KR20120094983A - A multi-parallel energy storage system including multi-phases power converters for regulating the catenary voltage of electric railway - Google Patents

Abstract

PURPOSE: A multi-parallel energy storage system including a multi-phase power converter is provided to stably maintain line voltages by controlling an electric power inverter by a line voltage estimation algorithm. CONSTITUTION: A multi-phase power converter is connected to a line(1) of an electric railway in parallel. An initial charge device(5) and a high speed direct current circuit breaker(4) connect or divide the line and an energy storage device. An input filter reactor(8) and an input filter capacitor(9) control current change and voltage change which are made according to the operation of an electric power inverter. A voltage transformer(10) measures the voltage of an input unit which passes a voltage transformer(3) for measuring the line voltage and a filter. A current transformer(24) measures currents which are supplied or absorbed to the line.

Description

A multi-parallel energy storage system including multi-phases power converters for regulating the catenary voltage of electric railway}

The present invention is a multi-parallel energy storage device having a multi-phase power converter for voltage stabilization of an electric railway wire, and determines the voltage fluctuations occurring in the wire during vehicle backing and braking by a prediction algorithm to inject or absorb current into the wire. It is possible to reduce the ripple in the output voltage waveform by controlling the interleaved PWM control method of the multi-phase power converter and the multi-phase power converter and the phase separation method in the event of a failure. The present invention relates to an energy storage device capable of continuously operating by separating only a corresponding energy storage unit in which a failure has occurred by allowing connection or disconnection by means of a failure.

Among the braking methods of electric railway vehicles, regenerative break, which is an electric braking method that obtains braking force by returning kinetic energy of a vehicle to electric energy by an electric motor and supplying the electric wire, is widely used.

The regenerative braking method can reduce the electricity consumption of the entire wire, and it is widely used as a method of operating an electric railway vehicle because it has the advantage of preventing noise, dust, and abrasion wear generated during mechanical braking.

In the powering mode in which the vehicle uses electric energy, the line voltage is lower than the rated voltage due to the rectifier voltage drop, and the line voltage becomes higher than the rated voltage due to the energy returned during regenerative braking. Electromagnetic disturbances of other equipment due to voltage fluctuations shown in the diagram may affect the operation of other electric vehicles as well. In addition, when the vehicle distance is far or the number of running vehicles is small, when the voltage generated by the regenerative braking is not consumed and when the threshold value is exceeded, the braking method uses the electric energy consumed by the braking resistor mounted on the vehicle. As well as severe fluctuations in voltage, energy use efficiency is reduced.

In order to stabilize the line voltage fluctuating with vehicle operation and to improve the energy consumption efficiency, it is necessary to configure a parallel structure with a rectifier that supplies electricity to the line using a large-capacity energy storage and power converter that can accumulate and supply electrical energy. It has been proposed in prior patents (application no. 10-2008-7015332) and prior patents (application no. 10-2008-0056217).

However, in the above-described energy storage system of the prior art, even if there is one or more power converters (DC / DC converters) that are responsible for charging and discharging energy, each of them operates independently, so that switching noise is irregular at the line voltage. In this case, a severe voltage fluctuation may occur in the line voltage, and if a single power converter fails, charging and discharging using the corresponding energy storage medium is impossible.

In particular, when several energy storage systems are distributed and connected to a single wire, a plurality of tanks are operated by reading the voltage of the wire and charging above the charging reference voltage and discharging electric energy below the discharge reference voltage. Has a problem of frequently operating in response to the noise of the generated line voltage, and the energy charging and discharging between several energy storage system is not efficient. In order to avoid this problem, the charging start voltage of 1800V is applied to the wire with rated voltage of 1500V, and the operation voltage band is largely operated by setting the operating voltage band large, such as setting the voltage to start discharging at 1000V. There is a problem with this.

In the energy storage system, the energy storage device has a small internal voltage of several volts, so the large number is connected in series, and the large number is connected in parallel to save energy. It constitutes wealth. A large number of series-connected energy storage media generate heat due to internal loss during charging or discharging, and the amount of charge or discharge varies depending on internal impedance, resulting in voltage unbalance of the series-connected device.

When the voltage charged in the unit energy storage device is higher than the withstand voltage, burnout may occur, and thus, the energy storage device needs to be separated from the wires for protection, and thus, the energy storage device may not function as an energy storage device. Recently, in order to increase the energy use efficiency of a vehicle, a vehicle that is not equipped with a braking resistor is being introduced. In the case of such non-resistance vehicles, the energy storage device must suppress an increase in the line voltage because the vehicle has no high resistance. Reliability is required.

On the other hand, when the driving frequency of the vehicle or the number of vehicles connected to the line changes, it is necessary to adjust the capacity of the energy storage device pre-installed in the substation. However, the related art has a disadvantage in that the capacity of the initially designed energy storage unit and the power converter capacity are not freely adjusted.

Accordingly, the present invention is to solve the problems of the prior art described above, the power converter which is a main part of the energy storage device is multi-phased and configured in a parallel connection structure, the switch to be connected or disconnected By increasing the degree of freedom of operation of the energy storage device by multiplexing the installed energy storage unit, it increases the reliability and expandability of the device, and provides an energy storage device that can stabilize the line voltage by an algorithm and control method that accurately determines the fluctuation of the line voltage. It aims to do it.

In order to achieve the above object, a multi-parallel energy storage device having a multi-phase power converter for voltage stabilization of an electric railway wire according to the present invention comprises: a multi-parallel energy storage unit having a switch capable of connecting or disconnecting circuits; A power conversion unit including a plurality of face-rack structured power circuits, filter reactors, and current transformers in parallel as basic units; And a controller capable of controlling a plurality of power converters by interleaved PWM and predicting a change in the line voltage.

The energy storage unit of the multi-parallel structure comprises a unit energy storage module having a constant capacity consisting of an electric energy storage medium consisting of a series and a parallel circuit, and a basic unit by installing one switch and a monitoring unit for each storage module. It is configured so that the system builds the required capacity by constructing a plurality in parallel and has a structure that can be instantaneously connected and disconnected as needed. The monitoring unit normally measures the cell voltage and temperature of the energy storage medium, transmits the abnormality by communication with the above-described control unit, and operates the switch so that the corresponding energy storage unit can be separated or input from the system.

The multi-phase power converter connects two power semiconductor devices to have a face-rack structure, connects a filter reactor and a current transformer between the two devices to form a single basic unit, It is composed by connecting several in parallel to meet the current capacity of power converter required, and has a structure that can be expanded as needed. Power semiconductor devices located in power converters connected in parallel are driven by interleaved PWM pulses that control the power semiconductor devices ON / OFF at a phase interval divided by a constant PWM period. Current ripple and voltage ripple can be minimized in injecting current or absorbing current from the wire.

In addition, the operation of each of the above-mentioned multi-phase power converter is monitored for each phase by the controller, and a phase in which a fault such as an overvoltage, an overcurrent, an overtemperature, a phase imbalance, or an abnormality in a power conversion element is detected stops PWM control. In the next PWM period, the control of the line voltage can be automatically continued by generating a new phase interval except for the control interrupted constant in the paralleled constant and applying an interleaved PWM driving signal having the new phase interval to the power converter. It works with an algorithm.

The multi-phase power converter obtains the voltage of the fluctuating electric wires by using a prediction algorithm, generates a current target value for supplying or absorbing wires in the direction of reducing the error between the pre-predicted voltage magnitude and the rated voltage, and generates an interleaved PWM pulse. It is operated by the control unit can control the wire voltage stably.

In addition to the above-mentioned configuration, the input filter part composed of the current stabilization filter reactor and the voltage stabilization film capacitor in the part connected by wires, the initial charging part, the discharge circuit part, the voltage transformer, the current transformer, the protective fuse, and the high speed DC circuit breaker, etc. It further comprises a detection and protection circuit unit is configured to enable the charging and discharging of electrical energy.

The present invention has a high degree of freedom in selecting a multi-phase power converter composed of a plurality of parallel circuits and a multi-parallel energy storage device having respective switches, thereby improving reliability of the system when charging and discharging energy for voltage stabilization of an electric wire. It can secure and additionally save energy.

The interleaved PWM control method by the phase difference of the multi-phase power converter composed of multiple parallel circuits produces small switching ripple, which improves the power quality of the line voltage, and maintains the line voltage stably by controlling the power converter by the line voltage prediction algorithm. Can be.

In addition, the number of parallel circuits of the power converter and the number of parallel circuits of the energy storage unit can be added or removed, respectively, so that it can be made into an energy storage device having various capacities, so that it is easy to implement different capacities required for each installation location. It is possible to diversify the configuration, thereby reducing the installation and maintenance costs.

1 is a block diagram of a multiple parallel energy storage device having a multi-phase power converter according to an embodiment of the present invention;
2 is a graph illustrating a method of operating a power converter configured in four-phase parallel, in which four power converters are connected in parallel according to one embodiment of the present invention;
3 is a graph illustrating a method of operating the remaining power converter when one of the polyphase power converters has failed;
4 is a block diagram of an algorithm for predicting voltage of a rapidly changing line,
5 is a control block diagram of a control algorithm for controlling a line voltage,

Hereinafter, with reference to the accompanying drawings a multi-parallel energy storage device having a multi-phase power converter which is an embodiment of the present invention will be described the characteristics of the operation method and the invention according to the embodiment.

1 is a block diagram of a multi-parallel energy storage device (hereinafter, referred to as an energy storage device) having a polyphase power converter according to the present invention, FIG. 2 is a graph illustrating interleaved PWM control of a polyphase power converter, and FIG. 2 is a graph illustrating a method of controlling when a problem occurs in one phase, FIG. 4 is a block diagram for predicting a line voltage, and FIG. 5 is a line voltage control block diagram.

1, a multi-parallel energy storage device 100 having a multi-phase power converter connected in parallel to the electric wire 1 of the electric railway has a protection fuse 2 for permanent failure therein, and The charging device 5 and the high-speed DC circuit breaker 4 are configured to connect or disconnect the wire and the energy storage device, and to suppress the current fluctuations and the voltage fluctuations generated by the operation of the power converter and supply sufficient energy. It is provided with an input filter reactor (8) and an input filter capacitor (9) for supplying or absorbing the voltage transformer (3) for measuring the line side voltage and the voltage transformer (10) for measuring the voltage of the input part passing through the filter. It is equipped with a current transformer (8) for measuring the current to be generated, a plurality of power converters (20a ~ 20n) are connected in parallel between the input filter unit and the energy storage unit, and connected in multiple parallel The energy storage unit 60a to 60n, the discharge resistor 51 and the discharge switch 50 are further provided in parallel thereto, and control the voltage transformer 11 and the entire energy storage device for measuring the voltage of the energy storage unit. Consists of the controller 90 and the motoring device 200 for the user interface.

In the basic configuration of the power converter 20a, power semiconductor elements 21 and 22, such as an IGBT, are connected in a face-rack structure, and a filter reactor 23 and a current transformer 24 are formed at the center of the connection. In order to operate independently, the plurality of power converters generate an interleaved PWM driving pulse from the control unit 90 to operate in parallel in different phases, and apply the energy to the multiphase power converters 20a to 20n. Conversion is possible.

PWM control of the upper arm device 21 among the power semiconductor devices operates as a power converter for stepping down the voltage from the wire 1 to the energy storage units 60a to 60n, and to the lower arm. When the device 22 is driven by a PWM pulse, the device 22 operates as a power converter for boosting the voltage from the energy storage units 60a to 60n to the line 1. According to the energy flow, each phase arm element in the multi-phase power converter may be selected, or each lower arm element may be selected and PWM controlled. The device selection can be configured in software or hardware.

The current flowing through each power converter can be detected through each current transformer, and the total current can be calculated by the summation, all can be controlled by the same PWM pulse, and each PWM can be configured by an independent current controller. Pulse width control is also possible.

In FIG. 2, it is assumed that four power converters are connected in parallel, and that the flow of electric energy is stored in the energy storage unit from the wire, and the interleaved PWM generated by the control unit 90 is generated. The output current waveforms 400a to 400d of the power converters 20a to 20d and the waveform 500 of the current injected into the energy storage unit by the driving signals 300a to 300d are shown. If not controlled, overlapping or output ripple becomes large. However, when implemented with an interleaved PWM method of PWM control with a phase difference proportional to a constant connected to a multiphase power converter configuration method as in the present invention, output ripple can be reduced, resulting in a smooth current and Voltage can be obtained.

FIG. 3 assumes a case where any one of the four phase power converters in the example of FIG. 2 has a failure, and finds a failure of one phase at the previous sampling time, and at the next sampling time. The following example shows how to generate interleaved PWM pulses with the remaining three power converters. The current waveform 500 injected into the energy storage unit has three ripples due to phase separation after a failure occurs and can be operated to enable continuous operation, thereby improving reliability of the power converter.

In FIG. 1, the energy storage units 60a to 60n of the multiple parallel connection structure have a unit energy storage module 62 having a constant capacity configured by connecting energy storage media in series and parallel, and one switch 61 for each storage module. And a monitoring unit 63 may be installed to form a basic unit 60a, and the energy storage system may be configured in a multi-parallel structure so as to have a capacity required for the system by connecting a plurality of units in parallel. The monitoring unit 63 measures the cell voltage and temperature of the energy storage medium and transmits abnormality by communication with the above-described control unit, and when the internal failure occurs, the corresponding energy storage unit can be separated or input from the system. To work.

When constructing the unit energy storage module 62, in order to have sufficient internal pressure and necessary capacity, there are structural problems by connecting a large number of energy storage media in series and in parallel. Because of this, heat dissipation should be performed. Unbalance of cell voltage may occur due to the difference of internal impedance, and burnout may occur if it is out of the allowable range. Normal energy storage devices are operated to enable continuous charging and discharging of energy.

When the faulty element is removed to enable normal operation, the parallel circuit may be configured by closing the switch 61 when the magnitude of the voltage is similar to that of other energy storage modules connected in parallel. Here, there are two ways to make the voltage similar to that of other storage modules. The first method is to close the discharge switch 50 in FIG. 1 to discharge the electrical energy through the discharge resistor to make the same as the energy storage module to re-inject the voltage of another storage module, and then stop the forced discharge and store the re-injection. The second method is to make a parallel circuit by switching on the module. The second method is to charge the module to be re-inserted while the other storage module is open using the voltage of line (1), If they are the same, there is a way to inject other modules at the same time. The sequence of disconnection and reloading of the faulty module is automatically controlled by the controller.

The following describes a prediction algorithm that stably detects a line voltage that fluctuates irregularly with vehicle driving.

As a method of predicting the voltage variation of a live wire, the wire voltage at the next sampling time is estimated from the measured wire voltage detection value, the current detection value, and the slope, and used for current control in advance to stabilize the wire voltage variation. Do. When the detected voltage value of the live line at the current sample time is s (n), the slope a (n) of the live line voltage can be expressed by Equation 1 below. However, since k is a time delay constant and s (nk) is a voltage delayed by k, a (n) is a slope during k sample intervals.

Equation 1

In order to prevent a sudden change due to disturbance and surge for the obtained voltage change amount, passing through an FIR filter having a rectangular window can be written as Equation 2 below. In Equation 2, I is the size of the window function, w represents the value of the window function.

Equation 2

Since the value of Equation 2 means the average value of the voltage slope to date, it can be obtained as Equation 3 below by assuming that the change in voltage for a short period is within the rated operation range.

Equation 3

From Equation 3, the predicted value of the line voltage may be represented by a first-order function such as Equation 4 below. Here, b (n) is an intercept value of the first function and can be expressed as in Equation 5. 4 is a block diagram for obtaining a line voltage prediction value. The estimated line voltage value obtained here is used to control the PWM pulse width for driving the power converter.

Equation 4

Equation 5

In FIG. 5, the reference value of the line voltage may be set to a fixed value of general line 750V or 1500V, and the feedback line voltage detection value is substituted into the value predicted in FIG. 4 instead of the current detection value to control the output of the voltage controller. A predicted current command value is generated. By substituting the error between the command value and the measured value as the input of the current controller, the PWM pulse width for driving the power converter can be estimated and calculated. Therefore, the rapidly changing line voltage can be stabilized using an energy storage device, and energy use can be reduced by operating a constant line voltage.

1: wire of electric railway 2: protection fuse
3: line side voltage transformer 4: high speed DC circuit breaker
5: initial charging part 6: disconnector
7: input current transformer 8: input filter reactor
9: input filter capacitor 10: input voltage transformer
11: Voltage transformer on the energy storage side
20a: Power converter unit configuration a group 21: semiconductor device for phase power
22: semiconductor device for haam power 23: filter reactor
24: current transformer
20b: power converter unit configuration b group 20n: power converter unit configuration n group
50: discharge switch 51: discharge resistance
60a: energy storage unit a group 61: energy storage unit switching switch
62: energy storage module 63: energy storage medium monitoring unit
60b: group n of energy storage 60n: group n of energy storage
90: control unit 100: energy storage device
200: monitoring device 300a to 300d: interleaved PWM drive signal
400a to 400d: output current waveform 500: combined output waveform
s (n): detected voltage a (n): slope
b (n): Intercept of 1st order function: 1 sample Predicted line voltage
s ^* : line voltage reference value I ^* : current control reference value
I _real : Actual current value

Claims (7)

An energy storage device having a multi-parallel structure that can be separated to absorb or supply electric energy to suppress voltage fluctuations of wires of an electric railway vehicle;
A multiphase power converter having a plurality of phase leg structures capable of smoothing the line voltage when supplying or absorbing electrical energy to suppress voltage fluctuations in the line;
And a control unit that implements a line voltage change prediction algorithm that suppresses voltage change at an early stage by predicting a voltage change of the line. The multi-parallel energy storage device having a multi-phase power converter for stabilizing the line voltage.
The method of claim 1,
The energy storage unit of the multi-parallel structure capable of connecting or disconnecting circuits includes a unit storage module formed by configuring an electric energy storage medium in series and parallel circuits, and a unit having one switch and a monitoring unit for each module. An energy storage device having a structure in which the two units are configured in parallel to enable instantaneous circuit connection and disconnection as necessary. The method of claim 2,
The electrical energy storage medium can be connected and separated using the same type of storage medium, either an electric double layered capacitor or an ultracapacitor or a high capacity secondary battery, and the capacity can be easily increased or decreased as needed. Multiple parallel energy storage devices. The method of claim 1,
A multiphase power converter having a plurality of face-rack structures;
It consists of a face-rack power circuit in which two power semiconductor switches are connected in series, a filter reactor and a current transformer connected to the center of the face-rack structure in basic units, and many of these power converters are connected in parallel. It is an energy storage device having a multi-phase power converter that is operated in different phases by interleaved PMW (Inter leaved PWM), and easy to increase or decrease the number of parallel according to the required capacity. The method according to claim 1, wherein
A multiphase power converter having a plurality of face-rack structures;
An energy storage device having a control method of a multi-phase power converter capable of continuously operating by automatically adjusting phases by the number of separated phases when separating a problematic phase among a plurality of face-rack structures. The method of claim 1, wherein
The controller implementing the line voltage variation prediction algorithm;
The change in the line voltage generated during retrograde driving and braking of the electric railway vehicle is detected at every sampling time, and the predicted value of the line voltage preceding one sample is calculated from the calculation during the unit time, and the line voltage command value and the predicted value are compared. It is equipped with a control unit that calculates the current command value and PWM control pulse width sequentially so that the wire voltage can be effectively stabilized, and can be applied to both electric railway vehicles without braking resistors and electric railway vehicles with braking resistors. . The method of claim 1, wherein
The controller implementing the line voltage variation prediction algorithm;
An energy storage device equipped with an evacuation energy supply operation method for allowing electric energy stored in an energy storage device to stop at a nearby history by supplying electrical energy to a live line by remote control using various communication means during a power failure.

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