CN111654032A - Control method of straight-string module type energy consumption device - Google Patents

Control method of straight-string module type energy consumption device Download PDF

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Publication number
CN111654032A
CN111654032A CN202010463041.XA CN202010463041A CN111654032A CN 111654032 A CN111654032 A CN 111654032A CN 202010463041 A CN202010463041 A CN 202010463041A CN 111654032 A CN111654032 A CN 111654032A
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voltage
power semiconductor
direct
semiconductor device
string
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CN111654032B (en
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谢晔源
姚宏洋
田杰
王宇
李钊
袁庆伟
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NR Electric Co Ltd
NR Engineering Co Ltd
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NR Electric Co Ltd
NR Engineering Co Ltd
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Priority to PCT/CN2021/087876 priority patent/WO2021238498A1/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Direct Current Feeding And Distribution (AREA)

Abstract

The application provides a control method of a straight-string module type energy consumption device. The direct-string module type energy consumption device is connected between direct-current lines in parallel and comprises M direct-string modules and energy consumption resistors which are connected in series; the direct-series module comprises a first power semiconductor device and a voltage clamping unit; the voltage clamping unit comprises an energy storage unit and a discharge unit, and the energy storage unit is connected with the first power semiconductor device in parallel; the discharge unit comprises a second power semiconductor and an equalizing resistor which are connected in series; the control method comprises the following steps: when the voltage of the direct current line is normal, the control device is in a standby mode, part of the second power semiconductor devices are switched on or off, or part of the first power semiconductor devices and the second power semiconductor devices are simultaneously switched on or off, so that the capacitance voltage of the direct current string module is adjusted; when the voltage of the direct current line reaches a starting threshold value, the control device is in an energy consumption mode, the control device is started to control the input and the exit of the energy consumption resistor, and the voltage of the direct current line is adjusted.

Description

Control method of straight-string module type energy consumption device
Technical Field
The application relates to the technical field of power electronics, in particular to a control method of a straight-string module type energy consumption device.
Background
The method has clear standard requirements for the new energy grid-connected low-voltage ride through capability at home and abroad. For a new energy system which is grid-connected by adopting a high-voltage flexible direct-current transmission technology, as shown in fig. 1, for example, a power generation end is an inertial power supply similar to wind power, when a power receiving end fails to cause voltage drop of an alternating-current power grid, active power cannot be sent out or only part of the active power can be sent out to the alternating-current power grid due to the fact that a transmitting-end converter is in power control, surplus active power causes voltage rise of a direct-current transmission line, and safety of equipment such as a flexible direct-current converter valve is damaged.
Usually, a dc energy consuming device is added to the dc line to consume excess energy and limit the dc line voltage. In the prior art, power semiconductor devices are directly connected in series to be applied to a direct current energy consumption device. When the direct current voltage is too high, the resistor is put in through the control of the power electronic device, the direct current voltage is reduced due to the putting in of the resistor, when the energy consumption speed of the resistor exceeds the speed of accumulating energy at the direct current side, the direct current voltage is reduced, at the moment, the resistor discharge loop is switched off, the direct current voltage is increased again, and the resistor branch is switched on and off repeatedly, so that the hysteresis control effect is formed.
The main problems of the method are that: when the resistance discharge loop is turned off, because the simultaneous turn-off of a plurality of power semiconductor switching devices is difficult to ensure consistency, once the turn-off is asynchronous, a device which is slowly turned on or a device which is quickly turned off bears overvoltage and is damaged. How to ensure the balance of the module direct current voltage under the condition of asynchronous turn-off is lack of an effective control method in the prior art, so that a plurality of problems exist in practical application and the realization of engineering is not facilitated.
Disclosure of Invention
The embodiment of the application provides a control method of a direct-string modular energy consumption device, wherein the direct-string modular energy consumption device is connected in parallel between direct-current lines and comprises M direct-string modules and energy consumption resistors which are connected in series, and M is an integer greater than or equal to 2; the direct-series module comprises a first power semiconductor device and a voltage clamping unit; the voltage clamping unit comprises an energy storage unit and a discharging unit, the energy storage unit is connected with the first power semiconductor device in parallel, and the energy storage unit comprises a capacitor and a third power semiconductor device which are connected in series; the discharge unit is connected in parallel to two ends of the capacitor or the third power semiconductor device and comprises a second power semiconductor and an equalizing resistor which are connected in series; the working modes of the device comprise a standby mode and an energy consumption mode, and the control method comprises the following steps: when the voltage of the direct current line is normal, controlling the device to be in a standby mode, and switching on or switching off a second power semiconductor device of a part of direct-current string modules, or simultaneously switching on or switching off a first power semiconductor device and a second power semiconductor device of the part of direct-current string modules so as to adjust the capacitance voltage of the direct-current string modules; and when the voltage of the direct current line reaches a starting threshold value, controlling the device to be in an energy consumption mode, starting the device, controlling the input and the exit of the energy consumption resistor, and regulating the voltage of the direct current line.
According to some embodiments, when the apparatus is in a standby mode, the second power semiconductor device of the partial straight string module in the apparatus is turned on or off, or the first power semiconductor device and the second power semiconductor device of the partial straight string module in the apparatus are controlled to be simultaneously turned on or off, so as to adjust the capacitance voltage of the straight string module, including: repeating the following steps to keep the capacitance voltage of all the direct string modules stable between the capacitance voltage first threshold and the capacitance voltage second threshold: when the capacitance voltage of the direct string module is larger than a first threshold value of the capacitance voltage, switching on a second power semiconductor device of the direct string module, or simultaneously switching on a first power semiconductor device and a second power semiconductor device of the direct string module, and the capacitance voltage of the direct string module begins to drop; and when the capacitance voltage of the direct string module is smaller than a second threshold value of the capacitance voltage, turning off a second power semiconductor device of the direct string module, or simultaneously turning off a first power semiconductor device and a second power semiconductor device of the direct string module.
According to some embodiments, in the standby mode, the number of the direct string modules of the first power semiconductor device in the off state is less than or equal to M.
According to some embodiments, the energy consumption modes include an offline energy consumption mode in which the second power semiconductor device remains in an off state and an online energy consumption mode; in the line energy consumption mode, the second power semiconductor device is switched on and off according to the capacitance voltage of the straight string module.
According to some embodiments, said activating said device while said device is in said offline power consumption mode, controlling the putting in and out of power consumption resistors, comprises: when the voltage of the direct current line reaches a starting threshold value, starting the device, and turning on all the first power semiconductor devices of the direct current string module; when the direct current line voltage reaches a first threshold value of the line voltage, the device is withdrawn, and all the first power semiconductor devices of the direct string modules are turned off; when the direct current line voltage reaches a second threshold value of the line voltage, starting the device, and turning on all the first power semiconductor devices of the direct series module; and the device enters a standby mode until the working duration of the device reaches the required energy consumption time or the external fault is eliminated, and the voltage of the direct current line is recovered to a normal range.
According to some embodiments, the online energy consumption mode comprises a hysteresis control mode and a double closed loop control mode, in the hysteresis control mode, the direct current line voltage is controlled between a first line voltage threshold and a second line voltage threshold by controlling the on and off of the first power semiconductor device, and the capacitance voltage is controlled between a first capacitance voltage threshold and a second capacitance voltage threshold by controlling the on and off of the second power semiconductor device; in the double closed-loop control mode, the on and off of the first power semiconductor device are controlled in a closed-loop mode through the voltage of the direct current line, the voltage of the direct current line is controlled at a line voltage target value, the on and off of the second power semiconductor device are controlled in a closed-loop mode through the voltage of the module capacitor, and the voltage of the direct current capacitor is controlled at a capacitor voltage target value.
According to some embodiments, said activating said device while said device is in said hysteresis control mode, controlling the putting in and out of dissipative resistors, comprises: when the voltage of the direct current line reaches a starting threshold value, starting the device, and simultaneously or sequentially turning on the first power semiconductor devices of all the direct-current series modules; when the direct current line voltage reaches a first threshold value of the line voltage, the device is withdrawn, and the first power semiconductor devices of all the direct string modules are turned off simultaneously or sequentially; when the direct current line voltage reaches a second threshold value of the line voltage, starting the device, simultaneously turning on the first power semiconductor devices of all the direct string modules or sequentially turning on the first power semiconductor devices, calculating the turning-on time of the second power semiconductor devices in each direct string module, and turning on the second power semiconductor devices according to the turning-on time; and the device enters a standby mode until the working duration of the device reaches the required energy consumption time or the external fault is eliminated and the voltage of the direct current line is recovered to a normal range.
According to some embodiments, the calculation formula of the on-time t of the second power semiconductor device is as follows:
t＝RC·ln(V0/Vt)
wherein R is the resistance of the equalizing resistor, C is the capacitance of the capacitor, and V0Is the initial voltage of the capacitor, VtIs the target value of the capacitor voltage.
According to some embodiments, when the device is in the dual closed-loop control mode, the activating the device, controlling the firing and the exiting of the dissipative resistance, regulating the dc link voltage, comprises: starting the device when the direct current line voltage reaches a starting threshold; sending error signals of a line voltage target value and a line voltage feedback value into a PI regulator, and controlling the on and off of each first power semiconductor device according to the output value of the regulator; sending error signals of the capacitor voltage target value and the capacitor voltage feedback value into a PI (proportional-integral) regulator, and controlling the on and off of each second power semiconductor device according to the output value of the regulator; and the device enters a standby mode until the working duration of the device reaches the required energy consumption time or the external fault is eliminated and the voltage of the direct current line is recovered to a normal range.
According to some embodiments, when more than one of the first power semiconductor devices perform on or off at the same time, the first power semiconductor devices are sequentially on or sequentially off.
According to some embodiments, the sequentially turning on comprises: sequencing the capacitor voltage of each direct-string module, and sequentially selecting the first power semiconductors corresponding to the N direct-string modules with the highest capacitor voltage to be switched on, wherein N is an integer larger than 1 and smaller than M; the sequentially turning off comprises: and sequencing the capacitor voltages of the direct-string modules, and sequentially selecting the first power semiconductors corresponding to the N direct-string module capacitors with the lowest capacitor voltages to turn off, wherein N is an integer larger than 1 and smaller than M.
According to the technical scheme provided by the embodiment of the application, in a standby mode, a part of direct-current series modules are turned on in turn, so that the voltage balance of the sub-modules is ensured in a normal range of the voltage of a direct-current line, and meanwhile, the voltage of the direct-current line is stabilized by utilizing the clamping effect of a capacitor; under the energy consumption mode, an off-line energy consumption mode and an on-line energy consumption mode are provided, the on-line energy consumption mode comprises two modes of hysteresis control and double closed-loop control, and when energy is consumed, a first power semiconductor device and a second power semiconductor device of the energy consumption device are respectively controlled, so that the accurate control of the voltage of a direct current line is realized, and the capacitor voltage of a direct-current series module is ensured to be in a normal range.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a typical application scenario of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 2 is a schematic view of a topology structure of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 3 is a second schematic view of a topology structure of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 4 is a schematic flowchart of a method for controlling a straight-string module energy consumption device according to an embodiment of the present application.
Fig. 5 is a control mode diagram of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 6 is a flowchart illustrating a method for controlling a standby mode of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 7 is a schematic view illustrating a control effect of a straight-string modular energy consumption device in a standby mode according to an embodiment of the present application.
Fig. 8 is a schematic flowchart of a method for controlling an offline energy consumption mode of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 9 is a schematic flowchart of a control method of a hysteresis control mode of a straight-string module type energy consumption device according to an embodiment of the present application.
Fig. 10 is a schematic diagram of a control effect of a hysteresis control mode of a straight-string module energy consumption device according to an embodiment of the present application.
Fig. 11 is a schematic flowchart of a control method of a dual closed-loop control mode of a straight-string modular energy consumption device according to an embodiment of the present application.
Fig. 12 is a block diagram of a control strategy of a dual closed-loop control mode of a straight-string modular energy consumption device according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be understood that the terms "first," "second," "third," and the like in the claims, the description, and the drawings of the present application are used for distinguishing between different objects and not for describing a particular order. The terms "comprises" and "comprising," when used in the specification and claims of this application, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Fig. 2 is a schematic view of a topology structure of a straight-string modular energy consumption device according to an embodiment of the present application.
As shown in fig. 2, the dc-string module energy dissipation device 20 is connected in parallel between the dc lines, and includes M dc-string modules 1 and energy dissipation resistors 7 connected in series, where M is an integer greater than or equal to 2. The direct string module 1 comprises a first power semiconductor device 2 and a voltage clamping unit. The voltage clamping unit comprises an energy storage unit and a discharge unit. The energy storage unit is connected in parallel with the first power semiconductor device 2 and comprises a capacitor 3 and a third power semiconductor device 6 which are connected in series.
The discharge unit is connected in parallel across the third power semiconductor device 6 and comprises a second power semiconductor 4 and an equalizing resistor 5 connected in series.
Fig. 3 is a second schematic view of a topology structure of a straight-string modular energy consumption device according to an embodiment of the present application.
As shown in fig. 3, the dc-string module energy dissipation device 20 is connected in parallel between the dc lines, and includes M dc-string modules 1 and energy dissipation resistors 7 connected in series, where M is an integer greater than or equal to 2. The direct string module 1 comprises a first power semiconductor device 2 and a voltage clamping unit. The voltage clamping unit comprises an energy storage unit and a discharge unit. The energy storage unit is connected in parallel with the first power semiconductor device 2 and comprises a capacitor 3 and a third power semiconductor device 6 which are connected in series.
The discharging unit is connected in parallel to two ends of the capacitor 3, and comprises a second power semiconductor 4 and an equalizing resistor 5 which are connected in series.
Fig. 4 is a schematic flowchart of a control method for a straight-string modular energy consumption device according to an embodiment of the present application, where an operating mode of the device includes a standby mode and an energy consumption mode.
In S110, when the voltage of the dc line is normal, the energy consuming apparatus is in a standby mode, and the second power semiconductor device of the partial dc-serial module in the apparatus is turned on or off, or the first power semiconductor device and the second power semiconductor device of the partial dc-serial module in the apparatus are controlled to be turned on or off simultaneously, so as to adjust the capacitor voltage of the dc-serial module.
And in the standby mode, the number of the direct-current series modules of the first power semiconductor device in the off state is less than or equal to M.
In S120, when the dc line voltage reaches the start threshold, the energy consumption device is in the energy consumption mode, and the device is started to control the input and the exit of the energy consumption resistor, consume surplus energy on the dc line, and regulate the dc line voltage.
The energy consumption modes include an offline energy consumption mode and an online energy consumption mode, as shown in fig. 5. In the offline power consumption mode, the second power semiconductor device remains in an off state. In the online energy consumption mode, the second power semiconductor device is switched on and off according to the capacitance voltage of the straight-string module.
The online energy consumption mode includes a hysteresis control mode and a double closed loop control mode, as shown in fig. 5. In a hysteresis control mode, the direct current line voltage is controlled between a first line voltage threshold and a second line voltage threshold by controlling the on and off of the first power semiconductor device, and the capacitor voltage is controlled between the first capacitor voltage threshold and the second capacitor voltage threshold by controlling the on and off of the second power semiconductor device.
In the double closed-loop control mode, the on and off of the first power semiconductor device are controlled in a closed-loop mode through the voltage of the direct current line, the voltage of the direct current line is controlled at a line voltage target value, the on and off of the second power semiconductor device are controlled in a closed-loop mode through the voltage of the module capacitor, and the voltage of the direct current capacitor is controlled at a capacitor voltage target value.
According to the technical scheme provided by the embodiment, in the standby mode, a part of direct-current serial modules are turned on in turn, so that the voltage balance of the sub-modules is ensured in the normal range of the voltage of the direct-current line, and meanwhile, the voltage of the direct-current line is stabilized by utilizing the clamping effect of the capacitor; under the energy consumption mode, an off-line energy consumption mode and an on-line energy consumption mode are provided, the on-line energy consumption mode comprises two modes of hysteresis control and double closed-loop control, the first power semiconductor device and the second power semiconductor device of the energy consumption device are respectively controlled, the voltage of a direct current line is accurately controlled, and the capacitor voltage of the direct-current series module is ensured to be in a normal range.
Fig. 6 is a flowchart illustrating a method for controlling a standby mode of a straight-string modular energy consumption device according to an embodiment of the present application.
S110 of the embodiment of fig. 4 includes the following control flow when the device is in the standby mode.
And repeating the following steps to keep the capacitance voltage of all the direct-current string modules stable between the first capacitance voltage threshold and the second capacitance voltage threshold.
In S111, when the capacitor voltage of the dc-serial module is greater than the first threshold of the capacitor voltage, the dc-serial module or the apparatus issues a command to turn on the second power semiconductor device of the dc-serial module, or turn on the first power semiconductor device and the second power semiconductor device of the dc-serial module at the same time, so that the capacitor voltage of the dc-serial module starts to decrease.
In S112, when the capacitor voltage of the dc-serial module is smaller than the second threshold of the capacitor voltage, the dc-serial module or the apparatus issues a command to turn off the second power semiconductor device of the dc-serial module, or turn off the first power semiconductor device and the second power semiconductor device of the dc-serial module at the same time.
The control effect of this embodiment is as shown in fig. 7, and the capacitor voltage in the direct string module is controlled between the capacitor voltage first threshold and the capacitor voltage second threshold.
According to the technical scheme, under the standby mode, a part of direct-current serial modules are turned on in turn, voltage balance of the sub-modules is guaranteed when the voltage of the direct-current line is within a normal range, and meanwhile, the voltage of the direct-current line is stabilized by the clamping effect of the capacitor.
Fig. 8 is a schematic flowchart of a method for controlling an offline energy consumption mode of a straight-string modular energy consumption device according to an embodiment of the present application.
When the apparatus is in the offline energy consumption mode, S120 of the embodiment of fig. 4 includes the following control flows.
In S121, when the dc line voltage reaches the start threshold, the device is started, and all the first power semiconductor devices of all the dc link modules are turned on.
In S122, when the dc line voltage reaches the first threshold of the line voltage, the apparatus is withdrawn, and all the first power semiconductor devices of all the dc link modules are turned off.
In S123, when the dc line voltage reaches the second threshold of the line voltage, the apparatus is activated, and all the first power semiconductor devices of all the dc link modules are turned on.
And repeating the steps S122 and S123 until the working duration of the device reaches the required energy consumption time or the external fault is eliminated, the voltage of the direct current line is recovered to the normal range, and the device enters a standby mode.
According to the technical scheme provided by the embodiment, in the off-line energy consumption mode, the first power semiconductor device of the energy consumption device is controlled, the accurate control of the voltage of the direct current line is realized, and the capacitor voltage of the direct current series module is ensured to be in a normal range.
Fig. 9 is a schematic flowchart of a control method of a hysteresis control mode of a straight-string module type energy consumption device according to an embodiment of the present application.
When the apparatus is in the hysteresis control mode of the online energy consumption mode, S120 of the embodiment of fig. 4 includes the following control procedures.
In S124, when the dc line voltage reaches the start threshold, the device is started, and the first power semiconductor devices of all the dc-serial modules are turned on simultaneously or sequentially.
The opening in proper order includes: and sequencing the capacitor voltages of the direct-string modules, and sequentially selecting the first power semiconductors corresponding to the N direct-string modules with the highest capacitor voltages to turn on, wherein N is an integer which is greater than 1 and smaller than M.
In S125, when the dc line voltage reaches the first threshold of the line voltage, the device is withdrawn, and the first power semiconductor devices of all the dc string modules are turned off simultaneously or sequentially.
The sequentially turning off comprises: and sequencing the capacitor voltages of the direct-string modules, and sequentially selecting the first power semiconductors corresponding to N direct-string module capacitors with the lowest capacitor voltages to turn off, wherein N is an integer larger than 1 and smaller than M.
In S126, when the dc line voltage reaches the second threshold of the line voltage, the device is activated, the first power semiconductor devices of all the dc-serial modules are turned on simultaneously or sequentially, the turn-on time of the second power semiconductor device in each dc-serial module is calculated, and the turn-on is performed according to the turn-on time.
The calculation formula of the on-time t of the second power semiconductor device is as follows:
t＝RC·ln(V0/Vt)
wherein R is the resistance of the equalizing resistor, C is the capacitance of the capacitor, and V0Is the initial voltage of the capacitor, VtIs the target value of the capacitor voltage.
And repeating the steps S125 and S126 until the working duration of the device reaches the required energy consumption time or the external fault is eliminated, the voltage of the direct current line is recovered to the normal range, and the device enters a standby mode. The hysteresis control effect is shown in fig. 10.
According to the technical scheme provided by the embodiment, the first power semiconductor device and the second power semiconductor device of the energy consumption device are respectively controlled in the hysteresis control mode, so that the accurate control of the direct current line voltage is realized, the capacitor voltage of the direct string module is ensured to be in a normal range, the strategy of sequencing on and off based on the capacitor voltage is adopted, the soft switching is realized, the overhigh voltage and current change rate is avoided, and the safe operation of the device is ensured.
Fig. 11 is a schematic flowchart of a control method of a dual closed-loop control mode of a straight-string modular energy consumption device according to an embodiment of the present application.
When the apparatus is in the dual closed-loop control mode of the online energy consumption mode, S120 of the embodiment of fig. 4 includes the following control procedures.
In S127, when the dc line voltage reaches the activation threshold, the device is activated.
In S128, the error signal of the line voltage target value and the line voltage feedback value is sent to the PI regulator, and the on/off of each first power semiconductor device is controlled according to the regulator output value, as shown in fig. 12.
When more than one first power semiconductor device simultaneously performs on or off, the first power semiconductor devices are sequentially on or sequentially off.
The opening in proper order includes: and sequencing the capacitor voltages of the direct-string modules, and sequentially selecting the first power semiconductors corresponding to the N direct-string modules with the highest capacitor voltages to turn on, wherein N is an integer which is greater than 1 and smaller than M.
The sequentially turning off comprises: and sequencing the capacitor voltages of the direct-string modules, and sequentially selecting the first power semiconductors corresponding to N direct-string module capacitors with the lowest capacitor voltages to turn off, wherein N is an integer larger than 1 and smaller than M.
In S129, the error signal of the capacitor voltage target value and the capacitor voltage feedback value is sent to the PI regulator, and the on/off of each second power semiconductor device is controlled according to the regulator output value, as shown in fig. 12.
And repeating the steps S128 and S129 until the working duration of the device reaches the required energy consumption time or the external fault is eliminated, the voltage of the direct current line is recovered to the normal range, and the device enters a standby mode.
According to the technical scheme provided by the embodiment, under a double closed-loop control mode, the first power semiconductor device and the second power semiconductor device of the energy consumption device are respectively controlled, the accurate control of the voltage of a direct current line is realized, the capacitor voltage of a direct string module is ensured to be in a normal range, a strategy of sequencing on and off based on the capacitor voltage is adopted, a 'soft switch' is realized, the overhigh voltage and current change rate is avoided, and the safe operation of the device is ensured.
The foregoing detailed description of the embodiments of the present application has been presented to illustrate the principles and implementations of the present application, and the description of the embodiments is only intended to facilitate the understanding of the methods and their core concepts of the present application. Meanwhile, a person skilled in the art should, according to the idea of the present application, change or modify the embodiments and applications of the present application based on the scope of the present application. In view of the above, the description should not be taken as limiting the application.

Claims (11)

1. A control method of a direct-string modular energy consumption device is characterized in that the direct-string modular energy consumption device is connected in parallel between direct-current lines and comprises M direct-string modules and energy consumption resistors which are connected in series, wherein M is an integer greater than or equal to 2; the direct-series module comprises a first power semiconductor device and a voltage clamping unit; the voltage clamping unit comprises an energy storage unit and a discharging unit, the energy storage unit is connected with the first power semiconductor device in parallel, and the energy storage unit comprises a capacitor and a third power semiconductor device which are connected in series; the discharge unit is connected in parallel to two ends of the capacitor or the third power semiconductor device and comprises a second power semiconductor and an equalizing resistor which are connected in series; the working modes of the device comprise a standby mode and an energy consumption mode, and the control method comprises the following steps:
when the voltage of the direct current line is normal, controlling the device to be in a standby mode, and switching on or switching off a second power semiconductor device of a part of direct-current string modules, or simultaneously switching on or switching off a first power semiconductor device and a second power semiconductor device of the part of direct-current string modules so as to adjust the capacitance voltage of the direct-current string modules;
and when the voltage of the direct current line reaches a starting threshold value, controlling the device to be in an energy consumption mode, starting the device, controlling the input and the exit of the energy consumption resistor, and regulating the voltage of the direct current line.
2. The control method according to claim 1, wherein when the apparatus is in a standby mode, the second power semiconductor device of the partial dc link module in the apparatus is turned on or off, or the first power semiconductor device and the second power semiconductor device of the partial dc link module in the apparatus are controlled to be turned on or off simultaneously, so as to adjust the capacitance voltage of the dc link module, the method comprising:
repeating the following steps to keep the capacitance voltage of all the direct string modules stable between the capacitance voltage first threshold and the capacitance voltage second threshold:
when the capacitance voltage of the direct string module is larger than a first threshold value of the capacitance voltage, switching on a second power semiconductor device of the direct string module, or simultaneously switching on a first power semiconductor device and a second power semiconductor device of the direct string module, and the capacitance voltage of the direct string module begins to drop;
and when the capacitance voltage of the direct string module is smaller than a second threshold value of the capacitance voltage, turning off a second power semiconductor device of the direct string module, or simultaneously turning off a first power semiconductor device and a second power semiconductor device of the direct string module.
3. The control method according to claim 1, wherein the number of the direct-string modules of the first power semiconductor device in the off state in the standby mode is less than or equal to M.
4. The control method of claim 1, wherein the energy consumption mode comprises:
an off-line power consumption mode, wherein the second power semiconductor device is kept in an off state;
in an online energy consumption mode, the second power semiconductor device is switched on and off according to the capacitor voltage of the direct-connected module.
5. The control method of claim 4, wherein said activating the device, controlling the firing and firing of dissipative resistors, and regulating the DC link voltage while the device is in the offline dissipative mode comprises:
when the voltage of the direct current line reaches a starting threshold value, starting the device, and turning on all the first power semiconductor devices of the direct current string module;
when the direct current line voltage reaches a first threshold value of the line voltage, the device is withdrawn, and all the first power semiconductor devices of the direct string modules are turned off;
when the direct current line voltage reaches a second threshold value of the line voltage, starting the device, and turning on all the first power semiconductor devices of the direct series module;
and the device enters a standby mode until the working duration of the device reaches the required energy consumption time or the external fault is eliminated, and the voltage of the direct current line is recovered to a normal range.
6. The control method of claim 4, wherein the online energy consumption mode comprises:
a hysteresis control mode, wherein the direct current line voltage is controlled between a first line voltage threshold and a second line voltage threshold by controlling the on and off of the first power semiconductor device, and the capacitance voltage is controlled between the first capacitance voltage threshold and the second capacitance voltage threshold by controlling the on and off of the second power semiconductor device;
and in the double closed-loop control mode, the on and off of the first power semiconductor device are controlled in a closed-loop mode through the voltage of the direct current line, the voltage of the direct current line is controlled at a line voltage target value, the on and off of the second power semiconductor device are controlled in a closed-loop mode through the voltage of the module capacitor, and the voltage of the direct current capacitor is controlled at a capacitor voltage target value.
7. The control method of claim 6, wherein said activating the device to control the firing and the exiting of the dissipative resistance when the device is in the hysteresis control mode comprises:
when the voltage of the direct current line reaches a starting threshold value, starting the device, and simultaneously or sequentially turning on the first power semiconductor devices of all the direct-current series modules;
when the direct current line voltage reaches a first threshold value of the line voltage, the device is withdrawn, and the first power semiconductor devices of all the direct string modules are turned off simultaneously or sequentially;
when the direct current line voltage reaches a second threshold value of the line voltage, starting the device, simultaneously turning on the first power semiconductor devices of all the direct string modules or sequentially turning on the first power semiconductor devices, calculating the turning-on time of the second power semiconductor devices in each direct string module, and turning on the second power semiconductor devices according to the turning-on time;
and the device enters a standby mode until the working duration of the device reaches the required energy consumption time or the external fault is eliminated and the voltage of the direct current line is recovered to a normal range.
8. The control method according to claim 7, wherein the calculation formula of the on-time t of the second power semiconductor device is as follows:
t＝RC·ln(V0/Vt)
wherein R is the resistance of the equalizing resistor, C is the capacitance of the capacitor, and V0Is the initial voltage of the capacitor, VtIs the target value of the capacitor voltage.
9. The control method of claim 6, wherein said activating the device, controlling the firing and firing of dissipative resistors, and regulating the dc link voltage while the device is in the dual closed-loop control mode comprises:
starting the device when the direct current line voltage reaches a starting threshold;
sending error signals of a line voltage target value and a line voltage feedback value into a PI regulator, and controlling the on and off of each first power semiconductor device according to the output value of the regulator;
sending error signals of the capacitor voltage target value and the capacitor voltage feedback value into a PI (proportional-integral) regulator, and controlling the on and off of each second power semiconductor device according to the output value of the regulator;
and the device enters a standby mode until the working duration of the device reaches the required energy consumption time or the external fault is eliminated and the voltage of the direct current line is recovered to a normal range.
10. The control method according to claim 9, wherein when more than one of the first power semiconductor devices simultaneously performs on or off, the first power semiconductor devices are sequentially turned on or sequentially turned off.
11. The control method according to claim 7 or 10, wherein,
the sequentially opening includes: sequencing the capacitor voltage of each direct-string module, and sequentially selecting the first power semiconductors corresponding to the N direct-string modules with the highest capacitor voltage to be switched on, wherein N is an integer larger than 1 and smaller than M;
the sequentially turning off comprises: and sequencing the capacitor voltages of the direct-string modules, and sequentially selecting the first power semiconductors corresponding to the N direct-string module capacitors with the lowest capacitor voltages to turn off, wherein N is an integer larger than 1 and smaller than M.
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