A megawatt fuel cell grid-connected power generation system and a control method thereof

Abstract

The application provides a megawatt fuel cell grid-connected power generation system and a control method thereof. The system comprises a megawatt fuel cell stack group, a plurality of power generation modules, each power generation module works in parallel, and each power generation module comprises a plurality of stacks connected in series; a megawatt inverter group, a plurality of inverter groups, the inverter group is arranged one by one with the power generation module, and each inverter group comprises a plurality of parallel inverters, the number of inverters is the same as the number of stacks contained in the power generation module corresponding to the inverter group; a grid-connected cabinet, the output end of the grid-connected cabinet is connected with the output end of each inverter group, and the output end of the grid-connected cabinet is connected with the low-voltage side of a step-up transformer; a step-up transformer and a control system. The application supports power grid scheduling, does not need an energy buffer device, has the characteristics of simple structure, flexible operation, stable and reliable operation, high efficiency, scalability and the like.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to a megawatt-level fuel cell grid-connected power generation system and its control method. Background Technology

[0002] A fuel cell is a chemical device that directly converts the chemical energy of fuel into electrical energy. Because fuel cells convert the Gibbs free energy portion of the fuel's chemical energy into electrical energy through an electrochemical reaction, they are not limited by the Carnot cycle effect, resulting in high conversion efficiency. Furthermore, fuel cells use fuel and oxygen as feedstock and have no mechanical transmission components, thus emitting very few harmful gases and having a long service life. Therefore, from the perspective of energy conservation and environmental protection, fuel cells are the most promising power generation technology.

[0003] Under the dual-carbon context, the large-scale application of new energy sources such as fuel cells has become a trend. Currently, megawatt-level or higher fuel cell power generation systems are rare, and existing grid-connected fuel cell power generation systems typically include lithium battery packs, DC / DC converters, and DC / AC inverters. However, most existing grid-connected inverter products are for photovoltaic, wind power, and lithium batteries, with no dedicated inverter products for fuel cells. This necessitates specific conversion circuitry from companies like Yongtuo to be used in fuel cell systems. Furthermore, some DC / AC inverter products include isolation transformers, making the structure of grid-connected fuel cell power generation systems, especially megawatt-level systems, complex, and reducing output efficiency after multiple energy conversions. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a megawatt-level fuel cell grid-connected power generation system and its control method. Multiple fuel cell power generation modules generate DC power, which is then converted into AC power by multiple inverter sets and connected to the grid via a step-up transformer. The response power is set by a local controller, avoiding the use of energy buffering devices.

[0005] The technical means employed in this invention are as follows:

[0006] A megawatt-class fuel cell grid-connected power generation system includes:

[0007] A megawatt-level fuel cell stack, wherein the megawatt-level fuel cell stack includes several power generation modules, each of which operates in parallel, and any power generation module includes multiple stacks connected in series;

[0008] A megawatt-level inverter group, comprising several inverter groups, each inverter group being configured in a one-to-one correspondence with a power generation module, and each inverter group comprising multiple inverters connected in parallel, the number of inverters being the same as the number of fuel cells contained in the power generation module corresponding to the inverter group, and each inverter being electrically connected to each fuel cell contained in the power generation module corresponding to the inverter group.

[0009] A grid-connected cabinet, the output terminal of which is connected to the output terminal of each inverter group, and the output terminal of which is connected to the low-voltage side of the step-up transformer;

[0010] A step-up transformer, which steps up the AC power output from the grid-connected cabinet to 10kV for grid connection;

[0011] and a control system, the control system including a local controller, a host computer, and a remote operator station.

[0012] The local controller includes a fuel cell module controller, an auxiliary system controller, and an energy management controller. The fuel cell module controller controls the start and stop of each power generation module, the auxiliary system controller controls the setting of auxiliary machine parameters in the power generation auxiliary system, and the energy management controller controls the start and stop of each inverter group.

[0013] The host computer is used for local monitoring.

[0014] The remote operating station is used to receive grid dispatch instructions, convert the dispatch instructions into a communication protocol that the local controller can recognize, and then the local controller controls the power generation.

[0015] Furthermore, the fuel cell module controller controls the start and stop of each power generation module, including: adjusting the number of stacks connected in series to ensure that the operating voltage range of the power generation module does not exceed the DC input voltage range of the inverter.

[0016] Furthermore, the inverter is an energy storage grid-connected inverter, the DC side voltage range of a single inverter is greater than the voltage operating range of the fuel cell power generation module, and the total capacity of the inverter group must be greater than the capacity of the fuel cell stack group.

[0017] Furthermore, the step-up transformer is a split transformer, and the capacity of the step-up transformer is not less than the capacity of the inverter group.

[0018] This invention also discloses a megawatt-level fuel cell grid-connected power generation control method, comprising the following steps:

[0019] The number of power generation modules to operate is set according to power generation demand;

[0020] The remote operating station sends a start command for the fuel cell grid-connected power generation system to the power generation system controller. The power generation system executes the start-up process, which includes: starting the auxiliary equipment of the power generation system through the auxiliary system controller, and then starting the power generation module through the fuel cell controller.

[0021] After the power generation system is started, the power generation system controller receives the power generation setting manually or remotely, and sends instructions to the auxiliary system controller, fuel cell controller and energy management controller respectively. The inverter group receives the power instructions sent by the energy management controller and performs closed-loop control on the power value.

[0022] After the power generation system operation is completed, the power generation system is first deloaded. Then, the remote operation station sends a shutdown command to the power generation system controller. The power generation system executes the shutdown process, which includes: first executing the shutdown operation of the power generation module, and then executing the shutdown operation of the auxiliary equipment of the power generation system.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The fuel cell grid-connected power generation system provided by this invention has a simple structure, adopts an energy storage grid-connected inverter, avoids the internal losses of the equipment body caused by the isolation transformer, adopts a multi-machine parallel working mode, not only has remote control function, supports grid dispatch, and has stable operation and high efficiency.

[0025] 2. This invention sets the corresponding power through a local controller, achieving efficient control of the grid-connected power generation system without the need for an energy buffer device, thus meeting the power demand of the power grid.

[0026] 3. The power generation module used in this invention is a multi-stack series structure, which is used in conjunction with the inverters in the inverter group. It can not only operate independently but also serve as a backup for each other, thus enhancing the scalability of the system.

[0027] Based on the above reasons, this invention can be widely promoted in the field of fuel cells. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of a megawatt-level fuel cell grid-connected power generation system according to the present invention.

[0030] Figure 2This is an electrical connection block diagram of a megawatt-level fuel cell grid-connected power generation system in an embodiment.

[0031] Figure 3 This is an operation flowchart of a megawatt-level fuel cell grid-connected power generation system in one embodiment. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] like Figure 1As shown, this invention provides a megawatt-level fuel cell grid-connected power generation system, comprising a megawatt-level fuel cell stack, a megawatt-level inverter group, a grid-connected cabinet, a step-up transformer, and a control system. The megawatt-level fuel cell stack consists of multiple fuel cell power generation modules, each containing multiple fuel cell stacks, which convert the chemical energy of hydrogen into electrical energy through an electrochemical reaction. The megawatt-level inverter group consists of multiple inverter groups, the number of which is the same as the number of fuel cell power generation modules. Each inverter group contains multiple inverters operating in parallel, converting the DC output power from the fuel cells into AC output power. The grid-connected cabinet connects the multiple inverter groups to the low-voltage side branch of the step-up transformer. The step-up transformer boosts the AC output voltage of the inverters to 10kV for grid connection. The control system includes a local PLC controller, a local supervisory control unit (SCADA) computer, and a remote operator station. The local controller comprises a fuel cell module controller, an auxiliary system controller, and an energy management controller. The fuel cell module controller controls multiple fuel cell power generation modules, the auxiliary system controller controls the auxiliary equipment in the power generation auxiliary system, and the energy management controller controls the inverter group. The local controller adjusts the actions of the auxiliary equipment in the power generation system and parameters such as the gas supply to the power generation modules in real time based on the power setpoint, responding to power values ​​in real time without the need for an energy buffer device. The local SCADA computer enables local monitoring of the fuel cell grid-connected power generation system. The remote operator station receives grid dispatch commands and converts them into a communication protocol recognizable by the local controller, which then controls the power generation output. In this invention, the auxiliary system refers to conventional fuel cell-related devices such as external gas and water supply required for the operation of the fuel cell power generation modules.

[0035] Each fuel cell power generation module establishes its DC output bus voltage through internal stack series-parallel connections. The DC output bus of each fuel cell power generation module is directly electrically connected to the DC input terminal of a single inverter group. The AC output terminal of each inverter group is electrically connected to the outgoing terminals within the grid-connected cabinet. The outgoing terminals within the grid-connected cabinet can be simultaneously electrically connected to the AC output terminals of multiple inverter groups. The incoming terminals within the grid-connected cabinet are electrically connected to the low-voltage side of the step-up transformer. The high-voltage side of the step-up transformer is electrically connected to the 10kV bus via a switchgear. The inverter group control terminal and the grid-connected cabinet control terminal are connected to the local controller signal.

[0036] In a preferred embodiment of the present invention, the fuel cell power generation module may include multiple fuel cell stacks. By adjusting the number of stacks connected in series, the operating voltage range of the fuel cell power generation module shall not exceed the DC input voltage range of the inverter.

[0037] In a preferred embodiment of the present invention, each inverter in the inverter group is an energy storage grid-connected inverter, which does not contain an isolation transformer to reduce internal losses of the equipment body, can be connected in parallel by multiple units, has remote control function, the DC side voltage range of a single inverter is greater than the voltage operating range of the fuel cell power generation module, and the total capacity of the inverter group needs to be greater than the capacity of the fuel cell stack group.

[0038] In a preferred embodiment of the present invention, the grid-connected cabinet includes a circuit breaker, a comprehensive protection device, and a multi-function meter, and has a remote control on / off function.

[0039] In a preferred embodiment of the present invention, the step-up transformer is a double-split transformer, and its capacity is not less than the capacity of the inverter group.

[0040] In a preferred embodiment of the present invention, the control system has active and reactive power regulation functions.

[0041] This invention also discloses a megawatt-level fuel cell grid-connected power generation control method, comprising the following steps:

[0042] S1. Set the number of power generation modules to operate according to power generation needs.

[0043] S2. The remote operating station sends a start command for the fuel cell grid-connected power generation system to the power generation system controller. The power generation system executes the start-up process, which includes: executing the start-up operation of the auxiliary machine of the power generation system through the auxiliary system controller, and then performing the start-up operation of the power generation module through the fuel cell controller.

[0044] S3. After the power generation system is started, the power generation system controller receives the power generation setting manually or remotely, and sends instructions to the auxiliary system controller, fuel cell controller and energy management controller respectively. The inverter group receives the power instruction sent by the energy management controller and performs closed-loop control on the power value.

[0045] S4. After the power generation system operation is completed, the power generation system is first deloaded. Then, the remote operation station sends a shutdown command to the power generation system controller. The power generation system executes the shutdown process, which includes: first executing the shutdown operation of the power generation module, and then executing the shutdown operation of the auxiliary equipment of the power generation system.

[0046] The technical solution of the present invention will be further explained below through specific application examples.

[0047] Example 1

[0048] like Figure 2The diagram shown is an electrical connection block diagram of a megawatt-level fuel cell grid-connected power generation system provided by the present invention. The power generation system consists of six sets of fuel cell power generation modules, six sets of inverter groups, two grid-connected cabinets, and one step-up transformer. The first set of fuel cell power generation modules consists of four fuel cells (stack 1-1, stack 1-2, stack 1-3, and stack 1-4) connected in series. The first set of inverter groups consists of four inverters (inverter 1-1, inverter 1-2, inverter 1-3, and inverter 1-4) connected in parallel. The rest are connected similarly. The grid-connected cabinet contains switches and protection devices. The step-up transformer is a double-split transformer. The positive output terminal of each fuel cell power generation module is electrically connected to the positive busbar, and the negative output terminal is electrically connected to the negative busbar. In each inverter group, the positive and negative DC input terminals of each inverter are electrically connected to the aforementioned positive and negative busbars via cables. The AC output terminal of each inverter in the first three inverter groups is electrically connected to one side of the busbar leading out of the grid-connected cabinet 1 switch via a cable. The other side of the grid-connected cabinet 1 switch is electrically connected to one branch of the low-voltage side of the step-up transformer via a cable. The AC output terminal of each inverter in the last three inverter groups is electrically connected to one side of the busbar leading out of the grid-connected cabinet 2 switch via a cable. The other side of the grid-connected cabinet 2 switch is electrically connected to another branch of the low-voltage side of the step-up transformer via a cable. The operating voltage range of the fuel cell power generation module is approximately 700–1300VDC, and the DC input range of the inverter is 600–1500VDC, which is greater than the operating voltage of the fuel cell power generation module. The capacity of a single inverter group is greater than the output power of a single fuel cell power generation module. The inverter's AC output is 400VAC, the grid-connected cabinet switch's capacity is greater than the parallel power of three inverter groups, and the capacity of each step-up transformer is greater than the sum of the capacities of three fuel cell power generation modules.

[0049] Example 2

[0050] This invention provides a control method for a megawatt-level fuel cell grid-connected power generation system, used to control the grid-connected power generation system described in Example 1. The grid-connected power generation system includes a local controller, a local supervisory control unit (SCADA) computer, and a remote operator station. The local controller includes a fuel cell module controller, an auxiliary system controller, an energy management controller, and a power generation system controller. The fuel cell module controller estimates the current maximum power output P1 to P6 in real time based on the current module operating status and gas supply, and uploads this estimate to the power generation system controller. The auxiliary system controller performs closed-loop control of the gas setpoint according to instructions issued by the power generation system controller. The energy management controller issues power commands to each inverter group based on the power value issued by the power generation system controller, referring to an algorithm; each inverter group performs closed-loop control of the power setpoint. The power generation system controller issues commands to the fuel cell module controller, the auxiliary system controller, and the energy management controller respectively based on the current system status, power demand, and current maximum power output. The power generation system controller has a preset power setpoint and gas supply curve, where the gas excess coefficient varies at different power levels, with a larger coefficient at low power and a smaller coefficient at high power.

[0051] Example 3

[0052] like Figure 3 The diagram shows the operation flowchart of a megawatt-level fuel cell grid-connected power generation system provided by this invention. Before starting the grid-connected power generation system, parameter settings are required, including selecting the number of fuel cell power generation modules to operate. Then, a power generation system start-up command is sent to the power generation system controller. The power generation system controller sends commands to the auxiliary system controller and the power generation system controller, which execute the start-up actions respectively. After the power generation system starts, power generation adjustment operations can be performed. The preset power generation value can be set locally by the operator or remotely through the dispatch center and sent to the power generation system controller. The power generation system controller sends commands to the energy management controller, auxiliary system controller, and fuel cell controller according to the algorithm. The energy management controller sends commands to the inverter group according to the algorithm. The inverter group performs closed-loop control of the set value. The auxiliary system controller adjusts the external gas supply for the specified power. The fuel cell controller controls the operating status of the fuel cell power generation modules. These three components cooperate to complete the power generation system loading process and maintain stable system operation.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A megawatt-level fuel cell grid-connected power generation system, characterized in that, include: A megawatt-level fuel cell stack, wherein the megawatt-level fuel cell stack includes several power generation modules, each of which operates in parallel, and any power generation module includes multiple stacks connected in series; A megawatt-level inverter group, comprising several inverter groups, each inverter group being configured in a one-to-one correspondence with a power generation module, and each inverter group comprising multiple inverters connected in parallel, the number of inverters being the same as the number of fuel cells contained in the power generation module corresponding to the inverter group, and each inverter being electrically connected to each fuel cell contained in the power generation module corresponding to the inverter group. A grid-connected cabinet, the output terminal of which is connected to the output terminal of each inverter group, and the output terminal of which is connected to the low-voltage side of the step-up transformer; A step-up transformer, which steps up the AC power output from the grid-connected cabinet to 10kV for grid connection; and a control system, the control system including a local controller, a host computer, and a remote operator station. The local controller includes a fuel cell module controller, an auxiliary system controller, and an energy management controller. The fuel cell module controller controls the start and stop of each power generation module, the auxiliary system controller controls the setting of auxiliary machine parameters in the power generation auxiliary system, and the energy management controller controls the start and stop of each inverter group. The host computer is used for local monitoring. The remote operating station is used to receive grid dispatch instructions and convert the dispatch instructions into a communication protocol recognizable by the local controller, which then controls the power generation. The fuel cell module controller controls the start and stop of each power generation module, including adjusting the number of stacks connected in series to ensure that the operating voltage range of the power generation module does not exceed the DC input voltage range of the inverter. The inverter is an energy storage grid-connected inverter, and the DC voltage range of a single inverter is greater than the operating voltage range of the fuel cell power generation module, and the total capacity of the inverter group must be greater than the capacity of the fuel cell stack group.

2. The megawatt-level fuel cell grid-connected power generation system according to claim 1, characterized in that, The step-up transformer is a dual-split transformer, and the capacity of the step-up transformer is not less than the capacity of the inverter group.

3. A megawatt-level fuel cell grid-connected power generation control method, characterized in that, The application of a megawatt-level fuel cell grid-connected power generation control system as described in claim 1 or 2 includes the following steps: The number of power generation modules to operate is set according to power generation demand; The remote operating station sends a start command for the fuel cell grid-connected power generation system to the power generation system controller. The power generation system executes the start-up process, which includes: starting the auxiliary equipment of the power generation system through the auxiliary system controller, and then starting the power generation module through the fuel cell controller. After the power generation system is started, the power generation system controller receives the power generation setting manually or remotely, and sends instructions to the auxiliary system controller, fuel cell controller and energy management controller respectively. The inverter group receives the power instructions sent by the energy management controller and performs closed-loop control on the power value. After the power generation system operation is completed, the power generation system is first deloaded. Then, the remote operation station sends a shutdown command to the power generation system controller. The power generation system executes the shutdown process, which includes: first executing the shutdown operation of the power generation module, and then executing the shutdown operation of the auxiliary equipment of the power generation system.

Images