CN104345218A - Reactance value measurement system and method for three-phase reactor - Google Patents

Abstract

The invention discloses a reactance value measurement system for a three-phase reactor. The reactance value measurement system comprises the processes as follows: a direct current side of a three-phase inverter power supply unit provides a direct current power supply to an inverter by rectification of the system or by virtue of a storage battery; output of an alternating current side is respectively connected with one end of a to-be-tested three-phase reactor after passing through a low-pass filter composed of an RC; the other end of the to-be-tested three-phase reactor is connected with a neutral point of the system; a three-phase electric signal detection unit is respectively connected to a three-phase inverter power supply unit in series and is output to three-phase phase lines of the to-be-tested three-phase reactor; collected current signals are respectively output to a first wiring terminal of a calculation control unit; the composition and connection relationships of the calculation control unit are as follows: the calculation control unit comprises the first wiring terminal, a conditioning circuit, an A/D part, a CPLD (Complex Programmable Logic Device), a dual-port RAM and a DSP (Digital Signal Processing) part, which are sequentially connected with one another; the CPLD is also externally connected with a PWM (Pulse-Width Modulation) transmission circuit and an input and output circuit respectively; the PWM transmission circuit and the input and output circuit are externally linked through a second wiring terminal. The reactance value measurement system has the advantages of being compact in structure, advanced in function, high in test efficiency, convenient for field use, accuracy in measurement, and small in measurement error.

Description

Three-phase reactor reactance value measuring system and method

Technical field

The present invention relates to a kind of three-phase reactor reactance value measuring system.The invention still further relates to the method adopting described system to carry out the measurement of three-phase reactor reactance value.

Background technology

Reactor is a kind of conventional, important power equipment in electrical network, is widely used in the aspects such as reactive-load compensation, current limliting, current stabilization (flat ripple), filtering, damping, phase shift in circuit.GB/T 1094.6-2011 " power transformer the 6th part: reactor " lists the measurement of reactor reactance value in delivery test project; To the reactor put into operation, its reactance value measurement judges that it normally runs no important indicator, lists preventive trial project in; And according to national Specification, to iron core reactor reactance measurement should to be greater than under 90% rated current just effective.

Traditional three-phase reactor reactance value measurement mechanism, is made up of generator, pressure regulator, compensation condenser group, current transformer, voltage transformer (VT), voltage table, reometer, stube cable and mating fastener.There is the shortcoming large, structure is scattered, cost is high that takes up room in such device, can only for the manufacture of factory or professional test mechanism; At present, to the reactor come into operation, almost reactance measurement cannot be completed.

Further, traditional three-phase reactor reactance value measurement is based on three-phase symmetric voltage source metering system, itself there is following defect: (1) inductance measurement result is relevant with the internal resistance of source, and different inner walkway results is different, therefore there is systematic error; (2) be difficult to accomplish that the value of three-phase current is more close, three-phase current varies in size and affects alternate induced voltage by mutual inductance, thus affects measurement result, about current deviation no standard; (3) even if can accomplish that three-phase electricity flow valuve is equal, but three-phase current may not be symmetrical, still affects alternate induced voltage, causes measuring and forbidden.

Summary of the invention

First technical matters to be solved by this invention, proposes a kind of three-phase reactor reactance value measuring system exactly.

Second technical matters to be solved by this invention, proposes a kind of measuring method adopting described system to carry out three-phase reactor reactance value exactly.

The feature that system of the present invention has compact conformation, function is advanced, test efficiency is high, facilitate onsite application, and the reactance value measuring method adopting described system to carry out three-phase reactor to measure accurate error little.

Solve above-mentioned first technical matters, the technical solution used in the present invention is:

A reactance value measuring system for three-phase reactor, is characterized in that: comprise three phase inverter unit, three-phase electricity detecting signal unit and calculation control unit;

The DC side of described three phase inverter unit connects tested three-phase reactor one end respectively through the output of rectification or the direct supply provided for inverter with accumulator, AC for system after the low-pass filter that RC forms; Tested three-phase reactor other end welding system neutral point;

Described three-phase electricity detecting signal unit be connected on respectively three phase inverter unit export to connect tested three-phase reactor triple-phase line on, its current signal gathered exports the first connection terminal of calculation control unit respectively to;

The composition of described calculation control unit with annexation is: the first connection terminal be connected successively, modulate circuit, A/D, CPLD (Complex Programable Logic Device), dual port RAM and DSP (Digital Signal Processing), described CPLD also distinguishes external PWM transmission circuit and input and output circuit, and described PWM transmission circuit and input and output circuit are outreached by the second connection terminal.

The low-pass filter of described RC composition is resistance and the electric capacity of series connection, and the Hall voltage sensor in parallel at electric capacity two ends, it exports u _a, u _b, u _c.

Described three phase inverter unit adopts 3 single-phase inverters composition, and three phase inverter unit adopts PWM (width modulation) technology, the frequency of PWM at 2 ~ 12kHz, instruction cycle 40us, device sine wave output frequency range is 0.5 ~ 50Hz;

Described three-phase electricity detecting signal unit adopts Hall current sensor to measure three-phase current i _a, i _b, i _c, adopt RC filtering circuit (see Fig. 3 modulate circuit) and Hall voltage sensor measurement three-phase voltage u _a, u _b, u _c;

Described calculation control unit CPU adopts TI company floating point DSP chip TMS320C6713, and core frequency can reach 225MHz.Logic chip adopts CPLD, controls outside 8 passage 14 AD, and sends PWM instruction.Controller inside possesses the On-off signal output module of some, for controlling external communication contactor.

Solve above-mentioned second technical matters, the technical solution used in the present invention is:

Adopt described system to carry out a method for three-phase reactor reactance value measurement, comprise the following steps:

The first step, calculates according to the volumeter of the inductance ratings value of tested three-phase reactor, rated current and native system the maximum frequency that native system can bear;

Second step, calculates according to native system output frequency the sampled voltage phase shift and amplitude coefficient that RC wave filter causes, and instead pushes away voltage over zero;

3rd step, finds voltage over zero according to detection magnitude of voltage, and sets up sin ω t and cos ω t;

In formula, ω is power supply angular frequency; T is the time;

4th step, calculates the meritorious of output current and reactive current according to sin ω t and cos ω t:

$I_{M1}=\frac{2}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{i}_k\sin \left(k\right);$

$I_{M2}=\frac{2}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{i}_k\cos \left(k\right);$

In formula, I _m1, I _m2be respectively active current, peak value of idle current; N is a cycle discrete point number; i _kit is the electric current discrete signal detected; Sin (k), cos (k) are the discrete magnitude of sin ω t and cos ω t respectively;

5th step, calculates the inductance value of reactor according to voltage and reactive current:

$L=\frac{U_M}{\mathrm{\ω}{I}_{M2}}$

Capacity formula due to three-phase reactor is P _n=3 ω L _ni ²namely the capacity of reactor is directly proportional to the frequency applying electric current, and therefore under same test current, reducing ω can effectively reduce capacity of experiment, also just can reduce required testing equipment capacity.

So thinking of the present invention is that the frequency by reducing to measure power supply reaches reduction measuring equipment capacity problem, meets in-site measurement requirement; The current source of making three-phase controlled frequency, controlled current flow substitutes three-phase voltage source to improve the accuracy of three pole reactor measurement.

The present invention compared with prior art has following advantage:

1, the sine wave freuqency scope that system of the present invention exports is 0.5 ~ 50Hz, and the capacity formula of three-phase reactor is P _n=3 ω L _ni ²therefore, under same test current, reduce required testing equipment capacity can be effectively reduced.

2, three phase inverter unit of the present invention adopts current tracking PWM technology, the three-phase electricity flow valuve exported is symmetrical and equal, eliminates the adverse effect of current deviation to mutual voltage, improves accuracy of measurement, eliminate the impact of the internal resistance of source, measurement result does not have Systematic Errors.

Accompanying drawing explanation

Fig. 1 a is one of structural representation of the present invention (wiring diagram);

Fig. 1 b is structural representation two (three-phase inverting circuit) of the present invention;

Fig. 2 is the wiring schematic diagram of three-phase electricity detecting signal unit;

Fig. 3 is calculation control unit composition and annexation schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

Participate in 4 years Fig. 1-Fig. 3, the reactance value measuring system embodiment of three-phase reactor of the present invention, comprises three phase inverter unit, three-phase electricity detecting signal unit and calculation control unit.

Three phase inverter unit DC side connects tested three-phase reactor one end respectively, tested three-phase reactor other end welding system neutral point for system after the low-pass filter (the external connecting circuit of A, B, C of Fig. 1 a) that the output of rectification or the direct supply provided for inverter with accumulator, AC forms through RC; Three-phase electricity detecting signal unit be connected on respectively three phase inverter unit export to connect tested three-phase reactor triple-phase line on, its current signal gathered exports the first connection terminal of calculation control unit respectively to; Calculating the composition controlling list with annexation is: the first connection terminal, modulate circuit, A/D, CPLD, dual port RAM and the DSP that are connected successively, CPLD also distinguishes external PWM transmission circuit and input and output circuit, and described PWM transmission circuit and input and output circuit are outreached by the second connection terminal.

Three phase inverter unit adopts 3 single-phase inverters composition, and three phase inverter unit adopts PWM (width modulation) technology, the frequency of PWM at 2 ~ 12kHz, instruction cycle 40us, device sine wave output frequency range is 0.5 ~ 50Hz; Three-phase electricity detecting signal unit adopts Hall current sensor to measure three-phase current i _a, i _b, i _c, adopt RC filtering circuit and Hall voltage sensor measurement three-phase voltage u _a, u _b, u _c; Calculation control unit CPU adopts TI company floating point DSP chip TMS320C6713, and core frequency can reach 225MHz.Logic chip adopts CPLD, controls outside 8 passage 14 AD, and sends PWM instruction.Controller inside possesses the On-off signal output module of some, for controlling external communication contactor.

The current signal of Hall current sensor collection enters A/D converter through the RC filtering of control panel, the CPLD control AD sampling time, by the signal write dual port RAM gathered; DSP calculates amplitude and the frequency of instruction current according to the volumeter of tested three-phase reactor rated current, inductance ratings value and testing equipment, CPLD is write back through dual port RAM, CPLD adopts the pwm signal needed for the generation of stagnant ring comparative approach, delivers to driver through isolating chip; Adopt optical-fibre communications between controller and inverter, improve the interference free performance of testing equipment calculation and control device unit.

Adopt said system to carry out the method for three-phase reactor reactance value measurement, comprise the following steps:

The first step, calculates according to the volumeter of the inductance ratings value of tested three-phase reactor, rated current and native system the maximum frequency that native system can bear;

Second step, calculates according to native system output frequency the sampled voltage phase shift and amplitude coefficient that RC wave filter causes, and instead pushes away voltage over zero;

3rd step, finds voltage over zero according to detectable voltage signals, and sets up sin ω t and cos ω t;

4th step, calculates the meritorious of output current and reactive current according to sin ω t and cos ω t;

5th step, calculates the inductance value of reactor according to voltage and reactive current.

Claims (4)

1. a reactance value measuring system for three-phase reactor, is characterized in that: comprise three phase inverter unit, three-phase electricity detecting signal unit and calculation control unit;

The DC side of described three phase inverter unit connects tested three-phase reactor one end respectively through the output of rectification or the direct supply provided for inverter with accumulator, AC for system after the low-pass filter that RC forms; Tested three-phase reactor other end welding system neutral point;

Described three-phase electricity detecting signal unit be connected on respectively three phase inverter unit export to connect tested three-phase reactor triple-phase line on, its current signal gathered exports the first connection terminal of calculation control unit respectively to;

The composition of described calculation control unit with annexation is: the first connection terminal be connected successively, modulate circuit, A/D, CPLD (Complex Programable Logic Device), dual port RAM and DSP (Digital Signal Processing), described CPLD also distinguishes external PWM transmission circuit and input and output circuit, and described PWM transmission circuit and input and output circuit are outreached by the second connection terminal.

2. the reactance value measuring system of three-phase reactor according to claim 1, is characterized in that: the low-pass filter of described RC composition is resistance and the electric capacity of series connection, and the Hall voltage sensor in parallel at electric capacity two ends, it exports u _a, u _b, u _c.

3. the reactance value measuring system of three-phase reactor according to claim 2, it is characterized in that: described three phase inverter unit adopts 3 single-phase inverter compositions, three phase inverter unit adopts PWM (width modulation) technology, the frequency of PWM is at 2 ~ 12kHz, instruction cycle 40us, device sine wave output frequency range is 0.5 ~ 50Hz;

Described three-phase electricity detecting signal unit adopts Hall current sensor to measure three-phase current i _a, i _b, i _c, adopt RC filtering circuit (see Fig. 3 modulate circuit) and Hall voltage sensor measurement three-phase voltage u _a, u _b, u _c;

Described calculation control unit CPU adopts TI company floating point DSP chip TMS320C6713, and core frequency can reach 225MHz; Logic chip adopts CPLD, controls outside 8 passage 14 AD, and sends PWM instruction; Controller inside possesses the On-off signal output module of some, for controlling external communication contactor.

4. adopt the system as described in claim 1-3 any one to carry out a method for three-phase reactor reactance value measurement, it is characterized in that comprising the following steps:

The first step, calculates according to the volumeter of the inductance ratings value of tested three-phase reactor, rated current and native system the maximum frequency that native system can bear;

Second step, calculates according to native system output frequency the sampled voltage phase shift and amplitude coefficient that RC wave filter causes, and instead pushes away voltage over zero;

3rd step, finds voltage over zero according to detection magnitude of voltage, and sets up sin ω t and cos ω t;

In formula, ω is power supply angular frequency; T is the time;

4th step, calculates the meritorious of output current and reactive current according to sin ω t and cos ω t:

$I_{M1}=\frac{2}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{i}_k\sin \left(k\right);$

$I_{M2}=\frac{2}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{i}_k\cos \left(k\right);$

In formula, I _m1, I _m2be respectively active current, peak value of idle current; N is a cycle discrete point number; i _kit is the electric current discrete signal detected; Sin (k), cos (k) are the discrete magnitude of sin ω t and cos ω t respectively;

5th step, calculates the inductance value of reactor according to voltage and reactive current:

$L=\frac{U_M}{{\mathrm{\ωI}}_{M2}}$

Capacity formula due to three-phase reactor is P _n=3 ω L _ni ²namely the capacity of reactor is directly proportional to the frequency applying electric current, and therefore under same test current, reducing ω can effectively reduce capacity of experiment, also just can reduce required testing equipment capacity.