JP2006146525A - Power supply and method for compensating load voltage of power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the responsiveness and accuracy of voltage control at the load end of a power supply to which a load 2 is connected from a voltage source 1 via circuit elements such as reactors. <P>SOLUTION: A voltage variation that arises at the circuit elements R, jX intervening between the voltage source and the load is computed by a compensation computing part 8 on the basis of their circuit constants and the output current of the voltage source and is added to the voltage command value V<SB>L</SB>* of the voltage source and the load voltage is held constant by feed forward. If a load current varies suddenly, a current similar to the present load current, such as a current waveform of the last cycle, is used in place of the current waveform that appears during the sudden variation, for a short period of time until the load current is stabilized, so as to hold the load current constant. Combining these methods with a conventional method of load voltage feedback is also proposed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power supply apparatus having an output voltage control function, and more particularly to a power supply apparatus in which a circuit element such as a reactor is interposed between a load and a load voltage compensation method thereof.

  A path from the output end to the load in a power supply device (hereinafter referred to as voltage source) that can supply AC power or DC power to the load with a voltage control function, such as a voltage source inverter or converter that controls the output voltage constant or variable In some cases, circuit elements such as a power cable, a transformer, a reactor, a capacitor, and a resistor are interposed. In addition to the linear element such as the power cable, the circuit element may be interposed as a nonlinear characteristic of the load. Such power supply devices are found in, for example, uninterruptible power supply devices, instantaneous voltage drop compensation devices, and the like.

  In the voltage source in which the circuit element as described above is interposed between the load and the circuit constant (reactance or resistance) of the circuit element and the voltage change due to the load current appears in the load end voltage, the voltage accuracy is low as viewed from the load. Become a voltage source. Therefore, in order to obtain a load voltage that matches the voltage command value of the voltage source, a method of detecting the load voltage and performing feedback control has been proposed (see, for example, Patent Document 1).

  In Patent Document 1, AC power is supplied to a load by a power conversion device composed of a converter and an inverter, and the output voltage matches a target value by controlling the DC side voltage (smoothing capacitor voltage) of the inverter for load voltage control. In this configuration, when the DC side voltage changes due to disturbance, the product of the DC voltage differential value (ΔV / Δt) and the capacitor capacitance C is calculated, and this is added to the DC voltage control signal to thereby calculate the load end voltage. To compensate for changes in

  As another load voltage compensation method, a method combining a feedforward method has also been proposed (for example, see Patent Document 2). In Patent Document 2, a reactive power compensator is connected to an electric power system, and in an apparatus that performs feedback control to the reactive power compensator so as to cancel the deviation between the system voltage and a set voltage, the influence on the system voltage due to a change in load current is described. Mitigates with feedforward control.

  As described in Patent Document 1, the load voltage correction control by feedback control for directly compensating the load voltage basically has the configuration shown in FIG.

In the figure, power is supplied from a voltage source 1 to a load 2, and the voltage source 1 is a device that controls an AC output voltage having a waveform that matches the voltage command (AC signal) V _L * of the voltage setter 3. In order to compensate for the change of the load voltage due to the circuit constants R and jX of these circuit elements, a transformer or a reactor is interposed between the load 2 and the load 2, and the load voltage is detected, and the detected voltage and the voltage command V _L * Is obtained by the comparator 4 and amplified by the amplifier 5 as a voltage command value of the voltage source 1.
JP 2004-153978 A JP 2001-268796 A

  In the power supply device having the configuration of FIG. 4, when a load current flows, the load voltage decreases with circuit constants R and jX possessed by circuit elements such as a transformer and a reactor. Furthermore, the load voltage also changes due to the change in the load current. For this reason, if the voltage source 1 is controlled to be the target value by feeding back the load voltage detection signal, it takes time until the load voltage reaches the target value because there is a delay in voltage detection and output control. (Decrease in responsiveness).

  When the gain of the voltage control amplifier is increased in order to reduce the control delay, the voltage change in the jX term becomes very large when the load operating state is changed and the load current changes suddenly. Actually, since there is a delay from the detection of the load voltage to the voltage output of the voltage source, the voltage output of the voltage source and the load current oscillate with each other due to the voltage change in the jX term, which may cause unstable control. Or it takes time until the load current settles to a steady state.

  In the method of Patent Document 2 in which a change in load voltage due to a change in load current is compensated by a feedforward method, the same problem remains because the load voltage is feedback-controlled.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply apparatus capable of compensating for a load end voltage by improving stability and responsiveness to a load current and its sudden change, and a load voltage compensation method thereof.

  In the present invention, the amount of voltage change generated by a transformer, a reactor or the like interposed between the voltage source and the load is obtained by calculation from the circuit constants and the output current of the voltage source, and this is used as the voltage command value of the voltage source. In addition, keep the load voltage constant by feed-forward, and if the load current suddenly changes, the current waveform one cycle before instead of the current waveform at the time of sudden load change, etc. for a short time until the load current settles The load voltage is kept constant by using a current similar to the current load current, and these methods are combined with the conventional load voltage feedback method, and the following devices and methods are characterized.

(1) A power supply device in which a load is connected from a voltage source via a circuit element such as a reactor, and the output voltage of the voltage source is controlled in accordance with a voltage command from a voltage setter to supply voltage-controlled power to the load. And
A current detector for detecting an output terminal current of the voltage source as a load current;
A compensation amount calculation unit for obtaining a voltage change generated in the circuit element from the constant of the circuit element and the load current;
And an adder that adds the voltage change to the voltage command of the voltage setter to obtain a voltage command of the voltage source.

(2) a dead time generator for obtaining an output obtained by delaying the detection current of the current detector by a fixed period or a fixed time;
A load current sudden change detector that detects a sudden change in load current when a load current sudden change occurs or is predicted on the load side; and
And a changeover switch that switches the output of the dead time generator as a load current detection input of the compensation amount calculation unit for a predetermined time when the load current sudden change detector detects a sudden change in load current. .

(3) a voltage detector for detecting the voltage at the load end;
And a load voltage control circuit using a load voltage control signal corresponding to a deviation between a detection voltage of the voltage detector and a voltage command of the voltage command generator as an addition input of the adder.

(4) A load of a power supply apparatus, in which a load is connected from a voltage source through a circuit element such as a reactor, and the output voltage of the voltage source is controlled in accordance with a voltage command from a voltage setting device to supply voltage-controlled power to the load A voltage compensation method comprising:
The current detector detects the output terminal current of the voltage source as a load current,
The compensation amount calculation unit obtains a voltage change generated in the circuit element from the constant of the circuit element and the load current,
The adder adds the voltage change to the voltage command of the voltage setting device to obtain a voltage command of the voltage source.

(5) The dead time generator obtains an output obtained by delaying the detection current of the current detector by a fixed period or a fixed time,
A sudden change in load current is detected when a sudden change in load current occurs or is predicted on the load side,
The changeover switch is characterized in that when the load current sudden change detector detects a sudden change in load current, the output of the dead time generator is switched for a predetermined time as a load current detection input of the compensation amount calculation unit.

(6) The voltage detector detects the voltage at the load end,
The load voltage control circuit is characterized in that a load voltage control signal corresponding to a deviation between a detection voltage of the voltage detector and a voltage command of the voltage command generator is used as an addition input of the adder.

  As described above, according to the present invention, the amount of voltage change generated by a transformer, a reactor, or the like interposed between the voltage source and the load is obtained from the circuit constants and the output current of the voltage source, and this is calculated. Since the load voltage is kept constant by feedforward in addition to the voltage command value of the source, the voltage generated in the transformer and reactor can be obtained instantaneously, and a high-speed response can be expected. Further, the load voltage can be kept constant regardless of the load current without creating a load voltage feedback loop. The same control is possible even when a non-linear load is connected.

  In addition, when the load current changes suddenly, the load voltage is measured using a current similar to the current load current, such as the current waveform one cycle before, instead of the current waveform at the time of sudden load change until the load current settles. If the load current changes abruptly, such as when the switch is turned on or off, and the voltage change becomes very large, the load voltage is calculated by using the load current that is expected to flow in advance. Can be shortened to reach the command value.

  In addition, by combining the above load voltage compensation method with the conventional load voltage feedback method, the output voltage can be matched with the voltage command even when there are changes or errors in parameters such as R and jX, resulting in high responsiveness. And can ensure accuracy.

(Embodiment 1)
FIG. 1 is a circuit configuration diagram of a power supply device according to the present embodiment, and the same parts as those in FIG. 4 are denoted by the same reference numerals.

In FIG. 1, a current detector 7 detects a load current I at the output terminal of the voltage source 1. The compensation amount calculation unit 8 obtains the current voltage change due to the circuit element interposed between the voltage source 1 and the load 2 and the load current I flowing therethrough. In the figure, circuit constants (resistance component R and reactance component jX) of a circuit element interposed between the voltage source 1 and the load 2 are preset in the multipliers 8A and 8B, and these are multiplied by the detected load current I. The voltage change I (R + jX) is obtained by adding both outputs by the adder 8C. The adder 6 adds the voltage change I (R + jX) obtained by the compensation amount calculation unit 8 to the voltage command V _L * of the voltage setter 3.

With the above configuration, the output voltage of the voltage source 1 becomes a value obtained by adding the voltage change I (R + jX) to the voltage command V _L *, and this voltage is generated by a circuit element interposed between the voltage and the load. The voltage that is reduced by the voltage change is the load end voltage, and this load end voltage can always be kept equal to the voltage command V _L *.

  According to the present embodiment, the amount of voltage change generated in a circuit element such as a transformer or a reactor interposed between the voltage source 1 and the load 2 is obtained in advance as the load current I detected at the output terminal of the voltage source 1. By calculating from the circuit constants (R, jX) to be placed and adding this to the voltage command value of the voltage source 1, the voltage source output is controlled in a feedforward manner for the load, and the load voltage is kept constant. This makes it possible to perform load voltage compensation with reduced delay in load voltage detection and output control generated in a transformer or reactor as compared with a conventional load voltage feedback system, and high response to load voltage compensation can be expected.

(Embodiment 2)
FIG. 2 is a circuit configuration diagram of the power supply device according to the present embodiment, and parts equivalent to those in FIG. 1 are denoted by the same reference numerals.

  In FIG. 2, a dead time generator 9 receives a detection signal of the load current I and obtains an output in which a dead time is generated with the AC output cycle of the voltage source 1 as T for this load current. For example, the dead time generator 9 obtains a load current waveform obtained by delaying the load current I by one cycle (or several cycles). When the voltage source 1 is a DC power source that supplies DC power to the load 2, a load current detection value (DC value) obtained by delaying the detection signal of the load current I for a predetermined time is obtained.

  The change-over switch 10 uses the detection output of the current detector 7 as an input to the compensation amount calculation unit 8 in a steady state, and detects this sudden change in load current when the load current suddenly changes or is predicted on the load side. In response to the detection signal (ON / OFF) of the load current sudden change detector 11 to be switched to the dead time generator 9 side, the output is used as an input to the compensation amount calculation unit 8.

  The interlock between the switch 10 and the detector 11 is, for example, a current detection circuit in which the detector 11 predicts a sudden load change from the detected current I of the current detector 7 or detects a sudden change in the load current by switching the operating state of the load 2. And a comparator, the switch 10 can be realized by a switch circuit that responds to the comparator output signal. Further, when there are a plurality of detectors 11, the switch 10 is switched to the dead time generator 9 side when any one of them detects a sudden change in the load current.

  According to the present embodiment, when the load current sudden change detector 11 detects or predicts a sudden change in the load current, a short period before the load current settles, instead of the detected current waveform I at the time of sudden load change, one cycle before. A load current waveform similar to that in the steady state, such as a load current waveform, is obtained from the dead time generator 9, and the same load voltage compensation as that in the first embodiment is performed. After the switching, the switch 10 returns to the original state after a time necessary for the sudden change of the load current to be settled (a time predicted in advance by the functional configuration of the load 2).

  As described above, when the load current changes suddenly, the voltage change in the jX term of the circuit element interposed between the voltage source 1 and the load 2 becomes very large. Moreover, there is a delay from the detection of the load current to the voltage output of the voltage source 1, and the voltage output of the voltage source 1 and the load current I converge to a steady state with vibration. As a result, it takes time until the load current settles to a steady state.

  Therefore, in the present embodiment, when the load current changes suddenly, the output voltage of the voltage source 1 is calculated by performing the correction amount calculation using the compensation signal based on the load current waveform immediately before it instead of the detection current I. It is possible to perform load voltage compensation by suppressing the vibration and shortening the time until the load voltage reaches the voltage command value.

(Embodiment 3)
FIG. 3 is a circuit configuration diagram of the power supply device according to the present embodiment. The figure shows a configuration in which the method of the second embodiment is combined with a conventional load voltage feedback method. In addition, this embodiment can also be set as the structure combined with Embodiment 1. FIG.

In FIG. 3, based on the load voltage detection signal, in addition to the load voltage compensation circuit (conventional feedback system) for the voltage command V _L * by the comparator 4, the amplifier 5 and the adder 6, the output current of the voltage source 1 A load voltage compensation method (embodiment 1) by a compensation amount calculation unit 8 based on I and a circuit constant (R + jX), and a load at the time of sudden change in load current by a dead time generator 9, a changeover switch 10 and a detection circuit 11 The voltage compensation method (Embodiment 2) is additionally provided.

  According to the present embodiment, in order to provide feedback control based on load voltage detection in addition to the methods of the first and second embodiments, in addition to the same effects as the first and second embodiments, a circuit set by the multipliers 8A and 8B Even if there is an error between the parameters such as constant R and jX and the actual circuit constant, the load voltage can always be matched with the voltage command by feedback control based on the load voltage detection, and high responsiveness and accuracy can be ensured.

  In the first, second, and third embodiments, the circuit constants R and jX interposed between the voltage source 1 and the load 2 are fixed. However, when these are switched, for example, when the transformer is switched, this case The same operation and effect can be obtained by switching the setting circuit constants in the compensation amount calculation unit 8 and the like. In addition, although a case where one load 2 is connected to the voltage source 1 is shown, in the case where a plurality of loads are connected from the voltage source 1 via a plurality of power cables, the compensation amount calculation unit 8 Can be accommodated by a circuit constant and a load current provided between the voltage source and each load.

The block diagram of the power supply device which shows Embodiment 1 of this invention. The block diagram of the power supply device which shows Embodiment 2 of this invention. The block diagram of the power supply device which shows Embodiment 3 of this invention. The block diagram of the conventional power supply device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage source 2 Load 3 Voltage command generator 4 Comparator 5 Amplifier 6 Adder 7 Current detector 8 Compensation amount calculation part 9 Dead time generator 10 Changeover switch 11 Load current sudden change detector

Claims (6)

A power supply apparatus, wherein a load is connected from a voltage source via a circuit element such as a reactor, and the output voltage of the voltage source is controlled according to a voltage command from a voltage setter to supply voltage-controlled power to the load,
A current detector for detecting an output terminal current of the voltage source as a load current;
A compensation amount calculation unit for obtaining a voltage change generated in the circuit element from the constant of the circuit element and the load current;
A power supply apparatus comprising: an adder that adds the voltage change to a voltage command of the voltage setter to obtain a voltage command of the voltage source. A dead time generator for obtaining an output obtained by delaying the detection current of the current detector by a certain period or a certain time;
A load current sudden change detector that detects a sudden change in load current when a load current sudden change occurs or is predicted on the load side; and
And a changeover switch that switches the output of the dead time generator as a load current detection input of the compensation amount calculation unit for a predetermined time when the load current sudden change detector detects a sudden change in load current. The power supply device according to claim 1. A voltage detector for detecting the voltage at the load end;
The load voltage control circuit using a load voltage control signal corresponding to a deviation between a detection voltage of the voltage detector and a voltage command of the voltage command generator as an addition input of the adder. The power supply device according to 1 or 2. A load voltage compensation method for a power supply apparatus in which a load is connected from a voltage source via a circuit element such as a reactor, and the output voltage of the voltage source is controlled according to a voltage command from a voltage setter to supply voltage-controlled power to the load Because
The current detector detects the output terminal current of the voltage source as a load current,
The compensation amount calculation unit obtains a voltage change generated in the circuit element from the constant of the circuit element and the load current,
The adder adds the voltage change to the voltage command of the voltage setter to obtain the voltage command of the voltage source, and a load voltage compensation method for a power supply device. The dead time generator obtains an output obtained by delaying the detection current of the current detector by a certain period or a certain time,
A sudden change in load current is detected when a sudden change in load current occurs or is predicted on the load side,
5. The switch according to claim 4, wherein when the load current sudden change detector detects a sudden change in load current, the output of the dead time generator is switched for a certain period of time as a load current detection input of the compensation amount calculation unit. The load voltage compensation method of the power supply device described in 1. The voltage detector detects the voltage at the load end,
6. The load voltage control circuit according to claim 4, wherein a load voltage control signal corresponding to a deviation between a detection voltage of the voltage detector and a voltage command of the voltage command generator is used as an addition input of the adder. The load voltage compensation method of the power supply device described in 1.

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