KR101071208B1 - energy storage system of AC method of electric supply - Google Patents

Abstract

The present invention relates to an AC powered energy storage system; An AC-DC converter installed in a substation, the transformer for stepping down AC power supplied from a live wire, and the first to fourth transistors which are opened and closed according to a control signal to convert the stepped input voltage through the transformer into a DC voltage; And an energy storage unit for storing the power passing through the AC-DC converter as electrical energy, and fifth and sixth transistors electrically connected between the AC-DC converter and the energy storage unit and controlled to be opened and closed according to a control signal. And a control unit for detecting the voltage and current of the AC-DC converter and the bidirectional DC-DC converter and controlling the opening and closing of the first to sixth transistors.

According to the present invention, by converting the AC power supplied through the wire into a DC power of the appropriate size to store the electrical energy and when the power supplied to the electric vehicle falls below the reference voltage generated instantaneously through the configuration to provide the stored electrical energy It is possible to respond quickly to the regenerative energy to increase the stability of other systems of the electric vehicle.

 Electric cars, energy, storage

Description

AC energy storage system {energy storage system of AC method of electric supply}

The present invention relates to an AC power supply type energy storage system, and in more detail, an AC power supply type energy supplying and storing electric vehicle regenerative power generated in the AC power supply method and supplying it to the electric vehicle again as necessary. Relates to a storage system.

Recently, in order to save energy as a braking method for braking an electric vehicle, a regenerative braking method, that is, a method of recovering kinetic energy of an electric vehicle as electric energy again when an accelerated electric vehicle decelerates for stopping is adopted.

Such regenerative braking system not only reduces the power consumption of the entire railway system, but also has the advantage of preventing noise problems caused by mechanical braking and wear of brake shoes. to be.

However, in the regenerative braking method, when the accelerated electric vehicle decelerates using the regenerative braking method to stop the vehicle while driving, the motor operates as a generator to perform power generation braking, which generates instantaneous large regenerative power. Such regenerative power not only destabilizes the system by changing the line voltage by applying a large voltage to the line instantaneously, but also causes fluctuations in the line voltage when a trailing train cannot accept the voltage. This can cause malfunction of the trailing train.

On the other hand, in general, the voltage supply method of the electric vehicle is a method of supplying after converting the AC voltage to the DC voltage through the rectifier, the rectifier is connected to the circuit by the forward diode method so that the regenerative power of the electric vehicle is not returned to the power supply side. Therefore, surplus regenerative power that is not consumed on the wire is converted into thermal energy and consumed, or it is cut off by overvoltage of the electric vehicle entering by raising the voltage of the wire, or the regenerative power is consumed by the magnetoresistance because the wire cannot accept the voltage. Sometimes a condition occurs.

Of course, in order to solve this problem, a regenerative inverter is installed in the DC rectifier to convert the line voltage to AC and return it to the power supply or to install a separate storage device for receiving and storing the regenerative power from the line. When the regenerative power generated by the large electric vehicles is returned to the power supply side without being filtered through the inverter, the regenerative power includes harmonics, which may cause unexpected damage to the consumer.

In addition, as an example of using a separate storage device has been presented the Republic of Korea Patent No. 0659366, the regenerative power storage system of the urban railway registered and filed by the applicant.

It is an electric supply path of the electric vehicle and at the same time the path of returning the electricity generated by the regenerative braking when deceleration of the electric vehicle is returned; A gate electrically connected to the wire and capable of intermittent power input / output; An energy storage device connected to the gate and configured to convert and store the supplied electrical energy into kinetic energy and convert the stored kinetic energy into electrical energy by outputting the control signal; A voltage detector electrically connected to the wire to detect the wire voltage; A gate driving circuit driving the gate by a control signal according to the information detected by the voltage detector; And a microprocessor configured to determine a detected voltage of the voltage detector, output a control signal to a gate driving circuit, control an operation of an energy storage device, and control conversion between electric energy and kinetic energy and power input / output.

However, the energy storage device; Due to the mechanical configuration using a flywheel, the noise is high during operation, the volume of the energy storage device itself is large, and the process of converting electrical energy into kinetic energy is inefficient to receive and store instantaneous electrical energy. There was room for improvement such as having a seal.

Accordingly, the present invention is to solve this problem, it is provided in the substation is supplied to the electric vehicle regenerative power generated in the AC power supply method and stored, and provides the energy supply system of the AC power supply system to supply it to the electric vehicle as needed. Its purpose is to.

In addition, the present invention has a higher storage efficiency than the conventional flywheel method to respond quickly to the instantaneous regenerative voltage, it is possible to provide a quick charge and discharge of the regenerative voltage, AC power supply system that can be used semi-permanently. The purpose is.

The present invention to solve this technical problem;

An AC-DC converter installed in a substation, the transformer for stepping down AC power supplied from a live wire, and the first to fourth transistors which are opened and closed according to a control signal to convert the stepped input voltage through the transformer into a DC voltage; And an energy storage unit for storing the power passing through the AC-DC converter as electrical energy, and fifth and sixth transistors electrically connected between the AC-DC converter and the energy storage unit and controlled to be opened and closed according to a control signal. AC power supply method characterized by comprising a bi-directional DC-DC converter, a control unit for detecting the voltage and current of the AC-DC converter and the bi-directional DC-DC converter and controls the opening and closing of the first to sixth transistors. Provide a storage system.

At this time, the energy storage is characterized in that consisting of a supercapacitor (SC).

The energy storage unit may further include an energy storage monitoring unit including a capacitor and measuring a charging voltage of the capacitor and outputting the measured voltage to the controller. When the storage unit is fully charged during the charging mode, the controller turns off the fifth transistor. The control unit turns off the sixth transistor when the charging voltage is less than or equal to the reference voltage while operating in the power supply mode.

The first to sixth transistors may be formed of an insulated gate bipolar transistor (IGBT).

In addition, the AC-DC converter is a single-phase voltage-type PWM converter consisting of first to fourth transistors that are controlled on / off under the control of the controller, the antiparallel diodes are connected to the first to fourth transistors, respectively, It is characterized in that the smoothing capacitor is connected.

와 정수 k₂를 곱하고, 정수 k₁과 입력 전압 v_s의 곱을 더한 값을 전류제어기 G_i(s)의 출력부에 더해 회로임피던스에 의한 입력전류파형의 왜형을 보상하여 2개의 스위칭 캐리어를 통해서 Unipolar 스위칭을 행하여 상기 AC-DC 컨버터의 제1 내지 제4트랜지스터를 스위칭 제어하는 것을 특징으로 한다.At this time, the control unit variance V ^* _dc of the AC-DC DC voltage reference value V of the converter ^* _dc and the actual voltage feedback value V _dc - enter the V _dc in the voltage controller G _v (s) and performs the integral and proportional control; The output of the voltage controller G _v (s) adds the forward compensation term (multiplication of the constant k _L and the load current i _L ) to the load current sudden change to make the magnitude of the input current command value; Multiplying the magnitude value by sin (ωt) in synchronization with the power supply voltage to generate an input current command value i ^* _s to input a deviation from the actual current i _s into the current controller G _i (s); AC circuit impedance at input current i _s

Multiply by and the integer k ₂ and add the product of the integer k ₁ and the input voltage v _s to the output of the current controller G _i (s) to compensate for the distortion of the input current waveform due to the circuit impedance and through the two switching carriers. Unipolar switching is performed to control switching of the first to fourth transistors of the AC-DC converter.

The bidirectional DC-DC converter includes fifth and sixth transistors turned on or off by PWM control of a controller, and the sixth transistor is turned off and the fifth transistor is turned on by a control signal of the controller. When switching, it operates as a buck converter, and when the fifth transistor is turned off and the sixth transistor is switched on, it operates as a boost converter.

According to the present invention, by converting AC power supplied through a wire into DC power of an appropriate size and storing it as electrical energy, when the power supplied to the electric vehicle falls below a reference voltage, the stored electric energy is provided. It is possible to respond quickly to the regenerative energy generated by the configuration, and to prevent other systems of the train from becoming unstable. In particular, the entire urban railway system in the urban railway section where the line voltage fluctuates relatively large due to the short operating period. It has the effect of increasing energy efficiency and stability.

In addition, the present invention, compared to the conventional flywheel-type storage device of the mechanical method to convert the properties of the energy itself even in the rapid supply of electrical energy by storing the electrical energy in response to the instantaneous regenerative voltage and again through the wire There is also the effect of supplying power without.

In addition, the present invention can reduce the weight and volume compared to the storage device using a chemical battery or mechanical properties by using a capacitor, there is an effect that can be installed in various capacities as necessary.

Hereinafter, with reference to the accompanying drawings, the AC power supply energy storage system according to the present invention will be described in detail the features thereof

At this time, Figure 1 is a block diagram of an AC power supply energy storage system according to the present invention, Figure 2 is a block diagram of an AC-DC converter according to the present invention, Figure 3 is a control block diagram of the control unit according to the present invention 4 is a diagram illustrating a switching pattern of an AC-DC converter according to the present invention, FIG. 5 is a configuration diagram of a bidirectional DC-DC converter according to the present invention, and FIG. 6 is a bidirectional DC-DC converter according to the present invention. Fig. 7 is a control block diagram in the charging mode of the bidirectional DC-DC converter according to the present invention, and Fig. 8 is the current flowchart in the discharge mode of the bidirectional DC-DC converter according to the present invention. 9 is a control block diagram in the discharge mode of the bidirectional DC-DC converter according to the present invention.

Referring to FIG. 1, an AC power supply type energy storage system according to the present invention is installed in a substation, and stores electric energy generated when regenerative braking of an electric vehicle is configured to be used as an auxiliary power of an electric vehicle when necessary. do.

In this case, the electric vehicle is supplied with power of a wire through a pantograph (not shown), and the AC power passing through the pantograph and the transformer 10 is converted into DC power through the AC-DC converter 20. In order to control the motor, the motor is driven and controlled through an inverter that converts DC power into AC power.

At this time, between the AC-DC converter 20 and the inverter is provided with an AC power supply energy storage system for efficiently processing the power generated when regenerative braking.

As described above, the AC power supply type energy storage system according to the present invention is installed in a substation, and has a cutoff switch (VCB) for connection with an AC line, which is a path for supplying AC power, and a single-phase AC 50 [kV] AC voltage. A transformer 10 for stepping down the power to a constant input voltage of AC 980 [V], an AC-DC converter 20 capable of quadrant operation for converting the stepped down input voltage through the transformer 10 into a DC voltage; , A bidirectional DC-DC converter 30 capable of bidirectional power flow, an energy storage unit 40 formed of a supercapacitor (SC) for storing energy, the AC-DC converter 20, and a bidirectional DC-DC converter ( 30 is configured to control the controller 50 for monitoring the charging power of the energy storage unit 40.

In this case, the plurality of transistors S1, S2, S3, S4, S5, and S6 constituting the AC-DC converter 20 and the bidirectional DC-DC converter 30 may include an insulated gate bipolar transistor (IGBT). ).

On the other hand, between the pantograph and the transformer 10 is further provided a blocking switch (VCB) for opening and closing the electrical connection with the AC addition. By such a configuration, the controller 50 opens the cutoff switch VCB when an overcurrent is detected.

On the other hand, the energy storage monitoring unit 52 for measuring the voltage and power of the energy storage unit 40 and outputs to the control unit 50 is further provided, the control unit 50 is the energy storage unit ( If 50 is fully buffered, the control is controlled to stop charging. If the voltage input from the energy storage monitoring unit 52 is less than or equal to the reference voltage in the power supply mode, the control is stopped.

Hereinafter, the structure of each part which comprises this invention is demonstrated more concretely.

First, the household wire is a path for supplying AC power to an electric vehicle, and the AC power supplied from the household wire is, for example, AC 25000V and 50000V.

The AC power of such wires is supplied to the bidirectional DC-DC converter 30 through the transformer 10 and the AC-DC converter 20 through the pantograph of the electric vehicle. In this case, the AC-DC converter 20 includes first to fourth transistors S1, S2, S3, and S4 which are turned on or turned off by pulse width modulation (PWM) control. The first to fourth transistors S1, S2, S3, and S4 are switched to convert the DC voltages.

Basically, it is a device that boosts and steps down by oscillating from several tens of ㎑ to hundreds of 에서 internally. Therefore, the AC- The DC converter 20 is provided with a smoothing capacitor C _dc to remove high frequency noise as shown in FIG. 2.

In this case, when the capacity of the smoothing capacitor C _dc is small, the time required for the smoothing capacitor C _dc to charge is not a big problem, but when the smoothing capacitor C _dc has a large capacity, There is a risk of overcurrent because the charge is similar to the shorted state until the amount of current decreases.

의 에너지로 저장되고, 양방향 DC-DC 컨버터(30)의 입력전원으로 사용된다. As shown in FIG. 2, the AC-DC converter 20 steps down the single-phase AC 50 [kV] voltage to the AC 980 [V] through the transformer 10 and converts the stepped-down power supply voltage V _s into the bidirectional DC-. It is supplied to the DC converter 30, and is a single-phase voltage-type PWM converter consisting of first to fourth transistors (S1, S2, S3, S4) controlled on and off under the control of the control unit 50, each of The antiparallel diodes D1, D2, D3, and D4 are connected to the first through fourth transistors S1, S2, S3, and S4. Single-phase AC power is converted into DC power through an AC reactor (L _s ) and a PWM converter to provide a smoothing capacitor (C _dc ).

It is stored as energy and used as the input power of the bidirectional DC-DC converter 30.

At this point, V _s and V _c is the power supply voltage and the converter input voltage, L _s and R _s is the series equivalent resistance and the AC inductor for boosting the input side. Multiple DC-side smoothing capacitors (C _dc ) can be connected in parallel.

The AC-DC converter 20 is controlled according to the control flow of the controller 50 as shown in FIG. 3.

와 정수 k₂를 곱하고, 정수 k₁과 입력 전압 v_s의 곱을 더한 값을 전류제어기 G_i(s)의 출력부에 더해 회로임피던스에 의한 입력전류파형의 왜형을 보상한다. 이렇게 얻어진 최종 출력은 2개의 스위칭 캐리어를 통해서 Unipolar 스위칭을 행하게 된다. 상기 Unipolar 스위칭 방식은 컨버터 입력단이 단락되는 모드가 존재하여 컨버터 입력전압에 0, +V_dc, -V_dc가 나타나게 된다. 이 방식은 Bipolar 스위칭 방식과 비교하여 제어 알고리즘이 복잡하지만 컨버터의 스위칭 주파수를 높일 수 있어 입력전류의 리플을 감소시키는 장점이 있다. First, the deviation of the DC voltage reference value V _dc ^* V _dc ^* and the actual feedback voltage value V _dc - V _dc input to the voltage controller G _v (s) and performs the integral and proportional control. The output of the voltage controller G _v (s) adds the forward compensation term (multiplication of the constant k _L and the load current i _L ) to the load current sudden change to produce the magnitude of the input current command value, which is synchronized with the supply voltage. Multiply by one sin (ωt) to generate the input current setpoint i ^* _s . Input the deviation between the generated current setpoint i ^* _s and the actual current i _s into the current controller G _i (s). Also, AC circuit impedance at input current i _s

And multiplied by a constant k _2, the addition product obtained by adding the value of the constant k ₁ and the input voltage v _s to the output of the current controller G _i (s) compensates for the distortion of the input current waveform of the circuit impedance. The final output thus obtained is subjected to Unipolar switching via two switching carriers. In the unipolar switching method, a mode in which a converter input terminal is shorted is present, so that 0, + V _dc , and -V _dc appear in the converter input voltage. Compared to the bipolar switching method, the control algorithm is more complicated, but the switching frequency of the converter can be increased to reduce the ripple of the input current.

In this case, the relative magnitudes of the DC voltage reference value V ^* _dc and the actual voltage feedback value V _dc are compared. In the case of V ^* _dc > V _dc , power is supplied to the DC load and I _m is positive and i ^* _s is in phase with the supply voltage, but on the contrary, in case of V ^* _dc <V _dc , I _m is negative and i ^* _s is out of phase with the supply voltage. And a current controller G _i (s), output i ^* _s, and, depending on the absolute size of the i _s sign positive or negative of the sine wave of the (-) are amplified in and the value of the, G _i (s) modulated wave You can get a signal.

4 illustrates a relationship between a modulated wave signal, a triangular wave X, and an inverted triangular wave Y, and ON / OFF of the gate signals S1 to S4 corresponding thereto, and a solid line represents the AC-DC converter 20. represents the input AC voltage V _c, the dotted line represents a fundamental component of the AC voltage V _c. The gate signals S1, S2 and the gate signals S3, S4 are alternately turned ON / OFF, and the AC voltage V _c becomes a PWM modulation waveform whose peak value is the same as the DC voltage V _dc . When the power is regenerated from the DC load and supplied to the power source, the flow of power is reversed and the polarity of the modulated wave signal is reversed. The voltage equation of the AC-DC converter 20 seen from the AC input side is as shown in Equation (1) below.

V _s = V _L + V _c ----------- (1)

이며, V_c는 AC-DC 컨버터(20)의 입력전압을 나타낸다. 또한, V_s는 정현파이고 컨버터 입력전압 V_c와 입력전류 i_s의 기본파 성분을 각각 V_c 과 I_s로 나타낸다. 이때, 입력전압 V_s(=V_s·e⁰)를 기준 페이저로 선택하면 기본파 성분에 대한 전압식은 식 (2)와 같다. Where V _s is the AC input voltage,

And V _c represents the input voltage of the AC-DC converter 20. In addition, V _s is a sine wave and the fundamental wave components of the converter input voltage V _c and the input current i _s are represented by V _c and I _s , respectively. At this time, if the input voltage V _s (= V _s e ⁰ ) is selected as the reference pager, the voltage formula for the fundamental wave component is shown in Equation (2).

-----------(2)

-----------(2)

로 표현된다.here,

It is expressed as

The bidirectional DC-DC converter 30 includes fifth and sixth transistors S5 and S6 that are turned on or turned off by pulse width modulation (PWM) control of the controller 50. The fifth and sixth transistors S5 and S6 are switched to convert the DC voltage into a specific DC voltage in both directions.

In this case, the control signals of the fifth and sixth transistors S5 and S6 are applied from the controller 50, and the sixth transistor S6 is turned off by the control signal of the controller 50 and is fifth. When the transistor S5 is switched on, it operates as a buck converter.

On the other hand, if the fifth transistor (S5) is off (Off) and the sixth transistor (S6) is switched on (On) to operate as a boost converter, in order to control the bidirectional power flow with the fifth transistor (S5) It is preferable to control the sixth transistor S6 with a 180 ° phase difference. In this case, the sixth transistor S6 plays the main switching role.

Meanwhile, the bidirectional DC-DC converter 30 may be configured as shown in FIG. 5, which is turned on or turned off by pulse width modulation (PWM) control of the controller 50. DC-DC Buck-Boost chopper composed of seventh and eighth transistors (S7, S8) is a bi-directional current flow, Buck mode is a supercapacitor (SC) of the energy storage unit 40 in the DC Line The boost mode is operated in a mode of discharging to the DC line from the supercapacitor (SC) of the energy storage unit 40. Such a bidirectional DC-DC converter 30 is selectively operated in the charging mode and the power mode.

6 and 7, when the bidirectional DC-DC converter 30 operates in the charging mode under the control of the controller 50, the bidirectional DC-DC converter 30 receives an overcurrent during initial charging of the supercapacitor SC of the energy storage unit 40. A soft start controller 53 for limiting, a current controller 54 for constant current charging, and a duty controller 55 for controlling the duty of PWM. That is, the soft start controller 53 is used for the purpose of limiting the overcurrent flowing into the supercapacitor SC, starting with a minimum pulse of about 1 second to 1.2 seconds at the initial stage of charging in the fully discharged state of the supercapacitor SC. In order to charge the supercapacitor (SC) with a constant current, the current controller 54 amplifies the error value using the PI controller and reduces the error of the steady state through the integral controller. The final value of the current controller 54 controls the duty ratio of the PWM in the duty controller 55.

Meanwhile, according to FIGS. 8 and 9, the bidirectional DC-DC converter 30 operates in the power mode by the power controller 56 under the control of the controller 50 to the supercapacitor SC in the initial charging mode. After the constant voltage is charged, the controller 50 is controlled to the power mode. The power mode operates in the charging mode when the input voltage is higher than the defined reference voltage level, and operates in the discharge mode when the input voltage is lower than the reference voltage level. The error between the defined reference voltage and the input voltage generates a current reference value charged / discharged from the supercapacitor (SC) through the PI controller. This value determines the duty ratio of the PWM in the duty controller 57 via the current controller PI so as to follow the actual current flowing in the supercapacitor SC to the reference current value.

Next, the energy storage unit 40 is configured of a supercapacitor (SC) to store the regenerative power received through the bidirectional DC-DC converter 30. At this time, the storage time is determined according to the capacity of the supercapacitor SC.

In addition, the energy storage monitoring unit 52 measures the voltage and the amount of charge of the supercapacitor SC of the energy storage unit 40, and outputs the same to the controller 50.

The controller 50 may be configured as a microprocessor or a general computer system. In general, AC power provided to vehicles in urban railways of Korea is various, such as AC 25000V, 50000V. This is converted into a reference voltage of DC 980V while passing through the transformer 10 and the AC-DC converter 20.

At this time, the reference voltage for storing the stored power is set larger than the applied voltage, and the reference voltage for supplying the regenerative power again is set smaller than the applied voltage.

For example, when the applied voltage is DC 980V, the power storage reference voltage is set to DC 1200V greater than the applied voltage and the power supply reference voltage is set to DC 700V smaller than the applied voltage, the controller 50 detects the applied voltage. When the DC voltage is 1200V or more, a bidirectional DC-DC converter is output by outputting a control signal for switching the fifth transistor S5 of the bidirectional DC-DC converter 30 to an on state in order to switch to a charging mode. 30) is operated as a Buck Converter.

When the applied voltage falls below 700V, the controller 50 turns off the fifth transistor S5 of the bidirectional DC-DC converter 30 to turn off the sixth transistor S6. By outputting a control signal to the On) state to operate the bidirectional DC-DC converter 30 as a boost converter.

In this case, the controller 50 outputs control signals to the fifth and sixth transistors S5 and S6 of the bidirectional DC-DC converter 30 by a pulse width modulation (PWM) method. Since is a known method, detailed description thereof will be omitted.

In the meantime, when the energy storage monitoring unit 52 outputs that the supercapacitor SC of the energy storage unit 40 is in a buffered state, the controller 50 may be charged even if the applied voltage is greater than or equal to 980 V (storage reference voltage). If the voltage of the energy storage unit 40 measured by the energy storage monitoring unit 52 is 700 V (supply reference voltage) or less, the power storage mode is not switched to the power supply mode.

Hereinafter, an operation example of the AC power supply energy storage system according to the present invention will be described in detail. Electric trains of urban railways are operated by repeating driving and stopping between stop stations along a track.

At this time, the electric vehicle is supplied with an alternating current (AC) voltage through a pantograph and accelerated by driving an electric motor (motor) (not shown) through a transformer 10 and an AC-DC converter 20, After being accelerated to speed, inertia operation is performed by using inertia, and when decelerating, the motor functions as a generator and generates regenerative power by generating power using inertial kinetic energy of the electric vehicle. In order to supply regenerative power, it is divided into general monitoring mode, charging mode, and power supply mode.

In this case, the AC-DC converter 20 is controlled by the controller 50 so that the first to fourth transistors S1 and S2 (S3 and S4) are alternately turned on / off to become a PWM modulated waveform, and a DC load When the power is regenerated from and supplied to the power source, the flow of power is reversed and the polarity of the modulated wave signal is reversed.

When the voltage is applied in this way, the voltage and current detector 51 for detecting the voltage and current of the input terminal and the output terminal of the AC-DC converter 20 and the bidirectional DC-DC converter 30 measures the applied voltage, which is a control unit ( 50) to operate in general monitoring mode.

The general monitoring mode is a mode in which the applied voltage is measured without comparing with the charging or discharging operation of the supercapacitor SC of the energy storage unit 40 and compared with a reference voltage set in the controller 50. That is, when the voltage and current detector 51 measures the applied voltage and outputs the measured value to the controller 50, the controller 50 compares the reference voltage with the reference voltage to determine whether to switch to the charging mode or to the power supply mode. After the determination, the fifth and sixth transistors S5 and S6 of the bidirectional DC-DC converter 30 are turned on / off to operate in the charging mode or the power supply mode.

That is, when the applied voltage input to the controller 50 is equal to or higher than the regenerative power storage reference voltage and the energy storage unit 40 is not in the buffered state, it switches to the charging mode and operates as a Buck Converter, and the applied voltage is applied to the regenerative power supply reference voltage. When falling below and the voltage across the supercapacitor (SC) of the energy storage unit 40 is not less than the reference value is switched to the power supply mode to operate as a boost converter. In this case, the regenerative power storage and supply reference voltage may be selected according to the situation of the peripheral device and the system of the electric vehicle.

At this time, when the charging mode is switched, the bidirectional DC-DC converter 30 operates as a buck converter by switching the fifth transistor S5 to the on state and switching the sixth transistor S6 to the off state. Therefore, the applied voltage is converted into a voltage within the rated voltage of the supercapacitor SC of the energy storage unit 40 and stored in the supercapacitor SC.

On the other hand, if the supercapacitor SC is measured to be buffered by the capacitor monitoring unit 52, the controller 50 outputs a control signal for turning off the fifth transistor S5, terminates the charging mode, and monitors general. The mode will be switched.

When the power supply mode is switched, the bidirectional DC-DC converter 30 operates as a boost converter, so that the power stored in the supercapacitor SC is converted to an appropriate voltage and returned.

At this time, when the voltage of the supercapacitor SC drops below a certain level, the controller 50 outputs a control signal for turning off the fifth transistor S5 and / or the sixth transistor S6 to supply power. To exit and switch to normal monitoring mode.

Although the preferred embodiment of the present invention has been described above, the scope of the present invention is not limited thereto, and the scope of the present invention extends to the scope of the present invention to be substantially equivalent to the embodiment of the present invention. Various modifications can be made by those skilled in the art without departing from the scope of the present invention.

1 is a block diagram of an AC power supply energy storage system according to the present invention,

2 is a block diagram of an AC-DC converter according to the present invention,

3 is a control block diagram of a control unit according to the present invention;

4 is a view showing a switching pattern of the AC-DC converter according to the present invention,

5 is a configuration diagram of a bidirectional DC-DC converter according to the present invention;

6 is a current flow chart in a charging mode of a bidirectional DC-DC converter according to the present invention;

7 is a control block diagram in a charging mode of a bidirectional DC-DC converter according to the present invention;

8 is a current flow chart in the discharge mode of the bidirectional DC-DC converter according to the present invention,

9 is a control block diagram in the discharge mode of the bidirectional DC-DC converter according to the present invention.

DESCRIPTION OF REFERENCE NUMERALS

10: transformer 20: AC-DC converter

30: bidirectional DC-DC converter 40: energy storage unit

50: control unit SC: supercapacitor

S1, S2, S3, S4, S5, S6: Transistor

Claims (7)

A transformer installed in the substation for stepping down AC power supplied from the live wire; A cutoff switch installed between the pantograph and the transformer; An AC-DC converter comprising first to fourth transistors which are opened and closed in response to a control signal to convert the stepped input voltage through the transformer into a DC voltage; An energy storage unit including a supercapacitor (SC) to store power passing through the AC-DC converter as electrical energy; A bidirectional DC-DC converter comprising fifth and sixth transistors electrically connected between the AC-DC converter and the energy storage unit and opened and controlled according to a control signal; And a control unit detecting voltage and current of the AC-DC converter and the bidirectional DC-DC converter and controlling opening and closing of the first to sixth transistors. The energy storage unit is formed of a capacitor, and further includes an energy storage monitoring unit for measuring the charging voltage of the capacitor and outputting it to the controller. When the storage unit is fully charged during the charging mode, the controller turns off the fifth transistor, The controller turns off the sixth transistor when the charging voltage is lower than the reference voltage while operating in the supply mode. The AC-DC converter is a single-phase voltage-type PWM converter consisting of first to fourth transistors controlled on / off under the control of the controller, and an anti-parallel diode is connected to the first to fourth transistors, and a smoothing capacitor Is connected, The controller deviation V _dc ^* of the AC-DC DC voltage reference value V ^* of the converter _dc voltage feedback and the actual value V _dc - V _dc input to the voltage controller G _v (s) and performs the integral and proportional control; The output of the voltage controller G _v (s) adds the forward compensation term (multiplication of the constant k _L and the load current i _L ) to the load current sudden change to make the magnitude of the input current command value; Multiplying the magnitude value by sin (ωt) in synchronization with the power supply voltage to generate an input current command value i ^* _s to input a deviation from the actual current i _s into the current controller G _i (s); AC circuit impedance at input current i _s

Multiply by and the integer k ₂ and add the product of the integer k ₁ and the input voltage v _s to the output of the current controller G _i (s) to compensate for the distortion of the input current waveform due to the circuit impedance and through the two switching carriers. AC power supply type energy storage system, characterized in that for performing switching control of the first to fourth transistors of the AC-DC converter by performing a unipolar switching. delete delete The method of claim 1, And the first to sixth transistors are formed of an insulated gate bipolar transistor (IGBT). delete delete The method of claim 1, The bidirectional DC-DC converter includes fifth and sixth transistors that are turned on or off by PWM control of a controller, and when the sixth transistor is turned off and the fifth transistor is turned on by a control signal of the controller, Operating as a Buck Converter, the AC power supply system, characterized in that when the fifth transistor is off and the sixth transistor is switched on to operate as a Boost Converter.

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