A UPS and UPS power system suitable for implementing online battery testing

Abstract

The application discloses a UPS and a UPS power supply system suitable for realizing online battery testing, and relates to the technical field of UPSs. The UPS comprises a DC bus, a bidirectional AC / DC converter, a bidirectional DC / DC converter, a DC / AC converter and a control unit; the control unit controls the bidirectional AC / DC converter and the bidirectional DC / DC converter to work in a normal working mode and a battery testing mode; and in the battery testing mode: the working direction and the output power of the bidirectional AC / DC converter are configured so that the algebraic sum of the discharge power of the battery and the output power of the bidirectional AC / DC converter is balanced with the load power, and the battery is discharged with constant current, thereby realizing accurate online battery testing on the battery contained in the UPS power supply system based on the UPS.

Description

[0001] This invention is a divisional application of the patent application filed on June 25, 2021, with application number 202110711787.2 and patent title "A constant current discharge device and related methods and systems". Technical Field

[0002] This invention relates to the field of battery-powered UPS power supply system technology, and more particularly to a UPS and UPS power supply system suitable for realizing online battery testing. Background Technology

[0003] In the transportation and industrial sectors, UPS power supply systems are commonly used to ensure the power supply to loads. After the UPS power supply system is put into use, in order to ensure the energy storage reliability of the backup battery, it is necessary to conduct periodic discharge tests on the battery to evaluate its performance.

[0004] Traditionally, offline testing was used, which involved disconnecting the host from the battery and applying a heating discharge test to the battery alone with a resistance wire. This method not only carries the risk of power failure but also causes the ambient temperature to rise, requiring forced cooling. Therefore, the demand for online battery testing is increasing.

[0005] However, during online testing, the load at the customer's site is usually small and fluctuates greatly, which leads to problems such as slow discharge, limited testing conditions, and inability to accurately calculate the discharge capacity, making it difficult to obtain accurate and effective test evaluation results. Summary of the Invention

[0006] The purpose of this invention is to overcome at least one defect or problem existing in the prior art, and to provide a method for conducting online testing of batteries while ensuring stable power supply to the load and obtaining more accurate and effective test evaluation results.

[0007] To achieve the above objectives, a first aspect of the present invention provides a UPS suitable for implementing online battery testing, for connecting mains power, a battery, and a load; comprising: a DC bus; a bidirectional AC / DC converter connected to the mains power and the DC bus for bidirectional power conversion between the mains power and the DC bus; a bidirectional DC / DC converter connected to the battery and the DC bus for bidirectional power conversion between the battery and the DC bus; a DC / AC converter connected to the load and the DC bus for power conversion between the load and the DC bus; and a control unit for controlling the bidirectional AC / DC converter. The bidirectional DC / DC converter operates in a normal operating mode and a battery test mode. In the normal operating mode, when the mains power fails, the bidirectional DC / DC converter is turned on and the battery supplies power to the load. When the mains power is normal, the operating direction of the bidirectional AC / DC converter is controlled and the mains power supplies power to the load and the battery. In the battery test mode, the operating direction and output power of the bidirectional AC / DC converter are configured such that the discharge power of the battery and the algebraic sum of the output power of the bidirectional AC / DC converter are balanced with the load power, so that the battery discharges at a constant current.

[0008] Furthermore, the control unit is adapted to switch to the battery test mode when executing the second control strategy, and to start timing when the battery is discharging at the constant current, so as to evaluate the battery performance based on the constant current after the timing is completed.

[0009] Furthermore, when the load power is greater than the battery discharge power, the control unit controls the operating direction of the bidirectional AC / DC converter and enables both the mains power and the battery to supply power to the load simultaneously; when the load power matches the battery discharge power, the control unit controls the bidirectional AC / DC converter to turn off and enables the load to be powered only by the battery; when the load power is less than the battery discharge power, the control unit controls the operating direction of the bidirectional AC / DC converter and enables the battery to supply power to the load and feed power to the mains power; when the load is unloaded, the control unit controls the operating direction of the bidirectional AC / DC converter and enables the battery to supply power only to the mains power.

[0010] Furthermore, the control unit includes a first control loop and a second control loop, both configured as feedback control loops. The setpoint and feedback quantity of the second control loop are the value of the constant current and the actual discharge current value of the battery, respectively, and its output is a second current value. The setpoint and feedback quantity of the first control loop are the second current value and the current value of the bidirectional AC / DC converter near the mains power, respectively, and its output is a PWM drive signal suitable for adjusting the operating direction and output power of the bidirectional AC / DC converter. When the load power is greater than the battery discharge power, the second current value is positive and its absolute value is positively correlated with the difference between the load power and the battery discharge power, and the operating direction of the bidirectional AC / DC converter is that electrical energy flows from the mains current to the DC bus. When the load power is less than the battery discharge power, the second current value is negative and its absolute value is positively correlated with the difference between the load power and the battery discharge power, and the operating direction of the bidirectional AC / DC converter is that electrical energy flows from the DC bus to the mains power. When the load power matches the battery discharge power, the second current value is 0, and the bidirectional AC / DC converter is turned off.

[0011] To achieve the above objectives, a second aspect of the present invention provides a UPS power supply system suitable for realizing online battery testing, characterized in that it includes a UPS as described in any one of the technical solutions and a battery connected to a bidirectional DC / DC converter of the UPS.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] A UPS connects mains power, a battery, and a load. Mains power is suitable for outputting or receiving power. When the load power and battery discharge power are mismatched, the control unit adjusts the operating direction and output power of the bidirectional AC / DC converter. Therefore, in battery test mode, the UPS introduces mains power to bidirectionally compensate for the power imbalance between the battery and the load, enabling dynamic balance among the three. This avoids the inevitable fluctuations in battery discharge current caused by matching load power when only the battery supplies power. Consequently, the discharge current of the battery connected to the UPS is controllable during discharge testing, making it suitable for accurate and reliable online battery testing. Furthermore, because the battery voltage gradually decreases during discharge due to its inherent discharge characteristics, even with a relatively stable load, the UPS can reliably control the battery discharge current. In other words, using this UPS, the battery discharge current can be controlled and constant current discharge can be achieved while ensuring stable power supply to the load. This allows for constant current online discharge testing of batteries in battery-powered UPS systems, yielding accurate and effective test evaluation results.

[0014] Furthermore, the UPS power supply system using the above-mentioned UPS inherits the aforementioned advantages. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments are briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a topology diagram of a UPS power supply system according to an embodiment of the present invention.

[0017] Figures 2a-2d These are schematic diagrams illustrating four power flow directions of the UPS power system in battery test mode according to embodiments of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and accompanying drawings of this invention is for distinguishing different objects and not for describing a specific order.

[0020] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0021] In the claims, description and drawings of this invention, unless otherwise expressly defined, the term "connection" may include both direct and indirect connections; the term "coupling" refers to two electrical modules having specific circuit functions after being connected.

[0022] Reference Figure 1 This invention provides a power supply system that is connected to an external first power source and used to supply power to a load. The first power source is adapted to output electrical energy or receive power. In this embodiment, the first power source is AC mains power, which can supply AC power to the power supply system or receive power from the power supply system to achieve grid connection.

[0023] Specifically, the power system has a bus and includes a battery, a first converter, a second converter, a third converter, and a control unit.

[0024] The term "battery" should be interpreted broadly, meaning it can be a single cell, a battery pack, or a battery cabinet. In this embodiment, the bus is a DC bus, and the load is an AC load. Correspondingly, the first converter is an AC / DC converter, specifically configured as a bidirectional AC / DC converter with its two ends connected to the first power source and the bus, respectively, to achieve bidirectional power conversion (i.e., rectification and inversion). The second converter is a bidirectional DC / DC converter with its two ends connected to the battery and the bus, respectively, to achieve bidirectional power conversion (i.e., buck-boost conversion) from the battery to the bus. The third converter is a DC / AC converter with its two ends connected to the bus and the load, respectively, to achieve inversion power conversion between them.

[0025] It is easy to understand that, after the above configuration, the power system of this embodiment is exemplary shown as a UPS power system, and the first converter, second converter, third converter, and control unit (excluding the battery) constitute the UPS. However, it goes without saying that by configuring the converters in other ways, the power system can be modified to have different buses and be suitable for connecting different first power sources and loads.

[0026] Furthermore, the control unit can execute different control strategies to control the first and second converters, so that the power system is in normal operating mode and battery test mode, respectively. It is understood that the control unit can refer to a single controller capable of performing the corresponding function, or it can refer to a collection of multiple controllers capable of performing the corresponding function.

[0027] It is worth noting that in normal operating mode, the power system mainly focuses on ensuring normal power supply to the load under any circumstances; while in battery testing mode, the power system needs to further achieve constant current discharge of the battery while still ensuring normal power supply to the load, in order to obtain accurate and effective test evaluation results.

[0028] On one hand, when the control unit executes the first control strategy, the power system is in normal operating mode. Specifically, in the normal operating mode, the control unit executes the first control strategy, which, when the first power supply fails, activates the second inverter and allows the battery to supply power to the load; when the first power supply is normal, it controls the operating direction of the first inverter and allows the first power supply to supply power to the load; when the battery is not fully charged, it controls the operating direction of the second inverter and allows the battery to be charged by the first power supply; and when the battery is fully charged, it shuts down the second inverter. It can be understood that the first control strategy is the conventional control strategy of the UPS power system during normal operation.

[0029] On the other hand, when the control unit executes the second control strategy, the UPS power system is in battery test mode. In battery test mode, the UPS acts as a constant current discharge device. Therefore, the following description focuses on the constant current discharge device as the primary perspective of the UPS control process in battery test mode, which is the second control strategy executed by the power system's control unit. However, it is understood that a constant current discharge device with the corresponding structure and control process can also be applied to other battery discharge scenarios and should not be limited to the online battery testing scenario of the power system.

[0030] Specifically, when the constant current discharge device is operating, the control unit activates the second converter and adjusts its operating direction so that electrical energy flows from the battery to the bus, thereby causing the battery to discharge to the bus. During the battery discharge process, the control unit also adjusts the operating direction and output power of the first converter when the load power and battery discharge power are mismatched, so that the sum of the battery discharge power and the output power of the first converter is balanced with the load power, and the battery maintains a constant current discharge to the bus at a set first current value. Preferably, during this process, the control unit also controls the output voltage of the second converter to maintain a constant voltage on the bus.

[0031] It is worth noting that since the power direction of battery discharge and the power direction of load are both constant, only the power direction of the first converter can change. Therefore, the output power of the first converter can be positive or negative. The sum of the battery discharge power and the output power of the first converter being balanced with the load power refers to the algebraic sum of the battery discharge power and the output power of the first converter being balanced with the load power, rather than the sum of their absolute values.

[0032] Combination Figures 2a-2d Specifically, when the load power is greater than the battery discharge power, the control unit controls the operating direction of the first inverter and causes the first power source and the battery to simultaneously supply power to the load, such as... Figure 2a As shown. When the load power matches the battery discharge power, the control unit controls the first inverter to shut down and ensures that the load is powered solely by the battery, such as... Figure 2b As shown. When the load power is less than the battery discharge power, the control unit controls the operating direction of the first inverter and causes the battery to supply power to the load and feed power to the first power source, as shown. Figure 2c As shown. When the load is unloaded, the control unit controls the operating direction of the first inverter and causes the battery to supply power only to the first power source, such as... Figure 2d As shown.

[0033] Therefore, when the load power and battery discharge power are matched and balanced or mismatched, by controlling the working direction of the first converter, the first power source can be introduced during battery discharge and the first power source can be put into the corresponding state of outputting electrical energy or receiving power. This ensures that the battery has a stable power output while ensuring the power supply to the load, thereby making the battery discharge current continuously controllable and achieving constant current discharge.

[0034] In this embodiment, the power system control unit includes a first control loop and a second control loop, both configured as feedback control loops, to better execute the second control strategy and improve the operation of the constant current discharge device. The setpoint and feedback of the second control loop are the first current value and the actual battery discharge current value, respectively, and its output is a second current value. The setpoint and feedback of the first control loop are the second current value and the current value of the first converter on the side closest to the first power source, respectively, and its output is a PWM drive signal suitable for adjusting the operating direction and output power of the first converter. Specifically, when the load power is greater than the battery discharge power, the second current value is positive and its absolute value is positively correlated with the difference between the load power and the battery discharge power, and the operating direction of the first converter is that electrical energy flows from the first power source to the bus. When the load power is less than the battery discharge power, the second current value is negative and its absolute value is positively correlated with the difference between the load power and the battery discharge power, and the operating direction of the first converter is that electrical energy flows from the bus to the first power source. When the load power matches the battery discharge power, the second current value is 0, and the first converter is turned off.

[0035] Therefore, by constructing a dual closed-loop feedback control loop within the control unit, the operating direction and output power of the first converter can be automatically adjusted by detecting the battery discharge current and based on the deviation between the actual discharge current and the set first current value. This can effectively stabilize the battery discharge current, resulting in higher stability compared to the scheme of directly sampling and comparing the load power and battery discharge power for control.

[0036] As described above, the UPS connects to mains power, a battery, and a load. Mains power is suitable for outputting or receiving power. When the load power and battery discharge power are mismatched, the control unit adjusts the operating direction and output power of the bidirectional AC / DC converter. Therefore, in battery test mode, the UPS introduces mains power to bidirectionally compensate for the power imbalance between the battery and the load, enabling dynamic power balance among the three components. This avoids the inevitable fluctuations in battery discharge current caused by matching the load power when only the battery supplies power. Consequently, the discharge current of the battery connected to the UPS is controllable during discharge testing, making it suitable for accurate and reliable online battery testing. Furthermore, because the battery's discharge voltage gradually decreases during discharge due to its inherent discharge characteristics, the UPS can reliably control the battery discharge current even when the load is relatively stable.

[0037] In other words, by using the above-mentioned UPS, the battery discharge current can be controlled and constant current discharge of the battery can be achieved while ensuring stable power supply to the load. The battery can be tested online with constant current and the test evaluation results can be obtained in the UPS power system that uses battery power.

[0038] Furthermore, with the second converter in the UPS, not only can the opening and closing control of the battery discharge circuit to the bus be performed, but the bus voltage can also be kept constant by controlling the output voltage of the second converter. This allows the mismatch between load power and battery discharge power to be quickly mapped to changes in battery discharge current, thereby effectively improving the response sensitivity of the control unit in a scheme that directly controls based on changes in battery discharge current.

[0039] Furthermore, the power supply system, based on a corresponding constant current discharge device, inherits all its advantages. When executing the second control strategy, the control unit can switch the system from normal operating mode to battery testing mode, and can perform constant current online discharge testing on the battery while ensuring stable power supply to the load, obtaining accurate and effective test evaluation results. In this embodiment, the power supply system is constructed as a UPS power supply system, thus solving the problem that UPS power supply systems struggle to perform online discharge testing on batteries while maintaining stable power supply to the load, and obtain accurate and effective test evaluation results.

[0040] The following section introduces a constant current discharge method based on the aforementioned constant current discharge device, and an online battery testing method based on the aforementioned power system and employing the constant current discharge method. It can be understood that the aforementioned related methods are actually internalized within the control unit of the corresponding device and system.

[0041] First, we introduce the constant current discharge method, which is used to achieve constant current discharge of the battery, including:

[0042] Set the first current value.

[0043] The second converter is turned on to discharge the battery to the bus, and the output voltage of the second converter is controlled to maintain a constant voltage on the bus.

[0044] When the load power and battery discharge power are mismatched, the operating direction and output power of the first converter are adjusted so that the sum of the battery discharge power and the output power of the first converter is balanced with the load power, and the battery is maintained to discharge to the bus at a constant current value of the first current.

[0045] Specifically, when the load power is greater than the battery discharge power, the operating direction of the first converter is controlled so that the first power source and the battery simultaneously supply power to the load; when the load power matches the battery discharge power, the first converter is controlled to shut down so that the load is powered only by the battery; when the load power is less than the battery discharge power, the operating direction of the first converter is controlled so that the battery supplies power to the load and feeds power to the first power source; when the load is unloaded, the operating direction of the first converter is controlled so that the battery supplies power only to the first power source.

[0046] Specifically, the method for adjusting the operating direction and output power of the first converter is as follows:

[0047] A first control loop and a second control loop, both of which are feedback control loops, are constructed, and control parameters for the first control loop and the second control loop are configured. The setpoint and feedback quantity of the second control loop are the first current value and the actual battery discharge current value, respectively, and its output is a second current value. The setpoint and feedback quantity of the first control loop are the second current value and the current value of the side of the first converter closest to the first power source, respectively, and its output is a PWM drive signal suitable for adjusting the operating direction and output power of the first converter. When the load power is greater than the battery discharge power, the second current value is positive, and its absolute value is positively correlated with the difference between the load power and the battery discharge power; the operating direction of the first converter is that electrical energy flows from the first power source to the bus. When the load power is less than the battery discharge power, the second current value is negative, and its absolute value is positively correlated with the difference between the load power and the battery discharge power; the operating direction of the first converter is that electrical energy flows from the bus to the first power source. When the load power matches the battery discharge power, the second current value is 0, and the first converter is turned off. The actual discharge current value of the battery and the current value of the side of the first converter closest to the first power source are detected and input into the second control loop and the first control loop respectively to obtain the PWM drive signal. The first converter is driven using the PWM drive signal.

[0048] Understandably, the constant current discharge method is based on a corresponding constant current discharge device, inheriting all its advantages. It can control the battery discharge current and achieve constant current discharge of the battery while ensuring stable power supply to the load. This provides a good material basis for conducting constant current online discharge tests on batteries in battery-powered power systems and obtaining accurate and effective test evaluation results.

[0049] The following describes the online battery testing method, which includes:

[0050] Switch the power system to battery test mode.

[0051] The battery is discharged at a constant current using the aforementioned constant current discharge method, and a timer is started.

[0052] When the battery voltage reaches a low voltage threshold or when the timing reaches a preset duration, the power system is switched to normal operating mode and the timing ends.

[0053] Battery performance is evaluated based on the battery's total discharge time.

[0054] Therefore, the battery online testing method is based on the corresponding UPS power supply system. By applying the aforementioned constant current discharge method in the UPS power supply system, the battery is subjected to constant current online discharge test while ensuring stable power supply to the load. The battery discharge time is accumulated and timed to evaluate the battery performance based on the total discharge time and the corresponding evaluation criteria, and accurate and effective test evaluation results are obtained.

[0055] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A UPS suitable for realizing online battery testing, used to connect mains power, battery, and load; characterized in that, include: DC bus; A bidirectional AC / DC converter, which connects the mains power and the DC bus, is used to realize bidirectional power conversion between the mains power and the DC bus; A bidirectional DC / DC converter, which connects the battery and the DC bus, is used to realize bidirectional power conversion between the battery and the DC bus; A DC / AC converter is connected to the load and the DC bus to realize the conversion of electrical energy between the load and the DC bus. and control unit, which controls the bidirectional AC / DC converter and bidirectional DC / DC converter to operate in normal working mode and battery test mode; In the normal operating mode: when the mains power fails, the bidirectional DC / DC converter is turned on and the battery supplies power to the load; when the mains power is normal, the operating direction of the bidirectional AC / DC converter is controlled and the mains power supplies power to the load and the battery; in the battery test mode: the operating direction and output power of the bidirectional AC / DC converter are configured such that the discharge power of the battery and the algebraic sum of the output power of the bidirectional AC / DC converter are balanced with the load power, so that the battery discharges at a constant current; The control unit includes a first control loop and a second control loop, both configured as feedback control loops. The setpoint and feedback quantity of the second control loop are the value of the constant current and the actual discharge current value of the battery, respectively, and its output is a second current value. The setpoint and feedback quantity of the first control loop are the second current value and the current value of the bidirectional AC / DC converter near the mains power, respectively, and its output is a PWM drive signal suitable for adjusting the operating direction and output power of the bidirectional AC / DC converter. When the load power is greater than the battery discharge power, the second current value is positive and its absolute value is positively correlated with the difference between the load power and the battery discharge power, and the operating direction of the bidirectional AC / DC converter is that the electrical energy flows from the mains current to the DC bus. When the load power is less than the battery discharge power, the second current value is negative and its absolute value is positively correlated with the difference between the load power and the battery discharge power, and the operating direction of the bidirectional AC / DC converter is that the electrical energy flows from the DC bus to the mains power. When the load power matches the battery discharge power, the second current value is 0, and the bidirectional AC / DC converter is turned off.

2. A UPS suitable for online battery testing as described in claim 1, characterized in that: The control unit is adapted to switch to the battery test mode when executing the second control strategy, and to start timing when the battery is discharging at the constant current, so as to evaluate the battery performance based on the constant current after the timing is completed.

3. A UPS suitable for realizing online battery testing as described in claim 1 or 2, characterized in that: When the load power is greater than the battery discharge power, the control unit controls the working direction of the bidirectional AC / DC converter and enables the mains power and the battery to supply power to the load simultaneously. When the load power matches the battery discharge power, the control unit controls the bidirectional AC / DC converter to shut down and makes the load powered only by the battery. When the load power is less than the battery discharge power, the control unit controls the working direction of the bidirectional AC / DC converter and enables the battery to supply power to the load and feed power to the mains power. When the load is unloaded, the control unit controls the operating direction of the bidirectional AC / DC converter and makes the battery supply power only to the mains.

4. A UPS power supply system suitable for realizing online battery testing, characterized in that: Includes a UPS as described in any one of claims 1-3 and a battery connected to the bidirectional DC / DC converter of the UPS.

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