CN207518280U - The three-phase imbalance for having both fault current limitation function administers device - Google Patents

Abstract

The utility model proposes a three-phase unbalance controller with fault current limiting function, which includes: an annular transformer core, three sets of AC coupling coils and a set of auxiliary coils; the three sets of AC coupling coils and auxiliary coils are Wound on the transformer core with the same winding direction; among the three sets of AC coupling coils, any set of AC coupling coils is connected in series to a phase line of the three-phase grid, and any two sets of AC coupling coils are connected to into different phase lines of the three-phase power grid; both ends of the auxiliary winding are connected in parallel with IGBT-based voltage source converters or anti-parallel thyristors, and the transformation ratio of the three sets of AC coupling coils is 1:1:1, and the The transformation ratio between the auxiliary coil and any set of AC coupling coils is 1:k. The utility model can effectively control faults and normal imbalances, and at the same time has a fault current limiting function, and does not affect the operating conditions and safety and stability of the power grid when there is no imbalance or short-circuit fault in the power grid.

Description

Three-phase unbalance controller with fault current limiting function

technical field

The utility model relates to the technical field of electric engineering, in particular to a three-phase unbalance controller with a fault current limiting function, which can control fault/stable unbalance and short-circuit faults.

Background technique

The three-phase unbalance of the power system can be divided into two types: fault unbalance and normal unbalance. Phase-to-phase faults, etc.; normal unbalance refers to the unbalanced conditions that occur when the power grid operates in a steady state.

Fault unbalance usually requires fault protection. Under the background of grid scale development, the short-circuit current level of power grid continues to increase, and the difficulty of fault protection continues to increase. There is an urgent need for a governance method that can effectively limit fault transient unbalance. The normal imbalance is caused by the unbalanced operation of the five links of generation, transmission, transformation, distribution, and utilization. Usually, the symmetry of generators and transformers is better, and the imbalance is mainly caused by the asymmetry of transmission lines and power loads.

The current unbalance controller mainly readjusts and distributes the load through the transfer switch, which cannot quickly respond to the normal unbalance, let alone effectively deal with the fault unbalance and grounding fault. Therefore, there is an urgent need for an unbalance control device that can be used to control faulty and normal unbalances, and can perform fast fault current limitation for various transient faults.

Contents of the invention

Purpose of the invention: In order to solve the technical problem that the existing unbalance controller cannot quickly respond to the normal unbalance, let alone effectively deal with the fault unbalance and grounding fault, the utility model proposes a fault current limiting function The three-phase unbalance controller with fault current limiting function can effectively control the fault and normal imbalance when there is no unbalance and short-circuit fault in the power grid, and at the same time it will not affect the operation of the power grid. conditions and safety and stability.

Technical solution: In order to achieve the above-mentioned technical effects, the utility model proposes the following technical solutions:

A three-phase unbalance controller with a fault current limiting function, including: a ring-shaped transformer core, three sets of AC coupling coils and a set of auxiliary coils; the three sets of AC coupling coils and auxiliary coils are all wound in the same winding direction Wound on the transformer core; among the three sets of AC coupling coils, any set of AC coupling coils is connected in series to the one-phase line of the three-phase grid, and any two sets of AC coupling coils are connected to the different phases of the three-phase grid. In the phase line; both ends of the auxiliary winding are connected in parallel with an IGBT-based voltage source converter or an anti-parallel thyristor; the transformation ratio of the three sets of AC coupling coils is 1:1:1, and the auxiliary coil is connected to any A set of AC coupled coils has a transformation ratio of 1:k.

Further, the two ends of the three sets of AC coupling coils and the auxiliary coil are respectively connected in parallel with a circuit breaker, and the circuit breaker is in the off state when the three-phase unbalance controller is normal, and when the equipment has its own fault or a small current grounding fault when closed.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

The utility model can have no influence on the power flow three-phase balance and line current after being connected to the power grid when the power grid is normal (three-phase balance and no short-circuit fault), and can quickly reduce the three-phase Unbalanced current; when an unbalanced ground fault occurs, the fault current level can be quickly limited; when a balanced ground fault occurs, the fault current level can also be limited. In the present invention, the magnetic circuit constrained three-phase unbalance controller with the fault current limiting function has low operation loss of the whole machine, can realize adaptive control response when the load current is unbalanced, and has fast action speed of unbalance control. At the same time, it can realize the adaptive current limiting response when the fault current occurs, and the action speed of the fault current limiting is fast.

Description of drawings

Fig. 1 is the structural principle diagram of the three-phase unbalance controller with fault current limiting function described in the utility model;

Fig. 2 is the access diagram of the three-phase unbalance controller with fault current limiting function described in the utility model in the three-phase power grid;

Fig. 3 is a functional wiring diagram of the auxiliary winding; Fig. 4 is a three-phase current comparison diagram before and after the three-phase unbalance controller with the fault current limiting function of the present invention is connected to the power grid when there is no unbalanced and short-circuit fault in the power grid;

Fig. 5 is a three-phase current comparison diagram before and after the three-phase unbalance controller with the fault current limiting function of the present invention is connected to the power grid when there is a normal imbalance in the power grid;

Fig. 6 is a partial enlarged view of the three-phase current before and after the three-phase unbalance controller with fault current limiting function described in the present invention is connected to the power grid when there is a normal imbalance in the power grid;

Fig. 7 is a three-phase current diagram before the three-phase unbalance regulator with fault current limiting function described in the present invention is connected to the power grid when a single-phase ground fault occurs in the power grid;

Fig. 8 is a three-phase current diagram after the three-phase unbalance regulator with fault current limiting function according to the present invention is connected to the power grid when a single-phase ground fault occurs in the power grid.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described further.

Fig. 1 shows the structural principle diagram of the three-phase unbalance regulator with fault current limiting function described in the utility model, and Fig. 2 shows the connection of the three-phase unbalance regulator with fault current limiting function The system access diagram of the three-phase power grid; as shown in the figure, the three-phase unbalance controller with fault current limiting function includes: a ring-shaped iron core, and three groups of coupling windings are installed on the iron core. The windings are coupling winding A, coupling winding B and coupling winding C respectively. Coupling winding A is connected to the A-phase line of the power grid, coupling winding B is connected to the B-phase line of the power grid, and coupling winding C is connected to the C-phase line of the power grid. The three sets of coupling windings are wound on the transformer core in the same direction. There is also a set of auxiliary windings installed on the iron core, and the winding direction of the auxiliary windings is consistent with the other three sets of coupling windings; both ends of the auxiliary windings are connected in parallel with IGBT-based voltage source converters or anti-parallel thyristors, and the connection topology is shown in Figure 3 As shown, the auxiliary winding is in the exit state when the fault is unbalanced and the normal is unbalanced, and it is put into operation only when the power grid has a balanced short-circuit fault. To suppress the balanced ground fault in the circuit and compensate for low/overvoltage: when a symmetrical ground fault occurs, the magnetic flux of the transformer core is adjusted by controlling the current in the auxiliary winding, so that an unbalanced magnetic flux is generated in the transformer core, Inductive inductance is then generated to limit the fault current; when low voltage/overvoltage occurs, the magnetic flux of the transformer core is adjusted by adjusting the current in the auxiliary winding, and the compensation voltage is induced in the three sets of AC coupling coils, so that the low voltage or The overvoltage reaches the normal voltage level.

When VSC (voltage source converter based on IGBT) is used to control the auxiliary winding, the auxiliary winding can be directly powered by the three-phase winding, that is, the three-phase winding is used for rectification to provide the DC voltage required by the VSC, or an external independent power supply can be used Provide the DC power required by the VSC; when the anti-parallel thyristor type is used, the auxiliary winding is independent from the three-phase winding, and no external DC power is required.

In the above technical solution, the transformation ratio of the three sets of coupled windings is 1:1:1, which can ensure that the equipment has no unbalanced voltage drop when the power grid is running in a steady state, and does not destroy the original unbalanced state of the power grid. The transformation ratio between the auxiliary winding and any group of coupled windings is 1:k.

Preferably, the two ends of the three sets of coupling windings and one set of auxiliary windings are respectively connected in parallel with bypass switches, and the bypass switches are in the off state when the equipment is normal. The bypass switch is only closed when the equipment itself is faulty and the small current is grounded, and it is used for the protection of the equipment itself and the normal power supply of the non-faulty phase when the small current is grounded.

For the three-phase symmetrical fault, the utility model can realize the fault current limitation of the three-phase symmetrical fault by controlling the magnetic flux of the auxiliary winding. The working principle of the utility model will be further explained through specific examples below.

When a symmetrical fault is detected by unbalance protection/longitudinal differential protection based on traveling wave/wavelet fault identification technology, the current of the auxiliary winding is adjusted to its fixed value through VSC or anti-parallel thyristor, so that the fault current level of the three-phase symmetrical fault is low Due to the interrupting capacity of the circuit breaker, the circuit breaker can normally break the fault current at this time; when the low/overvoltage occurs, when the low/overvoltage is detected, the current of the auxiliary winding is adjusted through the VSC or the anti-parallel thyristor so that the output of the three-phase winding The voltage reaches its rated value, and the treatment of low/overvoltage is completed.

The main electrical parameters of the three-phase unbalance controller are 400V/60kVA, 1% no-load current, 4% short-circuit impedance, 0.025% no-load loss, and 0.014% no-load loss. On the grid side, a 10kV power supply plus a 10kV/400V distribution transformer supplies power to the load. The load is connected in series with a 54-ohm resistance and a 0.063H reactance.

In the normal working condition of the power grid, that is, the three-phase power grid is balanced and there is no short-circuit fault. The three-phase current simulation diagram of the three-phase unbalance controller before it is connected to the grid and when it is connected to the grid is shown in Figure 4. There are three sets of curves in the figure: Ia, Ib, and Ic, which are the A, B, and C phase lines of the three-phase grid respectively The current before and after the middle three-phase unbalance controller is connected to the grid. Among them, the three solid lines are the three-phase current curves before the three-phase unbalance controller is connected to the grid, and the three dotted lines are the three-phase current curves after the three-phase unbalance controller is connected to the grid. It can be seen from the simulation figure that the current peak value of the three-phase unbalance controller before and after connecting to the power grid remains unchanged at 6A, which has no effect on the power flow of the power grid.

When the normal unbalanced condition occurs, take the three-phase unbalanced grid load as a typical scenario, and set the load impedance of phase B to be 10% different from that of phase C, and the load impedance of phase A to be different from phase C by 20% as a typical scenario. The three-phase current simulation diagrams before and after the three-phase unbalance controller is connected to the power grid are shown in Figure 5 and Figure 6. There are three sets of curves in the figure: Ia, Ib, and Ic, respectively for the three-phase power grid A and B , The current before and after the three-phase unbalance controller in the C-phase line is connected to the grid. Among them, the three solid lines are the three-phase current after the three-phase unbalance controller is connected to the grid, and the three dotted lines are the three-phase current before the three-phase unbalance controller is connected to the grid. It can be seen from the simulation diagram that the three-phase current before the three-phase unbalance controller is connected to the power grid is: 6.79A (phase A), 6.04A (phase B), and 5.44A (phase C), and the unbalance degree is : The deviation between phase A and phase B is 12.42%, and the deviation between phase C and phase B is 9.93%. After the three-phase unbalance controller is connected to the power grid, the three-phase currents are: 5.74A (A phase), 6.05A (B phase), 6.42A (C phase), and the unbalance degree is: the deviation between A phase and B phase is 5.12 %, C-phase and B-phase deviation of 6.11%. After the three-phase unbalance controller is connected to the power grid, the three-phase unbalance degree is effectively reduced.

When faulty unbalanced conditions occur, take a single-phase ground fault in the power grid as a typical scenario, set the ground resistance to 0.01Ω, and the ground fault occurs on the C-phase outlet side of the transformer, and the fault time is 50ms. The three-phase current simulation diagrams before and after the three-phase unbalance controller is connected to the power grid are shown in Figure 7 and Figure 8 respectively. In Fig. 7, the dotted line is the A-phase current of the three-phase grid before the three-phase unbalance controller is connected to the grid, and the two solid lines are the B and C phase currents of the three-phase grid before the three-phase unbalance controller is connected to the grid. In Figure 8, the three curves are the A, B, and C phase currents of the three-phase grid after the three-phase unbalance controller is connected to the grid. It can be seen from the figure that when a single-phase ground fault occurs, when the three-phase unbalance controller is not connected to the grid, the peak value of the fault current level of phase C reaches 3.82kA; when the three-phase unbalance controller is connected to the grid, C The peak value of the phase fault current level reaches 18.2A; after the three-phase unbalance controller is connected to the grid, the fault current level when a single-phase ground fault occurs is effectively reduced.

The above is only a preferred embodiment of the utility model, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the utility model, some improvements and modifications can also be made. Retouching should also be regarded as the scope of protection of the present utility model.

Claims (2)

1. The three-phase unbalance controller with fault current limiting function is characterized in that it includes: an annular transformer core, three groups of AC coupling coils and one group of auxiliary coils; the three groups of AC coupling coils and auxiliary coils are all Wound on the transformer core in the same winding direction; among the three sets of AC coupling coils, any set of AC coupling coils is connected in series to a phase line of the three-phase power grid, and any two sets of AC coupling coils are connected to into different phase lines of the three-phase power grid; both ends of the auxiliary winding are connected in parallel with IGBT-based voltage source converters or anti-parallel thyristors; the transformation ratio of the three sets of AC coupling coils is 1:1:1, and the The transformation ratio between the auxiliary coil and any set of AC coupling coils is 1:k. 2. The three-phase unbalance controller with fault current limiting function according to claim 1, characterized in that, the two ends of the three sets of AC coupling coils and the auxiliary coil are respectively connected in parallel with circuit breakers, and the circuit breakers When the three-phase unbalance controller is normal, it is in the open state, and it is closed when the equipment itself fails and a small current grounding fault occurs.