JPS62107635A - Constant voltage control of electric power converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a constant power control method for a power conversion device such as a DC power transmission or frequency conversion device that operates while coordinating a forward converter and an inverse converter.

[Technical background of the invention]

FIG. 3 is a DC two-terminal power transmission system diagram as an example of a conventional power converter of this type.

10 and 11 are AC systems, 20 and 21 are transformers, 30 and 3
1 is a converter, 40 and 41 are DC reactors, 50 and 51
is a DC line.

Considering the case where the converter 30 performs forward conversion and the converter 31 performs inverse conversion, the converter 30 is assumed to be a forward converter, and the converter 31 is assumed to be an inverse converter.

Generally, the forward converter 30 is operated by constant current control to determine the current Id of the DC line 50, and the inverse converter 31 is operated by constant voltage control or constant margin angle control to determine the DC voltage Vd of the DC line 50. ing.

The control characteristic diagram when such control is performed is shown in the fourth diagram.
As shown in the figure.

I-1 and 1-2 represent the control characteristics of the forward converter 30, and l
l-1 and -2 indicate control characteristics of the inverse converter 31.

FIG. 5 is a block diagram of a control device that produces the control characteristics shown in FIG. 4 in the forward and inverse converters.

60 is a switch, 70 and 71 are adders, 80 is a constant current control circuit, 81 is a constant voltage control circuit, 82 is a constant margin angle control circuit, 90 is a minimum value selection circuit, a forward converter 30 and an inverse converter 31 are the control angle α of the output of the control device in FIG.
When the input is the maximum positive value, the control angle α is the minimum, and when the input is the negative minimum value (the absolute value is the maximum), the control angle α is the maximum and calculation is performed.

The switch 60 is opened in the forward converter 30 and opened in the inverse converter 3.
1 is closed.

Therefore, in the control device for the inverter 31, the adder 70 reduces the DC current setting value Idρ by the current margin ΔdP, and the constant current control circuit 80 produces the characteristic ll-2 in FIG. , constant current circuit 80 of forward converter 30
Caused by! There is a difference in current margin ΔIdp from the characteristic of -2.

The control characteristic 1-1 of the forward converter 30 is the characteristic when operating at the minimum value of the control angle α determined by the characteristics of the forward converter.

The constant voltage control circuit 81 is controlled by the difference between the DC voltage setting value Vdp from the adder 71 and the DC voltage Vd, but in the forward converter 30, the direction of the DC voltage Vd shown in FIG. Since the control angle from the voltage control circuit 81 is the maximum value determined by the constant voltage control circuit 81, it is controlled by the control angle α from the constant current control circuit 80.

On the other hand, in the inverter 31, since the direction of the DC voltage Vd in FIG. 1 is regarded as a positive value, the constant voltage control circuit 81 controls the constant voltage (
Depending on the conditions, the control angle α is determined by the constant margin angle control circuit 82), and the characteristic ll-1 in FIG. 4 is created.

The constant margin angle control circuit 82 is a circuit that generates a control angle to ensure a constant margin angle γ to prevent commutation failure of the inverter 31 during normal operation. The determined control angle is being calculated. X is commutation reactance.

Among the control angles output from the constant current circuit 80, constant voltage circuit 81, and constant margin angle circuit 82 described above, the minimum control angle is selected by the minimum value selection circuit 90, and the control angle is selected by the forward converter 30 as the control angle α. The inverter 31 is operated.

As a result, in the forward converter 30, the control characteristics shown in FIG. 4 1-4 and I-2 are obtained, and in the inverse converter 31,
As a result, the DC power transmission system in FIG. 3 is operated at point A in FIG. 4.

Note that the control characteristic n-1 of the inverse converter 31 in FIG.

For example, when the AC voltage Vac is low or the DC current Id is large, the control angle from the constant margin angle control circuit 82 becomes smaller than the control angle from the constant voltage control circuit 81, so that the constant margin angle control circuit It may also be determined by the control angle of

Up to now, we have described the converter 3o as a forward converter and the converter 31 as an inverse converter, but when the switch 60 in FIG. 5 is opened in the converter 3o and closed in the converter 31, the converter 30 is It is clear that the converter, converter 31, is an inverse converter. Forward converter 30 of the DC two-terminal system in Fig. 3
and the inverter 31 are operated by the above operation.
o. It is also possible to use a forward converter 31, in which case the DC voltage Vd becomes reverse polarity and the power that was being transmitted from the converter 30 to the converter 31 is reversely transmitted from the converter 31 to the converter 30. Electricity will be transmitted. This is called a tide reversal.

Conventionally, constant power control for keeping the transmitted power constant in the above-mentioned DC terminal power transmission system has been performed using the first-order lag control calculation circuit shown in FIG. 7 in the constant power control device shown in FIG.

In FIG. 6, 101 and 102 are adders, and 110 is a first-order delay control calculation circuit. In Fig. 7, 120.121 is an operational amplifier, and 131.132.133 are resistors R1 and R2, respectively.
,R.

140 represents an upper and lower limiter, and a capacitor C1151 represents an upper and lower limiter.

The operation of the constant power control device shown in FIG. 6 will be explained. Adder 10
1, the difference between the power setting device Pdρ and the transmitted power P of DC power transmission is taken and output as an error signal ERR.

ERR = Pdp - Pd α) Here, the transmitted power Pd is the absolute value of the product of the DC voltage Vd and the DC current Id in Figure 3, and Pd = l Vd * Idl
■It is sought after. The error signal ERR from the adder lO1 is input to a first-order lag control calculation circuit 110, subjected to a first-order lag control calculation, and then output as a correction signal DP. The adder 102 uses the correction signal DP and the power setting value P.
dP is added and a DC current setting value Idp is output. Generally, in DC power transmission, the DC voltage setting value Vdp is set to a constant value, so the increase or decrease in DC transmission power is determined by the DC current setting value IdP.
It is known to increase or decrease the amount of Therefore, 100% of the power setting value Pdp is set to 10% of the DC current setting value rdp.
The power setting value Pdp is determined to correspond to 0%. Therefore, by setting the DC current setting value Idρ outputted from the adder 102 in FIG. 6 to the DC current setting value IdP in FIG. 5, the transmitted power Pd of DC power transmission is determined. The primary lag control calculation circuit 110 in FIG. 6 is for correcting when the transmitted power Pd of DC two-terminal power transmission becomes a transmitted power different from the power setting value Pdp due to a disturbance or the like. FIG. 7 shows a conventional example of a first-order lag control circuit used in the first-order lag control calculation circuit 110.

However, the transfer function G (s) of the circuit shown in FIG. 7 is as follows. Generally, K is called the gain and T is called the delay time constant. S is Laplace's operator.

[Problems with background technology]

The conventional constant power control device described above with reference to FIGS. 6 and 7 has the following problems. In other words, (a) When the DC transmission system shown in Figure 3 starts up, the DC voltage Vd
It takes a long time to rise from zero voltage to the rated voltage, and the transmitted power Pd determined by equation (2) becomes significantly lower than the power setting value Pdρ for a certain period of time. Therefore, the error signal ERR expressed by equation (2) increases, and the correction signal DP, which is the output of the -order lag control calculation circuit 110, increases. In this state, the DC voltage Vd becomes equal to the DC voltage setting value VdP due to the action of the constant voltage control circuit 81 of the inverter 31 of the DC transmission system shown in FIG. 3, and the DC current setting value Idp becomes the DC power setting value PdP. Therefore, even if the DC power Pd becomes equal to the DC power set value Pdp, the error signal DP is determined by the delay time constant T,=C*R, determined by the first-order lag control calculation circuit in FIG. It becomes zero only in the time it takes. For this reason, it takes time for the DC current setting value Idp to become equal to Pdp, and when the constant power control device shown in Figure 6 is applied to the DC power transmission system shown in Figure 3, there is a problem that fluctuations in the transmitted power at startup become large. It is. FIG. 8 is a diagram illustrating the movement of the DC current setting value Idp when the constant power control device described in FIGS. 6 and 7 is used. The above problem will be explained using FIG. 8. When the DC power transmission system shown in Figure 3 is activated at time 1 = 1o, the transmitted power Pd does not rise to the power setting value PdP until time t = , so the time determined by the first-order lag circuit in Figure 7 DC current setting value I output from the constant power control device in Fig. 6 according to the constant T
dρ increases up to I dPl, which is limited by the upper and lower limiters 151 in FIG. Thereafter, when the transmitted power Pd exceeds the power setting value, time 1=1. By then, the DC voltage setting value Idp becomes Pdp. In the inverter 31, since the response of the constant current control circuit 80 in FIG. 5 is faster than the response of the constant voltage control circuit 81, the DC voltage Vd of the DC power transmission system in FIG. It is approximately equal to the DC voltage setting value Vdp. Time t and t2. Although the DC transmission system shown in Figure 3 can transmit power as instructed by the power setting value Pdp, it is not possible to transmit power as instructed by the power setting value Pdp due to the use of the first-order delay circuit shown in Figure 7. It becomes.

(b) Also, when reversing the power flow in the DC transmission system shown in Figure 3, the period from the start to the end of the reversal of the power flow.

The absolute value of the DC voltage Vd becomes less than or equal to the DC voltage setting value Vdp, and the transmitted power Pd fluctuates greatly. As a result, the DC current setting value Idp output from the constant power control device shown in Fig. 6 fluctuates in the same way as at startup, and the constant power control shown in Fig. 6 does not operate properly immediately after the power flow is reversed. There is.

(c) In order to solve the problems in (a) or (b) above, the ERR signal shown in Fig. 6 is cut off by a switch when the DC power transmission system shown in Fig. 3 starts up or the power flow is reversed, and first-order lag calculation is performed. A method of stopping the operation of the circuit 110 has been considered, but this method not only causes disturbances in the first-order delay calculation circuit when the switch is turned on and off, but also
There is a problem in that the response of the constant power control circuit shown in FIG. 6 becomes worse.

[Purpose of the invention]

Therefore, the present invention was made in order to solve the problems of conventional devices, and the DC current setting is determined by a constant power control device during a certain period of time when the transmitted power is greatly fluctuated due to startup of DC power transmission, power flow reversal, etc. By regulating the fluctuation of the value,
It is an object of the present invention to provide a constant power control method for a power conversion device configured to speed up the response of the constant power control device.

[Summary of the invention]

The present invention is a constant power control device used in a power conversion device such as a DC power transmission or a frequency conversion device that operates while coordinating a forward converter and an inverse converter. The present invention is characterized in that when changing , the upper and lower limiters of the control calculation of the constant-time power control device are changed over time.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a constant power control device for a power conversion device according to the present invention will be described below with reference to FIGS. 1 and 2.

In FIGS. 1 and 2, the same reference numerals as in FIGS. 7 and 8 indicate the same or corresponding parts.

In FIG. 1, 150 is a switch, and 152 is an upper and lower limiter.

160 is an upper/lower limiter switching signal generator.

The upper and lower limiter 152 has a narrower width between the upper and lower limit values than when the upper and lower limiter 151 is used.

The upper and lower limiter switching signal generator 160 switches the switch 150 at the start of DC power transmission or at the start of power flow reversal in FIG.
A signal is output to connect the switch 150 to the a side, but after a predetermined period of time has elapsed after activation or after the start of power flow reversal, a signal is output to connect the switch 150 to the a side.

FIG. 2 is a diagram illustrating the movement of the DC current setting value Idp output from the constant power control circuit according to the present invention in which the first-order lag control calculation circuit 11o of FIG. 4 is replaced with the first-order lag control calculation circuit 11o of FIG. be. When starting up the DC transmission system of FIG. 3 at time 1=1°, the switch 150 of FIG. 1 is closed to the b side by a signal from the upper/lower limiter switching signal generator 160.

At this time, the value of the correction signal DP, which is the output signal of the -order delay circuit 111, is limited by the upper and lower limiter 152, so the DC current setting value Idρ output from the constant power control circuit in FIG. 1 is equal to or greater than Idp2. do not become.

Thereafter, at time t=t1 when the DC transmission power of the DC transmission system in FIG. 3 rises to the power setting value Pdp, the switch 150 in FIG. It will be done. At this time, the value of the correction signal DP, which is the output signal of the -th delay circuit 111, is limited by the upper and lower limiter 151, and the maximum value of the DC current setting value Idp output from the constant power control circuit in FIG.
This will extend from P2 to Idp□. In other words, after time 1=11, the constant power control circuit in FIG.
Similar to the one using the first-order delay circuit in the figure, the power setting value P
DC depending on the dp value? I! The current setting value p is I dp
It can be expanded to t.

This embodiment has the following effects. Namely.

When starting up the DC power transmission system in Figure 3, the DC voltage Vd takes a long time to rise from zero voltage to the rated voltage, and the transmitted power Pd becomes much lower than the power setting value Pdp for a certain period of time. . As a result, from time 1=1o to tl in FIG. 2, the correction signal that is the output of the first-order lag circuit 111 in FIG. 1 increases until it reaches the upper limit of the upper and lower limits.
However, from time 1=1° to tl, the upper limit value is limited by an upper/lower limiter 152 that is smaller than the upper/lower limiter 151 during normal operation. Therefore, there is a point when the DC transmission voltage Vd rises to the rated voltage and the transmitted power Pd becomes the power setting value Pdρ at the rated DC current setting value =
At j, the DC current setting value Idp, which is the output of the constant power control circuit in FIG. 1, immediately decreases to the rated DC current setting value. Second
In the figure, time 1=11 to 1=1. Since the current is the rated DC current, proper control can be started in a much faster time than the time 1=12 explained in FIG.

Next, the operation of the constant power control device according to the present invention when the power flow is reversed will be explained. Before starting the power flow reversal, the switch 150 in FIG. 1 is closed to side a, and operates in the same way as the first-order delay control circuit in FIG. The switch 150 is closed to the b side, and when the current reversal is completed, the switch 150 is closed again to the a side. As a result, the upper limit value of the auxiliary signal DP output from the first-order delay circuit 111 in FIG.
An increase in the DC current setting value Idp from the constant power control device shown in the figure is suppressed. Furthermore, after the power flow is reversed, the upper and lower limiter 15 serves as the upper and lower limiter of the -order delay circuit 111.
1 is used, the constant power control device shown in FIG. 1 can immediately perform proper control.

Incidentally, although the constant power control device shown in FIG. 1 has been described above as being constructed by hardware, it is clear that it can be realized by software by using a computer.

When implementing the first-order lag calculation of formula (3) on a computer, the first-order lag calculation of formula (3) can be implemented by calculating the following difference equation (■) at every fixed sampling period.

The subscript n is the value at the time of sampling this time, n-1
represents the calculated value at the previous sampling. Signals ERR and DP are the signals shown in FIG. T□ is the time constant of the first-order lag calculation, LMX is the upper limit value of the calculation,
LMN represents the lower limit value of calculation. E.R.R.
I and DPI represent intermediate results for the calculation.

Equation (2) shows that the upper limit value LMX and lower limit value LMN of the first-order lag calculation can be manipulated every sampling period. That is, it is shown that it is very easy to change the DC voltage Vd during the period until it reaches the rated DC voltage and the period after that when starting the DC power transmission system shown in FIG.

Using a computer, it is possible to gradually change the upper limiter LMX and lower limiter LMN of Type 0 at each sampling time. Since the first-order delay calculation does not suddenly stop as described above, it is possible to reduce fluctuations in the DC power transmission system.

〔Effect of the invention〕

As described above, according to the present invention, in a constant power control device used for a power conversion device such as a DC power transmission or a frequency conversion device, which operates while coordinating a forward converter and an inverse converter, it is possible to adjust the power setting value and transmit the power. ? ! ! In addition, upper and lower limiters are attached to the control calculation that detects the deviation from the power and controls the transmitted power so that it becomes equal to the power set value, and limit the upper and lower limits of the output value. During a certain period of time when the deviation between the power setting value and the transmitted power becomes large due to power flow reversal, etc., the upper and lower limit values of the upper and lower limiters are changed over time, so that the power converter is activated or the power flow is reversed. Even if the power setting value and the transmitted power differ significantly due to the above, the response of the constant power control device can be adjusted, so disturbances to the DC power transmission and frequency conversion device can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the constant power control circuit according to the present invention, FIG. 2 is a diagram explaining the operation of the constant power control device according to the present invention, and FIG. 3 is a diagram showing an example of a DC power converter. Terminal power transmission system diagram, Fig. 4 is its control characteristic diagram, Fig. 5 is a block diagram of its control device, Fig. 6 is a diagram explaining an example of a constant power control device, Fig. 7 is a primary diagram used in Fig. 6. FIG. 8, a conventional circuit diagram of a delay control circuit, is a diagram illustrating the operation of the constant power control device of FIG. 6 according to the conventional example of FIG. 7. 1.20.121... operational amplifier 131-134.
・Resistor 140...Capacitor 150...
Switches 151, 152... Upper/lower limit limiter agent Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata Figure 1 1 dp Figure 2 Figure 3 ct Figure 4 Figure 5

Claims (1)

[Claims] In constant power conversion control devices used in power conversion devices such as DC power transmission and frequency converters, which operate while coordinating forward and inverse converters, the transmitted power is determined by detecting the deviation between the power setting value and the transmitted power. In addition, upper and lower limiters are attached to the control calculation that limits the upper and lower limits of the output value so that the output value is equal to the power set value, and the power set value and the transmitted power are 1. A constant power control method for a power conversion device, characterized in that the upper and lower limit values of the upper and lower limiters are changed over time during a certain period of time during which the deviation from the upper and lower limiters increases.