WO2006064742A1

WO2006064742A1 - Self-excited reactive power compensating apparatus

Info

Publication number: WO2006064742A1
Application number: PCT/JP2005/022695
Authority: WO
Inventors: Nobuhiko Hatano
Original assignee: The Kansai Electric Power Co., Inc.
Priority date: 2004-12-16
Filing date: 2005-12-09
Publication date: 2006-06-22
Also published as: JPWO2006064742A1

Abstract

A self-excited reactive power compensating apparatus capable of achieving both a high performance and a high efficiency at the same time. In this apparatus, a plurality of power supply circuits (41,42,43), each of which comprises a DC power supply source (C1,C2,C3), which has a charging/discharging function, and a self-excited inverter (I1,I2,I3) connected to the DC power supply source (C1,C2,C3) for converting the voltage of the DC power supply source (C1,C2,C3) to an AC voltage and outputting the AC voltage to the power system, are connected in series with one another, and the voltages of the DC power supply sources (C1,C2,C3) are caused to be different from one another.

Description

Specification

Self-excited reactive power compensator

Technical field

The present invention relates to a reactive power compensator connected to an electric power system and supplying reactive power to the electric power system, and more particularly to a self-excited reactive power compensator using a self-excited inverter.

Background art

[0002] Conventionally, a self-excited reactive power compensator has been installed for the purpose of voltage compensation necessary for improving the stability of an electric power system or power factor improvement necessary for reducing the capacity of a power receiving facility.

In this self-excited reactive power compensator, for example, as shown in Patent Document 1, one capacitor is used as a DC power source, a DC voltage output from the capacitor is converted into an AC voltage by an inverter, and the AC Output the voltage to the power grid.

However, PWM control is used for inverter control of this self-excited reactive power compensator, and there is a trade-off relationship between performance and loss. In other words, in order to improve the performance of the self-excited reactive power compensator, it is necessary to increase the number of switches in order to increase the number of pulses, but this makes it possible to ignore the power loss due to the semiconductor switch elements that make up the inverter. There is a problem that it is impossible to achieve high efficiency.

[0005] On the other hand, in order to eliminate the power loss due to semiconductor switch elements and achieve high efficiency, the number of switches must be reduced as much as possible. If the voltage stability is disturbed or if harmonics flow into the system, problems will occur.

Patent Document 1: JP-A-8-137564

Disclosure of the invention

Problems to be solved by the invention

[0006] Therefore, the main object of the present invention is to provide a self-excited reactive power compensator that solves the trade-off relationship between the performance and the loss at once and achieves both high performance and high efficiency. It is what. Means for solving the problem

That is, the self-excited reactive power compensator according to the present invention is connected in parallel to the power system and supplies reactive power as an output voltage to the power system, thereby adjusting the voltage of the power system and the power of the load. This is a self-excited reactive power compensator that improves the rate, and is connected to the DC power supply having a charge / discharge function, and converts the DC voltage output from the DC power supply into an AC voltage and outputs it to the power system. And a plurality of power supply circuits composed of self-excited inverters connected in series, and the voltages of the respective DC power supplies are made different from each other.

[0008] In such a case, a plurality of power supply circuits having different output voltages are connected in series, and the magnitude of the output voltage can be changed by the combination thereof, so that the entire inverter can be changed. Since the number of equivalent switches can be reduced, a high-performance and high-efficiency self-excited reactive power compensator can be provided.

As a specific embodiment, it is desirable that the voltage ratio of the DC voltage charged to each of the DC power sources is in a power-of-two relationship.

[0010] A capacitor may be considered as the DC power source.

[0011] For example, when capacitors are used, the total sum of energy input and output from each capacitor is ideally zero, but in reality, an effective current that compensates for the loss of the inverter and a harmonic generated by the inverter. Since wave currents flow at the same time, it is necessary to control so that the sum of energy input and output from each capacitor, including these, becomes zero. In order to have the necessity, a control unit that controls a phase difference between the output voltage and the system voltage and adjusts energy input and output between the power system and the respective capacitors is provided. It is hoped that

[0012] In order to achieve higher performance by keeping the voltage of each capacitor constant, when the controller outputs a desired output voltage, the voltage ratio between the capacitors can be set to a predetermined value. It is desirable to determine the operation of each self-excited inverter so as to be as close as possible.

[0013] In order to further enhance the effects of the present invention, the control unit is provided for each of the capacitors for each 1Z4 cycle of AC frequency, for each 1Z2 cycle, or for each integer cycle. It is preferable to adjust so that the total sum of input and output energy is almost zero! /.

[0014] Further, in order to always achieve a high-precision voltage output of 15 levels regardless of the output voltage, the control unit is capable of withstanding voltage performance of components such as a semiconductor switch element, a capacitor, or a rear tuttle, and the like. Based on the current capacity, the upper and lower limits of the output voltage for outputting the reactive power are limited, and within that range, the sum of the voltages of the respective DC power supplies is made as substantially as possible as the output voltage. It is preferable to define the operation for each self-excited inverter.

In addition, the self-excited reactive power compensator according to the present invention is connected in parallel to the power system and supplies reactive power to the power system, thereby adjusting the voltage of the power system and the power factor of the load. A self-excited reactive power compensator that performs improvement, comprising a capacitor and a self-excited inverter that is connected to the capacitor and converts the voltage of the capacitor into an AC voltage and outputs the AC voltage to the power system. Three sets are connected in series, and the phase difference between the output voltage and the system voltage is controlled to adjust the total energy input and output between the power system and each capacitor. Each of the capacitors has a voltage ratio of about 4: 2: 1, and the control unit has a voltage resistance performance of a component such as a semiconductor switch element, a capacitor, or a rear tuttle. And the upper and lower limits of the output voltage for outputting the reactive power based on the current capacity, and within that range, the sum of the capacitor voltages is made approximately equal to the output voltage as much as possible. The operation of each of the self-excited inverters is determined so that the voltage ratio of the capacitors of the capacitor maintains a relationship of approximately 4: 2: 1.

[0016] In such a case, the magnitude of the capacitor voltage is approximately 4 according to the desired output voltage.

: 2: It can be moved up and down while maintaining the relationship of 1, and it is possible to always output a highly accurate voltage of 15 levels regardless of the output voltage.

The invention's effect

[0017] According to the present invention configured as described above, a plurality of power supply circuits having different output voltages are connected in series, and the magnitude of the output voltage can be changed by the combination of the power supply circuits. Therefore, a high-performance and high-efficiency self-excited reactive power compensator can be provided. Brief Description of Drawings

FIG. 1 is a schematic configuration diagram of a self-excited reactive power compensator according to a first embodiment of the present embodiment.

FIG. 2 is a device configuration diagram of the information processing apparatus in the embodiment.

FIG. 3 is a functional configuration diagram of the information processing apparatus in the embodiment.

FIG. 4 is a block diagram showing an inverter control method in the same embodiment.

FIG. 5 is a table showing combinations of output levels of the inverter control method and capacitor voltage conditions at that time in the same embodiment.

FIG. 6 is a view showing the operation timing of each power supply circuit in the same embodiment.

FIG. 7 is a diagram showing charging and discharging of the inverter when outputting an output level 1 voltage in the same embodiment.

FIG. 8 is a diagram showing the results of an operation simulation of a self-excited reactive power compensator using a conventional 3-pulse inverter.

FIG. 9 is a diagram showing the results of an operation simulation of a self-excited reactive power compensator using a conventional 16-pulse inverter.

FIG. 10 is a diagram showing condition settings for an operation simulation of the self-excited reactive power compensator according to the same embodiment.

FIG. 11 is a diagram showing the operation of each inverter in the simulation.

FIG. 12 is a graph showing changes in capacitor voltage in the simulation.

FIG. 13 is a diagram showing the transition of the phase adjustment amount of the output voltage in the same simulation.

FIG. 14 is a diagram showing system current and the like in the simulation.

FIG. 15 is a diagram showing the total value of the capacitor voltage and the operation timing of each power supply circuit at that time.

FIG. 16 is a block diagram showing an inverter control method of the self-excited reactive power compensator according to the second embodiment of the present invention.

FIG. 17 is a diagram showing condition settings for operation simulation of the self-excited reactive power compensator according to the embodiment.

FIG. 18 is a view showing a result of operation simulation of the self-excited reactive power compensator according to the embodiment. Explanation of symbols

[0019] 1 · · · Self-excited reactive power compensator, V · · · System voltage, V · · · Output voltage, 41, 42, 43 · p SVC

• 'Power circuit, Cl, C2, C3' · · DC power supply (capacitor), II, 12, 13 · · · Self-excited inverter, 82 · · · Control unit

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] <First embodiment>

Hereinafter, a first embodiment of a self-excited reactive power compensator according to the present invention will be described with reference to the drawings.

[0022] The self-excited reactive power compensator 1 of the present embodiment includes an AC power source 2 and a load as shown in FIG.

(Consumer) 3 is connected in parallel to the load (Consumer) 3 and the reactive power is supplied to the power system to adjust the system voltage and load power factor of the power system. It is intended to improve.

[0023] The configuration of the self-excited reactive power compensator 1 includes an initial charge for charging initial power to the power supply circuits 41, 42, 43 and the DC power supplies Cl, C2, C3 of the power supply circuits 41, 42, 43. It consists of circuit 5. Here, the self-excited reactive power compensator 1 is configured by connecting the power supply circuits 41, 42, and 43 in series.

[0024] Each part will be described in detail.

[0025] The power supply circuits 41, 42, and 43 are connected to the DC power supply Cl, C2, and C3 having a charge / discharge function and the DC power supply Cl, C2, and C3, and the voltage output from the DC power supply Cl, C2, and C3. It consists of self-excited inverters II, 12, 13 that convert Vh, Vm, VI to AC voltage and output to the power system.

[0026] The DC power sources Cl, C2, and C3 are capacitors, and the initial charge voltage Vh, Vm, and VI have a voltage power ratio of 2 respectively by the initial charge circuit 5 described later.

0 0 0

Each charging voltage Vh, Vm, VI is approximately 2 ⁿ times the minimum charging voltage VI (n = 0, 1

0 0 0 0

Charge the battery so that it becomes 2). In other words, Vh = 2 XVm = 2 X 2 XV1

0 0 0

Electricity. Specifically, AC based on the initial charging voltages Vh, Vm, and VI, respectively.

0 0 0

The peak value of voltage is 60 [%], 30 [%], and 15 [%].

[0027] Self-excited inverters II, 12, and 13 are semiconductor switch elements 111, 121, and 131 and anti-parallel to them. Connected to capacitors Cl, C2, and C3 and converts the DC voltages Vh, Vm, and VI of capacitors Cl, C2, and C3 into AC voltages. Output to the power system. In the present embodiment, IGBTs (Insulated Gate Bipolar Transistors) are used as the semiconductor switch elements 111, 121, and 131, which have a small saturation voltage when turned on and low power loss. These self-excited inverters II, 12, and 13 are controlled to be turned on and off by a drive signal to the gate using a control unit 82 of the information processing apparatus 8 described later, so that an operation pattern (switch pattern) is controlled.

[0028] The initial charging circuit 5 charges capacitors Cl, C2, and C3 with DC voltages Vh, Vm, and VI.

A charging transformer 51 is included, and is connected in parallel to the capacitors Cl, C2, and C3. The charging operation is performed only when the apparatus is activated. When charging is completed, the capacitor Cl, C2, C3 is electrically disconnected by a switch (not shown), and the operation of the self-excited reactive power compensator 1 is not affected at all.

[0029] Therefore, in the present embodiment, the phase measuring unit 6 for measuring the phase angle of the system voltage V,

P

Capacitor voltage measurement unit 7 for measuring capacitor voltage Vh, Vm, VI, system voltage V

P

The system voltage measurement unit 9 for measuring the crest value of the output voltage V and the information processing device 8 for adjusting the crest value and the phase of the output voltage V based on the measurement data from the system voltage measurement unit 9 should be provided.

SVC

is doing.

[0030] The phase measurement unit 6 measures the phase angle of the system voltage V and displays the measurement result.

P

The phase angle measurement data is output to the information processing device 8.

[0031] The capacitor voltage measuring unit 7 is for measuring the voltages Vh, Vm, VI charged in the capacitors Cl, C2, and C3, and outputs the voltage measurement data to the information processing device 8. It is.

[0032] The system voltage measurement unit 9 measures the crest value of the system voltage V and indicates the measurement result.

P

The voltage measurement data is output to the information processing device 8.

As shown in FIG. 2, the information processing apparatus 8 is a general-purpose or dedicated computer having a CPU 801, a memory 802, an input / output interface 803, etc., and is stored in a predetermined area of the memory 802. By cooperating the CPU 801, peripheral devices, etc. according to the specified program, the functions as the reception unit 81, the control unit 82, etc. are generated as shown in FIG. Devour.

The receiving unit 81 receives the measurement data from each measurement unit described above, and outputs it to the control unit 82.

The control unit 82 is configured to output the output voltage V based on the measurement data received by the reception unit 81.

SVC

And the phase difference between the system voltage V and the power system every cycle of the AC frequency.

P

This adjustment is made so that the average sum of energy input and output between the capacitor and the capacitors Cl, C2, and C3 is zero. In other words, each capacitor voltage Vh, Vm, VI is monitored and active power is input / output to / from the power system according to the difference between the charging energy and the initial charging energy, and the capacitors Cl, C2, C3 Control is performed so that the total charge energy E is a constant value.

Specifically, as shown in the block diagram of FIG. 4, the p SVC phase difference Φ of the output voltage V with respect to the system voltage V is determined, and the target voltage V of the output voltage V of the self-excited reactive power compensator 1 is determined.

SVC ref Controls inverters II, 12, and 13 using the following formula.

[0037] [Equation 1]

Where V is the peak value of the AC voltage of AC power supply 2, X is the impedance of the power system, X

P P s is impedance of self-excited reactive power compensator 1 rear tutor 10 Q is general SV

VC

As with C, it is calculated by the information processing device 8 according to the purpose of controlling the interconnection point voltage V and improving the power factor.

[0038] In the block diagram of Fig. 4, the constant K is used to correct the error between the sum E and the reference value E.

1 c ref

This constant is used to adjust the time required. The constant K suppresses the temporal vibration of the sum E.

2 c

It is a constant to do. The constant K is used to correct the error between the sum E and the reference value E.

3 c ref is regarded as positive power, and is converted into a phase difference φ between the system voltage V and the output voltage V for exchange between the self-excited reactive illumination compensator 1 and the power system. Constant p SVC

The

[0039] Here, the sum E of energy stored in all capacitors and the reference value E are

c ref [0040] [Equation 2]

E c knee (, 'Vh ² + -CVm ² + U ²

[Equation 3]

E _ref C ₃ .VI, ²

Respectively. Note that Cl is the capacitance of the capacitor CI, C2 is the capacitance of the capacitor C2, and C3 is the capacitance of the capacitor C3.

[0042] Further, when the control unit 82 outputs the voltage V, the respective capacitors Cl, C

SVC

2. The operation pattern for each of the self-excited inverters II, 12 and 13 is determined so that the voltage ratio between C3 and C3 is as close as possible to the predetermined value (Vh: Vm: Vl = 4: 2: 1). is there.

[0043] Specific operation patterns of self-excited inverters II, 12, and 13 will be described below.

[0044] Capacitors Cl, C2, and C3 have Vh = 2 XVm = 2 X 2 XV1 in the initial charge state.

0 0 0 Since the related voltages Vh, Vm, VI are charged, the operation patterns of inverters II, 12, 13

0 0 0

Depending on the selection method, 7 levels of voltage V can be output. At this time

SVC

The minimum output level is level 1. When outputting the same level of voltage V

SVC

Multiple operation patterns of inverters II, 12, and 13 may be selectable.

[0045] The operation patterns of the self-excited inverters II, 12, and 13 are normalized values of the initial charging voltages Vh, Vm, and VI of the capacitors Cl, C2, and C3 (Vh, 2Vm, 4V1) and the charging voltage at the output. The

0 0 0 0 0 0

Compared with normalized values (Vh, 2Vm, 4V1), it is determined to preferentially correct in the order of capacitors C1, C2, and C3 where the values deviate.

In other words, as shown in the table of FIG. 5, depending on the relationship between the state power of the capacitors Cl, C2, and C3, the voltage Vh, Vm, and VI of the capacitors, and the voltage conditions of the capacitors, it depends on the output level. The operation pattern, that is, discharging and charging is determined. In the table of Fig. 5, when it is “1”, the capacitor Cl, C2, C3 is discharged, and when it is “−1”, the capacitor Cl, C2, C3 is charged. However, when the output current I and the output voltage are opposite in polarity, they are charged / discharged. The electrical relationship is reversed. In this case, the direction of the inequality sign in the capacitor voltage condition is also reversed. Further, FIG. 6 shows the operation timing of each power supply circuit 41, 42, 43 that causes the power supply circuits 41, 42, 43 to perform a predetermined output operation and outputs the output voltage V and output current I of the device 1.

SVC SVC

Is showing.

Next, as a specific example, FIG. 7 shows an example in which the voltage V of level 1 is output. The level

SVC

The combination of capacitor voltages Vh, Vm, and VI to output 1 voltage V

SVC

[0048] (1) When discharging only the capacitor voltage VI:

[0049] (2) When discharging the capacitor voltage Vm and charging the capacitor voltage VI,

[0050] (3) When discharging capacitor voltage Vh and charging capacitor voltage Vm and capacitor voltage VI,

[0051] There are three ways. This makes it possible to charge and discharge the capacitor voltages Vm and VI, depending on how the output pattern is selected. In other words, the capacitor voltages Vh, Vm, VI of the power supply circuits 41, 42, 43 can be adjusted by selecting the operation pattern of the inverters II, 12, 13 for each output level.

Next, the operation of the self-excited reactive power compensator 1 according to the present embodiment configured as described above will be described below.

[0053] First, when the self-excited reactive power compensator 1 is activated, the system voltage measuring unit 9

P

The phase measurement unit 6 measures the phase of the system voltage V and measures the capacitor voltage.

P

The fixed unit 7 measures the capacitor voltages Vh, Vm, and VI, and outputs the measured data to the information processing device 8, respectively. Then, the information processing apparatus 8 receives the measurement data, and the control unit 82 starts to supply reactive power V to the power system.

SVC

[0054] Thereafter, when the capacitor voltages Vh, Vm, and VI change, the control unit 82 is shown in the control block diagram of FIG. 4 based on the phase measurement data and the capacitor voltage measurement data. The phase of the output voltage V is adjusted according to the control method used. This allows the capacitor

SVC

The total charge energy E of Cl, C2, and C3 is adjusted.

[0055] Further, the control unit 82 determines, based on the capacitor voltage measurement data, which of the capacitor voltage conditions in FIG. 5 the capacitor voltages Vh, Vm, V1 apply, and the semiconductor switch elements of the inverters II, 12, 13 Select the operation pattern of 111, 121, 131 and drive with inverter The inverter drive signal is output to circuit 11. As a result, the inverters II, 12, and 13 perform the desired operation to output the output voltage V and the voltage ratio of the capacitor voltages Vh, Vm, and VI.

SVC

Is corrected to the relationship of Vh: Vm: VI = 4: 2: 1.

Next, the result of the operation simulation of the self-excited reactive power compensator 1 under the specific condition setting shown in FIG. 10 is shown. In this simulation, it is assumed that a voltage drop of 20% occurred at time 2 [S] to 4 [S] after startup of device 1. Here, [%] of the voltage of the DC power supply used so far is read as [V]. For comparison, Fig. 8 shows the operation simulation results when only the conventional 3-pulse (carrier frequency 180Hz) PWM inverter is used, and the operation simulation results when only the 16-pulse (carrier frequency 960Hz) PWM inverter is used. Figure 9 shows.

As shown in FIG. 11, inverters II, 12, and 13 are PWM-controlled by control unit 82, and output voltage V is adjusted. At this time, the number of switches of inverters II, 12, 13

SVC

Capacitor voltage Vh is 1 pulse, Capacitor voltage Vm is 3 pulses, Capacitor voltage VI is 7 pulses, and the equivalent number of switches is 2.4 pulses (= (60 [V] X 1 pulse + 3 0 [V ] X 3 pulses + 15 [V] X 7 pulses) Z105 [V]), which can be confirmed to be 3 pulse inverter or less. In addition, compared to the results in Figs. 8 and 9, the output voltage V

SVC

It can be seen that there are far fewer harmonic components.

[0058] In FIG. 11, for example, when output level 3 (45 [V]) is output (part A), confirm that capacitors Cl and C3 are charged and capacitor C2 is discharged. Is possible.

[0059] The transition of the phase difference shown in FIG. 12 is the time when the system voltage V is normal (1 to 2 [S], 4 to 5 [S]).

P

It is stable at about 0.23 [rad]. Furthermore, it can be seen that it stabilizes to about 0.5 [rad] during the voltage drop from time 2 [S] to 4 [S].

[0060] Figure 13 shows the results of the successful adjustment of the capacitor voltages Vh, Vm, and VI. Capacitor voltages Vh, Vm, VI even though the system voltage V has abrupt fluctuations

P

It can be seen that is stable at almost 60 [V], 30 [V], 15 [V] over the entire time.

[0061] Although the system voltage V force is reduced to ¾0 [V], the connection point voltage V «90 [V]

Voltage stability effect as the original self-excited reactive power compensator 1 Check it.

[0062] In the result shown in FIG. 14, the present apparatus 1 supplies a delayed current i to the power system,

SVC

It can be seen that the load power factor (cos Z (V, i)) seen from the grid side can be improved satisfactorily.

P P

[0063] According to the self-excited reactive power compensator 1 configured as described above, a plurality of power supply circuits 41, 42, and 43 having different output voltages Vh, Vm, and VI are connected in series. The magnitude of the output voltage can be changed, and the number of equivalent switches of inverters II, 12, and 13 can be reduced, so that high performance and high efficiency can be realized.

[0064] In other words, a 15-level inverter with a maximum output voltage of 105V can be configured in total, and the total distortion of the output voltage V of this 15-level inverter is about 4% without using a harmonic filter.

SVC

Compared with a 16-pulse inverter (inverter with a carrier wave of about 1 kHz), it is much higher performance. Furthermore, the equivalent number of switches is 2.4 and 3 pulse inverters or less. For example, when 1kHz PWM control is performed with a single inverter of 105 [V], that is, compared with a 16-pulse inverter, the switching loss is 15%. It only takes about. As described above, according to the present embodiment, both high performance and high efficiency can be achieved.

Further, the control unit 82 controls the phase difference between the output voltage V and the system voltage V.

SVC p

, Adjust the average sum of energy input and output between the power system and the capacitors Cl, C2, and C3 every cycle of the AC frequency to output a voltage V

SVC

The self-excited inverters II, 12, so that the voltage ratio between the respective capacitors Cl, C2, C3 is as close as possible to a predetermined value (Vh: Vm: Vl = 4: 2: 1). Since the operation pattern is determined every thirteen, the effect of the present embodiment can be made more remarkable.

[0066] <Second Embodiment>

Next, a second embodiment of the self-excited reactive power compensator 1 according to the present invention will be described with reference to the drawings.

[0068] The self-excited reactive power compensator 1 according to the present embodiment differs from the first embodiment in the function of the control unit 82. That is, as shown in FIG. 15, the control unit 82 of the present embodiment uses the sum of the voltages Vh, Vm, and VI (Vh + Vm + Vl) of the capacitors Cl, C2, and C3 as the peak value of the output voltage V.

SVC

The ratio of the capacitor voltages Vh, Vm, VI is as follows as Vh: Vm: In order to maintain the relationship of Vl = 4: 2: 1, the operation of each of the self-excited inverters II, 12 and 13 is determined so that a voltage of 15 levels can always be output regardless of the peak value of the output voltage V.

SVC

It also has the ability.

[0069] FIG. 15 shows, for example, the output voltage V when the output voltage changes from 105 [V] to 90 [V], and the operation timing of each of the power supply circuits 41, 42, and 43 at that time. Have

SVC

The At this time, the control unit 82 of the present embodiment sets the voltages Vh, Vm, and VI force S of the capacitors Cl, C2, and C3 to 51.44 [V], 25.72 [V], and 12.86 [V], respectively. Control self-excited innotators II, 12, and 13 so that

Further, the control unit 82 of the present embodiment limits the peak value of the output voltage V based on the withstand voltage performance and current capacity of the components of the device 1, and outputs 15 levels of voltage as described above.

SVC

It is something that can help you.

Specifically, as shown in the block diagram of FIG. 16, the output voltage V

S

The provisional value | Vz | The calculated provisional value | Vz | is passed through the second limiter section (T).

VC

SVC ref ref

If the output voltage exceeds the withstand voltage performance of device l, or if the output current determined by the provisional value | Vz | exceeds the current capacity of device 1, the predetermined peak value | v I that satisfies them is determined. Ret.

Here, | V I in FIG. 16 is a target value of the peak value of interconnection point voltage V, and is a constant value in the time domain. V is the instantaneous value of the connection point voltage in the time domain, E is the instantaneous value in the time domain of the sum of the charging energy of the capacitors Cl, C2, and C3, and the RMS block converts the instantaneous value to an effective value. . The first limiter section (S) is provided so that the output of the previous integration section does not diverge when an error of | V I and IV I occurs due to the second limiter section (T).

[0073] On the other hand, the target value of Vh + Vm + VI | V | is the peak value | V c re

I is determined via the third limiter unit (U).

f

[0074] Next, the difference between the charging energy E of the capacitors Cl, C2, and C3 and the target value E is in a steady state. C ref The active power Ps input / output to / from the capacitors Cl, C2, and C3 is determined so as to be zero. The active power Ps is converted to the self-excited reactive power compensator 1 and the power by conversion using the constant K.

Four

The system voltage V to be exchanged with the power system and the t SVC ref phase difference Φ of the target voltage V of the output voltage V are determined. Then, the target voltage VV of the output voltage of the self-excited reactive power compensator 1 is calculated by the following formula to control the inverters II, 12, and 13.

ref

[0075] [Equation 4]

[0076] Here, ω is the fundamental frequency of the power system.

Next, FIG. 18 shows the result of the operation simulation of the self-excited reactive power compensator 1 under the specific condition setting shown in FIG. In this simulation, it is assumed that a voltage drop of 30% occurred at time 2 [S] to 4 [S] after startup of device 1. The capacitances of capacitors Cl, C2, and C3 are 100 [mF], 200 [mF], and 400 [mF], respectively.

Here, the second limiter section (T) in FIG. 16 determines the output voltage range based on the withstand voltage performance and current capacity of the components of the apparatus 1, and the maximum limiter value is min ( IVI + 50 [V] ゝ 140 [V]), that is, the peak value of the grid voltage IVI + 50 [V] and 140 [V], which is the smaller value, and the minimum limiter value is the peak value of the grid voltage IVI — 50 [V]. The third limiter part (U) is determined based on the withstand voltage performance of the components of the device 1, such as capacitors Cl, C2, and C3. Its maximum limiter value is 120 [V], and the minimum limiter value Is 0 [V]. The first limiter (S) has a maximum limiter value of 40 [V] and a minimum limiter value of 1 [V].

[0079] At this time, the voltage V that the self-excited reactive power compensator 1 should output to the power system is 140 [

SVC

V], and as shown in FIG. 18, the voltage Vh of the capacitor C1 is increased from 56 [V] to 68 [V], and the voltage Vm of the capacitor C21 is changed from 28 [V] to 34 [V]. The voltage VI of capacitor C3 has risen from 14 [V] to 17 [V], and the total value of these is 119 [V]. As a result, the system voltage V drops by 30% from 100 [V] to 70 [V].

P

Nevertheless, the interconnection voltage V can be maintained at about 90 [V], confirming the voltage stability effect of the original self-excited reactive power compensator. [0080] According to the self-excited reactive power compensator 1 configured as described above, the desired output voltage V

SVC

Accordingly, the capacitor voltages Vh, Vm, VI can be increased or decreased while maintaining the 4: 2: 1 relationship, and 15 levels of high-accuracy voltage output is always possible regardless of the output voltage V.

SVC

Therefore, even during low-voltage output, high-accuracy voltage output is possible without reducing the number of voltage output levels. At this time, the maximum value of the output voltage V is calculated in consideration of the withstand voltage performance and current capacity of the components of the device 1.

SVC

A certain device operation can be ensured.

Note that the present invention is not limited to the above-described embodiment.

[0082] For example, in the embodiment, three power supply circuits are connected in series. However, the present invention is not limited to this, and two power supply circuits may be connected in series, or four or more power supply circuits may be connected in series! / ヽ.

[0083] Further, a force that makes the voltage ratio of the capacitor voltage a power of 2 may be used.

[0084] In the above-described embodiment, only one capacitor is used for one power supply circuit and the output voltage is different. A plurality of capacitors are connected in series to one power supply circuit to output different output voltages. OK!

Furthermore, in the above-described embodiment, the capacitor is used as the energy storage unit. However, the present invention is not limited to this. For example, a battery may be used.

In addition, although IGBT is used as the semiconductor switch element, it is not limited to this, and a self-extinguishing semiconductor switch element such as a gate turn-off thyristor may be used.

[0087] In addition, a switch in which those switch elements are connected in series may be used as one switch.

[0088] In the above embodiment, normalization is corrected so as to correct the most dissimilarity, but in addition to this, the initial charge voltage is compared with the actual voltage without normalization and the You may make it correct what has deviated.

In view of the above, in the above embodiment, when the energy of the entire capacitor is adjusted, only the capacitor voltage that is charged with the largest voltage is adjusted in consideration of the sum of the capacitor voltages. May be adjusted in consideration of the two capacitor voltages. It is okay to make adjustments in consideration.

[0090] The target voltage V in Equation 1 is measured by measuring the peak value and phase of the voltage V at the grid connection point of the device.

ref t

It can also be calculated using the impedance X of reactor 10 of device 1.

svc

[0091] [Equation 5] ef (0 = Y _t + Q / X _svc ) x sin (+)

[0092] The total DC voltage is not necessarily 105 [%] (= 60 [%] + 30 [%] + 15 [%]). Can also be designed.

[0093] The present invention is not limited to single-phase applications.

If it is treated as a normal / reverse phase component in a three-phase AC, it can also be applied to a three-AC system.

In addition, in the second embodiment, when the output voltage is calculated, the first limiter unit, the first limiter unit,

Although the 2 limiter unit and the 3rd limiter unit are provided to limit the maximum value of the output voltage, the output voltage may be calculated without providing these limiter units.

[0095] Needless to say, various modifications can be made without departing from the spirit of the present invention.

Industrial applicability

[0096] As described above, the self-excited reactive power compensator according to the present invention is configured by connecting a plurality of power supply circuits having different output voltages in series, and the magnitude of the output voltage is changed by the combination thereof. It is possible to reduce the number of equivalent switches of the entire inverter, and thus high performance and high efficiency can be realized.

Claims

The scope of the claims

[1] A self-excited reactive power compensator that is connected in parallel to a power system and supplies reactive power to the power system to adjust the voltage of the power system and improve the power factor of the load. A plurality of power supply circuits connected in series and connected to the DC power supply, and a self-excited inverter that converts the voltage of the DC power supply into an AC voltage and outputs the AC voltage to the power system. A self-excited reactive power compensator characterized in that the voltages of the respective DC power supplies are different from each other!

2. The self-excited reactive power compensator according to claim 1, wherein voltage ratios of the respective DC power supplies are in a power-of-two relationship.

3. The self-excited reactive power compensator according to claim 1 or 2, wherein the DC power supply is a capacitor.

[4] The phase difference between the output voltage and the system voltage is controlled to adjust the average sum of energy input and output between the power system and each DC power supply to be substantially zero. The self-excited reactive power compensation device according to claim 1, 2 or 3, further comprising a control unit.

[5] When the control unit outputs a desired output voltage, the operation of each self-excited inverter is defined so that the voltage ratio between the DC power sources is as close as possible to a predetermined value. 5. The self-excited reactive power compensator according to claim 4, wherein

[6] The control unit may perform adjustment so that an average of the amount of charge passing for each DC power supply becomes zero every 1Z4 cycle, every 1Z2 cycle, or every integer cycle of an AC frequency. 5. The self-excited reactive power compensator according to 5.

[7] The control unit restricts the upper and lower limits of the output voltage for outputting the reactive power based on the withstand voltage performance and current capacity of the component, and within the range, the respective DC 7. The self-excited reactive power compensator according to claim 5 or 6, wherein an operation for each of the self-excited inverters is determined so that a sum of the voltages of the power supplies becomes as close as possible to the output voltage. .

[8] A self-excited reactive power compensator that is connected in parallel to a power system and supplies the reactive power to the power system, thereby adjusting the voltage of the power system and improving the power factor of the load. A power supply circuit comprising a capacitor and a self-excited inverter that is connected to the capacitor and converts the voltage of the capacitor into an AC voltage and outputs it to the power system is connected in series, and the output voltage And a control unit that controls the phase difference between the power system and the system voltage, and adjusts the sum of energy input and output between the power system and the respective capacitors,

The voltage of each capacitor is approximately 4: 2: 1.

The control unit limits the upper and lower limits of the output voltage for outputting the reactive power based on the withstand voltage performance and current capacity of the component parts, and in that range, the sum of the capacitor voltages is added to the output voltage. And the operation of each self-excited inverter is defined so that the voltage ratio of the capacitors is approximately 4: 2: 1. Self-excited reactive power compensator.