JPS6035921A - Synchronization adopting method - 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 is directed to converting alternating current power between a power plant consisting of a plurality of generators or an alternating current system including power plants into direct current power using an AC/DC converter. Synchronous combination when switching from a state in which direct current is being transmitted solely on the power transmission line to AC/DC parallel power transmission by interconnecting the AC/FM line via a interconnection breaker between the AC side ends of the AC/DC converter. Regarding how to enter.

[Technical background of the invention and its problems]

The construction of large-capacity power plants is progressing with the expansion of electricity demand, but due to constraints such as location conditions, it is currently necessary to construct them in areas far from the load side, and long-distance, There is a growing need for large-scale power transmission. However, it is well known that when such long-distance and high-power transmission is performed using a conventional AC power transmission system, the stability of the system becomes a problem.

Therefore, as a power transmission method that solves this stability problem, high-power DC transmission d, which utilizes high-reliability, high-voltage, and large-current thyristor elements based on semiconductor technology, which has made remarkable progress in recent years, has been attracting attention. ing. By applying this DC power transmission technology, it becomes possible to transmit large amounts of power over long distances as described above, but the initial load control when a generator is connected to the grid becomes complicated when transmitting DC power alone. BACKGROUND OF THE INVENTION Due to various system configuration conditions such as eliminating the need for frequency control when generators are under low load, it has become necessary to install both a DC power transmission system and an AC power transmission system to transmit large amounts of power over long distances.

When transmitting large amounts of power over long distances using such DC and AC transmission systems (hereinafter referred to as AC/DC parallel transmission systems),
AC power from the power plant is converted to DC power at an AC/DC converter station, and from a state where DC power is being transmitted solely through a DC transmission line, AC power is converted to AC power by a interconnection breaker at the source end of the AC/DC converter station. There is a process of interconnecting power lines and transitioning to AC/DC/parallel power transmission.

In the process of shifting to AC/DC/parallel power transmission, a continuous line breaker must be turned on after the frequency and voltage phase of the power plant are synchronized with the frequency and voltage phase of the AC transmission line. In this case, in a power plant consisting of multiple generators, even if the frequency and voltage phase of one generator are changed, the change in the frequency and voltage phase of the entire power plant is small, so the alternating current transmission is It took a long time to synchronize the frequency and voltage phase on the wire side.

When the power plant and the AC/DC converter station are installed far apart from each other, the time required for the synchronization is even longer.

[Purpose of the invention]

The present invention was made based on the dual circumstances, and its purpose is to shorten the frequency and voltage phase period of the AC side of the AC/DC converter and the AC transmission line side in the state of DC single power transmission. It is an object of the present invention to provide a cyclical combination method that can be carried out on time and easily transition to AC/DC parallel power transmission.

[Advantage of the invention]

In the synchronous joining method according to the present invention, the AC/DC converter is controlled so that the frequency at the AC side end of the AC/DC converter matches the frequency on the AC power transmission line side, and furthermore, a predetermined amount of electricity on the DC power transmission line side, that is, The above objective is achieved by controlling the AC/DC converter so that the voltage phase at the AC side end of the AC/DC converter matches the voltage phase at the AC transmission line side due to minute changes in power, voltage, or current. ing.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a diagram showing an example of a system configuration in which AC power generated by a power plant having a plurality of generators can be transmitted in AC/DC parallel power to an AC load system. In FIG. 1, PS includes a plurality of generators G1, G2, . ..., a power plant with Gn.

Each generator G, , G2 of this power plant ps. ...t
The output of Gn is connected to transformer T1. T2. . . . The voltage is boosted by Tn and collectively connected to the power plant AC bus line AB.

The AC power of the power station ps is transmitted from the power station AC bus line AB to the conversion station AC bus line AB2 of the AC/DC conversion station CS via the AC power transmission line AL1. In the AC/DC converter station C8, a part of the AC power from the power station PS is transmitted from the converter AC bus AB2 to the substation SS via the interconnection breaker CB and the AC/AC transmission line -5-2. The remainder of the above AC power is transferred from the converter station AC bus AB2 to the converter transformer T0゜nv' AC/DC/DC converter type 1 DC reactor DCR.
It is converted into DC power by the AC/DC converter C0NV, which is constructed by the AC/DC converter C0NV, and is transmitted to the DC/DC converter station CR, which is in reverse conversion operation, via the DC transmission fwDL. This orthogonal transform station C
At R, the DC power is converted into AC power by the orthogonal converter INV, and is supplied to the AC load A together with the AC power from the AC power transmission line AL2 mentioned above.

In Figure 1, PT, PT2 are AC power transmission lines A
A transformer installed on the L converter station AC bus line AB2 outputs detection signals a and b, respectively. Also CT1゜CT
Reference numeral 2 indicates current transformers provided on the AC side and DC side of the AC/DC converter C0NV, respectively, and outputs detection signals c and d, respectively.

Next, referring to Figure 2, from DC single power transmission to AC/DC parallel transmission <V
We will explain the steps to take when migrating.

FIG. 2 shows a control device for the AC/DC converter V in a block diagram. In FIG. 2, Fref is a reference frequency setting circuit that outputs a reference frequency setting signal fref for setting the reference frequency of the AC/DC converter V. FCl is a frequency converter that outputs a frequency detection signal fa1 on the AC power transmission line AL2 side based on a detection signal a from the transformer PT provided in the AC transmission line F4iAL2 in FIG.

FC is a frequency converter that outputs a frequency detection signal fC2 of the converter station AC bus line AB2I111I based on a detection signal from the transformer PT2 provided on the converter station AC bus line AB2 in FIG.

The reference frequency setting signal fref from the reference frequency setter Fref and the frequency detection signal fC4 from the frequency converter FC1 are switched and outputted by a switching mechanism S, and the frequency detection signal fc from the frequency converter FC2 is output. 2 and the comparator COMIK, and the deviation output ΔfVi from the comparator COMI is sent to the divider I.

P is the detection signal b1 from transformer PT2 and current transformer CT
Based on the detection signal C from 1, the converter station AC bus line As2
This is a power detector that outputs a power detection signal P on the side.

BV is set to the converter station AC mains i on the condition that it is switched to the reference frequency ridge setter Fref side by the operation of the switching number structure S.
In order to adjust the voltage phase on the #AB2 side, the DC feed 'It
In the constant power control circuit APR that adjusts the power on the line DL side,
t is a power control signal generation circuit that outputs a force control signal Jpdv. In the constant power control circuit APR, the power command signal pdp from the integrating circuit I is passed through the switch SW to the power detection signal p from the power detector P and the scale force control signal generation circuit B.
It is compared with the power control signal 4Pdv from Y by the comparator C0M2, and outputs the power control signal idp for controlling the power on the DC transmission line DL side based on the difference signal.

This power control signal iap is sent to the constant current control circuit ACH. In this constant current control circuit ACR, the detection signal d from the current transformer CT2 provided on the DC transmission line DL is compared with the power control signal idp in the comparator C0M3, and constant current control is performed based on the deviation signal. The phase control signal phc is sent to a phase control circuit (not shown).

Next, we will discuss the specific control during single DC power transmission in the second section.
This will be explained with reference to the figures. First, the switching mechanism S is operated to compare the reference frequency setting signal fraf and the frequency detection signal fa on the AC bus As2 side of the converter station using the comparator COMf. At this time, the stain force control signal generation circuit BV does not operate due to the operation of the switching mechanism S, and the comparator C0M7 supplies the deviation signal Δf,=fr*f fal to the integration circuit (2) to perform integration processing. The power command signal pdPl is output from the integrating circuit I.
"" Constant power control circuit AP is supplied to constant power control circuit APR and is also supplied to constant power control circuit AP according to power detection signal p from power detector P.
R, controls the constant current control circuit ACR and the phase control circuit (not shown), so that the output frequency of the power station ps, that is, the frequency on the converter station AC bus line As2 side, matches the reference frequency, and the output power of the power station ps is adjusted. Control. Note that to simplify the explanation, power loss in the AC power transmission line AL between the power station PS and the AC/DC converter station CS will be ignored. Further, the switch SW is used to switch from the power command signal pap when DC power is being transmitted alone to the power command signal pap' when AC/DC parallel power transmission is constant.

Next, control at the time of transition from DC independent power transmission to AC/DC parallel power transmission will be explained with reference to FIG. 2.

First, by operating the switching mechanism S, the frequency detection signal f c on the AC power transmission line AL1 side and the frequency detection signal fe2 on the conversion station AC bus line As2 side are compared by the comparator COMI, and the deviation signal 4!2- fC2-fC4 is sent to the integrating circuit (2). Integrating circuit K f (fe2
fa, )dt (K is a constant) are given to the constant power control circuit APR, and the constant power control circuit APR is supplied with the power detection signal p from the power detector P.

Controls the constant current control circuit ACR and the phase control circuit (not shown) to control the output frequency of the power station PS, that is, the AC bus A of the converter station.
The frequency on the s2 side is controlled to match the frequency on the AC power transmission line AL2 side.

Generally, the power receiving system capacity is larger than the capacity of the power station PS, so the frequency on the power station PS side is controlled to match the frequency on the AC power transmission line AL2 side.

Next, by operating the switching mechanism S, the power control signal generation circuit BV is activated after a certain period of time. A power control signal Δpdv is output from the power control signal generation circuit BY and added to the input of the constant power control circuit APR. This power control signal Δ
The DC power on the DC transmission line DL changes slightly in accordance with the pdv, and the frequency on the converter station AC bus line Ag3 changes very slightly and slowly. Therefore, converter station AC bus line AB
The voltage phase on the AC power transmission line AL2 side can be made to match the voltage phase on the AC power transmission line AL2 side.

After synchronizing the frequency and voltage phase between the converter AC bus line Ag3 side and the AC transmission line AL2 side as described above, synchronization is determined by the synchronization detection circuit as shown in Fig. 3, and the interconnection shown in Fig. 1 is performed. Then, the interrupter BC is turned on to shift to AC/DC/parallel power transmission.

In FIG. 4, ΔF is calculated by inputting the detection signal a of the transformer PT on the AC power line AL2 side and the detection signal S of the transformer P2 on the AC bus line Ag3 side of the converter station.
and a frequency deviation detector that detects the frequency deviation of the converter station AC bus line AB2.

LDI is a level detector that outputs No. 18 when the frequency deviation output from the frequency deviation detector ΔF becomes equal to or less than a constant 111. ΔPH inputs the detection signal a of the transformer PT and the detection nfi signal b of the transformer PT2, and calculates the output voltage of the AC v1t, the transmission line AL2, and the AC bus line AB2 of the converter station.
This is a voltage phase deviation detector that detects the voltage phase deviation of .

LD2 is a level detector that outputs a signal when the voltage phase deviation output from the voltage phase deviation detector ΔPH becomes equal to or less than a predetermined value. The above level detectors LDI and LD2
The signal output is the operating signal 8 of the switching mechanism S in FIG.
and is input to ANDf-1.AND. When the input signal satisfies the AND condition, a signal output m is output as a command to close the interconnection breaker CB in FIG. 1.

Next, referring to FIG. 4, the operating procedure shown in FIGS. 1 to 3 will be explained along with the sweep of time t. In FIG. 4, at time t1, the DC power on the DC transmission line DL increases, and the frequency fδ2 on the AC bus line Ag3 side of the converter station becomes higher than the frequency f e 1 on the AC transmission line AL2 side. be. When the switching mechanism S is operated at this time, the DC power increases and the frequency 16□ on the AC bus line Ag3 side of the converter station gradually decreases. At time t2, which has passed for T1 time from time t1, the frequency f on the AC bus line Ag3 side of the converter station
c2 and the frequency fδ on the AC transmission line AL2 side match, and at this time the level detector LD outputs a signal. Furthermore, at time t3, which has elapsed for a time T2 from time t2, the frequency f c 2 on the AC bus line Ag3 side of the converter station changes slightly, but the voltage phase between the AC bus line Ag3 side of the converter station and the AC power transmission line AL2 side changes slightly. match, and the level detector LD2 outputs a signal.

At this time t3, AND GO 1-AND satisfies the AND condition, and is connected to the signal output m to turn on the interrupter CB.

As described above, in this embodiment, the converter station AC bus line Ag3
After matching the frequencies of the AC transmission line AL2 side and the AC transmission line AL2 side, the voltage phases are matched to establish synchronization conditions, and with this synchronization condition, the interconnection breaker CB is set. Moreover, it can be transferred in a short time.

Note that the present invention is not limited to the above embodiments.

That is, even if the output of the power control signal generation circuit BY is added to the constant current control circuit ACH as shown in FIG. 6, the same effect as in the above embodiment can be obtained. The same effect can also be obtained by applying the output of the power control signal generation circuit BY to the voltage setting input of a converter operated under constant voltage control.

Furthermore, the same effect can be obtained by applying the output signal of the power control signal generation circuit BY to the output detection amount feeder loop of the constant power control circuit APR or the current detection amount feedback loose of the constant current control circuit ACH. Needless to say, you can get it.

In addition, in FIG. 1, a plurality of generators G1. G2゜...
The power plant ps and the AC/DC converter station cs', which consist of
It is applicable even if L1 is the same as the converter station AC bus line AB2 (14=-). Furthermore, it is also applicable to AC/DC parallel power transmission in a multi-terminal DC transmission system.

〔Effect of the invention〕

As described above, according to the present invention, the frequency of the AC side end of the AC/DC converter is matched to the frequency of the AC transmission line side between power plants having multiple generators or power systems including power plants. The AC/DC converter is controlled so that the voltage phase at the AC side end of the AC/DC converter matches the voltage phase at the AC power line side due to minute changes in a predetermined amount of electricity on the DC power line side. As a result, the frequency and voltage phase of the AC side of the AC/DC converter and the AC transmission line side can be synchronized in a short time in the state of DC single power transmission,
It is possible to provide a synchronous merging method that allows easy transition to AC/DC parallel power transmission.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram showing an example of the configuration of a power system to which the present invention is applied, and FIGS. 2 and 3 show a 15-rule detection circuit, AND-...and dart. An embodiment of the synchronization V(input method) according to the present invention is shown in a block diagram for clarification.
FIG. 5 is a diagram for explaining another embodiment of the present invention. G1 + 02 +...l Gn... Generator, PS
...Power plant, T1$ T2. ...9 Tn...Transformer, ABl...Power plant AC bus, AL, , AL
2... AC transmission line, C8... AC/DC converter station, AH, converter station AC bus, CB... interconnection breaker, SS... substation, Tconv... converter transformer, ■. ...AC/DC converter, DCR...DC reactor, C0NV...
AC/DC converter, DL...DC transmission line, CR...DC converter station, INV...Auto/DC converter, A...AC load, PTl + PT2...Transformer, CT4. CT2
...Current transformer, Fr.f...Reference frequency setting circuit, F
C, ... frequency converter, FC2 ... frequency converter,
S...Switching mechanism, COMJ, C0M2, C0
M3...Comparator/■-°°integrator circuit, P...Power detector, BY...Power control signal generation circuit, SW...Switch, APR...Constant current control circuit, ACR...・Constant current control circuit, AF...frequency deviation detection circuit, Δl)
H...Voltage phase difference detection circuit, LDI, LD2...
・Repe 16- Applicant's agent Patent attorney Takehiko Suzue 171

Claims (1)

[Claims] AC power between power plants with generators or power systems including power plants is converted to DC power by an AC/DC converter, and DC power is transmitted solely through a DC transmission line. When connecting AC transmission lines between the side ends via a interconnection breaker and transitioning to AC/DC parallel power transmission, the frequency of the AC side end of the AC/DC converter is made to match the frequency of the AC power transmission line side. The AC/DC converter is controlled so that the voltage phase at the AC side end of the AC/DC converter matches the voltage phase at the AC power line side due to a minute change in a predetermined amount of electricity on the DC power line side. The synchronous addition is characterized in that the AC/DC converter is controlled to synchronize the frequency and voltage phase between the AC side end of the AC/DC converter and the AC power transmission line side, and the interconnection breaker is turned on. Method.