CN110601206A - Earth fault current compensation system and method for self-generating power phase power supply - Google Patents

Abstract

The invention discloses a ground fault current compensation system and method for self-produced power supply phase power supply, comprising a phase power supply power supply generator, a phase power supply power supply phase compensator, a switching switch, a controller and a voltage regulator. The input end of the generator is connected with the bus bar, the output end of the phase power supply generator is connected with the input end of the phase power supply phase compensator, and the voltage regulator is connected in series between the power supply phase compensator and the neutral point of the system. During the time, the controller is connected with the voltage transformer of the bus, and the output end of the controller is connected with the switching switch. The system passively generates power supply phase power, and puts the reverse phase power supply phase power supply and harmonic phase power supply into the system according to the fault logic. Realize the complete compensation of the ground fault reactive current, harmonic current and active current of the distribution network, and overcome the problems that the power electronic device inverter injection method cannot achieve full compensation and the control is complicated after the power is drawn from the system.

Description

A ground fault current compensation system and method for self-produced power supply phase power supply

technical field

The invention relates to the technical field of distribution network, in particular to a ground fault current compensation system and method for self-produced power supply phase power supply.

Background technique

Single-phase grounding faults in distribution networks at home and abroad account for more than 80%, which seriously affects the safe operation of power grids and equipment. Safely handling grounding faults plays an important role in social and economic development. When the capacitance current of the system is greater than 10A, the grounding method of the arc suppression coil is adopted. The arc suppression coil can reduce the fault current to a certain extent, and the system can run for 2 hours with a fault, but the arc suppression coil cannot achieve full compensation, and there is still a residual current of less than 10A at the fault point, which can cause personal electric shock and fire accidents. , and a serious threat to the safe and stable operation of power grids and equipment. When the capacitance current of the system is large, the small resistance grounding method is mostly used. When a single-phase grounding fault occurs, the zero-sequence current of the faulty line is amplified, and the relay protection device quickly cuts off the faulty line. However, the reliability of power supply in this grounding method is difficult to guarantee. , and there is a risk that the relay protection will refuse to act when the high-resistance is grounded.

At present, in order to completely eliminate the hazards of single-phase grounding faults, and at the same time ensure the reliability of power supply. Many methods have been proposed at home and abroad to fully compensate the single-phase ground fault point current.

Swedish Neutral published "The Application of Ground Fault Neutralizer Full Compensation Technology" and disclosed a method of compensating the ground fault point current by injecting current into the neutral point of the system through an active compensator. However, the ground fault residual current in this method cannot be obtained directly, and the residual current value is calculated by using the system-to-ground distribution parameters, and the deviation is large; at the same time, the compensator uses power electronic devices to control the current phase and amplitude. The accuracy of the value cannot be guaranteed at the same time, and the harmonic content of the compensation current is large, the control is complicated, and the stability is poor; therefore, the compensation effect of the GFN (ground fault neutralizer) manufactured by Swedish Neutral deviates greatly from the ideal value. The results of the simulation test show (Zhejiang Electric Power, 2018-04 Field Test Research on Fault Line Selection Based on Neutral Point Full Compensation Technology), for metallic ground faults, the ground residual current after compensation by the GFN device is still above 5A , and the ideal value, that is, the zero current has a large gap, and is only equivalent to the compensation effect of the arc suppression coil.

Domestically, the patent CN102074950A discloses a ground fault arc suppression and protection method of a distribution network, which is similar to the arc suppression method of Swedish Neutral. The fault phase voltage is suppressed to zero by injecting current into the neutral point of the distribution network. This method has the problem of how to control the fault voltage to be 0 when the fault phase voltage is 0 when the metal is grounded. This method only applies high resistance to grounding. The fault has an effect, and to control the fault phase voltage, it is necessary to accurately control the amplitude and phase of the injected current, which is difficult to achieve.

The patent with application number 201710550400.3 discloses an active step-down safety processing method for ground faults in non-effective grounding systems. The method is provided with taps on the side windings of the transformer system. By short-circuiting the faulty phase winding taps to ground or short-circuiting through impedance, the fault is reduced. Phase voltage to achieve the purpose of limiting the current at the ground fault point. In essence, this method is to create another grounding point on the bus side of the system when a single-phase grounding occurs in the power grid line, and shunt the original single-phase grounding current. Obviously, this method has poor compensation effect for metallic single-phase grounding faults. Even invalid, and the device malfunction will cause a short circuit between phases.

Patents with application numbers 201710544978.8 and 201710544976.9 disclose methods for phase-down and arc suppression of ground faults in non-effectively grounded systems. Both methods are: when a single-phase grounding fault occurs, the busbar and ground on the side of the non-effectively grounded system, or External power is applied between the line and ground, or neutral point and ground, or between the tap and ground of the winding on the side of the neutral point non-effectively grounded system, in order to reduce the fault voltage. The only difference between the two methods is that one of the external power sources is a voltage source and the other is a current source, and there is no essential difference. There is also the problem of the phase voltage accuracy of the control system of the voltage source and the current source, and the problem that the phase-to-ground voltage is zero and cannot be controlled when the metal is short-circuited. In the implementation of the two methods, if the external power supply is directly applied between the busbar or the line and the ground, the system line voltage will be changed, causing the system load (such as the distribution transformer) to fail to operate normally.

To sum up, in the prior art, there is no simple, accurate and efficient method for complete compensation of single-phase ground fault current, which can take into account the reliability and safety of power supply of the power distribution system.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a ground fault current compensation system and method for self-produced power supply phase power supply, through the phase power supply power supply generator, the phase power supply phase compensator and the voltage regulator to change the line power supply on the bus. For the reverse phase power supply, combined with the neutral point of the switching switch access system, the faulty phase is connected to suppress the overvoltage of the faulty phase, so as to achieve the purpose of full compensation. It effectively solves the problems of complicated current control in the single-phase grounding fault of the power distribution system, and it is difficult to completely compensate for the metallic grounding. In order to achieve the purpose of full current and voltage compensation, the present invention has no arc after complete compensation, avoids the risk of personal electric shock, and improves power supply reliability and power supply safety.

The present invention solves the above-mentioned technical problems through the following technical means:

The invention provides a ground fault current compensation system for self-produced power supply phase power supply, including a phase power supply power supply generator, a phase power supply power supply phase compensator, a switching switch, a controller and a voltage regulator. The power generator and the phase compensator of the phase power supply are transformed into a three-phase power supply with the same amplitude as the power supply phase. The phase voltage with the same amplitude and opposite phase as the power supply is obtained at the neutral point, so as to achieve the purpose of fully compensating the passive ground fault current and ensuring the reliability and safety of the system power supply.

Further, the phase power supply generator converts the system line voltage into phase voltage to generate power supply phase power. The connection form of the phase power supply generator is Dy or Zy or Yd or Yy. There is a phase difference between the phase voltage of the power supply and the power supply of the grid system and

in is the phase difference between the line voltage of the phase power generator and the line voltage corresponding to the grid system, n is an integer in the range [0,11].

The phase compensator of the phase power supply compensates the phase difference of the phase voltage generated by the generator of the phase power supply. Its connection form is Dyn or Zyn or Yyn, and its neutral point terminal must be grounded.

In order to implement this technology more conveniently, the following table shows the connection groups that can be used by some phase power supply generators and the connection groups that the corresponding phase power supply phase compensators should use, as shown in Table 1.

Table 1 Partial phase power supply generator and phase power supply phase compensator connection group

Further, the switching switch is a fast switching switch such as a mechanical switch, a power electronic switch, and the like.

Further, when the compensation current is output, the internal impedance of the phase power supply generator and the phase power supply phase compensator produces a voltage drop, so that the voltage amplitude obtained at the output end (ie the neutral point) of the phase power supply phase compensator will be Lower than the power supply voltage amplitude of the grid system. Therefore, in this technical solution, a voltage regulator is provided, and the voltage drop generated when the phase compensator of the phase power supply outputs the compensation current is adjusted by the voltage regulator. The non-identical terminals on both sides of the device are used to obtain the phase voltage with the same amplitude and opposite phase as the power supply at the neutral point.

The rated voltage of the primary winding of the phase power generator is not lower than the rated voltage of the grid system, and the rated voltage of the secondary winding of the voltage regulator, that is, the side connected to the neutral point of the grid system, is not lower than the rated voltage of the grid system.

Assuming that the rated voltage ratios of the phase power supply generator, phase power supply phase compensator and voltage regulator are m, n, and j, respectively, then m, n, and j should satisfy the following formula:

1≤m×n×j≤1.15

The voltage regulator is connected in series between the common connection point of the switching switch and the neutral point of the power grid system, and the common connection point of the switching switch and the neutral point of the system are connected to the non-identical terminals on both sides of the voltage regulator. The remaining connection points are grounded, and the voltage adjustment range of the voltage regulator is ±15% of the rated voltage. If it is necessary to control the ground fault current, the rated voltage adjustment range can be larger, such as voltage ±100% adjustable.

Further, the controller includes a fault judgment module and a switch control module.

The fault judging module judges whether the single-phase grounding occurs in the system and judges the grounding phase according to the system zero-sequence voltage, three-phase voltage, line zero-sequence current, etc. The switch control module controls the corresponding switch of the switching switch to close according to the grounding phase judged by the fault judging module. .

Further, the lead point of the primary winding of the phase power supply generator is connected to the busbar of the power grid system, and the lead point of the secondary winding of the phase power supply generator is respectively connected to the corresponding phase connection point of the primary winding of the phase compensator of the phase power supply.

A-phase compensation connection point, B-phase compensation connection point, C-phase compensation connection point and neutral point lead-out point com are respectively set on the secondary winding of the phase compensator of the phase power supply.

Further, the switching switch is provided with an A-phase switch connection point, a B-phase switch connection point, a C-phase switch connection point and a common connection point. The A-phase compensation connection point, B-phase compensation connection point, and C-phase compensation connection point of the secondary winding of the phase compensator of the phase power supply are respectively connected to the A-phase switch connection point, B-phase switch connection point, and C-phase switch of the switching switch. Junction.

On the other hand, a ground fault current compensation method for a self-produced power supply of the present invention includes:

S1: The controller judges whether the single-phase grounding occurs in the system and judges the grounding phase;

S2: A ground fault occurs in a phase, and the controller controls the switching switch to close the switch corresponding to the fault;

S3: Voltage compensation is performed through a voltage regulator;

S4: When the closing time of the switching switch reaches the set time, the controller controls the switching switch to disconnect;

S5: The controller continues to judge whether the single-phase ground fault exists;

S6: If the ground fault still exists, go to step 2, and if the single-phase grounding does not exist, the single-phase grounding compensation process ends.

Further, the disconnection time of the switching switch set in the step S4 is set according to the line operating conditions, such as the disconnection time of the line tree barrier with many ground faults or other situations that are likely to cause many ground faults.

The invention creatively proposes to pass the constant line voltage before and after the single-phase grounding in the system through the phase power supply generator; Active power and reactive power formed by ground impedance. The purpose of complete compensation is to suppress the voltage and current of the single-phase grounding fault point to zero. Under the single-phase grounding fault, the system can be operated with electricity, and the single-phase grounding fault point has no risk of electric shock and arcing; and the method provided by the invention only controls the opening and closing of the switch, which greatly simplifies the single-phase grounding fault full compensation technology. Control Method.

The beneficial effects of the present invention are:

(1) The technical solution proposed by the present invention obtains the power supply from the system with the phase voltage opposite to that of the system power supply and the same amplitude through passive components, which can completely compensate the single-phase grounding fault point current, eliminate the grounding arc, and ensure the power supply of the power grid system. Reliability, avoiding the risk of personal electric shock. It enables the grid system to continuously supply power and improves the security of power supply.

The compensation system proposed by the present invention can use passive components to obtain components whose phases are opposite to the phase voltage of the power supply of the faulty phase of the system, without the need for phase adjustment, only to adjust the voltage amplitude and switch the corresponding switch. Compared with the existing active full compensation technology based on power electronic inverter technology, its compensation accuracy is higher, the control method is simpler, and it has incomparable technical advantages.

(2) In the technical solution provided by the present invention, the transformers, voltage regulators, capacitors, switches and other components that can operate stably for a long time are used, and the stability is obviously better than that of power electronic devices that are easily damaged; and the maintenance is complicated. Compared with the power electronic inverter power supply, the components used in this technical solution are commonly used and mature components of the power system that are easy to maintain or even maintenance-free; the components used in this technical solution are mature in technology and low in cost; Compared with the full source compensation technology, the hardware cost, R&D cost and maintenance cost in the implementation of the technical solution are relatively low, and the stability is high and the maintenance cost is low.

Description of drawings

1 is a schematic diagram of a ground fault current compensation system of a self-produced power supply according to the present invention;

2 is a flow chart of a ground fault current compensation method for a self-produced power supply according to the present invention;

Figure 3 is a schematic diagram of the composition of the controller;

Among them: phase power supply generator 1 , phase power supply phase compensator 2 , switching switch 3 , controller 4 , voltage regulator 5 , fault judgment module 41 and switch control module 42 .

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, those skilled in the art will All other embodiments obtained without creative work fall within the scope of protection of the present application.

As shown in Figures 1-2, a ground fault current compensation system for self-produced power supply phase power supply of the present invention includes a phase power supply power supply generator 1, a phase power supply power supply phase compensator 2, a switching switch 3, a controller 4 and a Voltage regulator 5.

In this embodiment, the phase power supply generator 1 is a Dy11-connected transformer, which is connected to the busbar, and converts the busbar voltage into a phase voltage with a voltage ratio of m.

The phase power supply phase compensator 2 is a Dyn1-connected transformer, which is connected to the phase power supply generator 1 for compensating the phase, and its voltage ratio is n.

In this embodiment, the input end of the phase power supply generator 1 is connected to the bus bar, the output end of the phase power supply generator 1 is connected to the input end of the phase power supply phase compensator 2, and the voltage regulator 5 is connected in series Between the power supply phase compensator 2 and the neutral point of the system, the controller 4 is connected to the voltage transformer of the bus, the output end of the controller 4 is connected to the switching switch 3, and the switching switch 3 is connected in common The point and system neutral are connected to the non-identical terminals on both sides of the voltage regulator 5, and the remaining connection points of the voltage regulator 5 are grounded. The voltage ratio of the voltage regulator 5 is j.

And m*n*j=1.

In this embodiment, the line voltages of the bus power supply are respectively U _AB , U _BC , and U _CA , and the phase voltages of the bus power supply are respectively U _A , U _B , and U _C ; the line voltages output by the phase power generator 1 are respectively are U _ab1 , U _bc1 , and U _ca1 , and the phase voltages are U _a1 , U _b1 , and U _c1 , respectively. According to the principle of transformers, Dy11 connects the transformers of the group, and the secondary side line voltage leads the primary side voltage by 30°, that is, the busbar voltage After being transmitted by the phase power supply generator 1, the busbar voltages U _AB , U _BC , and U _CA are converted into phase voltages U _a1 U _b1 , U _c1 , and the phase angles of U _ab1 , U _bc1 , and U _ca1 lead U _AB , U ca1 respectively. The angle of U _BC and U _CA is 30°, and the voltage ratio of the phase power supply generator (1) is m, so there are

and

The line voltages output by the phase compensator 2 of the phase-recording power supply are U _ab2 , U _bc2 , and U _ca2 , and the phase voltages are U _a2 , U _b2 , and U _c2 respectively. If it lags behind the line voltage of the primary side by 30°, that is, the phase angles of U _ab2 , U _bc2 , and U _ca2 lag behind U _ab1 , U _bc1 , and U _ca1 by 30° respectively, and the voltage ratio of the phase compensator 2 of the phase power supply is n, there are:

According to equations 41, 42, 43, there are:

because:

Substituting Equation 44 into Equation 45, we have:

In this embodiment, the common connection point of the switching switch 3 and the neutral point of the system are connected to the non-identical terminals on both sides of the voltage regulator 5, the voltage ratio of which is j, and m*n*j=1, therefore, the switching switch When a certain phase switch of 3 is closed, the voltages obtained at the neutral point of the system are:

It can be seen that when a single-phase grounding occurs in a phase, and the corresponding phase switch is closed, the neutral point of the system will obtain a voltage equal to the voltage amplitude of the power supply phase of the power grid system and opposite in phase, so that the grounding phase voltage is zero, and the grounding phase voltage is zero. The fault point voltage and current are also zero.

The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the spirit and scope of the technical solutions of the present invention, all of them should be included in the scope of the claims of the present invention. The technology, shape, and structural part that are not described in detail in the present invention are all well-known technologies.

Claims (8)

1. A ground fault current compensation system for self-produced power supply phase power supply, characterized in that it comprises a phase power supply power supply generator (1), a phase power supply power supply phase compensator (2), a switching switch (3), a controller ( 4) and a voltage regulator (5), the input terminal of the phase power supply generator (1) is connected to the bus, and the output terminal of the phase power supply generator (1) is connected to the phase power supply phase compensator (2) The input end of the power supply is connected, the voltage regulator (5) is connected in series between the power supply phase compensator (2) and the neutral point of the system, the controller (4) is connected to the voltage transformer of the bus, and the control The output end of the device (4) is connected with the input end of the switching switch (3). 2 . The ground fault current compensation system of self-produced power supply phase power supply according to claim 1 , wherein the connection form of the phase power supply power supply generator ( 1 ) is Dy or Zy or Yd or Yy. 3 . 3. A ground fault current compensation system for self-produced power supply phase power supply according to claim 1, characterized in that: the connection form of the phase power supply power supply phase compensator (2) is Dyn or Zyn or Yyn. 4 . The ground fault current compensation system of self-produced power supply phase power supply according to claim 1 , wherein the switching switch ( 3 ) is a mechanical switch or a power electronic fast switching switch. 5 . 5. The ground fault current compensation system of a self-produced power supply phase power supply according to claim 1, characterized in that: the common connection point of the switching switch (3) and the system neutral point are connected to the voltage regulator ( 5) Non-identical terminals on both sides, the remaining connection points of the voltage regulator (5) are grounded. 6 . The ground fault current compensation system for self-produced power supply phase power supply according to claim 1 , wherein the controller ( 4 ) comprises a fault judgment module ( 41 ) and a switch control module ( 42 ). 7 . 7. A ground fault current compensation method for self-produced power supply phase power supply, characterized by comprising the following steps: S1: The controller judges whether the single-phase grounding occurs in the system and judges the grounding phase; S2: A ground fault occurs in a certain phase, and the controller (4) controls the switching switch (3) to close the phase switch corresponding to the fault; S3: performing voltage compensation through the voltage regulator (5); S4: When the closing time of the switching switch reaches the set time, the controller controls the switching switch to disconnect; S5: The controller continues to judge whether the single-phase ground fault exists; S6: If the ground fault still exists, go to step 2, and if the single-phase grounding does not exist, the single-phase grounding compensation process ends. 8 . The ground fault current compensation method for a self-produced power supply phase power supply according to claim 7 , wherein the time when the switching switch is turned off set in the step S4 is set according to the line operating conditions. 9 .