CN112152214B - Restarting method and system of distributed power flow controller in two-wire operation mode - Google Patents
Restarting method and system of distributed power flow controller in two-wire operation mode Download PDFInfo
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- CN112152214B CN112152214B CN202011345174.3A CN202011345174A CN112152214B CN 112152214 B CN112152214 B CN 112152214B CN 202011345174 A CN202011345174 A CN 202011345174A CN 112152214 B CN112152214 B CN 112152214B
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Abstract
The invention discloses a method and a system for restarting a distributed power flow controller in a two-wire operation mode. The restarting method of the invention comprises the following steps: restarting a first line or a second line when an alternating current line has an instantaneous fault, restarting the first line or the second line when the alternating current line has a permanent fault, restarting an outer line when the outer line has the instantaneous fault and restarting the outer line when the outer line has the permanent fault, rapidly restarting the DPFC after the alternating current line has the fault, and restoring the line power flow to a value before the fault by adjusting the output voltage of the DPFC. The method can quickly play a role of optimizing the line tide by the DPFC, effectively improve the tide transmission capacity of a local power grid, and improve the operation efficiency and the safety and the stability of the power grid.
Description
Technical Field
The invention belongs to the field of distributed power flow control, and particularly relates to a restarting method and a restarting system of a distributed power flow controller in a double-line operation mode.
Background
With the continuous expansion of high-voltage direct-current transmission and new energy power generation in the scale of power grid access, the problems of tide control and flexible new energy consumption after a large-capacity power supply is hierarchically connected into the power grid are increasingly prominent, the phenomena of large tide fluctuation and unbalanced distribution are serious in the operation process of the power grid, the important and key power supply section limit is low, the bottleneck of power supply capacity restriction of the power grid is formed, and meanwhile, the low operation efficiency of the power grid asset is also caused. At present, the main mode for solving the problems of power supply bottleneck and section overrun is to strengthen power grid construction, and the problems are solved by exploring measures such as a unified power flow controller in partial areas, and the problems are all the problems of long construction period, large investment, large occupied area and the like, so that a novel technical means for improving the power flow transmission capacity of a 220kV system is necessary to be researched, and the operation efficiency and the safety and stability of a power grid are improved.
The DPFC is applied to the power transmission and distribution network, so that the tidal current transmission capacity of a local power grid is effectively improved, and the operation efficiency and the safety and stability of the power grid are improved.
Distributed Power Flow Controllers (DPFCs) are a novel flexible Power Flow control device, can be applied to a Power transmission network, can be installed in a transformer substation in a Distributed mode, and have the functions of optimizing system operation, balancing and optimizing Power Flow distribution, limiting Power Flow section overload, inhibiting Power oscillation and subsynchronous resonance. The distributed power flow controller is connected in series into the power transmission line, and the optimal control of the power flow of the alternating current line is realized by controlling the impedance of a series circuit of the distributed power flow controller.
Because the probability of the instantaneous fault of the alternating-current line is high, in order to ensure that the DPFC can avoid the influence of the fault current on equipment and ensure that the DPFC can quickly play a role of optimizing the line current after the instantaneous fault disappears, an adaptive restart strategy needs to be designed according to different fault positions and types.
At present, scholars at home and abroad have not studied the restarting strategy of the distributed power flow controller, but have developed a certain research on the restarting strategy of the unified power flow controller, the research is mainly focused on the restarting strategy in a single-wire operation mode, and no design guidance is given to the time required by the whole restarting process and the requirements of the restarting process on a bypass switch.
Disclosure of Invention
The technical problem to be solved by the present invention is to overcome the defects in the prior art, and provide a method and a system for restarting a distributed power flow controller in a two-wire operating mode, so as to ensure that a DPFC in the two-wire operating mode can be restarted after an instantaneous fault disappears, adjust the output voltage of the DPFC to restore the line power flow to the value before the fault occurs, and quickly exert the function of optimizing the line power flow of the DPFC.
Therefore, the invention adopts the following technical scheme: a restarting method for a distributed power flow controller in a two-wire operation mode, wherein the two wires are a first wire and a second wire, the first wire is connected with a first DPFC in series, the second wire is connected with a second DPFC in series, and the first wire and the second wire are respectively connected to a first alternating current bus and a second alternating current bus through an alternating current breaker and an isolation disconnecting link, and the restarting method comprises the following steps:
1) restarting of first or second line in the event of an AC line transient fault
When the instantaneous fault of the alternating current circuit occurs to the first circuit or the second circuit, the first circuit and the second circuit simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault circuit are tripped, the alternating current circuit breakers at two ends of the fault circuit are superposed after a period of time, and the overcurrent is recovered due to the instantaneous fault, successful superposition; the two DPFCs detect the overcurrent recovery, restart the two DPFCs and recover the line power flow to the value before the fault by adjusting the output voltage of the DPFCs;
2) restarting of AC line permanent fault on first line or second line
When the first line or the second line has permanent faults of the alternating current line, the first line and the second line simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault line are tripped, the alternating current circuit breakers at two ends of the fault line are coincided after a period of time, and the alternating current circuit breakers are coincided with the fault for permanent tripping due to the permanent faults; the DPFC of the fault line is not started, the DPFC of the non-fault line is successfully restarted, and the power flow of the line is recovered to a value before the fault occurs by adjusting the output voltage of the DPFC;
3) restarting of outside line with instantaneous fault
When the alternating current lines except the first line and the second line have instantaneous faults, if the power capacity near a fault point is large, short-circuit current fed into the fault point and flowing through the DPFC triggers overcurrent protection actions of the first DPFC and the second DPFC, so that the first DPFC and the second DPFC are bypassed, and alternating current circuit breakers on two sides of the external line fault line are tripped; due to instantaneous failure, the alternating current protection of the first line and the second line cannot act, when the failure disappears, the outer line alternating current circuit breaker is successfully superposed, and overcurrent is recovered; the first DPFC and the second DPFC detect the overcurrent recovery, restart the circuit, and recover the circuit power flow to a value before the fault by adjusting the output voltage of the DPFC;
4) restart with permanent fault in outside line
The method comprises the steps that permanent faults occur to alternating current lines except a first line and a second line, overcurrent protection actions of a first DPFC and a second DPFC are triggered, so that the two DPFCs are bypassed, alternating current circuit breakers at two ends of a fault line are tripped out later, alternating current circuit breakers at two ends of the fault line are coincided after a period of time, due to the permanent faults, the alternating current circuit breakers are coincided with the faults to be permanently tripped, overcurrent is recovered, the two DPFCs are restarted, and the line tide is recovered to a value before the faults occur by adjusting the output voltage of the DPFCs.
As a further complement to the above technical solution, the AC breakers at both ends of the fault line are overlapped after 1.0-1.5s of time interval.
As a further supplement to the above technical solution, the external line is restarted due to an instantaneous fault, and if the power supply capacity near the fault point is small, the short-circuit current fed to the fault point and flowing through the DPFC does not trigger the overcurrent protection actions of the first DPFC and the second DPFC.
As a further supplement to the above technical solution, a single sub-module of the DPFC includes an energy-obtaining current transformer, a bypass switch KM, a bidirectional thyristor TBS, and a full-bridge module, wherein the energy-obtaining current transformer is connected in series with the full-bridge module, and the bypass switch KM, the bidirectional thyristor TBS, and the full-bridge module are connected in parallel. The bypass switch KM and the bidirectional conduction thyristor TBS are mainly used for switching in and out of the sub-modules, and play a role in protecting the full-bridge module when a fault occurs.
As a further supplement to the above technical solution, for the sub-module of the DPFC, when a fault occurs, the control protection system of the DPFC simultaneously issues commands of locking the converter valve of the faulty sub-module, closing the bidirectional conducting thyristor TBS, and closing the bypass switch KM, the converter valve is firstly locked, then the bidirectional conducting thyristor TBS is conducted, then the bypass switch KM is closed, and finally the bidirectional conducting thyristor TBS is turned off; after the fault disappears, the DPFC is restarted, the bypass switch KM is divided, the converter valve is unlocked, if the bypass switch KM is divided, the alternating current circuit breaks down immediately, and the bypass switch KM needs to have the capability of being closed immediately in order to protect the converter valve from being damaged.
Furthermore, the DPFC restart has a fast "close-open-close" requirement on the bypass switch KM, and the specific time sequence of the "close-open-close" requirement is as follows:
1) time t 1: when the AC line fault occurs, switching on a bypass switch KM;
2) time t 2: in order to avoid reclosing of the alternating current circuit, the bypass switch KM is opened after being closed for 1.5s, and the DPFC starts to restart;
3) time t 3: if the line has a fault after the bypass switch KM is separated, the bypass switch KM and the bidirectional conducting thyristor BPS are combined and are not restarted.
Furthermore, the DPFC is not put into operation within the time period from t1 to t2, and the DPFC cannot play a role if line overload occurs at the time; since overload is not allowed for the cable line and only short-circuit current tolerance of 5s is specified, 5s is used as a tolerance time for allowing the cable to be disconnected from the DPFC operation.
Still further, t2-t1 needs to be controlled within 1.5s-5s, namely, within 1.5s-5s after the bypass switch KM is closed when the DPFC is restarted, the DPFC needs to recover the operation and control the power flow to the previous level, and the bypass switch KM needs to have the capability of closing-opening-closing within 1.5s-5 s.
The other technical scheme adopted by the invention is as follows: a restart system of a distributed power flow controller in a two-wire operation mode, wherein the two wires are a first wire and a second wire, the first wire is connected with a first DPFC in series, the second wire is connected with a second DPFC in series, and the first wire and the second wire are respectively connected to a first alternating current bus and a second alternating current bus through an alternating current breaker and an isolation disconnecting link, the restart system comprises:
1) restarting module for instantaneous fault of alternating current line of first line or second line
When the instantaneous fault of the alternating current circuit occurs to the first circuit or the second circuit, the first circuit and the second circuit simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault circuit are tripped, the alternating current circuit breakers at two ends of the fault circuit are superposed after a period of time, and the overcurrent is recovered due to the instantaneous fault, successful superposition; the two DPFCs detect the overcurrent recovery, restart the two DPFCs and recover the line power flow to the value before the fault by adjusting the output voltage of the DPFCs;
2) restarting module for permanent fault of alternating current line of first line or second line
When the first line or the second line has permanent faults of the alternating current line, the first line and the second line simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault line are tripped, the alternating current circuit breakers at two ends of the fault line are coincided after a period of time, and the alternating current circuit breakers are coincided with the fault for permanent tripping due to the permanent faults; the DPFC of the fault line is not started, the DPFC of the non-fault line is successfully restarted, and the power flow of the line is recovered to a value before the fault occurs by adjusting the output voltage of the DPFC;
3) restarting module for instantaneous fault of outside line
When the alternating current lines except the first line and the second line have instantaneous faults, if the power capacity near a fault point is large, short-circuit current fed into the fault point and flowing through the DPFC triggers overcurrent protection actions of the first DPFC and the second DPFC, so that the first DPFC and the second DPFC are bypassed, and alternating current circuit breakers on two sides of the external line fault line are tripped; due to instantaneous failure, the alternating current protection of the first line and the second line cannot act, when the failure disappears, the outer line alternating current circuit breaker is successfully superposed, and overcurrent is recovered; the first DPFC and the second DPFC detect the overcurrent recovery, restart the circuit, and recover the circuit power flow to a value before the fault by adjusting the output voltage of the DPFC;
4) restarting module for permanent fault of exterior line
The method comprises the steps that permanent faults occur to alternating current lines except a first line and a second line, overcurrent protection actions of a first DPFC and a second DPFC are triggered, so that the two DPFCs are bypassed, alternating current circuit breakers at two ends of a fault line are tripped out later, alternating current circuit breakers at two ends of the fault line are coincided after a period of time, due to the permanent faults, the alternating current circuit breakers are coincided with the faults to be permanently tripped, overcurrent is recovered, the two DPFCs are restarted, and the line tide is recovered to a value before the faults occur by adjusting the output voltage of the DPFCs.
The invention has the following beneficial effects: the invention can ensure that the DPFC in the double-line operation mode can be restarted after the transient fault disappears, adjust the output voltage of the DPFC to restore the line power flow to the value before the fault occurs, and quickly play the role of optimizing the line power flow of the DPFC. The invention can effectively improve the tidal current transmission capacity of the local power grid and improve the operation efficiency and the safety and the stability of the power grid.
Drawings
Fig. 1 is a primary wiring diagram of a distributed power flow controller in a two-wire operation mode according to the present invention.
Detailed Description
The technical scheme of the invention is more clearly and completely described below by combining the embodiment and the attached drawings of the specification.
Fig. 1 is a primary wiring diagram of a two-wire DPFC, which includes multiple stages of sub-modules and a common switch area, wherein a first line is connected in series with a first DPFC, a second line is connected in series with a second DPFC, and the first line and the second line are connected to a first ac bus and a second ac bus through an ac circuit breaker and an isolation switch, respectively. The single sub-module of the DPFC comprises an energy-obtaining current transformer, a bypass switch KM, a bidirectional conduction thyristor TBS and a full-bridge module, wherein the energy-obtaining current transformer is connected with the full-bridge module in series, and the bypass switch KM, the bidirectional conduction thyristor TBS and the full-bridge module are connected in parallel. The bypass switch KM and the bidirectional conduction thyristor TBS are mainly used for switching in and out of the sub-modules, and play a role in protecting the full-bridge module when a fault occurs.
In fig. 1, Ubus1 and 2 are PTs of the first bus and the second bus of the left-side substation, and TV1 and TV2 are PTs of the first bus and the second bus of the right-side substation.
W1.ds41, w1.ds42, w1.qf1 are ac breakers and disconnectors with first lines connected to the left side substation bus.
W2.ds41, w2.ds42, w2.qf1 are ac breakers and disconnecting switches with second lines connected to the left side substation bus.
W1.DS1, W1.DS2, W1.DS3, W1.QF, W1.DS21 and W1.DS31 are public area switches and switches of the first DPFC, and for application scenes with long sub-module distribution distances, the switch switches can be omitted.
W2.DS1, W2.DS2, W2.DS3, W2.QF, W2.DS21 and W2.DS31 are common area switches and switches of the second DPFC, and for application scenes with long sub-module distribution distances, the switch switches can be omitted.
MOV is arrester, BPS is bidirectional conduction thyristor.
KM1 and KM2 are bypass switches of the submodules.
C1# -C9# indicates the capacitance number corresponding to 9 sub-modules.
Example 1
Taking a two-wire DPFC operation as an example, a first line corresponds to a first DPFC, a second line corresponds to a second DPFC, and a quick restart method of the DPFC in a two-wire operation mode is introduced below according to different fault types (transient fault, permanent fault) and different fault positions (first line, second line, and external line).
(1) Restarting of first or second line in the event of an AC line transient fault
The first line or the second line has an instantaneous fault of the AC line, the first line and the second line simultaneously overflow to trigger the overcurrent protection actions of the first DPFC and the second DPFC, so that the two DPFCs are bypassed, then the AC circuit breakers at the two ends of the fault line are tripped, the AC circuit breakers at the two ends of the fault line are coincided after 1.5s, and due to the instantaneous fault, the coincidence is successful and the overcurrent is recovered. And the two DPFCs detect the overcurrent recovery, restart the two DPFCs and restore the line power flow to the value before the fault by regulating the output voltage of the DPFCs.
(2) Restarting of AC line permanent fault on first line or second line
When the first line or the second line has a permanent fault of the alternating current line, the first line and the second line simultaneously overflow, and overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then the alternating current circuit breakers at two ends of the fault line are tripped, the alternating current circuit breakers at two ends of the fault line are coincided after 1.5s, and due to the permanent fault, the alternating current circuit breakers are coincided with the fault for permanent tripping. And the DPFC of the fault line is not started, the DPFC of the non-fault line is successfully restarted, and the power flow of the line is recovered to the value before the fault occurs by adjusting the output voltage of the DPFC.
(3) Restarting of outside line with instantaneous fault
Instantaneous faults occur in the alternating current lines except the first line and the second line, if the power supply capacity near a fault point is large, the short-circuit current fed into the fault point and flowing through the DPFC is large, overcurrent protection actions of the first DPFC and the second DPFC are triggered, the two DPFCs are bypassed, and alternating current circuit breakers on two sides of the external line fault line are tripped; due to instantaneous failure, the alternating current protection of the first line and the second line cannot act, when the failure disappears, the outer line alternating current circuit breaker is successfully superposed, and overcurrent is recovered; the first DPFC and the second DPFC detect the overcurrent recovery, restart the circuit, and recover the circuit power flow to a value before the fault by adjusting the output voltage of the DPFC;
if the power supply capacity near the fault point is small, the short-circuit current fed into the fault point and flowing through the DPFC is small, and the overcurrent protection actions of the first DPFC and the second DPFC cannot be triggered.
(4) Restart with permanent fault in outside line
The method comprises the steps that permanent faults occur to alternating current lines except a first line and a second line, overcurrent protection actions of the first DPFC and the second DPFC are triggered, the two DPFCs are bypassed, alternating current circuit breakers at two ends of a fault line are tripped, the alternating current circuit breakers at two ends of the line are coincided corresponding to the fault point after 1.5s, due to the permanent faults, the alternating current circuit breakers are coincided with the faults to be permanently tripped, overcurrent recovery is conducted, the two DPFCs are restarted, and the power flow of the line is recovered to the value before the faults occur by adjusting the output voltage of the DPFCs.
For the sub-module, when a fault occurs, the control protection system simultaneously issues commands of locking a fault sub-module converter valve, switching on the bidirectional conducting thyristor TBS and switching on the bypass switch KM, the converter valve is firstly locked, then the bidirectional conducting thyristor TBS is conducted, then the bypass switch KM is switched on, and finally the bidirectional conducting thyristor TBS is switched off. And after the fault disappears, the DPFC is restarted, the bypass switch KM is switched off, and the converter valve is unlocked. If the bypass switch KM is separated, the alternating current circuit breaks down immediately, and the bypass switch KM needs to have the capability of being closed immediately in order to protect the converter valve from being damaged. Therefore, when the DPFC is restarted, the bypass switch KM has a fast "close-open-close" requirement, and the specific time sequence is as follows:
1) time t 1: when the AC line fault occurs, switching on a bypass switch KM;
2) time t 2: in order to avoid reclosing of the alternating current circuit, the bypass switch KM is opened after being closed for 1.5s, and the DPFC starts to restart;
3) time t 3: if the line has a fault after the bypass switch KM is separated, the bypass switch KM and the bidirectional conducting thyristor BPS are combined and are not restarted.
And the DPFC is not put into operation in the time period from t1 to t2, and the DPFC cannot function if the line overload occurs at the time. For cable lines not allowing overload, there is a relevant provision only for short circuit current withstand 5s, so 5s is taken as the withstand time for the cable to be allowed to leave the DPFC operation. Therefore, t2-t1 needs to be controlled within 1.5s-5s, namely within 1.5s-5s after the bypass switch KM is closed when the DPFC is restarted, the DPFC needs to be recovered to operate and control the power flow to the previous level. This requires the bypass switch KM to have the ability of "on-off-on" within 1.5s-5 s.
Example 2
Taking an example of the operation of the dual-line DPFC, the first line corresponds to the first DPFC, the second line corresponds to the second DPFC, and a quick restart system of the DPFC in the dual-line operation mode is introduced below according to the difference of fault types (transient fault, permanent fault) and the difference of fault positions (first line, second line, and external line).
(1) Restarting module for instantaneous fault of alternating current line of first line or second line
The first line or the second line has an instantaneous fault of the AC line, the first line and the second line simultaneously overflow to trigger the overcurrent protection actions of the first DPFC and the second DPFC, so that the two DPFCs are bypassed, then the AC circuit breakers at the two ends of the fault line are tripped, the AC circuit breakers at the two ends of the fault line are coincided after 1.5s, and due to the instantaneous fault, the coincidence is successful and the overcurrent is recovered. And the two DPFCs detect the overcurrent recovery, restart the two DPFCs and restore the line power flow to the value before the fault by regulating the output voltage of the DPFCs.
(2) Restarting module for permanent fault of alternating current line of first line or second line
When the first line or the second line has a permanent fault of the alternating current line, the first line and the second line simultaneously overflow, and overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then the alternating current circuit breakers at two ends of the fault line are tripped, the alternating current circuit breakers at two ends of the fault line are coincided after 1.5s, and due to the permanent fault, the alternating current circuit breakers are coincided with the fault for permanent tripping. And the DPFC of the fault line is not started, the DPFC of the non-fault line is successfully restarted, and the power flow of the line is recovered to the value before the fault occurs by adjusting the output voltage of the DPFC.
(3) Restarting module for instantaneous fault of outside line
Instantaneous faults occur in the alternating current lines except the first line and the second line, if the power supply capacity near a fault point is large, the short-circuit current fed into the fault point and flowing through the DPFC is large, overcurrent protection actions of the first DPFC and the second DPFC are triggered, the two DPFCs are bypassed, and alternating current circuit breakers on two sides of the external line fault line are tripped; due to instantaneous failure, the alternating current protection of the first line and the second line cannot act, when the failure disappears, the outer line alternating current circuit breaker is successfully superposed, and overcurrent is recovered; the first DPFC and the second DPFC detect the overcurrent recovery, restart the circuit, and recover the circuit power flow to a value before the fault by adjusting the output voltage of the DPFC;
if the power supply capacity near the fault point is small, the short-circuit current fed into the fault point and flowing through the DPFC is small, and the overcurrent protection actions of the first DPFC and the second DPFC cannot be triggered.
(4) Restarting module for permanent fault of exterior line
The method comprises the steps that permanent faults occur to alternating current lines except a first line and a second line, overcurrent protection actions of the first DPFC and the second DPFC are triggered, the two DPFCs are bypassed, alternating current circuit breakers at two ends of a fault line are tripped, the alternating current circuit breakers at two ends of the line are coincided corresponding to the fault point after 1.5s, due to the permanent faults, the alternating current circuit breakers are coincided with the faults to be permanently tripped, overcurrent recovery is conducted, the two DPFCs are restarted, and the power flow of the line is recovered to the value before the faults occur by adjusting the output voltage of the DPFCs.
For the sub-module, when a fault occurs, the control protection system simultaneously issues commands of locking a fault sub-module converter valve, switching on the bidirectional conducting thyristor TBS and switching on the bypass switch KM, the converter valve is firstly locked, then the bidirectional conducting thyristor TBS is conducted, then the bypass switch KM is switched on, and finally the bidirectional conducting thyristor TBS is switched off. And after the fault disappears, the DPFC is restarted, the bypass switch KM is switched off, and the converter valve is unlocked. If the bypass switch KM is separated, the alternating current circuit breaks down immediately, and the bypass switch KM needs to have the capability of being closed immediately in order to protect the converter valve from being damaged. Therefore, when the DPFC is restarted, the bypass switch KM has a fast "close-open-close" requirement, and the specific time sequence is as follows:
1) time t 1: when the AC line fault occurs, switching on a bypass switch KM;
2) time t 2: in order to avoid reclosing of the alternating current circuit, the bypass switch KM is opened after being closed for 1.5s, and the DPFC starts to restart;
3) time t 3: if the line has a fault after the bypass switch KM is separated, the bypass switch KM and the bidirectional conducting thyristor BPS are combined and are not restarted.
And the DPFC is not put into operation in the time period from t1 to t2, and the DPFC cannot function if the line overload occurs at the time. For cable lines not allowing overload, there is a relevant provision only for short circuit current withstand 5s, so 5s is taken as the withstand time for the cable to be allowed to leave the DPFC operation. Therefore, t2-t1 needs to be controlled within 1.5s-5s, namely within 1.5s-5s after the bypass switch KM is closed when the DPFC is restarted, the DPFC needs to be recovered to operate and control the power flow to the previous level. This requires the bypass switch KM to have the ability of "on-off-on" within 1.5s-5 s.
The above embodiments are merely preferred embodiments of the present invention. Any simple modification, equivalent change and modification of the above embodiments according to the technical spirit of the present invention fall within the scope of the present invention.
Claims (8)
1. A restarting method of a distributed power flow controller in a two-wire operation mode, wherein the two wires are a first wire and a second wire, the first wire is connected with a first DPFC in series, the second wire is connected with a second DPFC in series, and the first wire and the second wire are respectively connected to a first alternating current bus and a second alternating current bus through an alternating current breaker and an isolation disconnecting link, and the restarting method comprises the following steps:
1) restarting of first or second line in the event of an AC line transient fault
When the instantaneous fault of the alternating current circuit occurs to the first circuit or the second circuit, the first circuit and the second circuit simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault circuit are tripped, the alternating current circuit breakers at two ends of the fault circuit are superposed after a period of time, and the overcurrent is recovered due to the instantaneous fault, successful superposition; the two DPFCs detect the overcurrent recovery, restart the two DPFCs and recover the line power flow to the value before the fault by adjusting the output voltage of the DPFCs;
2) restarting of AC line permanent fault on first line or second line
When the first line or the second line has permanent faults of the alternating current line, the first line and the second line simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault line are tripped, the alternating current circuit breakers at two ends of the fault line are coincided after a period of time, and the alternating current circuit breakers are coincided with the fault for permanent tripping due to the permanent faults; the DPFC of the fault line is not started, the DPFC of the non-fault line is successfully restarted, and the power flow of the line is recovered to a value before the fault occurs by adjusting the output voltage of the DPFC;
3) restarting of outside line with instantaneous fault
When the alternating current lines except the first line and the second line have instantaneous faults, if the power capacity near a fault point is large, short-circuit current fed into the fault point and flowing through the DPFC triggers overcurrent protection actions of the first DPFC and the second DPFC, so that the first DPFC and the second DPFC are bypassed, and alternating current circuit breakers on two sides of the external line fault line are tripped; due to instantaneous failure, the alternating current protection of the first line and the second line cannot act, when the failure disappears, the outer line alternating current circuit breaker is successfully superposed, and overcurrent is recovered; the first DPFC and the second DPFC detect the overcurrent recovery, restart the circuit, and recover the circuit power flow to a value before the fault by adjusting the output voltage of the DPFC;
restarting the exterior line when instantaneous fault occurs, if the power supply capacity near the fault point is small, short-circuit current fed into the fault point and flowing through the DPFC does not trigger overcurrent protection actions of the first DPFC and the second DPFC, under the condition, firstly adjusting the output voltage of the DPFC for a short time, and gradually recovering the line power flow to the value before the fault occurs after the reclosing time of the alternating-current circuit breaker is avoided;
4) restart with permanent fault in outside line
The method comprises the steps that permanent faults occur to alternating current lines except a first line and a second line, overcurrent protection actions of a first DPFC and a second DPFC are triggered, so that the two DPFCs are bypassed, alternating current circuit breakers at two ends of a fault line are tripped out later, alternating current circuit breakers at two ends of the fault line are coincided after a period of time, due to the permanent faults, the alternating current circuit breakers are coincided with the faults to be permanently tripped, overcurrent is recovered, the two DPFCs are restarted, and the line tide is recovered to a value before the faults occur by adjusting the output voltage of the DPFCs.
2. The method for restarting the distributed power flow controller in the two-wire operation mode according to claim 1, wherein the ac breakers at both ends of the fault line are coincided after 1.0-1.5s of time interval.
3. The method as claimed in any one of claims 1 to 2, wherein the individual sub-modules of the DPFC comprise an energy-taking current transformer, a bypass switch KM, a bidirectional thyristor TBS, and a full-bridge module, the energy-taking current transformer is connected in series with the full-bridge module, and the bypass switch KM, the bidirectional thyristor TBS, and the full-bridge module are connected in parallel.
4. The method for restarting the distributed power flow controller in the two-wire operation mode according to claim 3, wherein for the sub-module of the DPFC, when a fault occurs, a control protection system of the DPFC simultaneously issues commands of locking a fault sub-module converter valve, switching on the bidirectional conducting thyristor TBS and switching on the bypass switch KM, wherein the converter valve is firstly locked, then the bidirectional conducting thyristor TBS is switched on, then the bypass switch KM is switched on, and finally the bidirectional conducting thyristor TBS is switched off; after the fault disappears, the DPFC is restarted, the bypass switch KM is divided, the converter valve is unlocked, if the bypass switch KM is divided, the alternating current circuit breaks down immediately, and the bypass switch KM needs to have the capability of being closed immediately in order to protect the converter valve from being damaged.
5. The method for restarting the distributed power flow controller in the two-wire operation mode according to claim 4, wherein the bypass switch KM has a fast on-off-on demand when the DPFC is restarted, and the specific timing sequence of the on-off-on demand is as follows:
1) time t 1: when the AC line fault occurs, switching on a bypass switch KM;
2) time t 2: in order to avoid reclosing of the alternating current circuit, the bypass switch KM is opened after being closed for 1.5s, and the DPFC starts to restart;
3) time t 3: if the line has a fault after the bypass switch KM is separated, the bypass switch KM and the bidirectional conducting thyristor BPS are combined and are not restarted.
6. The method for restarting the distributed power flow controller in the two-wire operation mode according to claim 5, wherein the DPFC is not put into operation during a time period from t1 to t2, and the DPFC cannot function if the line is overloaded; since overload is not allowed for the cable line and only short-circuit current tolerance of 5s is specified, 5s is used as a tolerance time for allowing the cable to be disconnected from the DPFC operation.
7. The method of claim 6, wherein t2-t1 is controlled to 1.5s-5s, that is, within 1.5s-5s after the bypass switch KM is turned on when the DPFC is restarted, the DPFC needs to resume operation and control the power flow to the previous level, and the bypass switch KM needs to have an on-off-on capability within 1.5s-5 s.
8. A restart system of a distributed power flow controller in a two-wire operation mode, wherein the two wires are a first wire and a second wire, the first wire is connected with a first DPFC in series, the second wire is connected with a second DPFC in series, and the first wire and the second wire are respectively connected to a first alternating current bus and a second alternating current bus through an alternating current breaker and an isolation disconnecting link, the restart system is characterized by comprising:
1) restarting module for instantaneous fault of alternating current line of first line or second line
When the instantaneous fault of the alternating current circuit occurs to the first circuit or the second circuit, the first circuit and the second circuit simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault circuit are tripped, the alternating current circuit breakers at two ends of the fault circuit are superposed after a period of time, and the overcurrent is recovered due to the instantaneous fault, successful superposition; the two DPFCs detect the overcurrent recovery, restart the two DPFCs and recover the line power flow to the value before the fault by adjusting the output voltage of the DPFCs;
2) restarting module for permanent fault of alternating current line of first line or second line
When the first line or the second line has permanent faults of the alternating current line, the first line and the second line simultaneously overflow, overcurrent protection actions of the first DPFC and the second DPFC are triggered, so that the two DPFCs are bypassed, then alternating current circuit breakers at two ends of the fault line are tripped, the alternating current circuit breakers at two ends of the fault line are coincided after a period of time, and the alternating current circuit breakers are coincided with the fault for permanent tripping due to the permanent faults; the DPFC of the fault line is not started, the DPFC of the non-fault line is successfully restarted, and the power flow of the line is recovered to a value before the fault occurs by adjusting the output voltage of the DPFC;
3) restarting module for instantaneous fault of outside line
When the alternating current lines except the first line and the second line have instantaneous faults, if the power capacity near a fault point is large, short-circuit current fed into the fault point and flowing through the DPFC triggers overcurrent protection actions of the first DPFC and the second DPFC, so that the first DPFC and the second DPFC are bypassed, and alternating current circuit breakers on two sides of the external line fault line are tripped; due to instantaneous failure, the alternating current protection of the first line and the second line cannot act, when the failure disappears, the outer line alternating current circuit breaker is successfully superposed, and overcurrent is recovered; the first DPFC and the second DPFC detect the overcurrent recovery, restart the circuit, and recover the circuit power flow to a value before the fault by adjusting the output voltage of the DPFC;
if the power supply capacity near the fault point is small, short-circuit current fed into the fault point and flowing through the DPFC does not trigger overcurrent protection actions of the first DPFC and the second DPFC, under the condition, the output voltage of the DPFC is firstly adjusted in a short time, and the line power flow is gradually restored to the value before the fault occurs after the reclosing time of the alternating-current circuit breaker is avoided;
4) restarting module for permanent fault of exterior line
The method comprises the steps that permanent faults occur to alternating current lines except a first line and a second line, overcurrent protection actions of a first DPFC and a second DPFC are triggered, so that the two DPFCs are bypassed, alternating current circuit breakers at two ends of a fault line are tripped out later, alternating current circuit breakers at two ends of the fault line are coincided after a period of time, due to the permanent faults, the alternating current circuit breakers are coincided with the faults to be permanently tripped, overcurrent is recovered, the two DPFCs are restarted, and the line tide is recovered to a value before the faults occur by adjusting the output voltage of the DPFCs.
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| CN113964817A (en) * | 2021-09-18 | 2022-01-21 | 国网浙江省电力有限公司电力科学研究院 | Control method and system of distributed power flow controller under operating condition of double-wire to single-wire operation |
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