CN105977947A - Power distribution network active arc extinction device and current control method thereof - Google Patents

Abstract

The present invention discloses a power distribution network active arc extinction device and a current control method thereof. The device is configured to inject power current into the neutral point of a power distribution network to reach the purpose of earth fault arc extinguishing. The amplitude and the phase of the injection current may be obtained through the injection of special current into the neutral point twice and through combination of corresponding calculation methods. An injection current controller is formed by a proportion resonance controller, modulation signals are obtained by using injection current deviation signals through the proportion resonance controller, an inverter switch tube is driven after the modulation signals are subjected to triangle carrier modulation to generate inversion current, and the inversion current is outputted to the neutral point of the power distribution network after passing through a filtering circuit. The power distribution network active arc extinction device is fast in response speed, high in sensitivity and low in cost, and is able to realize rapid and reliable arc extinguishing of instant earth faults.

Description

A kind of active arc-extinction device of power distribution network and current control method thereof

Technical field

The invention belongs to Relay Protection Technology in Power System field, have particularly to a kind of power distribution network Source arc-extinction device and current control method thereof.

Background technology

Power system is a complication system non-linear, large-scale, and power distribution network gos deep into user eventually End, running environment is changeable, and it is that instantaneity connects that random fault, the fault of the most about 70% easily occur Earth fault.There is electric capacity and bleeder resistance over the ground due to power distribution network, therefore earth-fault current is Capacitance current and resistive leakage current.For limiting earth-fault current, China's power distribution network is typically adopted With isolated neutral, through the neutral non-effective grounding such as grounding through arc, resistance grounded The method of operation.Along with urban and rural power grids develop, capacitance current increases, instantaneity earth fault extinguishing arc Less able, the electric arc of trouble point is difficult to self-extinguish, is easily generated fault overvoltage, causes many Weight accident, even causes large-area power-cuts, jeopardizes power grid security, affect social stability.

Affect earth fault extinguishing arc because have: fault current, indirect arc overvoltage (include Recovery initial velocity, recovery time and the amplitude of faulted phase voltage).Fault current is the least, medium Damage the least, be more conducive to fault extinguishing arc；The recovery initial velocity of faulted phase voltage is the slowest, recovery Time is the longest, amplitude is the least, is more difficult to again puncture dielectric, stops arc reignition, more has It is beneficial to fault extinguishing arc.

Current power distribution network fault extinguishing arc typically uses post-set arc suppression coils device to realize, this dress Put and carry out condenser current compensation by regulation arc suppression coil contact with dynamically change access capacity, It is difficult to meet the requirement of fast and reliable blow-out at the aspect such as degree of regulation and response speed.Therefore, Realize extinguishing arc purpose the most fast and accurately, ensure that power distribution network safely and steadily runs, become urgently A difficult problem to be solved.

Summary of the invention

For solving technical problem present in above-mentioned power distribution network arc extinguishing method, the present invention proposes A kind of active arc-extinction device of power distribution network, which solves distribution net work earthing fault electric current and quickly may be used A difficult problem by suppression.When distribution net work earthing fault occurs, rapidly to neutral point injection current, Forcing fault point voltage is zero, it is achieved the reliable extinguishing arc of transient fault.Its topology diagram such as Fig. 1 Shown in.

The technical solution adopted for the present invention to solve the technical problems includes following several step:

1) measure power distribution network three-phase voltage and neutral point voltage, it is judged that earth fault occur with No；

2) when judging that earth fault occurs, by the active arc-extinction device of power distribution network in power distribution network Property point injects two primary currents, to determine the reference current carrying out fault current compensation；

3) by the difference warp of active for power distribution network arc-extinction device actual output current Yu reference current Ratio resonant controller produces modulating wave, controls inverter switching device by triangular modulation method The break-make of pipe is with to power distribution network injection current, and pressure fault point voltage and earth-fault current are Zero.

In view of at resonant frequency, the gain of ratio resonant controller is infinitely-great, and During disresonance frequence, gain declines substantially, and in reality, the parameter of components and parts can not accurately be surveyed The precision restriction of amount and digitial controller, the gain at resonant frequency can not reach infinite Greatly.So when design proportion resonant controller actual resonance frequency to be considered and ideal resonant Deviation, the above analysis takes transmission function and is:

$G\left(s\right)=k_p+\frac{2k_r{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}^2}---\left(1\right)$

K in formula_pAnd k_rBeing respectively proportionality coefficient and resonance coefficient, ratio resonant controller is transmitted Function schematic diagram is as shown in Figure 2.Output current deviation value obtains after ratio resonant controller Modulating wave U_r, as shown in formula

$U_r=(k_p+\frac{2k_r{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}^2})(I^{*}-I)---\left(2\right)$

Wherein I^*For injecting the reference current of neutral point, I is neutral point actual current, is obtaining After modulating wave, it is compared generation inverter switching device pipe driving pulse afterwards, with control with triangular carrier It is shaped with source arc-extinction device to power network neutral point injection current.

In order to obtain injection current reference value, the present invention proposes the reference electricity of twice injection current Stream generating method, injects amplitude by twice different, and the electric current that phase place is identical determines with reference to electricity Stream.

For the power distribution network shown in Fig. 1, it is assumed that singlephase earth fault occurs in C phase, by base You understand by hoff's law

$\begin{array}{c}{I}_i=E_A(\frac{1}{r_A}+{\mathrm{j\ωC}}_A)+E_B(\frac{1}{r_B}+{\mathrm{j\ωC}}_B)+E_C(\frac{1}{r_C}+\frac{1}{R_f}+{\mathrm{j\ωC}}_C)\\ +U_N\[\frac{1}{r_A}+\frac{1}{r_B}+\frac{1}{r_C}+\frac{1}{R_f}+j\mathrm{\ω}(C_A+C_B+C_C)\]\end{array}---\left(3\right)$

Establishing electrical network three-phase voltage and over the ground parameter are the most symmetrical, then have

$I_i=\frac{E_C}{R_f}+U_N(\frac{3}{r_C}+\frac{1}{R_f}+j3{\mathrm{\ωC}}_C)---\left(4\right)$

Assume fault point voltage U_C=0, injected value of current now is reference current, this electricity Stream is represented by

$I_i^{*}=-E_C(\frac{3}{r_C}+j3{\mathrm{\ωC}}_C)---\left(5\right)$

Assume in formula (4),

$\left\{\begin{array}{c}{Y}_1=\frac{3}{r_C}+\frac{1}{R_f}+j3{\mathrm{\ωC}}_C\\ Y_2=\frac{1}{R_f}\end{array}\right.---\left(6\right)$

Then formula (4) is represented by

I_i=U_NY₁+E_CY₂ (7)

At twice that phase place is identical, that amplitude is different power current I_i1、I_i2Inject neutral point, point Do not measure corresponding neutral point voltage U_N1、U_N2。I_i1Capacitance current knot when being installed by device Box-like (5) determine；I_i2It is taken as I_i170%, by I_i1And I_i2Substitution formula (7), is calculated

$\left\{\begin{array}{c}{Y}_1=\frac{{\mathrm{\ΔI}}_i}{{\mathrm{\ΔU}}_N}\\ Y_2=\frac{U_{N1}{I}_{i2}-U_{N2}{I}_{i1}}{{\mathrm{\ΔU}}_N{E}_C}\end{array}\right.---\left(8\right)$

Convolution (5), formula (6) and formula (8) can obtain:

$I_i^{*}=-E_C(Y_1-Y_2)=\frac{I_{i2}{U}_{N1}-I_{i1}{U}_{N2}-{\mathrm{\ΔI}}_i{E}_C}{{\mathrm{\ΔU}}_N}---\left(9\right)$

Wherein △ I_i=I_i1-I_i2, △ U_N=U_N1-U_N2。

The solution have the advantages that:

(1) this device fast response time, highly sensitive, cost is low, it is possible to achieve instantaneous connect Earth fault arc extinguishing quick, reliable；

(2) reference current generates method only needs to inject two primary currents to neutral point, it is not necessary to measure Power distribution network parameter over the ground, has simplicity, rapid, the feature of strong operability；

(3) the ratio resonant controller used can make up output electric current actual frequency and control The stable state accuracy problem on the low side that deviation between device resonant frequency processed causes, it is ensured that output electric current Control accuracy.

The present invention is further illustrated below in conjunction with the accompanying drawings.

Accompanying drawing explanation

Fig. 1 is power distribution network active arc-extinction device topology diagram；

Fig. 2 is that ratio resonance controls schematic diagram；

Fig. 3 is power distribution network active arc-extinction device program flow chart.

Neutral point voltage and injection current oscillogram when Fig. 4 is first time injection current；

Neutral point voltage and injection current oscillogram when Fig. 5 is second time injection current；；

Fig. 6 is reference current and neutral point sample rate current oscillogram；

Fig. 7 is that faulted phase voltage emulates dynamic waveform figure；

Fig. 8 is that fault current emulates dynamic waveform figure.

Detailed description of the invention

Power distribution network active arc-extinction device software flow pattern is as shown in Figure 3.Measure distribution the most continuously Net three-phase voltage and residual voltage, when residual voltage is more than 15% phase voltage, it is judged that earth fault Occur, compare three-phase voltage size, it is judged that voltage low phase is fault phase, and measures fault phase Voltage；By active arc-extinction device to power network neutral point injection current I_i1, measure neutral point electricity The amplitude of pressure and phase place, to power network neutral point injection current I after time delay 1s_i2, again measure Neutral point voltage, and obtain optimum reference current by relational expression (3)；By reference current and adopting Modulated signal is obtained through ratio resonant controller by the difference of electric current, then after comparing with triangular carrier Obtaining IGBT driving pulse, the break-make controlling IGBT produces inverter current；Inverter current warp Inject power network neutral point by injection transformer after filter circuit filtering, suppress fault point voltage To zero, reach the purpose of extinguishing arc.

In order to verify the active arc-extinction device of power distribution network described in the invention and current control method thereof Effectiveness, PSIM9.0 simulation software has been built twice injection current phantom, its Simulation result is as shown in Figure 6 to 8.From dynamic waveform it can be seen that control system is to fault The response speed of point voltage quickly, is found by observation, this system for fault point voltage and The adjustment time of fault current is about 1ms, is far smaller than post-set arc suppression coils up to 3～5 The response time of individual cycle.From Fig. 7 Yu Fig. 8 it can be seen that after putting into active arc-extinction device, Fault point voltage U_CSize is suppressed to 3.7V, fault current I by 214V_fSize is by 21.3A Being reduced to 0.68A, extinguishing arc effect is obvious, demonstrates the effective of the carried principle of the present invention and method Property.

Claims (3)

1. the active arc-extinction device of power distribution network, including uncontrollable commutator, inverter, control Circuit, filter circuit, injection transformer.It is characterized in that: described uncontrollable commutator is connected to Grounding transformer secondary, provides galvanic current pressure for inverter；Described inverter is by controlling Circuit provides driving pulse, produces specific power current, by note after filtered circuit filtering Enter transformator and inject power network neutral point, thus suppress fault point voltage, it is achieved the purpose of extinguishing arc.

The reference value of injection current the most according to claim 1, by twice injection current Method obtain, it mainly comprises the following steps: by the active extinguishing arc of the power distribution network described in claim 1 Device is at twice by power current I_i1、I_i2Inject neutral point, measure corresponding neutral point electricity respectively Pressure U_N1、U_N2, in conjunction with faulted phase voltage E, pass through relational expression

I^*=(I_i2U_N1-I_i1U_N2-ΔI_iE)/ΔU_NObtain with reference to output electric current.

Twice injection current the most according to claim 2, it is characterised in that: twice injection Electric current is power frequency, and phase angle is identical, and amplitude is different.The current value injected for the first time is according to being Uniting parameter determination over the ground, the amplitude of injection current is the 70% of injection current for the first time for the second time.