JPH0583862A - Power converter - Google Patents

Abstract

PURPOSE:To eliminate a restriction in a parallel operation limited to power converters having the same rating and the same characteristics by estimating a parameter of a system and controlling with an optimum control parameter. CONSTITUTION:A system parameter calculator 121 detects an output current varying when output voltage and phase are varied based on variations in the output voltage and phases and a command applied from an output reference controller 122 to a voltage controller 116a and a phase sync controller 118a, and calculates parameters such as voltage, phase, impedance of a system based on it to estimate it. An output reference controller 122 obtains optimum control outputs of output voltage and phase from system parameter estimated data calculated by the calculator 121 and applies the output as a reference of control of the controllers 116a and 118a. Thus, a restriction in a parallel operation limited to power converters having the same rating and the same characteristics can be eliminated.

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 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. 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 An uninterruptible power supply (hereinafter referred to as UPS) that supplies stable AC power using a storage battery as a power supply even when an AC input power supply is interrupted or a momentary voltage drop is used as a power supply for an important load system such as a computer. Is becoming widely used. Especially in recent years online communication networks
A system that operates UPS in parallel is also used to increase the capacity and improve the reliability of power supply as the system scales up.

FIG. 3 shows an example of a conventional parallel operation system of this kind of UPS. In FIG. 3, 10 is an AC input power source, 1a and 1b are UPSs in which respective outputs are connected in parallel, 1
Reference numeral 2 is a load, and 13 is a parallel output busbar. UPS 1a and 1
The internal configurations of b are completely the same and are distinguished by adding subscripts of a and b, and their main circuits are converters 11a and 11b.
b, storage batteries 12a, 12b, inverters 13a, 13
b, AC filters 14a and 14b. UPS
The main circuit configurations of 1a and 1b are known, but the power of the AC input power source 10 is converted into DC power by the converters 11a and 11b, and converted into AC power again by the inverters 13a and 13b. The output voltage waveform is improved to a sine waveform by the AC filters 14a and 14b, and power is supplied to the load 12. The storage batteries 12a and 12b are normally charged by the converters 11a and 11b, and when the AC input power source 10 fails,
By supplying the DC power of 2a and 12b to the inverters 13a and 13b, the UPS 1a and 1b continue the power supply without interruption.

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 taking the system capacity as the sum of the output capacities of the UPS 1a and 1b, or for one of the UPS 1a, 1b. It is a redundancy to improve the power supply reliability 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 deviation ΔI and the output voltage of the output current of each UPS detected by the CTs 111a and 111b. The phase synchronization controller 1 based on the oscillators 117a and 117b based on the active power deviation ΔP
18a, 118b phase correction, reactive power deviation Δ
The voltage controller 116 that controls the output voltage at a constant voltage by Q
a, 116b, and the inverters 13a, 115b generated by the gate signal generators 115a, 115b.
Parallel operation control is performed by controlling the drive signal of 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 the like, and therefore detailed description thereof will be omitted.

In the UPS parallel operation system as shown in FIG. 3, it is necessary to exchange signals between the 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 performance.

[0007]

The technical problems of the parallel operation system for the power conversion device according to the prior art will be summarized as follows based on the example of FIG.

(1) It is necessary for each power conversion device to exchange control signals for parallel operation control with each other, and it has not been possible to have a structure of independent control in a device unit in the true sense. (2) The output of each power converter was controlled so that the voltage distribution was equalized, 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 item (2), equipment that accurately estimates the spare capacity from the initial planning stage. It is difficult to respond flexibly unless a plan is made, and since it is necessary to send and receive control signals according to item (1) above, expansion work with online power supply is required.
Due to the risk of the above, there were restrictions on the time and time for the expansion work.

The present invention has been made in view of the above points, and in a system in which the outputs of power converters are interconnected for capacity increase or redundancy, mutual exchange of control signals between the devices is performed. An object of the present invention is to provide a flexible power conversion device that is not necessary and is not limited to a system configuration of devices having the same rating and the same characteristics.

[0011]

In order to achieve the above object, the present invention provides a parallel output (parallel connection) of parallel outputs connected in parallel based on a change in output current when the output voltage or output phase of a power converter is changed. A means for estimating the parameters of the busbar and a means for optimally controlling the output voltage and output phase of the power converter so that the output power is shared according to the estimated parameters according to the estimated parameters. It is provided in the control unit of the power converter.

[0012]

In the power converter having such a configuration, the optimum control parameter for controlling the output voltage and the output phase is the data of the change in the output current when the output voltage and the output phase are changed. Based on the estimation, the control operation is always performed while learning the optimum control state.

[0013]

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 designated by the same numbers as those in FIG. 3 have the same functions as those in FIG. 3, and the description thereof will be omitted. However, 2 is a UPS corresponding to 1a and 1b in FIG.
Reference numeral 21 is an interconnection impedance for connecting the inverter 13a to the parallel output bus bar 13 (14a, 14a in the configuration of FIG. 3).
(The configuration may be the same as that of b) 121 is a system parameter calculator, and 122 is an output reference controller.

The system parameter calculator 121 outputs the output voltage and the output phase based on the output voltage and the output phase change and the command given from the output reference controller 122 to the voltage controller 116a and the phase synchronization controller 118a. When there is a change, the fluctuating output current is detected, and the parameters of the system voltage, phase, impedance, etc. are calculated and estimated based on this (divided into active current and reactive current). Output reference controller 12
2 obtains the optimum control data of the output voltage and the output phase from the system parameter estimation data calculated by the system parameter calculator 121, and determines this data as the voltage controller 1
16a, which is given to the phase synchronization controller 118a as a control reference. Next, the operation of the embodiment of the present invention configured as described above will be described.

To facilitate understanding of the operation of FIG. 1, FIG.
The equivalent circuit including the parameters of the system connected to is described in.
In FIG. 2, eK is the output voltage of the inverter 13a, eX
Is the no-load terminal voltage on the grid side, K is the interconnection impedance 2
1, X are impedances on the system side, IK is the output current of UPS2, and IL is the load current, and both are vector quantities having amplitude and phase. Where eK,
X and IL are unknown parameters, and other parameters are UPS2's own parameters or detectable parameters.
It is.

For example, when the output reference controller 122 gives the voltage controller 116a a command to change the output voltage eK of the inverter 13a into three kinds of eK1, eK2, and eK3, the output current IK1 of the UPS2, Suppose it has changed to IK2 and IK3. This change in the output current IL is detected by the system parameter calculator 121 via the CT 111a.

In three cases, the parallel output bus bar 13
It can be considered that IL is constant in any case, assuming that there is almost no change in the voltage of, and the following three relational expressions are obtained. (EK1−eX) / (K + X) = IK1−IL …… (1) (eK2−eX) / (K + X) = IK2−IL …… (2) (eK3−eX) / (K + X) = IK3−IL ・ ・ ・(3) Unknown parameters eK, X, IL from these three relations
Is required.

If only the amplitude of the output voltage eK is changed, the above three relational expressions can be solved only by the amount corresponding to the reactive component of the current, and the parameter corresponding to the reactive component can be obtained.

Similarly, the change of the output current IL when the change command of the output phase of the inverter 13a is given to the phase synchronization controller 118a is detected by the system parameter calculator 121, and the relational expression as described above is obtained. If you solve with, you can obtain the parameters corresponding to the effective amount. In this way, the system parameters eK, X, and IL are the system parameter computing unit 12
1 is calculated and estimated. Based on this estimated parameter, the output reference controller 122 finds the optimum control parameters for the output voltage and output phase. Normally, the capacity of the system is related to the system impedance X, so the load sharing between the system and UPS2 is determined from the size of X, and I
The power to be output by UPS2 can also be set from the estimated data of L. That is, the load sharing between the system and the output of UPS2 and the output voltage and output phase optimum control parameters for controlling the power to be output by UPS2 to a level commensurate with the rating of UPS2 are voltage controller 116a and phase synchronization control. Bowl 118a
Given as a control criterion. As a result, the output voltage and the output phase of the UPS 2 are optimally controlled, and if the above operation is performed in a predetermined cycle, the optimal control that always follows the changes in the system parameters can be performed.

In this way, in this embodiment, the parameters of the system are estimated, and the optimum control based on the parameters is controlled, so that the power conversion device having the same rating and the same characteristics is limited. Since the restriction of parallel operation is solved and the control signal for parallel operation control is not required, it is possible to configure a flexible system that facilitates equipment expansion work corresponding to load system expansion.

Although the embodiment of FIG. 1 has been described with reference to UPS, the invention is not limited to UPS, and another power conversion device may be used. Further, the configuration is not limited to the (converter + inverter) configuration, and the circuit configuration and system may be another type of power conversion device. Furthermore, the storage battery that is the second power source may be another energy source, such as a fuel cell.

[0023]

As described above, according to the present invention, in a system in which the outputs of power conversion devices are interconnected for capacity increase or redundancy, it is not necessary to exchange control signals between the devices. In addition, it is possible to provide a power conversion device that can be flexibly adapted to load system expansion, without being limited to a system configuration of devices having the same rating and the same characteristics.

[Brief description of drawings]

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

FIG. 2 is an equivalent circuit diagram for explaining the operation of the embodiment of 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, 2 ... UPS 10 ... Input AC power supply 11a, 11b ... Converter 12 ... Load 12a, 12b ... Storage battery 13 ... Parallel output busbars 13a, 13b ... Inverter 14a, 14b ... AC filter 110a, 110b ... Invalid Power detectors 111a, 111b ... CT 115a, 115b ... Gate signal generators 116a, 116b ... Voltage controllers 117a, 117b ... Oscillators 118a, 118b ... Phase synchronization controllers 119a, 119b ... Active power detector 21 ... Interconnection Impedance 121 ... System parameter calculator 122 ... Output reference controller

Claims (1)

[Claims] 1. A power converter for supplying stable AC power by inputting a first power source such as a commercial power source or a second power source using a storage battery, a fuel cell or the like as an energy source,
The outputs of a plurality of the power conversion devices are configured to be interconnected for capacity increase or redundancy, and the output voltage or output current of the power conversion devices is changed depending on the output current. An electric power conversion device comprising means for estimating a parameter of a system to be connected and means for controlling an output voltage and an output phase of the electric power conversion device according to the estimated parameter.