Method of generating electrical energy and electrical energy conversion system

Abstract

The application provides a power generation method, comprising the steps of: setting AC / DC converters for each asynchronous generator set and connecting the asynchronous generator set to a DC bus; starting the asynchronous generator set, actively increasing the rotating speed to a grid-connected rotating speed set point, or passively waiting for the rotating speed to exceed the grid-connected rotating speed set point to start the power generation system; presetting voltage set values of each AC / DC converter; starting each AC / DC converter to provide power for DC power consumption equipment through the DC bus; and controlling each AC / DC converter by using a droop control principle to stabilize the DC bus voltage and balance the loads of each asynchronous generator set. The power generation method provided by the application can generate power by using asynchronous generator sets under the condition of unstable generator frequency and voltage. The application also relates to a power conversion system using the power generation method.

Description

Technical Field

[0001] This invention relates to a method for generating electrical energy, and more particularly to a method for generating electrical energy using an asynchronous generator set. The invention also relates to an energy conversion system utilizing the above-described method for generating electrical energy. Background Technology

[0002] When the mechanical load is low, the shaft-driven working equipment can convert excess prime mover mechanical energy into electrical energy in order to maintain the best prime mover efficiency. However, when using an asynchronous generator set to generate energy, the shaft-driven working equipment operates within a wide speed range, which prevents the asynchronous generator set from providing a stable frequency AC power supply. Therefore, it cannot be connected to the AC power grid. Summary of the Invention

[0003] The purpose of this invention is to provide a method for generating electrical energy, which enables the generation and use of energy through an asynchronous generator set.

[0004] Another object of the present invention is to provide an energy conversion system capable of generating and using energy through an asynchronous generator set.

[0005] This invention provides a method for generating electrical energy, comprising the following steps:

[0006] Each asynchronous generator set is equipped with an AC / DC converter and connected to the DC bus;

[0007] Start the asynchronous generator set to actively increase the speed to the grid-connected speed set point, or passively wait for the speed to exceed the grid-connected speed set point before starting the power generation system;

[0008] Preset the voltage settings for each AC / DC converter;

[0009] Start all AC / DC converters to provide power to DC equipment via the DC bus; and

[0010] The droop control principle is used to control each AC / DC converter, stabilize the DC bus voltage, and balance the load of each asynchronous generator set.

[0011] The power generation method provided by this invention converts AC power generated by several asynchronous generator sets into DC power with controllable voltage using an AC / DC converter. This DC power is then fed into a DC bus to provide electrical load for DC-powered equipment. Furthermore, the method utilizes droop control principles to control each AC / DC converter, stabilizing the DC bus voltage and balancing the load of each asynchronous generator set. Therefore, the power generation method provided by this invention enables energy generation and utilization through asynchronous generator sets. Of course, this power generation method is also suitable for power generation applications where precise control of the prime mover speed is not required or where optimal energy consumption needs to be controlled according to load changes.

[0012] In another illustrative embodiment of the power generation method, the step of presetting the voltage setting value of each AC / DC converter specifically includes the following steps:

[0013] Set the DC bus reference voltage and maximum deviation value;

[0014] Obtain the real-time DC bus voltage and calculate whether the difference between the DC bus reference voltage and the real-time DC bus voltage is greater than the maximum deviation value.

[0015] If so, set the voltage setting of the AC / DC converter to the DC bus reference voltage; and

[0016] Otherwise, set the voltage setting of the AC / DC converter to the real-time DC bus voltage.

[0017] In another illustrative embodiment of the power generation method, the steps of controlling each AC / DC converter using the droop control principle to stabilize the DC bus voltage and balance the load of each asynchronous generator set specifically include the following steps:

[0018] Pre-set the load percentage-droop voltage compensation value curve for each asynchronous generator set;

[0019] Switch the voltage setting value of each AC / DC converter to the sum of the DC bus reference voltage and the droop voltage compensation value of each asynchronous generator set;

[0020] Based on the real-time load percentage and load percentage-droop voltage compensation curves of each asynchronous generator set, calculate the droop voltage compensation value and voltage setpoint of each AC / DC converter; and

[0021] The AC / DC converter automatically adjusts the speed of the asynchronous generator set according to the load requirements and optimal efficiency curve of the asynchronous generator set.

[0022] In another illustrative embodiment of the power generation method, the load percentage-droop voltage compensation curve is set such that the droop voltage compensation value reaches its maximum value when the load percentage is 0%, and the droop voltage compensation value is 0 when the load percentage is 100%.

[0023] In another illustrative embodiment of the power generation method, the power generation method further includes the step of: installing a DC / AC converter on a DC bus, and providing power to AC electrical equipment through the DC / AC converter.

[0024] This invention also provides a power conversion system, including several asynchronous generator sets, several AC / DC converters, a DC bus, and several controllers. Each asynchronous generator set can be driven by shaft-driven power equipment. The AC / DC converters control the asynchronous generator sets one-to-one and convert the AC power generated by the asynchronous generator sets into DC power with adjustable voltage. The DC bus can connect several AC / DC converters and provide power loads to DC-consuming equipment. The controllers control the AC / DC converters one-to-one and are configured to preset the voltage setpoints of the AC / DC converters when the asynchronous generator sets start up, and to control each AC / DC converter using a droop control principle to stabilize the DC bus voltage and balance the load of each asynchronous generator set.

[0025] The power conversion system provided by this invention converts AC power generated by several asynchronous generator sets into DC power with controllable voltage using AC / DC converters. This DC power is then fed into a DC bus to provide the power required by DC electrical equipment. Furthermore, a controller, based on the droop control principle, controls each AC / DC converter to stabilize the DC bus voltage and balance the load of each asynchronous generator set. This power conversion system enables energy generation and utilization through asynchronous generator sets. Of course, this power conversion system is also suitable for power generation applications where precise control of the prime mover speed is not required or where optimal energy consumption needs to be controlled according to load changes.

[0026] In another illustrative embodiment of the power conversion system, each controller is configured to obtain the real-time DC bus voltage from the corresponding AC / DC converter, and calculate whether the difference between the DC bus reference voltage and the real-time DC bus voltage is greater than the maximum deviation value based on the preset DC bus reference voltage and the maximum deviation value. If so, the corresponding AC / DC converter is controlled to use the DC bus reference voltage as the voltage setpoint; otherwise, the corresponding AC / DC converter is controlled to use the real-time DC bus voltage as the voltage setpoint.

[0027] In another illustrative embodiment of the power conversion system, each controller is configured to have a preset load percentage-droop voltage compensation value curve for the corresponding asynchronous generator set. The controller is configured to obtain the real-time load percentage of the asynchronous generator set from the corresponding AC / DC converter, calculate the droop voltage compensation value in combination with the load percentage-droop voltage compensation value curve, and control the corresponding AC / DC converter to use the sum of the DC bus reference voltage and the droop voltage compensation value as the voltage setpoint.

[0028] In another illustrative embodiment of the power conversion system, in the load percentage-droop voltage compensation value curve preset by each controller, the droop voltage compensation value reaches its maximum value when the load percentage is 0%, and the droop voltage compensation value is 0 when the load percentage is 100%.

[0029] In another illustrative embodiment of the power conversion system, the power conversion system further includes at least one DC / AC converter connected to the DC bus and capable of converting DC power on the DC bus into AC power with controllable parameters. Attached Figure Description

[0030] The following figures are for illustrative purposes only and do not limit the scope of the invention.

[0031] Figure 1 This is a schematic flowchart illustrating one embodiment of a method for generating electricity.

[0032] Figure 2 This is a schematic diagram illustrating one embodiment of a method for generating electricity.

[0033] Figure 3 This is a flowchart illustrating some steps of a method for generating electricity.

[0034] Figure 4 This is a flowchart illustrating some steps of a method for generating electricity.

[0035] Figure 5 This is a schematic diagram showing the relationship between the droop voltage compensation value and the load percentage.

[0036] Figure 6 This is a schematic flowchart illustrating another embodiment of the method for generating electricity.

[0037] Label Explanation

[0038] 10 Asynchronous generator sets

[0039] 20 AC / DC converters

[0040] 30 DC bus

[0041] 40 Controller

[0042] 50 DC / AC converter

[0043] 60 DC electrical equipment

[0044] 70. AC electrical equipment

[0045] U DMax Maximum value of droop voltage compensation Detailed Implementation

[0046] To provide a clearer understanding of the technical features, objectives, and effects of the invention, specific embodiments of the invention are now described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate components with the same or similar structures but the same function.

[0047] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0048] Figure 1 This is a schematic flowchart illustrating one embodiment of a method for generating electricity. Figure 2 This is a schematic diagram illustrating one embodiment of a method for generating electricity. (Refer to...) Figure 1 and Figure 2 The method for generating electricity involves several asynchronous generator sets 10 driven by shaft-driven power equipment. Specifically, the method includes the following steps:

[0049] Step S10: Install an AC / DC converter 20 for each asynchronous generator set 10 and connect it to the DC bus 30. The AC / DC converter 20 can convert the unstable AC power generated by the asynchronous generator set 10 into DC power with controllable voltage. Compared with AC grid connection, which requires consideration of parameters such as frequency, voltage, and phase sequence, connecting DC power to the DC bus 30 only requires consideration of voltage.

[0050] Step S20: Start the asynchronous generator set 10, actively increasing its speed to the grid-connected speed setpoint, or passively waiting for the speed to exceed the grid-connected speed setpoint before starting the power generation system. Startup is completed when the asynchronous generator set 10 reaches the grid-connected speed.

[0051] Step S30: Preset the voltage setting value of each AC / DC converter 20. Figure 3 This is a flowchart illustrating some steps in a method for generating electricity. (Refer to...) Figure 3 In the illustrative embodiment, step S30 specifically includes the following steps:

[0052] Step S31: Set the DC bus reference voltage and maximum deviation value. The DC bus reference voltage is determined according to the usage requirements of the DC bus 30, and after the DC bus 30 is connected to the DC electrical equipment 60, the actual voltage value of the DC bus 30 always remains near the DC bus reference voltage. The setting of the maximum deviation value is used to determine whether other AC / DC converters 20 that are already in operation have been connected to the DC bus 30 before the AC / DC converter 20 is connected to the DC bus 30.

[0053] Step S32: Obtain the real-time DC bus voltage and calculate whether the difference between the DC bus reference voltage and the DC bus real-time voltage is greater than the maximum deviation value.

[0054] Step S33: If yes, set the voltage setting of AC / DC converter 20 to the DC bus reference voltage. If the difference between the DC bus reference voltage and the real-time DC bus voltage is greater than the maximum deviation value, it means that no other AC / DC converter 20 is connected to the DC bus 30. As the first AC / DC converter 20 connected to the DC bus 30, its voltage setting determines the voltage value of the DC bus 30, and therefore can be set to the DC bus reference voltage.

[0055] Step S34: Otherwise, set the voltage setting value of AC / DC converter 20 to the real-time DC bus voltage. If the difference between the DC bus reference voltage and the DC bus real-time voltage is less than or equal to the maximum deviation value, it indicates that another AC / DC converter 20 that is currently in operation has been connected to DC bus 30. In order to avoid voltage difference, the voltage setting value of the AC / DC converter 20 that is later connected to DC bus 30 is set to the real-time DC bus voltage.

[0056] Step S40: Start each AC / DC converter 20 to provide power to the DC power supply equipment 60 through the DC bus 30. After starting, the AC / DC converter 20 automatically synchronizes with the asynchronous generator set 10, converts AC power into DC power, and boosts the voltage to the voltage set value of the AC / DC converter 20. This operation is an internal electrical control process of the AC / DC converter 20 and usually takes a very short time.

[0057] Step S50: Use the droop control principle to control each AC / DC converter 20, stabilize the DC bus 30 voltage, and balance the load of each asynchronous generator set 10. Figure 4 This is a flowchart illustrating some steps in a method for generating electricity. (Refer to...) Figure 4 In the illustrative embodiment, step S50 specifically includes the following steps:

[0058] Step S51: Preset the load percentage-droop voltage compensation value curve for each asynchronous generator set 10. Figure 5 This is a schematic diagram illustrating the relationship between droop voltage compensation and load percentage. (Refer to...) Figure 5 When the load percentage is 0%, the droop voltage compensation value reaches its maximum value U. DMax When the load percentage is 100%, the droop voltage compensation value is 0. The load percentage-droop voltage compensation value curve is generated based on the droop coefficient of each asynchronous generator set 10. The droop coefficient of the asynchronous generator set 10 corresponds to the actual parameters of the asynchronous generator set 10. Control is performed using the load percentage-droop voltage compensation value curve. There is no need for communication and coordination between the AC / DC converters 20, which enables adaptive adjustment between the AC / DC converters 20, ensuring the voltage stability of the DC bus 30 and the load balance of each asynchronous generator set 10.

[0059] Step S52: Switch the voltage setting value of each AC / DC converter 20 to the sum of the DC bus reference voltage and the droop voltage compensation value of each asynchronous generator set 10.

[0060] Step S53: Based on the real-time load percentage of each asynchronous generator set 10 and the load percentage-droop voltage compensation curve, calculate the droop voltage compensation value and voltage setting value of each AC / DC converter 20. Specifically, obtain the real-time load percentage of each asynchronous generator set 10 through each AC / DC converter 20, substitute it into the load percentage-droop voltage compensation curve to obtain the droop voltage compensation value, and then add it to the DC bus reference voltage to obtain the voltage setting value of the AC / DC converter 20.

[0061] Step S54: Each AC / DC converter 20 controls the speed of each asynchronous generator set 10 according to the voltage set value. The obtained voltage set value is input to the AC / DC converter 20, which performs internal calculations based on the voltage set value and automatically adjusts the speed of the asynchronous generator set 10 according to the load requirements and optimal efficiency curve of the asynchronous generator set 10.

[0062] The power generation method provided by this invention converts AC power generated by several asynchronous generator sets 10 into DC power with controllable voltage using an AC / DC converter 20. This DC power is then fed into a DC bus 30 to provide power to electrical equipment. Furthermore, the method utilizes a droop control principle to control each AC / DC converter 20, stabilizing the voltage of the DC bus 30 and balancing the load of each asynchronous generator set 10. Therefore, the power generation method provided by this invention enables energy generation and utilization through asynchronous generator sets 10. This power generation method is also applicable to power generation applications where precise control of the prime mover speed is not required or where optimal energy consumption needs to be controlled according to load changes.

[0063] Figure 6 This is a schematic flowchart illustrating another embodiment of the power generation method. (Refer to...) Figure 6 , and Figure 1 The similarities or identicalities in the power generation methods described above will not be repeated here. The difference lies in the fact that the power generation method further includes step S60: installing a DC / AC converter 50 on the DC bus 30, and providing AC power to the AC-using equipment 70 through the DC / AC converter 50. By using the DC / AC converter 50 to convert the DC power on the DC bus 30 into AC power with controllable frequency and voltage, the use of AC-using equipment 70 can be accommodated.

[0064] The present invention also provides an energy conversion system, with reference to Figure 2 The power conversion system includes several asynchronous generator sets 10, several AC / DC converters 20, a DC bus 30, and several controllers 40.

[0065] Each asynchronous generator set 10 can be driven by shaft-driven power equipment. An AC / DC converter 20 controls each asynchronous generator set 10 in a one-to-one correspondence and can convert the AC power generated by the asynchronous generator set 10 into DC power with adjustable voltage. The DC bus 30 can connect several AC / DC converters 20 and provide power to DC-powered equipment 60. The controller 40 can be an independent device or a functional module of the AC / DC converters 20, controlling each AC / DC converter 20 in a one-to-one correspondence. The controller 40 is configured to preset the voltage setpoints of the AC / DC converters 20 when the asynchronous generator set 10 starts, and to control each AC / DC converter 20 using a droop control principle to stabilize the DC bus 30 voltage and balance the load of each asynchronous generator set 10.

[0066] The power conversion system provided by this invention converts AC power generated by several asynchronous generator sets 10 into DC power with controllable voltage using AC / DC converters 20. This DC power is then fed into a DC bus 30 to provide power to electrical equipment. Furthermore, a controller 40, based on the droop control principle, controls each AC / DC converter 20 to stabilize the voltage of the DC bus 30 and balance the load of each asynchronous generator set 20. The power conversion system provided by this invention enables energy generation and utilization through asynchronous generator sets. Of course, this power conversion system is also suitable for power generation applications where precise control of the prime mover speed is not required or where optimal energy consumption needs to be controlled according to load changes.

[0067] In the illustrative embodiment, each controller 40 is configured to obtain the real-time DC bus voltage from the corresponding AC / DC converter 20, and calculate whether the difference between the DC bus reference voltage and the real-time DC bus voltage is greater than the maximum deviation value based on the preset DC bus reference voltage and the maximum deviation value. If so, the corresponding AC / DC converter 20 is controlled to use the DC bus reference voltage as the voltage setting value; otherwise, the corresponding AC / DC converter 20 is controlled to use the real-time DC bus voltage as the voltage setting value.

[0068] In the illustrative embodiment, each controller 40 is configured to have a preset load percentage-droop voltage compensation value curve for the corresponding asynchronous generator set 10. In the load percentage-droop voltage compensation value curve, the droop voltage compensation value reaches its maximum value U when the load percentage is 0%. DMax When the load percentage is 100%, the droop voltage compensation value is 0. The controller 40 is configured to obtain the real-time load percentage of the asynchronous generator set 10 from the corresponding AC / DC converter 20, calculate the droop voltage compensation value in combination with the load percentage-droop voltage compensation value curve, and control the corresponding AC / DC converter 20 to use the sum of the DC bus reference voltage and the droop voltage compensation value as the voltage setpoint.

[0069] In the illustrative embodiment, refer to Figure 2 The power conversion system also includes at least one DC / AC converter 50, which is connected to the DC bus 30 and can convert the DC power on the DC bus 30 into AC power with controllable parameters. By using the DC / AC converter 50 to convert the DC power on the DC bus 30 into AC power with controllable frequency and voltage, the use of AC electrical equipment 70 can also be accommodated.

[0070] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0071] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation schemes or modifications made without departing from the spirit of the present invention, such as combinations, divisions or repetitions of features, should be included within the scope of protection of the present invention.

Claims

1. A method for generating electrical energy, comprising generating electricity using several asynchronous generator sets driven by shaft-driven power equipment, characterized in that, The method for generating electrical energy includes the following steps: Each asynchronous generator set is equipped with an AC / DC converter and connected to the DC bus; Start the asynchronous generator set to actively increase the speed to the grid-connected speed set point, or passively wait for the speed to exceed the grid-connected speed set point before starting the power generation system; Preset the voltage settings for each AC / DC converter; Start all AC / DC converters to provide power to DC equipment via the DC bus; and The droop control principle is used to control each AC / DC converter, stabilize the DC bus voltage, and balance the load of each asynchronous generator set. The step of presetting the voltage settings for each AC / DC converter includes the following steps: Set the DC bus reference voltage and maximum deviation value; Obtain the real-time DC bus voltage and calculate whether the difference between the DC bus reference voltage and the real-time DC bus voltage is greater than the maximum deviation value. If so, set the voltage setting of the AC / DC converter to the DC bus reference voltage; and Otherwise, set the voltage setting of the AC / DC converter to the real-time DC bus voltage.

2. The method for generating electrical energy as described in claim 1, characterized in that, Steps: Utilizing the droop control principle to control each AC / DC converter, stabilize the DC bus voltage, and balance the load of each asynchronous generator set, specifically including the following steps: Pre-set the load percentage-droop voltage compensation value curve for each asynchronous generator set; Switch the voltage setting value of each AC / DC converter to the sum of the DC bus reference voltage and the droop voltage compensation value of each asynchronous generator set; Based on the real-time load percentage and load percentage-droop voltage compensation curves of each asynchronous generator set, calculate the droop voltage compensation value and voltage setpoint of each AC / DC converter; and The AC / DC converter automatically adjusts the speed of the asynchronous generator set according to the load requirements and optimal efficiency curve of the asynchronous generator set.

3. The method for generating electrical energy as described in claim 2, characterized in that, The load percentage-droop voltage compensation curve is set so that the droop voltage compensation value reaches its maximum value when the load percentage is 0%, and the droop voltage compensation value is 0 when the load percentage is 100%.

4. The method for generating electrical energy as described in claim 1, characterized in that, The power generation method further includes the step of: setting up a DC / AC converter on the DC bus, and providing AC power to AC electrical equipment through the DC / AC converter.

5. A power conversion system, characterized in that, include: Several asynchronous generator sets (10), which can be driven by shaft-driven power equipment; Several AC / DC converters (20) control the asynchronous generator set (10) in a one-to-one correspondence and can convert the AC power generated by the asynchronous generator set (10) into DC power with adjustable voltage. A DC bus (30) capable of connecting several of the AC / DC converters (20) and providing electrical loads for DC electrical equipment; and Several controllers (40) control the AC / DC converters (20) one by one. They are configured to preset the voltage setting value of the AC / DC converters (20) when the asynchronous generator set (10) is started, and to control each AC / DC converter (20) using the droop control principle to stabilize the DC bus (30) voltage and balance the load of each asynchronous generator set (10). Each controller (40) is configured to obtain the real-time DC bus voltage from the corresponding AC / DC converter (20), and calculate whether the difference between the DC bus reference voltage and the real-time DC bus voltage is greater than the maximum deviation value based on the preset DC bus reference voltage and the maximum deviation value. If so, the corresponding AC / DC converter (20) is controlled to use the DC bus reference voltage as the voltage setting value; otherwise, the corresponding AC / DC converter (20) is controlled to use the real-time DC bus voltage as the voltage setting value.

6. The power conversion system as described in claim 5, characterized in that, Each controller (40) is configured to have a preset load percentage-droop voltage compensation value curve for the corresponding asynchronous generator set (10). The controller (40) is configured to obtain the real-time load percentage of the asynchronous generator set (10) from the corresponding AC / DC converter (20), calculate the droop voltage compensation value in combination with the load percentage-droop voltage compensation value curve, and control the corresponding AC / DC converter (20) to use the sum of the DC bus reference voltage and the droop voltage compensation value as the voltage setpoint.

7. The power conversion system as described in claim 6, characterized in that, In the load percentage-droop voltage compensation value curve preset by each controller (40), the droop voltage compensation value reaches its maximum value when the load percentage is 0%, and the droop voltage compensation value is 0 when the load percentage is 100%.

8. The power conversion system as described in claim 5, characterized in that, The power conversion system also includes at least one DC / AC converter (50) connected to the DC bus (30) and capable of converting DC power on the DC bus (30) into AC power with controllable parameters.

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