JP2001016859A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly operate each parallel multiplexed unit converter without unevenness, by selecting the unit converter in the number of operating sets determined successively from a small existing operation amount, to be operated in respective maximum converting efficiency. SOLUTION: A control circuit 4 supervises output voltage detected by an instrument transformer 5, with the output current of each inverter 1 being detected by each instrument current transformer 6, etc. Required power in each point of time set by an operating schedule data is divided by output power of maximum converting efficiency of each inverter 1, to determine the number of operating sets in each point of time of each inverter 1. Next, an individual integrating result of output power of each inverter 1 is stored as an existing operating amount of each inverter 1. The number of operating sets of the inverters 1 determined successively, starting from small this existing operating amount are selected to be operated by maximum converting efficiency. Accordingly, the number of operating sets, where generated power obtained through parallel multiplex operation in maximum converting efficiency is required power or higher in each point of time, can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for operating a plurality of inverters or inverters for power of the same capacity or a plurality of forward converters such as converters in parallel and multiplex operation.

[0002]

2. Description of the Related Art Conventionally, in power facilities such as power storage facilities, photovoltaic power generation facilities, and various battery charge / discharge test apparatuses, a static power converter converts DC power into AC power (DC / AC). ) Or conversion of AC power to DC power (forward conversion of AC / DC).

[0003] In this case, the capacity of the power conversion device differs depending on the application or the like, and it may be necessary to increase the capacity of the device by so-called expansion.

[0004] Therefore, in this type of power converter, it is desired to use standardized equipment to cope with the diversification of products having different capacities. Specifically, for example, a comparison of about several KW is required. An inverter or converter having a very small capacity is used as a unit converter, and a plurality of unit converters determined in consideration of required capacity and the like are formed by parallel multiplexing.

Further, in this type of power converter, the required AC or DC power changes with time based on the change of the demand power with the time zone.
The required power in each time zone of the day is preset as an operation schedule, and each unit converter is selectively operated at each time based on the operation schedule.

In this operation control, for example, assuming that the power to be generated in the time zone (required power) is Pref and the rated output (output power at a load factor of 100%) of each unit converter is Pr, (m− 1) The number of operating units m that satisfies the condition of Pr <Pref <mPr is determined, and the unit converter for the operating unit m is appropriately selected for operation.

[0007]

SUMMARY OF THE INVENTION In the case of the conventional device,
In order to select a unit converter that operates without consideration of the previous operation results of each unit converter, etc., in some cases, one group of unit converters is always selected and continuously operated, but another group of unit converters is continuously operated. An operation bias occurs in which the device is not selected and is not operated at all.

For example, in the case of a photovoltaic power generation system in which the unit converter is an inverter for electric power, in order to make full use of the energy generated by the solar cell, the solar power generation system is formed by multiplexing the number of inverters corresponding to the rated power generation in parallel. However, the actual solar radiation is 30 to 40 of the solar radiation at the rated power generation (full power generation) of the solar cell.
%, About 3% of each inverter
There are inverters that are operated only 0 to 40% and are always selected and kept running as described above, and inverters that are not selected and are not operated at all.

For this reason, in the conventional apparatus, each unit converter cannot be operated uniformly. As a result, the life of the entire apparatus is determined by the unit converter which is always selected and continuously operated, and its life is extended. There is a problem that cannot be solved.

Inverters such as inverters and forward converters such as converters have a rated output (load factor 100%) as shown in FIG. 3 showing general conversion efficiency characteristics of an inverter.
% Output), the conversion efficiency is at a maximum ηma when operating at an output of about 50 to 60% (load factor A%).
x, the efficiency is high both in terms of energy and economy.

However, in the case of the conventional apparatus, each selected unit converter is operated at the rated output. For example, if the power to be generated is 180% of the rated output, two unit converters are selected and It runs at 90%.

In this case, each of the three unit converters is operated at a load factor of A% (50 to 60%), and a rated output of 18 is obtained.
There is a problem that the conversion efficiency is lower than when 0% power is generated, and high-efficiency power conversion cannot be performed.

According to the present invention, the unit converters which are multiplexed in parallel are operated uniformly without unevenness to extend the life, and
An object is to enable efficient power conversion with high conversion efficiency.

[0014]

In order to solve the above-mentioned problems, a power converter according to the present invention, in the case of claim 1, converts a set required power to a power generated at a maximum conversion efficiency of each unit converter. Means for determining the number of operating unit converters by dividing by, means for storing the individual integration results of the output power of each unit converter as the already operated amount of each unit converter, Means for selecting the unit converters of the number of units determined in order and operating at the maximum conversion efficiency.

Therefore, the number of operating unit converters at each time point is determined to be the number of units at which the generated power obtained by the parallel multiplex operation at the maximum conversion efficiency becomes equal to or more than the required power at each time point.

[0016] Since the unit converters of the number of operating units selected in order from the one with the smallest operating record and the one with the smallest operation amount are operated at the maximum conversion efficiency, each unit converter is operated regardless of the required power change. It is possible to operate the device with high conversion efficiency by selecting the devices evenly without any deviation, and to efficiently generate power that satisfies the required power.

According to a second aspect of the present invention, there is provided means for storing the number of operable unit converters and the number of unavailable units due to a failure or the like. Is divided by the output power of the maximum conversion efficiency of each unit converter, and the number obtained by dividing the total number of each unit converter by the number of operable units is multiplied. Determined as the number of operating units.

Therefore, when a part of each unit converter cannot be operated due to a failure or the like, the number of units that can not be operated (the number of units that cannot be operated) is determined as the number of units operated at each time.

Therefore, even if the unit converter selected based on this determination includes an inoperable unit converter, each unit converter is evenly selected without deviation and operated with high conversion efficiency. It is possible to generate electric power to cover the required electric power.

Furthermore, in the case of claim 3, when the determined number of operating units exceeds the number of operable unit converters, the required power is obtained by multiplying the rated output power of each unit converter by the number of operable units. If the amount is equal to or less than the limit amount, a unit for operating each operable unit converter with electric power obtained by dividing required electric power by the number of operable units is provided.

Therefore, even if all the operable unit converters are operated at the maximum conversion efficiency, the generated power is insufficient. However, if all the unit converters are operated at a higher output, the required power can be satisfied. The operable unit converters are equally operated to generate electric power to cover the required electric power, and the operation is continued as much as possible to improve reliability and the like.

Further, in the case of claim 4, when the determined number of operating units exceeds the number of operable units of each unit converter, the required power is obtained by multiplying the rated output power of each unit converter by the number of operable units. If the amount exceeds the upper limit, all the units of the unit converter are stopped to generate an abnormality alarm.

Therefore, even if all the operable unit converters are operated at the rated output, the generated power is insufficient, so-called an insufficient power condition. An alarm can be issued, and reliability and the like are further improved.

In the case of claim 5, each of the unit converters comprises a power inverter having the same capacity, and the DC power supply of each inverter comprises a secondary battery or a solar battery for storing power. An applied power storage facility or solar power generation device can be provided.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows each unit converter as an inverter which is an example of an inverse converter, and INV1,
The inverters INV2,..., INVn are connected in parallel to the power system 2 by multiplexing n inverters 1 in parallel, and a common DC power supply 3 composed of a secondary battery or a solar cell for storing power is synchronized with the system power supply 2. The case of converting to electric power is shown.

The operation of each inverter 1 is controlled by software processing of a common control circuit 4 having a microcomputer configuration.

The control circuit 4 monitors the output voltage detected by the instrument transformer 5 and the output current of each inverter detected by each instrument current transformer 6, and the following (i) to (i).
(Iii) means. (I) Means for determining the number of inverters 1 to be operated at each time point by dividing the required power at each time point set by the operation schedule data to be described later by the output power of the maximum conversion efficiency of each inverter 1 (ii) Each inverter Means for storing the individual integration results of the output powers as the already-operated amounts of the respective inverters (iii) The inverters of the determined number of operated units are selected in ascending order of the already-operated amounts and each is operated at the maximum conversion efficiency. means

Also, in this embodiment, the control circuit 4 is provided with the following means (iv) in consideration of the fact that there is an inverter 1 which cannot be operated due to a failure or being inspected. (Iv) Means for storing the latest operable number of each inverter 1 and the inoperable number due to a failure or the like.

When determining the number of vehicles operated at each point in time by means of (i), the required power is
Is multiplied by the coefficient obtained by dividing the total number of inverters 1 by the number of operable units, and the number obtained by dividing the total number of inverters 1 by the number of operable units is determined as the number of operating units.

Further, the operation is continued as much as possible even when the determined number of operating vehicles exceeds the number of operable vehicles, and an alarm is generated when the number of operating vehicles is not possible.
The following means (v) and (vi) are also provided. (V) When the determined operating number exceeds the operable number of the inverters 1 and the required power is equal to or less than the upper limit obtained by multiplying the rated output power of each inverter 1 by the operable number,
Means for operating all the operable inverters 1 with an output obtained by dividing the required power by the number of operable units (vi) When the determined number of operating units exceeds the number of operable inverters 1, the required power is Means for stopping the operation of all inverters 1 and generating an abnormal alarm if the power exceeds the upper limit obtained by multiplying the rated output power by the number of operable units.

Next, a specific operation control of the control circuit 4 based on each of the above means will be described with reference to a flowchart of the operation control of the control circuit 4 in FIG.

First, as the entire operation schedule data, for example, combination data (Pi, ti) (= P ₁ , t ₁ ), (P ₂ , t ₂ ) of the total required power Pi and the time ti,
.., (Pz, tz) are controlled by the control circuit 4 by keyboard operation or the like.
Is set in advance.

It should be noted, indicates that the requested power (P _1, t ₁₎ between times t ₀ ~t ₁ (time T ₁₎ is P _1,
(P _2, t ₂₎ indicates that the required power between times t ₁ ~t ₂ (time T ₂₎ is P _2, similarly, (Pz, tz)
Means that the required power between times tZ _{-1 and} tz (time Tz) is Pz
Is shown.

[0034] When the operation control is executed to initialize the control circuit 4 and the like in step S ₀ in FIG. 2, after setting a variable i to 1, the process proceeds to step S _1, the set operation schedule data Check.

Furthermore, the number Na of normal operation Friendly of referring to the inverters 1 information such as the self-diagnosis result of each inverter 1 in step S _2, the number of operation not being remaining failure or the like Nb Check the current value of (the latest value).

Next, the required power Pi in step S ₃
, Nz (= N ₁ , N ₂ ,..., Nz).

The operation number Ni is determined by the inverter 1
Is the load factor (set value) at which is the maximum conversion efficiency, that is, FIG.
And the rated output power (set value) Pr of each of the inverters 1 and the calculated coefficient C = (Na + Nb) / Na.

[0038]

## EQU00001 ## Ni = [Pi / {(A / 100) .Pr}]. C

In the equation (1), (A / 100) ·
Pr is the output power at the maximum conversion efficiency of each inverter 1, and the coefficient C is the number N
It is a constant for determining i.

Each time Ti (= T ₁ , T ₂ ,..., T
the number of operating units Ni (= N _1, N ₂ of z), ..., Nz) is determined as shown in Table 1 below.

[0041]

[Table 1]

Next, it is determined whether or not the number of operating vehicles Ni determined in steps S ₄ and S ₅ is greater than the number of operating vehicles Na. Normally, since Ni ≦ Na, steps S ₄ and S _{5 are performed.}
Together through a negative (NO) the processing flow proceeds to step S _6.

[0043] Then, step S integrated value W ₁ of the individual power generated to date of each inverter 1 (output power) by _6, W _2, ..., Wn confirms reads out the already operating variable.

[0044] In addition, the integrated value W ₁ ~W by step S ₇
For example, n is arranged in ascending order from the smallest one to obtain a column table in ascending order, and the inverters that operate the Ni inverters 1 in the ascending order (from the smallest one) are determined.

[0045] Then, the process proceeds to step S _8, it instructs the operation at the maximum conversion efficiency Ni stand inverter 1 determined.

At this time, the operable one of the Ni inverters 1 is actually operated at the maximum conversion efficiency to output AC power, and the parallel combined power thereof always exceeds the required power Pi. Is supplied to the system load or the like efficiently.

Then, at time tz, the driving schedule
Step S until the process ends₉, S _TenStep through
S₁₁And prepares for the next time Ti operation.
When the operation of the Ti is started, step S₁Processing from
Return.

By repeating this process, at each time Ti, the inverters 1 of the number of operating units Ni determined in order from the one with the smallest operation amount are operated. In this case, each inverter 1 operates at the maximum conversion efficiency of, for example, the load factor A%. Since the operation is performed, the power conversion is always performed most efficiently, and the inverters 1 are evenly selected and operated without unevenness, so that the life of the device becomes significantly longer.

Next, when the number of operable units Na of the inverter 1 is smaller than the required power Pi, for example, in the determinations of steps S ₄ and S ₅ , the determined number of operable units Ni is the number of operable units Na. In some cases, Ni> Na.

[0050] At this time, in order to continue as much as possible the operation, the determination in step S _4, whether the AC power Pr · Na to all the inverters 1 of the operation enabled obtained by operating at rated output required power Pi is can cover and, step through the step S ₄ when the Pr · Na> Pi in affirmative (YES) S
_{In step 12} , the number of operating units Ni is changed to Na, and all the operable inverters 1 are instructed to operate at a load factor at which Pi / Na output power is obtained.

Meanwhile, it becomes Ni> Na, and, when the required power Pi exceeds the power Pr · Na, the process proceeds from step S ₄ to step S _5, step S ₁₃ through a positive this step S ₅ proceeds to, after stopping the operation of all the inverter 1, the control circuit 4 of FIG. 1 in step S ₁₄
, An output of an abnormal alarm is instructed to the notifying unit 7, and the notifying unit 7 warns the abnormal stop by sound (buzzer sound, etc.), light (lamp, etc.), or the like.

Therefore, even if it becomes difficult to operate at the maximum conversion efficiency, as long as each inverter 1 is operated at a load factor equal to or less than the rated output and AC power equal to or more than the required power is obtained, the operation is continued to supply the load. Is performed stably.

In addition, when the inverter 1 is operated at the rated output, the operation is stopped and the occurrence of the abnormality is notified when the inverter 1 is operated at the rated output. By the way, it goes without saying that the number of inverters 1 may be any.

When it is not necessary to consider the failure of each inverter 1, etc., the above-mentioned (iv), (v), (vi)
May be omitted. In this case, control and the like are significantly simplified.

Each unit converter is composed of various inverters other than inverters or various forward converters such as converters, and a plurality of these unit converters are multiplexed in parallel to perform DC / AC or AC / DC conversion. Of course, the present invention can be applied to the case of performing power conversion in the same manner as described above.

[0056]

The present invention has the following effects. First, in the case of claim 1, the operating number of the unit converters (inverters 1) at each time point is determined to be the number at which the generated power obtained by the parallel multiplex operation at the maximum conversion efficiency becomes equal to or more than the required power at each time point. be able to.

Then, in order to operate the unit converters of the number of units selected in order from the one with the lowest operation record at the maximum conversion efficiency, the unit converters are evenly selected without unevenness and the conversion efficiency is increased. It is possible to provide a power conversion device that can operate and convert a required amount of power at each time point, and is excellent in both energy saving and economy.

In the case of claim 2, when a part of each unit converter cannot be operated due to a failure or the like, the number of inoperable units (inoperable units) is determined as the number of operating units at each time. Therefore, it is possible to select the unit converters of the determined number in order from the one with the smallest operation record and to operate at the maximum conversion efficiency.

In this case, even if some of the selected unit converters are inoperable, the unit converters are evenly selected without deviation and operated at a high conversion efficiency, and the electric power that can reliably cover the required power is supplied. Can be generated, and the reliability and the like are further improved.

Furthermore, in the case of claim 3, even if all the operable unit converters are operated at the maximum conversion efficiency, the generated power is insufficient, but if all the unit converters are operated with a higher output, When the required power can be satisfied, the operable unit converters can be operated equally to generate power that can cover the required power, and the reliability can be further improved.

Further, in the case of claim 4, even when all the operable unit converters are operated at the rated output, the generated power is insufficient. Operation can be stopped and an abnormality can be alerted,
Reliability and the like are further improved.

Further, in the case of claim 5, each unit converter comprises an inverter 1 for power of the same capacity, and the DC power supply 3 of each inverter 1 comprises a secondary battery or a solar battery for storing power. Therefore, an electric power storage facility or a solar power generation device to which the present invention is applied can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of one embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG. 1;

FIG. 3 is a characteristic diagram of a general conversion efficiency of an inverter.

[Explanation of symbols]

 Reference Signs List 1 inverter 3 DC power supply 4 control circuit 7 notification unit

Continued on front page F term (reference) 5G066 HA15 HB03 5H006 CB09 CC04 CC08 DA03 DA06 5H007 AA05 BB07 CC04 CC05 DA04 DB13 DC03 5H420 BB03 BB14 CC03 CC04 DD03 EA02 EA43 EA48 EB13 EB39 EB40

Claims (5)

[Claims] 1. A power conversion apparatus comprising: a plurality of unit converters of the same capacity, which are multiplexed in parallel and are composed of an inverter or a forward converter for power, and selectively convert each of the unit converters according to a change in a set required power. In the power converter that generates power to cover the required power, a unit that determines the number of operating unit converters by dividing the required power by the output power of the maximum conversion efficiency of each unit converter, Means for storing the individual integration results of the output powers of the unit converters as the amount of operation of each unit converter, and selecting the unit converter of the number of operating units determined in ascending order of the amount of operation. And means for operating at the maximum conversion efficiency respectively. 2. A unit for storing the number of operable unit converters and the number of unavailable units due to a failure or the like, and when determining the number of unit converters to be operated, a required power of each unit converter is calculated. The number obtained by dividing by the output power of the maximum conversion efficiency is multiplied by a coefficient obtained by dividing the total number of the respective unit converters by the number of operable units, and the number obtained by taking into account the number of non-operable units is the number of operating units. The power converter according to claim 1, wherein the power converter is determined as: 3. When the determined number of operating units exceeds the number of operable unit converters, and the required power is equal to or less than the upper limit of the rated output power of each unit converter multiplied by the number of operable units, 3. The power converter according to claim 2, further comprising means for operating all operable unit converters with an output obtained by dividing the required power by the operable number. 4. If the required power exceeds the upper limit value obtained by multiplying the rated output power of each unit converter by the number of operable units when the determined number of operated units exceeds the number of operable unit converters, 4. The power converter according to claim 2, further comprising means for stopping the operation of the unit converter and generating an abnormality alarm. 5. The unit converter according to claim 1, wherein each of the unit converters comprises an inverter for power having the same capacity, and the DC power supply of each inverter comprises a secondary battery or a solar battery for storing power. The power converter according to claim 2, 3, or 4.