CN205622497U - Electric -power active filter's direct current protection circuit - Google Patents

Abstract

The utility model discloses an electric -power active filter's direct current protection circuit, including the discharge protection return circuit that prevents the too high damage of direct current busbar voltage IPM and shut down in the system, the outage back, exoelectric outage lets out can the return circuit to direct current energy -storage capacitor, the discharge protection return circuit sets up at the direct current electric capacity C7 both ends that link to each other with positive and negative dc bus, including discharge resistance R7, discharge switch Q7, detection module and control module, connect in parallel at direct current electric capacity C7 both ends behind discharge resistance and the discharge switch polyphone, the voltage that detection module detected direct current electric capacity C7 both ends links to each other with control module, and control module judges that the voltage of detection module output produces control signal control when being greater than the setting value the discharge switch closed, the outage is let out and can the return circuit be let out can resistance R9 including connecting in parallel in the outage at direct current electric capacity C7 both ends, and the outage is let out and to be more than discharge resistance R7 by resistance R9. The discharge protection return circuit switches on and discharges when direct current busbar voltage is higher than the setting value, lets out through the outage after switching on and shutting down and to let out the ability in the return circuit.

Description

A kind of DC protection circuit of active power filter

Technical field

This utility model relates to active power filter field, particularly to a kind of DC protection circuit protected, in active power filter, the DC capacitor being connected on dc bus.

Background technology

Active power filter (APF:Active power filter) is a kind of for dynamic harmonic wave, the novel electric power electric device of compensating reactive power, it can carry out quick tracing compensation to the harmonic wave of different size and frequency, the most active, it is relative to passive LC filter, can only be for the harmonic wave of Passive intake fixed frequency and size, APF can be by sampling load current carry out each harmonic and idle separation, control and actively export the size of electric current, frequency and phase place, and quickly respond, phase induced current in payment load, achieve dynamic tracking to compensate, and not only can mend harmonic wave but also mend idle and uneven.

Active filter compares with passive filter, and regulation effect is good, mainly can filter repeatedly and higher hamonic wave simultaneously, will not cause resonance, but price is relatively high.Current active filter is all based on low pressure, high voltage active wave filter technology is the most ripe, but actual application safety coefficient is the lowest, international common practice is with transformer boost, ensure reliability, national correlation department also requires that the form with transformer boost and active filter combine, and administers high pressure harmonic wave.

The principle of active filter: Active Power Filter-APF detects load current by current transformer, and calculated by internal DSP, extract the harmonic components in load current, then it is sent to internal IGBT by pwm signal, control inverter generation one and load harmonic current is equal in magnitude, harmonic current injection in opposite direction, in electrical network, reaches the purpose of filtering.

DC bus-bar voltage U_dCross and can damage IPM by height, it addition, after system-down, power-off, for security consideration, the energy of DC energy storage electric capacity must be released complete within the time of regulation.

Summary of the invention

The purpose of this utility model is to provide a kind of DC protection circuit, protects DC energy storage electric capacity.

This utility model be employed technical scheme comprise that the DC protection circuit of a kind of active power filter by realizing its goal of the invention, including preventing DC bus-bar voltage U_dThe discharge prevention loop of too high damage IPM and after system closedown, power-off, the power-off of DC energy storage electric capacity electric discharge is let out can loop, described discharge prevention loop is arranged on the DC capacitor C7 two ends being connected with positive and negative dc bus；Including discharge resistance R7, discharge switch Q7, detection module and control module, it is connected in parallel on DC capacitor C7 two ends after described discharge resistance and discharge switch series winding, the voltage at the described DC capacitor C7 two ends described in detection module detection is connected with described control module, and described control module determines the voltage of detection module output more than the discharge switch Guan Bi produced during setting value described in control signal control；Described power-off let out can loop include being connected in parallel on the power-off at DC capacitor C7 two ends let out can resistance R9, described power-off let out can resistance R9 much larger than discharge resistance R7.

The discharge prevention loop conducting electric discharge when DC bus-bar voltage is higher than setting value, is let out can be let out energy in loop by power-off after switching on and shutting down.

Further, in the DC protection circuit of above-mentioned active power filter: described discharge switch Q7 is discharge IGBT, the source terminal of discharge IGBT connects the anode of DC capacitor C7 by discharge resistance R7, the negative electrode of the drain electrode termination DC capacitor C7 of discharge IGBT.

Further, in the DC protection circuit of above-mentioned active power filter: also include the drive circuit being driven described discharge IGBT, described drive circuit includes audion Q1, audion Q2 and audion Q3；Described control module connects the base stage of audion Q1 by isolation optocoupler U1, and the colelctor electrode of audion Q1 connects high level, the grounded emitter of audion Q1 by collector resistance R2；The colelctor electrode of audion Q1 base stage with audion Q2 and audion Q3 respectively is connected, and the colelctor electrode of audion Q2 connects high level, and the emitter stage of audion Q2 connects the colelctor electrode of audion Q3, the grounded emitter of audion Q3；The colelctor electrode junction of the emitter stage of audion Q2 and audion Q3 connects the grid of discharge IGBT.

Below with reference to drawings and Examples, this utility model is described in detail.

Accompanying drawing explanation

Fig. 1 is this utility model basic circuit diagram.

Fig. 2 is this utility model IGBT drive circuit schematic diagram.

Detailed description of the invention

The present embodiment is in a kind of active power filter, the circuit of direct current protecting, as it is shown in figure 1, include two parts, and first discharge prevention loop, prevent DC bus-bar voltage U_dToo high damage IPM, its two be powered off letting out can loop, after system closedown, power-off, DC energy storage electric capacity discharges.

Utilize a voltage detection module to dc bus discharge prevention loop to U_dDetecting in real time, have a detection resistance R8 in detection module, the voltage at DC capacitor C7 two ends is namely detected, works as U by voltage detecting in real time_d>=800V, it is an IGBT that control module controls to open electric discharge Q7, Q7, makes electric capacity C7 be discharged by discharge resistance R7；Work as U_d≤ 700V, control module controls to turn off discharge IGBT.The rated current of discharge IGBT is taken as I_C=150A, rated voltage U_CES=1200V, then initial drain I_C=150A, discharge resistance is calculated as follows:

$R=\frac{U_d}{I}=\frac{800}{150}=5.33\mathrm{\Ω}$

Reality takes R=6 Ω.

RC circuit meets below equation:

$u_c=U_0{e}^{\frac{-1}{RC}t}$

Wherein, initial voltage U_o=800V, u_c=700V, C=20mF, R=6 Ω, can solve t=16ms.

Therefore, R7 value is the least, discharges the fastest, and instant discharge current is the biggest, and the cooling requirements of discharge resistance and IGBT electric current quota will improve accordingly, thus cause cost increase.Choosing of R7 value needs factor of both compromise consideration t and discharge current I discharge time.R=6 Ω in reality, uses special electric motor starting resistance.

Real system direct-current discharge uses IGBT, and its rated current, voltage are respectively 300A, 1200V.Owing to this circuit is the highest to performance requirements such as the loss of IGBT, switching speeds, type selecting is to be relatively easy to.The drive circuit figure of IGBT is as shown in Figure 2.This drive circuit is made up of audion Q1, audion Q2 and audion Q3, first the base stage of audion Q1 receives, by isolation optocoupler U1, the control signal produced by control module, then IGBT is driven by the push-pull circuit by being made up of audion Q2 and audion Q3, additionally, audion in putting into practice circuit, it is generally required to have base resistance, collector resistance and emitter resistance etc. such as resistance R1, resistance R2 and resistance R3, also has some parasitic capacitances such as electric capacity C1, electric capacity C2.

After system-down, power-off, for security consideration, the energy of DC energy storage electric capacity must be released complete within the time of regulation.Therefore, having a power-off to let out energy loop and be arranged on the two ends of DC capacitor C7, it is a resistance R9 being connected in parallel on electric capacity C7 two ends.For the zero input response of RC firstorder circuit, engineering be it is generally acknowledged and i.e. come to an end through (3 τ～5 τ) time transient process, it is assumed that t=120s discharge time of native system, then have

3 τ=3RC=t

Wherein, C=20mF, t=120s, R=2k Ω can be solved.The power of resistance consumption is

$P=\frac{U_d^2}{R}=\frac{{750}^2}{2\×{10}^3}=281.6W$

Obviously, reduce R9 and can accelerate discharge process, convenient debugging, but loss can rise.In order to reduce resistance heating and loss, using a 10k Ω in reality, the resistance of 1kW is fixed in device.But in order to debug conveniently, can outside device a 2k Ω in parallel again, the resistance of 1kW, to accelerate the velocity of discharge.Final value needs to consider of both discharge time and loss and affects.Therefore, R9 should be much larger than R7.

Claims (3)

1. a DC protection circuit for active power filter, including preventing the discharge prevention loop of DC bus-bar voltage too high damage IPM and after system closedown, power-off, energy loop is let out in the power-off to the electric discharge of DC energy storage electric capacity, it is characterised in that:

Described discharge prevention loop is arranged on the DC capacitor C7 two ends being connected with positive and negative dc bus；Including discharge resistance R7, discharge switch Q7, detection module and control module, it is connected in parallel on DC capacitor C7 two ends after described discharge resistance and discharge switch series winding, the voltage at the described DC capacitor C7 two ends described in detection module detection is connected with described control module, and described control module determines the voltage of detection module output more than the discharge switch Guan Bi produced during setting value described in control signal control；

Described power-off let out can loop include being connected in parallel on the power-off at DC capacitor C7 two ends let out can resistance R9, described power-off let out can resistance R9 much larger than discharge resistance R7.

The DC protection circuit of active power filter the most according to claim 1; it is characterized in that: described discharge switch Q7 is discharge IGBT; the source terminal of discharge IGBT connects the anode of DC capacitor C7 by discharge resistance R7, the negative electrode of the drain electrode termination DC capacitor C7 of discharge IGBT.

The DC protection circuit of active power filter the most according to claim 2, it is characterised in that: also including the drive circuit being driven described discharge IGBT, described drive circuit includes audion Q1, audion Q2 and audion Q3；

Described control module connects the base stage of audion Q1 by isolation optocoupler U1, and the colelctor electrode of audion Q1 connects high level, the grounded emitter of audion Q1 by collector resistance R2；The colelctor electrode of audion Q1 base stage with audion Q2 and audion Q3 respectively is connected, and the colelctor electrode of audion Q2 connects high level, and the emitter stage of audion Q2 connects the colelctor electrode of audion Q3, the grounded emitter of audion Q3；The colelctor electrode junction of the emitter stage of audion Q2 and audion Q3 connects the grid of discharge IGBT.