1: obtaining output voltage U PV 0 and output current i PV 0 at the initial moment of the photovoltaic array, and inputting the output voltage U PV 0 and the output current i PV 0 into an MPPT algorithm module;
Step 2: the MPPT algorithm module calculates initial output power P 0 of the photovoltaic array, randomly generates disturbance voltage DeltaU 0, and outputs a reference value U ref of voltage to the PI regulator according to U PV 0 and DeltaU 0, wherein the absolute value of DeltaU 0 is smaller than 0.5% of U PV;
step 3: the PI regulator outputs a switching signal of a power switching tube of the Boost converter after passing through the PWM modulator according to U ref, so that the electric energy output of the photovoltaic array is regulated;
Step 4: obtaining the output voltage UPV and the output current i PV of the photovoltaic array at the current moment, and inputting the output voltage UPV and the output current i PV into an MPPT algorithm module;
Step 5: the MPPT algorithm module calculates the output power P of the photovoltaic array at the current moment and the change delta P of the power P - of the photovoltaic array at the previous moment, determines the application of a tiny disturbance voltage delta U to U PV according to the disturbance voltage delta U - applied at the previous moment, and outputs a reference value U ref of the voltage to the PI regulator according to U PV and the delta U;
step 6: and repeatedly executing the steps 3-5.
In a specific embodiment, in step 5,
When DeltaP >0, deltaU- >0 is DeltaU >0, deltaU- <0 is DeltaU <0;
When DeltaP <0, deltaU- >0 is DeltaU <0, deltaU- <0 is DeltaU >0.
In a specific embodiment, the energy storage unit comprises: a bidirectional DC/DC converter, an electrolytic tank, a compressor, a storage tank and a fuel cell;
the front stage of the bidirectional DC/DC converter is a direct current bus, and the rear stage is an electrolytic tank or a hydrogen fuel cell; in the hydrogen production mode, the electrolyzer electrolyzes and generates hydrogen by utilizing the electric energy provided by the bidirectional DC/DC converter, and stores the hydrogen into the storage tank through the compressor; in the power generation mode, the hydrogen fuel cell generates power using hydrogen in the storage tank and supplies power to the bi-directional DC/DC converter.
In one specific embodiment, the voltage and power transmission control strategy for the dc bus is as follows:
Setting the rated voltage value of a direct current bus as U bus when the system operates normally, setting the voltage value of the direct current bus as U now, setting the state of charge of a fuel cell as SOC, setting the power generated by a new energy power generation unit as PPV and setting the power consumed by hydrogen production as PL; when the PPV is far greater than PL, the dc bus voltage will be continuously raised due to power saturation, so that the dc bus voltage exceeds the safety threshold value of 1.05U bus and approaches the upper limit of 1.1U bus of the dc bus voltage, at this time, the new energy power generation unit must be switched to the fixed power mode, and the grid-connected unit releases the maximum grid-connected power from the dc bus to the power grid, so as to protect the operation safety of the system.
When the SOC is more than or equal to 0.1, when the SOC is 1.05U bus<Unow≤1.1Ubus, the energy storage unit is used for adjusting the voltage of the direct current bus, power is released to the direct current bus in a constant voltage mode, the grid-connected unit is enabled to release the maximum grid-connected power from the direct current bus to the power grid, and the new energy power generation unit adopts a constant power mode; if SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the energy storage unit to work in a hydrogen production mode to charge at constant current and constant voltage;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit when the SOC is 1.02U bus<Unow≤1.05Ubus, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to the power grid, wherein the new energy power generation unit adopts an MPPT working mode; the SOC is less than 0.1, the new energy unit is used for regulating the voltage of the direct current bus, and the energy storage unit works in a hydrogen production mode and is charged with constant current and constant voltage;
when the voltage of the direct current bus is 0.98U bus<Unow≤1.02Ubus, the voltage of the direct current bus is basically kept unchanged, the grid-connected unit regulates the voltage of the direct current bus, and the photovoltaic unit is switched to an MPPT control mode;
When the SOC is more than or equal to 0.1, when the SOC is more than or equal to 0.95U bus<Unow≤0.98Ubus, the energy storage unit is used for regulating the voltage of the direct current bus, power is released to the direct current bus in a constant voltage mode, the grid-connected unit is enabled to absorb grid-connected power from the direct current bus to the power grid, and the new energy power generation unit adopts an MPPT working mode; if SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the energy storage unit to work in a hydrogen production mode to charge at constant current and constant voltage;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit when the SOC is more than or equal to 0.90U bus<Unow≤0.95Ubus, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to the power grid, wherein the new energy power generation unit adopts an MPPT working mode; and if the SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to the power grid.
In a specific embodiment, as shown in fig. 2, the NPC three-level rectifier topology is connected to diodes connected in series with upper and lower bridge arms respectively through a pair of neutral point clamping diodes, power switching devices are connected in series respectively, the clamping diodes are used for clamping the level, the voltages on the two capacitors on the dc side are equal, the power switching devices are controlled logically according to the switching sequence, and three phase voltage levels are generated to synthesize a sine wave at the output end.
The NPC three-level inverter is a bidirectional three-level inverter, and the mathematical model is completely the same as the three-phase PWM converter under the three-phase abc coordinate system, and is as follows:
rotation to a two-phase synchronous rotation coordinate system dq can be obtained:
Wherein, L is line inductance, t is time, i a、ib、ic is A, B, C phase current, R is line resistance, e a、eb、ec is grid voltage, S a、Sb、Sc is three-phase switching function, v dc is DC bus voltage, d and q represent d-axis and q-axis components in dq coordinate system. In the mathematical model under the dq coordinate system, the alternating current quantity is completely changed into direct current quantity, and the static-difference-free control of voltage and current is realized by adopting the dq decoupling and PI control modes. The grid-connected unit has the advantages of small alternating-current side harmonic wave, power factor of more than 0.95, high electric energy quality, interaction friendliness with a power grid, strong dynamic adjustment capability of power electronic equipment, four-quadrant working mode, capability of supporting rectification to produce hydrogen, and power generation and grid connection of hydrogen energy, namely bidirectional power flow.
In a specific embodiment, as shown in fig. 7, the control strategy of the grid-connected unit first samples the current values of the current grid-connected currents iA, iB, iC, the voltage values of the grid voltages eA, eB, eC, and the dc bus voltage value UDC; and carrying out Clark conversion and Park conversion on the sampled iA, iB, iC, eA, eB, eC to obtain grid-connected currents id and iq and grid points ed and eq under a dp rotation coordinate system. Further, in the algorithm, a reference value UDC_ ref of the direct current bus voltage is subtracted by UDC, and the obtained result passes through a PI controller of a voltage ring to obtain a reference value id_ref of grid-connected current id; and sending the results obtained by subtracting id and iq from id_ref and iq_ref into a PI controller of a current loop, decoupling signals output by the controller to obtain modulated waves Ud_ref and Uq_ref under a dp rotation coordinate system, obtaining modulated wave signals after inverse Park conversion and inverse Clark conversion, obtaining on-off signals of 12 power switching tubes of the NPC converter after the modulated wave signals pass through an SPWM modulator, and performing corresponding on-off operation on the power switching tubes according to the on-off signals, thereby realizing a grid-connected control strategy of a grid-connected unit.
In one particular embodiment, a bi-directional DC/DC converter topology is shown in FIG. 3, which is a DC/DC converter with bi-directional energy flow, the front stage being a DC bus and the rear stage being a hydrogen plant or hydrogen fuel cell. The charge-discharge control strategy is shown in fig. 6, and when the charge-discharge control strategy works, the duty ratio of the switching tube S1 is D, the voltage on the capacitor C2 is U bat＝(1-D)Udc in a steady state, and the charge-discharge function of the battery can be realized through the control method of the power outer ring and the current inner ring. The hydrogen production equipment works in the voltage range of 500V-1000V, and the hydrogen production current can reach 5500A-12000A.
In a specific embodiment, the photovoltaic array and the DC/DC converter form a photovoltaic unit, and the DC/DC converter has a topological structure as shown in fig. 4, and since the output characteristic of the photovoltaic array has a nonlinear characteristic and the output is affected by sunlight intensity, ambient temperature and load conditions, in order to improve the overall efficiency of the photovoltaic system, the photovoltaic array is controlled by using an MPPT algorithm, so that the photovoltaic system always outputs the maximum power. The MPPT algorithm adopts an interference observation method, and the principle is that the output voltage of the photovoltaic array is increased or decreased at regular intervals, and the change direction of the output power is observed to determine the control signal of the next step, and the algorithm flow is shown in fig. 5, wherein U pv、Ipv is the output voltage of the photovoltaic array, P is the power P - of the battery at the current moment and is the power of the battery array at the last moment.
In a specific embodiment, the wind power unit uses a three-level converter as shown in fig. 2 to transfer the electric energy generated by the wind power generator to the dc bus.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (6)
1. A bidirectional reversible new energy hydrogen production system based on a phase-shifting transformer is characterized by comprising: the system comprises a grid-connected unit, a direct current bus, a new energy power generation unit and an energy storage unit;
The AC end of the grid-connected unit is connected with a power grid, and the DC end of the grid-connected unit is connected with the direct current bus and is used for exchanging electric energy between the direct current bus and the power grid;
The output end of the new energy power generation unit is connected with the direct current bus to provide electric energy for the direct current bus;
The energy storage unit is connected with the direct current bus, hydrogen is prepared by using electric energy of the direct current bus and stored in the hydrogen production mode of the energy storage unit, and the stored hydrogen is used for generating electricity to provide electric energy for the direct current bus in the electricity generation mode of the energy storage unit;
Defining a working interval based on the rated voltage of the direct current bus, and selecting a control method of a grid-connected unit, a new energy power generation unit and an energy storage unit in the system according to the working interval where the voltage value of the current direct current bus is located;
The voltage and power transmission control method of the direct current bus is as follows:
Setting the rated voltage value of the direct current bus as U bus when the system operates normally, setting the voltage value of the direct current bus of the current system as U now, and setting the state of charge of the fuel cell as SOC;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit when the SOC is 1.05U bus<Unow≤1.1Ubus, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid, wherein the new energy power generation unit adopts a constant power mode; if SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the energy storage unit to work in a hydrogen production mode to charge at constant current and constant voltage;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit when the SOC is 1.02U bus<Unow≤1.05Ubus, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid, wherein the new energy power generation unit adopts an MPPT working mode; the SOC is less than 0.1, the new energy unit is used for regulating the voltage of the direct current bus, and the energy storage unit works in a hydrogen production mode and is charged with constant current and constant voltage;
when the voltage of the direct current bus is 0.98U bus<Unow≤1.02Ubus, the voltage of the direct current bus is basically kept unchanged, the grid-connected unit regulates the voltage of the direct current bus, and the photovoltaic unit is switched to an MPPT control mode;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit, releasing power to the direct current bus in a constant voltage mode, enabling the grid-connected unit to absorb grid-connected power from the direct current bus to a power grid, and enabling the new energy power generation unit to adopt an MPPT working mode; if SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the energy storage unit to work in a hydrogen production mode to charge at constant current and constant voltage;
When the SOC is more than or equal to 0.1, regulating the voltage of the direct current bus by using the energy storage unit, releasing power to the direct current bus in a constant voltage mode, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid, wherein the new energy power generation unit adopts an MPPT working mode; and if the SOC is less than 0.1, regulating the voltage of the direct current bus by using the new energy unit, and enabling the grid-connected unit to release the maximum grid-connected power from the direct current bus to a power grid.
2. The bi-directional reversible new energy hydrogen production system based on the phase-shifting transformer as claimed in claim 1, wherein the grid-connected unit comprises the phase-shifting transformer and an NPC three-level rectifier;
the phase-shifting transformer main winding is connected with a power grid, the auxiliary winding is connected with the AC end of the NPC three-level rectifier, and the phase difference between the main winding and the auxiliary winding is controlled by adjusting the connection mode of the auxiliary winding or the coupling magnetic flux of the phase-shifting converter, so that the power flow direction and the voltage are controlled;
The NPC three-level rectifier DC end is connected with the direct current bus, and the NPC three-level rectifier logically controls a power switch device according to a switch sequence to generate three phase voltage levels, and synthesizes alternating current at an AC end.
3. The bidirectional reversible new energy hydrogen production system based on the phase-shifting transformer as recited in claim 1 wherein the new energy power generation unit comprises a photovoltaic unit and a wind power unit, the photovoltaic unit is connected with the direct current bus by adopting a DC/DC converter, and the wind power unit is connected with the direct current bus by adopting an NPC three-level converter.
4. A bi-directional reversible new energy hydrogen production system based on a phase-shifting transformer as in claim 3 wherein said DC/DC converter is a Boost converter; the photovoltaic unit adopts an MPPT control method to control electric energy output, and comprises the following steps:
Step 1: obtaining output voltage U PV 0 and output current i PV 0 at the initial moment of the photovoltaic array, and inputting the output voltage U PV 0 and the output current i PV 0 into an MPPT algorithm module;
Step 2: the MPPT algorithm module calculates initial output power P 0 of the photovoltaic array, randomly generates disturbance voltage delta U 0, and outputs a reference value U ref of voltage to a PI regulator according to U PV 0 and delta U 0, wherein the absolute value of delta U 0 is smaller than 0.5% of U PV;
Step 3: the PI regulator outputs a switching signal of a power switching tube of the Boost converter after passing through a PWM modulator according to the U ref, so as to regulate the electric energy output of the photovoltaic array;
Step 4: obtaining output voltage U PV and output current i PV of the photovoltaic array at the current moment, and inputting the output voltage U PV and the output current i PV into an MPPT algorithm module;
Step 5: the MPPT algorithm module calculates the output power P of the photovoltaic array at the current moment and the change DeltaP of the power P - of the photovoltaic array at the previous moment, determines to apply a tiny disturbance voltage DeltaU to the U PV according to the disturbance voltage DeltaU - applied at the previous moment, and outputs a reference value U ref of the voltage to the PI regulator according to U PV and DeltaU;
step 6: and repeatedly executing the steps 3-5.
5. The bidirectional reversible new energy hydrogen production system based on the phase-shifting transformer as recited in claim 4, wherein in step5,
When the delta P >0, deltaU - >0 is DeltaU >0, deltaU - <0 is DeltaU <0;
When Δp <0, Δu - >0 is Δu <0, and Δu - <0 is Δu >0.
6. The bi-directional reversible new energy hydrogen production system based on a phase-shifting transformer of claim 1, wherein the energy storage unit comprises: a bidirectional DC/DC converter, an electrolytic tank, a compressor, a storage tank and a fuel cell;
The front stage of the bidirectional DC/DC converter is the direct current bus, and the rear stage is the electrolytic tank or the hydrogen fuel cell; in the hydrogen production mode, the electrolyzer electrolyzes and generates hydrogen by utilizing the electric energy provided by the bidirectional DC/DC converter, and stores the hydrogen into the storage tank through the compressor; in the power generation mode, the hydrogen fuel cell generates power using hydrogen in the storage tank and supplies power to the bidirectional DC/DC converter.
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