Power conversion system

Abstract

The present application discloses a power conversion system, a micro control unit of which obtains a current charging ratio of a charging battery according to a state of charge signal, and obtains an external output power of the power conversion system according to a voltage and a current detected by a voltage and current meter. When the micro control unit detects that a commercial power is off-grid, the following steps are executed: judging whether the current charging ratio of the charging battery is greater than a first preset ratio; when it is judged that the current charging ratio of the charging battery is greater than the first preset ratio, judging whether the external output power is less than a first preset power; and when it is judged that the external output power is less than the first preset power, increasing a frequency of alternating current outputted from an alternating current power supply port of the power conversion system, so as to stop a solar power inverter coupled to the alternating current power supply port from outputting electric energy.

Description

Technical Field

[0001] This invention relates to a power conversion system, and more particularly to a power conversion system that can adjust the frequency of its output AC power according to the charge ratio of a rechargeable battery. Background Technology

[0002] A power conversion system (PCS) is a bidirectional power conversion inverter that can be used for both on-grid and off-grid energy storage applications. How to effectively operate a power conversion system has always been an important topic in this technical field. Summary of the Invention

[0003] In view of the problems in the prior art, the present invention provides a power conversion system to solve the above problems.

[0004] Therefore, the technical problem to be solved by the present invention is to provide a power conversion system comprising:

[0005] AC power port;

[0006] DC power port, coupled to a rechargeable battery;

[0007] A voltmeter and current meter, coupled to the AC power supply port, is used to detect the voltage and current output from the AC power supply port by the power conversion system; and

[0008] The microcontroller unit is used to control the operation of the power conversion system and receive state of charge signals from the rechargeable battery.

[0009] The microcontroller unit obtains the current charge percentage of the rechargeable battery based on the state-of-charge signal, and calculates the output power of the power conversion system based on the voltage and current detected by the voltmeter and ammeter.

[0010] When the microcontroller detects a power outage, it performs the following steps:

[0011] Determine whether the current charged percentage of the rechargeable battery is greater than a first preset percentage;

[0012] When it is determined that the current charge percentage of the rechargeable battery is greater than the first preset percentage, it is determined whether the external output power is less than the first preset power; and

[0013] When it is determined that the external output power is less than the first preset power, the frequency of the AC power output from the AC power source of the power conversion system is increased so that the solar photovoltaic converter coupled to the AC power source stops outputting power.

[0014] As an optional technical solution, when the microcontroller detects that the mains power is disconnected from the grid, and determines that the current charge ratio of the rechargeable battery is greater than the first preset ratio and the external output power is less than the first preset power, the power conversion system provides the power from the rechargeable battery to the load.

[0015] As an optional technical solution, when the microcontroller detects that the mains power is disconnected from the grid and determines that the current charging ratio of the rechargeable battery is equal to or less than the first preset ratio, the microcontroller maintains the frequency of the AC power output from the AC power port so that the solar photovoltaic converter continues to output power.

[0016] As an optional technical solution, when the microcontroller detects that the mains power is disconnected from the grid, and determines that the current charging ratio of the rechargeable battery is greater than the first preset ratio and the external output power is greater than or equal to the first preset power, the microcontroller maintains the frequency of the AC power output from the AC power port so that the solar photovoltaic converter continues to output power.

[0017] As an optional technical solution, when the microcontroller determines that the current charging ratio of the rechargeable battery is less than the second preset ratio, the microcontroller reduces the frequency of the AC power output from the AC power port so that the solar photovoltaic converter can resume output power, and the second preset ratio is less than the first preset ratio.

[0018] As an optional technical solution, when the microcontroller determines that the current charging ratio of the rechargeable battery is less than the second preset ratio, the solar photovoltaic converter resumes outputting electrical energy to the load. When the power consumption of the load is greater than the power output by the solar photovoltaic converter, the power conversion system outputs electrical energy to the load.

[0019] As an optional technical solution, when the microcontroller determines that the current charging ratio of the rechargeable battery is less than the second preset ratio, the solar photovoltaic converter resumes outputting power to the load. When the power output by the solar photovoltaic converter is greater than the power consumed by the load, the solar photovoltaic converter outputs additional power to the power conversion system to charge the rechargeable battery.

[0020] As an optional technical solution, when the microcontroller determines that the current charging ratio of the rechargeable battery is between the first preset ratio and the second preset ratio, the microcontroller sets the frequency of the AC power output from the AC power port to the cutoff frequency so that the solar photovoltaic converter stops outputting power, and the second preset ratio is less than the first preset ratio.

[0021] As an optional technical solution, the solar photovoltaic converter responds to the frequency of the AC power output from the AC power port in a two-stage manner: full output or no output.

[0022] As an optional technical solution, when the frequency of the AC power output from the AC power port is within a first range, the solar photovoltaic converter converts the electrical energy and then outputs the converted power at 100% efficiency; when the frequency of the AC power output from the AC power port is not within the first range, the solar photovoltaic converter stops outputting power.

[0023] Compared to existing technologies, the power conversion system of this invention, when its microcontroller detects grid disconnection, will cause the power conversion system to output AC frequency, thereby inducing the solar photovoltaic converter to generate electricity and feed it back to the grid without entering islanding protection. Its energy can supply the load and the power conversion system. The microcontroller will dynamically adjust the frequency of the AC output by the power conversion system according to the current charge ratio of the rechargeable battery and the positive or negative magnitude of the output power. Therefore, the overall power flow can be efficiently regulated.

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0025] Figure 1 This is a functional block diagram of a power conversion system and its coupled mains power, load, rechargeable battery, solar photovoltaic converter and solar panel according to an embodiment of the present invention.

[0026] Figure 2 yes Figure 1 The flowchart shows the microcontroller unit controlling the power conversion system. Implementation

[0027] To provide a further understanding of the purpose, structure, features, and functions of the present invention, detailed descriptions are provided below with reference to specific embodiments.

[0028] Figure 1 This is a functional block diagram of a power conversion system (PCS) 100 and its coupled mains power 10, load 60, rechargeable battery 70, photovoltaic inverter (PVinverter) 50, and solar panel 80 according to an embodiment of the present invention. The photovoltaic inverter 50 is used to convert the direct current generated by the solar panel 80 into alternating current, and feed the converted alternating current into the load 60 and / or the power conversion system 100.

[0029] The power conversion system 100 includes an AC power connection port 12, an AC power supply port 14, a DC power supply port 16, a voltmeter and ammeter 30, and a microcontroller unit (MCU) 40. The power conversion system 100 can be connected to AC power 10 via the AC power connection port 12 and receive power from AC power 10. The DC power supply port 16 is coupled to a rechargeable battery 70, and the power conversion system 100 can charge the rechargeable battery 70 or receive power from the rechargeable battery 70 via the DC power supply port 16. The voltmeter and ammeter 30 is coupled to the AC power supply port 14 to detect the voltage Va and current Ia output by the power conversion system 100 from the AC power supply port 14. The voltage Va and current Ia are the AC voltage and AC current, respectively. The microcontroller unit 40 is used to control the operation of the power conversion system and receives the state of charge (SOC) signal from the rechargeable battery 70. The microcontroller unit 40 can obtain the current charge percentage of the rechargeable battery 70 based on the state of charge (SOC) signal, and obtain the external output power P_Inv of the power conversion system 100 based on the voltage Va and current Ia detected by the voltmeter and ammeter 30. When the external output power P_Inv is positive, it indicates that the power conversion system 100 outputs electrical energy through the AC power port 14; when the external output power P_Inv is negative, it indicates that the power conversion system 100 receives electrical energy from the outside through the AC power port 14.

[0030] The power conversion system 100 may also include a DC-DC converter 20 and a power inverter 22. The DC-DC converter 20 is used to convert the DC voltage Vb output by the rechargeable battery 70 into a DC voltage Vd of different values, while the power inverter 22 is used to convert the DC voltage Vd into an AC voltage Va.

[0031] Figure 2 yes Figure 1 The flowchart illustrates the control of the power conversion system 100 by the microcontroller unit 40. When the microcontroller unit 40 detects an off-grid event (e.g., when the connection between port 12 and the mains power 10 is disconnected or the mains power 10 experiences a power outage), the microcontroller unit 40 executes... Figure 2 The process includes the following steps:

[0032] Step S100: The microcontroller unit 40 determines whether the power conversion system 100 has reconnected to the grid. Specifically, when the conversion system 100 reconnects to the mains power 10 or the solar photovoltaic converter 50 starts supplying power, it indicates that the power conversion system 100 has reconnected to the grid. If the microcontroller unit 40 determines that the power conversion system 100 has not reconnected to the grid, it executes step S102; otherwise, it executes step S113.

[0033] Step S102: The microcontroller unit 40 determines whether the current charge percentage of the rechargeable battery 70 is greater than the first preset percentage s1 based on the state of charge (SOC) signal. The first preset percentage s1 can be adjusted according to different control requirements (e.g., between 20% and 90%). When the microcontroller unit 40 determines that the charge percentage of the rechargeable battery 70 is greater than the first preset percentage s1, it executes step S104; otherwise, it returns to step S100.

[0034] Step S104: The microcontroller unit 40 determines whether the external output power P_Inv is less than the first preset power P1. The first preset power P1 can be adjusted according to different control requirements (e.g., 500 watts). When the microcontroller unit 40 determines that the external output power P_Inv is less than the first preset power P1, it executes step S106; otherwise, it returns to step S100.

[0035] Step S106: The microcontroller unit 40 increases the frequency F of the AC power output from the AC power port 14 of the power conversion system 100, causing the solar photovoltaic converter 50 coupled to the AC power port 14 to stop outputting power and enter overfrequency protection. For example, the microcontroller unit 40 increases the frequency F of the AC power to (F_Trip + Max_step). Here, F_Trip is, for example, 60.6 Hz, and Max_step is, for example, 0.3 Hz. Furthermore, once the frequency F of the AC power reaches above F_Trip, the solar photovoltaic converter 50 will stop outputting power. The frequency F_Trip can be called the cutoff frequency. Max_step can be considered as a frequency added to the cutoff frequency to avoid false alarms. In practical applications, the solar photovoltaic converter 50 may be selected from products of different brands available on the market. This results in differences in the specific product parameters of solar photovoltaic converters from different brands in the power conversion system. To avoid misjudgment caused by minor frequency errors due to different brands of solar photovoltaic converters, Max_step is added to avoid misjudgment and accurately control the solar photovoltaic converter, enabling it to accurately stop output. Therefore, when the frequency F of the AC power is equal to (F_Trip + Max_step), it can be further ensured that the solar photovoltaic converter 50 will stop outputting power. After the microcontroller unit 40 completes step S106, it returns to step S100.

[0036] Step S113: The microcontroller unit 40 determines whether the current charge percentage of the rechargeable battery 70 is less than the second preset percentage s2 based on the state of charge (SOC) signal. The second preset percentage s2 can be 10% less than the first preset percentage s1. Therefore, when the first preset percentage s1 is between 20% and 90%, the second preset percentage s2 can be between 10% and 80%. If the microcontroller unit 40 determines that the current charge percentage of the rechargeable battery 70 is not less than the second preset percentage s2, then step S115 is executed; otherwise, step S117 is executed.

[0037] Step S115: The microcontroller unit 40 sets the frequency F of the AC power output from the AC power port 14 of the power conversion system 100 to the cutoff frequency F_trip, so that the solar photovoltaic converter 50 stops outputting power and enters overfrequency protection; and

[0038] Step S117: The microcontroller 40 sets the frequency F of the AC power output from the AC power port 14 of the power conversion system 100 to the normal frequency F_normal, so that the solar photovoltaic converter 50 can resume output power; wherein, the normal frequency F_normal is, for example, 60 Hz; after the microcontroller 40 completes step S117, it returns to step S100.

[0039] When the solar photovoltaic converter 50 detects that the voltage or frequency exceeds the normal operating range, it will activate protection (e.g., overvoltage, undervoltage, overfrequency, underfrequency, islanding, etc.) and stop outputting power to the grid. At this time, the microcontroller unit 40 will determine whether the solar photovoltaic converter 50 has tripped and adjust the AC output frequency of the power conversion system 100 according to the status to determine whether the solar photovoltaic converter 50 can be reconnected to the grid for power supply. If the solar photovoltaic converter 50 detects that the voltage and frequency of the mains terminal are within the normal operating range, it will determine that the conditions for reconnecting to the grid for power supply are met. After counting a certain number of seconds (e.g., 300 seconds as required by grid connection regulations), the solar photovoltaic converter 50 will output power to the grid.

[0040] In this invention, the solar photovoltaic converter 50 responds to the frequency F of the AC power output from the AC power port 14 in a two-stage manner: full output (100%) or no output (0%). When the frequency F of the AC power output from the AC power port 14 is within a first range, the solar photovoltaic converter 50 converts the electrical energy received from the solar panel 80 and then outputs 100% of the converted power; conversely, when the frequency of the AC power output from the AC power port 14 is not within the first range, the solar photovoltaic converter 50 stops outputting power. For example, the first range is 59.3 Hz to 60.5 Hz. In practical applications, the first range is set according to the specific parameters of the components within the power conversion system and is not limited to this. For example, when the frequency F of the AC power output from AC power port 14 is between 59.3 Hz and 60.5 Hz, the solar photovoltaic converter 50 will convert the electrical energy received from the solar panel 80 and then output the converted power at 100% efficiency; while when the frequency of the AC power output from AC power port 14 is less than 59.3 Hz or greater than 60.5 Hz, the solar photovoltaic converter 50 will stop outputting power.

[0041] According to the above Figure 2 As can be seen from the process, when the microcontroller unit 40 detects an off-grid power outage and determines that the current charge percentage of the rechargeable battery 70 is greater than a first preset percentage s1 and the external output power P_Inv is less than a first preset power P1, the microcontroller unit 40 will increase the frequency F of the AC power output from the AC power port 14 of the power conversion system 100. This causes the solar photovoltaic converter 50 to stop outputting power and enter over-frequency protection. The power conversion system 100 will then supply the power from the rechargeable battery 70 to the load 60, ensuring uninterrupted power supply to the load 60. At this time, the external output power P_Inv of the power conversion system 100 is a positive number.

[0042] Furthermore, when the microcontroller unit 40 detects an off-grid and determines that the current charge percentage of the rechargeable battery 70 is equal to or less than a first preset percentage s1, the microcontroller unit 40 maintains the frequency F of the AC power output from the AC power port 14 to ensure that the solar photovoltaic converter 50 continues to output power. Similarly, when the microcontroller unit 40 detects an off-grid and determines that the current charge percentage of the rechargeable battery 70 is greater than the first preset percentage s1 and the external output power P_Inv is greater than or equal to the first preset power P1, the microcontroller unit 40 maintains the frequency of the AC power output from the AC power port 14 to ensure that the solar photovoltaic converter 50 continues to output power.

[0043] Furthermore, when the microcontroller unit 40 determines that the current charge percentage of the rechargeable battery 70 is less than the second preset percentage s2, the microcontroller unit 40 reduces the frequency F of the AC power output from the AC power port 14 to allow the solar photovoltaic converter 50 to resume output power. At this time, if the power consumption of the load 60 is greater than the power output of the solar photovoltaic converter 50, the power conversion system 100 will convert the power received from the rechargeable battery 70 and output it to the load 60. However, if the power output of the solar photovoltaic converter 50 is greater than the power consumption of the load 60, the solar photovoltaic converter 50 will also output additional power to the power conversion system 100 to charge the rechargeable battery 70.

[0044] In addition, when the microcontroller 40 determines that the current charging ratio of the rechargeable battery 70 is between the first preset ratio s1 and the second preset ratio s2, the microcontroller 40 will set the frequency F of the AC power output from the AC power port 14 to the cutoff frequency F_trip, so that the solar photovoltaic converter 50 stops outputting power and enters overfrequency protection.

[0045] In summary, when the microcontroller of this invention detects an off-grid situation, it causes the power conversion system to output AC frequency F, thereby inducing the solar photovoltaic converter to generate electricity and feed it back to the grid without entering islanding protection. The energy can be supplied to the load and the power conversion system. The microcontroller dynamically adjusts the frequency of the AC output by the power conversion system according to the current charge ratio of the rechargeable battery and the positive or negative value of the output power P_Inv. Therefore, the overall power flow can be efficiently regulated.

[0046] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A power conversion system, characterized in that, It includes: AC power port; DC power port, coupled to a rechargeable battery; A voltmeter and current meter are coupled to the AC power supply port. The voltmeter and current meter are used to detect the voltage and current output by the power conversion system from the AC power supply port. as well as The microcontroller unit is used to control the operation of the power conversion system and receive state of charge signals from the rechargeable battery. The microcontroller unit obtains the current charge percentage of the rechargeable battery based on the state-of-charge signal, and calculates the output power of the power conversion system based on the voltage and current detected by the voltmeter and ammeter. When the microcontroller detects a power outage, it performs the following steps: Determine whether the current charged percentage of the rechargeable battery is greater than a first preset percentage; When it is determined that the current charge ratio of the rechargeable battery is greater than the first preset ratio, it is determined whether the external output power is less than the first preset power. as well as When it is determined that the external output power is less than the first preset power, the frequency of the AC power output from the AC power source of the power conversion system is increased so that the solar photovoltaic converter coupled to the AC power source stops outputting power.

2. The power conversion system as described in claim 1, characterized in that, When the microcontroller detects a power grid disconnection and determines that the current charge percentage of the rechargeable battery is greater than the first preset percentage and the external output power is less than the first preset power, the power conversion system supplies the power from the rechargeable battery to the load.

3. The power conversion system as described in claim 1, characterized in that, When the microcontroller detects a grid disconnection and determines that the current charge percentage of the rechargeable battery is equal to or less than the first preset percentage, the microcontroller maintains the frequency of the AC power output from the AC power port so that the solar photovoltaic converter continues to output power.

4. The power conversion system as described in claim 1, characterized in that, When the microcontroller detects a grid disconnection and determines that the current charge percentage of the rechargeable battery is greater than the first preset percentage and the external output power is greater than or equal to the first preset power, the microcontroller maintains the frequency of the AC power output from the AC power port so that the solar photovoltaic converter continues to output power.

5. The power conversion system as described in claim 1, characterized in that, When the microcontroller determines that the current charge ratio of the rechargeable battery is less than the second preset ratio, the microcontroller reduces the frequency of the AC power output from the AC power port so that the solar photovoltaic converter can resume output power, and the second preset ratio is less than the first preset ratio.

6. The power conversion system as described in claim 5, characterized in that, When the microcontroller determines that the current charge ratio of the rechargeable battery is less than the second preset ratio, the solar photovoltaic converter resumes outputting power to the load. When the power consumed by the load is greater than the power output by the solar photovoltaic converter, the power conversion system outputs power to the load.

7. The power conversion system as described in claim 5, characterized in that, When the microcontroller determines that the current charge ratio of the rechargeable battery is less than the second preset ratio, the solar photovoltaic converter resumes outputting power to the load. When the power output by the solar photovoltaic converter is greater than the power consumed by the load, the solar photovoltaic converter outputs additional power to the power conversion system to charge the rechargeable battery.

8. The power conversion system as described in claim 1, characterized in that, When the microcontroller determines that the current charge ratio of the rechargeable battery is between the first preset ratio and the second preset ratio, the microcontroller sets the frequency of the AC power output from the AC power port to the cutoff frequency so that the solar photovoltaic converter stops outputting power, and the second preset ratio is less than the first preset ratio.

9. The power conversion system as described in claim 1, characterized in that, The solar photovoltaic converter responds to the frequency of the AC power output from the AC power port in a two-stage manner: full output or no output.

10. The power conversion system as described in claim 1 or 9, characterized in that, When the frequency of the AC power output from the AC power port is within the first range, the solar photovoltaic converter converts the electrical energy and then outputs the converted power at 100% efficiency; when the frequency of the AC power output from the AC power port is not within the first range, the solar photovoltaic converter stops outputting power.

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