CN103134969A - Power factor corrector and phase voltage estimation method - Google Patents

Abstract

The invention discloses a power factor corrector and a voltage estimation method in an electric system. The power factor corrector comprises a parameter sampling circuit and a signal processing circuit, wherein the parameter sampling circuit is used for obtaining phase voltage on each phase line of the electric system and line voltage among the phrase lines through sampling to supply the voltage to the signal processing circuit, and the signal processing circuit is used for confirming effective values of sampled phase voltage and sampled line voltage according to the sampled phase voltage value and the sampled line voltage value and is used for calculating an estimation phase voltage value on a corresponding phase line through a degree of unbalance of the line voltage according to the effective values. The power factor corrector and the phase voltage estimation method can well estimate the voltage in the electric system.

Description

Power factor corrector and phase voltage estimation method

Technical Field

The present invention relates to power equipment and methods, and more particularly, to a power factor corrector and a phase voltage estimation method.

Background

For a three-phase three-wire system zero-line-free power system, since there is no zero potential reference point in the system, an artificial reference point (i.e., a virtual reference point) in the system is used as a sampling reference point of an actual input voltage, such as a connection point N of three phase voltages shown in fig. 2. When the effective values of the three live wires are equalized, the phase voltages of the respective live wires based on the virtual reference point are equal to each other, and the measured phase voltages are equal to the actual voltages.

However, when the effective values of the voltages on the three lines are not balanced, such as the input voltages are asymmetric or unbalanced in magnitude or the input voltage harmonics are different between different phases, the artificial reference point may float and thus differ from the actual zero potential reference point, and therefore sampling the voltages according to the artificial reference point in the system will result in the sampled phase voltages being different from the actual voltages.

At present, the commonly adopted solution to the above problems is: and generating a zero potential reference point on the secondary side by using the input three-phase transformer, and taking the zero potential reference point as a system reference point. However, in general, the input transformer is very bulky and its cost is not negligible, so this solution is not ideal.

Disclosure of Invention

The present invention provides a power factor corrector and a voltage estimation method in an electric power system, so as to estimate a voltage in the electric power system.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a power factor corrector comprising:

the parameter sampling circuit is used for acquiring phase voltages on all phase lines of the power system and line voltages among all the phase lines through sampling and providing the phase voltages and the line voltages to the signal processing circuit;

the signal processing circuit is configured to determine effective values of the sampled phase voltage and the sampled line voltage according to the sampled phase voltage value and the sampled line voltage value, and calculate an estimated phase voltage value on a corresponding phase line by utilizing the unbalance degree of the line voltage according to the effective values.

The signal processing circuit includes: an analog-to-digital conversion unit and a calculation unit.

Wherein the analog-to-digital conversion unit is configured to convert the sampled phase voltages and line voltages from analog signals to digital signals, which are provided to the calculation unit.

The calculating unit is configured to determine an effective value of the sampling phase voltage on each phase line according to the digital sampling phase voltage value, determine an effective value of each sampling phase voltage according to the digital sampling phase voltage value, and determine an estimated phase voltage value on each phase line according to the effective values of the sampling phase voltages on all the phase lines and the effective values of all the sampling phase voltages.

The calculation unit is configured to: and calculating the average value of the sampling phase voltage effective values according to the effective values of the sampling phase voltages on all the phase lines, calculating the average value of the sampling line voltage effective values according to the effective values of all the sampling line voltages, and determining the estimated phase voltage value on the corresponding phase line according to the average value of the sampling phase voltage effective values, the average value of the sampling line voltage effective values and the effective value of the sampling line voltage between any phase lines.

The calculation unit is configured to: according to the formula

$V_{a\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the first phase line; and/or according to a formula

$V_{b\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ca}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on a second phase line; and/or according to a formula

$V_{c\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the third phase line;

va _ acqui is an effective value of a sampling phase voltage on the first phase line, Vb _ acqui is an effective value of a sampling phase voltage on the second phase line, and Vc _ acqui is an effective value of a sampling phase voltage on the third phase line; vab _ acqui is the effective value of the sampled line voltage between the first and second phase lines, Vbc _ acqui is the effective value of the sampled line voltage between the second and third phase lines, and Vca _ acqui is the effective value of the sampled line voltage between the first and third phase lines.

In another aspect of the present invention, a method for estimating voltage in an electric power system includes:

sampling, namely obtaining phase voltages on all phase lines of the power system and line voltages among all the phase lines through sampling;

and a calculating step, namely determining effective values of the sampled phase voltage and the sampled line voltage according to the sampled phase voltage value and the sampled line voltage value, and calculating an estimated phase voltage value on the corresponding phase line by utilizing the unbalance degree of the line voltage according to the effective values.

The calculating step includes:

calculating effective values, converting the sampled phase voltages and line voltages from analog signals to digital signals, determining the effective value of the sampled phase voltages on each phase line according to the digital sampled phase voltage values, and determining the effective value of each sampled line voltage according to the digital sampled line voltage values;

and calculating an estimated phase voltage value, and determining the estimated phase voltage value on each phase line according to the effective value of the sampled phase voltage on each phase line and the effective values of all the sampled line voltages.

The calculating the effective phase voltage value includes:

calculating the average value of the sampling phase voltage effective values according to the effective values of the sampling phase voltages on all the phase lines, and calculating the average value of the sampling line voltage effective values according to the effective values of all the sampling line voltages;

and determining an estimated phase voltage value on the corresponding phase line according to the average value of the effective values of the voltage of the sampling phase, the average value of the effective values of the voltage of the sampling line and the effective value of the voltage of the sampling line between any phase lines.

The calculating step includes: according to the formula

$V_{a\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the first phase line; and/or according to a formula

$V_{b\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ca}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on a second phase line; and/or according to a formula

$V_{c\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the third phase line;

va _ acqui is an effective value of a sampling phase voltage on the first phase line, Vb _ acqui is an effective value of a sampling phase voltage on the second phase line, and Vc _ acqui is an effective value of a sampling phase voltage on the third phase line; vab _ acqui is the effective value of the sampled line voltage between the first and second phase lines, Vbc _ acqui is the effective value of the sampled line voltage between the second and third phase lines, and Vca _ acqui is the effective value of the sampled line voltage between the first and third phase lines.

Therefore, the power factor corrector and the voltage estimation method in the power system provided by the embodiment of the invention can better estimate the voltage, so that the system is monitored by utilizing the estimated voltage.

The above aspects, features and advantages of the present invention and the implementation thereof will be further explained in a clear and understandable manner by describing embodiments and referring to the accompanying drawings.

Drawings

FIG. 1 is a schematic diagram of a power factor corrector according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a three-phase three-wire power system according to an embodiment of the present invention, and illustrates a structure of a resistance voltage division sampling unit;

FIG. 3 is a flow chart of the processing of a compute unit in one implementation of the invention.

In particular, the reference symbols used in the above figures are as follows:

FIG. 1: a parameter sampling circuit 101 and a signal processing circuit 102.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be noted that in the following description, numerous specific details are disclosed to facilitate understanding. It will be understood by those skilled in the art, however, that the present invention may be practiced without some or all of these specific details. Well-known techniques have not been described in detail to avoid unnecessary confusion.

As previously described in connection with fig. 2, in a three-wire, three-phase power system, the phase voltages on the respective wires are voltages relative to a virtual reference point N, since there is no neutral wire. When the effective values of the lines are not equalized, the virtual reference point may float, resulting in that the acquired phase voltages are not actual voltages. As will be appreciated by those skilled in the art, phase voltage is the voltage relative to a reference point and line voltage is the voltage between two hot lines. Therefore, the value of the line voltage can be accurately obtained even if the effective value of the voltage on each line is unbalanced.

Further, the inventors of the present invention have found that there is an approximately direct proportional relationship between the degree of imbalance of the line voltage and the degree of imbalance of the phase voltage. As shown in fig. 2, there are three phase lines in a three-wire, three-phase power system, which are respectively referred to as a first phase line a, a second phase line B, and a third phase line C.

Wherein the phase voltage unbalance f of the first phase line A_AUnbalance f of line voltage between second and third phase lines B and C_BCThe relationship of (1) is:

f_A＝2·f_BC。

the other two phase lines also have a similar relationship.

WhileWherein V_BCIs the line voltage, V, between lines B, C_avgLIs the average of the individual line voltages and, $V_{\mathrm{avgL}}=\frac{V_{\mathrm{BC}}+V_{\mathrm{AC}}+V_{\mathrm{AB}}}{3}.$

then the process of the first step is carried out, $f_A=2\·\frac{V_{\mathrm{BC}}-V_{\mathrm{avgL}}}{V_{\mathrm{avgL}}}.$

further, V_A＝V_avgP-f_A·v_AvgPWherein

V_A、V_BAnd V_CRespectively the phase voltages on the first, second and third phase line.

The voltages mentioned in the above description are all root mean square, i.e. effective, values of the acquired voltage values.

The principle of the solution according to the invention is therefore to correct the phase voltage values obtained with accurate line voltage values, so that phase voltage values are obtained which are very close to the actual voltage.

Therefore, embodiments of the present invention provide a Power Factor Corrector (PFC) and a voltage estimation method in an electric power system, which are used to estimate a phase voltage value to obtain an estimated phase voltage value (or referred to as a calculated phase voltage value) that is closer to an actual phase voltage value. Further, even when the imbalance condition of the phase voltages deteriorates, the power factor corrector provides an estimated phase voltage value having a lower degree of error from the actual voltage than the conventional technique. Therefore, the power factor corrector provided by the embodiment of the invention can be used for better judging and monitoring the unbalanced condition of the three-phase input voltage.

In one embodiment of the present invention, as shown in fig. 1, a power factor corrector includes: a parameter sampling circuit 101 and a signal processing circuit 102. The parameter sampling circuit 101 is configured to obtain a sampling phase voltage and/or a sampling line voltage in the power system, and provide the sampling phase voltage and/or the sampling line voltage to the signal processing circuit 102.

Specifically, the parameter sampling circuit 101 includes: the device comprises a resistance voltage division sampling unit and an operational amplifier differential sampling unit. In practical application, an implementation of the resistance voltage division sampling unit is shown in fig. 2. The resistors shown in the figure are used for voltage division and the capacitors are used for filtering. The operational amplifier differential sampling unit is used for converting a high voltage value into a low voltage value, and providing the low voltage value to the signal processing circuit 102.

The signal processing circuit 102 is configured to obtain an estimated phase voltage value according to the sampled phase voltage value and the sampled line voltage value, and the circuit may be implemented by using a Digital Signal Processor (DSP). Specifically, the signal processing circuit 102 includes: an analog-to-digital (A/D) conversion unit and a calculation unit.

In light of the foregoing description of the principles of the present invention, the calculation unit may determine the estimated phase voltage values on phase lines A, B and C, respectively, in accordance with equations (1) - (3) as follows.

$V_{a\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3---\left(1\right)$

$V_{b\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ca}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3---\left(2\right)$

$V_{c\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3---\left(3\right)$

In equations (1) to (3) above, Va _ acqui, Vb _ acqui, and Vc _ acqui are Root Mean Square (RMS) values (i.e., effective values) of the sampled phase voltages on the A, B and C phase lines, respectively, Vab _ acqui, Vbc _ acqui, and Vca _ acqui are root mean square values of the sampled line voltages on phase lines a and B, phase lines B and C, and between phase lines a and C, and Va _ estim, Vb _ estim, and Vc _ estim are estimated phase voltage values on phase line A, B, C, respectively.

As indicated previously, the calculation of the phase voltage values on the three phase lines using the above parameters guarantees their accuracy even in the case of voltage imbalances, since they are not connected to a reference point.

In one specific implementation, the processing flow of the computing unit is shown in fig. 3, and includes the following steps.

Step 301: the a/D conversion results of the sampling phase voltages Va _ sample, Vb _ sample, Vc _ sample are read from the analog-to-digital conversion unit.

Step 302: the sum-squared of the sampled phase voltages Va _ sample, Vb _ sample, Vc _ sample on the respective phase lines and the sum-squared of the sampled line voltages Vab _ sample, Vbc _ sample, Vca _ sample between the respective phase lines are determined.

Wherein,

Vab_sample＝Va_sample-Vb_sample，

Vbc_sample＝Vb_sample-Vc_sample，

Vca_sample＝Vc_sample-Va_sample。

those skilled in the art will appreciate that the above calculation is not a simple numerical operation, but rather involves the operation of a phase angle, since the phase voltages of the respective phase lines have phases. This is common knowledge in the art and will not be described further herein.

Step 303: it is determined whether a voltage sampling period (typically a mains period) is over, and if so, step 304 is performed. Otherwise, return to execute step 301.

Step 304: and calculating effective values (namely root mean square values) Va _ acqui, Vb _ acqui and Vc _ acqui of the voltage of the sampling phase, and effective values Vab _ acqui, Vbc _ acqui and Vca _ acqui of the voltage of the sampling line.

Step 305: the average of the effective values of the voltages of the three sampled phases is calculated and, as previously mentioned,

$V_{\mathrm{avgP}}=\frac{V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}}}{3},$

and calculates the average of the effective values of the three sample line voltages, as previously described,

$V_{\mathrm{avgL}}=\frac{V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ac}\_\mathrm{acqui}}}{3}.$

step 306: calculating estimated phase voltage values V on phase lines A, B and C_{a_estim}、V_{b_estim}And V_{c_estim}，

$V_{a\_\mathrm{estim}}=(1-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-V_{\mathrm{avgL}}}{V_{\mathrm{avgL}}})\·V_{\mathrm{avgP}},$

$V_{b\_\mathrm{estim}}=(1-2\·\frac{V_{\mathrm{ac}\_\mathrm{acqui}}-V_{\mathrm{avgL}}}{V_{\mathrm{avgL}}})\·V_{\mathrm{avgP}},$

$V_{c\_\mathrm{estim}}=(1-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-V_{\mathrm{avgL}}}{V_{\mathrm{avgL}}})\·V_{\mathrm{avgP}}$

In another embodiment of the present invention, there is also provided a voltage estimation method in a power system, including:

phase voltage of each phase line of the power system and line voltage among the phase lines are obtained through sampling;

and determining effective values of the sampled phase voltage and the sampled line voltage according to the sampled phase voltage value and the sampled line voltage value, and calculating an estimated phase voltage value on the corresponding phase line by utilizing the unbalance degree of the line voltage according to the effective values. Note that both the phase voltage value and the line voltage value obtained by sampling are instantaneous values.

In one embodiment, a method for calculating an estimated phase voltage value using a sampled phase voltage value and an effective value of the sampled line voltage value includes:

converting the sampled phase voltage and line voltage from analog signals into digital signals, determining an effective value of the sampled phase voltage on each phase line according to the digital sampled phase voltage values, and determining an effective value of each sampled line voltage according to the digital sampled line voltage values;

determining estimated phase voltage values on the phase lines according to effective values Va _ acqui, Vb _ acqui and Vc _ acqui of the sampling phase voltages on all the phase lines and effective values Vab _ acqui, Vbc _ acqui and Vca _ acqui of all the sampling line voltages;

va _ acqui is an effective value of a sampling phase voltage on a phase line A, Vb _ acqui is an effective value of a sampling phase voltage on a phase line B, and Vc _ acqui is an effective value of a sampling phase voltage on a phase line C.

For example, the calculating unit in the PFC may determine the estimated phase voltage value Va _ estim on the phase line a according to Va _ acqui, Vb _ acqui, Vc _ acqui, Vab _ acqui, Vbc _ acqui, and Vca _ acqui, and the specific processing flow may refer to fig. 3, which is not described herein again.

Of course, the calculation unit in the PFC may also determine the estimated phase voltage value Vb _ estim on the phase line B or the estimated phase voltage value Vc _ estim on the phase line C according to Va _ acqui, Vb _ acqui, Vc _ acqui, Vab _ acqui, Vbc _ acqui, and Vca _ acqui.

In one specific implementation, the method for determining the estimated phase voltage values on the phase lines according to Va _ acqui, Vb _ acqui, Vc _ acqui, Vab _ acqui, Vbc _ acqui, and Vca _ acqui includes:

calculating an average value VavgP of the effective values of the sampled phase voltages according to the effective values of the sampled phase voltages on all the phase lines, and calculating an average value VavgL of the effective values of the sampled line voltages according to the effective values of all the sampled line voltages (see step 305); and determining an estimated phase voltage value on the other phase line according to the VavgP, VavgL and the effective value of the sampled line voltage between any two phase lines.

For example, Va _ estim can be determined from VavgP, VavgL, and Vbc _ acqui, and step 306 provides a specific calculation example.

In yet another specific implementation, a method of calculating an estimated phase voltage value using a sampled phase voltage value and an effective value of the sampled line voltage value includes: according to the formula

$V_{a\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on phase line A; and/or according to a formula

$V_{b\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ca}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on phase line B; and/or according to a formula

$V_{c\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on phase line C;

va _ acqui is an effective value of a sampling phase voltage on a phase line A, Vb _ acqui is an effective value of a sampling phase voltage on a phase line B, and Vc _ acqui is an effective value of a sampling phase voltage on a phase line C; vab _ acqui is the effective value of the sampling line voltage between phase lines A and B, Vbc _ acqui is the effective value of the sampling line voltage between phase lines B and C, and Vca _ acqui is the effective value of the sampling line voltage between phase lines C and A.

Further, after determining the estimated phase voltage values, performance evaluation may be performed according to equations (4) and (5).

In one specific example, the root mean square value Va of the actual phase voltage is 175, Vb is 220, and Vc is 265. The estimated value of the power factor corrector provided by the embodiment of the invention is Va _ estim-176.301, and error-1.301; vb _ estim is 218.864, error is-1.135; vc _ estim ═ 265.987, error ═ 0.987. It can be seen that when the degree of imbalance (UnbalanceDegreee) is less than or equal to 20%, the error tolerance value (ErrorDegrere) is less than or equal to 0.7%; even when the degree of imbalance reaches 50%, the degree of error is only 2%. If the conventional technique is used, the error margin value is already > 25% even when the unbalance degree is less than or equal to 20%. Therefore, compared with the prior art, the power factor corrector provided by the embodiment of the invention has great improvement on the performance of estimating the voltage value.

$\mathrm{UnbalanceDegree}=|\frac{\mathrm{PhaseVoltA}}{\mathrm{PhaseVolaA}+\mathrm{PhaseVoltB}+\mathrm{PhaseVoltC}}-1|---\left(4\right)$

$\mathrm{ErrorDegree}=|\frac{\mathrm{CalculatedPhaseVoltA}}{\mathrm{Real}\mathrm{PhaseVoltA}}-1|---\left(5\right)$

phaseVoltA, phaseVoltB and phaseVoltC in the formula (4) are effective values of the actual phase voltage on the phase lines A, B and C respectively, realPhaseVoltA in the formula (5) is an effective value of the actual phase voltage on the phase line A, and calledPhaseVoltA is an effective value of the estimated phase voltage on the phase line A. It should be noted that the estimated phase voltages calculated or determined in the embodiments of the present invention are all effective values.

In practical applications, the power factor corrector may be: the three-phase three-wire Vienna-Like power factor corrector can also be other types of corrector. It should be noted that all three-phase three-wire system power systems can use the power factor corrector and the voltage estimation method provided by the embodiment of the invention to monitor the imbalance condition of the three-phase input voltage. Of course, other types of power systems, such as other zero-line-less systems, may also use similar PFCs for the estimation of the voltage value.

While the invention has been illustrated and described in detail in the drawings and examples, the invention is not limited to the embodiments disclosed, and other arrangements derived therefrom by those skilled in the art are within the scope of the invention.

Claims (8)

1. A power factor corrector, comprising:

the parameter sampling circuit is used for acquiring phase voltages on all phase lines of the power system and line voltages among all the phase lines through sampling and providing the phase voltages and the line voltages to the signal processing circuit;

the signal processing circuit is configured to determine effective values of the sampled phase voltage and the sampled line voltage according to the sampled phase voltage value and the sampled line voltage value, and calculate an estimated phase voltage value on a corresponding phase line by utilizing the degree of unbalance of the line voltage according to the effective values.

2. The pfc of claim 1 wherein the signal processing circuit comprises: an analog-to-digital conversion unit and a calculation unit;

wherein the analog-to-digital conversion unit is configured to convert the sampled phase voltages and line voltages from analog signals to digital signals, which are provided to the calculation unit;

the calculating unit is configured to determine an effective value of the sampling phase voltage on each phase line according to the digital sampling phase voltage value, determine an effective value of each sampling phase voltage according to the digital sampling phase voltage value, and determine an estimated phase voltage value on each phase line according to the effective values of the sampling phase voltages on all the phase lines and the effective values of all the sampling phase voltages.

3. The power factor corrector of claim 2, wherein the computing unit is configured to: and calculating the average value of the sampling phase voltage effective values according to the effective values of the sampling phase voltages on all the phase lines, calculating the average value of the sampling line voltage effective values according to the effective values of all the sampling line voltages, and determining the estimated phase voltage value on the corresponding phase line according to the average value of the sampling phase voltage effective values, the average value of the sampling line voltage effective values and the effective value of the sampling line voltage between any phase lines.

4. The power factor corrector of claim 2, wherein the calculation unit is configured to be in accordance with a formula

$V_{a\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the first phase line; and/or according to a formula

$V_{b\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ca}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on a second phase line; and/or according to a formula

$V_{c\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the third phase line;

va _ acqui is an effective value of a sampling phase voltage on the first phase line, Vb _ acqui is an effective value of a sampling phase voltage on the second phase line, and Vc _ acqui is an effective value of a sampling phase voltage on the third phase line; vab _ acqui is the effective value of the sampled line voltage between the first and second phase lines, Vbc _ acqui is the effective value of the sampled line voltage between the second and third phase lines, and Vca _ acqui is the effective value of the sampled line voltage between the first and third phase lines.

5. A method of voltage estimation in an electrical power system, comprising:

sampling, namely obtaining phase voltages on all phase lines of the power system and line voltages among all the phase lines through sampling;

and a calculating step, namely determining effective values of the sampled phase voltage and the sampled line voltage according to the sampled phase voltage value and the sampled line voltage value, and calculating an estimated phase voltage value on the corresponding phase line by utilizing the unbalance degree of the line voltage according to the effective values.

6. The voltage estimation method of claim 5, wherein the calculating step comprises:

calculating effective values, converting the sampled phase voltages and line voltages from analog signals to digital signals, determining the effective value of the sampled phase voltages on each phase line according to the digital sampled phase voltage values, and determining the effective value of each sampled line voltage according to the digital sampled line voltage values;

and calculating the estimated phase voltage value to determine the estimated phase voltage value on each phase line according to the effective value of the sampled phase voltage on each phase line and the effective values of all the sampled line voltages.

7. The voltage estimation method of claim 6, wherein the calculating an estimated phase voltage value comprises:

calculating the average value of the sampling phase voltage effective values according to the effective values of the sampling phase voltages on all the phase lines, and calculating the average value of the sampling line voltage effective values according to the effective values of all the sampling line voltages;

and determining an estimated phase voltage value on the corresponding phase line according to the average value of the effective values of the voltage of the sampling phase, the average value of the effective values of the voltage of the sampling line and the effective value of the voltage of the sampling line between any phase lines.

8. The voltage estimation method according to claim 7, wherein the calculating step includes: according to the formula

$V_{a\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{bc}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the first phase line; and/or according to a formula

$V_{b\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ca}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on a second phase line; and/or according to a formula

$V_{c\_\mathrm{estim}}=(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3-2\·\frac{V_{\mathrm{ab}\_\mathrm{acqui}}-(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}{(V_{\mathrm{ab}\_\mathrm{acqui}}+V_{\mathrm{bc}\_\mathrm{acqui}}+V_{\mathrm{ca}\_\mathrm{acqui}})/3}\·(V_{a\_\mathrm{acqui}}+V_{b\_\mathrm{acqui}}+V_{c\_\mathrm{acqui}})/3$

Determining an estimated phase voltage value on the third phase line;

va _ acqui is an effective value of a sampling phase voltage on the first phase line, Vb _ acqui is an effective value of a sampling phase voltage on the second phase line, and Vc _ acqui is an effective value of a sampling phase voltage on the third phase line; vab _ acqui is the effective value of the sampled line voltage between the first and second phase lines, Vbc _ acqui is the effective value of the sampled line voltage between the second and third phase lines, and Vca _ acqui is the effective value of the sampled line voltage between the first and third phase lines.

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