JPS58148675A - Power converter - Google Patents

Abstract

PURPOSE:To suppress the variation in the voltage of a connecting point of a power converter by controlling the converter to switch with the detected voltage value of an AC power source when opening a switch and with the prescribed control reference after energizing the power source when the converter is connected through the switch to the AC power source. CONSTITUTION:A power converter 1 is connected and operated through a connecting reactor 2 to an AC power source 4 by the operation of a switch 3. At this time, the voltage reference 11 and the detected voltage value 311 of the power source 4 are inputted to a conversion circuit 13, the voltage reference is switched to the 311 side when the switch 13 is opened, and compared with the detected voltage value 211 of the reactor 2, thereby performing an automatic control, and after the switch 3 is closed, the voltage reference of an error amplifier 12 is connected to the 11 side, thereby performing the control with the prescribed voltage or power. Accordingly, the variation in the voltage can be effectively suppressed at the time of connecting the power converter 1 to the power source 4, thereby stabilizing the voltage of the AC power source.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a power conversion system which is improved in order to suppress voltage fluctuations at a connection point when connected to another AC power source.
It is related to t.

[Technical background of the invention]

For example, one of the purposes of interconnecting a power converter using an inverter with another AC power source is to stabilize the voltage at the interconnection point and supply bistable power to the load C.

Conventionally, in order to stabilize the voltage at the grid connection point, an inductance (hereinafter referred to as a grid connection reactor) is provided between the power converter and the AC power supply, and the voltage applied to the grid connection reactor is The power converter is configured to control the voltage generated by the power converter.

FIG. 1 shows a conventional example. In the figure, l is a power conversion device,
2 is a interconnection reactor, jJ. 211 is interconnection reactor 2
3 is a switch, 4 is an alternating current source, and 5 is an automatic control circuit of the power converter l.

The power conversion device 1 detects the detected voltage JJJ of the output 2I of the interconnection reactor 2 as a feedback signal of the automatic voltage control system,
The automatic control circuit 5 performs predetermined magnetic pressure control.

Here, although the automatic control circuit 5 is well-known, - example 21! This will be explained with reference to I. In FIG. 2, the same symbols as in FIG. 1 have the same functions; 11 is a voltage reference, 11 is an error amplifier, 212 is a feedback voltage setting value, and 111 is an error signal. The detected voltage 111 is rectified by a rectifier circuit 21M, converted into a positive DC port with a predetermined polarity, and set to a predetermined feedback voltage setting value 11 by a variable resistor 114.
The level is converted to H. This feedback voltage setting value 212 and voltage reference 11 are given as inputs to an error amplifier 12, and an error signal 121 is obtained from the deviation: y. This error signal 121 is applied to a phase control circuit (not shown) which determines the firing phase of the power converter r, and is controlled so that the voltage of the output 21 is equal to the voltage reference 11.

By changing this voltage reference 11, the voltage at the output 2 can be changed appropriately. Returning to FIG. 1 again, when the switch 3 is closed, the output voltage 111 of the power converter I is controlled so that the interconnection point voltage 1, ie, the voltage at the output 21, becomes equal to the voltage reference 12. . This phenomenon will be explained using a vector diagram of the eighth factor. In the figure, it is assumed that the voltage phases of the power converter device 1 and the AC power source 4 are completely equal, and the power converter @X
If the output voltage 111 is 81 and the voltage of the AC power supply 4, that is, the voltage of the output 21 is 81, then the interconnection reactor 2
6: is the current flowing through the one-way system reactor 1 due to the voltage g, -it, of the illustrated vector being applied! L
As shown in the figure, a vector IL having a phase difference of 90° with respect to the voltage vector "ls"lg is expressed.

That is, the power applied to the interconnection reactor 2 is reactive power in which the voltage and current vectors have a phase of 90°. As is clear from FIG. 8, if the output voltage 1 is smaller than the output voltage E3, reactive power will be supplied from the AC power supply 4 to the power converter l, and if the output voltage g1 is smaller than the output voltage M,
If it is larger than , the opposite will occur.

In addition, as shown in FIG. 4, the output voltage "1*"l of the voltage converter WtI and the AC key 4 is equal to 0 in the voltage phase of the 1st key.
If there is a difference in voltage g1-4 . applied to the interconnection reactor 1. Therefore, the electric current fi l L is expressed by the vector shown. [If the pressure phase difference 0 is small, the voltage E1-l,
is the voltage E,.

l! The current IL can be approximated by a right angle to the voltage g1, g, and therefore the current IL is represented by a vector having a phase difference of 180 DEG from the voltages g1 and g. That is, the power at this time becomes active power. As is clear from FIG. 4, if the AC power supply 4 is ahead of the power converter 1 (2), active power will be supplied from the AC power supply 4 to the power converter tt. If the phase relationship is reversed, active power will be supplied from the IT force converter J to the AC power source 4. That is,
Assuming that the voltage 1 phase of AC power converter #4 cannot be changed, the reactive power between the two power supplies can be controlled by changing the voltage 1 phase of power converter f.

r Problems of Background Art] Generally, when connecting the power converter Il to another AC power source 4, the magnetic force conversion #twLI must be set in advance.

A control method is used in which synchronous control is performed so that the phase is the same as that of the AC power source 4, and after the two power sources are connected, the phase of the power conversion device fils is changed to transfer and receive a predetermined active power. In FIG. 1, the active power is controlled (in both cases, it is assumed that the same control method is used).

However, in the method shown in Fig. 1, the voltage of the output 21 is controlled to be kept constant before the switch S is closed.
A voltage difference occurs between the AC power supply 4 and the switch 3, and immediately after the switch 3 is turned on, reactive power is exchanged due to the voltage difference between the two power supplies as described above, and the voltage of the output 21 is stabilized. The AC power source 4 is forced to fluctuate until it reaches the desired value, and does not contribute to the stabilization of the AC power source 4.

[Purpose of the invention]

The present invention has been made in order to improve the above-mentioned drawbacks.The present invention has been made in order to improve the above-mentioned drawbacks. It is an object of the present invention to provide a power conversion device that can maintain constant current and eliminate fluctuations in AC power #4.

[Embodiments of the invention]

The present invention will be explained below with reference to an embodiment shown in Fig. s5 and C2. Items with the same reference numerals as those in FIG. The point is that the automatic control circuit 6 is configured to input the detection voltage III.

Next, the operation of the present invention will be described.

That is, if the AC chamber m4 is established in FIG. 5, the detected voltage 311 is given as a reference signal to the automatic control circuit 6 before the switch 3 is closed, and It is controlled to be equal to the voltage 3I of room #4.

An example of the automatic control circuit 6 of the present invention will be explained with reference to FIG. In FIG. 6, the same reference numerals as in FIG. 2 have the same functions. The detected voltage 322 in the figure is rectified and then level-adjusted, and is obtained as the pressure reference srs. Reference numeral 12 denotes a reference switching circuit which selects the voltage references 11 and 312. The output of this reference switching circuit 13 is given to an error amplifier Zj as a voltage reference xsr. If the voltage of the AC power supply 4 is established before the switch 3 is turned on, the detected voltage JJZ
is selected by the switching circuit 13 and becomes the voltage reference Z31, and when there is no modified power supply 4 or after the switch 3 is turned on, the voltage reference 11 is selected and the output 21 is automatically controlled to a predetermined value. be done. Here, the reference switching circuit 13 is 7
By providing a well-known coupling element using a capacitor and a resistor, sudden changes in the voltage reference 131 at the time of reference switching can be suppressed without impairing the controllability of the error amplifier 12.

This embodiment has been explained by detecting the output 21 from the AC chamber #4 side of the interconnection reactor 2, but the detection point is from the interconnection reactor 2.
A similar effect can be obtained by performing control before. Although the control amount after switching the switch 3 is set to voltage, the same effect can be obtained by setting the control degree 1 to reactive power, for example, based on the above explanation. The AC power source 4 may be a power source such as a general power distribution system, or may be another power converter device similar to the power converter bag r11.

〔Effect of the invention〕

As described above, according to the present invention, in order to suppress the voltage ratio fluctuation at the connection point when connecting one power source in a power conversion system where a power conversion device and another AC power source are connected,
If the AC F/ contributes to stabilizing the voltage of the power supply, it is possible to control a predetermined electrical ratio or power in a steady state.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a conventional power conversion system. Figure 2 is a block diagram showing a conventional automatic control system. Figure 88 and Figure 1 are vector diagrams explaining the generation of reactive power and active power, respectively. Figure s5 is a system diagram of a power conversion system showing a -am example of the present invention, and Figure 6 is a block diagram of an automatic control circuit of the present invention. l...Power converter, 111...Output voltage, 2...
- Grid connection reactor, 11... Output, 3... Open w9 device, 4... AC room-1211... Detection voltage, 5...
Automatic control circuit, 21...lll mouthpart 314.° level setter, 212... return turtle pressure setting value, 12...-
Difference amplifier, 124...Error signal, 31...Voltage, 1
11...Detection voltage, 312...Voltage reference, IJ...
・Reference switching circuit. 131... Voltage standard, applicant's agent Takehiko Suzue, Figure 1, Figure 1, Figure 2, E1-E2 E+

Claims (1)

[Scope of Claims] In a power conversion system in which a power conversion device that is automatically controlled to maintain power at a predetermined value and another AC power source are connected via a switch, a switching circuit that is operated simultaneously with the switch. This switching circuit controls the output voltage of the first distribution power converter so that it is equal to the voltage detection value of the AC power supply when the switch is opened, and when the switch is closed. A power conversion device characterized in that the power of the power conversion device is controlled so that the power is equal to a predetermined control standard.