JP4741179B2 - Control method and apparatus for uninterruptible power supply with power storage function - Google Patents

Description

  The present invention relates to an uninterruptible power supply, and more particularly to a control method and an apparatus for an uninterruptible power supply with a power storage function using a secondary battery for power storage.

An uninterruptible power supply device configured by connecting a storage battery to a DC circuit between a converter and an inverter is widely used in various fields, but there is an additional function also used for power storage. This system stores power at times when there is little power demand, such as at night or on holidays, and discharges it at the time of a power failure.
As a storage battery for power storage, a secondary battery represented by a sodium-sulfur battery mainly for power storage (hereinafter referred to as a secondary battery for power storage) is used. Because it dislikes overcharge, it cannot be used in a floating charge state like a conventional lead battery.
That is, the lead battery in the state of the final balance the charge current and the self-discharge current can be maintained constant the voltage across the battery due to the self-discharge current of the battery itself, it will not be charged any more .

On the other hand, since the secondary battery for power storage does not have a self-discharge current, it is overcharged by continuing to flow even with a small charge current.
Therefore, when changing the lead battery to a secondary battery for power storage, in order to prevent overcharge due to floating charge, an overcharge prevention is provided between the DC circuit of the power converter and the secondary battery for power storage. A switch circuit must be provided and controlled so that unnecessary charging current does not flow after the battery is fully charged.

FIG. 10 shows a configuration diagram of the uninterruptible power supply, where CV is a converter made of IGBT or the like, IV is an inverter made of IGBT or the like, and its DC circuit is connected to a secondary battery for power storage via a switch circuit SW. NAS is connected. BC is a bypass circuit provided so as to bypass the power conversion device including the converter CV and the inverter IV.

In the uninterruptible power supply, when a power failure occurs on the grid side when power is supplied to the load from the AC power supply on the grid side through the bypass circuit BC, converter CV, or inverter IV, the secondary battery NAS for power storage is installed. Power is supplied to the load via an inverter as a power source.
At this time, since a discharge from the battery is required immediately at the time of a power failure on the system side, the overcharge prevention switch circuit SW needs to be configured so as to block only the charging current and not the discharging current. A diode D is provided in parallel with the overcharge prevention switch PS to form a discharge circuit.

In addition, as an uninterruptible power supply device with a power storage function, the thing like patent document 1 is well-known.
JP 2000-278866 A

When an electric motor is connected as a load in the uninterruptible power supply as shown in FIG. 10, it is conceivable that the regenerative electric power when the motor decelerates flows back to the secondary battery NAS for power storage through the inverter IV.
In the conventional uninterruptible power supply, the converter CV controls the rectified power from the system at a constant voltage based on the DC side voltage, so that when regenerative power is generated, this power can be reversed to the system side. did it.

However, in an uninterruptible power supply with a power storage function, it is necessary to charge and discharge the battery based on a time schedule, such as charging at night and discharging in the daytime. To that end, the converter is charged and discharged. The operation is performed with a constant current control capable of arbitrarily controlling the electric power.

When a secondary battery for power storage is connected to the switch circuit SW as shown in FIG. 10, there is no place for regenerative power from the inverter when the converter is being charged, resulting in overvoltage. This makes it impossible to continue operating the inverter.
As a means for avoiding this problem, it can be considered that the regenerative power from the inverter is absorbed by the secondary battery for power storage NAS. For this purpose, a semiconductor switch is used in place of the mechanical switch, and it is necessary to allow the charging current to pass instantaneously when regenerative power is generated, which has a problem that it is more expensive than the mechanical switch.

In the above-mentioned patent document, after the battery charging is completed, the passing power of the converter is made to coincide with the inverter load power, or the current flowing through the secondary battery is controlled to be a slight difference so that the current flowing through the secondary battery is zero or very small. There is no disclosure of the idea of preventing overcharging while maintaining a stable discharge state.

The present invention has been made in view of the above points, and the object of the present invention is to prevent the overcharge of the secondary battery for power storage by omitting the switch circuit, and to supply the regenerative power to the secondary battery for power storage. It is to provide a method and apparatus for absorbing.

A first aspect of the present invention is an uninterruptible power supply that connects a secondary battery for power storage to a DC circuit between a converter and an inverter, and charges and discharges the secondary battery for power storage while controlling the converter.
After completion of charging and discharging of the secondary battery for power storage, the power passing through the converter and the load power of the inverter are controlled so that the converter passing power ≦ the inverter load power. The flowing charge current and the discharge current are maintained in an error state corresponding to the power control performance of the converter.

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A second aspect of the present invention is an uninterruptible power supply apparatus in which a secondary battery for power storage is connected to a DC circuit between the converter CV and the inverter IV, and the secondary battery for power storage is charged and discharged while controlling the converter CV .
And the power value of the secondary battery electric power storage as determined by the product of the DC voltage and power storage for a secondary battery current detected converter CV, the inverter from the product of the detected current flowing through the DC voltage and an inverter DC circuit of the converter A conversion efficiency calculation unit 1 that calculates the DC power value of IV and calculates the AC / DC and orthogonal conversion efficiency in the converter CV from each of the determined power values;
The charging completion signal of the power storage for a secondary battery, any secondary battery is switched to one for power storage and charge completion time limit power preset rated charging power setting value of the power storage for a secondary battery A maximum charge calculation unit 2 for the maximum charge power of
Wherein the discharge completion signal of the secondary battery electric power storage, the rated discharge power set value previously set is discharged upon completion limits power and either a power storage for a secondary battery by the switching of the power secondary battery for storage A maximum discharge calculation unit 3 for the maximum discharge power of
A charge / discharge direction is selected by comparing the current battery power of the secondary battery for power storage , the maximum charge power value, and the maximum discharge power value, and the maximum charge power value and the maximum discharge power are selected based on the comparison signal. Is set as the upper limit value of the next command battery power value, and when the next command battery power value is not equal to the reference power, a minute charge / discharge correction signal is output as 0, and the next command battery power value Command battery power calculation unit 5 for outputting an arbitrary minute charge / discharge correction signal set when is equal to the reference power,
From the output signal of this calculation unit and the DC power value of the inverter IV, the converter CV
When the target value is in the discharge direction, the orthogonal conversion efficiency signal is multiplied to obtain a converter discharge command at the time of orthogonal conversion. When the target value is in the charge direction, the AC power is calculated. Converter charge / discharge command calculation unit 6 which converts the converter efficiency into a converter charge command during AC / DC conversion by dividing by the conversion efficiency signal
It is characterized by having.

The of the present invention 3, the DC power target value of the converter CV, inverter power value, and an error calculation section 4 for obtaining the error component that is dependent on the power control accuracy is provided for converter CV from the battery power value, the arithmetic unit 4 Is output to the converter charge / discharge command calculation unit 6 and added to the charge / discharge command calculation signal of the converter CV .

According to a fourth aspect of the present invention, the error x in the error calculator 4 is set in a range of 0 <x <1.0, and has a predetermined range of upper and lower limits based on the rated ratio of the converter CV. It is characterized by that.

In the fifth aspect of the present invention, the DC power target value of the converter CV is obtained by subtracting the inverter power value from the next command battery power value obtained by the command battery power calculation unit, and subtracting the minute charge / discharge correction signal from this subtraction value. This is characterized by the addition.

According to a sixth aspect of the present invention, the charge / discharge command value of the converter is any one of a value obtained by multiplying a converter DC power target value by the orthogonal conversion efficiency signal and a value obtained by dividing the converter DC power target value by the AC / DC conversion efficiency signal. It is characterized by being.

A seventh aspect of the present invention is characterized in that the minute charge / discharge correction signal is switched by a comparison signal between a converter DC power target value and the reference power. The eighth aspect of the present invention is characterized in that the error signal is added to the converter DC power target value.

As described above, according to the present invention, it is possible to prevent overcharging of the secondary battery for power storage only by control of the converter without using a switch circuit between the DC circuit of the converter and the secondary battery for power storage. It is something that can be done. Further, by adding the orthogonal and AC / DC conversion efficiency signals to the control signal of the converter, there is an effect that the adverse effect of the power receiving point at the time of regeneration or the like can be prevented.

FIG. 2 is a circuit configuration diagram showing an embodiment of the present invention, in which the same or corresponding parts as those in FIG. 10 are denoted by the same reference numerals. That is, in the present invention, the switch circuit for charging / discharging the secondary battery for power storage is omitted. Therefore, the functions shown in FIGS. 1 and 3 to 9 are provided in order to realize desired control. In each figure of the control unit C, a specific circuit configuration for PWM control of the IGBT that is an element constituting the converter CV and the inverter IV is omitted.

FIG. 1 is a block diagram of the control unit C.
Reference numeral 1 denotes a conversion efficiency calculation unit. The detected voltage, current, inverter DC current, and converter AC active power of the converter DC unit are input to the calculation unit to calculate the conversion efficiency, and the output is received by the converter CV. When the power is returned to the side, it is used as a calculation signal for not adversely affecting the power at the receiving point.

2 is a maximum charge calculation unit. Normally, the set rated charge power is the maximum battery charge value, but when charging is completed, the limit value at the completion of charging such as 0 kW becomes the maximum value, and its output is the command battery power calculation unit 5 Is output. 3 is a maximum discharge calculation unit. Similarly to the maximum charge calculation unit 2, the calculation unit 3 normally has a set rated discharge power that is the maximum battery discharge value. However, when the battery discharge is completed, a limit value at the completion of discharge such as 0 kW is obtained. Becomes the maximum value, and the output is output to the command battery power calculation unit 5. The command battery power calculation unit 5 obtains the next charge / discharge value and the minute charge / discharge correction value based on the maximum charge value, the maximum discharge value, and the battery power value. The battery power value is the current command battery power value, and the set battery power is used.

4 is an error calculation unit, and the error is determined depending on the power control accuracy etc. for the converter. The calculation unit includes a calculated converter power target value, an inverter power value, and a secondary battery for power storage. The power value is input, and the error at the next calculation cycle is calculated and output to the converter (PCS) charge / discharge command calculation unit 6. Converter charge / discharge command calculation unit 6 calculates a command value for converter CV based on signals input from AC / DC conversion efficiency calculation unit 1, command battery power calculation unit 5, error calculation unit 4, and the like.

FIG. 3 shows a waveform example of the converter charge / discharge command calculated from the battery charge / discharge pattern and the inverter load fluctuation. The horizontal axis indicates time. For example, when the setting pattern set for battery charge / discharge power such as discharge during the daytime and charge during the nighttime is A, the inverter load as shown by the line B is assumed. The converter charge / discharge command calculation unit 6 is controlled to output a command value such as line C to the converter CV.

In the present invention, when the setting pattern indicated by the line A is 0, that is, the command value indicated by the line C is output between times t _{5 and} t ₇ , the current flowing through the secondary battery for power storage is It is controlled to charge / discharge zero or slightly.

This will be specifically described below.
FIG. 4 shows a configuration diagram of the conversion efficiency calculation unit 1, and 11 is a battery power calculation unit made up of a multiplier, which detects the detected DC voltage V _{1 of the} converter and the secondary battery current I ₂ for power storage . Battery power is obtained by multiplying. Reference numeral 12 denotes an inverter power calculator composed of a multiplier, which obtains inverter power (UPS power) by multiplying the DC voltage V ₁ and the DC current I ₁ of the inverter IV . The battery power value obtained by the battery power computing unit 11 and the inverter power value obtained by the inverter power computing unit 12 are output to the subtractor 13, and the subtracter 13 subtracts “battery power- inverter power”. The result is output as converter DC power (PCS DC power) .

Reference numeral 14 denotes an orthogonal transformation efficiency calculator composed of a divider, which calculates the converter AC active power (PCS AC active power) and the converter DC power obtained from the detected AC side voltage and current v ₁ , i _1. Are used to divide “PCS AC active power ÷ PCS DC power” to calculate an orthogonal transformation efficiency signal. Reference numeral 15 denotes an AC / DC conversion efficiency calculator composed of a divider, and the calculator 15 performs a division calculation of “PCS DC power ÷ PCS AC active power” to calculate an AC / DC conversion efficiency signal.

In this way, the conversion efficiency calculation unit 1 converts the signal into an orthogonal or AC / DC conversion efficiency signal, constantly monitors the power at the power receiving point, and outputs the signal to the converter charge / discharge command calculation unit 6 so that the calculation unit 6 receives the power. It is used as a control signal for the converter CV so as not to adversely affect the point.

FIG. 5 shows a configuration diagram of the maximum charge calculation unit 2.
In the maximum charge calculation unit 2, either the set rated charge power or 0 kW is set as the maximum charge value of the battery. For this purpose, a switcher 20 is provided. As the switching signal, an output signal of the storage unit 21 that is set by a battery charging completion signal and reset at the time of battery discharging operation is used. The fact that the maximum charge value of the maximum charge calculation unit 2 is selected as 0 kW means that when a battery charge completion signal issued from a battery control unit (not shown) is output, a further charge current is supplied to the secondary battery for power storage. It is for restricting so that it does not flow.

FIG. 6 shows a configuration diagram of the maximum discharge calculation unit 3.
The maximum discharge calculation unit 3 uses either the set rated discharge power or 0 kW as the maximum discharge value of the battery. For this purpose, a switch 30 is provided. As the switching signal, an output signal of the storage unit 31 that is set by a battery discharge completion signal and reset at the time of battery charging operation is used. When the maximum discharge value is switched to 0 kW, the secondary battery for power storage is in a discharge complete state and is restricted from being discharged any further.

Figure 7 is a block diagram of an error calculation section 4, 41 and 42 in the first and second subtractors, the first subtracter 41, the converter DC power obtained in the converter charge and discharge command computing unit 6 to be described later The target value and the inverter power value obtained by the conversion efficiency calculation unit 1 are respectively introduced and the two are subtracted. In the second subtractor 42, the result value and the battery power value are subtracted and output to the multiplier 43. The multiplier 43 multiplies by an arbitrary constant, for example, 0.5, and the adder 44 Is output. The adder 44 performs addition with the previously obtained error and outputs the result to the range setting unit 45. The constant is effective in the range of 0 <x <1.0, and is appropriately set according to the degree of error correction.

The range setting unit 45 is for setting an upper limit and a lower limit of the error. The range depends on the power control accuracy and measurement accuracy of the converter and the battery characteristics, but about ± 10% or less of the converter rating (PCS rating ). Here, the range of ± 2% with respect to the rating of the converter is set so that the signal input from the adder 44 does not deviate from this range and is output to the adder 44 as the next error signal. And output to the converter charge / discharge command calculation unit 6.
The error calculation unit 4 is not necessarily required if the power control accuracy of the converter CV is good.

FIG. 8 shows a configuration diagram of the command value calculation unit 5.
In the figure, reference numeral 51 denotes a comparator, which compares the current required battery power value (battery power value) with 0 kW. This comparison is a polarity comparison of whether the battery power value is positive or negative. When the polarity of the required battery power value is negative, that is, when the charging mode is entered, an output is generated and the switch 54 is turned on. The minimum selection unit 52 is switched to the maximum selection unit 53 side.
The minimum selection unit 52 inputs the battery power value and the maximum battery discharge signal of FIG. 6 and selectively outputs the smaller one. Further, the maximum selector 53 receives the battery power value and the maximum battery charge signal of FIG. 5 and selectively outputs the larger one. That is, since the charging mode is expressed by a negative sign, the largest value is used as the limit of the maximum value of the charging power.

One of the outputs switched by the switch 54 becomes the upper limit value of the next command battery power value and is output to the converter charge / discharge command calculation unit 6. 55 is a small charge / discharge correction value calculation unit, and this calculation unit includes a comparator 56, switches 57 and 58, and a storage unit 59.
The switching device 58 performs switching, for example, by using + 2% of the converter rating as a minute discharge signal and −2% as a minute charge signal, and this switching is switched by the output signal of the storage unit 59. Therefore, the comparison signal A (next command battery power) of the comparator 56 is equal to or substantially equal to the result of comparison between the next command battery power value A and the reference power 0 kW. −2% <A <+2 When%, the switch 57 is switched to output the minute charge / discharge correction.
The storage unit 59 is set by a battery discharge completion signal and is reset by a battery charging operation signal. That is, when the battery discharge completion signal is input to the storage unit 59, the storage unit 59 switches the switch 58 to the -2% side in order to prevent further discharge, and the minute charge / discharge correction amount is reduced to the minute charge power. Output as correction. When the battery charging operation signal is input to the storage unit 59, the switch 58 is switched to + 2% and outputs the minute charge / discharge correction amount as the minute discharge power correction amount.

FIG. 9 shows a configuration diagram of the converter charge / discharge command calculation unit 6.
Reference numeral 61 denotes a subtracter, which subtracts the current inverter power value calculated in FIG. 4 from the next command battery power value obtained by the command battery power calculation unit 5 and outputs the output to the adder 62. The adder 62 adds the input subtraction signal and the minute charge / discharge correction signal, and the addition value is sent to the adder 63 to be added to the error to generate a converter (PCS) DC power target value. Is done. When the error calculation unit 4 is omitted, the adder 63 is omitted, and the output of the adder 62 becomes the converter DC power target value.

Reference numeral 64 denotes a switch, which switches to either the multiplier 66 or the divider 67 and outputs the converter DC power target value. Reference numeral 65 denotes a comparator which compares the converter DC power target value with 0 kW. When the target value is 0 kW or less, that is, when the target value is negative (during charging), the comparator 64 and the switch 68 are output. Switching from the state shown in the figure to the divider 67 side.

The multiplier 66 multiplies the converter DC power target value and the efficiency calculation signal at the time of orthogonal conversion in the converter CV, and the divider 67 converts the converter DC power target value into the efficiency calculation signal at the time of AC / DC conversion in the converter CV. An operation for division is performed and switched to one by a switch 68 and used as a converter (PCS) charge / discharge command for a converter control signal.
Therefore, even if a switch circuit connected in series with the secondary battery for power storage is not provided, the control signal of the converter is such that the current flowing to the secondary battery for power storage is 0 or a slight discharge state (a little in the discharge complete state). Charge) and overcharge of the secondary battery can be prevented.

The block diagram of the control part which shows embodiment of this invention. The block diagram of an uninterruptible power supply. Converter charge / discharge command waveform diagram calculated from the setting pattern and load variation. The block diagram of a conversion efficiency calculating part. The block diagram of a maximum charge calculating part. The block diagram of the maximum discharge calculating part. The block diagram of an error calculation part. The block diagram of a command battery power calculating part. The block diagram of a converter charge / discharge command calculating part. The block diagram of the conventional uninterruptible power supply.

1 ... Conversion efficiency calculation unit 2 ... Maximum charge calculation unit
3. Maximum discharge calculation section
4 ... Error calculation unit
5 ... Command battery power calculation unit 6 ... Converter charge / discharge command calculation unit

Claims (8)

In an uninterruptible power supply that connects a secondary battery for power storage to a DC circuit between the converter and the inverter and charges and discharges the secondary battery for power storage while controlling the converter.
After completion of charging and discharging of the secondary battery for power storage, the power passing through the converter and the load power of the inverter are controlled so that the converter passing power ≦ the inverter load power. A control method for an uninterruptible power supply with a power storage function, wherein a flowing charging current and a discharging current are maintained in an error state corresponding to a power control performance of a converter. In an uninterruptible power supply that connects a secondary battery for power storage to a DC circuit between the converter CV and the inverter IV and charges and discharges the secondary battery for power storage while controlling the converter CV.
The power value of the secondary battery for power storage obtained by the product of the detected DC voltage of the converter CV and the secondary battery current for power storage, and the product of the DC voltage of the converter and the detected current flowing through the inverter DC circuit A conversion efficiency calculation unit 1 that calculates the DC power value of IV and calculates the AC / DC and orthogonal conversion efficiency in the converter CV from each of the determined power values;
Depending on the charging completion signal of the secondary battery for power storage, either the rated charging power setting value of the secondary battery for power storage or the preset limited power at the time of charging completion is switched to one, and the secondary battery for power storage A maximum charge calculation unit 2 for the maximum charge power of
Depending on the discharge completion signal of the secondary battery for power storage, either one of the secondary battery for power storage is switched by switching between a rated discharge power setting value of the secondary battery for power storage and a preset limit power at the time of discharge completion. A maximum discharge calculation unit 3 for the maximum discharge power of
A charge / discharge direction is selected by comparing the current battery power of the secondary battery for power storage, the maximum charge power value, and the maximum discharge power value, and the maximum charge power value and the maximum discharge power are selected based on the comparison signal. Is set as the upper limit value of the next command battery power value, and when the next command battery power value is not equal to the reference power, a minute charge / discharge correction signal is output as 0, and the next command battery power value Command battery power calculation unit 5 for outputting an arbitrary minute charge / discharge correction signal set when is equal to the reference power,
The target value of the DC power value of the converter CV is calculated from the output signal of the arithmetic unit and the power value of the inverter IV, and when the target value is in the discharge direction, the orthogonal conversion efficiency signal is multiplied to convert the converter at the time of orthogonal conversion A converter charge / discharge command calculation unit 6 that generates a discharge command and, when the target value is in the charging direction, divides by the AC / DC conversion efficiency signal to obtain a converter charge command at the time of AC / DC conversion.
A control device for an uninterruptible power supply with a power storage function. An error calculation unit 4 is provided for obtaining an error depending on the power control accuracy for the converter CV from the DC power target value of the converter CV, the inverter DC power value, and the battery power value, and the output of the calculation unit 4 is supplied to the converter charging unit. 3. The control device for an electric power storage uninterruptible power supply according to claim 2, wherein the control device is output to the discharge command calculation unit 6 and added to the calculation signal of the charge / discharge command of the converter CV. The error amount x in the error amount calculation unit 4 is set to a range of 0 <x <1.0, and is set to a range having a predetermined range of an upper limit and a lower limit based on a rated ratio of the converter CV. The control apparatus of the uninterruptible power supply with a power storage function of 2 or 3. The DC power target value of the converter CV is obtained by subtracting the inverter power value from the next command battery power value obtained in the command battery power calculation unit and adding the minute charge / discharge correction signal to this subtraction value. The control device for an uninterruptible power supply with a power storage function according to any one of claims 2 to 4. The charge / discharge command value of the converter is either a value obtained by multiplying a converter DC power target value by the orthogonal conversion efficiency signal, or a value obtained by dividing the converter DC power target value by the AC / DC conversion efficiency signal. A control device for an uninterruptible power supply with a power storage function according to any one of claims 3 to 5. The uninterruptible power supply with a power storage function according to any one of claims 3 to 6, wherein the minute charge / discharge correction signal is switched by a comparison signal between a converter DC power target value and the reference power. Control device. The control device for an uninterruptible power supply with a power storage function according to any one of claims 3 to 7, wherein the error signal is added to the converter DC power target value.

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