CN110299704B - Grid-connected intelligent fault processing device and method for power distribution network - Google Patents
Grid-connected intelligent fault processing device and method for power distribution network Download PDFInfo
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Abstract
The invention provides a device and a method for processing intelligent faults of a grid-connected power distribution network, wherein the device comprises the following steps: the system comprises a single-phase transformer, a reactor, an independent IGBT bridge arm, an overcurrent protector, an overvoltage protector, a super capacitor bank and a grounding circuit; the method comprises the following steps: the frequency, amplitude and phase of the voltage of the power grid are automatically tracked to realize flexible non-impact grid connection; injecting compensation harmonic current to counteract system harmonic current according to the harmonic frequency and the content of the power grid; confirming the single-phase earth fault according to the set criterion of the single-phase earth fault, and injecting the compensating power grid grounding capacitance current into the grounding loop; setting an automatic splitting program to realize safe parking according to the grid fault characteristic quantity and the over-current and over-voltage limit values of the IGBT of the device; the direct current source stabilization of the grounding capacitive current compensation is realized through the super capacitor bank; and mode smooth control of compensating harmonic current and power grid grounding capacitance current is realized through current feedforward. The invention can realize the filtering function for improving the quality of the power grid and the protection function for single-phase earth faults.
Description
Technical Field
The invention relates to the technical field of power grid fault processing, in particular to a device and a method for processing grid-connected intelligent faults of a power distribution network.
Background
The existing medium-voltage distribution network widely adopts a mode of passing through an arc suppression coil, and belongs to a resonance grounding network. Due to the loop formed by the distributed capacitance of the transmission line to the ground in the network, the current of a fault point is generally very small, and the network is allowed to operate for 1-2 hours under the condition of single-phase ground fault. However, if the fault is not effectively processed within the time, the insulation damage of the transmission line is often caused, and a severe accident is caused. With the development of power electronic technology and the wide adoption of power electronic equipment in power systems, a method for realizing compensation by using a flexible grounding technology has received certain attention. The prior art mainly comprises various arc suppression coil technologies, power electronic device compensation technologies, single-phase grounding protection combination technologies and the like, research is focused on the single-phase fault moment of a power grid, and even in the occasions where multifunctional application is mentioned, equipment self-protection technology, grid connection and disconnection technology are not specifically mentioned. In addition, the conventional direct current side bus capacitor has the problem of insufficient impact resistance.
Power electronic devices widely used in various new energy equipment and loads have become a major source of grid harmonics. When a large number of switching devices work, high-frequency on-off current conversion is carried out, and larger harmonic waves are generated, so that on one hand, the large harmonic waves bring great harm to the safe and economic operation of a power grid, equipment loss can be increased, the use efficiency of the equipment is reduced, the comprehensive energy consumption is increased, and the national industrial development requirements are not met; on the other hand, the electromagnetic interference is serious, and the normal application of key equipment is influenced. In addition, since power electronic equipment is developing towards intellectualization, it is an important development direction to research multifunctional and time-sharing equipment.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a device and a method for processing the intelligent fault of a grid-connected power distribution network.
The invention provides the following technical scheme:
in a first aspect, the present invention provides a grid-connected intelligent fault handling device for a power distribution network, including: the system comprises four single-phase transformers, four reactors, four independent IGBT bridge arms, an overcurrent protector, an overvoltage protector, a super capacitor bank and a grounding circuit;
one end of a single-phase transformer 1 is connected with A, and the other end of the single-phase transformer is connected with a first end of a reactor 1; one end of the single-phase transformer 2 is connected with the B, and the other end of the single-phase transformer is connected with the first end of the reactor 2; one end of the single-phase transformer 3 is connected with the C, and the other end of the single-phase transformer 3 is connected with the first end of the reactor 3; one end of the single-phase transformer 4 is connected with a zero line, and the other end of the single-phase transformer 4 is connected with a first end of the reactor 4; one end of the zero line is connected with a grounding circuit;
the second end of the reactor 1 is connected with the IGBT bridge arm 1; the second end of the reactor 2 is connected with the IGBT bridge arm 2; the second end of the reactor 3 is connected with the IGBT bridge arm 3; the second end of the reactor 4 is connected with the IGBT bridge arm 4;
the overcurrent protector is connected between the zero line and the IGBT bridge arm 4; the overvoltage protector and the super capacitor bank are respectively connected between a positive bus and a negative bus of the device, and the super capacitor bank is used as a voltage stabilizing and energy converting unit at a direct current side.
Furthermore, an overvoltage protector on the direct current side in the device adopts a mode that an IGBT is connected with a bleeder resistor in series, so that the voltage of the overvoltage bus is quickly stabilized.
Further, the control process of the device is realized by a DSP control system, and comprises the following steps: the device comprises a data acquisition unit, an IGBT driving unit, a protection parameter setting unit and a data storage and uploading unit.
In a second aspect, the present invention further provides a grid-connected intelligent fault handling method based on the grid-connected intelligent fault handling apparatus of the first aspect, including:
step S1: the signal acquisition device automatically tracks the frequency, amplitude and phase of the voltage of the power grid to realize flexible non-impact grid connection;
step S2: injecting compensation harmonic current according to the harmonic frequency and the content of the power grid so as to offset the harmonic current of the system;
step S3: confirming the single-phase earth fault according to the set criterion of the single-phase earth fault, and injecting the compensating power grid grounding capacitance current into the grounding loop;
step S4: according to the grid fault characteristic quantity and the over-current and over-voltage limit values of the IGBT of the device, an automatic splitting program is set to realize safe parking, so that the accident expansion is avoided; the grid fault characteristic quantity comprises frequency, amplitude and phase;
step S5: the direct current source stabilization of the grounding capacitive current compensation is realized through a super capacitor bank in the device;
step S6: and mode smooth control of compensating harmonic current and power grid grounding capacitance current is realized through current feedforward.
Furthermore, the flexible impact-free grid connection is realized through a phase-locked loop PLL (phase-locked loop) based on a power grid voltage orientation vector control VOC technology.
Further, the system harmonic current detection is based on ip-iqThe method is obtained by transforming a matrix as follows:
in the formula ia、ib、icRespectively, the three-phase current detected by the device; i.e. ip、iqActive and reactive currents, respectively.
Further, the set criterion of the single-phase earth fault is as follows:
zero sequence voltage U0Greater than a set value U0ref(ii) a The reduction rate of any phase voltage is smaller than a set value, and the increase rates of the other two phase voltages are larger than the set value; meanwhile, a current criterion is added, and the grounding capacitance current is less than or equal to a set IcREF；
In the formula, Δ Ua＝Ua-Urm，ΔUb＝Ub-Urm，ΔUc＝Uc-Urm；U0Is zero sequence voltage, U0refIs the zero sequence voltage reference value, Δ Ua、ΔUb、ΔUcRespectively, the rate of change of voltage, ICIs a measurement of the earth current, ICREFIs a reference value of the ground current, UminrefIs the voltage minimum reference value, UmaxrefIs the reference value of the maximum voltage, UrmIt is the voltage amplitude, x ↓ and ↓ represent the voltage drop and rise, respectively.
Further, the capacitive grounding current of the power grid is measured on line and confirmed in an off-line measurement mode, and when the grounding current is measured, the grounding current is measured to be ICAfter the current is larger than the set upper current limit of the device, the device directly enters a splitting procedure toA protection device;
Ic＝3ωCUrm
where ω is the grid angular frequency, C is the grounding capacitance, UrmIs the voltage amplitude.
Further, the automatic disconnection procedure includes: voltage and current state detection, state word uploading, fault word uploading and shutdown instruction issuing.
Further, the automatic splitting program specifically includes:
step S41: grid-connected operation;
step S42: detecting voltage and current faults and uploading the marks;
step S43: judging whether the fault word is valid or not in a circulating manner, if so, executing S44, and otherwise, continuing to execute the step S43;
step S44: uploading a fault word, issuing a shutdown instruction, resetting a state word at the same time, and executing the step S46;
step S45: when the compensation grounding capacitive current is larger than the upper limit of the current set by the device, the device directly enters into the splitting parking and executes the highest priority;
step S46: and (5) separating and parking.
According to the technical scheme, the grid-connected intelligent fault processing device and method for the power distribution network can achieve a filtering function for improving the quality of the power grid and a protection function for single-phase earth faults, meanwhile, by designing grid connection and disconnection programs and using the super capacitor bank as a voltage stabilization and transduction unit on a direct current side, the safety of equipment and a system is improved, the power grid accidents caused by the self-problem of the equipment are prevented from being further expanded, the self-protection, grid connection and disconnection technology of the equipment is related, and the grid-connected intelligent fault processing device and method for the power distribution network are an advanced technology of power electronic equipment with complex functions in the application of a power system.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a grid-connected intelligent fault handling device for a power distribution network according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for processing an intelligent fault of a grid-connected power distribution network according to another embodiment of the present invention;
FIG. 3 is a flow chart of a de-queuing procedure;
FIG. 4 is a block diagram of current feed forward control;
the meaning of the reference symbols in figure 1 above is explained as follows:
1 denotes a single-phase transformer 1; 2 denotes a single-phase transformer 2; 3 denotes a single-phase transformer 3; 4 denotes a single-phase transformer 4; 5 denotes a reactor 1; 6 denotes a reactor 2; 7 denotes a reactor 3; 8 denotes a reactor 4; 9 denotes an IGBT leg 1; 10 denotes an IGBT leg 2; 11 denotes an IGBT arm 3; 12 denotes an IGBT leg 4; 13 denotes an overcurrent protector; 14 denotes an overvoltage protector; 15 denotes a supercapacitor bank; and 16 denotes a ground line.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. 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 invention.
The grid-connected intelligent fault processing device and method for the power distribution network are applied to a medium-voltage power distribution network of 6-35kV, are used for improving the power quality of the power grid and rapidly processing single-phase earth faults, can intelligently recognize the operation working condition of the power grid, further achieve the dual purposes of improving the power quality and processing faults, relate to self-protection, grid connection and disconnection technologies of the equipment, and are an advanced technology of power electronic equipment with complex functions in the application of a power system.
Specifically, an embodiment of the present invention provides a grid-connected intelligent fault handling device for a power distribution network, and referring to fig. 1, the device includes: the system comprises four single-phase transformers, four reactors, four independent IGBT bridge arms, an overcurrent protector, an overvoltage protector, a super capacitor bank and a grounding circuit;
one end of a single-phase transformer 1 is connected with A, and the other end of the single-phase transformer is connected with a first end of a reactor 1; one end of the single-phase transformer 2 is connected with the B, and the other end of the single-phase transformer is connected with the first end of the reactor 2; one end of the single-phase transformer 3 is connected with the C, and the other end of the single-phase transformer 3 is connected with the first end of the reactor 3; one end of the single-phase transformer 4 is connected with a zero line, and the other end of the single-phase transformer 4 is connected with a first end of the reactor 4; one end of the zero line is connected with a grounding circuit;
the second end of the reactor 1 is connected with the IGBT bridge arm 1; the second end of the reactor 2 is connected with the IGBT bridge arm 2; the second end of the reactor 3 is connected with the IGBT bridge arm 3; the second end of the reactor 4 is connected with the IGBT bridge arm 4;
the overcurrent protector is connected between the zero line and the IGBT bridge arm 4; the overvoltage protector and the super capacitor bank are respectively connected between a positive bus and a negative bus of the device, and the super capacitor bank is used as a voltage stabilizing and energy converting unit at a direct current side.
In a preferred embodiment, an overvoltage protector on a direct current side in the device adopts a mode of connecting an IGBT in series with a bleeder resistor, so that the voltage of a bus is quickly stabilized after overvoltage.
It can be understood that the direct current side of the device selects the super capacitor as the voltage stabilizing and energy converting unit, so that the reliability can be further improved. The direct current side 14 adopts a mode that an IGBT is connected with a bleeder resistor in series, so that the voltage of the bus can be quickly stabilized after overvoltage.
It should be understood that the grounding circuit 16 in fig. 1 may be any grounding method such as arc suppression coil, resistance grounding, etc., and the present invention is not limited thereto.
In a preferred embodiment, the control process of the device is realized by a DSP control system, which comprises: the device comprises a data acquisition unit, an IGBT driving unit, a protection parameter setting unit and a data storage and uploading unit.
Another embodiment of the present invention provides a method for processing a grid-connected intelligent fault of a power distribution network based on the grid-connected intelligent fault processing apparatus of the power distribution network according to the above embodiment, and referring to fig. 2, the method includes the following steps:
step 101: the signal acquisition device automatically tracks the frequency, amplitude and phase of the voltage of the power grid to realize flexible non-impact grid connection.
In this step, the voltage frequency f of the power grid is automatically tracked by a signal acquisition devicemAmplitude UmAnd phase
Flexible impact-free grid connection is realized; wherein f ismThe rate of change is between +/-5%; u shapemThe rate of change is between +/-10%;
the rate of change was between ± 3%.
Step 102: and injecting compensation harmonic current according to the harmonic frequency and the content of the power grid so as to offset the harmonic current of the system.
Step 103: and confirming the single-phase earth fault according to the set criterion of the single-phase earth fault, and injecting the compensation power grid grounding capacitance current into the grounding loop.
Step 104: according to the grid fault characteristic quantity and the over-current and over-voltage limit values of the IGBT of the device, an automatic splitting program is set to realize safe parking, so that the accident expansion is avoided; the grid fault characteristic quantity comprises frequency, amplitude and phase.
In the step, in the operation process of the device, an automatic splitting program is set according to the characteristic quantity (frequency, amplitude and phase) of the power grid fault and the over-current and over-voltage of the IGBT of the device to realize safe parking, so that the expansion of accidents is avoided. Wherein the overcurrent and overvoltage can be self-protected by the overcurrent protector 13 and the overvoltage protector 14.
Step 105: the direct current source stabilization of the ground capacitive current compensation is realized by a super capacitor bank in the device.
Step 106: and mode smooth control of compensating harmonic current and power grid grounding capacitance current is realized through current feedforward.
In the step, mode smooth control of compensating harmonic current and power grid grounding capacitance current is realized through current feedforward, and control mode conversion is completed. The current feed-forward control can be seen in fig. 4.
According to the technical scheme, the grid-connected intelligent fault processing method for the power distribution network can achieve a filtering function for improving the quality of the power grid and a protection function for single-phase earth faults, meanwhile, through designing grid connection and disconnection procedures, and using the super capacitor bank as a voltage stabilizing and energy converting unit on a direct current side, the safety of equipment and a system is improved, the power grid accidents caused by the self-problem of the equipment are avoided being further expanded, the self-protection, grid connection and disconnection technology of the equipment is involved in the embodiment, and the method is an advanced technology of power electronic equipment with complex functions in the application of a power system.
In a preferred embodiment, the flexible impact-free grid connection is based on a grid voltage oriented vector control (VOC) technology, and grid information is realized through a phase-locked loop (PLL).
In a preferred embodiment, the system harmonic current detection is based on ip-iqThe method is obtained by transforming a matrix as follows:
in the formula ia、ib、icRespectively, the three-phase current detected by the device; i.e. ip、iqActive and reactive currents, respectively.
In a preferred embodiment, the setting criterion of the single-phase earth fault is:
zero sequence voltage U0Greater than a set value U0ref(ii) a The reduction rate of any phase voltage is smaller than a set value, and the increase rates of the other two phase voltages are larger than the set value; at the same time, increaseApplying current criterion, grounding capacitance current is less than or equal to set IcREF；
In the formula, Δ Ua＝Ua-Urm，ΔUb＝Ub-Urm，ΔUc＝Uc-Urm；U0Is zero sequence voltage, U0refIs the zero sequence voltage reference value, Δ Ua、ΔUb、ΔUcRespectively, the rate of change of voltage, ICIs a measurement of the earth current, ICREFIs a reference value of the ground current, UminrefIs the voltage minimum reference value, UmaxrefIs the reference value of the maximum voltage, UrmIt is the voltage amplitude, x ↓ and ↓ represent the voltage drop and rise, respectively.
In a preferred embodiment, the capacitive grounding current of the power grid is measured on line and confirmed by means of off-line measurement, when the grounding current measured value I is measuredCAfter the current is larger than the set upper current limit of the device, directly entering a splitting procedure to protect the device;
Ic＝3ωCUrm
where ω is the grid angular frequency, C is the grounding capacitance, UrmIs the voltage amplitude.
It can be understood that the implementation of the grid-connection method requires the acquisition of the three-phase grid voltage and the three-phase grid current. In a preferred embodiment, the automatic de-listing procedure comprises: voltage and current state detection, state word uploading, fault word uploading and shutdown instruction issuing.
In a preferred embodiment, the automatic splitting procedure specifically includes:
step 1041: and (5) grid-connected operation.
Step 1042: and detecting voltage and current faults and uploading the marks.
Step 1043: and circularly judging whether the fault word is valid, if so, executing 1044, and otherwise, continuing to execute the step 1043.
Step 1044: the fault word is uploaded, a shutdown instruction is issued, the status word is reset, and step 1046 is performed.
Step 1045: and when the compensating grounding capacitive current is larger than the set current upper limit of the device, directly entering into the splitting parking, and executing the highest priority.
In this step, it will be appreciated that the compensated capacitive grounding current is compared to the measured value of grounding current I described aboveCAre equal.
Step 1046: and (5) separating and parking.
As can be seen from the above description, the present embodiment provides an apparatus and a method that can achieve the dual purposes of improving the quality of power and handling single-phase ground fault. The embodiment relates to self-protection, grid connection and disconnection technologies of the equipment, and is an advanced technology of the power electronic equipment with complex functions in the application of a power system.
The above examples are only for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A grid-connected intelligent fault processing method of a grid-connected intelligent fault processing device of a grid-connected power distribution network is characterized in that the grid-connected intelligent fault processing device of the grid-connected power distribution network comprises the following steps: the system comprises four single-phase transformers, four reactors, four independent IGBT bridge arms, an overcurrent protector, an overvoltage protector, a super capacitor bank and a grounding circuit;
one end of a single-phase transformer 1 is connected with A, and the other end of the single-phase transformer is connected with a first end of a reactor 1; one end of the single-phase transformer 2 is connected with the B, and the other end of the single-phase transformer is connected with the first end of the reactor 2; one end of the single-phase transformer 3 is connected with the C, and the other end of the single-phase transformer 3 is connected with the first end of the reactor 3; one end of the single-phase transformer 4 is connected with a zero line, and the other end of the single-phase transformer 4 is connected with a first end of the reactor 4; one end of the zero line is connected with a grounding circuit;
the second end of the reactor 1 is connected with the IGBT bridge arm 1; the second end of the reactor 2 is connected with the IGBT bridge arm 2; the second end of the reactor 3 is connected with the IGBT bridge arm 3; the second end of the reactor 4 is connected with the IGBT bridge arm 4;
the over-current protector is connected between the zero line and the IGBT bridge arm 4; the overvoltage protector and the super capacitor bank are respectively connected between a positive bus and a negative bus of the device, and the super capacitor bank is used as a voltage stabilizing and energy converting unit at a direct current side;
the method for processing the intelligent fault of the grid-connected power distribution network comprises the following steps:
step S1: the signal acquisition device automatically tracks the frequency, amplitude and phase of the voltage of the power grid to realize flexible non-impact grid connection;
step S2: injecting compensation harmonic current according to the harmonic frequency and the content of the power grid so as to offset the harmonic current of the system;
step S3: confirming the single-phase earth fault according to the set criterion of the single-phase earth fault, and injecting the compensating power grid grounding capacitance current into the grounding loop;
step S4: according to the grid fault characteristic quantity and the over-current and over-voltage limit values of the IGBT of the device, an automatic splitting program is set to realize safe parking, so that the accident expansion is avoided; the grid fault characteristic quantity comprises frequency, amplitude and phase;
step S5: the direct current source stabilization of the grounding capacitive current compensation is realized through a super capacitor bank in the device;
step S6: and mode smooth control of compensating harmonic current and power grid grounding capacitance current is realized through current feedforward.
2. The method according to claim 1, characterized in that the flexible non-impact grid connection is based on grid voltage oriented vector control (VOC) technology, and grid information is implemented by means of Phase Locked Loops (PLL).
3. According to the rightThe method of claim 1, wherein system harmonic current detection is based on ip-iqThe method is obtained by transforming a matrix as follows:
in the formula ia、ib、icRespectively, the three-phase current detected by the device; i.e. ip、iqActive and reactive currents, respectively.
4. The method according to claim 1, characterized in that the set criteria for the single-phase earth fault are:
zero sequence voltage U0Greater than a set value U0ref(ii) a The reduction rate of any phase voltage is smaller than a set value, and the increase rates of the other two phase voltages are larger than the set value; meanwhile, a current criterion is added, and the grounding capacitance current is less than or equal to a set IcREF；
In the formula, Δ Ua＝Ua-Urm，ΔUb＝Ub-Urm，ΔUc＝Uc-Urm；U0Is zero sequence voltage, U0refIs the zero sequence voltage reference value, Δ Ua、ΔUb、ΔUcRespectively, the rate of change of voltage, ICIs a measurement of the earth current, ICREFIs a reference value of the ground current, UminrefIs the voltage minimum reference value, UmaxrefIs the reference value of the maximum voltage, UrmIt is the voltage amplitude, x ↓ and ↓ represent the voltage drop and rise, respectively.
5. Method according to claim 1, characterized in that the capacitive earth current of the network is measured on-line and confirmed by means of off-line measurement, when the earth current is presentFlow measurement value ICAfter the current is larger than the set upper current limit of the device, directly entering a splitting procedure to protect the device;
Ic＝3ωCUrm
where ω is the grid angular frequency, C is the grounding capacitance, UrmIs the voltage amplitude.
6. The method of claim 1, wherein the auto-unlink procedure comprises: voltage and current state detection, state word uploading, fault word uploading and shutdown instruction issuing.
7. The method according to claim 1 or 6, wherein the automatic de-listing procedure specifically comprises:
step S41: grid-connected operation;
step S42: detecting voltage and current faults and uploading the marks;
step S43: judging whether the fault word is valid or not in a circulating manner, if so, executing S44, and otherwise, continuing to execute the step S43;
step S44: uploading a fault word, issuing a shutdown instruction, resetting a state word at the same time, and executing the step S46;
step S45: when the compensation grounding capacitive current is larger than the upper limit of the current set by the device, the device directly enters into the splitting parking and executes the highest priority;
step S46: and (5) separating and parking.
8. The method according to claim 1, characterized in that an overvoltage protector on a direct current side in the grid-connected intelligent fault processing device for the power distribution network adopts a mode of connecting a drain resistor in series with an IGBT to realize rapid stabilization of the bus voltage after overvoltage.
9. The method according to claim 1, wherein the control process of the grid-connected intelligent fault handling device of the power distribution network is realized by a DSP control system, and comprises the following steps: the device comprises a data acquisition unit, an IGBT driving unit, a protection parameter setting unit and a data storage and uploading unit.
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