KR102171351B1 - Method for controlling parallel driving Power Conversion System module - Google Patents

Abstract

An embodiment of the present invention is a method for controlling a parallel operation of a modular PCS in which a PCS power control device controls a modular PCS in which a power conversion device (PCS) as a unit module is connected in parallel, an energy storage device (ESS) A battery charging rate calculation process of calculating a battery charging rate (SOC) of the battery provided in the battery; A load power calculation process of calculating load power, which is power required by the battery, based on the calculated battery charge rate (SOC); And a load sharing control process of controlling to uniformly output from each modular PCS based on the calculated load power.

Description

Parallel operation control method of modular power conversion device {Method for controlling parallel driving Power Conversion System module}

The present invention relates to a method for controlling parallel operation of a modular power converter, and to a method for controlling parallel operation of a modular power converter for controlling a plurality of modular power converters connected in parallel.

In the conventional single modular power conversion system (PCS), a large current flows through a power switch element in a high power system, resulting in conduction loss proportional to the square of the current. In addition, there is a disadvantage in that the volume of the heat sink increases as the heat source is concentrated on the switch due to losses generated during switching.

Accordingly, the power conversion device (PCS) is configured as a parallel module as shown in Fig. 1 so that large-capacity power generation is possible and the customer can freely manufacture the desired capacity, so that the master module commands and controls the reference current of all slave modules. Driven in a way.

However, the existing Master-Slaver method does not require additional current detection, but since the Master module has to command the current control reference value to the Slave module, signal lines are required as many as the number of Slave modules, and the failure of the Master module affects the entire system. And the reliability decreases.

Therefore, there is a need for a new control method that has a simple controller structure, does not require additional current detection, and enables even load sharing to increase the reliability of the system.

Korean Patent Registration 10-1764586

The technical problem of the present invention is to equalize the output power from each module according to the load of the energy storage device (ESS) to charge the energy storage device (ESS) at high power density and high power conversion efficiency of the power conversion device (PCS). We propose a load sharing control technique that suppresses circulating current by distributing and increases efficiency.

An embodiment of the present invention is a method for controlling a parallel operation of a modular PCS in which a PCS power control device controls a modular PCS in which a power conversion device (PCS) as a unit module is connected in parallel, an energy storage device (ESS) A battery charging rate calculation process of calculating a battery charging rate (SOC) of the battery provided in the battery; A load power calculation process of calculating load power, which is power required by the battery, based on the calculated battery charge rate (SOC); And a load sharing control process of controlling to uniformly output from each modular PCS based on the calculated load power.

The process of calculating the battery charge rate may include a process of compensating an initial battery voltage for compensating an initial battery voltage according to temperature; And a battery charging rate tracking process of applying the initial voltage of the battery to a current integration method to follow the battery charging rate and calculating the battery charging rate.

In the battery initial voltage compensation process, V_ _{batt, init} is the initial battery voltage, V_ _n is the output voltage of the nth modular PCS, V_ _Ta is the voltage value changed by temperature, and V_ _Ra is the voltage decreased by the internal resistance of the battery. Value, T_ _BAT is the battery temperature, 25 is the room temperature 25℃, 0.1 is the gain value for calculating V_ _Ta ,

에 의해 배터리 초기전압인 V__batt,init이 산출됨을 특징으로 할 수 있다.

It may be characterized in that _{V_batt,init, which} is the initial voltage of the battery _, is calculated by.

The battery charge rate tracking process is when SOC_ _init is the initial value of SOC, V_ _{batt, init} is the initial battery voltage, V_ _batt,max is the maximum battery voltage, V_ _{batt, min} is the minimum battery voltage, and C_ _n is the nominal battery capacity. ,

에 의해 배터리 충전율(SOC)을 산출할 수 있다.

The battery charge rate (SOC) can be calculated by.

The load sharing control process, modular PCS power calculating step of calculating a P_ _n of each modular power PCS; A process of determining the number of modular PCSs supplied by using each of the modular PCS power P_ _n to determine the number N of the modular PCSs to supply load power; A power reference value calculation process of calculating a power reference value by dividing the number N of the modular PCS determined from the total amount of power of the entire modular PCS; And a power reference value control process of controlling and outputting the power reference value for the modular PCS determined to supply load power.

에 의해 P__n을 산출하거나, 또는 i__dc,n는 n번째 모듈 출력 전류, V__dc,n은 n번째 모듈 출력 전압, K는 상수라 할 때,

에 의해 P__n을 산출할 수 있다.The modular PCS power calculating process, P_ _Load the load power, N is referred to when the number of modular PCS,

P_ to calculate _n, or i_ _{dc, n} is the n-th module output current, _{dc V_, n} is the n-th module by the output voltage, when the K d is a constant,

By it can be calculated P_ _n.

According to an embodiment of the present invention, a modular power conversion device (PCS) is connected in parallel, so that thermal design is easy by using a low-rated element, and the size of a heat sink can be reduced.

In addition, according to an embodiment of the present invention, by operating several power conversion devices (PCS) in parallel, even if one module fails, it is possible to operate with the remaining modules, and by adding an extra module, a single power conversion device (PCS) ), the reliability of the system can be improved.

1 is an exemplary diagram of a conventional parallel-connected modular PCS.
2 is a block diagram of a system for controlling parallel operation of a modular PCS according to an embodiment of the present invention.
Figure 3 is a detailed picture provided with a modular PCS according to an embodiment of the present invention.
4 is a flowchart showing a method for controlling parallel operation of a modular PCS according to an embodiment of the present invention.
5 is an experimental graph showing the output power of each modular PCS when the parallel operation control of the modular PCS according to an embodiment of the present invention is performed.
6 is an experimental graph showing high efficiency even at a low load when parallel operation control of a modular PCS according to an embodiment of the present invention is performed according to an embodiment of the present invention.

Hereinafter, the advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and is provided to completely inform the scope of the invention to those of ordinary skill in the art to which the present invention belongs. As such, the invention is only defined by the scope of the claims. In addition, in describing the present invention, when it is determined that related known technologies may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

2 is a block diagram of a system for controlling parallel operation of a modular PCS according to an embodiment of the present invention, and FIG. 3 is a detailed diagram of a modular PCS according to an embodiment of the present invention.

The present invention applies the structure of a single modular power conversion system (PCS) having low efficiency under light load to a parallel operation method using several small-capacity PCS modules, so that a low-rated, high-speed device can be applied to a small power multi-system. By using it, it has high efficiency at full load.

To this end, in order to charge the ESS at the high power density and high power conversion efficiency of the PCS, the present invention evenly distributes the output power from each module according to the load of the ESS to suppress the circulating current and increase the efficiency. ) Perform control.

The parallel operation control system of the modular PCS of the present invention includes a modular PCS 100 having a parallel structure, an energy storage device 400 (ESS; Energy Storage System) composed of a battery, and a battery as shown in FIG. It includes a battery management device 300 to manage (BMS; Battery Management System), and a PCS power control device 200 for controlling each of the modular PCS (100).

In the modular PCS 100, a power conversion system (PCS) in a unit module type is connected in parallel. That is, as shown in FIG. 3, it is possible to have a modular AC/DC converter parallel structure that transmits grid power to the load.

The energy storage device 400 (ESS) is a system that stores energy and is used to store renewable energy and energy produced in the smart grid. The generated power is stored in a battery and then supplied when power is needed. It is a power system.

The battery management device 300 (BMS) provides a battery state value including a battery temperature (V _{_temp} ), a battery internal resistance (R _{_Total} ), and a battery current (i _{_BAT} ) to the PCS power control device 200.

The PCS power control device 200 is a device that controls a plurality of modular PCS 100 connected in parallel, and determines the number of modules operating according to the output power required by the load, and the output power corresponds to the load. It is determined according to the SOC of the battery. The circulating current generated during parallel operation performs load sharing control that equally controls the output voltage by equally sharing the power of each module. Hereinafter, a load sharing control method of the PCS power control apparatus 200 will be described with reference to FIGS. 4 to 6.

4 is a flowchart showing a method for controlling parallel operation of a modular PCS according to an embodiment of the present invention, and FIG. 5 is an output of each modular PCS when parallel operation control of the modular PCS according to an embodiment of the present invention is performed. An experimental graph showing power, and FIG. 6 is an experimental graph showing high efficiency even at a low load when parallel operation control of a modular PCS according to an embodiment of the present invention is performed according to an embodiment of the present invention.

The method for controlling parallel operation of the modular PCS of the present invention in which the PCS power control device 200 controls the modular PCS 100 in which the power conversion device (PCS) as a unit module is connected in parallel is shown in FIG. As described above, the battery charging rate calculation process (S410) for calculating the battery charging rate (SOC) of the battery provided in the energy storage device (ESS) and the load power, which is the power required by the battery, are calculated based on the calculated battery charging rate (SOC). The load power calculation process (S420) and a load sharing control process (S430) of controlling to uniformly output from each modular PCS 100 based on the calculated load power may be included. It will be described in detail below.

The battery charge rate calculation process (S410) is a process of calculating a battery charge rate (SOC) of a battery provided in the energy storage device (ESS).

The battery charge rate (SOC) is important information according to the charging and discharging of the battery and the use of the battery, and the battery charge rate (SOC) has a characteristic proportional to the voltage of the battery. As the SOC tracking method, the battery charging rate (SOC) can be tracked using the current integration method, which is a method of counting and predicting the amount of current flowing in and out of the battery. However, in tracking the battery charge rate (SOC) using the current integration method, the existing current integration method continues to generate an error when an initial value error occurs, so the present invention applies the improved current integration method to determine the battery charge rate (SOC). Calculate.

The SOC calculated as a voltage has different errors in voltage information sensed according to temperature, so the battery charge rate (SOC) is calculated after compensating for the voltage value according to the temperature.

To this end, the battery charge rate calculation process (S410) may include a battery initial voltage compensation process (S411) and a battery charge rate tracking process (S412).

The initial battery voltage compensation process (S412) is a process of compensating the initial battery voltage according to temperature. Therefore, V_ _n is the output voltage of the nth modular PCS(100), V_ _Ta is the voltage value changed by temperature, V_ _Ra is the voltage value dropped by the internal resistance of the battery, V_ _BAT is the battery voltage, I_ _BAT is the battery current. , T_ _BAT is such that the battery temperature, the room temperature 25 25 ℃, when 0.1 is referred to as gain value, the following equation 1 the battery voltage of the initial _{batt V_, init} by this calculation for V_ _Ta calculated.

The battery charge rate tracking process (S412) is a process of applying the initial voltage of the battery to the current integration method to follow and calculate the battery charge rate (SOC).

Therefore, when SOC_ _init is the initial SOC value, V_ _{batt, init} is the initial battery voltage, V_ _batt,max is the maximum battery voltage, V_ _batt,min is the battery minimum voltage, and C_ _n is the battery nominal capacity, the following [Equation 2] to calculate the battery charging rate (SOC).

The current integration method is a method of estimating the SOC of the battery based on the integration value of the initial SOC value and the sensed current. If the implementation is simple and the SOC initial value is accurately set and there is no error when sensing the current, the SOC estimation accuracy is very high. This is the most used method among battery SOC estimation methods. In the present invention, a more accurate SOC can be calculated using an equation that compensates for a voltage value according to temperature.

The load power calculation process (S420) is a process of calculating load power, which is the power required by the battery, based on the calculated battery charging rate (SOC). Therefore, if the battery charge rate (SOC) is high, the load power will be calculated high, and if the battery charge rate (SOC) is high, the load power will be calculated low.

The load sharing control process (S430) is a process of controlling to uniformly output from each modular PCS 100 based on the calculated load power. That is, based on SOC estimation, load sharing control is performed to evenly distribute the power required by the load.

The load sharing control process (S430) includes a modular PCS power calculation process (S431), a modular PCS supply number determination process (S432), a power reference value calculation process (S433), and a power reference value control process (S434). Can have.

Modular PCS power calculating process (S431) is a process of calculating the P_ _n of each modular power PCS. This modular PCS power calculation process can calculate the modular PCS power in two ways.

에 의해 P__n을 산출한다.One way to calculate modular PCS power is to determine the number of modules to operate after calculating the total power using the voltage and current of the load. That is, when P_ _Load is the load power, N is the number of modular PCS(100),

A P_ _n is calculated by.

에 의해 P__n을 산출할 수 있다. 여기서 i__dc,n과 V__dc,n은 하기의 [수학식 3]에 의해서도 산출 가능하다.Another way to calculate the modular PCS power is when i_dc _,n is the nth module output current, V_dc _,n is the nth module output voltage, and K is a constant,

By it can be calculated P_ _n. Here, i_ _dc,n and V_ _dc,n can also be calculated by the following [Equation 3].

Modular PCS supplied number determination process (S432) is a process of determining the number N of the modular PCS (100) using a P_ _n of each modular PCS power supply load power.

The power reference value calculation process (S433) is a process of calculating a power reference value by dividing the number N of the modular PCS 100 determined from the total amount of power of the total modular PCS 100.

The power reference value control process (S434) is a process of controlling and outputting a power reference value with respect to the modular PCS 100 determined to supply load power.

As a result, the present invention provides the output power required by the load through the load sharing control process (S430) consisting of a modular PCS power calculation process, a modular PCS supply number determination process, a power reference value calculation process, and a power reference value control process. It is possible to reduce the circulating current problem through equal power control for each module by determining and distributing the load sharing for each module evenly.

For example, referring to FIG. 5 showing the output power of each modular PCS 100 when applying the driving technique proposed in the present invention according to the load power, the modular PCS 100 is 100 [kW], When manufactured in 4 parallel, only the modular PCS(100) #1 operates in the 0kW~25kW section, and shares the power equally with the modular PCS(100)#2 in the 25kW~50kW section. Modular PCS(100) #1 ~ Modular PCS(100) #3 operate in the 50kW~75kW section, and in the 75kW~100kW section, the modular PCS(100) #4 operates up to 1/N equally in all stacks. It bears the load power. When the above algorithm is applied, only one stack is operated at a low load power, so that high efficiency can be obtained even at a low load as shown in FIG. 6.

Therefore, in the case of parallel operation control of the modular PCS 100 through the operation technique of the present invention, a solar PCS module capable of large-capacity power generation and freely manufacturing the capacity desired by consumers, increases in power consumption and high-quality power requirements. Accordingly, it can be implemented in a PCS used in the energy storage device 400 using a large-capacity battery, and in various modular PCS 100 in an application field using a battery pack composed of a plurality of battery modules as input power.

The embodiments in the description of the present invention described above are presented by selecting the most preferable examples to aid the understanding of those skilled in the art from among various possible examples, and the technical idea of the present invention is not necessarily limited or limited only by this embodiment. , Various changes and modifications, and other equivalent embodiments are possible within the scope of the technical spirit of the present invention.

100: Modular PCS
200:PCS power control device
300: BMS
400:ESS

Claims (4)

In the parallel operation control method of a modular PCS in which a PCS power control device controls a modular PCS in which a power conversion device (PCS) as a unit module is connected in parallel,
A battery charging rate calculation process of calculating a battery charging rate (SOC) of a battery provided in the energy storage device (ESS);
A load power calculation process of calculating load power, which is power required by the battery, based on the calculated battery charge rate (SOC); And
Includes; a load sharing control process for controlling to uniformly output from each modular PCS based on the calculated load power,
The process of calculating the battery charge rate,
An initial battery voltage compensation process for compensating an initial battery voltage according to temperature; And a battery charging rate tracking process of applying the initial voltage of the battery to a current integration method to follow the battery charging rate and calculating the battery charging rate.
The battery initial voltage compensation process,
V_ _batt,init is the initial voltage of the battery, V_ _n is the output voltage of the nth modular PCS, V_ _Ta is the voltage value changed by temperature, V_ _Ra is the voltage value dropped by the internal resistance of the battery, T_ _BAT is the battery temperature, When 25 is 25℃ at room temperature and 0.1 is the gain value for calculating V_ _Ta ,

A method for controlling parallel operation of a modular PCS, characterized in that _{V_batt,init, which} is an initial voltage of a battery _, is calculated by.
delete delete The method according to claim 1, wherein the battery charging rate tracking process,
SOC_ _init is the initial value of SOC, V_ _{batt, init} is the initial battery voltage, V_ _batt,max is the maximum battery voltage, V_ _batt,min is the minimum battery voltage, and C_ _n is the nominal battery capacity,

Parallel operation control method of modular PCS that calculates the battery charge rate (SOC) by.

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