JPS5843017A - Controlling system for power generating device of power distribution system - Google Patents

Abstract

PURPOSE:To prevent an increase of the width of the load voltage fluctuation which is caused by the connection of a power generating device, by starting the supply of a phase-advanced reactive current at a time point when the load voltage is approximate to the set upper-limit voltage and then controlling the output current of the generating device. CONSTITUTION:A power generating device 1 is provided with a power generating element 11, a DC filter containing a smoothed reactor 12 and a capacitor 13, and an inverter 14. The pulse width of the inverter 14 is modulated by a control circuit 16, and the output of a waveform synthesizing circuit 17 is applied to the circuit 16. The load voltage that is detected by a voltage detector 18 plus the input signals of an active current operating part 19 and a reactive current operating part 20 are applied to the circuit 17. The active current command value given from arithmetic part 21 for an active current command value is fed to the part 19 and a reactive current command arithmetic part 22. The reactive current command value given from the part 22 is transmitted to the part 20 via a characteristic changing element 23.

Description

[Detailed Description of the Invention] The present invention relates to a control method for a generating device that is interconnected to a system i, and its purpose is not to support the modification of the system configuration of M. , Is it acceptable? The goal is to allow all electrical devices to operate in a grid-connected manner while maintaining the same width.

In the distribution system, the voltage and voltage of low-voltage loads connected from the high-voltage bus through pole transformers is generally 101±6V...Also, low-voltage loads can usually withstand 101±10V. It is designed to. In other words, the permissible voltage fluctuation range is 201. Conventional power distribution systems are configured and operated in such a way that the load fluctuations (voltage) are well within this allowable fluctuation range.Since the oil crisis, fuel cells and There is a trend that many distributed inert power generation devices will be used in the future as new energy sources such as solar cells. It is in the direction of being operated in connection with the grid.

In cases where the single power generation capacity is small (for example, a home solar power generation system), a pole-mounted transformer is connected to a secondary low-voltage circuit power generation system, and as power generation systems become more popular, it is possible to connect to a high-voltage system during light loads. Reverse power transfer occurs, and the voltage fluctuation range at the load end expands due to the rise in the end load voltage.From this point of view, it becomes necessary to reconsider the system configuration.

The following problems will be explained in more detail using specific numerical values.

5111g4 (as shown in Iζ, using the circuit constants commonly used for low voltage systems connected via a single-phase, 50 KV pole transformer T, with the high voltage bus as the constant voltage receiving point) Let's move on to the discussion. The impedance of the transformer is 3-, the load is single phase, 50KV, and the power rate is pt.
= o, ss (late). Low voltage wiring is 60m
m'' hypothetically, the distance at the terminal load t is xooz (m),
10100 (per impedance 0.03 (1+j
(LO8(0). In this case, the following value is found by calculation.

Line resistance Rj; 0.03j (Q) Line reactance Xz = αos, t (Ω) (jll[
r), +, and Figure 3 shows the variation of the load end voltage VL in the above example (*
) and the low voltage wiring length coefficient t.

On the right side of Figure 3, the straight line (person) shows the full load characteristics when only the load L (an example of constant impedance characteristics) is present. When a power generator (an example of constant current characteristics) coexists, the power factor of the power generator is also assumed to be 0.85 for ease of illustration.
6 for power generators 501 and 100- during no-load
11i sex 4-1 sot1. Jf't1. Tjl@ (B)
, (C). As you will see,
When the generator G is not present at the same time, the allowable wiring length to suppress the terminal load voltage fluctuation width to 20% is approximately 112 m. On the other hand, when the generator G is present at the same time, the reverse feed force will be increased during no-load. The allowable wiring length for the load voltage to rise and maintain the fluctuation range of 20- is the power generation device 1001.
1, the length would be shortened to about 47 m.

As is clear from the above, when connecting a power generation device to a power distribution system, it is necessary to review the power distribution system, and in some cases, costs may be incurred for changing the system configuration or operational control. , .

One possible solution to this problem is to use an overvoltage relay to disconnect the generator, but this method causes a pumping phenomenon and has poor energy utilization.

Furthermore, a method of stabilizing the voltage by variable control of the reactive power of the power generator using an automatic voltage regulator may also be considered.

However, as shown in the example above, in the case of a power distribution system, the resistance and actance of the line are of the same order, so it is ineffective and requires reactive power that significantly exceeds the effective output of the power generator. l! It lacks reality. Further, it is practically impossible to adjust the voltage of the system while maintaining appropriate mutual power distribution among a large number of small-capacity power generation devices.

The purpose of the present invention is to generate power while using the existing power distribution system as is, without having to review the existing power distribution system. - Depends on the connection. The purpose is to prevent the widening of load voltage fluctuations and enable as many power generation devices and facilities as possible within the capacity of the pole transformer.

The purpose of this is to control the output current of the generator that is connected to the power distribution system by monitoring the load voltage as follows.In other words, when the load voltage approaches the set upper limit voltage, the phase-advanced reactive current When the load voltage reaches the set upper limit voltage, the distribution system calculates the voltage obtained by multiplying the impedance between the running voltage receiving point 7 and the generator by the generator output current and the constant voltage receiving point. ! This is achieved by controlling the magnitude of the vector sum with the voltage to be equal to the constant voltage receiving point voltage or magnitude Ik.

In order to explain the principle of the present invention, FIG. 4 again shows the equivalent impedance between a constant voltage receiving point and a load end as a power distribution system. Regarding this impedance, 1. ζζ
In this case, the combined value of transformer reactance xt and line reactance Xj in FIG. 2 is expressed as X, and the line resistance 8t in FIG. 2 is expressed as 8. The voltage at the constant voltage receiving point and the voltage at the load end are expressed as vectors by B* and VL, respectively, and the magnitude of each vector is expressed by i* and V.
sJ (Furthermore, if the load is the active current IPL and the reactive current IQL lagging behind it, then the load current IL can be expressed as IL = IPL - jIqL. Also, the power generation device () is effective Assuming that a current 1po and a leading reactive current are supplied, the generator output current I can be expressed as Io = Ipo + jlqa.

Now, considering the case of only load (Io=Q), in this case, the following holds true. In the case of -, of course, the power distribution system is configured or operated so that the variation in the magnitude V of the load voltage VR falls within an allowable range. Considering the load end under the worst condition within the allowable fluctuation range, VL (=ER,) = 111V at no load, VL = at full load
It becomes 91V. Therefore, according to Fig. 5, which shows a vector diagram based on the voltage E'' at the constant voltage receiving point, the tip of the vector of the load voltage VR is at point A when there is no load; During direct loading, the point HJ moves to 9.On the other hand, when the output current Io of the generator G exists, it becomes severe due to the reverse power.The output current of the generator G becomes 11・=IF (1+jI
When qa, the load voltage plate at no load is? L-=M inside+
It can be expressed as (R+jX)(Ira+jIQQ). In the present invention, the load voltage VL is monitored, and the power generation device G is started from the stage when the load voltage magnitude VL approaches the set upper limit voltage VLmax (from the stage when VL = VLmax - a). When the supply of phase reactive current IQ (1 is started and VL = Vtmax), the magnitude of the above-mentioned no-load voltage VL becomes the magnitude of iR IBRI =
equals IR. As such, that is, HiR+(a+jx)(xpa+jIqta>l =E
This is to control the output current of the power generator G so that (1) is achieved. According to this control,
In the range VL (VLmax-6, the generator G supplies only the active current Ipo, in which case the premotive current IPQ4g
Since it acts in the direction of increasing the load voltage, there is no time limit for keeping fluctuations in the decreasing direction of the load voltage within an allowable range. Furthermore, in the range of VL>VLmax, even under the worst conditions, the peak of the load voltage vector remains just above the circle indicating the maximum allowable limit (point C) as shown in the vector diagram of FIG. That is, even when there is no load, the magnitude of the load voltage VL can be determined from the magnitude of the constant voltage receiving point voltage BR in the same way as when the generator G is at zero. The value 6 of the invalid portion 1qa to be supplied each time takes a different value depending on the valid portion IP @ each time.

When calculating the invalid component Iqa that satisfies the formula (1) according to the effective component IP (l) in each case, let the calculation formula and BR be as follows. Therefore, in the range of VL > Vtmax, Operating point of power generator G (IPQ, IQG)
G is below the characteristic curve as shown in Fig. 5. In equation (1)'i, R,
Q(s*-bs of 1 is found 0 11g6 Figure shows an embodiment of the control method according to the present invention. In this figure, 1 is a power generation device operated in connection with the power distribution system 8, and 2 is a load. The power generation device 1 includes a light emitting element 11 which is, for example, a solar cell, a DC filter consisting of a smoothing reactor 12 and a capacitor 13, and an inverter 14.
It is possible to compose the force S from . As the inverter 14, for example, a transistor high-voltage type intweeter can be used, as shown schematically for one phase in the block. In this case, the connection point of generator 1 to the grid and in1<-14
It is preferable to insert an AC reactor (15) into each phase connection line between the output terminal of the The inverter 14 is controlled by the control circuit 16 in 4) less wheel modulation. A waveform synthesis circuit 17 generates a control signal waveform to be applied to the modulation control circuit 16 in order to cause a desired output current IQ to flow through the inverter 14. The waveform synthesis circuit 17 is led to a sine wave signal that affects the load voltage plate detected by the voltage detector 18, and is further led to the output signals of the active current operating section 19 and the reactive current operating section 20. The active current command value calculation unit 21 forms an effective current command value from the detected values of the voltage and current of the solar cell 11 so that the maximum output can be extracted from the solar cell 11.The operation unit 19 uses this command. It acts on the waveform synthesis circuit 17 so that an effective current IPG of different values flows.

In addition, this active current command value is also led to the calculation circuit 22, and the calculation circuit 22 calculates the reactive current command - according to the above equation (1'). The element 23, which removes the characteristic changing element 23 and transmits the reactive current to the operating section 20, determines the magnitude VL from the signal corresponding to VL from the voltage detection section 18, and responds to this Vt. It is a variable gain element with a gain that changes itself.
The figure shows the characteristics of the output IQG with respect to VL from the arithmetic circuit 22.
is shown for two different input values from . As we will see from now on, VL (' In the range of VLmax-ε, the gain of element VL is zero, so the power generator 1 supplies the effective current.' VL 〉VL
In the range of max, the gain of the power of 23° is 1 and 6';VLmax−ε<VL
<'VLInaX' range and increases linearly. This allows for smooth changes in characteristics. ′

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a line between a constant voltage receiving point and one load end in a power distribution system, Figure 2 is an equivalent circuit diagram for Figure 1, and Figure 3 is a diagram showing variations in load end voltage and line length. Fig. 4 is an impedance equivalent circuit diagram - Fig. 5 is an explanatory diagram of the relationship between
Figures g and p6 are block diagrams showing one embodiment of the present invention;
The figure is an explanatory diagram of the operation of the example shown in FIG. 1... Generator, 2... Load, 11.
...Power generation element, 12.13...Filter, 14...Inverter, 15...1,000 liters of AC, 16...Modulation control Circuit, 17...
... Waveform combining circuit, 18 ... Voltage detector,
φ 21... Effective current command value calculation section, 22...
...Reactive current command value calculation section, 1st time 2nd time 1st time; 4th time

Claims (1)

[Claims] 1) The output current of the power generation equipment connected to the power distribution system is controlled as follows from the viewpoint of the load voltage i. − Start supplying the reactive current from the stage when the − voltage approaches − −
When the load voltage reaches the set upper limit voltage, the voltage table is calculated by multiplying the impedance between the constant voltage receiving point in the power distribution system and the generator by the generator output current. A control method for power distribution system generators characterized by controlling the constant voltage to be equal to the magnitude of the receiving voltage.゛゛