Patent ID: 12191795

DETAILED DESCRIPTION

When the output voltage is regulated by a conventional automatic voltage regulator, the voltage between specific output terminals is measured, and the exciting current is controlled to allow the measured output voltage to be a target voltage. However, with the control by the conventional automatic voltage regulator, the difference in the voltage between the terminals is enlarged because the load is unevenly distributed. This causes a problem that the percentage of voltage fluctuation of the three-phase average output voltage (the percentage of three-phase E voltage fluctuation), or the percentage of voltage fluctuation of the single phase output voltage (the percentage of single phase voltage fluctuation) is increased with respect to a rated voltage.

In addition, in the case where the control is performed by the conventional automatic voltage regulator in the alternating current generator, when either the three-phase or the single phase is used independently, the output voltage between the terminals diverges from the target voltage due to mismatch between the output terminal connected to the load and the terminal at which the output voltage is measured. This causes a problem of worsening the percentage of voltage fluctuation.

The present invention has been achieved to solve the above-described problems. It is therefore an object of the invention to control the percentage of voltage fluctuation with respect to the rated voltage, in particular, to be able to control the percentage of voltage fluctuation with both the three-phase and the single phase when the three-phase and the single phase are used together, and to prevent the percentage of voltage fluctuation from worsening due to the mismatch between the terminal connected to the load and the terminal at which the output voltage is measured when either the three-phase or the single phase is used independently.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description below, the same reference numbers in the different drawings indicate the same functional parts, and therefore repeated description for each of the drawings is omitted.

As illustrated inFIG.1, a voltage fluctuation suppressing device1for an alternating current generator10(hereinafter, referred to simply as “voltage fluctuation suppressing device1”) is provided for the alternating current generator10, and includes a controller20configured to suppress the fluctuation of the output voltage obtained from output terminals11A of an armature11. The controller20includes at least a load current detector21, an in-use output terminal identifier22, an inter-terminal voltage detector23, and an excitation controller24, as functions to perform computation. The controller20includes at least a processor26, and a memory27configured to be able to communicate with the processor26. The processor26reads a program stored in the memory27to function as the load current detector21, the in-use output terminal identifier22, the inter-terminal voltage detector23, and the excitation controller24.

The load current detector21of the controller20detects a load current flowing through the output terminals11A of the armature11. With the illustrated example, the armature11includes three-phase output terminals (R phase terminal, S phase terminal, and T phase terminal), and single phase output terminals (U phase terminal and W phase terminal). Here, the load current is detected via current detectors CR, CS, Ct, CU, and CWprovided on wires LR, LS, LT, LUand LWconfigured to connect armature windings of the armature11to the output terminals11A, respectively, and the detected load current is inputted to the load current detector21.

With the illustrated example, the output terminals11A of the armature11include the R phase terminal, the S phase terminal, the T phase terminal, the U phase terminal, and the W phase terminal, but this is by no means limiting. The armature11may not be limited as long as it includes three-phase output terminals formed by a Y connection or a triangle connection of the armature windings. In this case, the individual single phase output terminals (the U phase terminal and the W phase terminal) may be eliminated, and the R phase terminal, the S phase terminal, and the T phase terminal may be used as three-phase output terminals or single phase output terminals in a three-phase generator.

The in-use output terminal identifier22of the controller20identifies the output terminals11A from which the load current is detected, based on the detection of the load current detector21. To be more specific, when the load current is detected from all the wires LR, LS, LT, LUand LW, the in-use output terminal identifier22identifies both the three-phase output terminals (R phase terminal, S phase terminal, and T phase terminal) and the single phase output terminals (U phase terminal and W phase terminal) as the in-use output terminals. Meanwhile, when the load current is detected from any of the wires LR, LS, LT, LUand LW, the in-use output terminal identifier22identifies the output terminal of the wire from which the load current is detected, as the in-use output terminal.

The inter-terminal voltage detector23of the controller20detects inter-terminal voltages via detection points PR, PS, PT, PU, and PWprovided on the wire LR, LS, LT, LUand LW, respectively. In this case, the inter-terminal voltage detector23detects inter-terminal voltages of the output terminals including the in-use output terminals identified by the in-use output terminal identifier22.

That is, when both the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal), and the single phase output terminals (the U phase terminal and the W phase terminal) are identified as the in-use output terminals (when the three-phase and the single phase are used together), the inter-terminal voltage detector23detects all of inter-terminal voltages VR-S, VS-T, VT-R, and VU-Wbetween R and S, between S and T, between T and R, and between U and W, respectively. When only the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) are identified as the in-use output terminals (when the three-phase is used independently), the inter-terminal voltage detector23detects the inter-terminal voltages VR-S, VS-T, and VT-Rbetween R and S, between S and T, and between T and R, respectively. Meanwhile, when only the single phase output terminals (U phase terminal and W phase terminal) are identified as the in-use output terminals (when the single phase is used independently), the inter-terminal voltage detector23detects the inter-terminal voltage VU-Wbetween U and W.

Then, the excitation controller24of the controller20calculates the output voltage by using the voltage values of the inter-terminal voltages detected by the inter-terminal voltage detector23, that is, only the inter-terminal voltages of the output terminals including the identified in-use output terminals, and controls the excitation to allow the output voltage to be a target voltage. By this means, it is possible to calculate the output voltage only from the inter-terminal voltages of the output terminals11A actually being used. The excitation current flowing through an exciting coil12of the alternating current generator10is controlled based on the output voltage, and therefore it is possible to suppress the voltage fluctuation of the output voltage.

The excitation controller24may control the excitation based on the output voltage which is an instantaneous value of the inter-terminal voltage detected by the inter-terminal voltage detector23, or based on the output voltage calculated by computing the inter-terminal voltage detected by the inter-terminal voltage detector23.

In the case where the instantaneous value is used as the output voltage, as an example, the percentage of fluctuation with respect to the rated voltage is calculated as needed, and when the percentage of fluctuation exceeds a threshold, the target voltage is reset. In this case, when both the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) and the single phase output terminals (the U phase terminal and the W phase terminal) are identified as the in-use output terminals, the target voltage is increased when the percentage of fluctuation of the three-phase or the single phase reaches the lower limit, and the target voltage is reduced when the percentage of fluctuation of the three-phase or the single phase reaches the upper limit. Then, the target voltage is increased and reduced a set number of times (several times) at a set interval (several seconds), and the output voltage is regulated by the PID control to allow the percentage of fluctuation of the three-phase to be within an allowance (for example, plus or minus 2.5%). In this case, it is preferred that the threshold of the percentage of fluctuation of the three-phase is equal to or smaller than 2.5%, and the percentage of fluctuation of the single phase is equal to or smaller than 3.5%.

When the output voltage is calculated by the computation, an output voltage calculator25is provided for the detected value of the inter-terminal voltage detector23as illustrated inFIG.2, and the excitation is controlled by using the output voltage calculated by the output voltage calculator25. In this case, the output voltage calculated by the output voltage calculator25covers the inter-terminal voltages of all of the in-use output terminals. The processor26reads the program stored in the memory27to function as the output voltage calculator25.

An example of the output voltage calculator25calculates an average value of the detected inter-terminal voltages as the output voltage, when either the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal), or the single phase output terminals (the U phase terminal and the W phase terminal) are identified as the in-use output terminals by the in-use output terminal identifier22, and used independently. Meanwhile, when both the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal), and the single phase output terminals (the U phase terminal and the W phase terminal) are identified as the in-use output terminals by the in-use output terminal identifier22, and used together, the average value of the inter-terminal voltages of the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) is calculated as a first average value (three-phase E voltage), and the average value obtained by averaging the inter-terminal voltage of the single phase output terminals (the U phase terminal and the W phase terminal) and the first average value (the three-phase E voltage) is calculated as a second average value which is the output voltage.

An example of a calculating formula table of output voltages of the output voltage calculator25is illustrated inFIGS.3A and3B. In this calculating formula table, No 1 to No. 3 indicate cases where the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) are used independently, and one of them is identified as the in-use output terminal. In these cases, the average value of two of the inter-terminal voltages (VR-S, VS-T, and VT-R) of the tree-phase output terminals including the one in-use output terminal is calculated as an output voltage.

In addition, No. 4 and No. 5 indicate cases where the single phase output terminals (the U phase terminal and the W phase terminal) are used independently, and one of them is identified as the in-use output terminal. No. 15 indicates a case where the single phase output terminals (the U phase terminal and the W phase terminal) are used independently, and two of them are identified as the in-use output terminals. In these cases, the inter-terminal voltage VU-Rof the single phase output terminals is calculated as an output voltage.

No. 6 and No. 7 indicate cases where the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) are used independently, and two of them are identified as the in-use output terminals. In these cases, the inter-terminal voltage of the identified two in-use output terminals is calculated as an output voltage. In addition, No. 16 indicates a case where the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) are used independently, and all of them are identified as the in-use output terminals. In this case, the average value ((VR-S+VS-T+VT-R)/3) of the inter-terminal voltages (VR-S, VS-T, and VT-R) is calculated as an output voltage.

The other numbers in the calculating formula table illustrated inFIGS.3A and3Bindicate cases where the three-phase and the single phase are used together. In these case, the average value of the inter-terminal voltages of the three-phase output terminals including the in-use output terminals is calculated as a first average value, and the average value obtained by averaging the first average value and the inter-terminal voltage of the single phase output terminals is calculated as a second average value which is an output voltage.

Here, the example where the average value is calculated by the computation of the output voltage calculator25is presented. However, the computation of the output voltage calculator25is not limited to this example. For example, the output voltage may be calculated by various computations, for example, a median value is calculated in addition to or instead of the average value, or correction or conversion is performed by multiplication of specific coefficients.

FIG.4illustrates another configuration example of the voltage fluctuation suppressing device according to an embodiment of the invention. In the voltage fluctuation suppressing device1illustrated inFIG.4, the armature11has a neutral point, and a detecting point Po of the inter-terminal voltage detector23is provided on a wire Lo connecting to a terminal for the neutral point (neutral point terminal) O. In this example, the detected inter-terminal voltages of all the output terminals (the R phase terminal, the S phase terminal, the T phase terminal, the U phase terminal, and the W phase terminal) are phase voltages (VR-O, VS-O, VT-O, VU-O, and VW-O) between the neutral point terminal O and the respective output terminals.

FIGS.5A and5Billustrate an example of the calculating formula table of the output voltages of the output voltage calculator25illustrated inFIG.4. With this example, all the calculating formulas (No. 1 to No. 32) calculate output voltages by using the phase voltages of the output terminals identified by the in-use output terminal identifier22. By this means, it is certainly possible to calculate the output voltage corresponding to the load. The usage conditions of the three-phase and the single phase in No. 1 to No. 32 ofFIGS.5A and5Bcorrespond to the usage conditions illustrated inFIGS.3A and3B.

Here, in the calculating formula tables illustrated inFIGS.3A and3Bas well asFIGS.5A and5B, No. 32 indicates a case where no current is detected from all of the output terminals (the R phase terminal, the S phase terminal, the T phase terminal, the U phase terminal, and the W phase terminal). In this case, it is supposed that an error of the current detection has occurred, and therefore the output voltage is calculated assuming that the current flows through all of the output terminals (all of the output terminals are in-use output terminals).

As described above, the connection of the armature windings of the armature11is not particularly limited, but a connection illustrated inFIG.6may be adopted as an example. With this example, the armature windings having the single phase output terminals (the U phase terminal and the W phase terminal) are connected to a three-phase connection of the armature wirings having the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal). To be more specific, the three-phase output terminals (the R phase terminal, the S phase terminal, and the T phase terminal) are one ends of three armature windings whose other ends are Y-connected to the neutral point O, and the single phase output terminals (the U phase terminal and the W phase terminal) are ends of two armature windings whose other ends are connected to the middle points of two of the three armature windings. Here,FIG.6merely illustrates an example, and the armature11is not limited as long as the three-phase and the single phase can be used independently of one another or together.

As described above, the voltage fluctuation suppressing device1according to the embodiment of the invention detects the load current for each of the output terminals to identify the output terminals actually being used; calculates the output voltage only from the inter-terminal voltages of the output terminals being used; and controls the excitation to allow the output voltage to be the target voltage. By this means, in any of the case where the three-phase is used independently, the case where the single phase is used independently, and the case where the three-phase and the single phase are used together, it is possible to control to allow an optimal output voltage for the load connected to each of the output terminals without particularly switching the connection for the detection.

By this means, it is possible to control the percentage of voltage fluctuation with respect to the rated voltage of the alternating current generator, and, when the three-phase output terminals and the single phase output terminals are used together, the excitation is controlled by using the output voltage based on the inter-terminal voltages of the three-phase output terminals and the inter-terminal voltage of the single phase output terminals. Therefore, it is possible to control the percentage of voltage fluctuation with both the three-phase output terminals and the single phase output terminals.

In addition, when either the three-phase output terminals or the single phase output terminals are used independently, the inter-terminal voltage is detected after the terminals being used are identified, and the excitation is controlled by using the output voltage calculated from the detected inter-terminal voltage. Therefore, it is possible to prevent the percentage of voltage fluctuation from worsening due to the mismatch between the output terminals being used and the terminals being detected.

Moreover, the voltage fluctuation suppressing device1according to the embodiment of the invention can control the percentage of voltage fluctuation for a generator capable of using the three-phase and the single phase together. Not only that, in a case of a three-phase generator including only three-phase output terminals, even when the terminals are used as single phase output terminals, it is possible to control the percentage of voltage fluctuation by identifying the output terminals based on the load current.

As described above, according to the invention, it is possible to control the percentage of voltage fluctuation with respect to the rated voltage, and when the three-phase output terminals and the single phase output terminals are used together, the excitation is controlled by using the output voltage based on the inter-terminal voltages of the three-phase output terminals and the inter-terminal voltage of the single phase output terminal. Therefore, it is possible to control the percentage of voltage fluctuation with both the three-phase and the single phase.

Moreover, when either the three-phase output terminals or the single phase output terminals are used independently, the inter-terminal voltage is detected after the terminals being used are identified, and the excitation is controlled by using the output voltage calculated from the detected inter-terminal voltage. Therefore, it is possible to prevent the percentage of voltage fluctuation from worsening due to the mismatch between the output terminals being used and the terminals being detected.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and the design can be changed without departing from the scope of the present invention. In addition, the above-described embodiments can be combined by utilizing each other's technology as long as there is no particular contradiction or problem in the purpose and configuration.