JPS6334696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Description of the technical field The present invention relates to a DC current control system for an AC/DC converter when nuclear generated power is transported by DC transmission.

(b) Description of Prior Art FIG. 1 shows a configuration diagram of bipolar single-line DC power transmission directly connected to nuclear power generation. In FIG. 1, steam generated in a nuclear reactor 1 is sent to a turbine 2, and the turbine output is connected to a light current bus 5 via a generator 3 and an elevation transformer 4. The AC bus 5 is connected to forward converters 8 and 9 via conversion transformers 6 and 7, and the converters 8 and 9 convert AC power obtained by nuclear power generation into DC power, The converted DC power is further converted into AC power by inverters 10 and 11 and supplied to the load. 12,1
3, 14, and 15 are smooth reactors, 16, 17 are main lines, and 18 is a neutral line.

For convenience of explanation, the pole composed of the forward converter 8, the main line 16, the inverse converter 10, and the neutral line 18 is referred to as _P1 pole,
Forward converter 9, main line 17, inverse converter 11, neutral line 1
The pole composed of 8 is called _P2 pole.

When controlling DC power transmission in such a configuration, as is well known, the forward converter side must control the current setting value.
It is operated by constant current control (ACR) that controls the DC current detection value Id to a constant value based on Idp and DC current detection value Id, and the inverter side is controlled by the voltage setting value Vdp.
It is operated by constant voltage control (AVR) that controls the DC voltage detection value Vd to be constant based on the DC voltage detection value Vd and the DC voltage detection value Vd. That is, point A in FIG. 2 is the cooperative operating point of the forward/inverse converter.

Now, in nuclear power generation, power load unbalance relays (hereinafter referred to as PLURY) are installed for the purpose of detecting load interruptions.
PLURY operates when the change reduction amount and change reduction speed of the generator current each reach a predetermined value, and the principle is to scram the reactor, so for example, if a ground fault occurs in the main line 16 in Figure 1, this Due to the fault current at the time, the PLURY would operate unnecessarily, causing the reactor to scram. Therefore, by designing converters and DC transmission lines in advance so that they can withstand overload for a short period of time, for example, main line 1 in Fig.
6, the converters 8 and 10 are stopped, and the DC current that has been flowing to the P ₁ pole is quickly transferred to the P ₂ pole.
It is necessary to prevent unnecessary operation of PLURY, but this method usually requires _P2 , which is a healthy pole.
A known method is to increase the DC current of the _P2 pole by increasing the current setting value Idp of the constant current control (ACR) of the pole.

However, if unnecessary operation of the PLURY can be prevented by setting the DC current of the P ₂ poles, which are healthy poles, to, for example, 120% of the rated DC current, there will be no problem. If 200% of the DC current is not passed to the healthy _P2 pole, PLURY will operate unnecessarily.
The above methods do not solve the problem.

For example, as shown in Figure 3, point B is the secondary no-load DC voltage on the forward converter side, but the DC voltage on the inverse converter side is due to the impedance of the conversion transformer and the loss due to the DC transmission line. Therefore, the voltage is significantly lower than the secondary no-load DC voltage. Therefore, even if the current setting value Idp is set to 200%, the DC current is actually
The drawback was that it did not flow 200%.

(c) Purpose of the invention Therefore, the purpose of the present invention was to eliminate such drawbacks, and to prevent unnecessary operation of PLURY in the event of a DC transmission line accident, etc. The object of the present invention is to provide a DC current control method for an AC/DC converter that does not cause the AC/DC converter to reach a scram.

(d) Structure of the invention The present invention will be described below with reference to the drawings.

4 and 5 are control block diagrams showing one embodiment of the present invention, with FIG. 4 showing a control block diagram on the forward converter side and FIG. 5 showing a control block diagram on the inverse converter side. In FIG. 4, 19 is a constant current control circuit, 20 is a lower limiter of the control delay angle (hereinafter referred to as α), 21, 22
is a switch that is linked to an accident signal. When an accident signal occurs, switch 21 is turned OFF and switch 22 is turned OFF.
ON, the output voltage of the lower limiter 20 of α is selected, and the output voltage is sent to the phase control circuit 23 that determines the ignition phase, and finally to the gate control circuit 24 that generates the gate signal sent to the converter. , instantly decreases α and increases the DC current. Fig. 5 also has the same configuration as Fig. 4, 25 is a constant voltage control circuit, 26 is an upper limiter of the control advance angle (hereinafter referred to as β), and the output voltage of the upper limiter of β is changed by the fault signal. selected, increasing β and decreasing the DC voltage.

(e) Effect of the invention In this configuration, as above, P ₁
If the main wire 16 of the pole has a ground fault, detect the ground fault at both converter stations, turn off the switch 21 and turn on the switch 22 in _Figs . The converter instantly reduces α to the lower limit of α, and the inverse converter instantly increases β to the upper limiter, so both forward and inverse converters operate to increase the DC current. Therefore, the DC current can be significantly increased. That is, in FIG.
The operating point of the forward/backward converter in steady state is point A,
Even if the current setting value Idp of the forward converter is significantly increased, the operating point only shifts from point A to point C, and it is not possible to flow that large a direct current. However, with the configuration of the present invention, the DC voltage is rapidly reduced on the inverter side, so the operating point A quickly shifts to the operating point O, allowing a large current to flow.

(f) Modification In one embodiment of the present invention, the forward converter side is configured to instantly switch from the lower limiter of α to the upper limiter of β in response to the fault signal, but it is possible to prevent unnecessary operation of PLURY. If possible, it is also possible to increase the current setting value Idp and decreasing the voltage setting value Vdp to significantly increase the DC current by constant current control and constant voltage control. however,
Due to stability issues, it is usually not possible to rapidly increase the current in the healthy pole, especially since constant voltage control has a large delay time constant.
PLURY may operate unnecessarily. In such a case, for example, it is possible to provide two constant voltage controls, one for steady-state constant voltage control and one for high-speed constant voltage control in case of an accident, and to switch between them as necessary. Furthermore, in the explanation so far, we have focused on the output voltage of constant current control and constant voltage control, but instead of this, for example, in the phase control circuit 23 in FIG.
A pulse switching method can also be adopted. That is,
The phase control circuit 23 can also be configured to switch to an ignition pulse having a desired ignition phase depending on the fault signal.

(g) Overall effect As explained above, according to the present invention, when an accident occurs on a certain pole, the accident is detected, and the detection signal of the accident is used to adjust the α of the forward conversion device of the healthy pole.
By forcibly reducing β to the desired value, and forcibly increasing β of the inverter to the desired value, and significantly increasing the DC current of the healthy pole, unnecessary operation of PLURY in nuclear power generation can be prevented. Furthermore, it has the remarkable effect of being able to prevent erroneous scrams in the nuclear reactor.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of DC power transmission directly connected to nuclear power generation, Figures 2 and 3 are operation explanatory diagrams of the DC control system, and Figures 4 and 5 are block diagrams showing one embodiment of the present invention. It is. 1... Nuclear reactor, 2... Turbine, 3... Generator, 4... Step-up transformer, 5... AC bus, 6, 7
... Conversion transformer, 8, 9 ... Forward converter, 10,
11... Inverse converter, 12, 13, 14, 15...
Smooth reactor, 16, 17... Main line, 18...
Neutral wire, 19... Constant current control circuit, 20... Control delay angle limiter circuit, 21, 22... Switch,
23... Phase control circuit, 24... Gate control circuit, 25... Constant voltage control circuit, 26... Control advance angle limiter circuit.

Claims (1)

[Claims] 1. When an accident occurs at a certain pole in a multi-pole single-line or single-pole multi-line power conversion device configured with a plurality of forward converters and inverse converters. Based on the output signal of the device for detecting an accident, the forward converter and inverse converter of the accident pole are stopped, and at the same time, the control delay angle of the forward converter of the healthy pole is forcibly reduced to a desired value, and A DC current control method for an AC/DC converter, characterized in that the control advance angle of the inverter of a pole is forcibly controlled to a desired value to increase the DC current of the healthy pole. 2. Forcibly increase the specified current value of the constant current control circuit of the forward converter of the healthy pole to a desired value, and forcibly increase the voltage setting value of the constant voltage control circuit of the inverse converter of the healthy pole to the desired value. 2. The DC current control method for an AC/DC converter according to claim 1, wherein the direct current of the healthy pole is increased.