JP2007104798A - Voltage fluctuation compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction smaller than ever, more inexpensive than ever, and capable of coping with voltage fluctuation with respect to a voltage fluctuation compensator that compensates voltage fluctuation that occurs when a motor is started. <P>SOLUTION: The voltage fluctuation compensator 10 is constructed of a voltage transformer 1; a current transformer 2; a phase advance capacitor circuit 8 that includes multiple shunts constructed of a semiconductor switch 11, a reactor 12, and a capacitor 13 and is connected in parallel with a motor M; and controlling means 9 that sends out a switching signal for the switches 11. The controlling means 9 includes a compensation value detection unit 4 that computes a compensation value corresponding to a voltage fluctuation value from the outputs of the transformer 1 and the current transformer 2; a computation unit 5 that computes a number of required phase advance capacitor stages from its output; a starting signal reception unit that receives a starting signal 3 from a motor controller MC; a subtraction unit that is connected thereto and sequentially carries out subtraction from the number of phase advance capacitor stages required to be thrown each time a predetermined time has passed from when a starting signal 3 is ended; and an input commanding unit 7 that sends out a switching signal for the switches 11 according to its output. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is electrically connected to a motor load whose input capacity fluctuates, and operates to maintain a constant voltage by turning on / off a plurality of phase-advancing capacitor circuits when a voltage fluctuation occurs in a distribution line when the motor is started. The present invention relates to a capacitor open / close control type voltage fluctuation compensator.

  A pump motor installed in a pumping station or the like requires a very large amount of electric power when starting up, while the electric power used becomes almost constant when shifting to a steady operation state. Therefore, the voltage drop of the distribution line greatly fluctuates when the motor is started, and becomes a substantially constant value in the steady state.

  However, even if the motor is in a steady operation state, as long as the motor is operating and consuming electric power, a voltage drop occurs. Therefore, the conventional voltage fluctuation compensation device is provided in the device even in the steady operation state. An operation for selecting and turning on a phase advance capacitor input circuit was performed so that the voltage was boosted by inserting a phase advance capacitor and the same voltage as when the motor was stopped (see, for example, Patent Document 1).

FIG. 4 is a diagram showing a configuration of a voltage fluctuation compensator 50 according to a conventional example in which a dedicated phase advance capacitor circuit 8 is provided for each pump motor in a pumping station facility having three pump motors. . In this example, no. 1-No. 3, each of the current transformers 2 for detecting the motor current for the pumps M1 to M3 is provided, and the voltage transformer 1 for voltage detection of the distribution line is shared. The transformer T shown in the figure is generally provided when a distribution line is drawn from the off-site high voltage receiving point into the pumping station yard. Each phase advance capacitor circuit 8 shown in the figure includes a semiconductor switch 11, a series reactor 12, and a phase advance capacitor 13 connected in series, and a plurality of shunts (here, connected in parallel with the motor load). , 8a to 8d). Reference numeral 14 in the figure is a known circuit breaker.
As described above, in the voltage fluctuation compensator 50 according to this conventional example, each control system (not shown) provided for each pump electric motor advances the necessary capacity as long as the pump is operating. It is the composition which continues putting on the phase capacitor. This will be described in more detail with reference to FIG.

FIG. 5 is a time chart regarding on / off of the phase advance capacitor in the case of this conventional example. In FIG. 1-No. It is shown that each of the three motors for the pumps M1 to M3 is a three-phase induction motor, and its activation is performed by a known condorfa method. As shown in FIG. 5, in the configuration according to the conventional example, the phase-advancing capacitor is continuously turned on to compensate for the voltage drop that occurs in the steady operation state even after the start-up is completed.
FIG. 5 also shows a sequence in which a power factor adjustment (power adjustment) capacitor is turned on after the start signal ends. Generally, in a voltage fluctuation compensating device, a power adjustment capacitor can also be inserted.

  In this way, the conventional voltage fluctuation compensator is advanced so that the voltage is the same as when the motor is stopped as long as the motor is in operation, regardless of whether it is at startup or in a steady state. Continued to put in the capacitor.

  By the way, when the motor is operating at startup or in a steady state, in order to boost the voltage to the same voltage as when the motor is stopped, in addition to the voltage fluctuation caused by reactive power, voltage fluctuation caused by active power It is necessary to compensate at the same time. The voltage fluctuation compensator of this example that compensates for the voltage fluctuation that may occur at the start of the motor by the phase advance capacitor should be sufficiently considered in this respect.

Here, the voltage drop value generated when the motor is in operation can be calculated by the following equation (1).
ΔV = P × (% R × cos θ +% X × sin θ) / (10 × 10 ⁶ ) (1)
ΔV: voltage drop value [%], P: apparent electric power [VA] of motor,% R: impedance of distribution line resistance (% per 10 MVA), cos θ: power factor of motor,% X: distribution line The impedance is reactance (% per 10 MVA), and sin θ is calculated from the power factor of the motor (θ = cos ⁻¹ θ).

Further, the voltage rise value in the phase advance capacitor can be calculated by the following equation (2).
ΔV _UP = Q ×% X / (10 × 10 ⁶ ) (2)
ΔV _UP : voltage increase value (%), Q: phase advance capacitor capacity [var],% X: impedance corresponding to reactance of distribution line (% per 10 MVA).
Equation (2) is derived from the fact that the power supplied by the capacitor in equation (1) = advanced reactive power only.

For example, when the apparent power P = 500 kVA of the motor in the steady operation state, the power factor 0.8, and the impedance% R = 50 and% X = 100 of the distribution line, the voltage drop value ΔV is
ΔV = 500 × 10 ³ × (50 × 0.8 + 100 × 0.6) / (10 × 10 ⁶ )
= 5 [%]
Is calculated.

Here, the active power generated by the motor can be calculated by the following equation (3).
W = P × cos θ (3)
Note that W: active power [W] generated by the electric motor, P: apparent electric power [VA] of the electric motor, and cos θ is a power factor of the electric motor.

Therefore, the active power generated by the electric motor of this example is
W = 500 × 10 ³ × 0.8
= 400 × 10 ³ [W]
= 400 [kW]
It becomes. That is, the voltage drop value resulting from the active power is calculated as 2% from the term (% R × cos θ) in the above equation (1).

As described above, in the conventional voltage fluctuation compensator, since the phase advance capacitor is inserted so as to be the same voltage as when the motor is stopped, when the voltage drop in the steady state is compensated with the phase advance capacitor,
ΔV _UP = Q ×% X / (10 × 10 ⁶ ) = 5 [%]
Q = 5 × (10 × 10 ⁶ ) / 100 = 500 × 10 ³ [var]
= 500 [kvar]
Capacity is required.

Here, the reactive power generated by the electric motor can be calculated by the following equation (3).
Q ′ = P × sin θ (3)
Here, Q ′ is the reactive power [var] generated by the motor, P is the apparent power [VA] of the motor, and sin θ is calculated from the power factor of the motor (θ = cos ⁻¹ θ).

Therefore, the reactive power generated by the motor of this example is
Q ′ = 500 × 10 ³ × 0.6
= 300 × 10 ³ [var]
= 300 [kvar]
Is calculated. That is, the voltage drop value resulting from the reactive power is 3% from the term (% X × sin θ) in the above equation (1).

  In other words, in the above example, the phase-advancing capacitor capacity that should be input by the voltage fluctuation compensator in the steady operation state of the motor is almost unchanged, but the motor is generated to compensate for the voltage drop in the distribution line. It must be in an advanced phase state that exceeds the active reactive power by 200 kvar. This is because it is necessary to input 200 kvar to compensate for the voltage drop of 2% caused by the active power.

On the other hand, when the voltage drop value ΔV at the time of starting the motor is an apparent power P = 1,500 kVA and a power factor of 0.6,
ΔV = 1,500 × 10 ³ × (50 × 0.6 + 100 × 0.8) / (10 × 10 ⁶ )
= 16.5 [%]
Is calculated.

Therefore, if the voltage drop at startup is compensated with a phase advance capacitor,
ΔV _UP = Q ×% X / (10 × 10 ⁶ ) = 16.5 [%]
Q = 16.5 × (10 × 10 ⁶ ) / 100 = 1,650 × 10 ³ [var]
= 1,650 [kvar]
Capacity is required.

  In summary, for example, in the motor described above, a voltage fluctuation compensator having a phase advance capacitor capacity of 1,650 kvar is required to compensate for the voltage drop that occurs during startup and in the steady operation state (per motor). )

  However, it is customary to install a plurality of pump motors installed in a pumping station. For example, in a pumping station where three motors are installed, if a voltage fluctuation compensator is installed in each motor, the total capacity A total of 1,650 × 3 = 4,950 kvar is a facility having a huge phase-advancing capacitor capacity.

  Moreover, even if a condition that a plurality of pump motors do not start at the same time is given, for example, if there are three pump motors, the maximum voltage fluctuation is one in two steady state motors. In order to compensate for this occurring under start-up conditions, a facility having a phase advance capacitor of 500 × 2 + 1, 650 = 2, 650 kvar and a huge capacity is required.

Here, in the voltage fluctuation compensator using the above-described capacitor switching control system, the capacitors are divided into a plurality of capacitance groups and, for example, weights of 1, 2, 4, and 8 are given to the capacitors, so that there are 15 levels of combinations of four capacitor groups. Control (4 group 15 stage control) can be performed, thereby reducing the number of groups of capacitors and the number of open / close switches of the capacitor current rather than turning on / off the capacitor capacity one step at a time by a semiconductor switch (FIG. 5). reference). For example, when 4 groups and 15 stages are controlled by weighting 1, 2, 4, and 8, for example, the number of open / close switches for the capacitor current is only four, but in the case of 15 stages of equal capacity control, 15 are required. As the number of circuits around the switch increases, it is obvious that the cost increases.
However, under such a configuration, when the total capacitance of the capacitor increases, the capacitor current of a circuit with a large weight increases, and the semiconductor switch that opens and closes becomes expensive or difficult to obtain.

For example, in the case of a 15-stage control capacity of 2,700 kvar, which is close to 2,650 kvar, if it is divided into four groups while weighting, it becomes a capacity group of 180/360/720/1, 440 kvar, respectively. A semiconductor switch capable of opening and closing 1,440 kvar becomes difficult to obtain or very expensive.
Japanese Patent Laid-Open No. 9-191576

  Accordingly, the present invention relates to a voltage fluctuation compensator that solves the above problems and is electrically connected to at least one motor load and compensates for voltage fluctuations that occur in the distribution line when the motor is started. It is an object to provide a new system that realizes voltage fluctuation countermeasures in space.

As a result of various studies to solve the above problems, the present inventor has found that the above problems can be solved by using a voltage fluctuation compensator having the following configuration, and has completed the present invention.
The present invention receives a start signal output from the motor control device for a period from immediately before the start of the start after the motor current actually flows and until the start of the start and the transition to the steady operation state. Control means with a subtractor circuit that subtracts the required number of advanced phase capacitor input stages calculated by the capacitor input stage number calculation circuit at the time of start-up every one time sequentially (or multiple stages) With
As a result, every time after start-up, the phase-advancing capacitors that were turned on are turned off sequentially, and finally the amount of phase-advancing capacitors charged is reduced to zero, so that multiple motors can be The present invention provides a voltage fluctuation compensator that can be handled with a compensation capacity of one unit. According to the present invention, it is possible to realize a countermeasure for voltage fluctuation at a lower cost and a smaller space.
Here, since the amount of phase-advancing capacitor input decreases by one stage (or a plurality of stages), the voltage fluctuation generated in the distribution line does not become a large value, and the influence on other customers is small. In addition, the voltage drop that occurs during steady operation gradually increases as the amount of phase-advancing capacitor in the voltage fluctuation compensator decreases, but the power company distribution line compensates for voltage fluctuation caused by steady load capacity, It is customary to install an automatic voltage regulator to supply at a constant voltage, and to reduce the amount of phase-advancing capacitor input to the voltage fluctuation compensator at intervals where the installed automatic voltage regulator can respond. In this case, it can be expected that the voltage fluctuation is automatically adjusted.

The voltage fluctuation compensator of the present invention that can solve the above-mentioned problems is (1) a voltage fluctuation compensator that is electrically connected to at least one motor load and compensates for voltage fluctuations that occur in a distribution line when the motor is started. Because
An instrument transformer for detecting the voltage of a distribution line electrically connected to the motor load, a current transformer for detecting a load current, a shunt connected in series with a series reactor, a semiconductor switch, and a phase advance capacitor. A phase advance capacitor circuit connected in parallel with the electric motor load, and a control means for outputting a signal for turning on / off a semiconductor switch of the phase advance capacitor circuit;
Consists of
The control means calculates a compensation value corresponding to a voltage fluctuation value generated in the distribution line from outputs of the instrument transformer and the current transformer, and an output from the compensation value detector A capacitor input stage number calculation unit that calculates the required number of phase advance capacitor input stages according to the condition, and a start signal reception that is electrically connected to the capacitor input stage number calculation unit and that receives the start signal output during the start-up period of the motor And the start signal receiving unit, and each time a predetermined time elapses from the end of the start signal of the motor, the necessary number of phase-advancing capacitor input stages is sequentially subtracted by one stage or a plurality of stages. A subtracting unit that performs a turn-on and a signal for turning on / off the semiconductor switch in response to an output from the subtracting unit.

  The voltage fluctuation compensator according to the present invention relates to the voltage fluctuation compensator of (1) above, and (2) the compensation value is calculated by calculating active power and reactive power generated in the motor load. It is a feature.

In this specification, “start-up” refers to the period from immediately before the start of start-up after the motor current has actually flowed to the point in time when the start-up ends and the state shifts to a steady operation state.
“Startup signal” refers to a signal that is output from the motor control device during the period from when the motor current actually flows out and immediately before the start of the start until the end of the start and the transition to the steady operation state And Further, a period from the start of outputting the start signal to the end is referred to as a start period.
“Subtraction trip” refers to an operation of turning off a phase advance capacitor that has been turned on sequentially by opening and closing a semiconductor switch every time after start-up based on the output from the subtraction circuit. Shall.
The “load power calculation period” refers to a period from the time when the output of the start signal is started until the time when the subtraction of the phase advance capacitor is completed after the transition to the steady state.

According to the present invention, by using the start signal output from the control device for the motor for the pump, after the start of a certain motor, the phase-advancing capacitors that are being charged in a steady state are sequentially turned off, and finally the number of capacitors to be charged The phase-advancing capacitor circuit having the compensation capacity for one motor used for starting this motor is set to a state where it can be operated as if it is a compensator dedicated to that motor when another motor is started. It is possible to provide a voltage fluctuation compensator that enables this. That is, according to the present invention, it is possible to provide a voltage fluctuation compensator capable of handling a plurality of electric motors with a compensation capacity for one unit.
As described above, according to the present invention, it is possible to provide a novel system that realizes a countermeasure against voltage fluctuation at a lower cost and in a smaller space.

Hereinafter, an embodiment of a voltage fluctuation compensator according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a control block diagram for explaining an embodiment of the present invention, FIG. 2 is a time chart showing a control sequence of an embodiment of the present invention, and FIG. It is a figure explaining the state installed in the water pump station provided with the electric motor. It should be noted that the same reference numerals are assigned to the same components as those described in the prior art section.
In this embodiment, a three-phase induction motor is used as the pump motor, and its activation is performed by a known condorfa method as shown in FIG.

[Constitution]
First, a schematic configuration of the voltage fluctuation compensator according to the present embodiment will be described with reference to FIG.
As shown in FIG. 1, the voltage fluctuation compensating apparatus 10 according to the present embodiment includes an instrument transformer 1 that detects a voltage of a distribution line, a current transformer 2 that detects a current flowing through a motor for a pump M, and the above-described instrument. Compensation value detection for calculating the compensation value corresponding to the voltage fluctuation value that can be generated in the distribution line in response to the output of the transformer 1, the output of the current transformer 2, and the start signal 3 output from the pump controller MC The circuit 4, the capacitor input stage number calculating circuit 5 for calculating the required number of phase advance capacitor input stages from the compensation value, and the start signal 3 output from the pump control device MC are received, and an arbitrary time from the end of the start signal , The activation signal reception and subtraction circuit 6 that sequentially subtracts the required number of advance phase capacitor input stages previously obtained, and the semiconductor switch according to the output from the activation signal reception and subtraction circuit 6 A closing command circuit 7 for creating a closing signal, and a phase advance capacitor including a plurality of shunts each including a semiconductor switch 11, a series reactor 12, and a phase advance capacitor 13 connected in series, and connected in parallel with the motor load. The circuit 8 is composed of shunts 8a to 8d. In the present embodiment, the compensation value detection circuit 4, the capacitor input stage number calculation circuit 5, the start signal reception and subtraction circuit 6, and the input command circuit 7 constitute the control means 9. Moreover, in this embodiment, the phase advance capacitor circuit 8 is comprised by 4 groups, and has shunt 8a-8d.

As shown in FIG. 1, in this embodiment, when the start signal 3 is output from the control device MC for the motor for the pump M, the start signal 3 is received by the start signal receiving and subtracting circuit 6 and then the compensation value is detected. Input to the circuit 4.
Here, as shown in FIG. 2, the start signal 3 is output from the pump control device MC immediately before the current actually flows through the pump M motor. In the control means 9 according to the present embodiment, the calculation process is performed immediately after obtaining the start signal 3, and the effective power generated by the pump M motor before the current actually flows to the pump M motor, The reactive power detection circuit (compensation value detection circuit) is activated (see the sequence of FIG. 2 and the description of the subsequent stage). As described above, according to the present embodiment, the start signal 3 output from the pump control device MC is used to detect the active power and reactive power generated by the pump M motor during the start-up period, and the pump start-up. The voltage drop at the time can be reliably suppressed.

[Operation]
Next, the operation of the voltage fluctuation compensator of the present embodiment having the above configuration will be described. Hereinafter, the description will proceed under the condition that a plurality of pumps are not started simultaneously.
First, when the activation signal 3 is output from the control device MC of the pump M, the control means 9 receives this signal by the activation signal reception and subtraction circuit 6 as described above, and then the activation signal 3 is received by the compensation value detection circuit 4. To enter. As shown in FIG. 2, the start signal 3 is output from the pump control device MC until the transient state at the start of the pump ends and the state shifts to a steady state.
The compensation value detection circuit 4 receives the activation signal 3 and calculates a necessary compensation value corresponding to the voltage fluctuation value generated in the distribution line from the output of the instrument transformer 1 and the output of the current transformer 2. The obtained compensation value is sent to the capacitor input stage number calculation circuit 5. The capacitor input stage number calculation circuit 5 calculates the required number of phase advance capacitor input stages based on the obtained compensation value.

Here, the voltage drop value ΔV generated when the motor is in operation, the voltage rise value ΔV _{UP at} the phase advance capacitor, and the phase advance capacitor capacity Q, which are necessary to obtain the compensation value and the required number of stages of phase advance capacitor, are required. As for the calculation method, etc., the above formulas (1), (2), etc. shown in the column of the prior art can be used as appropriate.
Note that, under the condition that a plurality of pumps are not started simultaneously, the apparent power P, voltage drop value ΔV, voltage rise value ΔV _UP in the phase advance capacitor, related to one pump motor (during start-up and steady state), Since each value such as the phase advance capacitor capacity Q and the power factor of the motor (see the column of the prior art) can be predicted, these values are stored in advance in a memory (not shown) provided inside or outside the control means 9. Alternatively, the output of the capacitor input stage number calculation circuit 5 may be obtained while referring to the memory as soon as the activation signal 3 is detected.
In addition, in obtaining the above compensation value and the required number of phase-advancing capacitor input stages, first, the active power and reactive power generated in the pump motor are calculated, and then the above compensation based on the mathematical formula shown in the column of the prior art. It may be configured to obtain the value and the required number of phase advance capacitor input stages.

  At the time of start-up, if the required number of phase advance capacitor input stages is obtained, a switch opening / closing signal is transmitted directly from the input command circuit 7 to each semiconductor switch 11 in order to input the required number of capacitors based on that. The

  When the transient state at the start of the pump ends and the start signal 3 output from the pump control device MC ends, the start signal receiving and subtracting circuit 6 next every time an arbitrary time elapses from the end of the start signal. Then, a process of sequentially subtracting the necessary number of phase advance capacitor input stages calculated previously is performed.

As described above, in the general configuration known in the art, the voltage drop caused by the substantially constant active power and reactive power generated after the motor enters the steady operation state is changed to the voltage when the motor is stopped. In order to compensate, the phase advance capacitor is continuously turned on after the transition to the steady state to keep the state of the over advance phase.In the present invention, the control means for calculating the capacitor capacity to compensate for the voltage drop is provided, and the start signal At the end, it was started to forcibly subtract the phased capacitor input capacity step by step. By subtracting one stage (or multiple stages) after an arbitrary time (for example, 1 minute) from the number of input capacitor stages, and gradually turning off the capacitor being input, the amount of capacitor input is finally reduced to zero. To decrease.
As shown in FIG. 2 as the load power calculation period, in the present invention, the control means 9 actually controls the distribution line voltage and the load current from the start of output of the start signal 3 to the phase advance capacitor after the transition to the steady state. This is the time until the subtraction trip is completed.

  By the way, also in the case of the present invention, immediately after the transition to the steady state, in order to compensate for the almost constant voltage drop that occurs after the motor transitions to the steady operation state, the phase advance capacitor is continuously maintained to enter the overrun state. However, the number of advanced phase capacitor input stages at this time is significantly smaller than the number of advanced phase capacitor input stages required at startup.

  Therefore, even if the number of input stages is subtracted by one stage at regular intervals after the start signal is finished, the amount of phase advance capacitor input can be reduced to zero in a short time. In other words, the waiting time when starting another motor after the start of a specific motor is not long.

  In the present embodiment, the amount of phase-advancing capacitor input decreases by one stage, so that the voltage fluctuation generated in the distribution line does not become a large value, and the influence on other consumers is small. In addition, the voltage drop that occurs during steady operation gradually increases as the amount of phase-advancing capacitor in the voltage fluctuation compensator decreases, but the power company distribution line compensates for voltage fluctuation caused by steady load capacity, It is customary to install an automatic voltage regulator to supply at a constant voltage. If the installed automatic voltage regulator reduces the amount of phase-advancing capacitor input in the voltage fluctuation compensator at an interval at which it can respond. In this case, it can be expected that the voltage fluctuation is automatically adjusted.

In the case of the electric motor according to the above-described example (see the column of the prior art), among the 1,650 kvar of voltage fluctuation compensator capacity required for one electric motor, the required capacitor input amount during steady operation is 500 kvar, In the case of 15-stage control (when capacity of 1, 2, 4, and 8 is weighted, it becomes a capacity group of 110/220/440/880 [kvar], respectively), the phase advance capacitor capacity 550 kvar closest to this Is equivalent to 5 stages, so the amount of phase-advancing capacitor input becomes zero by 5 stages of subtraction, and even if the subtraction is performed every minute, the subtraction trip is completed in 5 minutes after the start-up.
When the calculation is performed under the above-described conditions, the steady operation is 500 kvar and the startup is 1,650 kvar. When the conventional control is performed, the three pumps require 2,650 kvar. When this is the control method of the present invention, it may be 1,650 kvar of only the voltage fluctuation compensation capacity generated when one pump is started. When the phase advance capacitor capacity is 2,650 kvar, the maximum capacity when the four-group 15-stage control is configured is 1,440 kvar in the conventional example, but in the present invention, it is 880 kvar, which is about 60% of the capacity of the conventional example. As a result, products for general industries can be applied.

As described above, according to the present embodiment, the start-up signal output from the motor control device is used to sequentially turn off the phase-advancing capacitors that are being turned on in a steady state after the start-up of one motor. Finally, the number of input capacitors can be reduced to zero, so that a phase-advancing capacitor circuit having a compensation capacity for one motor used for starting the motor in a steady state can be used when starting another motor. It is possible to provide a voltage fluctuation compensator that can be operated as if it were a compensator dedicated to the electric motor.
Therefore, it can be seen that according to the present invention, it is possible to provide a voltage fluctuation compensator capable of handling a plurality of electric motors with a compensation capacity for one unit.

Below, the example which applied the voltage fluctuation compensation apparatus of this invention which has the above-mentioned control system, and actually comprised the pumping-station facility which has the three motors for pumps is demonstrated. FIG. 3 shows an embodiment of a pumping station facility to which the voltage fluctuation compensator of the present invention is applied. Also in this embodiment, the control sequence shown in FIG. 2 is similarly applied. In the configuration shown in FIG. 3, the control unit 9 described above with reference to FIG.
In this embodiment, no. 1-No. Each of the three motors for pumps M1 to M3 uses a three-phase induction motor, and its activation is performed by a known condorfa method as shown in FIG.

  In FIG. 1-No. 3 are provided with current transformers 2 for detecting motor currents for each of pumps M1 to M3, and share voltage transformer 1 for voltage detection of distribution lines, and output from pump control devices MC1 to MC3, respectively. The pump start signal 3 is supplied to the control means 9 of the voltage fluctuation compensation device 10. In addition, the transformer T shown in the figure is generally provided when a distribution line is drawn from the off-site high voltage receiving point to the pumping station yard. A phase advance capacitor circuit 8 shown in the drawing includes a semiconductor switch 11, a series reactor 12, and a phase advance capacitor 13 connected in series, and a plurality of components connected in parallel to the motors for the pumps M1 to M3. It consists of roads (8a-8d). Also in this embodiment, the phase advance capacitor circuit 8 is composed of four groups. Reference numeral 14 in the figure is a known circuit breaker.

The operation of the voltage fluctuation compensator of the present example having the above configuration is basically the same as that described in the above embodiment. Under the condition that a plurality of pumps are not started simultaneously, when a start signal is output from any of the control devices MC1 to MC3 of the pumps M1 to M3, the control means 9 first receives this signal. And the subtraction circuit 6 receives the start signal 3 to the compensation value detection circuit 4. In this embodiment as well, the start signal 3 is output from the pump control device until the transitional state at the time of starting the pump ends and shifts to a steady state (see FIG. 2).
The compensation value detection circuit 4 receives the start signal 3 and calculates a necessary compensation value corresponding to the voltage fluctuation value that can be generated in the distribution line from the output of the instrument transformer 1 and the output of the current transformer 2. The obtained compensation value is transmitted to the capacitor input stage number calculation circuit 5. The capacitor input stage number calculation circuit 5 calculates the required number of phase advance capacitor input stages based on the obtained compensation value.
Here, the voltage drop value ΔV generated when the motor is in operation, the voltage rise value ΔV _{UP at} the phase advance capacitor, and the phase advance capacitor capacity Q, which are necessary to obtain the compensation value and the required number of stages of phase advance capacitor, are required. As for the calculation method, etc., the above formulas (1), (2), etc. shown in the column of the prior art can be used as appropriate.

  In the present embodiment, the compensation value and the necessary number of phase advance capacitor input stages are calculated in the specific manner described below.

First, when the pump motor is started, a voltage drop ΔV obtained from the above equation (1) is generated. At this time, the voltage drop ΔV is calculated by calculating the active power W and the reactive power Q ′ of the motor from the pump current and the circuit voltage.
In this embodiment, a method is adopted in which the total voltage drop due to the active power and reactive power shown in the above equation (1) is compensated by the phase advance reactive current supplied from the phase advance capacitor. That is, in this embodiment, since the voltage drop at the time of start-up is compensated by inserting the phase advance capacitor, the voltage drop value ΔV in the above equation (1) immediately corresponds to the voltage rise value ΔV _UP in the phase advance capacitor. Become.
Accordingly, the compensation value detection circuit 4 calculates the voltage drop value ΔV or the voltage rise value ΔV _UP at the phase advance capacitor as the compensation value.
The voltage drop in equation (1) is the sum of the P × cos θ ×% R (active power) term and the P × sin θ ×% X (reactive power) term. The method of calculating active power and reactive power from the input voltage and current is already used in another device or a conventionally known voltage fluctuation compensator, and the voltage fluctuation compensator of the present invention also calculates the power by the same method. The voltage drop can be obtained by multiplying the impedance.

Here, by using the fact that the voltage increase value ΔV _UP in the phase advance capacitor is obtained from the above equation (2), it is possible to calculate the phase advance capacitor capacity and the number of phase advance capacitor input stages required at the time of startup. Therefore, the capacitor input stage number calculation circuit 5 calculates the phase advance capacitor capacity and the phase advance capacitor input stage number required at the start-up by the above compensation value and the above equation (2).

  At the time of start-up, if the required number of phase advance capacitor input stages is obtained, a switch open / close signal is directly sent from the input command circuit 7 to each semiconductor switch 11 in order to input the required number of phase advance capacitors based on that. Sent.

Here, the introduction of the phase advance capacitor corresponds to giving a voltage increase due to the phase advance current.
Thus, according to the present embodiment, the voltage drop ΔV shown in the above equation (1) can be compensated by the phase advance current flowing in the phase advance capacitor.

  When the transient state at the time of starting the pump ends and the start signal 3 output from the pump control device ends, next, in the start signal reception and subtraction circuit 6, every time an arbitrary time elapses from the end of the start signal, A process of sequentially subtracting the necessary number of phase advance capacitor input stages calculated previously is performed. In the closing command circuit 7, a semiconductor switch 11 opening / closing signal is generated in response to the start signal reception and the output from the subtracting circuit 6, and the phase advance capacitor that has been turned on even in the steady state is supplied from the closing command circuit 7. It is sequentially turned off based on the command (subtraction tripping). The number of input capacitors finally becomes zero as shown in FIG.

  Referring to FIG. 4 relating to the conventional example in which a dedicated phase advance capacitor circuit is provided for each pump motor, also in FIG. 4, each of the current transformers 2 for detecting the motor current for each of the pumps M1 to M3 is shown. This is the same as the present embodiment in that it is provided and the voltage transformer 1 for voltage detection of the distribution line is shared. However, the control system of the voltage fluctuation compensator 50 according to the conventional example does not use the pump start signal, and each control system provided for each pump motor is advanced as long as the pump is operating. This is different from the case of the present embodiment in that the phase capacitor is continuously put on.

  According to the time chart for turning on / off the phase advance capacitor in this embodiment shown in FIG. 2, in this embodiment, the amount of phase advance capacitor input is increased by one stage every time a predetermined time (1 minute) has elapsed from the end of startup. Is decreasing.

  On the other hand, in the case of the conventional example shown in FIG. 5, the introduction of the phase advance capacitor at the time of start-up is the same as that of the present embodiment, but the phase advance capacitor continues to compensate for the voltage drop that occurs in the steady operation state after the start-up. The input is maintained.

According to the present embodiment, after the start-up of one pump (for example, No. 1 pump) and after completion of subtraction of the capacitor (see FIG. 2), the phase advance capacitor circuit 8 shown in FIG. It can be used to start a pump (for example, No. 2 or later). The start sequence of the pumps that are started after the second time is the same as that of the pump that is started first.
Thus, under the condition that a plurality of pumps are not started simultaneously, the phase advance capacitor circuit 8 can be configured with a capacity of one unit, and the voltage fluctuation compensator according to the present embodiment is cost-effective and space-saving. This is very advantageous.

[Modification]
Although the present invention has been specifically described with reference to one embodiment and the like, the present invention is not limited to the configuration described in the embodiment and the like, and various design changes are possible.

  For example, in the above embodiment, the phase advance capacitor circuit 8 is configured with a capacity of one unit, but a capacity may be appropriately provided for the capacitor capacity. As a result, even after one motor has shifted to the steady operation state, the third motor is being put into the second motor even when the second motor is sequentially turning off the phase-advancing capacitor. It becomes possible to start up before the capacitor capacity becomes zero.

The use to which the present invention is applied is not limited to the pumping station. The present invention can be easily applied to equipment in which a plurality of inductive loads such as electric motors are connected in parallel.
The type of pump motor is not limited to a three-phase induction motor, and the start-up method is not limited to the condorfa method mentioned in the above example, and a known starting method may be used singly or in combination. Is possible.

In terms of the number of capacitor stages to which the subtraction and removal are sequentially performed after the transition to the steady state, the number of stages is one in each of the above examples, but depending on the capability of the automatic voltage regulator provided on the system side, etc. It is also possible to adopt a configuration in which the subtraction is deducted.
In the above examples, the time interval for performing the subtraction / deduction is also set to, for example, every minute. However, it is not necessary to set the time interval to be strictly constant, as long as an operation is performed every time an arbitrary time elapses. That's fine.
The specific calculation procedure of the compensation value or the necessary number of phase advance capacitor input stages is not limited to the one described in each of the above examples, and a known method can be appropriately employed.

  As described above, the present invention is not limited to the configurations described in the above embodiments and the like, and those skilled in the art can devise various modifications based on the basic technical idea and teachings disclosed above. Is self-explanatory.

  As described above, the present invention relates to a voltage fluctuation compensator that is electrically connected to at least one motor load and compensates for voltage fluctuation generated in a distribution line when the motor is started up. It is clear that the present invention is a new and useful one that provides a voltage fluctuation compensation system that can cope with the compensation capacity of a unit, thereby realizing a voltage fluctuation countermeasure at a low cost and in a space-saving manner.

It is a control block diagram explaining one Embodiment of this invention. It is a figure which shows the time chart showing the control sequence of one Embodiment of this invention. It is a figure explaining the state which installed this invention apparatus in the pumping-up station provided with the three electric motors for pumps. It is a figure which shows the mode of the conventional apparatus which installs a voltage fluctuation compensation apparatus for every electric motor for pumps. It is a time chart in the conventional Example.

Explanation of symbols

M, M1 to M3 Pump MC, MC1 to MC3 Pump control unit T Transformer 1 Instrument transformer 2 Current transformer 3 Start signal 4 Compensation value detection circuit 5 Capacitor input stage number calculation circuit 6 Start signal reception and subtraction circuit 7 Input command Circuit 8 Phase advance capacitor circuit 8a to 8d Shunt 9 Control means 10 Voltage fluctuation compensator 11 Semiconductor switch 12 Reactor 13 Phase advance capacitor 14 Breaker 50 Voltage fluctuation compensator

Claims (2)

A voltage fluctuation compensator that is electrically connected to at least one motor load and compensates for voltage fluctuations that occur in a distribution line when the motor is started,
An instrument transformer for detecting a voltage of a distribution line electrically connected to the motor load;
A current transformer for detecting the load current;
Including a plurality of shunts in which a series reactor, a semiconductor switch, and a phase advance capacitor are connected in series, and a phase advance capacitor circuit connected in parallel with the motor load;
Control means for outputting a signal for turning on / off the semiconductor switch of the phase advance capacitor circuit;
Consists of
The control means is
A compensation value detection unit that calculates a compensation value corresponding to a voltage fluctuation value generated in the distribution line from outputs of the instrument transformer and the current transformer;
A capacitor input stage number calculation unit that calculates the number of phase advance capacitor input stages required according to the output from the compensation value detection unit;
An activation signal receiving unit that is electrically connected to the capacitor input stage number calculation unit and receives an activation signal output during an activation period of the electric motor;
A subtraction that is electrically connected to the start signal receiving unit and sequentially subtracts the required number of phase-advancing capacitor input stages by one stage or multiple stages each time an arbitrary time elapses from the end of the start signal of the motor. And
An input command unit that outputs a signal for turning on / off the semiconductor switch according to an output from the subtracting unit,
A voltage fluctuation compensation device comprising:   The voltage fluctuation compensation apparatus according to claim 1, wherein the compensation value is calculated by calculating active power and reactive power generated in the motor load.

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