JPS58186379A - Control system for self-excited power converter - Google Patents

Abstract

PURPOSE:To continue as a reactive power regulator the operation of a self- excited power converter by switching the effective power control to a DC input constant-voltage control at the DC power source malfunction time when a DC power source and other different AC power source are interlocked. CONSTITUTION:The output of a converter 2 is interlocked through a transformer 3 and a switch 4 to an AC power source 5, the output 12 of a power converter is controlled via a switch 25 so as to become equal to the voltage reference 21 when the switch 4 is opened, and the effective and reactive components of the power are controlled and interlocked with the reactive power reference 22 and the effective power reference 31 by switching the switches 25, 36. The malfunction of a DC power source 1 is detected by a controller 42, the switch 36 is closed, the switch 53 is opened, thereby shortcircuiting the effective power control, and the phase of the converter 2 is controlled to become equal to the voltage reference 51. Accordingly, the operation as the reactive power regulator for stabilizing the voltage of the system can be continued at the malfunction time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an AC interconnection system that connects a DC power source to another different AC power source 1, and in particular, the present invention relates to an AC interconnection system that connects a DC power source to another different AC power source 1, and in particular, it is capable of controlling reactive power even during maintenance or abnormality of the DC power source. The present invention relates to a control method for a self-excited power converter suitable for continuous operation as an i-station.

[Technical background of the invention]

Conventionally, it has been known that when AC power supplies of a true system are operated in parallel, the voltage difference t between each AC power supply is controlled by the deviation of reactive power, and the phase difference t between each AC power supply is controlled by the deviation of active power. Inverter equipment! When connecting a DC-AC power converter to a power grid, the power grid cannot be controlled, so a self-excited power converter (hereinafter referred to as power converter) is used as the converter to convert active power and reactive power. A method is adopted to control the FIG. 1 shows a conventional control method for a power converter.

In the one-point diagram, the DC output of the DC power supply 1 is converted to AC by the power converter 2, which is converted to a predetermined voltage by the transformer 3, and connected to the power grid 5 via the switch 4. ?
It will be done.

In the control circuit 100, the voltage reference 21 and the output voltage 12 of the power converter 2 are compared, and the deviation 25m is applied to the error amplifier 24 via the changeover switch 25f. The reactive power reference 22 and the output of the reactive power detection circuit 23 are compared, and the deviation 25b is applied to the error amplifier 24 via the changeover switch 26, and the output of the error amplifier 24 serves as the power for the voltage control circuit 26. Similarly, active power base fs31
and the output of the active power detection circuit 32 t pro y crew 7' (
Phas-s 1ock@d 1oop) So-called P
This is one human power -4 of the LL circuit S4. J5 is a frequency divider that divides the output frequency of the PLL circuit 34, and its output becomes the other input "c" of the PLL circuit 34.
Another human power "port" of the LL circuit 34 is connected to the power system 5.
voltage 13 is given as a phase reference.

Although the PLL circuit 34 is a well-known circuit, it will be briefly explained here. Figure 2 shows the PLL circuit 34.

This is an example of the diagram, and the configuration of the PLL circuit 34 is composed of a phase error detector PHD, a low-pass P-wave device LPF, and a voltage controlled oscillator vCO. W*t of each of these elements - To explain, the phase error detector PHD generates a signal "2" k% proportional to the phase difference between the phase reference signal 101 and the phase feedback signal 1.
live. A ratio signal "2" proportional to this phase difference is input to the low-pass P-wave filter LPF, which removes harmonic components and amplifies the phase difference. Then, the voltage controlled oscillator VCO outputs a wave number compared to the output voltage of the low frequency F wave generator LPF, and the output of this voltage controlled oscillator vCO is
Hem is connected to the branch unit 35. Number of stages t of branching device 35
If N, the oscillation frequency of the voltage controlled oscillator VCO will be N times the phase reference signal 10''. Here, N is selected as an arbitrary integer depending on the number of phases of the inverter circuit of the power converter 1. Since the output of the phase error detector PHD is the phase feedback signal "c", the voltage controlled oscillator VCO
The resonant frequency of P
The function of one input "A" of the LL circuit 34 is that it can arbitrarily set the phase difference between the phase reference signal 10" and the phase feedback signal "..." by supplying a signal to the low-pass P-wave device LPF. .

Returning to FIG. 1 again, to explain the operation in step 7, since the phase of the power system 5 is applied as the phase reference signal 10'' of the PLL circuit 34, the output frequency of the PLL circuit 34 is the phase of the power system 50. Therefore, the phase of the power converter 20 is also synchronized with the phase of the power system 5. When the switch 4 is open, the switch 25 selects the deviation Jj5a'i7. The output voltage 12 of the power converter 2 is automatically controlled so that it becomes equal to the voltage reference 21. Furthermore, the input and output of the error amplifier j3 are short-circuited by a switch 36, so that the deviation of the active power 2
The active power control (b) path that controls the phase of the power converter 1 using 3mVC is not formed.When the 0-order switch 4t is closed, the selector switch 25 selects the deviation 25bt and sets the power conversion value WL2. The output voltage of the power conversion device 2 is automatically controlled so that the reactive power of the reactive power becomes equal to the reactive power reference 22.

Also, at the same time as the switch 4 is closed, the switch 36 is closed.
is resolved, the short circuit between the input and output of the error amplifier 33 is released, and the phase of the power converter 13 is automatically controlled so that the active power of the power converter 2 becomes equal to the active power reference 3.

[Problems with background technology]

As mentioned above, conventionally, in the control method of the power conversion value f112 connected to the electric power system 5, the active power of the power conversion device 2 is automatically controlled so as to always be equal to the active power reference 31. Therefore, when the capacity of the DC power supply 1 decreases or is opened, the active power control function cannot perform the prescribed operation. As a result, the power conversion device 2 becomes uncontrollable, resulting in a drawback that it becomes inoperable due to cross current with the power system 5.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a control method for a self-excited power converter.

[Summary of the invention]

In order to achieve this objective, the present invention allows the power converter 2 to continue operating even when the capacity of the DC power supply 1 decreases or is disconnected for maintenance etc., and only the reactive power control function among the control functions is performed. It is characterized in that it can be effectively operated as a reactive power adjustment device for stabilizing the voltage of the power system 5.

[Embodiments of the invention]

The present invention will be explained below using an embodiment shown in FIG. In Fig. 3, parts with the same symbols as in Fig. 1 have the same functions. The difference in Fig. 3 from Fig. 1 is that the operation of the error amplifier J1 in the active power control system in Fig. 1 [controlling switch 36
In addition to the signals that are controlled simultaneously with switch 4 in Fig. 1,
The error amplifier 52 of the DC input constant voltage control system is also controlled by the output signal 4Ja of the control circuit 42 which is activated when the capacity of the DC power supply 1 is reduced or opened, and is also controlled by the other output signal 42b of the control circuit 42. The output is the PLL circuit 34
This is the point where the input becomes "A" and the phase of the power conversion device 2 is controlled.

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

That is, in Figure #I3, if the DC power supply 1 is established in the predetermined 1st direction, the t signal converted by the level converter 41 is input to the control circuit 42, and the switch 36 is opened with the 7th output signal 42a. The switch 53 is closed by the output signal 4jb of the control circuit 42, and active power control is performed by the output of the error amplifier 33. Here, the control circuit JjFi in this embodiment detects a decrease in the capacity of the DC power source 1 or an open circuit using the output of the level converter 41, but the input signal to the control circuit 42 is used to detect a decrease in the capacity of the DC power source 1 or an open circuit. Not only can it be a device that operates by a signal that is operated before the DC power supply 1 is opened, but it may also be a device that operates by a signal that is operated before the DC power supply 1 is opened.Returning to the iris 3 diagram, when the control circuit 42 is activated, the switch 36 is closed and becomes effective. The power control function is stopped, and instead, the switch 5S is opened, the error amplifier 52 is operated, and the phase of the power converter 2 is controlled so that the DC input voltage is equal to the voltage reference 51. That is, in a steady state, this DC input constant voltage control receives active power from the power system 5 and charges a capacitor (not shown) or DC power source 1 provided in the input line of the power converter 2 with a constant voltage, and the power converter 2 The no-load loss will be consumed. When the AC/DC power supply 1 (not shown) is overcharged, surplus power is returned to the power system 5 through the DC input constant voltage control VC through the power converter 1, the transformer 3, and the switch 4. As a result, only the zero loss of the power converter ij is supplied from the power system 6, and the power converter 2 can operate as a reactive power control function. Detection of capacitance drop or open circuit of DC power source 1 t[l31EAlthough the explanation has been made using a method based on voltage detection, the detection means may be of any type as long as it operates due to a capacitance decrease or open circuit of DC power source 1. Operating conditions of the switch installed between the power converters 20, not shown in the diagram,
Alternatively, a similar effect can be obtained by detecting a DC current level relative to the setting of the active power reference 31, and more effects can be obtained by operating under one of these conditions. This implementation is shown in Fig. 4. In Fig. 4, similarly to Fig. 31jA, if the DC power supply 1 is normal, the switch 36 is opened by the output signal 4ja of the control circuit 42, and the error amplification @is is operated.
Active power control is performed. The output of the bias circuit 43 is added to the output of the difference amplifier 33 by the adder 44, and even if the output of the error amplifier S3 of the bias circuit 43 is zero, the phase of the power converter @2 is adjusted. By delaying the power system 6, the power system IR 5 is set to supply active power equivalent to the no-load loss of the power conversion scissors [j. Therefore, if the DC power supply 1 is normal, the active power control is performed. When the weight of the DC power source 1 decreases or #'i is opened, the control circuit 42 detects this and outputs the output signal 421.
is output, the switch 36'Ik is controlled, and the 1-difference amplifier 33
short-circuit the input and output of the device and stop the active power control function.

When this active power control function stops, the input "A" of the PLL circuit 34 is determined only by the output of the bias circuit 43, and the power converter @2 is switched so that the no-load loss of the power converter IL2 is supplied from the power system 5. The output phase can be controlled and operation can be continued, and at this time, the reactive power control function can transfer reactive power to and from the power grid 6, so the power converter 2 can be operated without reactive power. It can be operated as a regulating device.

〔Effect of the invention〕

As described above, according to the present invention, in an AC interconnection system in which a DC power source is connected to another different AC power source,
Even if the DC power is abnormal or disconnected from the system for maintenance, the power converter can operate as a reactive power adjustment device to stabilize voltage in the power system without stopping the system. be able to·

[Brief explanation of the drawing]

Figure 1 is a professional diagram showing the control method of a conventional AC interconnection system, Figure #I2 is a specific circuit configuration diagram of the PLL circuit in Figure 1, and Figure 3 shows an embodiment of the present invention. Figures 1 and 4 are block diagrams showing other embodiments of the present invention. 1... DC power supply, 2... Self-excited power converter, 3.
...Transformer, 4...Switch, 5...Power system, 1...Output current, 12...Output voltage, 13...Power system voltage, 21...Voltage reference, 22 ... Reactive power standard, 21... Reactive power inspection circuit, 24... Error amplifier, 25... Changeover switch, j' 5 a + J
5 b... Deviation, 26... Voltage control circuit, 31...
・Active power standard, JJII...deviation, 34...PL
L circuit, 35... Branch, 36... Switch, 41
... Level converter, 42 ... Control circuit, 4ja, 4
Jb...Output signal, 43...Bias circuit, 44.
...Adder, 51...1 pressure reference, 52...1 difference amplifier, 53...switch.

Claims (2)

[Claims] (1) The AC output of a self-excited power converter that converts the output of a DC power source into AC is connected to another AC power source, and the automatic power converter converts the effective and reactive power from the AC power source. In the AC interconnection system to be controlled, when the DC power supply is opened or the voltage drops, active power control is switched to DC input constant voltage control, so that the system operates as a reactive power adjustment device even if the DC power supply is opened or the voltage drops. I want to continue this! #Control method for automatic power conversion equipment that generates mold. (2) When the AC output of a self-excited power converter that converts the output of a DC power source to alternating current is connected to another AC power source, the self-excited power converter converts the active and reactive power from the AC power source. In the AC interconnection system to be controlled, the active power control function is stopped due to an open circuit or voltage drop of the DC power supply, and an active power control signal is supplied from the AC power supply to compensate for the no-load loss of the self-excited power converter. A control system for an automatic power converter that allows operation to continue as a reactive power adjustment device even if the DC power supply is opened or the voltage drops t'17t.