CN220711344U

CN220711344U - Direct-current side soft start protection circuit for APF or SVG

Info

Publication number: CN220711344U
Application number: CN202322027471.9U
Authority: CN
Inventors: 房占凯; 苟家喜; 刘霜; 黄云彪; 杨自清; 龚心周; 陈果
Original assignee: Chongqing Chuanyi Automation Co Ltd
Current assignee: Chongqing Chuanyi Automation Co Ltd
Priority date: 2023-07-31
Filing date: 2023-07-31
Publication date: 2024-04-02
Anticipated expiration: 2033-07-31

Abstract

The utility model discloses a direct-current side soft start protection circuit for an APF or SVG, which comprises a filtering unit and an IGBT power unit, wherein one end of the IGBT power unit is connected with a three-phase power grid through the filtering unit, the other end of the IGBT power unit is provided with a direct-current voltage source unit and a soft start unit which are connected in series, the soft start unit comprises a current limiting resistor, the current limiting resistor is connected with a relay, two pins of a switch end of the relay are connected at two ends of the current limiting resistor in parallel, a coil end of the relay is connected with a driving circuit, the driving circuit comprises a triode, an emitter of the triode is grounded, a collector of the triode is connected with a positive electrode of a power supply through a first resistor, two pins of a coil end of the relay are connected at two ends of the first resistor in parallel, a base of the triode is connected with a control signal end through a second resistor, and the control signal end is used for receiving a control signal of a main control chip, so that the problem of overlarge instant current when the direct-current side of the APF or SVG is started is solved, and the instant current of the direct-current side is effectively reduced.

Description

Direct-current side soft start protection circuit for APF or SVG

Technical Field

The utility model relates to the technical field of filters, in particular to a direct-current side soft start protection circuit for APF or SVG.

Background

The large amount of use of power electronic equipment and nonlinear loads causes a large amount of harmonic waves and reactive power in a power grid, seriously pollutes the quality of electric energy, interferes with the normal operation of the power equipment, and seriously even causes equipment faults and accidents. The Active Power Filter (APF) and the Static Var Generator (SVG) can compensate harmonic waves and reactive power in a power grid, so that the power quality is improved, and soft start modules are required to be arranged in the Active Power Filter (APF) and the Static Var Generator (SVG) to prevent the transient current from being overlarge during starting and damage components in the circuit. At present, soft start modules of APF or SVG circuits are usually arranged on the alternating current side, but the structure needs to be provided with soft start modules for each phase of a three-phase power grid, so that more components are required, the production cost is high, and the fault probability is increased.

Patent document CN210608916U discloses an APF active filter starting circuit, which is formed by respectively arranging soft start resistors and diodes at two ends of a bus capacitor and connecting the soft start resistors and the diodes to an alternating current end to form a loop, so as to prevent the instantaneous current at the moment of power on from being too large and damaging circuit elements. However, the current at two ends of the bus capacitor with the structure is still large, and the protection circuit cannot be well protected, fig. 6 is a simple simulation test chart of the APF active filter starting circuit in the prior art, as shown in fig. 7, the peak value of the impact current at the positive end of the bus capacitor at the direct current side can reach 450A, as shown in the ac current measuring waveform chart of fig. 8, the peak value of the impact current at the alternating current side can reach 600A, therefore, the impact current is large at the moment of starting the circuit in the prior art, the soft starting requirement is difficult to meet, and a direct current side soft starting protection circuit for APF or SVG is needed.

Disclosure of Invention

The utility model aims to overcome the defects of the prior art, provides a direct-current side soft start protection circuit for APF or SVG, solves the problem of overlarge instantaneous current during starting of the direct-current side of the APF or SVG, and effectively reduces the instantaneous current of the direct-current side to achieve the purpose of the protection circuit.

The technical scheme of the utility model is as follows: the utility model provides a direct current side soft start protection circuit for APF or SVG, includes filter unit, IGBT power unit one end passes through filter unit and connects three-phase electric wire netting, and the other end sets up direct current voltage source unit and soft start unit of series connection, soft start unit includes current-limiting resistor, a relay is connected to current-limiting resistor, two pins of relay switch end are parallelly connected at current-limiting resistor both ends, a drive circuit is connected to the coil end of relay, drive circuit includes the triode, the projecting pole ground connection of triode, the collecting electrode of triode passes through first resistance and connects the power anodal, two pins of relay coil end are connected in parallel at first resistance both ends, the base of triode passes through second resistance connection control signal end, control signal end is used for receiving main control chip's control signal.

The direct-current voltage source unit comprises an electrolytic capacitor, wherein the positive electrode of the electrolytic capacitor is connected with the soft start unit, and the negative electrode of the electrolytic capacitor is connected with the IGBT power unit.

The filtering unit comprises three LCL filtering circuits, each LCL filtering circuit comprises a first inductor, a second inductor, a filtering capacitor and a damping resistor, the first inductor and the second inductor are connected in series in a three-phase power grid, the filtering capacitors are connected in series with the damping resistors, one ends of the damping resistors of each LCL filtering circuit are connected with each other, and the other ends of the damping resistors of each LCL filtering circuit are connected with nodes between the first inductor and the second inductor through the filtering capacitors.

The IGBT power unit is of a two-level three-bridge-arm structure and comprises six IGBT switching tubes.

The relay is in a normally open state.

The technical scheme is adopted: a direct current side soft start protection circuit for APF or SVG solves the problem that the circuit is damaged due to overlarge instantaneous current when the direct current side of the APF or SVG is started by arranging the soft start protection circuit on the direct current side of the APF or SVG; in the soft start circuit, two ends of the current limiting resistor are connected with a relay driven by the driving circuit in parallel, so that the instantaneous current of the direct current side is effectively reduced, and components in the circuit are better protected.

The utility model is further described below with reference to the drawings and specific examples.

Drawings

FIG. 1 is a schematic diagram of a circuit structure of the present utility model;

FIG. 2 is a circuit simulation diagram of the present utility model;

FIG. 3 is a schematic diagram of the DC side voltage of the present utility model;

FIG. 4 is a schematic diagram of the DC side current of the present utility model;

FIG. 5 is a schematic diagram of the AC side current of the present utility model;

FIG. 6 is a prior art circuit simulation diagram;

FIG. 7 is a prior art DC side current schematic;

fig. 8 is a prior art ac side current schematic.

Detailed Description

Referring to fig. 1 to 8, a dc side soft start protection circuit for APF or SVG includes a filter unit, an IGBT power unit, a dc voltage source unit, and a soft start unit. The filtering unit comprises three LCL filtering circuits, namely a first LCL filtering circuit, a second LCL filtering circuit and a third LCL filtering circuit, wherein the first LCL filtering circuit comprises a first inductor L1, a second inductor L2, a filtering capacitor C2 and a damping resistor R1, the first inductor L1 and the second inductor L2 are connected in series in a U-phase circuit of a three-phase power grid, the second LCL filtering circuit comprises a first inductor L3, a second inductor L4, a filtering capacitor C3 and a damping resistor R2, the first inductor L3 and the second inductor L4 are connected in series in a V-phase circuit of the three-phase power grid, the third LCL filtering circuit comprises a first inductor L5, a second inductor L6, a filtering capacitor C4 and a damping resistor R3, the first inductor L5 and the second inductor L6 are connected in series in the W-phase circuit of the three-phase power grid, the filtering capacitors of the LCL filtering circuits are connected in series with the damping resistors, one ends of the damping resistors are connected with each other, and the other ends of the damping resistors are connected to nodes between the first inductor and the second inductor through the filtering capacitor. The damping resistor R1, the damping resistor R2 and the damping resistor R3 can absorb resonance peaks well and prevent resonance. The IGBT power unit is of a two-level three-bridge-arm structure and comprises six IGBT switching tubes. One end of the IGBT power unit is connected with a three-phase power grid through a filtering unit, the other end of the IGBT power unit is provided with a direct-current voltage source unit and a soft start unit which are connected in series, the direct-current voltage source unit comprises an electrolytic capacitor C1, the positive electrode of the electrolytic capacitor C1 is connected with the soft start unit, and the negative electrode of the electrolytic capacitor C1 is connected with the IGBT power unit. The direct-current voltage source unit can also use a super capacitor. The soft start unit comprises a current limiting resistor R4, wherein the current limiting resistor R4 is connected with a relay KY1, and the relay KY1 is a normally open relay. The two pins of the switching end of the relay KY1 are connected in parallel to the two ends of the current-limiting resistor R4, the coil end of the relay KY1 is connected with a driving circuit, the driving circuit comprises a triode Q1, the triode Q1 amplifies a control signal to drive the relay KY1, an emitting electrode of the triode Q1 is grounded, a collecting electrode of the triode Q1 is connected with a power supply positive pole VCC through a first resistor R5, the two ends of the first resistor R5 are connected with the two pins of the coil end of the relay KY1 in parallel, a base electrode of the triode Q1 is connected with a control signal end KY_CTL through a second resistor R6, and the control signal end KY_CTL is used for receiving a control signal of a main control chip.

In the embodiment, the control signal is sent by the main control chip in the direct-current side soft start protection circuit of the APF or SVG, and the signal is amplified and converted by the triode Q1 and then drives the relay to act. In the initial stage of power-on and starting of the circuit, a control signal end KY_CTL receives a signal which is low level, a triode is not conducted, a relay KY1 is in an off state, a current limiting resistor R4 plays a role in limiting current, the current at two ends of a direct-current voltage source unit current is reduced, and damage to the direct-current voltage source unit or other components caused by overlarge impact current is prevented. When the voltage of the direct-current voltage source unit rises to about 80% of the rated value, the main control chip sends out a high-level control signal, the triode Q1 is conducted, the relay KY1 acts to bypass the current-limiting resistor R4, and therefore a power-on soft start process is completed.

In this embodiment, the first inductance of the filter unit is 100uH, the second inductance is 1mH, the filter capacitance is 20uF, and the damping resistance is 0.167 Ω. The IGBT power unit is in a three-phase bridge type, and bears the maximum voltage of 1200V, pulse current 450A and direct current 225A. The first resistor R5 of the driving circuit is 10kΩ, the second resistor R6 is 2kΩ, the triode Q1 adopts TIP31C, and the power supply positive pole VCC is 24V. The relay selects a macro-generator relay HF167F140/24-H3F, the maximum switching current 165A and the maximum switching voltage 800V. Simulation test is carried out on the embodiment through SIMULINK software, as shown in FIG. 3, after the circuit of the embodiment is powered on, when the voltage of the direct current side reaches 500V along with time change, the driving circuit drives the relay to be closed, the voltage continues to rise, and the voltage is kept stable when the voltage peak value of the direct current side is 560V; as shown in fig. 4, after the circuit of the embodiment is powered on, the peak value of the current at the direct current side is 55A along with the time change, and compared with 450A in the prior art, the peak value of the impact current is greatly reduced; as shown in fig. 5, the peak value of the corresponding ac side current is about 56A at maximum, while the ac side current of the prior art exceeds 600A, the present embodiment greatly reduces the ac side and dc side impact currents, and achieves the purpose of protecting the circuit components.

The utility model relates to a direct-current side soft start protection circuit for APF or SVG, which solves the problem that the circuit is damaged due to overlarge instantaneous current when the direct-current side of the APF or SVG is started by arranging the soft start protection circuit on the direct-current side; through the cooperation of the relay and the current limiting resistor, the instantaneous current of the direct current side is effectively reduced, and components in the circuit are better protected.

The above description is only of the preferred embodiments of the present utility model and is not intended to limit the utility model, and those skilled in the art will appreciate that the modifications made to the utility model fall within the scope of the utility model without departing from the spirit of the utility model.

Claims

1. The utility model provides a direct current side soft start protection circuit for APF or SVG, includes filter unit, IGBT power unit one end is passed through filter unit and is connected three-phase power grid, and the other end sets up direct current voltage source unit and soft start unit of series connection, its characterized in that: the soft start unit comprises a current limiting resistor (R4), the current limiting resistor (R4) is connected with a relay (KY 1), two pins of a switch end of the relay (KY 1) are connected to two ends of the current limiting resistor (R4) in parallel, a coil end of the relay (KY 1) is connected with a driving circuit, the driving circuit comprises a triode (Q1), an emitting electrode of the triode (Q1) is grounded, a collecting electrode of the triode (Q1) is connected with a power supply positive electrode (VCC) through a first resistor (R5), two pins of a coil end of the relay (KY 1) are connected to two ends of the first resistor (R5) in parallel, a base electrode of the triode (Q1) is connected with a control signal end (KY_CTL) through a second resistor (R6), and the control signal end (KY_CTL) is used for receiving a control signal of a main control chip.

2. The dc-side soft start protection circuit for APF or SVG of claim 1, wherein: the direct-current voltage source unit comprises an electrolytic capacitor (C1), wherein the positive electrode of the electrolytic capacitor (C1) is connected with the soft start unit, and the negative electrode of the electrolytic capacitor is connected with the IGBT power unit.

3. The dc-side soft start protection circuit for APF or SVG of claim 1, wherein: the filtering unit comprises three LCL filtering circuits, each LCL filtering circuit comprises a first inductor, a second inductor, a filtering capacitor and a damping resistor, the first inductor and the second inductor are connected in series in a three-phase power grid, the filtering capacitors are connected in series with the damping resistors, one ends of the damping resistors of each LCL filtering circuit are connected with each other, and the other ends of the damping resistors of each LCL filtering circuit are connected with nodes between the first inductor and the second inductor through the filtering capacitors.

4. The dc-side soft start protection circuit for APF or SVG of claim 1, wherein: the IGBT power unit is of a two-level three-bridge-arm structure and comprises six IGBT switching tubes.

5. The dc-side soft start protection circuit for APF or SVG of claim 1, wherein: the relay (KY 1) is a normally open relay.