JPS5858835A - Method of controlling 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 The present invention relates to a method for controlling a power conversion device that controls the amount of power flow between two different power systems.

Japan's electric power system consists of a 60Hz system in western Japan and a 50Hz system in eastern Japan.
0 Hz thread system C can be clearly distinguished by two people.

As devices for connecting these two power systems and controlling the power lvl between the systems, there have been rotary frequency converters using a conductor or the like or static frequency converters using a mercury rectifier. Recently, static frequency converters using semiconductor-controlled rectifiers such as thyristors in place of mercury rectifiers have been put into practical use.

In addition, there are many power systems managed by several power companies within the 501 (Z system), and their voltage ratings and equipment capacities vary. Therefore, AC → DC →
A converter device is used to exchange AC. Special C
The above DC power line with a longer distance is well known as a power converter for DC power transmission.

Figure 1 shows a configuration diagram of a conventional power conversion device.
A case is shown in which a 50 Hz system and a 60 Hz system are connected and the electric current m between the two systems is controlled.

In the figure, BUS1 connects 50H2 to the three-phase power line of the power system, and BU
8g is the 3-phase power line of the 60H2'tjL power system, '[
'R1, TRg is a power transformer, 8S1. ss2 is an AC 1fiL power converter consisting of a thyristor bridge circuit.
IIO is a DC reactor, CAPJ and CAP2 are phase advance capacitors, and 8VO1 and 8VO2 are reactive force detection devices.

1. The operation of this device will be explained by taking as an example the case where a plow and power are sent from the electric line BUS1 of the 50 Hz system to the 1JL Momiji BUZZ of the 60 Hz system.

A current detector 0T81 and a voltage detector PT81 are installed at the receiving end from BUS1 to detect instantaneous values of voltage and current of three phases. This is input into active reactive power calculation circuits PQ and CI to obtain active power PI and reactive power Qt. Similarly, BU
The power receiving end C2 from S2 is also equipped with a current detector c'rs 8 and a voltage detector PTsl, and an active reactive power calculation circuit P.
Active power P2 and reactive power Q2 are detected together with Qog. Pl detects the incoming direction as positive, and P2 detects the outgoing direction as positive. Further, Q1+Qz detects delayed reactive power as positive and leading reactive power as negative.

For power flow: Power command value P8〉0 by setting device VRPC
is given. When P8>0, the Schmitt circuit SH generates an output (H number 111) and switches the switch SWI to the α side and provides the switch sw2 to the C: connection. Therefore, the power converter 88
1 is a power flow tP-(P
The output voltage Vl is controlled so that l+Pz)/2 becomes equal to the command value P8, and the power converter ss4 is controlled by the foot voltage control circuit AVR1m so that the output voltage v2 becomes constant 1V. be done.

PJ+PH24' are phase control circuits 881 and 882, respectively. FIG. 2 is a voltage-current vector diagram for one phase on the AC input side of each power converter at this time. (a) is a voltage and current vector diagram of 881, and (b) is an I/1ssj cD voltage and current vector diagram. In the figure, vs l + vs ! istm'
tc pressure, ICapl + engineering. apl is phase advance capacitor 0
Current of AP1 and cAp2, 881. ■881 Fi
Input current of power converter 881 and sel, ■88B, ■
884 is a reactive power compensator fJILsvcl and 8VC9
is the input current. Blood flow reactor L. Create a current that flows. In the case of binding, if the conversion constant is 4, the process is 881 ”
■882 ''' A・Eng. If the above DC current is in a steady state and the resistance of the DC reactor L0 is negligible and small, then the output voltage Vl of ssl and ss
The output voltages VpH of B must be equally balanced. Each ignition control angle is αl and α8, and the power supply voltage is V.
B l+ vs Z If the s conversion constant is AV and f, then Vl
:=Av 0VB10cmα1 V2=-AV -VB2 If we assume that O VB1 =V82 where there is a relationship of ° part α2, then Vl =
In the Vg state, the relationship α2 = 180°-αl holds true.

When sending power from electric line BUSl to electric line BUSB,
sel it forward converter, 881! acts as an inverse transformer.

The firing control angle α2 of the constant voltage controlled inverter sSg is 9
It is set to a certain value between 0° and 180°. α, = 180'
When , the power factor on the input side becomes 1 (2) α21 = 1, but in order to allow the thyristor to naturally commutate, the C two-strike timing r
I just have to move forward. In general, r is the same as the commutation advance angle. Therefore, C2α2=180′−r=set to constant. In this state, the flow rate of the drawer M is controlled by the converter 881. The input pressure of SSl and 882 is Vllll
” While VS2 = constant, the power is proportional to the active current components of 1881 and 882, l and pZ.I, l and Ip2 can be expressed as numbers in the following equation.

Work pl = 4 - Work 0° House αl ■, 2 = 4・Work.・In the state of smooth α2 6g = 180'-αl, Ipl = -engine, 2
It can be seen that the following relationship holds true, and the active power entering the forward converter Eel is equal to the active power exiting from the inverse converter ssB.

Power flow b: Controlled by changing the magnitude of DC current. Current current, current current. is DC reactor-L.

(2) O controlled by changing the applied voltage vl + VB Since v2 is controlled constant bVl”
It is controlled by changing Av-VBl-cosαl. ■. If you want to increase s vl > VZ, control αl and conversely. If you want to decrease Vl
52αl is controlled so that <VB. Near the steady point, the resistance of the accelerator L0 that flows directly can be ignored, Vl = V
The relationship g holds true, and the flaw αl''--the cap α2.

(On the other hand, the reactive power at the receiving end of the converters SS1 and EIS2 is controlled as follows. In other words, in the vector diagram of Fig. 2, the relationship of the following equation is established, 88
and controls the value of 884.

BB iA qo 1gt from Koapl””■i1+
o “1 + 工sss 工QQp2”’■? 2 + engineering 884 =
AHIo' tinα! "If you change the set value P* of the 1884 power flow rate, the DC current and current will change and the power SSS and 1884 will be controlled accordingly.

If the above relational expression holds true, the current supplied from BUS1 will be AOI, 1, and the current supplied from BUEI2 will be AO2, IpB = -■, 1, resulting in the fundamental wave power factor at the receiving end. is held at 1, and only active power is sent from BUSI to BUS No. 2.

When the power-flow rate set value P* is set to a negative value, the switch SW
I is connected to the b side, switch EIWfi is connected to the α side, and this time, the 60Hz system power line BUZZ is connected to the 50Hz system!
Power will now be sent to line BU81. At this time S
ol# is used as an inverse converter to perform constant output voltage control, and 5szrj is used as a forward converter to perform DC current control.

This conventional power converter fIIL has the following drawbacks. In other words, DC current is used to control the power flow rate. is increased or decreased, but the change C is accompanied by the reactive current component Itl = AI on the input side of the converter E]81 and ssB. Output αl and It2 = A Io output α2 also changes, and the reactive power compensator 5vc changes according to the change.
It is necessary to control the current l8BB+l884 of 1 and BVC2. This reactive power compensator ft 5vc1.5V
(The capacity and weight of 14 is the maximum value of DC current ■0. If (Otori)
84: 工 aap
2-Iy2 = 4 (ko(wc) -Iotomα
2, and considering the relationship αl"=γ, α2 = 180°-r, and considering that the above k changes between 0 and k.
$r is required. As mentioned earlier, r is the commutation advance angle required for natural commutation of the thyristor of the i-electric power converter, and is related to the inductance on the power source side, the turn-off time of the thyristor, etc. %≦2 The former is a fairly large value because it prevents the arm short-circuit accident of the converter. Therefore, r is usually 1: at @ of 30° to 40°. Even if r-30°, rrtrrr = 0.5, and the capacity of the reactive power compensator [5VO1 and 5V (4) becomes half the value C2 of each award of the power converter ssl and 88g.

Therefore, there was a drawback that the device was expensive and complicated.

The present invention has been made in view of the above, and the fundamental wave power factor at the power receiving end can be constantly adjusted to 521 without using a conventional reactive power compensator.
and the power flow between the two power systems 1iI-
An object of the present invention is to provide a control method for a power conversion device that can freely control f-sub.

FIG. 3 is a configuration diagram showing an embodiment of the power conversion device of the present invention. In the figure, BUS1 is connected to the first power system (for example, 50
H2 system) 3-phase power line, BU8i is the 3-phase power line of the second power system (for example, 60H2 system), C! API.

CAP2 is a phase advance capacitor, TR1 and TR9 are power transformers, 881 and S82 are AC/DC power converters consisting of thyristor bridge circuits, and LO is a DC reactor. In addition, CTo is a DC current detector, 01=(4 is a comparator, AI to A8 are adders %K(LKI is an operational amplifier, M
1+MB is a conventional circuit, Ht(8) and Hp(8) are control compensation circuits, %SQ is a square calculation circuit, 8QR is a square root calculation circuit, LM is a limiter circuit, PHI and PJ are phase control circuits.

First, the control operation of the voltage on the DC side will be explained. For simplicity of explanation, we use DC current. Keso command value engineering. Consider a condition containing control equal to 8.

The output a of the control compensation circuit Hp(8) is sent to the phase control circuit PH1 via the adder AI, and then to the inverter tIII width amplifier! (=-1) and are respectively input to the phase control (b) path PHg via the adder A3. ■. = Engineering. 8, the output ε of comparator c2, =I■8-■. is zero. Therefore P
H1 and PI (2 input voltage ET, 1.111 is νal
"Ua νg2 = -ua. Therefore, the firing phase α2 of the 882 is α2=180'-α1 for the firing phase α11 of the power converter Sex, and the output voltages Vl and VSl of each are balanced. C2 is operated at C2.G2, which increases Vl = V9, increases the output value v1 of the control compensation circuit H, (8).

Bye.

Next is DC current. DC current detected by current detector CT0.

and its command value engineering. ′ and its deviation, z = knee
■. Take out. The deviation c8 is amplified by an amplifier KQ and input to adders AI and A4. Therefore, the input voltage "b l'*2 of the phase control circuits PH1 and PH2 is ν
al −να + KO・ε2 ν, B = −va +KO”2. Therefore,
The above relationship αB = 180'-cl collapses, KO''
Vl increases by an amount proportional to 2, and Vfi decreases. The difference voltage Vl - vB is applied to the DC reactor L0, resulting in a DC current. increase.

■. 〉■. In this case, it becomes 62〈o, and vl〈v2
So, it is a direct current tortoise current. decrease. Finally, ■.

-Eng. It settles on a tree, becomes Fivl-Vg in a steady state, and satisfies the relationship α, valve 180'-αl.

Next, the active power control operation and reactive power control operation of this power converter will be explained.

Input voltages ν#1 and v of phase control circuits PHI and pH2
It is known that l is proportional to the cosine value of the firing phase angles α1 and α2, respectively.

There is a relationship as shown in the following equation between the output voltage Vα of the control compensation circuit Hp(8) and the input voltages El, 1 and 11g2 of the above-mentioned PH1 and PH3.

v, = (1g1 + va2) / 2-Aa (μs
αl 14 αz)/where Am is a proportionality constant.

Therefore, by detecting the above v1 and multiplying it by the coefficient (1/Aα), the average value of the cosine value of the firing phase angle is calculated as follows:
l + billion α2)/2 is found. The limit circuit LM has the above proportional coefficient (1/a,
) within the range satisfying -1≦■α≦+1 (2).

Square calculation circuit BQ + adder A3 and square root calculation circuit SQ
Using R, calculate J 1-cm"cL.

This value is equal to the sine value αj1 of the phase angle α.

Multipliers M1 and M2 are DC current value processors. and the said waxing value ・
It multiplies S-α and cosine 4fjicmα, and each output value is Iy=(2).・Okina α Ip = I.・Cap α is required. Former engineer? is the power converter ssl and ss
2 is the average value of the reactive current at the end of the receiver 14L, where the latter is the average value of the reactive current.

Reactive current command value? The reactive current detection value t is compared with 6 cl, and the deviation εl=knee-Iy is input to the next control compensation circuit Hy, (8) l-manually. Steady deviation g1
In order to make the value zero, an integral element may be used for the above Hi(8). The output of H, 1, (8) is the DC current command value. It becomes 8. ■t-work? In this case, cl becomes a positive value. Increase 8. Therefore (output deviation ε2 of the two comparators c2
= Engineering. ′-Eng. increases, s Vl > V2, and the DC current Io increases, but at this time, va :" (
v,1 +v,2)/2 does not change. Therefore, ■,=
Engineering.・Inner α increases and ■? -Work-! +1
@l will be done. Even when it becomes rice, it is controlled like In2, and eventually Iy = knee.

It's a moat, the effective current command value - and the effective current command value.

are compared by the comparator C2, and the deviation c8=work is input to the next control compensation circuit Hp(8). In order to make the steady-state deviation εl zero, an integral element is sometimes used for s Hp(s).)1. The output of (8) becomes a signal ν that determines the average value of the output voltages Vl and v2 of 881 and 8192.

(2) In the case of <I, #B>Q and Vα is increased. Even if v is changed, the state of Vl = v2 is maintained, so it is a direct current current. It doesn't change. v, =: Since there is a relationship between Aa and tassel α, ■, = engineering.・Part α increases, ■,
= knee is controlled by C2. In the case of (2), > (2), ε8 becomes 0, Zl is decreased, and the control is performed so that the equation becomes = (2) -.

First power system @ BUSl to second power system BUSI
If you want to send power to , you can control by setting ■, '>01. Conversely (2) When sending power from BUEI2 to BUS1, control should be performed by setting it to <0.

Here, engineering, control system and engineering 9. Consider the mutual influence of control systems.

■When - is increased, the damage α increases so that ■,=knee. Therefore, α = JTaye” a- decreases, =
Engineering.・Decrease output α. Therefore, in order to become a labor force, ■? = Engineering? 1 nie to make it 8. increase.

As a result, ■, =I0・□□□α also increases, and
becomes. Therefore, this time the circle α is decreased and the operation is reversed.

The above vibration phenomenon is repeated several times, and finally,
, II = IfP' l2. How quickly this vibration phenomenon can be reduced depends on how the control constants of the control compensation circuits Ht(8) and Hp(81) are selected.

However, if ordinary automatic control theory is used, optimization can be easily achieved using C2.

Similarly, when the knee is decreased by 1, and when the knee is increased or decreased by 1,000, the vibration is controlled so that it settles down after passing through the vibration phenomenon.

In other words, work steadily, = work 1. A direct current current that satisfies the requirements of engineering, = engineering, and *. and the cosine value ■α of the phase angle α.

FIG. 4 shows a voltage-current vector diagram for one phase on the AC input side of each power converter shown in FIG.

(α) is a voltage-current vector diagram of SSL (7), and (b) is a voltage-current vector diagram of 882. va 1 + v
92 is the power supply voltage, ■. , p l + Eng. apil is the voltage a of the phase advance capacitor 0APl and ahpB, ■881
The input current 88B is the input current of the power converter 881 and ss2. Engineered 11 DC currents. In the case of binding, if the conversion constant is 4, there is a relationship of 881 = 8ElB 4.

Considering the steady state, Vl and v2, and the firing phase angles of 8Sl and ss2 have a relationship of α2≠180°−cl. Separate the work 881 into effective parts I, l and ineffective parts, l, and perform direct f & 11 flow machining. Play around with the relational formula between ding and kopl: kos
e1'cosα1=J Engineering Oaαl Engineering tl= Engineering 881--
α1 = J engineering. The image becomes αl. In addition, the engineering ssg
The DC current is separated into a reactive component It2 and a reactive component It2. Using the relational expression, ps = 5 sli° - αg = A □ ayt α 2 ng f 2'' 88z° tuft αz = 4 ng. (2) α2.Here, α8'' = 180° - cl. If you include the relationship,
Key (2) α1 (α αl i α2 ≠ α Since it becomes, the control amount in Fig. 3, = engineering. (2) α, engineering, = engineering. Substitute α into the above relational expression. Ipi Misaki AI.

Engineering? L Cape 4 construction? ■1. Valve-4 engineering p engineering? 26A engineer? becomes. Ioap2 and the above lagging reactive current It of the phase advance capacitors CAPl and 0AP2
If the reactive power 1 and the film constant value I are selected so that lkieti is equal, the reactive power at each power receiving end of the power converters 8Sl and 882 becomes zero, and the fundamental wave can be realized without providing a conventional reactive power compensator. Operation with power factor = 1 is possible. On the other hand, if the shoulder effect set value BUZZ is selected to stop, then PI > OwIpil becomes 0, and the active power is sent from the first power system BU81 to the second power system BUZZ, and BUZZ is selected to be negative. If Ipl
＜O+ Eng, 2＞o, and the effective power becomes B[T
8fi to BUSI l second speed. In other words, by changing C, and C2, various values of the power flow amount can be selected.

As described above, the power converter of the present invention maintains the fundamental wave power factor at the power receiving end at C21 without using the conventional reactive power compensator, and the power converter of the present invention It is possible to freely control the tidal current source (7).
Uke I! In controlling the reactive power at the end, the blood flow tiL flow detection value is used. Since the reactive t#L is directly calculated and controlled from the cosine value (2) α of the firing phase angle, current transformers, transformation gain, etc. are required to detect the reactive power at the receiving end, which was conventionally required. , and the problem of detection delay is also eliminated, making it possible to achieve a control system with extremely good responsiveness.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional power converter, and FIG. 2 is a voltage and current vector diagram at one end of the receiver of the device shown in FIG. FIG. 3 is a block diagram showing a simple embodiment of the power conversion device of the present invention, and FIG. 4 is a voltage-current vector diagram at the receiving end of the device shown in FIG. 3. BUSI, BUS2... electric lines of the first and second power systems, 0AP1. CAP2 = phase advance capacitor,
TR1, TR2 - power transformer, eel, ss2...
・Direct current converter, LO...DC reactor, C
To...DC, current detector s cl, CBm C
B... Comparator, Al, Ag+ A8... Adder,
:KO+KI...Operation amplifier, My(8), Hp
(8)...Control compensation circuit, LM...Limiter circuit,
SQ,...square calculation circuit % 8QR...square root calculation circuit s Ml+Mg...multiplier, PH1, PH2
...Phase control circuit.

Claims (1)

[Claims] The AC side of the first AC/DC power converter is connected to the first power system, and the AC side of the second AC/DC power converter is connected to the second power system (two connected and A power converter device in which DC sides of the two power converters are connected through a DC reactor so that direct current fJtL*k in a constant force direction flows (-, phase control of the two power converters is performed. From the input signal, calculate the cosine value width α and the sine value −α of the ignition control angle α, and multiply those values by the detected value of the DC current controller (2, therefore, the Ume-effect Kanryu ratio, = the current value).
part α and reactive current Iy=I.・Determine the force α, compare the reactive current command value ** and the reactive current value above, and find the deviation? According to the above DC electrician. between the first and second power systems by controlling the DC side voltage of the two power converters in accordance with the deviation C and comparing the effective current command value K and the effective current Power flow rate and front h pi 2
A method for controlling a power converter, the feature of which is controlling reactive power at the receiving end of two power converters.