CN201029204Y - Lightning-proof and overvoltage-proof circuit used for double-feeding wind power generating system - Google Patents
Lightning-proof and overvoltage-proof circuit used for double-feeding wind power generating system Download PDFInfo
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- CN201029204Y CN201029204Y CNU2007201189317U CN200720118931U CN201029204Y CN 201029204 Y CN201029204 Y CN 201029204Y CN U2007201189317 U CNU2007201189317 U CN U2007201189317U CN 200720118931 U CN200720118931 U CN 200720118931U CN 201029204 Y CN201029204 Y CN 201029204Y
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The utility model discloses a lightning-proof overpressure resistance circuit which is used in the double-fed type wind power electric power system, comprising a cable which is arranged between the rotor side of a generator and the rotor wiring side of a convertor and at least a lightning arrester, the cable is earthed through the lightning arrester; in addition, the utility model also comprises a filter which is connected with the cable. The utility model is capable of protecting the convertor and the generator of the lightning-proof overpressure resistance circuit are free from the damage form the thunderstroke; the filter of the utility model is capable of restraining the overvoltage produced by the voltage reflection under the transmission condition of the long cable, protecting the generator is insolating and not damaged, and ensuring the lightning arrester is capable of working reliably.
Description
[ technical field ]
The utility model relates to an overvoltage crowbar is prevented in lightning protection for doubly-fed formula wind power generation system.
[ background art ]
Due to the influence of the installation position and the height of the wind power generation system, the wind power generation system is easy to be struck by lightning, and therefore the part which is easy to be struck by lightning needs to be protected by lightning. When the converter and the generator are not in the same installation position and a long cable is connected, the terminals of the rotor side of the generator and the rotor side of the converter are parts which are susceptible to lightning stroke, and need to be effectively protected. At present, the common practice is to consider no influence of lightning stroke, to have no lightning protection measure, or to simply install a lightning protector at the single end or the double ends of a cable connecting line.
However, for the double-fed wind power generator, under the condition of long-distance cable transmission, under the influence of the voltage reflection effect caused by the mismatch of the cable and the motor impedance, the PWM pulse square wave output by the rotor side of the converter generates voltage reflection on the rotor side of the generator, so as to generate peak overvoltage with higher amplitude on the rotor side of the generator and the rotor side of the converter, as shown in fig. 1.
The theory of application is the transmission line theory, the transmission line theory is a subject between the electromagnetic field theory and the circuit theory, and is the basis of the microwave circuit design, and the basic thought is as follows: the equivalent distributed circuit parameters are solved by the electromagnetic field theory, and the circuit theory is adopted for analysis. Since the transmission line theory itself covers a wide range, the theory is only applied directly to analyze the voltage reflection phenomenon.
When the long-wire cable is adopted for transmission, the pulse signal of PWM transmitted between the inverter and the motor is similar to the condition of traveling wave on the transmission line. The PWM pulse, as a forward traveling wave (incident wave), is transmitted from the inverter to the motor, reflected at the motor end to generate a backward traveling wave (reflected wave) and transmitted to the inverter, and the reflected wave transmitted to the output end of the inverter generates a second incident wave, and so on, as shown in fig. 21. To better understand the phenomenon of repeated reflection of traveling waves in the case of long cables between the inverter and the motor, a reflection process of the PWM pulses is first discussed. It is assumed here that the dv/dt of a PWM pulse is infinite. The equivalent circuit of the PWM inverter at the transmission line source end is shown in fig. 21 (a). Since the motor impedance is large at high frequency and can be an open circuit, when the switching device is turned on, the voltage and current of the incident wave are transmitted to the right simultaneously, and the waveforms are the same and have different amplitudes, as shown in fig. 21 (b). When the incident wave reaches the end of the transmission line, it is reflected, as shown in fig. 21 (c). The current at any time when the transmission line is open is zero, so the reflected wave current should be the same magnitude as the incident wave, but opposite in sign. The incident voltage forms a reflected wave of positive voltage, which is transmitted to the source side (shown by the dotted line) to the left. The reflected wave adds to the incident wave, doubling the motor terminal voltage (shown in solid lines). The voltage of the transmission line is 2E before the reflected wave reaches the source. However, when the output voltage of the source inverter is E, a negative reflected wave having a voltage of-E should be transmitted from the inverter to the motor, as shown in fig. 21 (d). The voltage traveling wave must also travel with a current wave, and since the direction of travel is positive, the sign of the current is the same as that of the voltage, i.e., -I. This second incident wave arrives at the terminal very quickly, as shown in fig. 21 (e), and is also reflected. The second incident wave is negative, and since the current should be zero when the circuit is open, the current of the second reflected wave should be positive, I. This positive current must be carried to the left with a negative voltage. The third incident wave is the same as the first and does not need to be studied.
The reflection mechanism can be seen as a mirror to a forward traveling wave V + The reflection generates a reflected wave V - ，V - As V + Is equal to V + Multiplied by the voltage reflection coefficient. Reflection coefficient of terminal (load) end L Comprises the following steps:
wherein Z L Is the load (motor) impedance, Z 0 For the characteristic impedance of the cable, neglecting the cable loss, there are
Wherein L is 0 Inductance value per unit length of cable, C 0 Is the capacitance value of the potential length cable.
Source end voltage reflection coefficient gamma S Comprises the following steps:
wherein Z S For source side impedance, generally Z S ≈0，Γ S ≈-1。
Therefore, at the inverter side, the forward traveling wave obtained after reflection has the same waveform as the transmitted backward traveling wave, but the amplitude is reduced to Γ of the backward traveling wave S And (4) doubling. And the reflected wave obtained after the incident wave is reflected is transmitted to the inverter,the value of the reflected wave is equal to its value multiplied by the load reflection coefficient Γ L The characteristic impedance Z of the machine is large due to its large winding inductance L For the characteristic impedance Z of the cable 0 10 to 100 times of that, i.e. Z L Is far greater than Z 0 As shown in the formula (1), gamma-ray L 1, the incident wave is superimposed with the reflected wave so that the motor terminal voltage is approximately doubled.
According to the traveling wave transmission theory and the analysis of the voltage reflection phenomenon, the peak voltage amplitude at the motor end can be obtained. Time t required for transmission of output pulse of inverter from inverter to motor t Comprises the following steps:
wherein t is t The time required for a pulse to travel once in the cable, l is the cable length, v is the propagation velocity of the pulse:
elapsed time t t Then, the output pulse of the inverter transmitted in the forward direction is reflected at the motor end, and as a result, a backward traveling wave is generated and moves to the inverter, and when t t ＜t r Then, its amplitude is:
when t is t ＞＞t r Then, its amplitude is:
V t (t t )＝V DC Γ L (7)
in the formula: v DC Is a dc bus voltage; t is t r The pulse rise time is output for the inverter.
In the case where a lightning arrester is additionally installed on a cable connection line, the overvoltage may cause the lightning arrester to be deteriorated and damaged due to frequent operations. When the lightning protection device is not additionally arranged on the cable connecting wire or the action voltage of the lightning protection device is too high, the overvoltage can also have adverse effects on the insulation of the generator winding and the rotor side of the converter, and equipment can be damaged in the case of lightning stroke.
[ summary of the invention ]
The to-be-solved technical problem of the utility model is to provide a lightning protection overvoltage crowbar for wind power generation system can restrict the overvoltage that produces on the cable junction line, improves the reliability of system's lightning protection.
The technical scheme of the utility model is that:
a lightning and overvoltage protection circuit for a doubly-fed wind power generation system comprises a cable connected between a rotor side of a generator and a rotor connection side of a converter, and at least one lightning protector, the cable being grounded through the lightning protector, and a filter electrically connected with the cable.
The lightning protection is connected to the cables near the rotor side of the generator and/or to the cables near the rotor connection side of the converter.
The lightning and overvoltage protection circuit for the double-fed wind power generation system further comprises a fuse, and the fuse is connected between the cable and the lightning protector in series.
The lightning and overvoltage protection circuit for the double-fed wind power generation system further comprises a circuit breaker which is connected between the cable and the lightning protector in series.
The filter is a filter for matching the input impedance of the generator with the characteristic impedance of the cable, and is electrically connected to the cable on the side close to the rotor of the generator. Wherein the filter is an RLC type or RC type filter.
The filter is a filter for increasing the rise time of the output PWM pulse of the converter, and is connected in series between the rotor connection side of the converter and a cable near the rotor connection side of the converter. Wherein the filter is a reactor, an LR output filter, an LC output filter or an RLC output filter.
The lightning protection device is a piezoresistor, or a discharge gap, or a gas discharge tube, or a series connection of the piezoresistor and the discharge gap, or a series connection of the piezoresistor and the gas discharge tube.
The beneficial effects of the utility model are that:
the utility model can limit the overvoltage generated by the generator rotor side due to the long-line transmission effect by connecting the filter at the terminal of the generator rotor side and/or the converter rotor side, absorb and consume the peak overvoltage energy, and avoid the lightning protection device from being damaged due to the deterioration caused by frequent actions; under the condition of lightning surge, the lightning protection device can provide a bypass discharge channel for the surge so as to prevent the surge from invading into a generator or a converter to cause equipment damage; because the overvoltage is eliminated, the lightning arrester does not act under the condition of normal operation of the system, and can reliably act when lightning surges exist, thereby ensuring the safe operation of the system; the fuse is connected in the circuit to ensure that the lightning protection device can be disconnected from the power line after the lightning protection device fails or is damaged, so that the lightning protection device is prevented from being on fire.
[ description of the drawings ]
Fig. 1 is a diagram illustrating a peak overvoltage caused by voltage emission on a motor side in long-line transmission.
Fig. 2 is the system schematic diagram (one) of the present invention.
Fig. 3 is a system schematic diagram (ii) of the present invention.
Fig. 4 is a system schematic diagram (iii) of the present invention.
Fig. 5 is a system schematic diagram (iv) of the present invention.
Fig. 6 is a system schematic diagram (v) of the present invention.
Fig. 7 is a system schematic diagram (six) of the present invention.
Fig. 8 is a schematic diagram (a) of the filter connected to the rotor side of the generator according to the present invention.
Fig. 9 is a schematic diagram (ii) of the filter connected to the generator rotor side according to the present invention.
Fig. 10 is a schematic diagram (one) of the filter connected to the rotor connection side of the converter according to the present invention.
Fig. 11 is a schematic diagram (ii) of the filter connected to the rotor connection side of the converter according to the present invention.
Fig. 12 is a schematic diagram (iii) of a filter connected to the rotor connection side of the converter according to the present invention.
Fig. 13 is a schematic diagram (iv) of the filter connected to the rotor connection side of the converter according to the present invention.
Fig. 14 is a schematic diagram (v) of the filter connected to the rotor connection side of the converter according to the present invention.
Fig. 15 is a schematic view (a) of the lightning protection device of the present invention.
Fig. 16 is a schematic view (two) of the lightning protection device of the present invention.
Fig. 17 is a schematic view (iii) of the lightning protection device of the present invention.
Fig. 18 is a schematic view (four) of the lightning protection device of the present invention.
Fig. 19 is a schematic view (a) of the protection mode for the lightning protection device according to the present invention.
Fig. 20 is a schematic view (ii) of the protection mode of the lightning protection device of the present invention.
Fig. 21 is a schematic diagram of voltage repetitive reflection.
[ detailed description of the invention ]
The invention will be further elucidated with reference to the following figures and embodiments:
fig. 2 to 7 are schematic diagrams of the system of the present invention, and the lightning protection overvoltage protection circuit for a doubly-fed wind power generation system of the present invention includes a cable, a filter and at least one lightning protection device connected between a rotor side of a generator and a rotor connection side of a converter, wherein two lightning protection devices are used in fig. 2 and 3, and one lightning protection device is used in fig. 4 to 7; in fig. 2, the cable near the rotor side of the generator is grounded through a lightning protector, and the cable near the rotor connection side of the converter is grounded through another lightning protector, and the filter is electrically connected to the cable near the rotor side of the generator; in fig. 3, the filter is connected in series between the rotor connection side of the converter and the cable close to the rotor connection side of the converter; in fig. 4 and 5, the same is that: the cables close to the rotor connection side of the converter are earthed by means of a lightning protection, with the difference that: the filter of fig. 4 is electrically connected to the cable near the rotor side of the generator, and the filter of fig. 5 is connected in series between the rotor connection side of the converter and the cable near the rotor connection side of the converter; in fig. 6 and 7, the same is that: the cables close to the rotor side of the generator are earthed by means of lightning protection, and the difference lies in: the filter of fig. 6 is electrically connected to the cable near the rotor side of the generator, and the filter of fig. 7 is connected in series between the rotor connection side of the converter and the cable near the rotor connection side of the converter.
In the double-fed wind power system, a converter adopts high-frequency switching devices such as IGBT (insulated gate bipolar transistor) and the like, the output pulse of a PWM (pulse-width modulation) inverter can rise in a short time to generate large dv/dt, when the converter and a generator are not positioned at the same installation position and a long installation cable is needed for connection, a voltage reflection phenomenon can be generated when the PWM output pulse reaches a motor, and the reflection phenomenon is closely related to the rise time of the output pulse of the inverter and the length of the cable.
The transmission line theory analysis shows that the reason of the overvoltage generated at the motor end is caused by the fact that the rise time of the PWM pulse is close to the propagation time of the pulse on a cable, and voltage reflection occurs at the motor end due to the fact that the characteristic impedance of the cable is not matched with that of the motor. Further analysis shows that, under the condition of a certain cable length, the magnitude of the reflected overvoltage mainly depends on the rising speed of the PWM pulse and the impedance difference between the cable and the motor: the faster the PWM pulse rises, the more the cable is very different from the magnitude of the impedance of the motor, the more pronounced the spike over-voltage caused by voltage reflections.
The wind power system is influenced by factors such as installation height and position and is easy to be struck by lightning. When the converter and the generator are not located at the same installation position and a long installation cable is needed to be connected, the connection cable is very close to a down lead of the wind power system direct lightning protection, lightning induced overvoltage with high amplitude is easy to generate, and partial direct lightning current can flow into the connection cable, so that the terminals of the rotor side of the generator and the rotor side of the protector need to be effectively protected against lightning. This is achieved by mounting lightning protection devices on the generator rotor side and on the converter rotor connection side.
The core component of the lightning protector is a nonlinear device, comprises a metal oxide piezoresistor, a gas discharge tube, a discharge gap or the like, or a combination thereof, and when the voltage applied to the two ends of the lightning protector is less than the action voltage of the lightning protector, the lightning protector does not act; when the voltage reaches the action voltage, the lightning protector acts and limits the voltage to a relatively low level, thereby realizing the protection effect on the protected circuit.
Although the energy contained in a single pulse is not large, the peak overvoltage caused by voltage reflection under the condition of long cable transmission needs to be suppressed because the occurrence frequency is high, and the lightning protection device is damaged due to frequent action or deterioration and even caused to fire due to repeated action on the lightning protection device.
In order to suppress the peak overvoltage caused by voltage reflection, a method of adding a filter on the motor side or the converter side may be adopted. The filter is added at the input end of the motor, and the function of the filter is to reduce the input impedance of the motor and enable the input impedance to be matched with the characteristic impedance of the cable; and a filter is added on the side of the converter, and the filter has the function of increasing the rising time of the PWM pulse output by the converter and reducing dv/dt. By connecting the filter, overvoltage generated by a long-line transmission effect at the rotor side of the generator can be limited, peak overvoltage energy consumption is absorbed, and the lightning protector is prevented from being damaged due to deterioration caused by frequent actions; the lightning protector is used for providing a bypass discharge channel for the surge in case of lightning surge so as to prevent the surge from invading a generator or a converter to cause equipment damage.
When the filter is electrically connected to the cable near the rotor side of the generator, the filter may be an RC type filter, as shown in fig. 8, the resistor and the capacitor are connected in series and in a star connection; the filter may also be an RLC type filter, as shown in fig. 9, in which a resistor is connected in parallel with an inductor and then connected in series with a capacitor, and a star connection mode is adopted.
When the filter is connected in series between the rotor connection side of the converter and the cable close to the rotor connection side of the converter, the filter may be a reactor, as shown in fig. 10, i.e. three inductors are used in series in three cables; the filter may be an LR output filter, as shown in fig. 11, that is, on the basis of fig. 10, a resistor is connected in parallel with each inductor; the filter may be an LC output filter, as shown in fig. 12, based on fig. 10, three capacitors are added, first ends of the three capacitors are respectively connected to one ends of the three inductors, and second ends of the three capacitors are connected in a star connection; the filter may be an RLC output filter, as shown in fig. 13 and fig. 14, fig. 13 is a circuit diagram of fig. 12 in which a resistor is connected in series to each capacitor, so that the first end of the capacitor is connected to one end of three inductors through the series resistor, and fig. 14 is a circuit diagram of fig. 12 in which a resistor is connected in parallel to each capacitor.
It should be noted that the structure of the filter can also adopt a delta connection method, and the function of suppressing overvoltage can be realized, so that the purpose of the utility model is realized.
The utility model discloses a lightning protection device schematic diagram is shown as figure 15, figure 16, figure 17 and figure 18, in figure 15, the lightning protection device comprises piezo-resistor and the series connection of discharge gap, or piezo-resistor and gas discharge tube's series connection, and in figure 16, the lightning protection device then adopts three piezo-resistor to establish ties with same discharge gap or gas discharge tube jointly and constitutes, in figure 17, the lightning protection device then adopts discharge gap or gas discharge tube to constitute alone, in figure 18, the lightning protection device then adopts piezo-resistor to constitute alone.
In addition, in order to prevent the possible fire problem after the failure or damage of the lightning protection device, a suitable fuse or breaker is required to be additionally installed, and the lightning protection device can be reliably disconnected from the power line after the short circuit failure or damage of the lightning protection device. The mode of fuse and lightning protection device series connection is adopted to the protection mode to the lightning protection device in fig. 19, the fuse is connected in series between the cable and the lightning protection device, and the mode of circuit breaker and lightning protection device series connection is adopted to the protection mode to the lightning protection device in fig. 20, the circuit breaker is connected in series between the cable and the lightning protection device.
The utility model can protect the converter and the generator in the double-fed wind power system from being damaged by lightning; the novel medium filter of this practicality can restrain the overvoltage that voltage reflection caused under the long cable transmission condition, and protection generator is insulating not destroyed, also ensures that the lightning protection device can reliable work.
Claims (9)
1. A lightning protection and overvoltage protection circuit for a doubly-fed wind power generation system, comprising a cable connected between a rotor side of a generator and a rotor connection side of a converter, and at least one lightning protector, the cable being grounded through the lightning protector, characterized in that: also included is a filter electrically connected to the cable.
2. The lightning and overvoltage protection circuit for the doubly-fed wind power generation system of claim 1, wherein: the at least one lightning protection device is connected to the cable close to the rotor side of the generator and/or to the cable close to the rotor connection side of the converter.
3. A lightning and overvoltage protection circuit for a doubly-fed wind power generation system according to claim 1 or 2, characterised in that: the lightning protection device also comprises a fuse which is connected between the cable and the lightning protection device in series.
4. A lightning and overvoltage protection circuit for a doubly-fed wind power generation system according to claim 1 or 2, characterised in that: the lightning protection device also comprises a circuit breaker which is connected between the cable and the lightning protection device in series.
5. A lightning and overvoltage protection circuit for a doubly-fed wind power generation system according to claim 1 or 2, characterised in that: the filter is a filter for matching the input impedance of the generator with the characteristic impedance of the cable, and is electrically connected to the cable near the rotor side of the generator.
6. The lightning and overvoltage protection circuit for the doubly-fed wind power generation system of claim 5, wherein: the filter is an RLC type or RC type filter.
7. A lightning and overvoltage protection circuit for a doubly-fed wind power generation system according to claim 1 or 2, characterized in that: the filter is a filter for increasing the rise time of the output PWM pulse of the converter, and is connected in series between the rotor connection side of the converter and a cable near the rotor connection side of the converter.
8. The lightning and overvoltage protection circuit for the doubly-fed wind power generation system of claim 7, wherein: the filter is a reactor, an LR output filter, an LC output filter or an RLC output filter.
9. A lightning and overvoltage protection circuit for a doubly-fed wind power generation system according to claim 1 or 2, characterised in that: the lightning protection device is a piezoresistor, or a discharge gap, or a gas discharge tube, or the series connection of the piezoresistor and the discharge gap, or the series connection of the piezoresistor and the gas discharge tube.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2007201189317U CN201029204Y (en) | 2007-03-13 | 2007-03-13 | Lightning-proof and overvoltage-proof circuit used for double-feeding wind power generating system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2007201189317U CN201029204Y (en) | 2007-03-13 | 2007-03-13 | Lightning-proof and overvoltage-proof circuit used for double-feeding wind power generating system |
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| CN201029204Y true CN201029204Y (en) | 2008-02-27 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNU2007201189317U Expired - Lifetime CN201029204Y (en) | 2007-03-13 | 2007-03-13 | Lightning-proof and overvoltage-proof circuit used for double-feeding wind power generating system |
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| CN (1) | CN201029204Y (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102868145A (en) * | 2012-06-25 | 2013-01-09 | 山亿新能源股份有限公司 | Lightning-proof equipment of micro-inverter |
| CN102957311A (en) * | 2012-11-14 | 2013-03-06 | 四川东方电气自动控制工程有限公司 | Anti-electromagnetic interference system of megawatt-level wind power converter |
| CN104578071A (en) * | 2014-12-26 | 2015-04-29 | 东莞市华炜雷电防护设备有限公司 | High-energy filtering protector |
| WO2016000220A1 (en) * | 2014-07-02 | 2016-01-07 | Ge Energy Power Conversion Technology Ltd | Overvoltage protection self-trigger circuit for double fed induction generator (dfig) wind power system |
| CN107863766A (en) * | 2016-09-22 | 2018-03-30 | 维谛技术有限公司 | A kind of current transformer primary heat transport system and current transformer |
| CN113346364A (en) * | 2021-04-30 | 2021-09-03 | 华能湖北新能源有限责任公司 | Cable terminal explosion-proof system and method |
-
2007
- 2007-03-13 CN CNU2007201189317U patent/CN201029204Y/en not_active Expired - Lifetime
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102868145A (en) * | 2012-06-25 | 2013-01-09 | 山亿新能源股份有限公司 | Lightning-proof equipment of micro-inverter |
| CN102957311A (en) * | 2012-11-14 | 2013-03-06 | 四川东方电气自动控制工程有限公司 | Anti-electromagnetic interference system of megawatt-level wind power converter |
| CN102957311B (en) * | 2012-11-14 | 2015-11-18 | 四川东方电气自动控制工程有限公司 | A kind of anti-electromagneticinterference interference system of megawatt-level wind power converter |
| WO2016000220A1 (en) * | 2014-07-02 | 2016-01-07 | Ge Energy Power Conversion Technology Ltd | Overvoltage protection self-trigger circuit for double fed induction generator (dfig) wind power system |
| CN104578071A (en) * | 2014-12-26 | 2015-04-29 | 东莞市华炜雷电防护设备有限公司 | High-energy filtering protector |
| CN107863766A (en) * | 2016-09-22 | 2018-03-30 | 维谛技术有限公司 | A kind of current transformer primary heat transport system and current transformer |
| CN113346364A (en) * | 2021-04-30 | 2021-09-03 | 华能湖北新能源有限责任公司 | Cable terminal explosion-proof system and method |
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Granted publication date: 20080227 |