JPH0315429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inversion control device for inverting DC power to AC power.

Conventionally, there has been a device of this type as shown in FIG. 1 is an AC power transmission line, 2 is a transformer, 3 is a forward converter that is connected to the power transmission line 1 via the transformer 2 and converts AC power into DC power, and 4 is connected to the DC end of the forward converter 3. 5 is an inverter that converts the DC power of the power transmission line 4 into AC power, and 6 is the AC end of the inverter 5 (also known as the valve winding voltage (E _i ) due to the AC voltage on the transformer side). transformer connected to
7 is a power transmission line connected to the secondary side of the transformer 6, 8 is an alternator that detects the current of the power transmission line 4, and 9 is the power transmission line 7.
10 is a divider circuit that calculates the ratio I _d /E of the output of the current transformer 8 (DC detected current value) I _d and the output of the transformer 9 (AC detected voltage value) E; 11
12 is a multiplication circuit that multiplies the ratio obtained by the division circuit 10 by a constant K, and 12 is a first subtractor that calculates the difference between the output signal 11a of the multiplication circuit 11 and the set value cosγ of the control amount of the phase control circuit 13, which will be described later. , 13 is a phase control circuit that outputs a firing pulse whose phase is controlled according to the difference obtained by the first subtracter 12.

Next, the operation will be explained. The DC detection current value of the power transmission line 4 detected via the current transformer 8 is I _d , the AC detection voltage value of the power transmission line 7 detected via the transformer 9 is E, and the transformer valve on the primary side of the transformer 6 When the winding voltage value is E _i , the control margin angle is γ, the control advance angle is β, and the commutation reactance for one phase is X _i , the input cosγ−cosβ of the phase control circuit 13 is expressed by equation (1). . (Refer to "Direct Current Transmission Technology Explanation" edited by the DC Power Transmission Expert Committee, published by the Institute of Electrical Engineers of Japan (March 30, 1982), pages 82-85) cosγ−cosβ=√2・X _i・I _d /E _i ≒KI _d /E… ……(1
) However, for convenience, let √2・X _i /E _i ≒K/E. Since equation (1) holds, let γ and X _i be constants,
An ignition pulse is generated when the relational expression between E _i and I _d is satisfied.

Thereby, the output of the first subtractor 12 has a value related to the control advance angle β, whereby the firing pulse of the controlled phase control circuit 13 is transmitted to the inverter 5
supplied to

In the conventional inverse conversion control device, although it is necessary to completely model the controlled object, as described above, the commutation reactance X _i in equation (1)
Since the configuration is such that the primary voltage E _i of the transformer 6 is determined by converting the secondary voltage to the theoretical value, there is a drawback that the control error is large.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and an object of the present invention is to provide an inverse conversion control device that can improve control accuracy by adding a control system related to control margin angle. do.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, 14 is the difference between the (measured) margin angle value γ _det obtained by measuring the commutation waveform of the thyristor valve of the inverter 5 and the preset reference margin angle value γ _ref . a second subtractor that takes 15
16 is an amplifier circuit that amplifies the margin angle difference γ _ref −γ _det obtained by the second subtractor 14; 16 is a limiter that receives the output signal of the amplifier circuit 15 and is saturated when the input exceeds a predetermined value; 17 is a limiter 16; This is an adder which takes the sum of the output signal and the control amount cosγ−cosβ output from the first subtracter 12, and uses this as an input signal to the phase control circuit 13. In addition, the same parts as in FIG. 1 are indicated by the same reference numerals.

Next, the operation will be explained. first subtractor 1
The output No. 2 is obtained in the same manner as described in FIG. 1, and in the present invention is subjected to the following correction processing by the adder 17. That is, the second subtractor 14 calculates the margin angle difference γ _ref by the measured margin angle value γ det obtained by actually measuring the margin angle value γ ref and the reference margin angle value γ _{ref .}
-γ _det is obtained, amplified by the amplifier 15 and supplied to the limiter 16. When the input signal is above a predetermined value, the limiter 16 performs a normal limiting operation to stabilize the control system and supplies an output signal to the adder 17. Adder 17
is the corrected phase control signal (cosγ−cosβ) by adding the output signal of the limiter 16 to the output signal of the first subtractor 12, that is, by adding the margin angle difference γ _ref −γ _det . +( _γref − _γdet )
is input to the phase control circuit 13.

In the above embodiment, an example in which a duplicated control system is provided has been described.
3 may be used to produce the same effect as in the above embodiment.

As described above, according to the present invention, since a control system is provided that feeds back the difference between the measured margin angle and its reference value, conventional control can be used for normal operations that require a relatively slow response. In addition, when a high-speed response is required, feedback control can be used to accurately follow the response, thereby improving control accuracy and reliability.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the conventional inverse conversion control system.
FIG. 2 is a block diagram of an inverse conversion control system according to an embodiment of the present invention. 2, 6...Transformer, 3...Forward converter, 5...Inverse converter, 10...Divide circuit, 11...Multiply circuit,
12...first subtractor, 14...second subtractor,
17... Adder, 13... Phase control circuit, 15...
...Amplifier, 16...Limitsuta. In addition, in the figures, the same reference numerals indicate the same parts.

Claims (1)

[Claims] 1 A forward converter that exchanges AC power into DC power,
an inverter that transmits the DC power converted by the forward converter via a DC transmission line and converts it back into AC power; a DC detected current value that detects the DC power via the converter; and the inverter. a division circuit that outputs the ratio to the AC detection voltage value detected via the transformer on the output side of the circuit; a multiplier circuit provided on the output side of the converter that multiplies the output of the divider circuit by a coefficient for converting it into a primary voltage value of the transformer; and a first multiplier circuit that subtracts the output value of the multiplier circuit from the set value of the margin angle. a subtracter, a second subtracter that calculates the difference between the measured margin angle value detected by the commutation waveform of the inverse converter and the reference margin angle value, and the output value of the second subtracter and the an adder that adds the output value of the first subtracter; and a phase control circuit that uses the output value of the adder as an input signal to control the advance angle of the firing phase of the inverse converter. Inverse conversion control device.