A single-phase uninterruptible power supply circuit and a charge-discharge control method thereof

Abstract

The embodiment of the application provides a single-phase uninterruptible power supply circuit and a charge-discharge control method thereof, and the uninterruptible power supply mainly comprises three parts of a controllable rectification module, a battery charge-discharge module and an inverter voltage stabilizing module. The battery charge-discharge module needs to timely switch the charge mode and the discharge mode, realizes uninterrupted power supply of the load, and puts forward higher control requirements for the charge-discharge control system inside the uninterruptible power supply. The battery usually stores electric energy in the form of direct current, and the load usually adopts an alternating current power supply mode. Therefore, in order to ensure reliable power supply in an emergency, the battery charge-discharge module and the inverter voltage stabilizing module need to be cooperatively controlled, and direct current stored inside the battery is timely converted into alternating current meeting the demand and output.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of uninterruptible power supply control, in particular to a single-phase uninterruptible power supply circuit and a charge-discharge control method thereof. BACKGROUND

[0002] For some important power loads, the power supply system needs to be configured with an uninterruptible power supply to ensure the reliability of load power supply. The uninterruptible power supply is internally configured with a corresponding number of battery packs, which can still provide sufficient power to provide emergency power supply for critical equipment when the power grid is powered off. Under normal power supply conditions, the battery charge-discharge system in the uninterruptible power supply can convert the AC power from the power grid into DC power and store it in the battery pack for future use. When a power grid outage occurs, the battery charge-discharge control system needs to timely deliver the stored power from the battery to the load to ensure uninterrupted power supply.

[0003] At present, the charging module and the discharging module in most uninterruptible power supplies are separate, and it is difficult to realize quick switching between the charging mode and the discharging mode. SUMMARY

[0004] The embodiment of the present application provides a single-phase uninterruptible power supply circuit and a charge-discharge control method thereof, which combines the charging module and the discharging module together, and can realize the charging function and the discharging function at the same time. By optimizing the control strategy of the charge-discharge module, the demand for the charging mode and the discharging mode can be identified in time, and the discharging mode can be switched to in time under the condition of power grid outage to supply power to the load.

[0005] In a first aspect, the embodiment of the present application provides a single-phase uninterruptible power supply circuit, which comprises a controllable rectifier module, a battery charge-discharge module and an inverter voltage stabilizing module.

[0006] The controllable rectifier module comprises a power input end, the power input end is connected to a rectifier circuit, the rectifier circuit comprises a first upper bridge arm switch tube and a first lower bridge arm switch tube, the emitter of the first upper bridge arm switch tube and the collector of the first lower bridge arm switch tube are connected after being connected to the power input end; the bases of the first upper bridge arm switch tube and the first lower bridge arm switch tube are not connected;

[0007] The battery charge-discharge module comprises a battery, a second upper bridge arm switch tube and a second lower bridge arm switch tube; the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube are connected after being connected to one pole of the battery; the bases of the second upper bridge arm switch tube and the second lower bridge arm switch tube are not connected;

[0008] The inverter voltage stabilizing module comprises a third upper bridge arm switch tube and a third lower bridge arm switch tube; the emitter of the third upper bridge arm switch tube and the collector of the third lower bridge arm switch tube are connected to the power output end; the bases of the third upper bridge arm switch tube and the third lower bridge arm switch tube are not connected;

[0009] The filter capacitor is further connected to one end of the filter capacitor, the collector of the first upper bridge arm switch tube, the collector of the second upper bridge arm switch tube and the collector of the third upper bridge arm switch tube; the emitter of the first lower bridge arm switch tube, the other end of the filter capacitor, the emitter of the second lower bridge arm switch tube, the other pole of the battery and the emitter of the third lower bridge arm switch tube are connected.

[0010] Preferably, the controllable rectifier module further comprises a first resistor and a first inductor connected in series, one end of the first resistor is connected to the power input end, the other end of the first resistor is connected to the first inductor, and the first inductor, the emitter of the first upper bridge arm switch tube and the collector of the first lower bridge arm switch tube are connected.

[0011] Preferably, the battery charging and discharging module further comprises a second inductor, one end of the second inductor is connected to one pole of the battery, and the other end of the second inductor is connected to the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube.

[0012] Preferably, the inverter voltage stabilizing module further comprises a third inductor and a grounding capacitor, one end of the third inductor is connected to the emitter of the third upper bridge arm switch tube and the collector of the third lower bridge arm switch tube, the other end of the third inductor is connected to the power output end, and the power output end is grounded through the grounding capacitor.

[0013] In a second aspect, the embodiment of the present application provides a charging and discharging control method based on the single-phase uninterruptible power supply circuit of the first aspect of the present application, comprising:

[0014] Step S1, collecting the DC bus voltage V dc (k) at time k b (k), the battery voltage V b (k) and the battery charging and discharging current I dc (k) at time k, wherein the DC bus voltage V dc (k) is the voltage across the filter capacitor;

[0015] Step S2, determining the voltage equation of the battery charging and discharging module based on the duty cycles of the second upper bridge arm switch tube and the second lower bridge arm switch tube, the DC bus voltage V b (k) at time k and the battery voltage V b (k) at time k;

[0016] Step S3, first-order Euler discrete processing is performed on the voltage equation of the battery charge-discharge module to predict the charge-discharge current I at time k+1 b (k+1);

[0017] Step S4, the charge-discharge current reference value is equal to the charge-discharge current I at time k+1 b (k+1), the closed-loop control based on the PID controller is performed on the DC bus voltage and the battery voltage to determine the optimal duty ratio based on the charge-discharge current I b (k+1) at time k dc (k), the battery voltage V b (k), the battery charge-discharge current I b (k), and the optimal duty ratio is determined, and the control pulse signal is output according to the optimal duty ratio value.

[0018] As preferred, in the step S2, the voltage equation of the battery charge-discharge module is:

[0019]

[0020]

[0021] In the above formula, D is the duty ratio of the second upper bridge arm switch tube and the second lower bridge arm switch tube, and the value is in the range of 0-1; T on is the duration of the second upper bridge arm switch tube being turned on and the second lower bridge arm switch tube being turned off, T off is the duration of the second upper bridge arm switch tube being turned off and the second lower bridge arm switch tube being turned on; V dc is the DC bus voltage, V b is the battery voltage, I b is the battery charge-discharge current; and L2 is the inductance value of the second inductor between the battery and the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube.

[0022] As preferred, in the step S3, the charge-discharge current I b (k+1) at time k+1 is:

[0023]

[0024] In the above formula, T s is the sampling period, T s =T on +T off .

[0025] As preferred, in the step S4, the optimal duty ratio is:

[0026]

[0027] In the above formula, I* b= I b (k+1).

[0028] The single-phase uninterruptible power supply circuit and the charge-discharge control method thereof provided by the embodiment of the present application mainly include a controllable rectifying module, a battery charge-discharge module, an inverter voltage stabilizing module and the like. The battery charge-discharge module needs to timely switch the charge mode and the discharge mode to realize uninterrupted power supply for the load, and thus a higher control requirement is proposed for the charge-discharge control system inside the uninterruptible power supply. The battery usually stores electric energy in the form of direct current, while the load usually adopts an alternating current power supply mode. Therefore, to ensure reliable power supply in an emergency, the battery charge-discharge module and the inverter voltage stabilizing module need to be controlled in cooperation to timely convert the direct current stored inside the battery into alternating current output meeting the requirement. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0030] Figure 1 The topological structure diagram of the uninterruptible power supply circuit according to the embodiment of the present application;

[0031] Figure 2 The flow chart of the discharge control method according to the embodiment of the present application;

[0032] Figure 3 The circuit topological structure of the battery charge-discharge module of the uninterruptible power supply according to the embodiment of the present application;

[0033] Figure 4 The control block diagram of the given value of the charge-discharge current according to the embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0035] The term "and / or" in the embodiments of the present application merely describes an association relationship of associated objects, and indicates that three relationships can exist, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone.

[0036] The terms "first", "second" in the embodiments of the present application are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a system, product or device including a series of components or units is not limited to the listed components or units, but can optionally include components or units not listed or can optionally include other components or units inherent to the products or devices. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0037] In this paper, the term "embodiment" means that the specific features, structures or properties described in conjunction with the embodiment can be included in at least one embodiment of the present application. The phrase appears at various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] At present, most of the charging modules and discharging modules inside the uninterruptible power supply are separated, and it is difficult to realize the quick switching of the charging mode and the discharging mode.

[0039] Therefore, the embodiment of the present application provides a single-phase uninterruptible power supply circuit and a charging and discharging control method thereof, which combines the charging module and the discharging module together, and can realize the charging function and the discharging function at the same time. By optimizing the control strategy of the charging and discharging module, the demand for the charging mode and the discharging mode can be identified in time, and in the case of power grid sudden power failure, the discharging mode can be switched in time to supply power to the load. The following will be described and introduced through multiple embodiments.

[0040] Figure 1 A single-phase uninterruptible power supply circuit provided by the embodiment of the present application comprises a controllable rectifier module, a battery charging and discharging module and an inverter voltage stabilizing module.

[0041] The controllable rectifier module comprises a power input end Vin connected to a rectifier circuit, the rectifier circuit comprising a first upper bridge arm switch tube Q1-1 and a first lower bridge arm switch tube Q1-2, the emitter of the first upper bridge arm switch tube Q1-1 and the collector of the first lower bridge arm switch tube Q1-2 being connected to the power input end Vin; the bases of the first upper bridge arm switch tube Q1-1 and the first lower bridge arm switch tube Q1-2 are not connected.

[0042] The battery charging and discharging module comprises a battery (i.e. a battery box in the figure), a second upper bridge arm switch tube Q2-1 and a second lower bridge arm switch tube Q2-2; the emitter of the second upper bridge arm switch tube Q2-1 and the collector of the second lower bridge arm switch tube Q2-2 are connected to one pole of the battery; the bases of the second upper bridge arm switch tube Q2-1 and the second lower bridge arm switch tube Q2-2 are not connected.

[0043] The inverter voltage stabilizing module comprises a third upper bridge arm switch tube Q3-1 and a third lower bridge arm switch tube Q3-2; the emitter of the third upper bridge arm switch tube Q3-1 and the collector of the third lower bridge arm switch tube Q3-2 are connected to a power output end Vo; the bases of the third upper bridge arm switch tube Q3-1 and the third lower bridge arm switch tube Q3-2 are not connected.

[0044] A filter capacitor is further included, the filter capacitor comprising a plurality of series-connected capacitors, one end of the filter capacitor, the collectors of the first upper bridge arm switch tube Q2-1, the second upper bridge arm switch tube Q2-1 and the third upper bridge arm switch tube Q3-1 being connected; the emitters of the first lower bridge arm switch tube Q1-2, the other end of the filter capacitor, the second lower bridge arm switch tube Q2-2, the other pole of the battery and the third lower bridge arm switch tube Q3-2 being connected.

[0045] The battery charging and discharging module needs to be able to timely switch between charging mode and discharging mode, so as to realize uninterrupted power supply for the load, which puts forward higher control requirements for the charging and discharging control system inside the uninterruptible power supply. The battery usually stores electric energy in the form of direct current, while the load usually adopts alternating current power supply mode. Therefore, in order to ensure reliable power supply in emergency situations, the battery charging and discharging module and the inverter voltage stabilizing module need to be controlled in cooperation with each other, so as to timely convert the direct current stored inside the battery into alternating current output meeting the requirements.

[0046] On the basis of the above embodiment, as a preferred implementation, the controllable rectifier module further includes a first resistor R1 and a first inductor L1 connected in series, one end of the first resistor R1 is connected to the power input terminal Vin, the other end of the first resistor R1 is connected to the first inductor L1, the first inductor L1, the emitter of the first upper bridge arm switch tube Q1-1, and the collector of the first lower bridge arm switch tube Q1-2 are connected.

[0047] On the basis of the above embodiment, as a preferred implementation, the battery charging and discharging module further includes a second inductor L2, one end of the second inductor L2 is connected to one pole of the battery, and the other end of the second inductor L2 is connected to the emitter of the second upper bridge arm switch tube Q2-1 and the collector of the second lower bridge arm switch tube Q2-2.

[0048] On the basis of the above embodiment, as a preferred implementation, the inverter voltage stabilizing module further includes a third inductor L3 and a grounding capacitor C1, one end of the third inductor L3 is connected to the emitter of the third upper bridge arm switch tube Q3-1 and the collector of the third lower bridge arm switch tube Q3-2, and the other end of the third inductor L3 is connected to the power output terminal Vo, and the power output terminal Vo is grounded through the grounding capacitor C1.

[0049] In a second aspect, the embodiments of the present application provide a charging and discharging control method, based on the single-phase uninterruptible power supply circuit in the above embodiment, as shown in the formula (1), the method comprises: Figure 2

[0050] Step S1, sampling the DC bus voltage V dc , the battery voltage V b , and the battery charging and discharging current I b ; collecting the DC bus voltage V dc (k), the battery voltage V b (k), and the battery charging and discharging current I b (k) at time k, wherein the DC bus voltage V dc (k) is the voltage across the filter capacitor.

[0051] Step S2, determining the voltage equation of the battery charging and discharging module based on the duty cycles of the second upper bridge arm switch tube and the second lower bridge arm switch tube, the DC bus voltage V dc (k), and the battery voltage V b (k).

[0052] Figure 3 The formula (1) is the circuit topology of the battery charging and discharging module, and according to the circuit topology, the voltage equation is written as:

[0053] (1)​

[0054] In the above formula, D is the duty ratio of the second upper bridge arm switch tube and the second lower bridge arm switch tube, and the value is in the range of 0~1; T on is the duration of the second upper bridge arm switch tube being turned on and the second lower bridge arm switch tube being turned off, T off is the duration of the second upper bridge arm switch tube being turned off and the second lower bridge arm switch tube being turned on; V dc is the DC bus voltage, V b is the battery voltage, I b is the battery charging and discharging current; L2 is the inductance value of the second inductor between the battery and the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube.

[0055] Step S3, first-order Euler discrete processing is performed on the voltage equation of the battery charging and discharging module to determine the charging and discharging current I b (k+1) at time k+1.

[0056] According to formula (1), the first-order Euler discrete method can be used to predict the charging and discharging current I b (k+1) at time k+1, and the formula is as follows:

[0057] (2)

[0058] In the above formula, T s is the sampling period, T s =T on +T off .

[0059] Step S4, the charging and discharging current reference value is equal to the charging and discharging current I b (k+1) at time k+1, and the DC bus voltage and the battery voltage are subjected to closed-loop control based on a PID controller, so as to determine the optimal duty ratio based on the charging and discharging current I b (k+1) at time k+1, the DC bus voltage V dc (k) at time k, the battery voltage V b (k), the battery charging and discharging current I b (k), and output a control pulse signal according to the optimal duty ratio value.

[0060] Suppose the charging and discharging current reference value is I* b, and the charging and discharging current at time k+1 is equal to the current reference value, that is:

[0061] (3)

[0062] Combined with formula (2) and formula (3), the optimal duty ratio expression can be derived as:

[0063] (4)

[0064] When the battery is charging, the charging current value is positive, and the DC bus voltage is controlled by the controllable rectifier module. When the battery is discharging, the discharging current value is negative, and the battery charging and discharging module needs to stabilize the DC bus voltage to provide the inverter module with a stable DC bus voltage, thereby generating alternating current to meet the load demand.

[0065] According to the above control requirements, the charging and discharging current reference value generation schematic diagram is as shown in Figure 4 When the battery is charging, the DC bus voltage is controlled by the controllable rectifier module, and is higher than the DC bus voltage given value V* dc set by the charging and discharging module. Therefore, the PI controller output is constantly greater than 0, and after the limiter, the PI regulator output is 0, at which time the DC bus voltage control of the charging and discharging module does not work. The charging and discharging current reference value is only generated by the battery voltage PI controller, and outputs a positive charging current given value, and the charging and discharging module mainly charges the battery to reach the specified charging voltage.

[0066] When the battery is discharging, the DC bus voltage PI controller starts to work due to the loss of the controllable rectifier control of the DC bus voltage, and outputs a negative discharging current given value, at which time the charging and discharging module stabilizes the DC bus voltage through the discharging current of the battery. Due to the action of the limiter, the positive current given value generated by the battery voltage PI controller is limited in a small range, which is much smaller than the negative given value generated by the bus voltage PI controller. Therefore, the charging and discharging current reference value is negative, and the battery starts to discharge to stabilize the DC bus voltage.

[0067] By adopting Figure 4 the charging and discharging current reference value control block diagram, the charging mode and the discharging mode can be automatically and quickly switched.

[0068] Step 3: Output control pulse signals according to the optimal duty cycle value.

[0069] The embodiments of the application can be combined arbitrarily to achieve different technical effects.

[0070] In the above embodiments, all or part of the methods can be implemented by software, hardware, firmware, or any combination thereof. When implemented by software, all or part of the methods can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transferred from one website, computer, server or data center to another website, computer, server or data center through wired (such as coaxial cable, optical fiber, digital subscriber line) or wireless (such as infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that includes one or more available media sets. The available media can be magnetic media (such as floppy disk, hard disk, magnetic tape), optical media (such as DVD), or semiconductor media (such as solid state disk), etc.

[0071] Those of ordinary skill in the art can understand that all or part of the processes in the above embodiments can be instructed by a computer program to complete the relevant hardware, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. The aforementioned storage medium includes ROM or random access memory (RAM), magnetic disk or optical disk, and various media that can store program codes.

[0072] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A charge-discharge control method of a single-phase uninterruptible power supply circuit, the single-phase uninterruptible power supply circuit comprising a controllable rectifier module, a battery charge-discharge module and an inverter voltage stabilization module; the controllable rectifier module comprising a power input end connected to a rectifier circuit comprising a first upper bridge arm switch tube and a first lower bridge arm switch tube, the emitter of the first upper bridge arm switch tube and the collector of the first lower bridge arm switch tube being connected to the power input end after being connected to each other, the bases of the first upper bridge arm switch tube and the first lower bridge arm switch tube not being connected to each other; the battery charge-discharge module comprising a battery, a second upper bridge arm switch tube and a second lower bridge arm switch tube, the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube being connected to one pole of the battery after being connected to each other, the bases of the second upper bridge arm switch tube and the second lower bridge arm switch tube not being connected to each other; the inverter voltage stabilization module comprising a third upper bridge arm switch tube and a third lower bridge arm switch tube, the emitter of the third upper bridge arm switch tube and the collector of the third lower bridge arm switch tube being connected to a power output end after being connected to each other, the bases of the third upper bridge arm switch tube and the third lower bridge arm switch tube not being connected to each other; further comprising a filter capacitor, one end of the filter capacitor, the collectors of the first upper bridge arm switch tube, the second upper bridge arm switch tube and the third upper bridge arm switch tube being connected, the emitter of the first lower bridge arm switch tube, the other end of the filter capacitor, the emitter of the second lower bridge arm switch tube, the other pole of the battery and the emitter of the third lower bridge arm switch tube being connected, the battery charge-discharge module further comprising a second inductor, one end of the second inductor being connected to one pole of the battery, the other end of the second inductor being connected to the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube; the charge-discharge control method comprising: a step S1 of determining a target voltage of the battery; a step S2 of determining an optimal duty ratio of the battery charge-discharge module according to the target voltage; a step S3 of determining a target current of the battery according to the optimal duty ratio; a step S4 of determining a target voltage of the battery according to the target current; and a step S5 of controlling the battery charge-discharge module according to the target voltage of the battery. In the step S2, the voltage equation of the battery charge-discharge module is: In the step S4, the optimal duty ratio is: ​ ​ characterized in that ​ Step S1, collect the direct current bus voltage V at time k dc (k), battery voltage V b (k), battery charge and discharge current I b (k), wherein the direct current bus voltage V dc (k) is the voltage across the filter capacitor; Step S2, based on the duty cycle of the second upper bridge arm switch tube and the second lower bridge arm switch tube, the DC bus voltage V dc (k) battery voltage V b (k) determining the voltage equation of the battery charge and discharge module; Step S3, first-order Euler discrete processing is performed on the voltage equation of the battery charge-discharge module to predict the charge-discharge current I at k+1 time b (k+1) Step S4, let the charge and discharge current reference value equal to the charge and discharge current I at time k+1 b (k+1), the DC bus voltage and battery voltage are closed-loop controlled based on the PID controller to control the charge and discharge current I at time k+1 b (k+1), the DC bus voltage V at time k is collected dc (k), the battery voltage V b (k), the battery charge and discharge current I b (k), determine the optimal duty ratio, and output the control pulse signal according to the optimal duty ratio value.

2. The charge-discharge control method of a single-phase uninterruptible power supply circuit according to claim 1, characterized by, ​ In the above formula, D is the duty ratio of the second upper bridge arm switch tube and the second lower bridge arm switch tube, and the value is in the range of 0~1; T on is the duration of the second upper bridge arm switch tube being turned on and the second lower bridge arm switch tube being turned off, T off is the duration of the second upper bridge arm switch tube being turned off and the second lower bridge arm switch tube being turned on; V dc is the direct current bus voltage, V b is the battery voltage, I b is the battery charging and discharging current; L2 is the inductance value of the second inductor between the battery and the emitter of the second upper bridge arm switch tube and the collector of the second lower bridge arm switch tube.

3. The charge-discharge control method of a single-phase uninterruptible power supply circuit according to claim 2, characterized by, In the step S3, the charge / discharge current I at the time k+1 b (k+1) is: In the above equation, T s is the sampling period, T s = T on + T off .

4. The charge-discharge control method of a single-phase uninterruptible power supply circuit according to claim 3, characterized by, ​ In the above equation, I* b= I b (k+1).

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