KR20190114596A - Electrical energy storage system with 3 level interleaved charger-discharger - Google Patents

Abstract

Disclosed is an electric energy storage system with a three-level interleaved charger-discharger. According to a specific embodiment of the present invention, when alternating current (AC) power supplied from a system is normal, direct current (DC) power converted by a bidirectional inverter circuit is reduced to charge a battery. When system power is peak or the system power is abnormal, in transferring storage voltage to the bidirectional inverter circuit by boosting the storage voltage of the battery, charging and discharging efficiency of the battery can be increased by using a three-level bidirectional inverter and a three-level interleaved charging and discharging circuit and a neutral point of charging and discharging control is controlled without separately additional devices so as to increase safety of the system.

Description

ELECTRICAL ENERGY STORAGE SYSTEM WITH 3 LEVEL INTERLEAVED CHARGER-DISCHARGER}

The present invention relates to an electrical energy storage system having a three-level interleaved charger and charger, and more particularly, when the AC power supplied from the system is normal, the DC power converted by the bidirectional inverter circuit is reduced to charge the battery, In case of peak power or abnormal grid power, boost the storage voltage of the battery and transfer it to the bi-directional inverter circuit, which can improve the charging efficiency of the battery and control the neutral point during charge / discharge control without any additional device. It's about one technology that can be improved.

A power converting system (PCS) of a general electrical energy storage system charges the battery 50 by converting commercial AC power or renewable power 10 into direct current at light loads or at midnight hours. The grid power supply has the key function of converting the DC power of the battery into AC power and supplying it to the grid during peak times.

These power converters (PCS) enable the use of electrical energy storage systems for demand management, renewable energy output stabilization, emergency power, and hybrids. Power conversion device (PCS) is a power loss, reliability, battery generated in the process of converting AC power to DC power or DC power to AC power according to the configuration of the circuit device constituting the power converter and the control method accordingly It affects the quality of electric energy storage system such as the state of charge and manufacturing cost.

For example, a power converter in which a battery is directly connected to a DC link of a bidirectional inverter has a high conversion efficiency because only a single stage power converter exists, but the bidirectional inverter bears all the charges to control the charging of the battery. Hard limits have been reached.

Therefore, when the battery is charged, the frequency of the grid power is included in the charging current, so that the charging quality is deteriorated. In this case, more than 64 cells of battery are connected in series.

Therefore, the voltage of the DC link and the battery varies widely from about 652 [Vdc] to 864 [Vdc], so that the installation environment of the battery connected to the outside of the power converter as well as the inside of the power converter is set to 700 Vdc. There is a disadvantage in that it causes a big burden in terms of electrical safety, and there is a method of lowering the voltage of the DC link and adding a transformer to the grid input in order to reduce the number of battery input cells to a low voltage range. .

On the other hand, the charge / discharger bears the charge control of the battery, which enables independent and reliable battery charging and improves the charging quality because the frequency of the system power is not included in the charging current when charging the battery. The two-stage power converter provided to accommodate a number (16 to 40 cells) has a disadvantage of low conversion efficiency.

Accordingly, the present applicant can improve charge and discharge efficiency by charging and discharging a battery by using a three-level bidirectional inverter and a three-level interleaved charge / discharge circuit, and control a neutral point during charge / discharge control without additional equipment. I would like to propose a method to secure stability.

The present invention has been made to solve the problems of the prior art, the object of the present invention is to charge the battery by reducing the DC power converted by the bidirectional inverter circuit when the AC power supplied from the system is normal, the system power is In case of peak power or abnormal system power, 3-level bidirectional inverter and 3-level interleaved charge / discharge circuit boost the battery's storage voltage to the bidirectional inverter circuit to improve the charge / discharge efficiency of the battery and It is an object of the present invention to provide an electrical energy storage system having a three-level interleaved charger that can suppress included commercial frequency components and reduce charge ripple current.

In addition, the present invention can stabilize the system because the neutral point control is performed during the charging and discharging without additional equipment, can reduce the cost of electrical energy loss of the user and extend the discharge time of the battery, the light and short It is an object of the present invention to provide an electrical energy storage system having a three-level interleaved charger.

The object of the present invention is not limited to the above-mentioned object, other objects and advantages of the present invention not mentioned can be understood by the following description, will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized by the means and combinations thereof indicated in the claims.

Technical problem of the present invention for achieving the above object,

In the electric energy storage system, when the system power is peaked or the system power is abnormal, the function of converting the power into the alternating current form of the battery into the alternating current and supplying it to the system or the load, and the system power when the system is lightly loaded or at night time A power converter converts an AC power into a DC form and stores the same in a battery. The power converter includes a static switch in series with a breaker to cut off AC power supplied from the outside at high speed when a power failure occurs. Connected input blocking circuit; Based on the three-level switching operation of a plurality of switching elements, it operates as a rectifier for converting a steady state AC power supplied from the outside into a DC form during charging operation of the switching element, and a DC link of the capacitor bank circuit during the discharge operation of the storage voltage of the battery. A bidirectional inverter circuit operating as an inverter that converts a voltage into an alternating current form and transfers the voltage to a grid or a load; A three-level interleaved charge / discharge circuit for reducing the DC power supplied from the bidirectional inverter circuit to charge the battery, and boosting and outputting the DC power of the battery; A capacitor bank circuit for receiving and supplying the DC power of the bidirectional inverter circuit to the three level interleaved circuit for transmission, and for linking and transmitting the DC power of the three level interleaved circuit to the bidirectional inverter circuit; And generating signals for performing charge / discharge control and neutral point control of the input blocking circuit, the three-level bidirectional inverter circuit, and the three-level interleaved charge / discharge circuit, and the overall operation of the electrical energy storage system based on the generated signals. It characterized in that it comprises a control circuit for controlling the.

Preferably, the three-level interleaved charge / discharge circuit includes a first coil L1 connected to the positive terminal of the battery and a second coil L2 connected to the negative terminal of the battery to interoperate with the capacitor bank circuit. An inductor unit configured to charge the battery by reducing the DC link voltage of the capacitor bank circuit or to boost the voltage of the battery to supply the capacitor bank circuit; First and third switching elements Q1 and Q3 are connected in parallel to the right side of the first coil L1 of the inductor unit, and second and fourth switching elements Q2 and Q4 are connected to the right side of the second coil L2. ) Are connected in parallel, respectively, and connect the first to fourth body diodes between the output terminals and the input terminals of the first to fourth switching elements, respectively, to perform charge / discharge control and neutral point control according to the control of the control circuit. It may include a bidirectional switching unit.

Preferably, the capacitor bank circuit has an upper capacitor connected between the input terminal of the first switching element Q1 and the ground N of the bidirectional switching unit, and has a lower end between the output terminal of the ground N and the second switching element Q2. Capacitors may be connected to the battery storage voltage received via the bidirectional switching unit to the DC link to the bidirectional inverter circuit, and the DC power of the bidirectional inverter circuit to the DC link may be provided to the bidirectional switching unit.

Preferably, the control circuit generates and generates a charge PWM signal for charging the battery by reducing the DC link voltage of the capacitor bank circuit based on the charge mode command signal of the power management system generated based on the battery monitoring result of the battery management system. The charge PWM signal to the first and second switching elements, generate a switching signal for turning off the third and fourth switching elements, and transmit the generated switching signal to the third and fourth switching elements. Can be.

Preferably, the charge PWM signal may include a charge offset PWM signal predetermined in the charge PWM signal to switch to the same duty to perform the neutral point control by removing the voltage imbalance of the upper capacitor and the lower capacitor of the capacitor bank circuit, The charging PWM signal supplied to the first switching element is generated by comparing a reference value of a duty value or a DC level with a triangle wave in a control circuit to obtain a PWM pulse waveform in which rising edges and falling edges are generated. A pulse width modulation (PWM) signal in which pulse widths are simultaneously changed from side to side based on a center of a pulse waveform according to a reference value, and a charge PWM signal supplied to the second switching element is a charge PWM supplied to the first switch element. It is a PWM signal having the same pulse width as the signal and having a phase shift of 180 degrees.

Preferably, the control circuit generates a charge PWM signal according to a duty value that varies according to a correlation between the storage voltage Vbat of the battery, the voltage of the lower DC link voltage Vc2 and the upper DC link voltage Vc1. The bidirectional switching unit may include a charge PWM signal of a non-overlapping control circuit when the storage voltage Vbat of the battery satisfies the condition 1, which is less than the DC link voltage Vc1 or Vc2 or the DC link voltage of the capacitor bank circuit. Independent charging mode (Non-crossing mode) for receiving the reduced pressure conversion and the DC link voltage (Vc1 or Vc2) or half of the DC link voltage of the capacitor bank circuit is the charge voltage (Vbat) of the battery 100 When the smaller condition 2 is satisfied, the control unit may include a redundant charging mode in which buck and boost conversion are sequentially performed based on the overlapping charging PWM signal of the control circuit.

Preferably, the independent charging mode of the bidirectional switching unit includes a charging mode 1 in which a DC link voltage Vc1 is charged to a battery when the first switching device Q1 is turned on based on a charging PWM signal of a control circuit, and the first switching device ( Q1) Charging mode 2 which operates in a cyclic mode by a closed circuit which does not include the DC link voltage Vc1 when turned off, and charging mode 3 in which the DC link voltage Vc2 is charged to the battery when the second switching element Q2 is turned on. And a charging mode 2 that operates in a cyclic mode by a closed circuit that does not include the DC link voltage Vc2 when the second switching element Q2 is turned off.

Preferably, the control circuit includes a charge offset PWM signal with an offset weighted value in the independent charging mode and the redundant charging mode in order to secure stability of the neutral point control by omitting the step of determining whether the independent charging mode or the redundant charging mode is omitted. The charging PWM signal may be provided to a selected one of the first switching element and the second switching element of the same bidirectional switching unit.

Preferably, the bidirectional switching unit may be configured to perform neutral point control by varying the discharge amount of the upper and lower capacitors by the charge PWM signal of the control circuit increased by the charge offset PWM signal in the charge mode 1 and the charge mode 3 of the independent charge mode. The bidirectional switching unit may include the charging PWM of the control circuit in which the charging offset PWM signal is increased when the upper DC link voltage Vc1 of the upper capacitor is greater than the lower DC link voltage Vc2 of the lower capacitor in the charging mode 1. The signal may be transmitted to the gate terminal of the first switching element Q1 to perform neutral point control, and in the charging mode 2, the lower DC link voltage Vc2 of the lower capacitor is higher than the upper DC link voltage Vc1 of the upper capacitor. When temporarily increased, the charge PWM signal of the control circuit in which the charge offset PWM signal is increased is transmitted to the gate terminal of the second switching element Q2. Neutral point control can be performed.

Preferably, when the charge voltage of the battery is higher than the DC link voltage Vc1 or Vc2, the control circuit increases the duty of the charge PWM signal of the first switching element Q1 and the charge PWM signal of the second switching element Q2 to increase the charge PWM. A charge PWM signal generating a signal overlapping section is generated and transferred to the bidirectional switching unit, and the bidirectional switching unit capacitor capacitor circuit is generated when a section in which the first switching element Q1 and the second switching element Q2 are simultaneously turned on occurs. Charge mode 4 in which the sum of the DC link voltages Vc1 and Vc2 of Vc1 + Vc2 is reduced through the inductors L1 and L2 and then charged to the battery, and the on state of the first switching element is maintained. While the second switching element Q2 is turned off to form a closed circuit for releasing energy stored in the inductors L1 and L2 in the previous charging mode 4 to form an upper capacitor having a voltage lower than the battery storage voltage Vbat. When a charging mode 1 for boosting the upper DC link voltage to charge the battery and a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time occurs, the DC link voltage Vc1 of the capacitor bank circuit Charge mode 4 in which the sum of Vc2 (Vc1 + Vc2) is decompressed via the inductors L1 and L2 and charged to the battery, and the first switching element Q1 while maintaining the on state of the second switching element. Off to form a closed circuit which releases the energy stored in the inductors L1 and L2 in the previous charging mode 4 to boost the lower DC link voltage of the lower capacitor having a voltage lower than the battery's storage voltage Vbat. Charging mode 3 for charging may be sequentially performed.

Preferably, the bidirectional switching unit may vary the discharge amount of the upper and lower capacitors by the charge PWM signal of the control circuit in which the charge offset PWM signal is increased in the charge mode 1 and the charge mode 3 occurring after the charge mode 4 of the redundant charge mode. Neutral point control may be performed, and the bidirectional switching unit may increase the charge offset PWM signal generated by the control circuit when the upper DC link voltage Vc1 becomes greater than the lower DC link voltage Vc2 when the battery is charged in the redundant charging mode. It is provided to transfer the charge PWM signal to the gate terminal of the first switching element (Q1) to perform the neutral point control, the charge when the lower DC link voltage (Vc2) is greater than the upper DC link voltage (Vc1) when charging the battery in the redundant charging mode In order to perform the neutral point control by transferring the charge PWM signal of the control circuit including the offset PWM signal to the gate terminal of the second switching element Q2. It can be.

Preferably, the control circuit generates a discharge PWM signal to supply DC power to the capacitor bank circuit by discharging the storage voltage of the battery based on the discharge mode command signal of the power management system generated based on the battery monitoring result of the battery management system. And transmit the generated discharge PWM signal to the third and fourth switching elements, generate a switching signal for turning off the first and second switching elements, and transmit the generated switching signal to the first and second switching elements. It may be provided.

The discharge PWM signal supplied to the third switching device is

In the control circuit, PWM is generated by comparing duty values to triangle waves to obtain PWM pulse waveforms in which rising and falling edges are generated, and the pulse width is simultaneously changed from side to side based on the center of the pulse waveform according to the duty value. The PWM signal is a width modulation signal, and the discharge PWM signal supplied to the fourth switching device is a PWM signal having the same pulse width as the charge PWM signal supplied to the third switching device and having a phase shift of 180 degrees.

Preferably, the control circuit generates a discharge PWM signal according to a duty value that is varied by a correlation between the storage voltage Vbat of the battery and the voltage of the lower DC link voltage Vc2 and the upper DC link voltage Vc1. The bidirectional switching unit may include a control circuit that does not overlap when the storage voltage Vbat of the battery satisfies Condition 1 that is greater than 1/2 (350 V) of the DC link voltage Vc1 or Vc2 or the DC link voltage of the capacitor bank circuit. A non-crossing mode in which the storage voltage Vbat of the battery is sequentially reduced and boosted based on the discharge PWM signal and transferred to the capacitor bank circuit, and the storage voltage Vbat of the battery 100 is a DC link voltage. When the condition 2 smaller than the upper DC link voltage Vc1 or the lower DC link voltage Vc1 equal to 1/2 is satisfied, the storage voltage Vbat of the battery is boosted based on the discharge PWM signal of the overlapping control circuit. W redundant discharge mode to pass to the capacitor bank circuit can include (Crossing mode).

Preferably, the independent discharge mode of the bidirectional switching unit includes discharge mode 5 in which the battery is depressurized and charged in the lower capacitor when the third switching element Q3 is turned on based on the discharge PWM signal of the control circuit, and when the third switching element Q3 is turned off. Discharge mode 6 and a fourth switching element in which a circulation circuit including the battery 100 is formed and the energy of the battery is charged by performing a boost (boost) conversion on the upper capacitor 232 and the lower capacitor 234. (Q4) A discharge mode 7 for depressurizing the battery at the time of charging the battery and charging the upper capacitor Vc1, and a circulation circuit including the battery at the time of turning off the fourth switching element Q4 is formed. And discharge mode 6 for charging the lower capacitor in sequence, wherein the control circuit is configured to transfer the upper capacitor and the lower capacitor of the capacitor bank circuit. A discharge PWM signal for switching to the same duty including an offset-weighted discharge offset PWM signal to perform neutral point control to remove the imbalance, wherein the bidirectional switching unit, discharge mode 5 and discharge mode 7 of the independent discharge mode The neutral point control may be performed by varying the charge amount of the upper and lower capacitors based on the discharge PWM signal of the control circuit in which the discharge offset PWM signal is increased.

Preferably, the bidirectional switching unit discharges the battery voltage by the third switching element Q3 in the discharge mode 5 during the independent discharge to charge the lower capacitor so that the upper DC link voltage Vc1 of the upper capacitor is lower than the lower DC of the lower capacitor. When the link voltage Vc2 is greater than the discharge voltage, the discharge PWM signal of the control circuit including the discharge offset PWM signal is transmitted to the gate terminal of the third switching element Q3 to perform neutral point control, and in the discharge mode 7, the fourth switching element Q4. The discharge PWM signal of the control circuit including the discharge offset PWM signal when the lower DC link voltage Vc2 of the lower capacitor becomes larger than the upper DC link voltage Vc1 of the upper capacitor when discharging the battery voltage to charge the upper capacitor. May be transferred to the gate terminal of the fourth switching element Q4 to perform neutral point control.

Preferably, in the redundant discharge mode of the bidirectional switching unit, when a section in which the third switching element Q3 and the fourth switching element Q4 are turned on at the same time occurs, the boost voltage is increased to the inductors L1 and L2 based on the storage voltage Vbat of the battery. The energy stored in the inductors L1 and L2 in the previous discharge mode 8 is turned off in the lower capacitor by turning off the fourth switching element Q4 while maintaining the discharge mode 8 where the energy is charged and the on state of the third switching element. When the discharge mode 5 to be charged and a section in which the third switching element Q3 and the fourth switching element Q4 are turned on at the same time occur, boost energy is charged to the inductors L1 and L2 based on the storage voltage Vbat of the battery. The discharge mode 8 and the fourth switching device while the on state of the fourth switching device is maintained as it is, the third switching device Q3 is turned off to charge the upper capacitor with the energy stored in the inductors L1 and L2 in the previous discharge mode 8. Mode 7 Are sequentially performed, and the bidirectional switching unit changes the charge amount of the upper and lower capacitors based on the discharge PWM signal of the control circuit in which the discharge offset PWM signal is increased in the discharge mode 5 and the discharge mode 7 after the discharge mode 8 during the overlap discharge. Neutral point control can be performed, and in the discharge mode 5 during the overlapping discharge, the upper DC link voltage Vc1 of the upper capacitor is lower than the lower DC in discharging the storage voltage of the battery by the third switching element Q3 to charge the lower capacitor. When the link voltage Vc2 is greater than the discharge voltage, the discharge PWM signal of the control circuit including the discharge offset PWM signal is transmitted to the gate terminal of the third switching element Q3 to perform neutral point control, and the fourth switching element Q4 in the discharge mode 7 is performed. The lower DC link voltage (Vc2) of the lower capacitor is the upper capacitor when charging the upper capacitor by discharging the storage voltage of the battery. When the upper DC link voltage Vc1 of the gate is greater than the discharge PWM signal of the control circuit including the discharge offset PWM signal may be transmitted to the gate terminal of the fourth switching element Q4 to perform neutral point control.

According to the present invention, when the AC power supplied from the system is normal, the DC power converted by the bidirectional inverter circuit is reduced to charge the battery, and when the system power is peak or the system power is abnormal, the battery is boosted by boosting the storage voltage of the battery. In the transfer to the inverter circuit, it is possible to improve the charge and discharge efficiency of the battery by using a three-level bidirectional inverter and a three-level interleaved charge and discharge circuit.

In addition, since the neutral point control is performed during charging and discharging without additional equipment according to the present invention, it is possible to stabilize the system, reduce the electric energy loss cost of the user, extend the discharge time of the battery, and reduce the energy of the electric energy storage system. It can be simplified.

The following drawings attached in this specification are illustrative of the preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.
1 is a view showing a schematic configuration of an electrical energy storage system to which an embodiment of the present invention is applied.
2 is a view showing a detailed configuration of a power conversion device of the electrical energy storage system according to an embodiment of the present invention.
3 is a diagram illustrating an operation state of the three-level bidirectional charging and discharging circuit of the power conversion device of the electrical energy storage system according to an embodiment of the present invention.
4 is a view showing the output waveform of each part when the three-level bidirectional charging and discharging circuit of the power conversion device of the electrical energy storage system according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating an operating state of a three-level bidirectional charging / discharging circuit of the power converter of the electrical energy storage system according to an exemplary embodiment of the present invention. FIG.
FIG. 6 is a diagram illustrating output waveforms of respective units during discharge of a three-level bidirectional charging / discharging circuit of a power conversion device of an electrical energy storage system according to an exemplary embodiment of the present invention.

Hereinafter, with reference to the drawings will be described embodiments of the present invention in more detail.

Advantages and features of the present invention, and methods of achieving them will be apparent with reference to the embodiments described below in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms, and only the embodiments are to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims.

Terms used herein will be briefly described and the present invention will be described in detail.

The terms used in the present invention have been selected as widely used general terms as possible in consideration of the functions in the present invention, but this may vary according to the intention or precedent of the person skilled in the art, the emergence of new technologies, and the like. In addition, in certain cases, there is also a term arbitrarily selected by the applicant, in which case the meaning will be described in detail in the description of the invention. Therefore, the terms used in the present invention should be defined based on the meanings of the terms and the contents throughout the present invention, rather than the names of the simple terms.

When any part of the specification is to "include" any component, this means that it may further include other components, except to exclude other components unless otherwise stated. In addition, the term "part" as used herein refers to a hardware component, such as software, FPGA or ASIC, and "part" plays certain roles. However, "part" is not meant to be limited to software or hardware. The “unit” may be configured to be in an addressable storage medium and may be configured to play one or more processors.

Thus, as an example, a "part" refers to components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, Subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays and variables. The functionality provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts".

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention.

The present invention stores the electrical energy in the battery using the grid power at light load or the late-night time when the grid power using the commercial power generation or renewable power generation system is a grid or In the electric energy storage system that transfers to the load, when the AC power supplied from the system is normal, the DC power converted by the bidirectional inverter circuit is reduced to charge the battery, and when the system power is peaked or the system power is abnormal, It is based on a three-level interleaved charge-discharge circuit that boosts the storage voltage to pass to the bidirectional inverter circuit. Accordingly, the present invention can improve the charging and discharging efficiency of the battery by using a three-level bidirectional inverter and a three-level interleaved charge and discharge circuit, and obtain a result that can control the neutral point during charge and discharge control without any additional device. Technology.

Hereinafter, a power according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a schematic configuration of an electrical energy storage system according to an embodiment of the present invention, Figure 2 is a view showing a detailed circuit of the power converter shown in Figure 1, Figure 3 is shown in Figure 2 FIG. 4 is a diagram illustrating a process of converting an AC power supplied from the outside of a three-level interleaved charge / discharge circuit to a DC power based on a bidirectional inverter circuit to charge a battery. FIG. 4 is an output waveform of each part shown in FIG. 3. Is shown. 1 to 4, an electric energy storage system includes a battery 100, a power control system (PCS) 200, a battery management system 300, and a power management system. (PMS, Power Management System: 400).

Here, the power converter 200 converts the stored DC power of the battery 100 into an alternating current form when the system power is peak or the system power is abnormal under the control of the power management system 400 to supply to the system or load. The function and the system power to convert the AC power of the system to the DC form at light loads or late night time to perform the function of storing in the battery 100.

In addition, the battery management system 300 monitors, controls, and protects an operation state (voltage, current, temperature, state of charge (SOC), life state (SOH), etc.) of the battery.

Here, the state of charge (SOC) of the battery 100 during operation of the battery is an indicator indicating the state of the amount of power charged or discharged with respect to the rated kWh capacity of the battery, the life state (SOH) is a cycle for the rated kWh capacity of the battery When the driving is performed, it is an index indicating the number of driving cycles or the remaining cycles of the battery 100.

On the other hand, the power management system (PMS: 400) of the electric energy storage device of the present invention monitors the operating states of the power conversion device 200, the battery 100, and the battery management system 300 which are main components of the electric energy storage system. It effectively manages the electrical energy storage system according to the load requirements.

In addition, the power management system 400 has a communication unit for transmitting the operating state of the electric energy storage system to the energy management system (EMS, 500) that is the upper system of the electric energy storage system. Accordingly, the energy management system performs a function of efficiently managing energy of the system power by comprehensively monitoring various customer load characteristics and operating characteristics of a distributed power source such as an electric energy storage system.

In the electrical energy storage system to which the present invention is applied, the storage voltage Vbat of the battery 100 is converted into an AC form and supplied to a system or a load, or the AC power is converted into a DC form and stored in the battery 100, or alternating current. A series of processes for supplying power to a load can be understood by those skilled in the art related to the embodiments of the present invention.

As shown in FIG. 2, the power converter 200 includes a three-level interleaved charge / discharge circuit 210, a capacitor bank circuit 230, a three-level bidirectional inverter circuit 250, an input disconnect circuit 270, And a control circuit 290.

Here, the three-level interleaved charge / discharge circuit 210 depressurizes the DC power supplied to the capacitor bank circuit 230 by the bidirectional inverter circuit 230 to charge the battery 100, thereby supplying the DC power of the battery 100. It is provided to perform the function of boosting and transferring to the capacitor bank circuit 230, the three-level interleaved charge and discharge circuit 210 may include an inductor unit 211 and a bidirectional switching unit 213.

The inductor unit 211 is formed of the first coil L1 and the battery 100 to which the positive terminal of the battery 100 and the first and third switching elements Q1 and Q3 of the bidirectional switching unit 213 are connected ( And a second coil L2 connected to the second and fourth switching elements Q2 and Q4 of the bidirectional switching unit 213 and the bipolar switching unit 213 of the capacitor bank circuit 230. The battery is charged by reducing the voltage or boosting and converting the voltage of the battery 100 to the capacitor bank circuit 230.

 The first and third switching elements Q1 and Q3 of the bidirectional switching unit 213 are connected in parallel to the right side of the first coil L1, respectively, and the second and fourth switching elements Q2 and Q4 are formed in the first direction. Each of the two coils L2 is connected in parallel to each other, and the output terminal of the third switching element Q3 and the input terminal of the fourth switching element Q4 have a structure connected to the ground N.

In the capacitor bank circuit 230, the upper capacitor 232 is connected between the input terminal of the first switching element Q1 of the bidirectional switching unit 213 and the ground N, and the ground N and the second switching element ( The lower capacitor 234 is connected between the output terminals of Q2), receives the DC power of the three-level bidirectional inverter circuit 250, links it to the three-level interleaved circuit 210, and transfers it to the three-level interleaved circuit 210. The DC power of 210 is linked to the three-level bidirectional inverter circuit 250 to transfer the same.

Meanwhile, the three-level bidirectional inverter circuit 250 includes a plurality of switching elements T1 connected to the input terminal of the upper capacitor 232, the ground N, and the output terminal of the lower capacitor 234 of the capacitor bank circuit 230, respectively. ~ T6, T1 '~ T6'), according to the three-level switching operation of the plurality of switching elements (T1 ~ T6, T1 '~ T6') the three-level bidirectional inverter circuit 250 is a battery (100) It operates as a rectifier for converting the AC power of the normal state supplied from the outside in the form of direct current during the charging operation of the system and converts the DC link voltage of the capacitor bank circuit 230 into the alternating current form during the discharge operation of the battery 100. It acts as an inverter that transfers load. Based on the plurality of switching elements T1 to T6 and T1 'to T6' of the three-level bidirectional inverter circuit 250, the battery 100 operates as a three-level rectifier during a charging operation and a three-level inverter during a discharge operation. A series of processes operating as is filed and registered in the Patent Registration No. 10-1627505 by the present applicant, a detailed description thereof will be omitted.

In addition, the input blocking circuit 270 is provided in a structure in which a static switch 271 is connected in series with a breaker in order to add an emergency power function of the electric energy storage system. In addition, the three-level interleaved circuit 210 boosts the storage voltage of the battery and transfers it to the capacitor bank circuit 230, and the output voltage of the direct current form of the capacitor bank circuit 230 is transmitted to the bidirectional inverter circuit 270. The bidirectional inverter circuit 270 supplies an output voltage of an alternating current type to a load connected to the terminals R, S, T, and N (not shown).

Meanwhile, when the charging or discharging mode is determined based on the power management system 400 receiving the battery state information of the battery management system 300, the control circuit 290 is a three-level interleaved charging circuit according to the determined charging or discharging mode. The first to fourth switching elements Q1 to Q4 of 210, the plurality of switching elements T1 to T6 and T1 ′ to T6 ′ of the three-level bidirectional inverter circuit 250, and an input blocking circuit ( Signals for controlling the operation of the circuit breaker 271 of 270 is generated and transmitted, whereby the power converter 200 is provided to perform a charge mode or a discharge mode of the battery 100.

In addition, the power converter 200 shown in FIG. 2 includes a plurality of first to fourth switching elements Q1 to Q4 of the three-level interleaved charging circuit 210 and a plurality of three-level bidirectional inverter circuits 250. Only the components related to the present embodiment are shown for performing the control of the switching elements T1 to T6 and T1 'to T6' and the breaker 271 of the input blocking circuit 270. Thus, in addition to the components shown in FIG. 2, other general purpose components, for example, a charge-discharge gate gate drive, a three-level bidirectional inverter circuit for controlling the operation of the first to fourth switching elements Q1 to Q4. An inverter gate driver for controlling the operation of the plurality of switching elements T1 to T6 and T1 'to T6' of the 250, and an input blocking circuit interface unit for controlling the interruption of the breaker 271 of the input blocking circuit 270. It can be understood by those of ordinary skill in the art related to the present embodiment that the etc. may be further included.

The capacitor bank charged from the 3-level bidirectional inverter circuit 250 in the three-level interleaved charge / discharge circuit 210 and the capacitor bank circuit 230 according to the charging or discharging mode set by the control circuit 290 will be charged below. A series of processes of charging the battery by depressurizing the DC power of the circuit 230, boosting the storage voltage of the battery via the capacitor bank circuit 230, and transferring the voltage to the system or the load will be described.

First, the DC voltage in which the AC power is rectified in the three-level bidirectional inverter circuit 250 is stored in the upper capacitor 232 and the lower capacitor 234 of the capacitor bank circuit 230, and the stored DC link voltage Vc1. ) Vc2 is transmitted to the three-level interleaved charge and discharge circuit 210.

Thereafter, when the charge mode command signal of the battery 100 is transmitted to the control circuit 290 of the power converter 200 in the power management system 400, the control circuit 290 is a three-level interleaved circuit 210. The switching signal for turning off the third switching element Q3 and the fourth switching element Q4 of the bidirectional switching unit 213 of the bidirectional switching unit 213 and charging the first switching element Q1 and the second switching element Q2, respectively. The PWM signal is sent, and the DC link voltage of the capacitor bank circuit 230 is decompressed to charge the battery 100.

That is, in the charging mode of the battery 100, the first switching element Q1 and the second switching element Q2, the third switching element Q3, and the fourth switching element Q4 of the bidirectional switching unit 213 are respectively provided. Charging of the battery 100 is performed based on the connected body diode.

Meanwhile, in the charging mode, two charging PWMs having a phase shift of 180 degrees and switching with the same duty are supplied to the gate ends of the first switching element Q1 and the second switching element Q2, respectively, and the duty value is increased. If the value is less than 0.5, the operation is performed in an independent charging mode in which the two charging PWMs do not overlap. When the duty value is greater than 0.5, the operation is in the redundant charging mode in which the two charging PWMs overlap. In this case, the control circuit 290 includes a charge offset PWM signal in the two charge PWMs switching to the same duty to remove the voltage imbalance between the upper capacitor 232 and the lower capacitor 234 of the capacitor bank circuit 230 during charging. Can be.

Meanwhile, when the discharge mode command signal of the battery 100 is transmitted to the control circuit 290 of the power converter 200 in the power management system 400, the control circuit 290 is a three-level interleaved circuit 210. A switching signal for turning off the first switching element Q1 and the second switching element Q2 of the bidirectional switching unit 213 of the bidirectional switching unit 213, and discharging the third switching element Q3 and the fourth switching element Q4, respectively. The PWM signal is transmitted, and the battery voltage charged in the battery 100 is boosted and transferred to the DC link voltage of the capacitor bank circuit 230.

That is, in the discharge mode of the battery 100, the third switching element Q3 and the fourth switching element Q4, the first switching element Q1, and the second switching element Q2 of the bidirectional switching unit 213 are respectively provided. Discharge of the battery 100 is performed based on the connected body diode.

Meanwhile, in the discharge mode, two discharge PWMs having a phase shift of 180 degrees and switching with the same duty are supplied to the gate ends of the third switching element Q3 and the fourth switching element Q4, respectively, and the duty value is increased. If it is 0.5 or less, it operates in an independent discharge mode in which two discharge PWMs do not overlap. If the duty value is greater than 0.5, it operates in an overlapping discharge mode in which a section in which two discharge PWMs overlap. At this time, the control circuit 290 includes a discharge offset PWM signal in the two discharge PWMs switching to the same duty to eliminate the voltage imbalance between the upper capacitor 232 and the lower capacitor 234 of the capacitor bank circuit 230 during discharge. Can be.

Necessity of Neutral Point Control

Compared to the conventional two-level power converter, the three-level power converter has superior efficiency characteristics due to the neutral point clamping effect, and the inductance value of the filter reactor can be reduced by the frequency multiplying effect and the electromagnetic wave generation amount is reduced by about 50%. Have The increase in efficiency, inductance and reduction of electromagnetic waves have the effect of lowering the cost of the device and improving reliability. In addition, the efficiency of the three-level power converter has the effect of reducing the operating cost by reducing the power loss during operation.

However, the transformerless two-level and three-level power converters using neutral wires have nonuniform impedances of the upper capacitor 232 and the lower capacitor 234 constituting the DC link and non-uniformity of the PWM signal applied to the semiconductor device. Due to the characteristics, the DC voltages stored in the upper capacitor 232 and the lower capacitor 234 may not match. If the bidirectional inverter converts the DC voltage stored in the upper capacitor 232 and the lower capacitor 234 having the mismatched voltage into an AC voltage, the DC component is included in the output of the bidirectional inverter.

However, when the output of a bidirectional inverter containing a DC component is connected to a grid or a load, noise and overheating occur in transformers and reactors installed on the grid and the load side, which is an important factor that seriously degrades the reliability of the bidirectional inverter, grid, and load. Becomes

In addition, when the voltage of the upper capacitor 232 and the lower capacitor 234 does not match when the battery 100 is charged using the bidirectional switching unit 213 of the three-level interleaved circuit 210, the charging current is charged for one period of the charging PWM. Becomes non-uniform, degrading the charging quality of the battery.

On the other hand, in the three-level power converter, the number of semiconductor elements and driver circuits for driving the semiconductor is generally twice as large as that of the two-level, which further increases the nonuniformity of the PWM signal.

On the other hand, when the bidirectional inverter acts as a rectifier to supply DC voltage to the DC link capacitor and at the same time a voltage mismatch occurs between the upper and lower DC link capacitors due to some factor in the process of charging the battery by the bidirectional charger and the bidirectional inverter PWM. By adding an offset to it, it is possible to eliminate the mismatch of voltages of the upper and lower DC link capacitors, but there is a problem in that harmonics are generated at the AC input terminal of the bidirectional inverter.

In addition, when the bidirectional inverter operates as a current source or voltage source inverter and converts the DC voltage charged in the DC link capacitor into an AC voltage to supply power to the system or load, the bidirectional inverter adds an offset to the PWM signal of the bidirectional inverter to provide an upper and lower DC link. Although the mismatch of the capacitor voltage can be eliminated, there is a problem that harmonics are generated at the AC input terminal of the bidirectional inverter.

In order to solve the problem as described above, it is possible to eliminate the mismatch between the voltage of the upper and lower DC link capacitor by adding a neutral point controller that performs a separate neutral point control, but the circuit is complicated and bulky.

Accordingly, the electric energy storage system of the present invention provides a means for performing neutral point control using only a three-level bidirectional charger without adding a separate neutral point controller.

<Charge mode of 3-level interleaved charge / discharge circuit>

A direct current power of the capacitor bank circuit 230 in the third level interleaved charging circuit 210 is transmitted to the charging PWM signal to a series of process of the charging operation to the battery 100, see Figs. 3 and 4 in more detail The explanation is as follows.

3A to 3D are circuit diagrams illustrating an operation process for each mode during the charging operation of the battery 100 based on the three-level interleaved charge / discharge circuit 210 shown in FIG. 2, and FIG. Figure 3 shows the output waveform for each mode.

Here, the charging PWM signal supplied to the first switch element Q1 is a method of obtaining a PWM pulse waveform in which the rising edge and the falling edge are generated by comparing the reference of the DC level with the triangular wave in the control circuit 290. Accordingly, the pulse width is a PWM (Pulse Width Modulation) signal in which the pulse widths are simultaneously changed from side to side with respect to the center of the pulse waveform, and the charge PWM signal supplied to the second switch element Q2 is supplied to the first switch element Q1. The PWM signal has the same pulse width as the charge PWM signal and has a phase shift of 180 degrees.

Accordingly, there are four switch combinations that can be generated by the first switch element Q1 and the second switching element Q2, and the charging mode of the battery 100 is the first switch element Q1 and the second switching element Q2. Including a charging mode (Crossing mode) when the charge PWM signal supplied to the non-overlapping mode (Non-crossing mode) is not superimposed, the independent charging mode performs a buck function, The redundant charging mode may be provided to sequentially perform decompression (buck) and boost.

Meanwhile, the DC link voltage Vc1 of the upper capacitor or the DC link voltage Vc2 of the lower capacitor is 1/2 of the voltage between DC (+) and DC (-) and is maintained at the same value in a normal state. The storage voltage Vbat of) varies from a low value to a high value during charging.

<Charging operation in the independent charging mode>

In the energy storage device of the present invention, for example, a 12V lead acid battery may be a battery input system in which 16, 20, 30 and 40 cells are connected in series. The independent charging mode and the redundant charging mode are both generated by the correlation between the DC link voltage Vc1 or Vc2. Therefore, the description of the charging operation in the 16 cells, 20 cells and 40 cells that generates only one of the independent charging mode or the redundant charging mode can be omitted.

Since the discharge end voltage of 12V lead acid battery is generally 10.2V per cell, the lowest voltage of battery input is 306V in a system with 30 cells connected in series, and the full charge voltage is generally 13.5V per cell. The voltage can be seen as 405V. Therefore, the battery input voltage may vary between 306V and 405V depending on the state of charge or discharge of the battery.

After that, when operating in the discharge mode in the previous operation process when the storage voltage of the battery completes the discharge to the lowest voltage (306V) and is switched to the charging mode, the control circuit 290 is a three-level bidirectional inverter 250 PFC ( It operates as a rectifier to convert AC input power to DC power to charge the DC link capacitor between DC (+) and DC (-) to full charge voltage (700V).

Meanwhile, in the steady state, the DC link voltage Vc1 of the upper capacitor 232 or the DC link voltage Vc2 of the lower capacitor 234 is 1/2 (350V) of the voltage between DC (+) and DC (-). Suppose you are running at about the same value.

Subsequently, the control circuit 290 supplies a charging PWM signal to the first switch element Q1 and the second switching element Q2 of the three-level interleaved charge / discharge circuit 210.

Here, the charge PWM signal generated from the control circuit 290 starts at a state where the initial duty is zero until the control state becomes normal and increases. Has characteristics.

On the other hand, the battery, which has been lowered to the lowest voltage (306V), starts to recharge until the charge voltage of the battery is equal to 350V, which is the voltage of the upper capacitor (Vc1) or the voltage of the lower capacitor (Vc2). In order for the discharge circuit 210 to operate in an independent charging mode, the control circuit 290 generates a charge PWM signal in which the inductor value and the switching frequency are set to maintain the duty of the two charge PWM signals within a range of 0 to 50%. To the first switch element Q1 and the second switching element Q2.

Accordingly, the bidirectional switching unit 230 starts charging at the lowest voltage 306V of the battery based on the charge PWM signal set by the set inductor value and the switching frequency, and thus the charge voltages are DC link DC (+) and DC. The voltage is operated in the independent charging mode until 350V, which is 1/2 of the negative voltage, and the two charging PWM signals supplied to the first switch element Q1 and the second switching element Q2 do not overlap.

That is, the independent charging mode is performed when the storage voltage Vbat of the battery satisfies Condition 1 which is less than 1/2 of the DC link voltage Vc1 or Vc2 or the capacitor bank voltage, and the three-level interleaved charging is performed in the independent charging mode. The discharge circuit 210 is repeatedly performed in sequence of charging mode 1 → charging mode 2 → charging mode 3 → charging mode 2.

Referring to the operation of the charging mode 2 in the charging mode 1, as shown in Figure 3 (a), when the first switching element (Q1) the DC link voltage (Vc1) is charged in the battery 100 As shown in (b), when the first switching element Q1 is turned off, a closed circuit is formed that does not include the DC link voltage Vc1 so that the bidirectional switching unit 213 operates in a cyclic mode and thus the bidirectional switching unit ( 213 is operated as a decompression (buck, buck) converter. The principle of operating in the charging mode 3 shown in (c) to the charging mode 2 shown in (b) is the same.

At this time, during the independent charging mode, the voltage equation and output voltage Vbat of the first coil L1 and the second coil L2 of the inductor unit 211 in the charging mode 1 to the charging mode 2 are represented by the following equations (1) and ( 2), and in the charging mode 3 to the charging mode 2, the voltage equation and the output voltage of the first coil L1 and the second coil L2 satisfy equations (3) and (4). In Equation (2), the charging voltage Vbat of the battery is determined in proportion to the DC link voltage Vc1 and the duty ratio d _Q1 , and in Equation (4) depends on the DC link voltage Vc2 and the duty ratio d _Q2 . It can be seen that it is determined by.

.. 식 1

.. Equation 1

.. 식 2

.. Equation 2

.. 식 3

.. Equation 3

.. 식 4

.. Equation 4

<Neutral Point Control in Independent Charge Mode>

Meanwhile, if the balance between the voltage Vc1 of the upper capacitor 232 and the voltage Vc2 of the lower capacitor 234 is broken for some reason during charging, an overvoltage may be applied to the upper capacitor or the lower capacitor to cause capacitor burnout. Non-uniform charge current for one period of PWM can degrade the charge quality of the battery.

Accordingly, in the independent charging mode 1 in which the first switching element Q1 charges the battery by using the upper capacitor 232, the upper DC link voltage Vc1 of the upper capacitor 232 is caused by the lower capacitor 234. When temporarily greater than the lower DC link voltage Vc2, the control circuit 290 transmits the charging PWM signal having the charging offset PWM signal increased to the first switching device Q1 to the gate terminal of the first switching device Q1. The bidirectional switching unit 213 performs neutral point control. That is, the discharge amount of the upper DC link voltage Vc1 of the upper capacitor 232 is greater than the discharge amount of the lower DC link voltage Vc2 of the lower capacitor 234 based on the charging PWM signal including the increased charge offset PWM signal. As a result, the voltage difference between the upper DC link voltage Vc1 and the lower DC link voltage Vc2 is eliminated.

In addition, in the independent charging mode 3 in which the second switching element Q2 uses the lower capacitor 234 to charge the battery, the lower DC link voltage Vc2 of the lower capacitor 234 may be caused by the lower capacitor 234 of the upper capacitor 232. When temporarily larger than the upper DC link voltage Vc1, the control circuit 290 transmits the charging PWM signal having the increased charging offset PWM signal to the gate terminal of the second switching element Q2, and thus the bidirectional switching unit 213 Perform neutral point control. That is, the discharge amount of the lower DC link voltage Vc2 of the lower capacitor 234 is greater than the discharge amount of the upper DC link voltage Vc1 of the upper capacitor 232 based on the charged PWM signal including the increased charge offset PWM signal. The voltage difference between the upper and lower capacitors 232 and 234 is reduced until the DC link voltage Vc2 of the lower capacitor 234 becomes equal to the upper DC link voltage Vc1.

<Charging operation in redundant charging mode>

On the other hand, when the charge voltage of the battery that starts recharging at the initial minimum voltage (306V) is higher than the DC link voltage Vc1 (350V) or Vc2 (350V), the battery 100 can no longer be charged in the independent charging mode. 290 may increase the duty of the charging PWM signal of the first switching device Q1 and the charging PWM signal of the second switching device Q2 by 50% or more to generate a charging PWM signal in which an overlapping section of the two charging PWM signals occurs. Transfer to the switching unit 213, the bi-directional switching unit 213 operates in a redundant charging mode.

Accordingly, the three level interleaved charge / discharge circuit 210 may charge the voltage of the battery 100 to a maximum voltage (405V) in a 30-cell series system using the redundant charging mode.

That is, the redundant charging mode is a three-level interleaved charge / discharge circuit when the DC link voltage Vc1 or Vc2 or one half of the capacitor bank voltage satisfies condition 2 smaller than the charge voltage Vbat of the battery 100. As a mode performed at 210, the charging mode 4 → charging mode 1 → charging mode 4 → charging mode 3 illustrated in FIG. 3 is sequentially and repeatedly performed.

That is, when a section in which the first switching element Q1 and the second switching element Q2 are turned on simultaneously in the charging mode 4 occurs, the sum Vc1 of the DC link voltages Vc1 and Vc2 of the capacitor bank circuit 230 occurs. + Vc2 is charged to the battery 100 by converting a decompression (buck) through the inductors L1 and L2.

Thereafter, in the charging mode 1, the ON switching state of the first switching device Q1 is maintained as it is and the second switching device Q2 is turned off by the charging PWM signal of the control circuit 290. In the charging mode 4 of the to form a closed circuit to release the energy stored in the inductors (L1, L2) to switch to the cyclic mode.

Accordingly, the energy of the upper capacitor 232 having a voltage lower than the storage voltage Vbat of the battery 100 is supplied to the battery 100 through the circulating current due to the closed circuit of the cyclic mode occurring in the charging mode 1, thereby interleaving the three levels. The decharge / discharge circuit 210 may include boosting conversion in the cyclic mode operation of the charge mode 1 that occurs after the decompression charging in the charge mode 4. Thereafter, the principle of operating in the charging mode 3 in the charging mode 4 is the same.

At this time, during the redundant charging mode, the voltage equation and output voltage Vbat of the first coil L1 and the second coil L2 of the inductor unit 211 in the charging mode 4 → charging mode 1 are represented by the following equations (5) and ( 6), and the voltage equation and the output voltage of the first coil L1 and the second coil L2 satisfy the following equations (7) and (8) during the charging mode 4 → charging mode 3 operation.

In the charging mode 4 → charging mode 1 during the redundant charging mode, the charging voltage Vbat of the battery 100 is the duty ratio d _Q1 to the sum (Vc1 + Vc2) of the upper and lower DC link voltages in Equation (6). _{/ Q2)} can result in the egg is determined as the value obtained by adding the result of multiplying the duty ratio (d _{'Q1 / Q2)} to the DC link voltage (Vc1), multiplied by the top.

In addition, in the charging mode 4 → charging mode 3 during the redundant charging mode, the charging voltage Vbat of the battery 100 is equal to the duty ratio d _Q1 to the sum (Vc1 + Vc2) of the upper and lower DC link voltages in Equation (8). a DC link voltage (Vc2) to the bottom of the result of multiplying a _{/ Q2)} by adding the result of multiplying the duty ratio (d _{'Q1 / Q2)} can be seen as determined by the derived value.

.. 식 5

.. Equation 5

.. 식 6

.. Equation 6

.. 식 7

.. Equation 7

.. 식 8

.. Equation 8

On the other hand, energy is transferred from the upper capacitor 232 to the battery 100 when the first switching device Q1 is turned on in the independent charging mode, and energy is transferred from the lower capacitor 234 when the second switching device Q2 is turned on. The energy is transferred from the upper capacitor 232 and the lower capacitor 234 at the same time in the section where the first switching element Q1 and the second switching element Q2 are simultaneously turned on in the redundant charging mode. 100, the first switching element Q1 or the second switching element Q2 transfers energy to the battery 100 by the upper capacitor 232 alone or the lower capacitor 234 alone when the first switching element Q1 or the second switching element Q2 is turned off. You can see this.

However, although the state of the first switching element Q1 of the charging mode 1 of the independent charging mode and the charging mode 1 of the redundant charging mode is the same, in the charging mode 1 of the independent charging mode, the first coil L1 of the inductor unit 211 and Since energy is charged in the second coil L2 and energy is discharged in the charging mode 1 of the redundant charging mode, the charging mode 1 of the redundant charging mode may be referred to as the charging mode 1 ′. In the independent charging mode 3, the first coil L1 and the second coil L2 of the inductor unit 211 are charged with energy, and the charging mode 3 of the redundant charging mode 3 emits energy. May be represented as the charging mode 3 '.

Therefore, even though the switch state of the first switching element Q1 and the second switching element Q2 is the same, the energy state of the inductor is different. Therefore, the charging mode 1 'and the charging mode 3' are added to the battery 100 when the charging operation is performed. Six operating modes can be said to occur.

Accordingly, during the charging operation of the battery 100, the switching state of the first switching element Q1 and the second switching element Q2 of the bidirectional switching unit 213 and the first coil L1 and the second of the inductor unit 211 are determined. The operation state of each mode according to the change of energy of the coil L2 may be shown in Table 2 below.

TABLE 1

<Neutral Point Control in Redundant Charging Mode>

On the other hand, if the balance between the DC link voltage (Vc1) of the upper capacitor 232 and the DC link voltage (Vc2) of the lower capacitor 234 due to some of the redundant charging, the upper capacitor 232 or the lower capacitor 234 The capacitor may be burned out by the overvoltage applied thereto, and the charging quality of the battery 100 may be deteriorated due to the uneven charging current for one period of the charging PWM.

Meanwhile, in the charging mode 4 of the redundant charging, the first switching element Q1 and the second switching element Q2 are turned on at the same time, so that the upper capacitor 232 and the lower capacitor 234 are simultaneously discharged, so that the direct current of the capacitor bank circuit 230 is reduced. Since the link voltage is charged in the battery 100, the discharge amount of the upper capacitor 232 or the lower capacitor 234 cannot be differentiated, and in the charging mode 1 and the charging mode 3 occurring after the charging mode 4, As the discharge amounts of the capacitors 232 and 234 are differentiated, neutral point control is possible.

Specifically, in the charging mode 4, the battery is charged by depressurizing to the sum of the upper and lower DC link voltages Vc1 + Vc2 and energy is applied to the first coil L1 and the second coil L2 of the inductor unit 211. The charging energy is proportional to a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time.

In this case, in the charging mode 1 section or the charging mode 3 section operating after the charging mode 4, the emission energy of the inductor should be equal to the charging energy of the inductor in the charging mode 4.

Therefore, the emission energy of the inductor unit 211 in the charging mode 1 or the charging mode 3 is also proportional to a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time.

However, the charging mode 1 or the charging mode 3 has a cyclic operation in which the charging energy of the inductor unit 211 is released and a boost boosting characteristic in which energy of the upper capacitor 232 or the lower capacitor 234 is transferred to the battery. In the charging mode 1 or the charging mode 3, the discharge amount of the upper capacitor 232 or the lower capacitor 234 may be proportional to the emission energy of the inductor unit 211.

Accordingly, the discharge amount of the upper capacitor 232 may be proportional to a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time in the charging mode 4 before the charging mode 1.

In addition, the discharge amount of the lower capacitor 234 may be proportional to a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time in the charging mode 4 before the charging mode 3.

The first switching element Q1 and the second switching element Q2 are turned on at the same time in the charging mode 4 before the charging mode 1 and the first switching element Q1 and the second in the charging mode 4 before the charging mode 3. The discharge amount of the upper capacitor 232 and the discharge amount of the lower capacitor 234 may be differently set by differently setting the sections in which the switching element Q2 is simultaneously turned on.

However, in the charging mode 4, the period in which the first switching element Q1 and the second switching element Q2 are turned on at the same time is the pulse width of the charging PWM signal supplied to the first switching element Q1 or the second switching element. It is proportional to the pulse width of the wire PWM signal supplied to Q2.

That is, the charge PWM signal supplied to the first switch element Q1 is a PWM (Pulse Width Modulation) signal in which the pulse width is simultaneously changed from side to side based on the center of the pulse waveform according to the duty value or the reference value of the DC level, The charging PWM signal supplied to the second switch element Q2 may be the PWM signal having the same pulse width as the charging PWM signal supplied to the first switch element Q1 and having a phase shift of 180 degrees. .

Accordingly, in order to differentiate the discharge amount of the upper capacitor 232 in the charging mode 1, the offset offset PWM signal, which is an offset weight, is supplied to the first PWM or the second switching element Q1 in the charging mode 4 before the charging mode 1. The charging PWM signal supplied to the switching element Q2 is selected and applied. That is, the control circuit 290 transmits the charging PWM signal having the charging offset PWM signal to which the offset weight is added to the bidirectional switching unit 213.

In addition, the charge offset PWM signal, which is an offset weight for differentiating the discharge amount of the lower capacitor 234 in the charge mode 3, may be a charge PWM signal supplied to the first switching element Q1 or the first switching element Q1 in the charge mode 4 before the charge mode 3. The charging PWM signal supplied to the second switching element Q2 may be selected and applied. The control circuit 290 transmits a charging PWM signal having a charging offset PWM signal to which the offset weight is added to the bidirectional switching unit 213.

Therefore, similar to the neutral point control in the independent charging mode, the discharge amount of the upper capacitor 232 uses the charge PWM signal supplied to the first switch element Q1, and the discharge amount of the lower capacitor 234 is the second switching element. The neutral point control of the redundant charging mode is performed using the charging PWM signal supplied to Q2.

Accordingly, when the upper DC link voltage Vc1 becomes greater than the lower DC link voltage Vc2 due to external factors when the battery 100 is charged in the redundant charging mode, the control circuit 290 removes the charging PWM signal to which the charging offset PWM signal is weighted. The gate terminal of the first switching element Q1 is provided, and the bidirectional switching unit 213 performs neutral point control. That is, the voltage difference between the upper DC link voltage Vc1 and the lower DC link voltage Vc2 is removed by making the discharge amount of the upper DC link voltage Vc1 larger than the discharge amount of the lower DC link voltage Vc2.

In addition, if the lower DC link voltage Vc2 becomes greater than the upper DC link voltage Vc1 when the battery is charged in the redundant charging mode, the control circuit 290 transmits the charging PWM signal to which the charging offset PWM signal is weighted, the second switching element Q2. In this case, the bidirectional switching unit 213 performs neutral point control. That is, the discharge amount of the lower DC link voltage Vc2 is greater than the discharge amount of the upper DC link voltage Vc1, so that the voltage difference between the upper DC link voltage Vc1 and the lower DC link voltage Vc2 is removed.

On the other hand, the control circuit 290 is independent according to the duty value that is automatically changed by the correlation between the storage voltage Vbat of the battery 100 and the voltage of the lower DC link voltage (Vc2) and the upper DC link voltage (Vc1). Since the charging to redundant charging or the redundant charging to the independent charging is performed, the control circuit 290 does not need to determine whether the current control state is independent charging or redundant charging.

However, the charge PWM signal with the charge offset PWM signal of the upper DC link voltage Vc1 is applied to the first switching element Q1 in the independent charging mode and to the second switching element Q1 in the redundant charging mode, or When the charge PWM signal with the charge offset PWM signal of the DC link voltage Vc2 is applied to the second switching element Q2 in the independent charging mode and to the first switching element Q1 in the redundant charging mode, the control circuit ( 290 must determine whether it is an independent charging mode or a redundant charging mode, but as a result, the stability of the neutral point control may be degraded due to an error in detection.

Therefore, in the independent charging mode and the redundant charging mode, if the charging PWM signal including the charging offset PWM signal is provided to the same switching device and the offset weight is applied to the same capacitor, the step of determining whether the independent charging mode or the redundant charging mode is omitted is omitted. Therefore, the stability of the neutral point control can be secured.

Subsequently, when the discharge mode command signal of the battery 100 is transmitted to the control circuit 290 of the power converter 200 in the power management system 400, the control circuit 290 of the three-level interleaved circuit 210. The switching signal for turning off the first switching element Q1 and the second switching element Q2 of the bidirectional switching unit 213 is discharged to the third switching element Q3 and the fourth switching element Q3, respectively. The signal is sent, and the voltage charged in the battery 100 is boosted and converted to the capacitor bank circuit 230.

That is, in the discharge mode of the battery 100, the third switching element Q3 and the fourth switching element Q4, the first switching element Q1, and the second switching element Q2 of the bidirectional switching unit 213 are respectively provided. Discharge of the battery 100 is performed based on the connected body diode.

Meanwhile, in the discharge mode, two discharge PWMs having a phase shift of 180 degrees and switching to the same duty are supplied to the gate ends of the third switching element Q3 and the fourth switching element Q4, respectively, and the duty value is 0.5. If it is below, it operates in the independent discharge mode which does not overlap two discharge PWM, and when duty value becomes larger than 0.5, it operates in the overlapping discharge mode which generate | occur | produces the area which overlaps two discharge PWM. In this case, the control circuit 290 may include a discharge offset PWM signal in the two discharge PWMs switching to the same duty to remove the voltage imbalance between the upper capacitor 232 and the lower capacitor 234 of the capacitor bank circuit 230. have.

<Discharge Mode of 3-Level Interleaved Charge-Discharge Circuit>

The three-level interleaved charge / discharge circuit 210 receiving the discharge PWM signal from the control circuit 290 discharges the voltage of the battery 100 to supply DC power to the capacitor bank circuit 230. More specifically described with reference to 5 and 6 as follows.

5A to 5D are circuit diagrams illustrating an operation process for each mode during the discharge operation of the battery 100 based on the three-level interleaved charge / discharge circuit 210 shown in FIG. 2, and FIG. Figure 5 shows the output waveforms for each mode.

Here, the discharge PWM signal supplied to the third switch element Q3 is a method of obtaining a PWM pulse waveform in which the rising edge and the falling edge are generated by comparing the reference of the DC level with the triangular wave in the control circuit 290 according to the duty value. A pulse width modulation (PWM) signal in which the pulse width is simultaneously changed from side to side with respect to the center of the pulse waveform, and the discharge PWM signal supplied to the fourth switch element Q4 is charged to the third switch element Q3. It is a PWM signal having the same pulse width as the PWM signal and having a phase shift of 180 degrees.

Accordingly, there are four switch combinations that can be generated by the third switch element Q3 and the fourth switching element Q4, and the discharge mode of the battery 100 is the third switch element Q3 and the fourth switching element Q4. Non-crossing mode when overlapping discharge PWM signal supplied to the non-overlapping mode (Non-crossing mode) includes a overlapping mode (Crossing mode), the independent discharge mode is a buck and boost (boost) Conversion is sequentially performed, and the redundant discharge mode may be provided to perform boost converting.

On the other hand, the DC link voltage Vc1 of the upper capacitor or the DC link voltage Vc2 of the lower capacitor is 1/2 of the voltage between DC (+) and DC (-), and the three-level interleaved charge / discharge circuit 210 is discharged. It is maintained at the same value by), and the storage voltage Vbat of the battery 100 varies from a high value to a low value during discharge.

On the other hand, the principle that the bidirectional inverter 250 converts the DC voltage of the capacitor bank circuit 230 to an AC voltage and supplies it to a system or a load will be omitted since it is widely known in the art.

First, when the AC power is abnormal, the circuit breaker 271 of the input blocking circuit 270 is blocked at high speed based on the control circuit 290 to prevent the abnormal AC power from being supplied to the load.

<Discharge Operation in Independent Discharge Mode>

In the energy storage device of the present invention, for example, a 12V lead acid battery may be a battery input system in which 16, 20, 30 and 40 cells are connected in series. The independent discharge mode and the redundant discharge mode are generated by the correlation between the DC link voltage (Vc1 or Vc2), which is convenient for explaining the discharge operation. Therefore, the description of the charging operation in the 16 cells, 20 cells and 40 cells in which only one of the independent discharge mode and the redundant discharge mode occurs may be omitted.

Since the discharge end voltage of 12V lead acid battery is generally 10.2V per cell, the lowest voltage of battery input is 306V in the system with 30 cells connected in series, and the full charge voltage is generally 13.5V per cell. Can be seen at 405V. Therefore, the battery input voltage may vary between 306V and 405V depending on the state of charge or discharge of the battery.

For the sake of explanation, assuming that the energy storage system is operated in the charging mode in the previous operation process, the battery voltage is completed charging up to 405V, which is the full charge voltage, and switched to the discharge mode. The discharge PWM signal is supplied to the third switch element Q3 and the fourth switching element Q4 to discharge the storage voltage of the battery and charge the capacitor bank circuit 230. At this time, the charging voltage of the capacitor bank circuit 230 is 700V.

Meanwhile, in the battery discharge state, the DC link voltage Vc1 of the upper capacitor of the DC link and the DC link voltage Vc2 of the lower capacitor are 350V, which is 1/2 of the voltage between DC (+) and DC (-). Assume it is driven.

Subsequently, the control circuit 290 controls the bidirectional inverter 250 to change the DC link capacitor 700V between DC (+) and DC (-) into an AC voltage and supply the system or a load.

For reference, in general, the discharge PWM signal generated from the control circuit 290 increases from the initial duty state of zero until the control state becomes normal, and then increases to a normal state. It has a variable characteristic.

On the other hand, the battery charged to the full charge voltage starts to discharge at 405V and operates in the independent discharge mode until the terminal voltage of the battery is equal to 350V, which is the voltage of the upper capacitor (Vc1) or the voltage of the lower capacitor (Vc2). In addition, the two discharge PWM signal duty supplied to the third switch element Q3 and the fourth switching element Q4 is maintained within the range of 0 to 50%, and the two discharge PWM signal dutys are the values of the inductor and the switching frequency. It is determined by and load.

Accordingly, the third switch element starts to discharge at 405V until the storage voltage of the battery 100 becomes 350V, which is 1/2 of the voltage between the DC link DC (+) and DC (-). Two discharge PWMs supplied to Q3 and the fourth switching element Q4 may be operated in an independent discharge mode that does not overlap.

That is, in the independent discharge mode in which the storage voltage Vbat of the battery 100 satisfies condition 1 which is greater than the DC link voltage Vc1 or Vc2 or 1/2 (350 V) of the capacitor bank voltage, the three-level interleaved charge / discharge circuit 210 and the capacitor bank circuit 230 sequentially perform the discharge mode 5 → discharge mode 6 → discharge mode 7 → discharge mode 6 of FIG. 5.

Referring to the operation of the discharge mode 6 in the discharge mode 5, as shown in (a) of FIG. 5, when the third switching element Q3 is turned on, the storage voltage Vbat of the battery 100 is lower capacitor ( 234 is charged to perform decompression (buck) conversion, and as shown in (b), when the third switching element Q3 is turned off , a circulation circuit including the battery 100 is formed, and at the same time, Step-up (boost) converting is performed in which the storage voltage Vbat is collectively charged in the upper capacitor 232 and the lower capacitor 234. The same applies to the operation in the independent discharge mode 7 shown in (c) to the independent discharge mode 6 shown in (b).

At this time, in the independent discharge mode, the voltage equation and the output voltage Vc2 of the first coil L1 and the second coil L2 of the inductor 211 in the discharge mode 5 to the discharge mode 6 are represented by the following equations (9) and (10). ), The voltage equation and the output voltage Vc1 of the first coil L1 and the second coil L2 of the inductor in the discharge mode 7 → discharge mode 6 are given by equations (11) and (12).

.. 식 9

.. Equation 9

… 식 10

… Equation 10

.. 식 11

.. Equation 11

.. 식 12

.. Equation 12

That is, as shown in equations (10) and (12), the lower DC link voltage Vc2 includes the storage voltage Vbat, the upper DC link voltage Vc1 of the battery 100, and the third switching element Q3. The upper DC link voltage Vc1 is determined by the duty ratio d ' _Q3 of the storage voltage Vbat, the lower DC link voltage Vc2 of the battery 100, and the duty of the fourth switching element Q4. It can be seen that it is determined by the ratio d ' _Q4 .

<Neutral Point Control in Independent Discharge Mode>

On the other hand, the neutral point control in the independent discharge mode is possible in the discharge mode 5 to discharge the battery 100 voltage based on the third switching element (Q3) to independently charge the lower capacitor 234 and to the fourth switching element (Q4). The battery 100 may be discharged in the discharge mode 7 to independently charge the upper capacitor 232 by discharging the voltage.

That is, in the discharge mode 5 during the independent discharge mode, the storage voltage of the battery 100 is discharged by the third switching element Q3 and charged in the lower capacitor 234. When the link voltage Vc1 is greater than the lower DC link voltage Vc2 of the lower capacitor 234, the control circuit 290 may discharge the PWM including the discharge offset PWM signal having an increased offset weight of the third switching element Q3. The signal is transferred to the gate terminal of the third switching element Q3, and the bidirectional switching unit 213 performs neutral point control.

That is, the lower direct current link voltage Vc2 of the lower capacitor 234 charged from the battery based on the discharge offset PWM signal to which the offset weight is given is greater than the upper direct current link voltage Vc1 of the upper capacitor 232 so that the upper direct current link The voltage difference between the voltage Vc1 and the lower direct current link voltage Vc2 is eliminated.

In addition, in the discharge mode 7 during the independent discharge mode, the voltage of the battery 100 is discharged by the fourth switching element Q4 and charged in the upper capacitor Q2, so that the lower DC link voltage Vc2 of the lower capacitor 234 is discharged. ) Is greater than the upper DC link voltage Vc1 of the upper capacitor 232, the control circuit 290 transmits a discharge PWM signal including an offset weighted discharge offset PWM signal to the gate terminal of the fourth switching element Q4. To perform neutral point control. That is, by making the upper DC link voltage Vc1 of the upper capacitor 232 charged from the battery based on the increased discharge offset PWM signal larger than the lower DC link voltage Vc2 of the lower capacitor 234, the upper DC link voltage ( The voltage difference between Vc1) and the lower DC link voltage Vc2 is eliminated.

<Discharge operation in double discharge mode>

On the other hand, if the storage voltage of the battery which started to discharge at the initial 405V is lower than the DC link voltage Vc1 (350V) or Vc2 (350V), the battery can no longer be discharged in the independent discharge mode, the control circuit 290 is the third switching element (Q3) Increases the duty of the discharge P WM signal and the discharge PWM signal of the fourth switching device Q4 by 50% or more to generate two discharge PWM signals in which two PWM overlapping intervals are generated, and then transfer them to the bidirectional switching unit 213. The bidirectional switching unit 213 operates in the redundant discharge mode.

That is, the redundant discharge mode is a case where the storage voltage Vbat of the battery 100 satisfies Condition 2 smaller than the upper DC link voltage Vc1 or the lower DC link voltage Vc1 that is 1/2 of the DC link voltage. As a mode performed in the three-level interleaved charge and discharge circuit 210, the discharge mode 8 → discharge mode 5 → discharge mode 8 → discharge mode 7 of FIG. It is performed by sequentially repeating.

In the discharge mode 8 shown in FIG. 5D, when the third switching device Q3 and the fourth switching device Q4 are turned on at the same time, the inductor is based on the storage voltage Vbat of the battery 100. Boost energy is charged in the first coil L1 and the second coil L2.

Subsequently, in the discharge mode 5 shown in FIG. 5A, the control circuit 290 turns off the fourth switching element Q4 while keeping the second switching element Q3 on and thereby inductors in the previous discharge mode 8. The lower capacitor 234 is charged with the energy stored in the first and second coils L1 and L2.

Subsequently, the control circuit 290 repeats the discharge mode 8 shown in FIG. 5D to boost the first and second coils L1 and L2 of the inductor based on the storage voltage Vbat of the battery 100. Energy is charged

Next, in the discharge mode 7 illustrated in FIG. 5C, the control circuit 290 turns off the third switching element Q3 while maintaining the on state of the fourth switching element, thereby inducing the inductor in the previous discharge mode 8. The upper capacitor 232 is charged with the energy stored in L1 and L2.

The voltage equation and output voltage of the inductor in discharge mode 8 → discharge mode 5 during the redundant discharge mode are given by equations (13) and (14), and the voltage equation and output of the inductor in redundant discharge mode 6 → redundant discharge mode 7 The voltage is given by equations (15) and (16).

In equations (14) and (16), the lower DC link voltage Vc2 is applied to the overlap duty ratio d _{Q3 / Q4} of the storage voltage Vbat, the third switching element Q3, and the fourth switching element _Q4 . Determined by the top The DC link voltage Vc1 may be determined by the overlap duty ratio d _{Q3 / Q4} of the storage voltage Vbat, the third switching element Q3, and the fourth switching element Q4.

.. 식 13

.. Equation 13

.. 식 14

.. Equation 14

.. 식 15

.. Equation 15

.. 식 16

.. Equation 16

In the independent discharge mode, the storage voltage of the battery is transferred to the upper capacitor 234 and the lower capacitor 234 during the on / off switching operation of the third and fourth switching elements Q3 and Q4. In the discharge mode, the storage voltage of the battery is transferred to the upper capacitor 234 and the lower capacitor 234 in the off periods of the third and fourth switching elements Q3 and Q4.

However, although the switching states of the third and fourth switch elements of the independent discharge mode 5 and the redundant discharge mode 5 are the same, the independent discharge mode 5 stores the energy in the inductor and the redundant discharge mode 5 emits the energy in the inductor. Denotes a redundant discharge mode 5 ′ different from the independent discharge mode 5.

In addition, although the switching states of the third and fourth switching devices of the independent discharge mode 7 and the overlapped discharge mode 7 are the same, the independent discharge mode 7 stores the energy in the inductor, and the redundant discharge mode 7 emits the energy of the inductor. 7 may be distinguished from the independent discharge mode 7 and may be represented as the overlapped discharge mode 7 '.

Therefore, the energy flows are different even if the switch state of the third switching element Q3 and the fourth switching element Q4 is the same, so that the discharge mode includes six operation modes including the redundant discharge mode 5 'and the redundant discharge 7'. Is done.

The operation mode and mode change according to the state change of the switch and inductor energy in the discharge mode are shown in the following table.

<Neutral point control in double discharge mode>

In the discharge mode 8, which is a redundant discharge mode, the third switching element Q3 and the fourth switching element Q4 are turned on at the same time to charge boost energy to the inductors L1 and L2 based on the battery voltage Vbat. In the discharge mode 5 and the discharge mode 7 generated after the discharge mode 8, the battery 100 may differentiate the upper capacitor 232 and the lower capacitor 234 and charge the neutral point.

In detail, the energy for charging the lower capacitor 234 in the redundant discharge mode 5 and the energy for charging the upper capacitor 232 in the redundant discharge mode 7 are the third switching element Q3 and the fourth switching element in the redundant discharge mode 8. It is proportional to the section where (Q4) is turned on at the same time.

Accordingly, the third switching device Q3 and the fourth switching device Q4 are turned on at the same time in the redundant discharge mode 8 before the overlapping discharge mode 5 and the third switching device in the redundant discharge mode 8 before the redundant discharge mode 7. The charging amount of the upper capacitor 232 and the charging amount of the lower capacitor 234 may be different from each other by varying a period in which Q3) and the fourth switching element Q4 are simultaneously turned on.

However, in the discharge mode 8, the size of the section in which the third switching element Q3 and the fourth switching element Q4 are simultaneously turned on is the pulse width of the PWM supplied to the third switching element Q3 or the fourth switching. It has a characteristic proportional to the pulse width of the PWM supplied to the element Q4.

In detail, the charge PWM signal supplied to the third switch element Q3 is a pulse width modulation (PWM) signal in which pulse widths are simultaneously changed from side to side based on the center of the pulse waveform according to the duty value, and the fourth switch element The charging PWM signal supplied to Q4 may be a PWM signal having the same pulse width as the charging PWM signal supplied to the third switch element Q3 and having a phase shift of 180 degrees.

Therefore, the offset weight value for differentiating the charge amount of the lower capacitor 234 in the redundant discharge mode 5 is the PWM or the fourth switching element Q4 supplied to the third switching element Q3 in the discharge mode 8 before the redundant discharge mode 5. Offset weighting can be applied by selecting PWM supplied to.

The offset weight value for differentiating the charge amount of the upper capacitor 234 in the redundant discharge mode 7 is the PWM or the fourth switching element Q4 supplied to the third switching element Q3 in the discharge mode 8 before the redundant discharge mode 7. Offset weighting can be applied by selecting PWM supplied to.

Therefore, similar to the neutral point control in the independent discharge mode, the charge amount of the lower capacitor 234 is supplied to the third switching element Q3 by using the PWM, and the discharge amount of the upper capacitor 232 is determined by the fourth switching element Q4. By using the PWM supplied to the neutral point control of the redundant charging mode can be performed.

That is, in the discharge mode 5 of the overlapping discharge mode, the upper DC link voltage of the upper capacitor 232 is discharged as a factor in discharging the battery 100 voltage by the third switching element Q3 to charge the lower capacitor 234. When Vc1) is greater than the lower DC link voltage Vc2 of the lower capacitor 234, the control circuit 290 increases the discharge offset PWM signal of the third switching element Q3 to the gate terminal of the third switching element Q3. Pass to perform neutral point control. That is, based on the increased discharge offset PWM signal, the amount of charge of the lower DC link voltage Vc2 of the lower capacitor 234 is greater than the amount of charge of the upper DC link voltage Vc1 of the upper capacitor 232 so that the upper DC link voltage ( The voltage difference between Vc1) and the lower DC link voltage Vc2 is eliminated.

In addition, the discharge voltage of the battery 100 is discharged by the fourth switching element Q4 in the discharge mode 7 during the overlapping discharge mode to charge the upper capacitor 232 with a certain factor as a lower DC link voltage of the lower capacitor 234 ( When Vc2 is greater than the upper DC link voltage Vc1 of the upper capacitor 232, the control circuit 290 increases the discharge offset PWM signal of the fourth switching element Q4 to the gate terminal of the fourth switching element Q4. Pass to perform neutral point control. That is, the charging amount of the upper DC link voltage Vc1 of the upper capacitor 232 is greater than the charging amount of the lower DC link voltage Vc2 of the lower capacitor 234 based on the increased discharge offset PWM signal. The voltage difference between Vc1) and the lower DC link voltage Vc2 is eliminated.

On the other hand, the control circuit 290 is independent of the duty value that is automatically changed by the correlation between the storage voltage (Vbat) of the battery 100 and the voltage of the lower DC link voltage (Vc2) and the upper DC link voltage (Vc1). Since the discharge is switched from the redundant discharge or the redundant discharge to the independent discharge, the control circuit 290 does not need to determine whether the current control state is the independent discharge or the duplicate discharge.

In detail, the charge offset PWM signal of the upper DC link voltage Vc1 is applied to the fourth switching device Q4 in the independent discharge mode and the third switching device Q3 in the redundant discharge mode or the lower DC link voltage. When the charge offset PWM signal of Vc2 is applied to the third switching element Q3 in the independent discharge mode and is applied to the fourth switching element Q4 in the redundant discharge mode, the control circuit 290 is overlapped in the independent discharge mode. It is necessary to determine whether the discharge mode, and as a result, the stability of the neutral point control may be degraded due to the error of detection.

Therefore, if the charging offset is applied to the same capacitor using the same switching device in the independent discharge mode and the redundant discharge mode, the step of determining whether the independent discharge mode or the redundant discharge mode is omitted can ensure the stability of the neutral point control. .

Hereinafter, the charging and discharging operation modes for the plurality of battery cells will be described with reference to Tables 3 and 4.

When the cells of the battery are 16 or 20 cells, the storage voltage (Vbat) of the battery 100 of 700V is the upper DC link voltage (Vc1: 350V) or the lower DC link voltage (Vc2: 350V) which is 1/2 of the DC link voltage. It is always lower, so it operates only in the independent charging mode (mode 1, 2, 3, 2) when charging, and operates only in the overlapping discharge mode (mode 8, 5 ', 8, 7,) during discharge.

When the battery cell is 30 cells, the storage voltage Vbat of the battery 100 is lower than the upper DC link voltage (Vc1: 350V) or the lower DC link voltage (Vc2: 350V), which is 1/2 of the DC link voltage. In this mode, charging is operated in the independent charging mode (mode 1, 2, 3, 2) and discharge is operated in the overlapping discharge mode (mode 8, 5 ', 8, 7,).

In addition, in the region where the storage voltage Vbat of the battery 100 is higher than the upper DC link voltage Vc1: 350V or the lower DC link voltage Vc2: 350V, which is 1/2 of the DC link voltage, charging is performed in the redundant charging mode ( 4, 1 ', 4, 3'), and the discharge is operated in the independent discharge modes 5, 6, 7, 6.

Meanwhile, when the battery cell is 40 cells, the storage voltage Vbat of the battery 100 is always higher than the upper DC link voltage (Vc1: 350V) or the lower DC link voltage (Vc2: 350V), which is 1/2 of the DC link voltage. Because it operates in the area, it operates only in the region of overlapping charging mode (mode 4, 1 ', 4, 3') during charging, and operates only in the area of independent discharge mode (mode 5, 6, 7, 6) during discharge.

TABLE 3

TABLE 4

Accordingly, the charging mode and the discharge mode can be performed for various battery cells, and the neutral point control can be performed, thereby having compatibility with the electric energy storage system for the number of battery cells.

Accordingly, when the AC power supplied from the system is normal, the DC power converted by the bidirectional inverter circuit is decompressed to charge the battery, and when the system power is peak or the system power is abnormal, the battery storage voltage is boosted to boost the battery. In the transfer, the three-level bidirectional inverter and the three-level interleaved charge and discharge circuit can be used to improve the charge and discharge efficiency of the battery.

In addition, since the neutral point control is performed during charging and discharging without additional equipment, the system can be stabilized, the cost of electric energy loss of the user can be reduced, the discharge time of the battery can be extended, and the light and small size of the electric energy storage system can be reduced. .

Although the embodiments have been described by the limited embodiments and the drawings as described above, various modifications and variations are possible to those skilled in the art from the above description. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different form than the described method, or other components. Or even if replaced or substituted by equivalents, an appropriate result can be achieved. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

When the AC power supplied from the system is normal, the converted DC power is charged to the battery by reducing the converted DC power according to the bidirectional inverter circuit, and when the system power is peaked or the system power is abnormal, the storage voltage of the battery is boosted and transferred to the bidirectional inverter circuit. In this case, a three-level bidirectional inverter and a three-level interleaved charging and discharging circuit can be used to charge and discharge the battery to improve charging efficiency, and to improve the stability of the system by controlling the neutral point during charging and discharging control without any additional device. For electrical energy storage systems with three-level interleaved chargers that can be implemented, they can bring significant advances in operational accuracy and reliability, and further in terms of performance efficiency. Not only that, but it can be done clearly The invention in the industrial applicability.

Claims (23)

In the electrical energy storage system,
When the system power is peaked or the system power is abnormal, the function of converting the battery into the DC form by using the stored DC power supply to the system or the load and converting the AC power of the system into the DC form when the system power is at light load or at night time Is provided with a power converter to perform the function of storing in the battery,
The power converter,
An input blocking circuit in which a static switch is connected in series with a breaker to cut off AC power supplied from the outside at high speed when a power failure;
Based on the three-level switching operation of a plurality of switching elements, it operates as a rectifier for converting a steady state AC power supplied from the outside into a DC form during charging operation of the switching element, and a DC link of the capacitor bank circuit during the discharge operation of the storage voltage of the battery. A bidirectional inverter circuit operating as an inverter for converting a voltage into an alternating current form and transferring the voltage to a grid or a load;
A three-level interleaved charge / discharge circuit for reducing the DC power supplied from the bidirectional inverter circuit to charge the battery, and boosting and outputting the DC power of the battery;
A capacitor bank circuit for receiving and supplying the DC power of the bidirectional inverter circuit to the three level interleaved circuit for transmission, and for linking and transmitting the DC power of the three level interleaved circuit to the bidirectional inverter circuit; And
Generate signals for performing charge / discharge control and neutral point control of the input disconnect circuit, the three-level bidirectional inverter circuit, and the three-level interleaved charge / discharge circuit and control the overall operation of the electrical energy storage system based on the generated signals. An electrical energy storage system having a three-level interleaved charger, characterized in that it comprises a control circuit for controlling. The method of claim 1, wherein the three-level interleaved charge and discharge circuit
The first coil L1 connected to the positive terminal of the battery and the second coil L2 connected to the negative terminal of the battery are connected to the capacitor bank circuit to reduce the DC link voltage of the capacitor bank circuit. An inductor unit charging a battery or boosting a voltage of the battery and supplying the battery to the capacitor bank circuit;
First and third switching elements Q1 and Q3 are connected in parallel to the right side of the first coil L1 of the inductor unit, and second and fourth switching elements Q2 and Q4 are connected to the right side of the second coil L2. ) Are connected in parallel, respectively, and connect the first to fourth body diodes between the output terminals and the input terminals of the first to fourth switching elements, respectively, to perform charge / discharge control and neutral point control according to the control of the control circuit. Electrical energy storage system having a three-level interleaved charger, characterized in that it comprises a two-way switching unit. The method of claim 2, wherein the capacitor bank circuit,
The upper capacitor is connected between the input terminal of the first switching element Q1 and the ground N of the bidirectional switching unit, and the lower capacitor is connected between the ground terminal N and the output terminal of the second switching element Q2 to provide the bidirectional switching unit. Electric energy storage having a three-level interleaved charging and discharging, characterized in that it is provided so as to transfer the battery storage voltage received via the DC link to the bidirectional inverter circuit, and to direct the DC power of the bidirectional inverter circuit to the DC link. system. The method of claim 3, wherein the control circuit,
According to the charge mode command signal of the power management system generated based on the battery monitoring result of the battery management system, a charge PWM signal for charging the battery is generated by reducing the DC link voltage of the capacitor bank circuit and generating the generated charge PWM signal. And to a second switching element,
And generate a switching signal for turning off the third and fourth switching elements and transfer the generated switching signal to the third and fourth switching elements. . The method of claim 4, wherein the charging PWM signal is
A three-level interleaved charger including a predetermined charge offset PWM signal in the charging PWM signal for switching to the same duty to perform neutral point control by eliminating voltage imbalance between the upper capacitor and the lower capacitor of the capacitor bank circuit Electrical energy storage system having a. The method of claim 5, wherein the charge PWM signal supplied to the first switching device
The PWM is generated by comparing the DC level reference to the triangular wave in the control circuit to obtain a PWM pulse waveform in which the rising and falling edges are generated, and the pulse width is simultaneously changed from side to side based on the center of the pulse waveform according to the duty value. (Pulse Width Modulation) signal,
The charge PWM signal supplied to the second switching element is
An electric energy storage system having a three-level interleaved charging and discharging device, characterized in that the PWM signal having a pulse width equal to the charge PWM signal supplied to the first switch element and having a phase shift of 180 degrees. The method of claim 6, wherein the control circuit
The charging PWM signal is generated according to a duty value that varies according to the correlation between the storage voltage Vbat of the battery and the voltage of the lower DC link voltage Vc2 and the upper DC link voltage Vc1.
The bidirectional switching unit,
When the storage voltage Vbat of the battery satisfies the condition 1, which is smaller than the DC link voltage Vc1 or Vc2 or the DC link voltage of the capacitor bank circuit, the charging PWM signal of the non-overlapping control circuit is decompressed. Independent charging mode (Non-crossing mode) to perform the conversion,
When half of the DC link voltage Vc1 or Vc2 or the DC link voltage of the capacitor bank circuit satisfies Condition 2 which is smaller than the charging voltage Vbat of the battery 100, the pressure is reduced based on the overlapping charging PWM signal of the control circuit. An electrical energy storage system having a three-level interleaved charger, characterized in that it comprises a cross-charging mode for sequentially performing buck and boost converting. The method of claim 7, wherein the independent charging mode of the bidirectional switching unit
A charging mode 1 in which the DC link voltage Vc1 is charged to the battery when the first switching element Q1 is turned on based on the charging PWM signal of the control circuit;
And the first switching element (Q1) to the circulating mode by the closed circuit which does not include the direct-current link voltage (Vc1) when off-load operation the second charging mode,
A charging mode 3 in which the DC link voltage Vc2 is charged to the battery when the second switching element Q2 is turned on;
When the second switching element (Q2) is off and has a three-level interleaved charger, characterized in that it is provided to sequentially perform the charging mode 2 operating in a cyclic mode by a closed circuit that does not include a DC link voltage (Vc2) Electrical energy storage system. The method of claim 8, wherein the control circuit
In order to ensure the stability of the neutral point control by omitting the step of determining whether the charging mode is the independent charging mode or the redundant charging mode, the charging PWM signal including the offset-weighted charging offset PWM signal in the independent charging mode and the redundant charging mode is the same bidirectional. An electrical energy storage system having a three-level interleaved charging and discharging, characterized in that provided to a selected one of the first switching element and the second switching element of the switching unit. The method of claim 9, wherein the bidirectional switching unit,
Three-level interleave, which is provided to perform neutral point control by varying the discharge amount of the upper and lower capacitors by the charge PWM signal of the control circuit increased by the charge offset PWM signal in the charge mode 1 and the charge mode 3 of the independent charge mode. Electrical energy storage system having a de-charger. The method of claim 10, wherein the bidirectional switching unit,
In the charging mode 1, when the upper DC link voltage Vc1 of the upper capacitor is greater than the lower DC link voltage Vc2 of the lower capacitor, the charging PWM signal of the control circuit in which the charging offset PWM signal is increased is the first switching element Q1. Is passed to the gate stage to perform neutral point control,
In the charging mode 2, when the lower DC link voltage Vc2 of the lower capacitor is temporarily greater than the upper DC link voltage Vc1 of the upper capacitor, the charging PWM signal of the control circuit in which the charging offset PWM signal is increased is changed to the second switching element. An electric energy storage system having a three-level interleaved charger / discharger, which is transmitted to the gate end of Q2) to perform neutral point control. The method of claim 7, wherein the control circuit
When the charging voltage of the battery is higher than the DC link voltage Vc1 or Vc2, the duty cycle of the charging PWM signal of the first switching device Q1 and the charging PWM signal of the second switching device Q2 is increased to generate an overlapping section of the charging PWM signal. Generates a charge PWM signal to pass to the bidirectional switching unit,
The bidirectional switching unit
When a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time occurs, the sum Vc1 + Vc2 of the DC link voltage Vc1 and Vc2 of the capacitor bank circuit is the inductor L1, L2. Charging mode 4, which charges the battery after decompression via),
While maintaining the on state of the first switching device, the second switching device Q2 is turned off to form a closed circuit for releasing energy stored in the inductors L1 and L2 in the previous charging mode 4 to store the battery voltage Vbat. Charge mode 1 for boosting the upper DC link voltage of the upper capacitor having a voltage lower than) to charge the battery,
When a section in which the first switching element Q1 and the second switching element Q2 are turned on at the same time occurs, the sum Vc1 + Vc2 of the DC link voltage Vc1 and Vc2 of the capacitor bank circuit is inductor L1, L2. Charging mode 4, which charges the battery after decompression via),
While maintaining the on state of the second switching element, the first switching element Q1 is turned off to form a closed circuit for releasing energy stored in the inductors L1 and L2 in the previous charging mode 4 to store the battery voltage Vbat. An electric energy storage system having a three-level interleaved charger and charger, characterized in that the charging mode 3 sequentially charging the battery by boosting and converting the lower DC link voltage of the lower capacitor having a lower voltage than). The method of claim 12, wherein the bidirectional switching unit,
In the charging mode 1 and the charging mode 3, which occurs after the charging mode 4 of the redundant charging mode, the neutral point control is performed by varying the discharge amount of the upper and lower capacitors by the charge PWM signal of the control circuit in which the charge offset PWM signal is increased. An electrical energy storage system having a three-level interleaved charger. The method of claim 13, wherein the bidirectional switching unit,
When the battery is charged in the redundant charging mode, when the upper DC link voltage Vc1 becomes greater than the lower DC link voltage Vc2, the charge PWM signal generated by the control circuit and the charge PWM signal weighted by the gate of the first switching element Q1 are converted into a gate. Forward to the stage for neutral control,
When the battery is charged in the redundant charging mode, when the lower DC link voltage Vc2 becomes greater than the upper DC link voltage Vc1, the charge PWM signal of the control circuit including the charge offset PWM signal is transmitted to the gate terminal of the second switching element Q2. Electrical energy storage system having a three-level interleaved charging and discharging, characterized in that the neutral point control. The method of claim 14, wherein the control circuit,
The discharge PWM signal is generated to supply DC power to the capacitor bank circuit by discharging the storage voltage of the battery based on the discharge mode command signal of the power management system generated based on the battery monitoring result of the battery management system. To the third and fourth switching elements,
And generate a switching signal for turning off the first and second switching elements and transfer the generated switching signal to the first and second switching elements. . The method of claim 15, wherein the discharge PWM signal supplied to the third switching device
The PWM is generated by comparing the DC level reference to the triangular wave in the control circuit to obtain a PWM pulse waveform in which the rising and falling edges are generated, and the pulse width is simultaneously changed from side to side based on the center of the pulse waveform according to the duty value. (Pulse Width Modulation) signal,
The discharge PWM signal supplied to the fourth switching device
And a PWM signal having a pulse width equal to that of the charging PWM signal supplied to the third switch element and having a phase shift of 180 degrees. The method of claim 16, wherein the control circuit,
Generate a discharge PWM signal having a duty value of PWM that varies by the correlation between the storage voltage of the battery (Vbat) and the voltage of the lower DC link voltage (Vc2) and the upper DC link voltage (Vc1),
The bidirectional switching unit,
When the storage voltage Vbat of the battery satisfies condition 1 which is greater than the DC link voltage Vc1 or Vc2 or the DC link voltage of the capacitor bank circuit, the battery is stored based on the discharge PWM signal of the non-overlapping control circuit. A non-crossing mode in which the voltage Vbat is sequentially reduced in pressure and in step-up conversion, and transferred to the capacitor bank circuit;
The discharge PWM signal of the overlapping control circuit when the storage voltage Vbat of the battery 100 satisfies Condition 2 which is smaller than the upper DC link voltage Vc1 or the lower DC link voltage Vc1 that is 1/2 of the DC link voltage. And a redundant discharging mode for converting the storage voltage Vbat of the battery to the capacitor bank circuit and transferring the voltage to the capacitor bank circuit. 18. The method of claim 17, wherein the independent discharge mode of the bidirectional switching unit
Discharge mode 5 in which the battery is depressurized and charged in the lower capacitor when the third switching element Q3 is turned on based on the discharge PWM signal of the control circuit;
When the third switching element Q3 is turned off, a circulation circuit including the battery 100 is formed, and at the same time, energy of the battery is charged by performing a boost (boost) conversion on the upper capacitor 232 and the lower capacitor 234. With discharge mode 6,
A discharge mode 7 for depressurizing the battery and charging the upper capacitor Vc1 when the fourth switching element Q4 is turned on;
When the fourth switching element Q4 is turned off, the circuit including the battery is formed, and at the same time, the discharge mode 6 for charging the upper capacitor and the lower capacitor by step-up-converting the storage voltage of the battery is sequentially performed. Electrical energy storage system having a de-charger. 19. The apparatus of claim 18, wherein the control circuit is
Generating a discharge PWM signal for switching to the same duty including an offset-weighted discharge offset PWM signal to perform neutral point control to remove voltage imbalance between the top capacitor and the bottom capacitor of the capacitor bank circuit,
The bidirectional switching unit,
In the discharge mode 5 and the discharge mode 7 of the independent discharge mode, three-level interleaved, the discharge offset PWM signal is provided to perform the neutral point control by varying the charge amount of the upper and lower capacitors based on the discharge PWM signal of the increased control circuit. Electrical energy storage system having a charge and discharge. The method of claim 19, wherein the bidirectional switching unit,
In the discharge mode 5 during the independent discharge, when the battery voltage is discharged by the third switching element Q3 to charge the lower capacitor, when the upper DC link voltage Vc1 of the upper capacitor becomes larger than the lower DC link voltage Vc2 of the lower capacitor. The discharge PWM signal of the control circuit including the discharge offset PWM signal is transmitted to the gate terminal of the third switching element Q3 to perform neutral point control,
In the discharge mode 7, when the battery voltage is discharged by the fourth switching element Q4 to charge the upper capacitor, the discharge offset PWM when the lower DC link voltage Vc2 of the lower capacitor becomes larger than the upper DC link voltage Vc1 of the upper capacitor. An electric energy storage system having a three-level interleaved charger / discharger, characterized in that a discharge PWM signal of a control circuit including a signal is transmitted to a gate terminal of a fourth switching element (Q4) to perform neutral point control. The method of claim 18, wherein the redundant discharge mode of the bidirectional switching unit
A discharge mode 8 in which boost energy is charged in the inductors L1 and L2 based on the storage voltage Vbat of the battery when a section in which the third switching element Q3 and the fourth switching element Q4 are turned on at the same time occurs;
Discharge mode 5 for turning off the fourth switching element Q4 while maintaining the on state of the third switching element to charge the lower capacitor with the energy stored in the inductors L1 and L2 in the previous discharge mode 8;
A discharge mode 8 in which boost energy is charged in the inductors L1 and L2 based on the storage voltage Vbat of the battery when a section in which the third switching element Q3 and the fourth switching element Q4 are turned on at the same time occurs;
The discharge mode 7 is sequentially performed to turn off the third switching element Q3 while maintaining the on state of the fourth switching element to charge the upper capacitor with the energy stored in the inductors L1 and L2 in the previous discharge mode 8. An electrical energy storage system having a three-level interleaved charger. The method of claim 21, wherein the bidirectional switching unit,
In the case of redundant discharge, in the discharge mode 5 and the discharge mode 7 after the discharge mode 8, the neutral point control is performed by varying the charge amount of the upper and lower capacitors based on the discharge PWM signal of the control circuit in which the discharge offset PWM signal is increased. Electrical energy storage system with three level interleaved charger. The method of claim 22, wherein the bidirectional switching unit,
In the discharge mode 5 during the overlapping discharge, when the storage voltage of the battery is discharged by the third switching element Q3 to charge the lower capacitor, the discharge occurs when the upper DC link voltage Vc1 of the upper capacitor becomes larger than the lower DC link voltage Vc2. The discharge PWM signal of the control circuit including the offset PWM signal is transmitted to the gate terminal of the third switching element (Q3) to perform the neutral point control,
In the discharge mode 7, when the storage capacitor of the battery is discharged by the fourth switching element Q4 to charge the upper capacitor, the lower DC link voltage Vc2 of the lower capacitor becomes higher than the upper DC link voltage Vc1 of the upper capacitor. An electric energy storage system having a three-level interleaved charger / discharger, characterized in that the neutral point control is performed by transferring a discharge PWM signal of a control circuit including an offset PWM signal to a gate terminal of a fourth switching element (Q4).

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