Control Method, Device and Master Controller of a Power Electronic Converter Equipment

Abstract

The present application discloses a control method, device and main controller for a power electronic converter device. The method and device are applied to the main controller, specifically to collect the active power and total current value at the outlet side of the high-voltage direct current (HVDC) transmission system; calculate the actual slope according to the active power and the total current value; and execute a predetermined control scheme for the power electronic converter device according to the actual slope and the set slope. This solution does not require knowledge of the actual network-side parameters. Based only on the detection of the electrical quantities at the outlet side of the device, by comparing the measured data with the set criterion conditions, the control of the power electronic converter device can be achieved, ensuring the voltage stability of the HVDC transmission system.

Description

Technical Field

[0001] The present application relates to the technical field of power equipment, and more specifically, to a control method, device and main controller for a power electronic converter device. Background Art

[0002] The energy source of the power system mainly depends on fossil energy and is currently undergoing a transformation towards low-carbon renewable energy. Building a new generation of power system, which is the core of the new generation of energy system, will play a key role in achieving the energy transformation goal. Various forms of new energy, such as wind power and solar energy, are connected to the power grid through power electronic converter devices or sent to load-intensive areas through traditional high-voltage direct current (HVDC) transmission systems. China is rich in new energy resources, and the proportion of new energy access is increasing both in the western power sending system and in the eastern load-intensive receiving system. Due to the spatial distribution characteristics of energy and load, HVDC transmission also plays an increasingly important role in the west-to-east power transmission project.

[0003] The widespread application of HVDC transmission systems and the widespread access of power electronic converter devices pose higher challenges to the voltage stability of the power system. HVDC transmission systems and new energy systems are different from traditional loads, and their control characteristics may deteriorate the transient voltage stability of the power system under disturbances. The current control scheme needs to master the network-side parameters of the power system to control the power electronic converter device to ensure system voltage stability. However, the actual situation is that the specific conditions of the power system vary greatly, and it is extremely difficult to fully master the network-side parameters, so the stability of the system voltage cannot be guaranteed. Summary of the Invention

[0004] In view of this, the present application provides a control method, device and main controller for a power electronic converter device to ensure the voltage stability of an HVDC transmission system.

[0005] To achieve the above object, the following solutions are proposed:

[0006] A control method for a power electronic converter device, which is applied to a main controller for controlling the power electronic converter device of an HVDC transmission system. The control method includes the steps of:

[0007] Collecting the active power and total current value at the outlet side of the HVDC transmission system;

[0008] Calculating an actual slope according to the active power and the total current value;

[0009] Executing a predetermined control scheme for the power electronic converter device according to the actual slope and a set slope.

[0010] Optionally, performing a predetermined control scheme on the power electronic conversion device according to the actual slope and the set slope includes the steps of:

[0011] When the actual slope is greater than the set slope, controlling the power electronic conversion device to operate in a constant power control mode;

[0012] When the actual power is less than the set power, implementing control on the power electronic conversion device in a constant PLT X trajectory input mode.

[0013] Optionally, controlling the power electronic conversion device to operate in a constant power control mode includes the steps of:

[0014] When the high-voltage direct current transmission system recovers from a fault, entering the constant power control mode by using a monostable time delay method.

[0015] Optionally, the set slope is or where V O is the internal potential of the system.

[0016] Optionally, if the reactive power of the high-voltage direct current transmission system during a fault is greater than 0.5 per unit value, the set slope is

[0017] If the reactive power of the high-voltage direct current transmission system during a fault is less than 0.5 per unit value, the set slope is

[0018] A control device for a power electronic conversion device, which is applied to a main controller. The main controller is used to control the power electronic conversion device of a high-voltage direct current transmission system. The control device includes:

[0019] A parameter acquisition module configured to acquire the active power and the total current value at the outlet side of the high-voltage direct current transmission system;

[0020] A slope calculation module configured to calculate an actual slope according to the active power and the total current value;

[0021] A control execution module configured to perform a predetermined control scheme on the power electronic conversion device according to the actual slope and the set slope.

[0022] Optionally, the control execution module includes:

[0023] A first control unit configured to, when the actual slope is greater than the set slope, control the power electronic conversion device to operate in a constant power control mode;

[0024] The second control unit is configured to control the power electronic conversion device in accordance with a fixed PLT when the actual power is less than the set power. X Implement control over the power electronic conversion device in a trajectory input mode.

[0025] Optionally, the first control unit is further configured to enter the constant power control mode by using a monostable time delay method when the HVDC transmission system recovers from a fault.

[0026] Optionally, the set slope is or where V O is the internal potential of the system.

[0027] Optionally, if the reactive power of the HVDC transmission system during a fault is greater than 0.5 per unit value, the set slope is

[0028] If the reactive power of the HVDC transmission system during a fault is less than 0.5 per unit value, the set slope is

[0029] A main controller is provided with a control device for the power electronic conversion device as described above.

[0030] A main controller includes at least one processor and a memory connected to the processor, where:

[0031] The memory is used to store computer programs or instructions;

[0032] The processor is used to execute the computer programs or instructions so that the main controller implements the control method for the power electronic device as described above.

[0033] As can be seen from the above technical solutions, the present application discloses a control method, device, and main controller for a power electronic conversion device. The method and device are applied to the main controller. Specifically, the active power and total current value at the outlet side of the HVDC transmission system are collected; the actual slope is calculated based on the active power and the total current value; and a predetermined control scheme is executed for the power electronic conversion device according to the actual slope and the set slope. This solution does not require knowledge of actual network-side parameters. Based only on the detection of electrical quantities at the device outlet side and by comparing the measured data with the set criterion conditions, the control of the power electronic conversion device can be achieved, ensuring the voltage stability of the HVDC transmission system. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a flowchart of a control method for an electronic power conversion device according to an embodiment of the present application;

[0036] Figure 2 It is a schematic diagram of a system per-unit value vector model according to an embodiment of the present application;

[0037] Figure 3 It is the PLT of the present application X Schematic diagram of the trajectory form;

[0038] Figure 4 It is the PLT of the present application Q Schematic diagram of the trajectory form;

[0039] Figure 5 It is an improved switching control structure diagram for the traditional HVDC constant active power control in the present application;

[0040] Figure 6 It is the time-domain simulation diagram of the active power and voltage after the fault of the traditional HVDC transmission without control switching in the present application;

[0041] Figure 7 It is the time-domain simulation diagram of the active power and voltage after the fault of the traditional HVDC transmission with control switching in the present application;

[0042] Figure 8 The improved control structure diagram for the d-axis current control of the doubly-fed wind turbine grid-connected system in the present application;

[0043] Figure 9 It is the time-domain simulation diagram of the active power and voltage after the fault of the doubly-fed wind turbine grid-connected system without control switching in the present application;

[0044] Figure 10 It is the active power after the fault of the doubly-fed wind turbine grid-connected system with control switching in the present application;

[0045] Figure 11 It is a block diagram of a control device for an electronic power conversion device according to an embodiment of the present application;

[0046] Figure 12 It is a block diagram of a main controller according to an embodiment of the present application. Detailed implementation manners

[0047] Next, in combination with the accompanying drawings in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0048] Embodiment 1

[0049] Figure 1 It is a flowchart of a control method for an electronic power conversion device in an embodiment of the present application.

[0050] As Figure 1 shown, the control method provided in this embodiment is applied to the master control device of a high-voltage direct current transmission system and is used to control the power electronic conversion device therein. The control method includes the following steps:

[0051] S1. Collect the active power and total current value at the outlet side.

[0052] That is, obtain the active power and total current value at the outlet side from the detection devices arranged at the outlet side of the high-voltage direct current transmission system, such as current sensors, voltage sensors, etc.

[0053] S2. Calculate the actual slope according to the active power and total current value.

[0054] The calculation method is to divide the active power by the total current value, and the quotient obtained is the actual slope.

[0055] S3. Execute a predetermined control scheme according to the actual slope and the set slope.

[0056] This embodiment determines multiple parameters based on the following analysis process:

[0057] First, based on the per-unit phasor model of the single-device - connection reactance - infinite bus system, the specific relationship between the active power transmission characteristics of the high-voltage direct current transmission system and the system parameters is obtained, qualitatively explaining the relationship between the system active power transmission limit and different parameters.

[0058] The per-unit phasor model of the single-device - equivalent reactance - infinite bus system is as Figure 2 shown. Among them, P and Q are the three-phase active power and reactive power generated by the device respectively, V is the effective value of the voltage at the point of common connection, V0 is the infinite internal potential, the phase angle of which is specified as the reference 0, θ is the angle of the voltage at the device feeding point relative to the infinite internal potential, I is the effective value of the line current, and X is the value of the equivalent reactance.

[0059] The relationship between the voltage at the point of common connection and the total current output by the device is:

[0060]

[0061] The relationship between the active power transfer capacity of the system and the total output current of the equipment is:

[0062]

[0063] Then, by using the method of partial derivative, the following are obtained respectively: 1) the relationship between the active power transfer limit of the system and the equivalent reactance characterizing the grid strength; 2) the relationship between the active power transfer limit of the system and the reactive power of the equipment. Define the active power limit trajectories under different parameter changes, and through mathematical processing, extract their linear characteristics as the basis for control design.

[0064] The relationships between the above-mentioned active power transfer limit and the parameters are specifically:

[0065]

[0066] The corresponding limit current is:

[0067]

[0068] Define the active power limit trajectories under different parameter changes, and the specific linear characteristics extracted through mathematical processing are:

[0069] (1) Taking the line reactance X as the dynamic parameter, the partial derivative relationship between the active power transfer limit and the total current can be obtained:

[0070]

[0071] (2) Taking the reactive power Q as the dynamic parameter, the partial derivative relationship between the active power transfer limit and the total current can be obtained:

[0072]

[0073] Define the active power transfer limit point trajectory PLT of the active power transfer limit with respect to the line reactance X and the active power transfer limit point trajectory PLT of the active power transfer limit with respect to the reactive power Q , the following conclusions can be obtained, as Figure 3 and Figure 4 shown:

[0074] (1) PLT X has good linear properties, and its extension line basically passes through the origin of coordinates;

[0075] (2) PLT Q has linear properties within a certain range, and the linear properties are not as good as those of PLT X .

[0076] Based on PLTX It has the characteristics of passing through the origin and high linearity. According to the relationship between the slopes of the measured active power and current and the set slope, it can be judged whether the system operation approaches the nose point. If the operating state reaches the nose point, control measures can be taken to prevent voltage instability. PLT Q For PLT X The influence on the internal potential V0 is as follows:

[0077] (1) If during the fault, the reactive power provided by the equipment (including the reactive power compensation device) is greater than 0.5 per unit value, then correct PLT X to

[0078] (2) If during the fault, the reactive power provided by the equipment (including the reactive power compensation device) is less than 0.5 per unit value, then ignore the influence of reactive power compensation on PLT X and PLT X still takes

[0079] When the actual slope is greater than the preset slope, that is, when the system operates on the left side of PLT X , control the power electronic converter equipment in the general constant power mode; when reaching the nose point, automatically switch to the constant PLT X trajectory input mode. When the system recovers from the fault, a monostable time delay is used to switch back to the normal constant power control mode.

[0080] In addition, if the actual slope is less than or equal to the preset slope then automatically switch the constant power control to PLT X control. Specifically, it is to switch the active power measurement input of the outer loop to the constant PLT X trajectory input mode.

[0081] From the above technical solutions, it can be seen that this embodiment provides a control method for a power electronic converter device. This method is applied to the main controller, specifically to collect the active power and total current values at the outlet side of the high-voltage direct current transmission system; calculate the actual slope according to the active power and the total current value; execute a predetermined control scheme for the power electronic converter device according to the actual slope and the set slope. This solution does not require knowing the actual network-side parameters. Only based on the detection of the electrical quantities at the outlet side of the device and by comparing the measured data with the set criterion conditions, the control of the power electronic converter device can be realized, ensuring the voltage stability of the high-voltage direct current transmission system.

[0082] Based on this solution, a specific implementation example is proposed here:

[0083] (1) In PSCAD / EMTDC, based on the DC transmission Benchmark model, a control structure is constructed as shown in Figure 5 . A 0.5H inductive grounding fault is set to occur at the point of common coupling for 0.2s. Figure 6 are the time-domain simulation curves of the active power and the device terminal voltage without control switching. It can be seen that due to commutation failure, the system active power drops to 0 and the voltage collapses; Figure 7 are the time-domain simulation curves of the active power and the device terminal voltage after control switching. It can be seen that due to the construction of the operating equilibrium point, the active power and voltage are maintained at a relatively high level. And as the fault is cleared, the control switches back to the constant power control (the purple line jumps from low to high), and the system returns to the normal operating state. (The preset slope is )

[0084] (2) In MATLAB / Simulink, based on a typical doubly-fed wind turbine model, a control structure is constructed as shown in Figure 8 (the Signal signal represents the signal triggering control switching, and inside the d-axis current control, the method of restricting the PI link input is adopted). The removal of an external feeder with an inductance of 10e-4H is set to occur for 0.2s. Figure 9 is the time-domain simulation curve of the 575V device port bus without control switching. It can be seen that due to the sudden reduction of the system strength, the voltage gets out of control and undergoes large-amplitude oscillations; Figure 10 is the time-domain simulation curve of the 575V device port bus after control switching. It can be seen that due to the construction of the operating equilibrium point, the voltage is maintained at a relatively high level. And as the fault is cleared, the control switches back to the original control, and the system returns to the normal operating state. (The preset slope is )

[0085] Embodiment 2

[0086] Figure 11 is a block diagram of a control device for an electronic power conversion device according to an embodiment of the present application.

[0087] As shown in Figure 11 , the control device provided in this embodiment is applied to the main control device of a high-voltage DC transmission system and is used to control the power electronic conversion device therein. The control device includes a parameter acquisition module 10, a slope calculation module 20, and a control execution module 30.

[0088] The parameter acquisition module is used to acquire the active power and the total current value at the outlet side.

[0089] That is, the active power and the total current value at the outlet side are obtained from detection devices such as current sensors and voltage sensors provided at the outlet side of the high-voltage DC transmission system.

[0090] The slope calculation module is used to calculate the actual slope according to the active power and the total current value.

[0091] The calculation method is to divide the active power by the total current value, and the quotient obtained is the actual slope.

[0092] The control execution module is used to execute a predetermined control scheme according to the actual slope and the set slope. The control execution module specifically includes a first control unit and a second control unit.

[0093] The first control unit is used to control the power electronic converter device in the general constant power mode when the actual slope is greater than the preset slope, that is, when the system is operating on the left side of the PLT X ; when reaching the nose point, automatically switch to the constant PLT X trajectory input mode. When the system recovers from a fault, a monostable time delay is used to switch back to the normal constant power control mode.

[0094] The second control unit is used to automatically switch the constant power control to the PLT control when the actual slope is less than or equal to the preset slope X Specifically, it is to switch the active power measurement input of the outer loop to the constant PLT X trajectory input mode.

[0095] As can be seen from the above technical solution, this embodiment provides a control device for a power electronic converter device, which is applied to a main controller, specifically to collect the active power and the total current value at the outlet side of the high-voltage direct current transmission system; calculate the actual slope according to the active power and the total current value; execute a predetermined control scheme on the power electronic converter device according to the actual slope and the set slope. This solution does not need to know the actual network-side parameters, and only needs to detect the electrical quantities at the outlet side of the device, and compare the measured data with the set criterion conditions to realize the control of the power electronic converter device, ensuring the voltage stability of the high-voltage direct current transmission system.

[0096] Embodiment III

[0097] This embodiment provides a main controller, which is applied to a high-voltage direct current (HVDC) transmission system and is used to control the power electronic converter equipment in the system. The main controller is provided with the control device disclosed in the previous embodiment, which is specifically used to collect the active power and total current value at the outlet side of the HVDC transmission system; calculate the actual slope according to the active power and the total current value; and execute a predetermined control scheme for the power electronic converter equipment according to the actual slope and the set slope. This solution does not require knowledge of the actual network-side parameters. Based only on the detection of the electrical quantities at the outlet side of the equipment, by comparing the measured data with the set criterion conditions, the control of the power electronic converter equipment can be achieved, ensuring the voltage stability of the HVDC transmission system.

[0098] Embodiment 4

[0099] Figure 12 It is a block diagram of a main controller according to an embodiment of the present application.

[0100] As Figure 12 shown, the main controller provided in this embodiment is applied to an HVDC transmission system and is used to control the power electronic converter equipment in the system. The main controller includes at least one processor 101 and a memory 102, which are connected through a data bus 103. The memory is used to store computer programs or instructions; the processor is used to execute calculations and programs or instructions so that the main controller can implement the control method of the power electronic equipment as described in Embodiment 1.

[0101] The specific control method is to collect the active power and total current value at the outlet side of the HVDC transmission system; calculate the actual slope according to the active power and the total current value; and execute a predetermined control scheme for the power electronic converter equipment according to the actual slope and the set slope. This solution does not require knowledge of the actual network-side parameters. Based only on the detection of the electrical quantities at the outlet side of the equipment, by comparing the measured data with the set criterion conditions, the control of the power electronic converter equipment can be achieved, ensuring the voltage stability of the HVDC transmission system.

[0102] The embodiments in this specification are all described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0103] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, devices, or computer program products. Therefore, the embodiments of the present invention can take the form of all-hardware embodiments, all-software embodiments, or embodiments combining software and hardware aspects. Moreover, the embodiments of the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0104] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of methods, terminal devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing terminal devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing terminal devices generate a device for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0105] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing terminal device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0106] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device, such that a series of operation steps are executed on the computer or other programmable terminal device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable terminal device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0107] Although the preferred embodiments of the embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0108] Finally, it should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or terminal device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or terminal device comprising the said element.

[0109] The technical solutions provided by the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A control method for a power electronic converter device, which is applied to a main controller. The main controller is used to control the power electronic converter device of a high-voltage direct current transmission system, and is characterized in that, The control method includes the steps of: collecting the active power and the total current value at the outlet side of the high-voltage direct current (HVDC) transmission system; calculating an actual slope according to the active power and the total current value; when the actual slope is greater than a set slope, controlling the power electronic converter device to operate in a constant power control mode; When the actual slope is less than or equal to the set slope, switch the active power measurement input to the fixed PLT X The trajectory input mode controls the power electronic converter device, and the PLT X The trajectory is the limit relationship curve of the active power calculated according to the internal potential of the system and the line reactance and the total current value.

2. The control method according to claim 1, wherein The step of controlling the power electronic converter device to operate in a constant power control mode includes the steps of: when the HVDC transmission system recovers from a fault, entering the constant power control mode by using a monostable time delay method.

3. The control method according to claim 1, wherein, The set slope is or , where V O is the electric potential within the system.

4. The control method according to claim 3, wherein, If the reactive power of the HVDC transmission system during a fault is greater than 0.5 per unit value, the set slope is ; If the reactive power of the HVDC transmission system during a fault is less than 0.5 per unit value, the set slope is .

5. A control device for a power electronic converter device, applied to a main controller, where the main controller is used to control the power electronic converter device of a high-voltage direct current transmission system, and is characterized in that, The control device includes: a parameter acquisition module configured to collect the active power and the total current value at the outlet side of the HVDC transmission system; a slope calculation module configured to calculate an actual slope according to the active power and the total current value; a control execution module configured to execute a predetermined control scheme on the power electronic converter device according to the actual slope and the set slope; The control execution module includes: a first control unit configured to control the power electronic converter device to operate in a constant power control mode when the actual slope is greater than the set slope; A second control unit, configured to switch the active power measurement input to the fixed PLT when the actual slope is less than or equal to the set slope X The trajectory input mode controls the power electronic conversion device, and the PLT X The trajectory is the limit relationship curve of the active power calculated according to the internal potential of the system and the line reactance and the total current value.

6. The control device according to claim 5, wherein The first control unit is further configured to enter the constant power control mode by using a monostable time delay method when the HVDC transmission system recovers from a fault.

7. The control device according to claim 5, characterized in that The set slope is or , where V O is the electric potential within the system.

8. The control device according to claim 7, characterized in that, If the reactive power of the HVDC transmission system during a fault is greater than 0.5 per unit value, the set slope is ; If the reactive power of the HVDC transmission system during a fault is less than 0.5 per unit value, the set slope is .

9. A main controller, characterized in that, There is provided a control device for a power electronic converter device according to any one of claims 5 to 8.

10. A main controller, characterized in that, It includes at least one processor and a memory connected to the processor, wherein: the memory is used for storing computer programs or instructions; the processor is used for executing the computer programs or instructions so that the main controller implements the control method for a power electronic device according to any one of claims 1 to 4.

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