KR102035223B1 - Hybrid Energy Storage System - Google Patents

Abstract

An objective of the present invention is to provide a small-scale hybrid energy storage system having various operation modes. To this end, according to the present invention, the hybrid energy storage system comprises: a converter converting power generated from a photovoltaic module into DC power and outputting the DC power; an inverter converting the power generated from the photovoltaic module into AC power and outputting the AC power; a battery receiving the DC power from the converter to be charged; and an energy monitoring system (EMS) controlling the inverter and the converter in various operation modes.

Description

Hybrid Energy Storage System

Embodiments of the present invention relate to hybrid energy storage systems.

Recently, due to the depletion of fossil fuels such as coal and oil and the seriousness of environmental pollution, various models of alternative energy have been proposed.

Power generation or heating using renewable energy such as solar, wind, and tidal power can reduce energy dependence on fossil fuels and create a pollution-free environment. It is developing rapidly.

On the other hand, power generated from renewable energy sources, even if direct current or alternating current, because the frequency is different, it can not be directly connected or supplied to the grid. Accordingly, there is a need to convert direct current to alternating current or to adjust frequency, for which a grid tie inverter is generally used.

However, such a grid tie inverter converts a DC power source from a renewable energy source into an AC power source, adjusts frequency, and directly connects / supplies to the grid, which is not suitable for general industrial or home use. For example, grid tie inverters are not designed to directly supply AC power and charge batteries for general industrial electronics or consumer electronics.

The above-described information disclosed in the background technology of the present invention is only for improving the understanding of the background of the present invention, and thus may include information that does not constitute the prior art.

Problems to be solved according to an embodiment of the present invention are various operation modes (for example, the first mode of the turn-on and peak power generation of the photovoltaic module, the second mode of the grid off, the third mode of the furnace battery, the night There is provided a small scale hybrid energy storage system having a fourth mode, a night mode and a fifth mode of grid off, a night mode and a sixth mode of using an uninterruptible power supply (UPS).

Another problem to be solved according to an embodiment of the present invention is that it is possible to maintain the voltage at the neutral point uniformly by adding a simple algorithm without additional circuitry, so that the efficiency is high, the total harmonic distortion (THD) is low, and the switch stress is low. To provide a hybrid energy storage system having a small, bulky T-type three-level three-phase inverter.

Hybrid energy storage system according to an embodiment of the present invention includes a converter for converting the power generated from the solar power module to a DC power output; An inverter for converting and outputting power generated from the solar power module into AC power; A battery charged with DC power supplied from a converter; And an EMS (Energy Monitoring System) for controlling the converter and the inverter, wherein the EMS controls the converter during generation of the solar power module during the day to charge the battery with DC power, and controls the inverter to control home appliances and the The first operating mode of supplying AC power to the grid, the second operating mode of supplying AC power to home appliances by controlling the inverter when the grid is off and controlling the converter and the inverter by controlling the converter The third operating mode, which supplies AC power to home appliances and grids by controlling the inverter without charging, controls AC converters and inverters during the non-power generation of photovoltaic modules at night to convert AC power to home appliances The fourth operating mode to supply, control the converter and inverter when off the grid to convert the power of the battery to home appliances Flow by controlling a fifth operating mode, and the inverter and the converter to supply the power to charge the power to the grid, the battery can operate in any one of the sixth mode of the operating mode used in UPS (uninterrupted power supply).,

The inverter may comprise a T-type three-level three phase inverter.

The inverter has a first DC link capacitor connected to the first DC link and a second DC link capacitor connected to the second DC link in series, and every three phases (a, b, c), a plurality of anti-parallel diodes and a plurality of A switch having a T-type three-level three-phase inverter configured to be connected between the first DC link and the second DC link; An output voltage detector for detecting a three-phase voltage output from the T-type three-level three-phase inverter; A command voltage generator configured to generate a command voltage V _{ref of} each phase by using a three-phase current and a grid voltage phase angle output from the T-type three-level three-phase inverter; A sequence generator for generating a PWM (Pulse Width Modulation) switching sequence by using a switching state of each phase in accordance with a position in a space voltage vector of each phase command voltage; A switch-on time calculator configured to obtain a switch-on time of each phase in the PWM switching sequence; The first DC link voltage (V _{d _top)} and the second DC link input voltage detection unit for detecting a difference between the voltage (V _{d _bot)} of the capacitors in the capacitor; A first direct current link capacitor and the second to control the voltage of the connection node of the neutral point (N) between the DC link capacitor, a first DC link capacitor voltage (V _{d _top)} and the second V voltage (the DC link capacitor _d of _{_bot} ) a switch-on time compensation unit configured to compensate for the switch-on time by calculating the switch-on time compensation time T _comp ; And a PWM generator for generating a PWM switching sequence applied to the plurality of switches of each phase with a compensated switch on time of each phase.

When the voltage of the first DC link capacitor is greater than the voltage of the second DC link capacitor, the switch on time compensator may add the compensation switch on time to the switch on time of each phase to increase the switch on time of each phase. If the voltage of the DC link capacitor is less than the voltage of the second DC link capacitor, the switch on time of each phase may be reduced by subtracting the compensation switch on time of each phase.

If the voltage of the first DC link capacitor is greater than the voltage of the second DC link capacitor, the compensation switch on time of each phase may be greater than zero (T _comp > 0), if the voltage of the first DC link capacitor is less than the voltage of the second DC link capacitor, the switch-on time of each phase may be less than zero (T _comp <0).

The compensation switch on time T _comp may be determined by the following equation.

Here, _N i _{_gen} is determined by the equation below,

i _1st to i _4th are the neutral currents in each switching sequence (i _1st = i _4th ), T _s is the total time of a total of seven switching sequences, and T _max is the five switches for the neutral point voltage (V _aN ) on a On time, T _mid is three switch on times for the neutral point voltage (V _bN ) on b, T _min is one switch on time for the neutral voltage voltage (V _cN ) on c

A compensation switch-on time of each phase (T _{aj_ comp,} T _{_ comp bj, cj _comp} T) can be determined by the equation below.

Where T _aj , T _bj , T _cj are the switch-on times of each phase, and j is the switch number of each phase.

The present invention provides a variety of operating modes (e.g., a first mode of turn-on and peak power generation of a photovoltaic module, a second mode of grid-off, a third mode of furnace battery, a fourth mode of night, night and grid-off of Small hybrid energy storage system having a fifth mode, a night mode, and a sixth mode of using a UPS).

The present invention can maintain the voltage at the neutral point uniformly by adding a simple algorithm without additional circuit, and thus has high efficiency, low THD (Total Harmonic Distortion), low switch stress, and small T-type 3-level 3 A hybrid energy storage system with a phase inverter is provided.

1 is a schematic diagram showing the overall configuration of a hybrid energy storage system according to an embodiment of the present invention.
2A and 2B are schematic diagrams showing the configuration of the hybrid energy storage system and the configuration of the hybrid inverter according to the embodiment of the present invention.
3A-3F are schematic diagrams illustrating various modes of operation of a hybrid energy storage system according to an embodiment of the invention.
4 is a schematic diagram showing the configuration of a T-type three-level three-phase inverter in a hybrid energy storage system according to an embodiment of the present invention.
5 is a schematic diagram showing 27 spatial voltage vectors of a T-type three-level three-phase inverter.
6 is a schematic diagram showing the state of the neutral point (N) voltage according to the switching state of each phase of the T-type three-level three-phase inverter in the hybrid energy storage system according to an embodiment of the present invention.
FIG. 7 is a schematic diagram illustrating a case where the command voltage Vref is located in sector I. FIG.
FIG. 8 is a schematic diagram showing a center-aligned PWM switching sequence when the reference voltage is located on the spatial voltage vector as shown in FIG.
9 is a schematic diagram illustrating a combination of a P-type and N-type switching state in the center-aligned PWM switching sequence of FIG. 8.
FIG. 10 is a schematic diagram illustrating neutral point current calculation during one period in the center-aligned PWM switching sequence of FIG. 8.
FIG. 11 is a schematic diagram illustrating compensated switch on-time according to a neutral point voltage in the center-aligned PWM switching sequence of FIG. 8.
12A, 12B, and 12C illustrate a neutral voltage control algorithm of a T-type three-level three-phase inverter, a P-type switching state, and an N-type switching state in a hybrid energy storage system according to an embodiment of the present invention. A schematic diagram showing the output line voltage.

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

The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art, and the following examples can be modified in many different forms, and the scope of the present invention is as follows. It is not limited to an Example. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art.

In addition, in the following drawings, the thickness or size of each layer is exaggerated for convenience and clarity of description, the same reference numerals in the drawings refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. In addition, the term "connected" in this specification means not only the case where the A member and the B member are directly connected, but also the case where the A member and the B member are indirectly connected by interposing the C member between the A member and the B member. do.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise, include" and / or "comprising, including" means that the features, numbers, steps, actions, members, elements, and / or groups thereof mentioned. It is intended to specify the existence and not to exclude the presence or addition of one or more other shapes, numbers, operations, members, elements and / or groups.

Although the terms first, second, etc. are used herein to describe various members, parts, regions, layers, and / or parts, these members, parts, regions, layers, and / or parts are defined by these terms. It is obvious that not. These terms are only used to distinguish one member, part, region, layer or portion from another region, layer or portion. Accordingly, the first member, part, region, layer or portion, which will be described below, may refer to the second member, component, region, layer or portion without departing from the teachings of the present invention.

Terms relating to spaces such as "beneath", "below", "lower", "above", and "upper" are associated with one element or feature shown in the figures. It can be used for easy understanding of other elements or features. Terms related to this space are for easy understanding of the present invention according to various process conditions or use conditions of the present invention, and are not intended to limit the present invention. For example, if an element or feature in the figures is inverted, the element or feature described as "bottom" or "bottom" will be "top" or "top". Thus, "below" is a concept encompassing "top" or "bottom".

In addition, the controller (controller) and / or other related devices or components according to the present invention may be implemented using any suitable hardware, firmware (e.g., on-demand semiconductor), software, or a suitable combination of software, firmware and hardware. Can be. For example, various components of a controller (controller) and / or other related device or component according to the present invention may be formed on one integrated circuit chip or on a separate integrated circuit chip. In addition, various components of the controller (controller) may be implemented on a flexible printed circuit film, and may be formed on the same substrate as the tape carrier package, printed circuit board, or the controller (controller). In addition, the various components of the controller (controller) may be, in one or more computing devices, a process or thread running on one or more processors, which execute computer program instructions to perform the various functions described below. And interact with other components. Computer program instructions are stored in memory that can be executed in a computing device using a standard memory device, such as, for example, random access memory. Computer program instructions may also be stored in other non-transitory computer readable media, such as, for example, a CD-ROM, flash drive, or the like. In addition, those skilled in the art will appreciate that the functions of various computing devices may be combined with one another, integrated into one computing device, or that the functionality of a particular computing device is not limited to one or more other computing devices without departing from the exemplary embodiments of the invention. It should be recognized that they can be distributed among the fields.

In one example, a controller (controller) according to the present invention typically comprises a central processing unit, a mass storage device such as a hard disk or a solid state disk, a volatile memory device, an input device such as a keyboard or mouse, an output device such as a monitor or a printer. Can be run on a commercial computer.

1 is a schematic diagram showing the overall configuration of a hybrid energy storage system 100 according to an embodiment of the present invention.

As shown in FIG. 1, the hybrid energy storage system 100 may supply power received from the solar power module 201 and / or the grid 202 to the home appliance 203 and / or the battery 120. have. In addition, the hybrid energy storage system 100 may supply power generated from the photovoltaic module 201 to the grid 202. In addition, the hybrid energy storage system 100 may receive power from the grid 202 to charge the battery 120. Various modes (six modes) of the hybrid energy storage system 100 will be described in detail below.

The photovoltaic module 201 may first supply generated power to the hybrid energy storage system 100. The hybrid energy storage system 100 may supply the generated power to the battery 120, the home appliance 203, and the grid 202.

The grid 202 may include a power plant, substation, power transmission line, or the like. When the grid 202 is in a steady state, the grid 202 may power the energy storage system 100 to power the home appliance 203 and / or the battery 120. The grid 202 may also be powered from the energy storage system 100. If the grid 202 is in an abnormal state (eg, in the event of a ground fault or power failure), the power supply from the grid 202 to the energy storage system 100 may be interrupted, and from the energy storage system 100 Power supply to grid 202 may also be interrupted.

The household appliance 203 may consume the power produced by the solar power module 201, the power stored in the battery 120, and / or the power supplied from the grid 202.

The hybrid energy storage system 100 may store the power generated by the photovoltaic module 201 in the battery 120 and supply the generated power to the grid 202. The hybrid energy storage system 100 may supply power stored in the battery 120 to the grid 202 or store power supplied from the grid 202 in the battery 120. In addition, when the grid 202 is in an abnormal state, for example, when a power failure occurs, the hybrid energy storage system 100 may supply power to the home appliance 203 by performing an uninterruptible power supply (UPS) operation. In addition, the hybrid energy storage system 100 may supply power generated by the photovoltaic module 201 or power stored in the battery 120 to the home appliance 203 even when the grid 202 is in a normal state.

The power conversion system (PCS) 130 is a form suitable for the grid 202, the home appliance 203, and the battery 120 by receiving power supplied from the photovoltaic module 201, the grid 202, and the battery 120. Can be converted to The PCS 130 performs power conversion to the input / output terminal and power conversion from the input / output terminal, where the power conversion may be DC / AC conversion and conversion between the first voltage and the second voltage. The PCS 130 may supply the converted power to an appropriate destination according to the operation mode under the control of the EMS 135.

The PCS 130 may include a power converter 131, a DC link unit 132, an inverter 133, and a converter 134.

The power converter 131 may be a power converter connected between the solar power module 201 and the DC link unit 132. The power converter 131 may transfer the power generated by the photovoltaic module 201 to the DC link unit 132. The output voltage from the power converter 131 may be a DC link voltage.

The power converter 131 may include a converter for converting the voltage level of the DC power of the photovoltaic module 201 to the voltage level of the DC power of the DC link unit 132. In particular, the power conversion unit 131 performs the MPPT control to maximize the power point tracking (Maximum Power Point Tracking) so as to obtain the maximum power produced by the photovoltaic module 201 according to the change in the amount of solar radiation, temperature, etc. It may include a converter. The power converter 131 may stop the operation in order to minimize the power consumption when there is no power generated from the photovoltaic module 201.

The DC link voltage may become unstable due to an instantaneous voltage drop in the photovoltaic module 201 or the grid 202, a sudden change in the home appliance 203, or a high load demand. However, the DC link voltage must be stabilized for normal operation of the converter 134 and the inverter 133. The DC link unit 132 is connected between the power converter 131 and the inverter 133 to maintain a constant DC link voltage. As the DC link unit 132, for example, two or more large capacitors may be included.

The inverter 133 is a power converter connected between the DC link unit 132 and the first switch 171. The inverter 133 may include an inverter that converts a DC output voltage from the DC link unit 132 into an AC voltage of the grid 202 in the discharge mode. In addition, the inverter 133 may include a rectifier circuit for rectifying the AC voltage of the grid 202, converting the DC voltage into a DC link voltage, and outputting the power to the battery 120 in the charging mode in the battery 120. have. That is, the inverter 133 may be a bidirectional inverter in which directions of input and output may be changed.

The inverter 133 may include a filter for removing harmonics from the AC voltage output to the grid 202. The inverter 133 may also include a phase locked loop (PLL) circuit for synchronizing the phase of the AC voltage output from the inverter 133 and the phase of the AC voltage of the grid 202 to suppress reactive power loss. . In addition, the inverter 133 may perform functions such as limiting voltage fluctuation range, power factor improvement, DC component removal, and protection against transient phenomena. When not in use, inverter 133 may shut down to minimize power consumption.

The converter 134 may be a power conversion device connected between the DC link unit 132 and the battery 120. The converter 134 may include a DC-DC converter that converts a voltage of power output from the battery 120 into a DC link voltage for the inverter 133 in the discharge mode. In addition, the converter 134 may include a DC-DC converter that converts the voltage of the power output from the power converter 131 or the inverter 133 into the voltage of the battery 120 in the charging mode. That is, the converter 134 may be a bidirectional converter 134 in which the directions of the input and the output may be changed. When the converter 134 is not used for charging or discharging the battery 120, the converter 134 may be stopped to minimize power consumption.

The EMS (Energy Monitoring System) 135 monitors the status of the photovoltaic module 201, the grid 202, the battery 120, and the home appliance 203, and according to the monitoring result, the power converter 131, Operations of the inverter 133, the converter 134, the battery 120, the first switch 171, and the second switch 172 may be controlled. The EMS 135 determines whether a power failure occurs in the grid 202 or whether a ground fault has occurred, whether power is generated in the photovoltaic module 201, or when power is generated in the photovoltaic module 201. The amount of power generated, the state of charge of the battery 120, the amount of power consumed by the home appliance 203, the time can be monitored. In addition, the EMS 135 sets a priority for the household electrical appliance 203 when there is not enough power to be supplied to the household electrical appliance 203, such as a power failure in the grid 202, for example. The home appliance 203 may be controlled to power a high powered device.

The first switch 171 and the second switch 172 are connected in series between the inverter 133 and the grid 202, and performs the on / off operation under the control of the EMS 135 to the solar power module ( Control the flow of current between 201 and grid 202. The first switch 171 and the second switch 172 may be turned on / off according to the states of the photovoltaic module 201, the grid 202, and the battery 120.

For example, in order to supply power of the grid module 202 to the battery 120, to supply power of the solar power module 201 and / or battery 120 to the home appliance 203, the first switch ( 171) is turned on. To supply power of the solar power module 201 and / or battery 120 to the grid 202 or to supply power of the grid 202 to the household electrical appliance 203 and / or the battery 120. 2 Switch 172 is turned on. As the first switch 171 and the second switch 172, a switching device such as a relay that can withstand a large current may be used.

When a ground fault or power failure occurs in the grid 202, the second switch 172 is turned off and the first switch 171 is turned on. That is, while supplying power from the photovoltaic module 201 and / or battery 120 to the home appliance 203, the power supplied to the home appliance 203 is prevented from flowing to the grid 202. The hybrid energy storage system 100 is disconnected from the grid 202 where a ground fault or power failure has occurred to prevent power supply to the grid 202. This makes it possible to prevent an accident, such as a worker working on a power line or the like of the grid 202, for example, repairing a power failure of the grid 202, by electric power from the hybrid energy storage system 100, or the like.

The battery 120 receives and stores power from the photovoltaic module 201 and / or grid 202 and supplies power to the home appliance 203 or the grid 202. The battery 120 may include a portion for storing power and a portion (eg, a battery monitoring system) for controlling and protecting the power.

In addition, in the embodiment of the present invention, the EMS 135 may control the air conditioning units 141 and 151 and the fire extinguishing units 142 and 152. The air conditioning units 141 and 151 may include a temperature sensor, a condensation sensor, a humidity sensor, a cooler, a heater, and the like. Therefore, the battery 120, the PCS 130, the EMS 135, and the like may be controlled to the optimum air conditioning state by the air conditioning units 141 and 151, respectively. In addition, the fire extinguishing units 142 and 152 may include a flame sensor, a heat sensor, a smoke sensor, a fire extinguishing device (eg, HCFC-123 gas, CO 2 gas, etc.). Therefore, the battery 120, the PCS 130, and the EMS 135 may be protected from fire by the fire extinguisher, respectively.

In addition, the embodiment of the present invention may include a configuration in which the EMS 135 is connected to the central management server 204 and the mobile terminal 205 through the Internet network 203. For example, when a ground fault or power failure occurs, an abnormality occurs in air conditioning, or a fire occurs, the EMS 135 may transmit it to the central management server 204 and the mobile terminal 205 in real time.

2A and 2B are schematic views showing the configuration of the hybrid energy storage system 100 and the configuration of the hybrid inverter 133 according to the embodiment of the present invention. 2A and 2B show only the main components of FIG. 1 separately for easy understanding of the present invention.

As shown in FIG. 2A, according to an embodiment of the present invention, the hybrid energy storage system 100 including the battery 120 is electrically connected to the photovoltaic module 201, the grid 202, and the home appliance 203. In addition, as shown in Figure 2b, the inverter 133 may include a T-type three-level three-phase inverter, the battery 120, EMS (135), PCS (130) based on this And the grid 202. In addition, the inverter 133 may include a BMS matching unit, an external interface, an operation command unit, an HMI, etc. In addition, the inverter 133 may control PQ, PLL, LVRT, and neutral point. You can perform the operation.

Hybrid energy storage system 100 according to an embodiment of the present invention can have a large six operating modes, which will be described sequentially. Here, the control subject of the operation mode may be the EMS 135, as described above, by controlling the converter 134, the inverter 133, the first switch 171, the second switch 172, etc., 6 There are four modes of operation that can be implemented.

3A-3F are schematic diagrams illustrating various modes of operation (operation mode or operation mode) of the hybrid energy storage system 100 according to an embodiment of the present invention.

As shown in FIG. 3A, in the first operation mode, the EMS 135 controls the converter 134 during the generation of the photovoltaic module 201 during the day to charge the battery 120 with DC power, and the inverter 133 may be controlled to supply AC power to the home appliance 201 and the grid 202. At this time, the EMS 135 turns on the first switch 171 and the second switch 172.

As shown in FIG. 3B, in the second operating mode, the EMS 135 controls the converter 120 during the day of power generation of the photovoltaic module 201 and the off-grid of the grid 202 to control the battery 120. The AC power may be supplied to the home appliance 201 by charging with DC power and controlling the inverter 133. At this time, the EMS 135 turns off the second switch 172 so that power is not supplied to the grid 202.

As shown in FIG. 3C, in the third operation mode, the EMS 135 controls the converter 134 during the generation of the photovoltaic module 201 during the day without recharging the battery 120 (for example, the battery 120 may not be mounted) The inverter 133 may be controlled to supply AC power to the home appliance 201 and the grid 202. At this time, the EMS 135 turns on the first and second switches 171 and 172.

As shown in FIG. 3D, in the fourth operation mode, the EMS 135 controls the converter 134 and the inverter 133 during the non-power generation of the photovoltaic module 201 at night to power the battery 120. By converting, AC power can be supplied to the home appliance 201. At this time, the EMS 135 turns on the first and second switches 171 and 172.

As shown in FIG. 3E, in the fifth operation mode, the EMS 135 controls the converter 134 and the inverter 133 when the grid 202 is off at night and converts power of the battery 120 to the home appliance. AC power can be supplied to 201. At this time, the EMS 135 turns off the second switch 172.

As shown in FIG. 3F, in the sixth operation mode, the EMS 135 controls the inverter 133 and the converter 134 to charge the battery 120 with the power of the grid 202 in advance, thereby charging the battery 120. Can be used as an uninterrupted power supply (UPS). Thus, EMS 135 turns off second switch 172.

4 is a schematic view showing the configuration of the T-type three-level three-phase inverter 133 in the hybrid energy storage system 100 according to an embodiment of the present invention, Figure 5 is a 27 of the T-type three-level three-phase inverter Figure 6 is a schematic diagram showing an open space voltage vector, Figure 6 is a schematic diagram showing the state of the neutral point (N) voltage according to the switching state of each phase of the T-type three-level three-phase inverter in the hybrid energy storage system according to an embodiment of the present invention 7 is a schematic diagram illustrating a case where the command voltage Vref is located in sector I, and FIG. 8 is a center-aligned PWM when the command voltage is located on a space voltage vector as shown in FIG. 7. 9 is a schematic diagram illustrating a switching sequence, FIG. 9 is a schematic diagram illustrating a combination of a P-type and N-type switching state in the center-aligned PWM switching sequence of FIG. 8, and FIG. 10 is a center-aligned diagram of FIG. 8. PWM switching FIG. 11 is a schematic diagram illustrating a neutral current calculation for one period in a sequence, and FIG. 11 is a schematic diagram illustrating compensated switch on-time according to a neutral point voltage in the center-aligned PWM switching sequence of FIG. 8.

As shown in FIG. 4, the hybrid energy storage system 100 according to an exemplary embodiment of the present invention includes a T-type three-level three-phase inverter 133, an input voltage detector 133a, an output voltage detector 133b, and a command. The voltage generator 133c, the sequence generator 133d, the switch-on time calculator 133e, and the PWM generator 133g may be included.

The T-type three-level three-phase inverter 133 includes a first DC link capacitor C1 connected to the first DC link and a second DC link capacitor C2 connected to the second DC link. , b, c), each phase consists of a plurality of anti-parallel diodes and switches. The first DC link capacitor C1 and the second DC link capacitor C2 are connected in series.

Phase A of the three phases is composed of antiparallel diodes Da1, Da2, Da3, Da4 and switches Sa1, Sa2, Sa3, Sa4, and the switch Sa1 and antiparallel diode Da1 are connected to the first DC link, and the second The switch Sa4 and the antiparallel diode Da4 are connected to the DC link, and are connected between the neutral point N, which is a connection node of the first DC link capacitor C1 and the second DC link capacitor C2, and a connection node of the switch Sa1 and the switch Sa4. , The switches Sa2, Sa3 and the antiparallel diodes Da2, Da3 are connected.

Among the three phases, b phase is composed of antiparallel diodes Db1, Db2, Db3, and Db4 and switches Sb1, Sb2, Sb3, and Sb4, and a switch Sb1 and an antiparallel diode Db1 are connected to a first DC link, and a second The switch Sb4 and the antiparallel diode Db4 are connected to the DC link, and the switches Sb2 and Sb3 and the antiparallel diodes Db2 and Db3 are connected between the neutral point N and the connection nodes of the switches Sb1 and Sb4.

The c phase of the three phases is composed of antiparallel diodes (Dc1, Dc2, Dc3, Dc4) and switches (Sc1, Sc2, Sc3, Sc4), and the switch Sc1 and the antiparallel diode Dc1 are connected to the first DC link, and the second The switch Sc4 and the antiparallel diode Dc4 are connected to the DC link, and the switches Sc2 and Sc3 and the antiparallel diodes Dc2 and Dc3 are connected between the neutral point N and the connection node of the switch Sc1 and the switch Sc4.

The input voltage detector 133a detects the voltage Vd_top of the first DC link capacitor C1 and the voltage Vd_bot of the second DC link capacitor C2, respectively, and calculates an unbalanced voltage difference to switch on time. It transfers to the compensation part 133f. The calculation of the voltage difference between the voltage of the first DC link capacitor C1 and the second DC link capacitor C2 of the input voltage detector 133a is performed by the sequence generator 133d before and after the operation of the command voltage generator 133c. Before and after, before and after the operation of the switch on time calculator 133e, and before and after the operation of the switch on time compensator 133f, the present invention is not limited thereto.

At this time, the magnitude of the voltage of the first DC link capacitor C1 and the voltage of the second DC link capacitor C2 depends on the switching state of each switch. Referring to FIG. 5, the T-type three-level three-phase inverter 133 has 27 spatial voltage vectors, which are zero, small, medium, Can be divided into large voltage vectors. Among these, the vectors affecting the neutral point (N) voltage are small voltage vectors (POO / ONN, PPO / OON, OPO / NON, OPP / NOO, OOP / NNO, POP / ONO) and intermediate voltage vectors (PON, OPN, NPO, ONP, PNO) and zero voltage vectors (PPP, NNN, OOO) and large voltage vectors (PNP, PPN, NPP, NNP, PNN) are the neutral voltage fluctuations because the inverter output is not connected to the DC link neutral point (N). Does not affect At this time, for example, PPP sequentially represents a switching state of a phase, a switching state of b phase, and a switching state of c phase from left to right. That is, the first P indicates that the switching state of the switches included in phase a is P type, the second P indicates that the switching state of the switches included in phase b is P type, and the third P is included in phase c. Indicates that the switching state of the switched switches is P type. The control of the switching states of the switches included in the a phase, the switches included in the b phase, and the switches included in the c phase may be performed according to a signal generated by the PWM generator 133g.

Small voltage vectors (POO / ONN, PPO / OON, OPO / NON, OPP / NOO, OOP / NNO, POP / ONO) can be divided into P type small voltage vector and N type small voltage vector according to the switching state. P type small vector vectors (POO, PPO, OPO, OPP, OOP, POP) are cases that include P and O states in a small vector switching combination, and N type small voltage vectors (ONN, OON, NON, NOO, NNO, ONO) is a case including the N and O states. And a pair of P type and N type small voltage vectors (POO / ONN, PPO / OON, OPO / NON, OPP / NOO, OOP / NNO, POP / ONO) that have redundancy each have voltage level but Are the opposite of each other. Therefore, the voltage fluctuation at the neutral point is also reversed.

This will be described in detail with reference to FIG. 6. 6 (a) shows a case of a zero voltage vector, and since the output terminal of the T-type three-level three-phase inverter 133 is not connected to the DC link neutral point N, the neutral point N does not affect the voltage fluctuation. Indicates. 6 (e) shows the case of a large voltage vector, and since the output terminal of the T-type three-level three-phase inverter 133 is not connected to the DC link neutral point N, the neutral point N does not affect the voltage fluctuation. Indicates. 6 (b) shows a case of a P-type small voltage vector, and since the output terminal of the T-type three-level three-phase inverter 133 is connected to the upper end of the DC link and the neutral point N, the current iN enters the neutral point direction. Increase the capacitor voltage (Vd_bot) at the bottom. 6 (c) shows a case of an N type small voltage vector, and since the output terminal of the T type 3-level three-phase inverter 133 is connected to the neutral point N and the lower end of the DC link, current iN flows out of the neutral point. Reduce the capacitor voltage (Vd_bot) at the bottom. 3 (d) shows the case of the intermediate voltage vector. Since the output terminal of the T-type three-level three-phase inverter 133 is connected to the neutral point N, the neutral point voltage is changed according to the current direction of the phase connected to the neutral point N. Increase or decrease

That is, the T-type three-level three-phase inverter 133 of the present invention has three switching states (P, N, O) for each phase. The switching state P represents a state in which the switches Sx1 and Sx2 are turned on and Sx3 and Sx4 are turned off in each phase, and the pole voltage is Vd / 2 [V]. On the other hand, the N state represents a state in which the switches Sx1 and Sx2 are turned off and Sx3 and Sx4 are turned on in each phase, and the pole voltage is -Vd / 2 [V]. The switching state O represents a state in which the switches Sx2 and Sx3 are turned on and Sx1 and Sx4 are turned off in each phase, and the pole voltage is 0 [V]. Table 1 shows the on / off states of the switches Sa1, Sa2, Sa3, and Sa4 in P, O, and N.

TABLE 1

The small voltage vector of P type (switches Sx1 and Sx2 are turned on) increases the neutral point voltage as shown in FIG. 6B, and the small voltage vector of N type (switches Sx3 and Sx4 is turned on) is shown in FIG. As shown in (c), the neutral voltage is reduced. The intermediate voltage vector increases or decreases the neutral point voltage according to the current direction of the phase connected to the neutral point, as shown in FIG.

The command voltage generator 133c generates a command voltage of each phase using the three-phase current and the grid voltage phase angle output from the T-type three-level three-phase inverter 133. At this time, the command voltage generation unit 133c converts the three-phase current into a rotational coordinate system and converts the current of the d (invalid) axis of the three-phase current converted into the rotational coordinate system into a command voltage on the d-axis ( Not shown), the q-axis command voltage converting unit for converting the current of the q-axis (effective) axis of the three-phase current converted to the rotational coordinate system into the q-axis command voltage, the output voltage and the q-axis command voltage converter of the d-axis command voltage converter Synchronous coordinate conversion unit (not shown) for converting the output voltage into the q-axis command voltage and the d-axis command voltage of the synchronous coordinate system, respectively, the q-axis command voltage and d-axis command voltage of the fixed coordinate system Fixed coordinate system converter (not shown) for converting and outputting the axis command voltage, and command voltage generator 133c for obtaining the command voltage of each phase of the three-phase coordinate system using the q-axis command voltage and the d-axis command voltage of the fixed coordinate system ( Not shown).

In one example, the d-axis command voltage converter includes a d-axis PI controller (not shown). The d-axis PI controller obtains a d-axis current error value Ide_err, which is a difference between the d-axis current red_Ide and the actual d-axis current Ide, and obtains a d-axis current error value Ide_err, an I controller gain Ki and The d-axis I controller output value (ref_Vde_fb_intg) is obtained by multiplying all system control cycles (Tsamp), and the d-axis I controller output value (ref_Vde_fb_intg) is multiplied by the value obtained by multiplying the d-axis current error value (Ide_err) and the P controller gain (Kp). In addition, the d-axis command voltage ref_Vde_fb is output. The q-axis command voltage converter includes a q-axis PI controller (not shown). The q-axis PI controller obtains the q-axis current error value Iqe_err, which is the difference between the q-axis current red_Iqe and the actual q-axis current Iqe, and calculates the q-axis current error value Iqe_err, I controller gain Ki and the system. Multiply all control periods Tsamp to obtain the q-axis I controller output value (ref_Vqe_fb_intg), and multiply the q-axis current error value (Iqe_err) and the P controller gain (Kp) by the q-axis I controller output value (ref_Vqe_fb_intg). The q-axis command voltage ref_Vqe_fb is output.

The dynamic coordinate system converting unit converts the d-axis command voltage (ref_Vde_fb) on the rotational coordinate system to the d-axis command voltage (ref_Vde) on the synchronous coordinate system and outputs it, and converts the q-axis command voltage (ref_Vqe_fb) on the rotational coordinate system to the q-axis command voltage ( ref_Vqe) and output it.

The fixed coordinate system converts the d-axis command voltage (ref_Vde) and the q-axis command voltage (ref_Vqe) of the synchronous coordinate system into the d-axis command voltage (ref_Vds) and the q-axis command voltage (ref_Vqs) of the fixed coordinate system using Equation 1 below. To convert.

[Equation 1]

In this case, Angle represents the system voltage phase.

The command voltage generation unit 133c applies the q-axis command voltage and the d-axis command voltage of the fixed coordinate system to Equation 2 below to obtain a command voltage of each phase of the three-phase coordinate system.

[Equation 2]

At this time, ref_Va represents the a-phase command voltage of the three-phase coordinate system, ref_Vb represents the b-phase command voltage of the three-phase coordinate system, and ref_Vc represents the c-phase command voltage of the three-phase coordinate system.

The sequence generator 133d may use a pulse width modulation to control the neutral point (N) voltage by using switching states of respective phases according to positions of the command voltage generated by the command voltage generator 133c according to positions in the spatial voltage vector. Create a switching sequence. In this case, the PWM switching sequence may be made using switching states in which the command voltage generated by the command voltage generator 133c exists at a position on the space voltage vector.

On the other hand, referring to Figure 7, when the command voltage (Vref) is located in one sector (Sector I), the PWM switching sequence by the four switching states [OON], [PON], [PPN], [PPO] It can be seen that it is composed of [OON]-[PON]-[PPN]-[PPO]-[PPN]-[PON]-[OON].

8 and 9 show a PWM switching sequence when the command voltage is located on the space voltage vector as shown in FIG. The P type small voltage vector and the N type small voltage vector generate the same output line voltage, but the opposite directions of the current flowing to the neutral point are applied to each other so that the neutral voltage can be maintained uniformly. This should be the same.

The switch on time calculation unit 133e calculates the switch on time of each phase.

For example, when the command voltage (Vref) is in sector 1, region 1, the voltage of each phase can be calculated as follows.

Calculated from Switch On Time

[Equation 3]

The KVL is calculated as follows.

[Equation 4]

[Equation 5]

Meanwhile, the phase voltage applied to the inverter load is as follows.

[Equation 6]

[Equation 7]

Here, the following Equation 8 can be obtained for the switch-on time from FIG. 8.

[Equation 8]

In addition, the switch on time can be calculated from Equation 8 as follows.

Tc1 , Tc2

Equation 8 may be derived from Tc1 = Tc2 = 0 and Equation 7 from Equation 8.

[Equation 9]

Ta1 , Ta2

If Van> 0, then Ta1 + Ta2> Ts, Van-Vcn> Vd / 2

From Equation 8

From equation (9)

이면, 위와 같은 방법으로

, In the same way as above

Tb1 , Tb2 (in the same way as above)

이면,

,

If,

,

이면,

If,

In this way, the switch-on time in six sectors (24 regions) can be calculated as follows.

Equation 10

As shown in Fig. 9, by setting the on-times of the P-type and N-type switching states to be the same within one period, the output current distortion can be reduced to favor the neutral point voltage balance.

[Equation 11]

Tc1 , Tc2

From the switching sequence of Figure 9, Tc1 = 0,

From Equation 11

Ta1 , Ta2

Ta2 = Ts from the switching sequence of FIG.

From Equation 11

Tb1 , Tb2

Tb2 = Ts from the switching sequence of FIG.

From Equation 11

In this way, when six sectors (24 regions) are applied, the switching on time may be calculated as in Equation 12 below.

[Equation 12]

10, the neutral voltage according to the switching operation is calculated as follows. For example, if you calculate the neutral current for one period, there are four independent sequences out of a total of seven switching sequences, each of which can be calculated by multiplying the neutral current and the on time (P type and N type). Same on time)

Neutral current iN is as follows.

If this is converted to a general expression, it is as follows.

As can be seen from the general formula and FIG. 10, it can be seen that the neutral point voltage is not stabilized.

A neutral point compensation method will be described with reference to FIG. 11.

First, the switch on time (Tcomp) is defined as follows.

It can be seen from the above equation that i4th and Tcomp affect the neutral point voltage.

Accordingly, an embodiment of the present invention changes Tcomp in proportion to Vd_bot-Vd_top as follows.

In this way, the compensated switch on time is as follows.

Finally, the compensated switch on time according to the neutral point voltage is as follows. Here, the blue dotted line means a case where the compensation switch on time is +, and the red dotted line means a case where the compensation switch on time is-.

As described above, the switch-on time calculator 133e obtains the switching-on time of each phase from the PWM switching sequence generated by the sequence generator 133d. For example, the switch on time calculator 133e calculates the switching on time of each phase in the PWM switching sequence.

In addition, as described above, the switch on time compensator 133f calculates each compensation time with respect to the switching on time of each phase calculated by the switch on time calculator 133e. As described above, the compensation time may be +, 0 or-.

As described above, the PWM generator 133g compensates the switch-on time of each phase by using the difference between the voltage of the first DC link capacitor C1 and the voltage of the second DC link capacitor C2, and compensates each phase. The switch on time transforms the PWM switching sequence and applies it to multiple switches in each phase.

At this time, the PWM generator 133g compares the magnitude of the voltage of the first DC link capacitor C1 with the magnitude of the voltage of the second DC link capacitor C2 and compensates for the switch-on time of each phase according to the comparison result.

 That is, when the first DC link capacitor C1 voltage Vd_top is greater than the second DC link capacitor C2 voltage Vd_bot, the PWM generator 133g adds a switch compensation time to each phase switch on time, Compensate for switch on time. As a result, the voltage of the first DC link capacitor C1 is reduced.

On the other hand, if the voltage Vd_top of the first DC link capacitor C1 is smaller than the voltage Vd_bot of the second DC link capacitor C2, the PWM generator 133g sets the switch compensation time to the switch-on time of each phase. Subtraction, to compensate for the switch-on time of each phase. As a result, the voltage of the second DC link capacitor C2 is reduced.

Through this process, when the command voltage Vref is in sector I as shown in FIG. 7, the PWM switching sequence for controlling the neutral point voltage can be obtained as shown in Table 1 above.

12A, 12B and 12C illustrate the use of the neutral point voltage control algorithm of the T-type three-level three-phase inverter 133, the use of the P-type switching state and the N of the hybrid energy storage system 100 according to the embodiment of the present invention. Schematic diagram of output line voltage when using a -type switching state.

As shown in FIG. 12A, when the neutral voltage control algorithm of the T-type three-level three-phase inverter 133 is used, Vd_bot = Vd_top (deviation of 0.5% or less), and thus no distortion occurs in the output line voltage. can see.

As shown in FIG. 12B, when the neutral point voltage control algorithm of the T-type three-level three-phase inverter 133 is not used (when the P-type switching state is used), when Vd_bot> Vd_top, the distortion occurs in the output line voltage. Can be.

As shown in FIG. 12C, since the neutral point voltage control algorithm of the T-type three-level three-phase inverter 133 is not used (when using an N-type switching state), when Vd_bot <Vd_top, it is shown that distortion occurs in the output line voltage. Can be.

What has been described above is just one embodiment for implementing a hybrid energy storage system according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, the gist of the present invention Without departing from the technical spirit of the present invention to the extent that any person of ordinary skill in the art to which the present invention pertains various modifications can be made.

100; Hybrid energy storage system according to an embodiment of the present invention
120; A battery 130; Power Conversion System (PCS)
131; A power converter 132; DC link section
133; Inverter 133a; Input voltage detector
133b; An output voltage detector 133c; Command voltage generator
133d; A sequence generator 133e; Switch on time calculator
133f; A switch on time compensator 133g; PWM generator
134; Converter 135; Energy Monitoring System (EMS)
171; First switch 172; Second switch
201; Solar power module 202; grid
203; Home appliance 203; Internet network
204; Central management server 205; Mobile terminal

Claims (7)

A converter for converting and outputting power generated from the solar power module into direct current power; An inverter for converting and outputting power generated from the solar power module into AC power; A battery charged with DC power supplied from a converter; And an EMS controlling the converter and the inverter, wherein the EMS includes:
In the daytime, the solar cell module controls the converter to charge the battery with DC power, and the inverter controls the inverter to supply AC power to home appliances and the grid. A second operating mode that supplies AC power to home appliances by charging with DC power and controlling the inverter; a third operating mode that supplies AC power to home appliances and grid by controlling the inverter without charging the battery by controlling the converter;
The fourth operating mode of supplying AC power to home appliances by controlling the converter and inverter when the solar power module is not generating power at night, and controlling the converter and inverter when the grid is off, converting the battery power To operate in any one of the fifth operating mode of supplying AC power to home appliances, and the sixth operating mode of controlling the inverter and the converter to charge the power of the grid with the battery and use it as an uninterrupted power supply (UPS).
Inverter
The first DC link capacitor connected to the first DC link and the second DC link capacitor connected to the second DC link are connected in series, and every three phases (a, b, c), a plurality of anti-parallel diodes and a plurality of switches A T-type three-level three-phase inverter configured to be connected between the first DC link and the second DC link;
An output voltage detector for detecting a three-phase voltage output from the T-type three-level three-phase inverter;
A command voltage generator configured to generate a command voltage V _{ref of} each phase by using a three-phase current and a grid voltage phase angle output from the T-type three-level three-phase inverter;
A sequence generator for generating a PWM (Pulse Width Modulation) switching sequence by using a switching state of each phase in accordance with a position in a space voltage vector of each phase command voltage;
A switch-on time calculator configured to obtain a switch-on time of each phase in the PWM switching sequence;
A first DC link input voltage detection unit for detecting a difference between the voltage (V _{d_top)} and the second DC link voltage (V _{d_bot)} of the capacitors in the capacitor;
A first direct current link capacitor and the second DC link for controlling the voltage of a connection node that is a neutral point (N) between the capacitor, the first voltage of the DC link voltage of the capacitor (V _{d_top)} and the second DC link capacitor (V _{d_bot)} A switch-on time compensator configured to compensate for the switch-on time by calculating a switch-on time compensation time T _comp according to a difference of the difference; And
And a PWM generator for generating a PWM switching sequence applied to a plurality of switches of each phase with a compensated switch on time of each phase. delete delete The method of claim 1,
The switch on time compensation unit
If the voltage of the first DC link capacitor is greater than the voltage of the second DC link capacitor, the compensation switch on time is added to the switch on time of each phase to increase the switch on time of each phase,
If the voltage of the first DC link capacitor is less than the voltage of the second DC link capacitor, subtract the compensation switch on time from the switch on time of each phase to reduce the switch on time of each phase. The method of claim 4, wherein
If the voltage of the first DC link capacitor is greater than the voltage of the second DC link capacitor, the compensation switch on time of each phase is greater than zero (T _comp > 0),
If the voltage of the first DC link capacitor is less than the voltage of the second DC link capacitor, the switch-on time of each phase is less than zero (T _comp <0). The method of claim 4, wherein
The compensation switch on time (T _comp ) is determined by the following equation, hybrid energy storage system.

Here, i _{N _gen} is determined by the following equation,

i _1st to i _4th are the neutral currents in each switching sequence (i _1st = i _4th ), T _s is the total time of a total of seven switching sequences, and T _max is the five switches for the neutral point voltage (V _aN ) on a On time, T _mid is three switch on times for the neutral point voltage (V _bN ) on b, T _min is one switch on time for the neutral voltage voltage (V _cN ) on c The method of claim 6,
The compensated switch on time (T _{aj_comp} , T _{bj_comp} , T _{cj_comp} ) of each phase is determined by the following equation.

Where T _aj , T _bj , T _cj are the switch-on times of each phase, and j is the switch number of each phase.

Images