JPH053603B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to a phase detection device for a separately excited converter used in controlling the operation of a DC motor, such as a thyristor Leonard control device, and particularly to a phase detection device for a separately excited converter, such as a thyristor Leonard control device. The present invention relates to a phase angle detection device capable of correcting errors caused by unbalance.

[Prior art and its problems]

Conventionally, as this type of phase detection device, analog type and digital type are known, but each has the following drawbacks.

(1) Analog type types generally consist of a zero-cross detection circuit for the input voltage waveform and an integrator that integrates the phase angle equivalent for each power supply phase or firing phase, so they are not 3-phase pure bridges. A wired static power converter requires three to six sets of such circuits, and therefore the zero-cross detection level, integration time of the integrator, offset, etc. must be adjusted according to the number of circuits. The work is complicated and difficult, and it is extremely difficult to achieve strict balance between the six phases.

(2) Even if the circuit configuration is devised and adjustment elements are eliminated, the balance among the six phases cannot be strictly maintained due to variations in the constants of the elements that make up the circuit.

(3) Even if it is possible to maintain balance among the six-phase detection circuits by some method, the phase voltages may differ from each other due to unbalanced load balance for the three phases, or voltage drop, insulation, and phase voltage If there are variations in the windings of a synchronous transformer provided before the phase detector for the purpose of converting the voltage from the voltage to the line voltage, etc., an unbalance will occur in the detected value.

(4) As a result, even if the separately excited converter is firing at a constant firing control angle, there are variations in the phase angle detection values for each phase, so in reality, each phase is firing at a different control angle. This results in a current imbalance due to the ignition phase. Note that FIG. 1 is a current waveform diagram for explaining this situation. In the figure, θ _U to θ _Z represent the detected phase angle values of phases U to Z, θ^ _U to θ^ _Z represent their actual values, and α represents the ignition control angle command value, and V , it is shown that the current waveform becomes unbalanced due to variations in the detected values in the Z phase.

(5) Also, since the elements corresponding to the power supply frequency, such as the integration time of the integrator, are fixed constants, it is not possible to follow the frequency fluctuations, and as a result, the phase detection value and the actual value are different. An error occurs between
In extreme cases, problems such as commutation failure may occur during operation at the limit of the phase control angle.

[Purpose of the invention]

This invention has been made in view of these points, and it corrects errors between detection phase angles due to variations in input voltage waveforms between phases or variations in element constants, and also corrects detection errors due to fluctuations in power supply frequency. An object of the present invention is to provide a phase detection device that can perform the following steps.

[Key points of the invention]

The gist of the present invention is that a digital phase detection device includes a detection means for detecting three-phase power supply voltages supplied from a power supply to a separately excited converter, and a detection means for detecting three-phase power supply voltages supplied from a power supply to a separately excited converter; A counter that counts each phase angle equivalent amount, and digital calculation means that calculates a correction amount represented by the difference between the actual value and the logical value of each phase difference between a reference counter and other counters among these counters. This digital calculation means calculates the actual value of the power supply cycle (360°) from the sum of the phase differences between the counters, calculates the correction amount based on this actual power supply cycle value, and calculates the correction amount based on the actual value of the power supply cycle. to the corresponding counter count value to correct the error between the detected phase angles, and further correct the corrected counter count value according to the ratio of the power cycle actual value to the power cycle logical value. In this way, errors in the detected phase angle due to fluctuations in the power supply frequency are corrected.

[Embodiments of the invention]

Fig. 2 is a configuration diagram showing an embodiment of this invention;
The figure is a waveform diagram of each part for explaining the operation. In FIG. 2, 1, 3, and 5 are phase angle integration counters, 7 is a digital processing device such as a microcomputer, 8 is a bus, 9 is a synchronization signal circuit,
10 is a signal conversion circuit.

The operation shown in FIG. 2 will be explained below with reference to FIG. 3 as well.

As shown in FIG. 3A, the input line voltages V _uv , V _vw and V _wu input to the separately excited conversion device (not shown) are given to the signal conversion circuit 10, so the signal conversion circuit 10 converts the voltage V _uv , V _vw , and V _wu are converted into logic signals V _uv ′, V _wv ′, and V _wu ′, which are, for example, “1” when positive and “0” when negative. Incidentally, these signals are expressed as shown in FIG. 3B. The synchronization signal circuit 9 receives logic signals V _uv ′,
When V _vw ′ and V _wu ′ change from 0 to 1,
Counter synchronization signals S ₁ , S ₃ and S ₅ each having a predetermined pulse width are output as shown in FIG. 3C. Phase angle integration counters 1, 3, and 5 count the separately given reference clock F of frequency _f0 , and are initialized (reset) by synchronizing signals _S1 , _S3 , and _S5 , respectively.
be done. Therefore, the integrated values θ ₁ , θ ₃ , θ ₅ of the counters ₁ , ₃ , ₅ as shown in FIG. In other words, it represents the phase difference from a predetermined phase. The digital processing device 7 reads the integrated values θ ₁ , θ 3 , and θ ₅ from the counters 1, ₃ , and 5 via the bus 8, and performs the following correction calculations.

Now, if the phase angles for the ignition phases U, V, W, X, Y, and Z are respectively θ _U , θ _V , θ _W , θ _X , θ _Y , and θ _Z , then the phase angle of each phase in this case is can be expressed as the following equation (1) by combining the counter count value (θ ₁ to _{θ 3} ) and the offset angle (−60°).

θ _U = θ ₁ −60° θ _Z = θ ₃ θ _V = θ ₃ −60° θ _X = θ ₅ θ _W = θ ₅ −60° θ _Y = θ ₁ ...(1) Suppose that the equilibrium of the three phases is broken, and as a result, the counts θ _{3 and} θ 5 of counters 3 and ₅ , shown by the solid lines in Figure 3D, change to the states shown by the broken lines (note that θ ₁ is the reference value). (Assume that the phase does not change.) θ _U to θ _Z calculated by the above equation (1) also include errors, making it impossible to maintain equilibrium among the six phases.

By the way, θ ₃₆₀ = θ ₁₃ + θ ₃₅ + θ ₅₁ [where θ _no = θ _n −θ _o , θ _n > θ _o ] ...(2), then θ ₃₆₀ corresponds to one period, that is, 360°. This is the count value of the counter. Furthermore, in an ideal state, the counter counts θ ₁ , θ ₃ , θ ₅ each have a phase difference of 120° from each other, so the counter counts θ^ ₁ , θ^ ₃ , Each of θ^ ₅ is expressed as in the following equation (3).

Therefore, by rewriting equation (1) above using equation (3), each phase angle of the six ignition phases can be calculated as shown in equation (4) below, taking into account the variation among the three phases. can.

θ _U = θ ₁ - 1/6 x θ ₃₆₀ θ _Z = θ ₃ + (θ ₁₃ - 1/3 x θ ₃₆₀ ) θ _V = θ ₃ + (θ ₁₃ - 1/3 x θ ₃₆₀ ) - 1/6 _{× θ 360 θ _ _ _ _ _ _ _ _} ...(4) By the way, it can be seen that each of the above equations (4) are all equations related to θ ₁ . For example, looking at θ _W , θ _W = θ ₅ + (θ ₁₅ -2/3 x θ ₃₆₀ ) x 1/6 x θ ₃₆₀ = θ ₅ + θ ₁ - θ ₅ -5/6 x θ ₃₆₀ = θ ₁ −5/6×θ ₃₆₀ ……(5) This apparently means that it can be configured with only θ ₁ , that is, counter 1, but in this way, the counting range of θ _W is smaller than the counting range of θ ₁ from 0 to 360° (θ ₃₆₀ ). is -300゜θ _W 60゜ or 0゜θ _W 60゜, -300゜θ _W 0゜ ...(6), and the discontinuous point of θ ₁ that operates in a 360゜ cycle (at the time of initial setting of counter 1) ) becomes a discontinuous point in the measurement of θ _W.Therefore , in the present invention, the phase angle detection circuit is purposely configured with three counters, without being modified as in equation (5). , are treated as in equation (4).

Then, the terms below the second term on the right side of each equation in this equation (4) (correction term: for example, θ ₁₃ − in the equation for θ _Z
1/3×θ ₃₆₀ ) can be regarded as a constant within a short period of time, provided that the balance between phases and rapid changes in frequency are not considered. This means that in the processing device 7 shown in FIG. 2, the calculation for calculating the correction term can be performed at a low priority (interrupt) level where time constraints are relatively loose. It means. Therefore, if we express the correction terms in each equation as in the following equation (7), we get Therefore, the above equation (4) can be expressed as the following equation (8).

θ _U =θ ₁ +Δθ _U θ _Z =θ ₃ +Δθ _Z θ _V =θ ₃ +Δθ _V θ _X =θ ₅ +Δθ _X θ _W =θ ₅ +Δθ _W θ _Y =θ ₁ +Δθ _Y ...(8) In other words, the point The phase angle of each arc phase is calculated by counter 1,
It can be expressed as the sum of count values (instantaneous values) of 3 and 5 and a correction term that can be regarded as a constant in the short term.

The above is a case in which fluctuations in the power supply frequency are not taken into account, but if this is to be taken into account, the following procedure is performed.

That is, since the slopes of the counter integrated values θ ₁ , θ ₃ , and θ ₅ shown in FIG. 3D do not change depending on the frequency, the above equation (2) holds true. Therefore,
If the counter count value corresponding to 360° when the power supply frequency is equal to the nominal value f _c is θ^ ₃₆₀ , the following relational expression is established: θ^ ₃₆₀ = f ₀ /f _c (9). Therefore, by multiplying each phase angle in the above equation (8) by θ^ ₃₆₀ /θ ₃₆₀ (=k), the phase angle normalized by the nominal frequency can be found as shown in the following equation (10). can.

θ _U =k(θ ₁ +Δθ _U ) θ _Z =k(θ ₃ +Δθ _Z ) θ _V =k(θ ₃ +Δθ _V ) θ _X =k(θ ₅ +Δθ _X ) θ _W =k(θ ₅ +Δθ _W ) θ _Y =k(θ ₁ +Δθ _Y ) ...(10) In this way, the count value θ ₁ of the phase angle integration counter,
From θ ₃ , θ ₅ and their phase differences, it is possible to correct phase-to-phase imbalance due to variations in input signals and input circuit constants, and it is also possible to correct phase angle detection errors due to power supply frequency fluctuations.

FIG. 4 is a configuration diagram showing another embodiment of the present invention;
FIG. 5 is a waveform diagram of each part for explaining the operation.

As is clear from FIG. 4, this embodiment differs from the one shown in FIG.
(counters 1 to 6) are provided.
Therefore, six synchronizing signals S1 to _S6 as shown in FIG. 5C are obtained from the synchronizing signal circuit 9, and _six synchronizing signals as shown in FIG. 5D are obtained from the phase angle integration counters 1 to 6. The phase angle signals θ ₁ to _{θ 6} are obtained. In this case, it corresponds to equation (1) above. Firing phase U,
Phase angles θ _U , θ _V , for V, W, X, Y, and Z phases,
The relationship between θ _W , θ _X , θ _Y , θ _Z and the counter count values θ ₁ to _{θ 6} can be expressed as in the following equation.

θ _{U = θ 2 θ Z} = θ _{3 θ V = θ 4} θ
The count value corresponding to 360° can be calculated as shown in the following equation (12).

θ ₃₆₀ = θ ₁₂ + θ ₂₃ + θ ₃₄ + θ ₄₅ + θ ₅₆ + θ ₆₁ (However, θ _no = θ _n −θ _o , θ _n > θ _o ) ...(12) Therefore, it corresponds to the previous equation (7) The correction amount for each phase is In this case, the phase angles θ _U , θ _V , θ _W , θ _X , θ _Y , θ〓 after correcting the variations between phases are as follows: θ _U = θ ₂ + Δθ _U θ _Z = θ ₃ + Δθ _X θ _V = θ ₄ +Δθ _V θ _X =θ ₅ +Δθ _X θ _W =θ ₆ +Δθ _W θ _Y =θ ₁ +Δθ _Y ...(14) Furthermore, in order to correct for fluctuations in the power supply frequency, it is sufficient to multiply each phase angle by the coefficient k (= θ^ ₃₆₀ / θ ₃₆₀ , θ^ ₃₆₀ = f ₀ /f _c ) as described above, so θ _U = k × (θ ₂ + Δθ _U ) θ _Z = k × (θ ₃ + Δθ _Z ) θ _V = k × (θ ₄ + Δθ _V ) θ _X = k × (θ ₅ + Δθ _X ) θ _W = k × (θ ₆ +Δθ _W ) θ _Y =k×(θ ₁ +Δθ _Y ) ...(15).

In other words, even in the case of six counters, by performing simple calculations, it is possible to correct interphase unbalance and correct errors based on frequency fluctuations.

Note that in the above case, three counters are used,
Although the case where six pieces are used has been described, the case is not limited to this, and the case where two pieces are used can be similarly applied.

〔Effect of the invention〕

According to this invention, the following effects can be expected.

(b) Since everything except the input period voltage is processed digitally, there are no adjustment points, and highly accurate phase detection without temperature drift or aging is possible.

(b) Since it is assumed that the phases are unbalanced, there is no need for adjustment elements and adjustment work to maintain the balance between the phases, and a certain amount of deviation in the balance between the phases is allowed. Therefore, there is a large degree of freedom in circuit configuration.

(c) It is also possible to correct phase-to-phase variations in the input power signal, which could not be addressed by conventional phase detectors.

(d) It is possible to compensate for and cope with fluctuations in the power supply frequency, which could not be dealt with conventionally due to semi-fixed or fixed systems.

(e) The time required to perform correction calculations using the instantaneous value of the phase angle counter and the phase difference is approximately zero, and therefore, it is difficult to compensate for unbalance between phases and fluctuations in power supply frequency that change over time. It is possible to follow even if

(f) The above (b) to (b) can be implemented without adding any hardware to the basic circuit as a phase detector.
(e) can be realized.

(g) Correction can be made using the four arithmetic operations of addition, subtraction, multiplication, and division (if only the phase balance needs to be corrected, only addition and subtraction are required), which reduces the burden on the processing device.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram for explaining the degree of current variation due to phase-to-phase imbalance of phase angle detection values.
FIG. 2 is a configuration diagram showing an embodiment of the present invention, FIG. 3 is a waveform diagram of each part to explain the operation of FIG. 2, FIG. 4 is a configuration diagram showing another embodiment of the invention, and FIG.
The figure is a waveform diagram of each part for explaining the operation of FIG. 4. Code explanation, 1 to 6... Phase angle integration counter,
7... Digital processing device (microcomputer), 8... Bus, 9... Synchronous signal circuit, 10...
...Signal conversion circuit.

Claims (1)

[Claims] 1. Detecting means for detecting three-phase power supply voltage supplied from the power supply to the separately excited converter; and detecting means for detecting the phase angle equivalent of each phase in synchronization with each phase of the three-phase voltage. It has a counter for counting, and a digital calculation means for calculating a correction amount represented by the difference between the actual value and the theoretical value of each phase difference between a reference counter and other counters among these counters, The digital calculation means calculates the actual value of the power supply cycle (360°) from the sum of the phase differences between the counters, calculates the correction amount based on this actual power supply cycle value, and converts these correction amounts into the corresponding counter count value. The error between the detected phase angles is corrected by adding the power supply frequency to A digital phase detection device that corrects errors in detected phase angles due to fluctuations.