CN110544929B - A ground fault current compensation system and method for self-produced power supply 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 compensation transformer, a combination switch, a coupling voltage regulating transformer and a controller. The output end of the combination switch is connected with the input end of the combination switch, the output end of the combination switch is connected to the neutral point, and the coupling voltage regulating transformer is connected in series between the combination switch and the neutral point. The system can passively generate the power supply phase power supply and harmonic phase power supply of the distribution network, and put the reverse phase power supply phase power supply and the 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 disadvantage of using the power electronic device inverter injection method to compensate incompletely after the power is drawn from the bus system. The invention can completely compensate the overvoltage and overcurrent generated by the grounding fault, and completely eliminates the risk of electric shock to the person.

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 treatment method for ground faults in non-effectively grounded systems. The method provides taps on the windings on the side of the transformer system, and reduces faults by short-circuiting the faulty phase winding taps to ground or short-circuiting through impedance. phase voltage to limit 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 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. The neutral point is connected to the faulty phase to suppress the overvoltage of the faulty phase to achieve the purpose of full compensation, which effectively solves the problems of complex current control in the single-phase grounding fault of the power distribution system and the difficulty of complete compensation for metallic grounding. There is a coupling voltage regulating transformer to adjust the voltage of the line power supply in disguised power supply, so as to achieve the purpose of full current and voltage compensation in the event of a ground fault. The present invention has no arc after complete compensation, avoids the risk of personal electric shock, and improves the reliability of power supply and power supply security.

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, comprising a compensation transformer, a combination switch, a coupling voltage regulating transformer and a controller, the input end of the compensation transformer is connected to the busbar, and the output end of the compensation transformer It is connected with the input end of the combination switch, and the output end of the combination switch is connected to the neutral point.

所述耦合调压变压器的电压调节范围为±5％～±50％。Further, the connection groups of the compensation transformers are Dy1 and Dy11. The rated voltage of the primary side of the compensation transformer (1) is the rated voltage U _S of the power grid system, and the rated voltage of the secondary side is 100V to U _S ; the rated voltage of the primary side of the coupling voltage regulating transformer is equal to the rated voltage of the secondary side of the compensation transformer. , the rated voltage of the secondary side of the coupling regulator transformer is

The voltage adjustment range of the coupling voltage regulating transformer is ±5% to ±50%.

Further, the primary side of the compensation transformer is connected to the power grid system bus; the secondary side of the compensation transformer is connected to the combination switch.

Further, the combination switch includes an A-phase split switch, an A-phase ground switch, a B-phase split switch, a B-phase ground switch, a C-phase split switch, and a C-phase ground switch. One end of the A-phase split switch of the combination switch is connected with one end of the A-phase grounding switch to form the A-phase connection point of the combined switch; one end of the B-phase split switch of the combined switch is connected to one end of the B-phase grounding switch, The B-phase connection point of the combination switch is formed; one end of the C-phase split switch of the combination switch is connected with one end of the C-phase grounding switch to form the C-phase connection point of the combination switch; the other end of the A-phase split switch of the combination switch, The other end of the B-phase split switch and the other end of the C-phase split switch are connected together to form the compensation connection point of the combination switch. The other end of the A-phase grounding switch, the other end of the B-phase grounding switch, and the C-phase grounding switch of the combination switch are grounded.

There are two ways to connect the combination switch to the coupling voltage regulating transformer and the neutral point of the system:

The first way:

The compensation connection point of the combination switch is connected to the same name terminal of the primary side of the coupling voltage regulating transformer; the other end of the primary side of the coupling voltage regulating transformer is grounded. The secondary side of the coupling voltage regulating transformer with the same name is connected to the neutral point of the power grid system, and the other end is grounded.

Second way:

The compensation connection point of the combination switch is connected to the same name terminal of the primary side of the coupling voltage regulating transformer; the other end of the primary side of the coupling voltage regulating transformer is grounded. The secondary side of the coupling voltage regulating transformer with the same name is grounded, and the other end is connected to the neutral point of the power grid system.

Further, the control includes a fault judging module and a switch control module. The fault judging module can judge whether a single-phase grounding occurs in the system and judge the grounding phase according to the system bus three-phase voltage, zero-sequence voltage, line zero-sequence current, etc. Since there are relatively mature technologies for ground fault judgment and ground phase judgment, the details will not be described in the present invention. The switch control module controls the closing or opening of each switch of the combination switch.

Further, a method for implementing a single-phase grounding full compensation system is specifically performed according to 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 phase, according to the grounding phase and the combination switch control table, control the corresponding switch of the combination switch to close;

S3: adjust the voltage by coupling the voltage regulating transformer;

S4: When the closing time of the combination switch reaches the set time, the controller controls the combination 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 combination 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.

Further, when the connection mode of the combination switch, the coupling voltage regulating transformer and the neutral point of the system is the first mode, the combination switch control table is shown in Table 1:

Table 1 Combination switch control table is shown in Table 1

When the connection mode of the combination switch, the coupling voltage regulating transformer and the neutral point of the system is the second mode, the control table of the combination switch is shown in Table 2:

Table 2 Combination switch control table 2

The working principle of the present invention is as follows: first, the controller judges the grounding phase of the bus through the voltage transformer. After a certain phase of the bus fails, the controller controls the corresponding switch to close through the combined switch. The reason for the resistance has a certain voltage drop, the coupling voltage regulating transformer adjusts the voltage, and then the inverse voltage is boosted into the neutral point to achieve the purpose of completely compensating for the overvoltage.

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. To achieve the complete compensation purpose of suppressing 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. The grid system can supply power continuously and improve 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 first connection mode of a single-phase grounding full compensation system according to the present invention;

2 is a schematic diagram of a second connection mode of a single-phase grounding full compensation system according to the present invention;

3 is a schematic structural diagram of a combination switch of the present invention;

4 is a schematic structural diagram of the controller of the present invention;

5 is a schematic diagram of a first connection mode phase power supply generation and conversion process of the present invention;

6 is a schematic diagram of the second connection mode phase power supply generation and conversion process of the present invention;

7 is a schematic flow chart of the method of the present invention;

Among them: compensation transformer 1, combination switch 2, coupling voltage regulating transformer 3, controller 4, A-phase splitting switch 21, A-phase grounding switch 22, B-phase splitting switch 23, B-phase grounding switch 24, C-phase Phase splitting switch 25 , C-phase grounding switch 26 , fault judging module 41 , 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 FIG. 1-FIG. 6, a ground fault current compensation system and method for self-produced power supply phase power supply of the present invention:

组合开关(2)与耦合调压变压器(3)及系统中性点的连接方式为第一方式：In this embodiment, FIG. 5 shows the voltage conversion process of the typical embodiment in the first connection mode. The connection group of the compensation transformer (1) is Dy11, and the voltage ratio is k. The voltage ratio of the coupled regulator transformer is

The connection method between the combination switch (2) and the coupling voltage regulating transformer (3) and the neutral point of the system is the first method:

Note that the line voltages of the bus power supply are U _AB , U _BC , and U _CA , and the phase voltages of the bus power supply are U _A , U _B , and U _C respectively; and the line voltages output by the phase power generator (1) are U _ab1 respectively , U _bc1 , U _ca1 , and the phase voltages are U _a1 , U _b1 , and U _c1 , respectively.

According to the basic principles of the three-phase system of the power grid:

After the compensation transformer (1), its output line voltage should be:

又由于耦合调压变压器的电压比为

因此耦合调压器变压器二次绕组输出电压应为Assuming that the A-phase grounding occurs in the system, the table can be obtained. At this time, the A-phase grounding switch and the C-phase splitting switch of the combination switch should be closed. Therefore, the voltage of the primary winding of the input-coupled regulator transformer should be

And because the voltage ratio of the coupling regulator transformer is

Therefore, the output voltage of the secondary winding of the coupled regulator transformer should be

because of

And according to Equation 41:

Therefore, the two have the same amplitude and opposite phase.

组合开关(2)与耦合调压变压器(3)及系统中性点的连接方式为第二方式：FIG. 6 shows the voltage conversion process of the exemplary embodiment in the second connection mode. The connection group of the compensation transformer (1) is Dy11, and the voltage ratio is k. The voltage ratio of the coupled regulator transformer is

The connection mode between the combination switch (2) and the coupling voltage regulating transformer (3) and the neutral point of the system is the second mode:

Note that the line voltages of the bus power supply are U _AB , U _BC , and U _CA , and the phase voltages of the bus power supply are U _A , U _B , and U _C respectively; and the line voltages output by the phase power generator (1) are U _ab1 respectively , U _bc1 , U _ca1 , and the phase voltages are U _a1 , U _b1 , and U _c1 , respectively.

According to the basic principles of the three-phase system of the power grid:

After the compensation transformer (1), its output line voltage should be:

又由于耦合调压变压器的电压比为

且根据其连接方式，其一次绕组电压与二次绕组电压反相，因此耦合调压器变压器二次绕组输出电压应为Assuming that the A-phase grounding occurs in the system, the table can be obtained. At this time, the A-phase splitting switch and the C-phase grounding switch of the combination switch should be closed. Therefore, the voltage of the primary winding of the input-coupled regulator transformer should be

And because the voltage ratio of the coupling regulator transformer is

And according to its connection method, the voltage of its primary winding is opposite to that of the secondary winding, so the output voltage of the secondary winding of the coupled regulator transformer should be

because of

And according to Equation 51:

即两者幅值相同，相位相反。therefore

That is, the two have the same amplitude and opposite phase.

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. The ground fault current compensation system for the self-generated phase power supply is characterized by comprising a compensation transformer (1), a combination switch (2) and a controller (4), wherein the input end of the compensation transformer (1) is connected with a bus, the output end of the compensation transformer (1) is connected with the input end of the combination switch (2), the output end of the combination switch (2) is connected with a neutral point, and the controller (4) is connected with a voltage transformer on the bus;

the compensation transformer (1) is used for directly generating three compensation phase voltages which have the same frequency, the same amplitude and the opposite phase with the phase A, the phase B and the phase C of the power system by using the line voltage of a bus, the controller (4) judges the grounding phase of the bus by using the voltage transformer, and after a certain phase of the bus breaks down, the controller (4) controls the corresponding switch to be closed by using the combination switch (2) so that the compensation phase voltages are connected to a neutral point;

and a coupling voltage regulating transformer (3) is also connected in series between the combination switch (2) and the neutral point, and the coupling voltage regulating transformer (3) is used for solving the problem that the voltage of the compensation phase is reduced due to the internal resistance of the compensation transformer (1) and finely adjusting the voltage of the compensation phase so as to achieve the purpose of completely compensating overvoltage.

2. A ground fault current compensation system for a self-generated phase power supply as claimed in claim 1, wherein: the connection group of the compensation transformer (1) is in the form of Dy1 or Dy 11.

3. A ground fault current compensation system for a self-generated phase power supply as claimed in claim 1, wherein: the combination switch (2) comprises an A-phase-splitting switch (21), an A-phase grounding switch (22), a B-phase-splitting switch (23), a B-phase grounding switch (24), a C-phase-splitting switch (25) and a C-phase grounding switch (26), wherein the A-phase grounding switch (22), the B-phase grounding switch (24) and the C-phase grounding switch (26) are grounded, and the A-phase-splitting switch (21) and the B-phase-splitting switch (23) are connected with the C-phase-splitting switch (25).

4. A ground fault current compensation system for a self-generated phase power supply as claimed in claim 1, wherein: the compensation connection point of the combined switch (2) is connected with the primary side homonymous end of the coupling voltage regulating transformer (3), the other end of the primary side of the coupling voltage regulating transformer (3) is grounded, the secondary side homonymous end of the coupling voltage regulating transformer (3) is connected with a neutral point of a power grid system, and the other end of the secondary side of the coupling voltage regulating transformer is grounded.

5. The system of claim 4, wherein the system further comprises a power supply circuit configured to generate a power supply voltage from the power supply source, wherein the power supply circuit is configured to: the combined switch (2) and the coupling voltage regulating transformer (3) have another connection mode: the compensation connection point of the combined switch (2) is connected with the primary side homonymous end of the coupling voltage regulating transformer (3), the other end of the primary side of the coupling voltage regulating transformer (3) is grounded, the secondary side homonymous end of the coupling voltage regulating transformer (3) is grounded, and the other end of the secondary side is connected with a neutral point of a power grid system.

6. A ground fault current compensation system for a self-generated phase power supply as claimed in claim 1, wherein: the controller (4) comprises a fault judgment module (41) and a switch control module (42).

7. The compensation method of the earth fault current compensation system of the self-generated phase power supply according to any one of claims 1 to 6, comprising the steps of:

s1, judging whether the system generates single-phase grounding or not through the controller (4) and judging a grounding phase;

s2, when a certain phase has ground fault, controlling the corresponding switch of the combined switch (2) to be closed according to the ground phase and the combined switch control table;

s3, adjusting voltage through a coupling voltage-adjusting transformer (3);

s4, when the closing time of the combined switch reaches the set time, the controller (4) controls the combined switch to be switched off;

s5, the controller (4) continuously judges whether the single-phase earth fault exists;

and S6, if the ground fault still exists, jumping to the step 2, and if the single-phase ground does not exist, ending the single-phase ground compensation process.

8. The compensation method of the ground fault current compensation system for self-generating phase power supply according to claim 7, wherein: the setting of the combination switch on time in step S4 is set according to different line conditions.

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