JPH0668710B2 - Voltage fluctuation suppression device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voltage by an unbalanced voltage detection device provided for suppressing a fluctuation of a bus voltage when the bus voltage of a power system is unbalanced and fluctuates sharply. It is related to a fluctuation suppressing device.

[Background technology and problems]

An example of the voltage fluctuation suppression apparatus used for the above-mentioned purpose of FIG. 1 is shown.

In the figure, 1 is an infinite bus, 2 is a power source impedance, and 3 is a bus. Reference numeral 4 is a series reactor, which is directly connected to the thyristor switch of 5, and this and the parallel capacitor 6 constitute a reactive power compensation circuit indicated by a dotted line.

However, this reactive power compensation circuit does not have to be the reactor current variable type (commonly called TCR method) as shown in the figure.

The series reactor 4 controlled by the thyristor switch 5 is Δ-connected between the three phases as shown in FIG.

Returning to FIG. 1, 7 is RT, 8 is a controller surrounded by a dotted line, 81 is a voltage detector, 82 is a subtractor, 83 is a controller, 84 is a pulse generator, P. The bus voltage from T7 is compared with the reference voltage Vref by the subtractor 82, and the difference voltage is input to the controller 83, and after performing a specific calculation, its output is input to the pulse generator 84 and this pulse The ignition phase of the thyristor switch 5 is controlled by the output of the generator, the energization of the series reactor 4 is controlled, and the fluctuation of the bus voltage is suppressed.

The control device 8 including such a voltage detection system is provided for each line and controls the thyristor switch 5. However, the voltage change due to the unbalanced load also affects other unrelated phases, and thus the lines There are the following problems only by detecting the voltage.

Figure 3 B illustrates a circuit diagram of a case where a single-phase reactor X _L is loaded to the system. However, the resistance of the power supply impedance of the system is ignored.

At this time, the relationship between the phase voltages is shown in FIG. 3A. Assuming that 81 shown in FIG. 1 detects the line voltage Vuv,
As shown in FIG. 3A, a balanced line voltage V is generated between u and v.
suv will change to Vuv, and vw
Similarly, between w and u also changes.

However, considering the case where such a single-phase reactor load suddenly occurs and the fluctuation due to the load is suppressed as soon as possible, the voltage drops across u-v, v-w, and w-u. Therefore, each phase control circuit is connected to the series reactor 4
Current is squeezed to increase the bus voltage.

In reality, only the u-v reactor needs to operate, but since all phases operate and they interfere with each other, fluctuations are suppressed, so it takes time to reach the target value. .

In other words, even in the conventional method, the fluctuation is finally suppressed in a settled state, but it is difficult to quickly respond to the sudden fluctuation.

DISCLOSURE OF THE INVENTION As described above, according to the conventional voltage fluctuation suppressing device of this kind, there is a problem in the control device, and the present invention detects the voltage due to the unbalanced load, and In a circuit that tries to suppress voltage fluctuations, each line voltage is detected, the line voltage fluctuation corresponding to the reactive power compensator of each phase is multiplied by 5, and the other two phases are subtracted from the sum of the fluctuations. By multiplying the result by 2/9, each phase will be independently converted into information that should be compensated for voltage fluctuations without being interfered with each other, and it will be used in the reactive power compensator. In addition, the bus voltage fluctuation can be quickly suppressed when the fluctuation fluctuates sharply.

An embodiment of the control circuit of the present invention shown in FIG. 4 will be described below.

The circuit of FIG. 4 is composed of the PT7, voltage detector 81, and subtractor of FIG.
The part consisting of 82 is indicated by a three-phase circuit, and the control information forming part connected to this is shown.

First, each phase voltage is Input in PT of connection. If the secondary neutral point of PT is used as the common terminal of the subsequent control device, the line voltage of the bus bar can be measured by the PT. Next, voltage detectors 81 ₁ , 8
1 _2, 81 ₃ with line voltages Vuv, converts Vvw, the Vwu to DC, versus the reference voltage Vref by the subtracter 82 calculates the difference (line-to-line voltage variations) ΔVuv, ΔVvw, the DerutaVwu.

The three control amounts ΔVuv, ΔV obtained as described above
Input vw and ΔVwu to the arithmetic circuit surrounded by the dotted line 85 in the figure,
Three control variables ΔV′uv and ΔV′v defined below
Determine w, ΔV′wu.

851 is an adder, 852 is a 5 times multiplier, and 853 is 2
/ 9 times the subtractors.

These ΔV′uv, Δ′Vvw, and Δ′Vwu are input to the controller 83 of FIG. 1, respectively.

That is, the reactive power between the lines is independently calculated by ΔV ′.
This means that it is only necessary to control the values so as to compensate uv, Δ′Vvw, and Δ′Vwu.

According to such a signal, the previously used signal, Δ
Unlike Vuv, ΔVvw, and ΔVwu, even in the example shown in FIG. 3, the target value to be controlled independently for each phase can be known without mutual interference.

The above is the description of the configuration of the present invention.
The basis for deriving Eq. (1) is shown below.

As shown in FIG. 2, the currents u, v, w are determined.

Fig. 1 uv, vw, wu by the pulse generator 84
Are controlled to flow as currents u, v, and w on the bus 3. As a result, uv of the bus bar 3
The voltage between V, V, and W is controlled, and the influence of the bus voltage fluctuation due to uv, vw, and wu is analyzed below.

First, when the standard of Bertrel is set to the voltage between u and v as follows, However, On the other hand, u, v, v, w
If the fluctuations due to v and w are Δuv, Δvw, and Δwu, and the power source impedance is jXs, Becomes

Here, there is the following relationship between u, v, w and uv, vw, wu.

The following equation is obtained from equations (2) to (4).

Therefore, the uv voltage fluctuation width ΔVuv is expressed by the following equation.

Similarly, using the voltage between v and w as a reference vector, (2) to (5)
Considering the process of the formula, Similarly between w and u, The formulas (5) to (7) are summarized in the following formula (8).

Here, the bus voltage fluctuations when uv, vw, and wu individually flow are ΔV′uv, ΔV′vw, Δ.
If V'wu, From equations (9) and (8), the following equation is obtained.

[Operation and Effect] Considering the example of FIG. 3, Conventionally, since the above value is directly used for the line reactive power control of the corresponding phase, the phase u having a load that causes a fluctuation
The phase (vw, wu) suppressor other than between -v worked and was not efficient.

However, according to the detection device of the present invention, from the equation (1), That is, the voltage fluctuation is detected only between uv and v-w.
During this period, no voltage fluctuation is detected between w and u. Due to this signal, the reactor is controlled so as to increase the voltage only between u and v, and the reactor between vw and wu does not require control operation. , It is possible to perform proper and high-speed control without receiving interference from other phases.

Although the variable load has been described as an example of the single-phase reactor, it is needless to say that the same measure can be applied to any unbalanced load.

Although the variable load has been described as an example of the single-phase reactor, it is needless to say that the same measure can be applied to any unbalanced load.

If the current of the load causing the voltage fluctuation can be measured, the reactive power of the load is detected, and its output signal is added to the output of the regulator 83 in FIG. 1 to control the reactor. The residual voltage fluctuation amount of the reactive power detection control described above works in such a direction as to be corrected by the control system of the present invention.

As described above, the present invention can quickly suppress unbalanced voltage fluctuations.

[Brief description of drawings]

FIG. 1 shows an example of the voltage fluctuation suppressing device. FIG. 2 shows the connection of a series reactor controlled by a thyristor switch. FIG. 3B is a circuit diagram when a single-phase reactor is loaded in the system, and FIG. 3A is an explanatory diagram showing a change in interphase voltage when the single-phase reactor is loaded. FIG. 4 shows an example of the control device of the present invention. 1 ... Infinity bus, 2 ... Power source impedance, 3 ...
Bus line, 4 ... Series reactor, 5 ... Thyristor switch, 6 ... Parallel capacitor, 7 ... PT, 8 ... Control device, 81 ... Voltage detector, 82 ... Subtractor, 83 ... Regulator,
84-Pulse generator.

Claims (1)

[Claims] 1. A circuit for detecting a voltage due to an unbalanced load and for suppressing this voltage fluctuation by a reactive power compensator, detects each three-phase line voltage and detects a line voltage fluctuation which is a difference from a reference voltage. And calculate one of the voltage fluctuations by 5
By multiplying it, subtracting it from the sum of the other two voltage fluctuations, and multiplying the result by 2/9, the information is independently converted into information that should be compensated for voltage fluctuations without interfering with each other. A voltage fluctuation suppressing device characterized by being used for control of a reactive power control device.