JPH05252668A - Power converter - Google Patents

Abstract

PURPOSE:To improve voltage waveform of parallel output bus by optimally controlling a power converter based on the parameter for controlling the output voltage or the phase of each order higher harmonic. CONSTITUTION:When basic wave output voltage or basic wave output phase fluctuates, a basic wave control parameter operating unit 121 detects fluctuated output current and operates parameters, e.g. basic wave voltage, basic wave phase, impedance, of a system based on a plurality of detected data and produces estimated parameter data. An reference output controller 122 determines optimal control data for basic wave output voltage and basic wave output phase based on the system parameter estimation data operated by the basic wave control parameter operating unit 121 and then controls a power conveter 2 optimally based on thus determined data. According to the constitution, power converters 2 having different capacity and different constitution can be linked and the voltage waveform of parallel output bus can be improved.

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 supplying stable AC power to a load by inputting a first power source such as a commercial power source or a second power source having a storage battery, a fuel cell or the like as an energy source. In particular, the present invention relates to a power conversion device configured so that outputs of a plurality of power conversion devices are interconnected for capacity increase or redundancy.

[0002]

2. Description of the Related Art As a power supply for an important load system such as a computer, there is no power conversion device that supplies stable AC power using a storage battery as a power supply even when the AC input power supply is interrupted or when the AC input system has a momentary voltage drop. Blackout power supply (hereinafter U
It is becoming widely used as PS). In particular, a system in which UPSs are operated in parallel is used to increase the capacity and improve the reliability of power supply with the increase in the scale of the system, which is the first of the recent online communication networks. FIG. 3 is a block diagram showing an example of a conventional UPS of this type.

In the figure, 10 is an AC input power source, 1a
1b is a UPS in which outputs are connected in parallel, 12 is a load, and 13 is a parallel output busbar. The UPSs 1a and 1b have the same internal configuration and are distinguished by adding subscripts a and b. The main circuits of the UPS 1a and 1b are converters 11a and 11b, storage batteries 12a and 12b, inverters 13a and 13b, AC filters. It is composed of 14a and 14b.

Although the main circuit configuration of the UPS 1a, 1b is well known, the power of the AC input power source 10 is converted into the converter 11.
a, 11b convert to DC power, and inverters 13a, 1
3b converts into AC power again, and the AC filter 14
The output voltage waveform is improved to a sine waveform with a and 14b, and load 1
Power to 2. The storage batteries 12a and 12b are normally charged by the converters 11a and 11b, and when the AC input power source 10 has a power failure, the DC power of the storage batteries 12a and 12b is supplied to the inverters 13a and 13b, so that the UPS 1
Power supply to a and 1b continues uninterrupted.

The purpose of parallel operation of the UPS 1a, 1b connected in parallel via the parallel output bus bar 13 is to increase the output capacity by making the system capacity the sum of the output capacities of the UPS 1a and 1b, or for one of the UPS 1a, 1b. This is for the purpose of redundancy for improving the reliability of power supply as a reserve capacity.

This parallel operation constitutes a control circuit 11
It is controlled as follows by 0a to 119a and 110b to 119b. That is, the active power detectors 119a and 119b detect the active power deviation ΔP and the reactive power detectors 110a and 110b detect the reactive power deviation ΔQ from the output current deviation ΔI and the output voltage of each UPS detected by the CTs 111a and 111b. .. By the active power deviation ΔP,
A voltage controller 115a for performing phase correction on the phase synchronization control circuits 118a, 118b with the oscillators 117a, 117b as a reference and controlling the output voltage by the reactive power deviation ΔQ,
115b (having a pulse width modulation function so as to reduce the output waveform distortion of the inverter)
Parallel operation control is performed by controlling the drive signals of a and 13b. The operation principle of this parallel operation control is a well-known technique, for example, in Japanese Patent No. 1215332 “Inverter parallel operation device”, and therefore its detailed description is omitted.

In the UPS parallel operation system as shown in FIG. 3, it is necessary to send and receive signals between devices for parallel balance correction control as shown in FIG.
It was also necessary that a and 1b had the same capacity, the same configuration, and the same control function.

[0008]

The technical problems of the parallel operation system for the power converter according to the prior art will be summarized as follows based on the example of FIG. (1) Each power conversion device needs to exchange control signals for parallel operation with each other, and it cannot be configured as an independent control in the true sense of the device unit. (2) The output of each power converter was controlled so that the power distribution was even, and parallel operation was limited to power converters with the same rating and characteristics.

(3) Regarding the expansion of the power conversion device to increase the power supply capacity corresponding to the expansion of the load computer system, from the above (2) the equipment plan that accurately estimates the spare capacity from the initial planning stage. If it is not possible to do so, it is difficult to respond flexibly, and since there is a risk of extension work with online power supply because it is necessary to send and receive control signals from the above (1), there are restrictions on the time and time for extension work. there were.

(4) Even if the waveform distortion of the parallel output bus voltage is large due to the low output voltage harmonic distortion correction performance of the existing power converter, it is necessary to match the characteristics of the new power converter with that of the existing power converter. High-performance devices cannot be operated in parallel due to the control technology, and in order to improve the parallel output bus voltage waveform distortion, it was necessary to install a filter for absorbing harmonics. (Most of the recent computers and communication devices are rectifier loads that generate harmonic currents, so there is an increasing demand for low distortion of the output voltage of power converters that support this.)

The present invention has been made in view of the above points, and in a system in which the outputs of power conversion devices are interconnected for increasing power supply capacity or for redundancy, exchange of control signals between devices is performed. It is an object of the present invention to provide a high-performance and flexible power conversion device that enables interconnection of power conversion devices having different capacities and different configurations, and that can also improve waveform distortion of parallel output bus voltage. ..

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention performs power conversion from a change in the fundamental wave output current when the fundamental wave output voltage or the fundamental wave output phase of the power converter is changed. A means for optimally controlling the fundamental wave output voltage and fundamental wave output phase of the power converter by obtaining a control pattern that shares the output power according to the rating of the equipment, and each harmonic output voltage of the power converter, or Each harmonic output voltage or each harmonic for improving the waveform distortion of the parallel output bus voltage from the change of each harmonic component of the waveform distortion of the parallel output bus voltage when the output phase of each harmonic is changed. The control unit of the power converter is provided with means for optimally controlling the wave output phase control parameters.

[0013]

In the power converter having such a configuration, the optimum control parameters for controlling the fundamental wave output are the fundamental wave output voltage and the fundamental wave output current when the fundamental wave output phase is changed. The optimum control parameter for controlling the harmonic output, which is estimated from the change data, is the harmonic output voltage and each harmonic component of the parallel output bus voltage when the harmonic output phase is changed. The control operation is performed while learning the optimum control state, which is estimated from the change data, and the output power sharing and the waveform distortion improvement of the parallel output bus voltage are always learned.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the components denoted by the same reference numerals as those in FIG. 3 have the same functions as those in FIG. 3, and the description thereof will be omitted.

In FIG. 1, 2 is a UPS as a power conversion device corresponding to 1a and 1b of FIG. 3, and 21 is an inverter.
, 13a is an interconnection impedance for connecting the parallel output bus 13 to the parallel output busbar 13 (may have a configuration similar to that of 14a and 14b in FIG. 3), 121 is a fundamental wave control parameter calculator, 122 Is a fundamental wave output reference controller, 123 is a harmonic component detector that detects each harmonic component of the parallel output bus voltage, 124 is a harmonic control parameter calculator, and 125 is a harmonic output reference controller. .. Next, the operation of the embodiment of the present invention configured as described above will be described.

The fundamental wave control parameter calculator 121 is based on the fundamental wave output voltage and the fundamental wave output phase change command given from the fundamental wave output reference device 122 to the voltage controller 116a and the phase synchronization controller 118a. Wave output voltage, fundamental wave When the output phase changes, the output current that fluctuates is detected, the command of change is changed, and this is repeated while repeating this, and the fundamental wave voltage and fundamental wave of the system are detected. Parameters such as phase and impedance are calculated and estimated.

The output reference controller 122 is a system parameter calculated by the fundamental wave control parameter calculator 121.
The optimum control data of the fundamental wave output voltage and the fundamental wave output phase is obtained from the data estimation data, and this data is calculated by the voltage controller 116.
a as a reference for fundamental wave control to the phase synchronization controller 118a.

For example, if the unknown parameters of the system are three, that is, the no-load terminal voltage ex, the impedance X, and the load current IL, the fundamental wave output voltages ek1, ek2, e are changed by changing the reference.
Estimating parameters can be calculated by solving the following relational expressions by taking Ik1, Ik2, and Ik3 of changes in the fundamental wave output current data when changing to three kinds of k3. Normally, the capacity of the system is related to impedance, so if the impedance and load capacity of the system are obtained by this method, UPS
The output power sharing of 2 can be determined. (Ek1−ex) / (K + X) = Ik1−IL (ek2−ex) / (K + X) = Ik2−IL (ek3−ex) / (K + X) = Ik3−IL where K is the interconnection impedance 21 The optimum control operation of harmonics is described in. In order to explain the algorithm of the optimum control operation of the harmonics in the embodiment of FIG. 1, a flowchart of the harmonics control is shown in FIG.

First, each harmonic component of the parallel output bus voltage is analyzed by the harmonic component detector 123, and the control operation is started from the nth harmonic having the largest component based on the analysis result. From the harmonic output reference controller 125 to the PWM controller 11
A command (for example, a command to advance) for changing the output phase of the nth harmonic is given to 5a, and the PWM controller 115a is based on this command.
As a result of the correction of the sine wave reference waveform in the inside and the change of the n-th harmonic output phase, it is detected how the n-th harmonic component of the parallel output bus voltage changes, and the harmonic control parameter calculator 124 Estimate how the next harmonic phase reference should change next. (If the output phase is advanced to reduce the nth harmonic component, it is estimated that it is better to proceed further.) Repeat this operation to estimate the optimum phase reference for reducing the nth harmonic of the parallel output bus voltage. Then, the control operation for the nth harmonic voltage is performed. n
Similarly for the next harmonic voltage, the harmonic output reference controller 1
A command to change the output voltage (for example, a command to increase) is given from 25 to the PWM controller 115a, and the harmonic control parameter calculator is detected while detecting how the nth harmonic component of the parallel output bus voltage changes. At 124, the direction of change of the nth harmonic voltage reference is estimated. (If the output voltage is increased and the n-th harmonic component is reduced, it is better to increase it further.) This operation is repeated.
The optimum voltage reference for the nth harmonic is estimated from the conditions such as the output current allowable limit of the switch 13a. Similarly, even for harmonic components of different orders, the optimum phase reference → the optimum voltage reference are sequentially estimated, and this operation is performed at a specified cycle to always follow the changes in the system parameters. The optimum control can improve the waveform distortion of the parallel output bus voltage.

In this way, in this embodiment, the harmonic output voltage is controlled so as to control the fundamental wave output voltage and the fundamental wave output phase while learning the system parameters and reduce the waveform distortion of the parallel output bus voltage. , By learning and controlling the optimum control parameter of the harmonic output phase, it is possible to connect power converters of different capacities and different configurations in parallel, and the output harmonic distortion correction performance of existing equipment is low. Even in the case, the waveform distortion of the parallel output bus voltage can be easily improved.

In the embodiment of FIG. 1, the UPS is cited and described, but the power converter is not limited to the UPS and may be another power converter. Further, the circuit configuration and method may be other types of power conversion devices without being limited to the combination of the converter and the inverter. Further, the storage battery, which is the second power source, may be another energy source such as a fuel cell.

[0022]

As described above, according to the present invention, in a system in which the outputs of power converters are interconnected for increasing power supply capacity or for redundancy, mutual exchange of control signals between devices is possible. In addition, it is possible to provide a high-performance and flexible power conversion device that enables interconnection of power conversion devices having different capacities and different configurations and that can also improve waveform distortion of the output parallel bus voltage.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining an optimal control algorithm for harmonics in the embodiment shown in FIG.

FIG. 3 is a block diagram showing a configuration example of a parallel operation system of a conventional power conversion device.

[Explanation of symbols]

 1a, 1b ... UPS 2 ... UPS 10 ... AC input power supply 11a, 11b ... Converter 12 ... Load 12a, 12b ... Storage battery 13 ... Parallel output busbars 13a, 13b ... Inverter 14a, 14b ... AC filter 110a, 110b ... Reactive power detector 111a, 111b ... CT 115a, 115b ... PWM controller 116a, 116b ... Voltage controller 117a, 117b ... Oscillator 118a, 118b ... Phase synchronization controller 119a, 119b ... Active power detector 21 ... Interconnection impedance Dance 121 ... Fundamental wave control parameter calculator 122 ... Fundamental wave output reference controller 123 ... Harmonic component detector 124 ... Harmonic control parameter calculator 125 ... Harmonic output reference controller

Claims (1)

[Claims] 1. A power converter for supplying a stable AC power to a load by inputting a first power supply such as a commercial power supply or a second power supply using a storage battery, a fuel cell or the like as an energy source. The output of the power conversion device is configured to be interconnected with parallel output buses for increasing power supply capacity or redundancy, and the fundamental when the fundamental wave output voltage or the fundamental wave output phase of the power conversion device is changed Means for controlling the fundamental wave output voltage and the fundamental wave output phase of the power converter according to the change of the wave output current, and when changing each harmonic output voltage or each harmonic output phase of the power converter Estimating the control parameter of each harmonic output voltage or each harmonic output phase in order to improve the waveform distortion of the parallel output bus voltage from the change of each harmonic component of the parallel output bus voltage of Means and this estimated control pattern A power conversion device comprising means for controlling the power conversion device according to a lamella.