Single-phase transformer district electric energy management device and control method thereof

Abstract

The invention discloses a single-phase transformer district electric energy management device and a control method thereof. The single-phase transformer district electric energy management device comprises a transformer output voltage regulating unit, a transformer load reactive power and harmonic compensation unit and a direct current energy storage unit. The method comprises the following steps: the reactive power and harmonic compensation unit performs control according to a switching tube control pulse generation method, performs reactive power and harmonic compensation on a load side, and simultaneously performs coordinated control on an actual terminal voltage of a capacitor of the direct-current energy storage unit; when the actual terminal voltage is approximately equal to the rated terminal voltage, the voltage regulating unit performs control according to a switching tube control pulse generation method so as to ensure that the load terminal voltage meets the reference requirement; in the process, power supply side voltage detection and short circuit protection detection are carried out all the time according to a control method of a mechanical switch. All common electric energy quality problems are solved, and the cost performance of the electric energy management device is improved; and the mechanical switch is controlled to quit operation when the power supply side voltage quality is qualified, so that the loss of equipment is saved, and the short-circuit current is reduced when the reload side is short-circuited.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage power distribution, and in particular to a single-phase transformer substation power management device and a control method thereof. Background Art

[0002] The power supply side of the transformer substation circuit may have problems with high or low supply voltage or harmonics in the supply voltage, which will affect the load power consumption. At the same time, the substation load will also require reactive power to work normally while consuming active power. This part of reactive power will cause loss in the power grid when it is obtained from the upper power grid of the substation transformer, and will also reduce the efficiency of the power grid equipment. For users who pass the power adjustment electricity fee assessment, they may also be fined for this part of reactive power. Some users will generate large harmonics due to the characteristics of their loads, and the harmonic current will also pass through the substation to affect the normal operation of the equipment in the upper power grid. To solve these problems at the same time, a multifunctional power management device is needed.

[0003] The current unified power quality conditioner can solve this problem, but most of the unified power quality conditioners use full-bridge inverters for the series and parallel parts. For example, the single-phase unified power quality controller uses 4 anti-parallel diode switches in the series part and 4 anti-parallel diode switches in the parallel part, requiring a total of 8 pairs of anti-parallel diode switches, which will increase the equipment cost. The use of a half-bridge inverter can reduce costs. If the voltage of the upper and lower bridge arm energy storage capacitors in the DC energy storage part is unbalanced, it will cause inverter failure. If hardware control measures are used, the equipment cost will inevitably increase. Summary of the invention

[0004] In view of the above existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides a single-phase transformer substation power management device and a control method thereof to improve the cost-effectiveness of existing power management devices while meeting the power management needs of the transformer substation.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a single-phase transformer area power management device, including a transformer output voltage regulation unit, a transformer load reactive power and harmonic compensation unit, and a DC energy storage unit;

[0008] The transformer output voltage regulating unit is composed of a mechanical switch, an isolation transformer, a switch tube of an anti-parallel diode, an inductor and an LC filter composed of a capacitor, and their connections; the transformer load reactive power and harmonic compensation unit is composed of a switch tube and an inductor of an anti-parallel diode, and their connections; the DC energy storage unit is composed of a capacitor connected in series with the common part of the transformer output voltage regulating unit and the transformer load reactive power and harmonic compensation unit.

[0009] As a preferred solution of the single-phase transformer substation electric energy management device described in the present invention, the device also includes a single-phase transformer substation power supply side voltage transformer, a single-phase transformer substation load side voltage transformer, the DC energy storage unit capacitor end voltage transformer, the DC energy storage unit load side current transformer, the transformer load reactive and harmonic compensation unit output current transformer and a device controller.

[0010] As a preferred solution of the single-phase transformer area power management device described in the present invention, the connection method of the transformer output voltage regulating unit includes:

[0011] After the primary winding of the isolation transformer is connected in parallel with the mechanical switch, it is connected in series to the live wire of the low-voltage circuit output by the single-phase transformer station area. The primary winding connected to the circuit incoming line side is defined as the incoming line end, and the secondary winding of the isolation transformer and the incoming line end are the secondary outgoing line ends of the same name;

[0012] The secondary output line end is connected in series with the mechanical switch and then connected in series with the reactor in the LC filter and connected to one end of the capacitor in the LC filter at the series connection. The other end of the reactor is connected to the inverter AC output end composed of a switch tube of an anti-parallel diode. The other end of the capacitor in the LC filter and the other end of the secondary output line of the isolation transformer are both connected to the neutral line of the low-voltage circuit output by the single-phase transformer station area; the two DC ends of the inverter are connected to the two ends of the DC energy storage unit composed of capacitors in series, and the capacitor series connection point is also connected to the neutral line of the low-voltage circuit.

[0013] As a preferred solution of the single-phase transformer area power management device described in the present invention, the connection method of the transformer load reactive power and harmonic compensation unit includes:

[0014] The DC end of the inverter formed by the switch tube of the anti-parallel diode is connected to the two ends of the DC energy storage unit, and the AC end of the inverter is connected to the live wire of the low-voltage circuit output by the single-phase transformer station area through a current transformer after being connected in series with a reactor.

[0015] In a second aspect, the present invention provides a single-phase transformer area power management control method, comprising:

[0016] The transformer load reactive power and harmonic compensation unit is controlled according to the generation method of the switch tube control pulse to compensate for the reactive power and harmonics on the load side, and coordinates and controls the actual terminal voltage of the capacitor of the DC energy storage unit;

[0017] When the actual terminal voltage of the capacitor is approximately equal to the rated terminal voltage, the transformer output voltage regulating unit is controlled according to the generation method of the switch tube control pulse to ensure that the load terminal voltage meets the reference requirement;

[0018] In this process, power supply side voltage detection and short circuit protection detection are always performed according to the control method of the mechanical switch to control the mechanical switch.

[0019] As a preferred solution of the single-phase transformer area power management control method described in the present invention, the transformer output voltage regulating unit is controlled according to the generation method of the switch tube control pulse, including:

[0020] The voltage signal detected by the voltage transformer at the power supply side of the single-phase transformer station area is used as the electrical angle wt of the dq rotating coordinate system after the electrical angle is obtained through the phase-locked loop;

[0021] The voltage signal detected by the voltage transformer on the load side of the single-phase transformer station and the voltage signal delayed by 90 electrical degrees are used as the voltages Uα and Uβ in the αβ coordinate system and U0=0;

[0022] The electrical angle wt is transformed from the αβ coordinate system to the dq coordinate system to obtain the d-axis voltage and q-axis voltage of the load side voltage in the dq rotating coordinate system, and the difference between the d-axis voltage and the q-axis voltage minus the reference voltage of each axis is used as the d-axis voltage and the q-axis voltage of the output voltage of the isolation transformer after PID adjustment;

[0023] The electrical angle wt is transformed from the dq coordinate system to the abc coordinate system, and the transformed a-phase voltage is subtracted from the triangular carrier. If the subtraction result is greater than or equal to 0, the upper bridge arm of the inverter is controlled to be turned on and the lower bridge arm is turned off; if the subtraction result is less than 0, the upper bridge arm of the inverter is controlled to be turned off and the lower bridge arm is turned on.

[0024] As a preferred solution of the single-phase transformer area power management control method described in the present invention, the transformer load reactive power and harmonic compensation unit is controlled according to the generation method of the switch tube control pulse, including:

[0025] The current signal I detected by the load side current transformer L Calculate the active current part I p , get the load reactive power and harmonic current value I that needs to be compensated L -I p ;

[0026] The rated terminal voltage of the capacitor of the DC energy storage unit is subtracted from the actual terminal voltage detected by the capacitor terminal voltage transformer, and the difference is multiplied by the active current part I after PID adjustment. p The active current I required to maintain the capacitor terminal voltage is obtained p1 ;

[0027] The difference between the actual terminal voltage of the capacitor connected to the upper bridge arm and the actual terminal voltage of the capacitor connected to the lower bridge arm of the DC energy storage unit is obtained by PID regulation to obtain the regulating current I for regulating the unbalanced voltage at the capacitor terminal. bp ;

[0028] Will I L -I p -I p1 +I bp The actual current detected by the output current transformer of the transformer load reactive and harmonic compensation unit is subtracted from the actual current, and the subtraction result is subtracted from the triangular carrier after PID adjustment. If the result is greater than or equal to 0, the upper bridge arm of the inverter is controlled to be turned on and the lower bridge arm is turned off; if the result is less than 0, the upper bridge arm of the inverter is controlled to be turned off and the lower bridge arm is turned on.

[0029] As a preferred solution of the single-phase transformer substation power management control method of the present invention, wherein: the current signal IL detected by the load-side current transformer is used to calculate the active current part Ip, which includes:

[0030] The electrical angle wt obtained by the phase-locked loop through the actual load voltage detected by the load-side voltage transformer is used to calculate 2*I L *sin(wt) is filtered through a low-pass filter to obtain the DC part, which is the peak value of the active current I pm , and then calculate I pm *sin(wt) can get the instantaneous active current I p .

[0031] As a preferred solution of the single-phase transformer area power management control method described in the present invention, the control method according to the mechanical switch includes:

[0032] A mechanical switch connected in parallel with the isolation transformer of the transformer output voltage regulating unit is controlled to be disconnected when the transformer output voltage regulating unit is put into use, and when the voltage on the power supply side of the low-voltage circuit output by the single-phase transformer station is within a qualified range, the upper and lower bridge arms of the inverter of the transformer output voltage regulating unit are closed, and the mechanical switch is controlled to be closed at the same time.

[0033] As a preferred solution of the single-phase transformer area power management control method described in the present invention, the control method according to the mechanical switch also includes:

[0034] The mechanical switch connected in series with the secondary output terminal of the transformer is controlled to be closed when the transformer output voltage regulating unit is put into use. When the current signal detected by the load-side current transformer is short-circuited, the switch is disconnected, so that only the primary side of the isolation transformer is connected in series as the excitation winding in the low-voltage circuit output by the single-phase transformer station area, thereby limiting the short-circuit current.

[0035] Compared with the prior art, the invention has the following beneficial effects: the invention provides a single-phase transformer substation power management device and a control method thereof, which realizes a series half-bridge inverter and a parallel half-bridge inverter by using a switch tube of four anti-parallel diodes, and is used for voltage regulation on the power supply side and load reactive power and harmonic compensation functions, solves all common power quality problems in conventional single-phase transformer substations, and improves the cost performance of power management devices; adopts a control method to adjust the voltage of the upper and lower bridge arm capacitors of the inverter, without adding hardware to increase costs, and the load active current can be directly obtained by trigonometric function calculation and low-pass filtering, compared with the traditional dq conversion instantaneous power detection, fewer multipliers are used and the amount of calculation is smaller; in addition, the invention controls the mechanical switch of the device, and the transformer output voltage regulation unit can exit operation when the voltage quality on the power supply side is qualified, saving the loss of the equipment itself. In addition, the mechanical switch of the control device can be used to reduce the short-circuit current by transmitting the excitation winding of the isolation transformer when the load side is short-circuited. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0037] Figure 1 A topological diagram of a single-phase transformer area power management device according to an embodiment of the present invention;

[0038] Figure 2 A control block diagram of a transformer output voltage regulation unit of a single-phase transformer area power management control method according to an embodiment of the present invention;

[0039] Figure 3 A control block diagram of a transformer load reactive power and harmonic compensation unit of a single-phase transformer area power management control method according to an embodiment of the present invention;

[0040] Figure 4A block diagram of single-phase load active current calculation for a single-phase transformer substation electric energy management control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0042] Example 1

[0043] Reference Figure 1 As an embodiment of the present invention, a single-phase transformer area power management device is provided, including a transformer output voltage regulation unit, a transformer load reactive power and harmonic compensation unit and a DC energy storage unit, specifically:

[0044] The transformer output voltage regulating unit is composed of two mechanical switches SW1 and SW2, an isolation transformer T, two switch tubes BD1 and BD2 of reverse parallel diodes, an inductor L1 and an LC filter composed of a capacitor C, and their connections;

[0045] The transformer load reactive power and harmonic compensation unit is composed of two reverse parallel diode switch tubes BD3 and BD4 and one reactor L2, and their connection lines;

[0046] The DC energy storage unit is composed of two capacitors C1 and C2 connected in series with the transformer output voltage regulation unit and the transformer load reactive power and harmonic compensation unit;

[0047] The single-phase transformer substation power management device also includes: single-phase transformer substation power supply side voltage transformer VM1, single-phase transformer substation load side voltage transformer VM2, DC energy storage unit each capacitor end voltage transformer VM3 and VM4, DC energy storage unit load side current transformer CM1, transformer load reactive and harmonic compensation unit output current transformer CM2. In addition to the components shown in the topology diagram, the device also includes a device controller.

[0048] In a feasible implementation manner, the connection method of the transformer output voltage regulating unit includes:

[0049] Figure 1The medium voltage source AC is simulated as a single-phase transformer power supply, and its output lines are live line L and zero sequence N. The primary winding of the isolation transformer T, whose terminal numbers are 1+ and 1, is connected in parallel with the mechanical switch SW1 and then connected in series to the live line L of the low-voltage circuit output by the single-phase transformer station; the primary winding of T is defined as the incoming line terminal 1+ connected to the incoming line side of the circuit, and the secondary winding of the isolation transformer is defined as the secondary output line terminal 2+ which is the same as the incoming line terminal. The secondary output terminal 2+ is connected in series with the mechanical switch SW2 and then connected in series with the reactor L1 in the LC filter, and one end of the capacitor C in the LC filter is connected at the series connection. The other end of the reactor L1 is connected to the inverter AC output end composed of the switch tubes BD1 and BD2 of two reverse parallel diodes; the other end of the capacitor C and the other end 2 of the secondary output line of the isolation transformer T are both connected to the neutral line N of the low-voltage circuit; the two DC terminals of the inverter are connected to the two ends of the DC energy storage unit composed of two capacitors C1 and C2 connected in series, and the capacitor series connection point is also connected to the neutral line N of the low-voltage circuit.

[0050] In a feasible implementation manner, the connection method of the transformer load reactive power and harmonic compensation unit includes:

[0051] Figure 1 The DC end of the inverter, which is composed of the switch tubes BD3 and BD4 of the two reverse parallel diodes, is connected to the two ends of the DC energy storage unit composed of C1 and C2; the AC end of the inverter is connected in series with the inductor L2 and then connected to the live wire of the low-voltage circuit output by the single-phase transformer station area through the current transformer CM2.

[0052] It should be noted that the present embodiment provides a single-phase transformer substation power management device, which realizes a series half-bridge inverter and a parallel half-bridge inverter by adopting a switch tube of four anti-parallel diodes, and is used for power supply side voltage regulation and load reactive power and harmonic compensation functions, thereby solving all common power quality problems of conventional single-phase transformer substations and improving the cost performance of the power management device; in addition, the present invention controls the mechanical switch of the device, so that the transformer output voltage regulation unit can exit operation when the voltage quality on the power supply side is qualified, thereby saving the equipment's own loss.

[0053] Example 2

[0054] Reference Figure 2 to Figure 4 As another embodiment of the present invention, a single-phase transformer area power management control method is provided, which specifically includes:

[0055] The transformer load reactive power and harmonic compensation unit is controlled according to the generation method of the switch tube control pulse, compensates for the reactive power and harmonics on the load side, and coordinates and controls the actual terminal voltage of the capacitor of the DC energy storage unit;

[0056] When the actual terminal voltage of the capacitor is approximately equal to the rated terminal voltage, the transformer output voltage regulating unit is controlled according to the generation method of the switch tube control pulse to ensure that the load terminal voltage meets the reference requirement;

[0057] During this process, power supply side voltage detection and short-circuit protection detection are always performed according to the control method of the mechanical switch to control the mechanical switch.

[0058] In a feasible implementation, the switch tube includes IGBT, IGCT, MOSFET, SiC, GaN, etc., and the device controller controls the transformer output voltage regulation unit and the transformer load reactive power and harmonic compensation unit, that is, provides a method for generating control pulses for the switch tube.

[0059] In a feasible implementation manner, the method for generating the control pulse of the switch tubes of the transformer output voltage regulating units BD1 and BD2 is as follows: Figure 2 As shown: Figure 1 The voltage signal VS detected by the voltage transformer VM1 on the power supply side is calculated by the phase-locked loop PLL1 to obtain the electrical angle as the electrical angle wt of the dq rotating coordinate system. It can be known from electrical related knowledge that the voltage vectors Ua, Ub, and Uc of the three-phase balanced AC circuit can be transformed from the abc coordinate system through Clark to the voltage vectors Uα, Uβ, and U0 in the αβ0 coordinate system, where Uα and Ua are equal, and Uβ lags behind Uα by 90 degrees and has the same electrical angle as the amplitude of Uα, and U0=0. Ua, Ub, and Uc can be transformed from the abc coordinate system through Park to the DC voltage vectors Ud, Uq, and U0 in the dq0 rotating coordinate system. When the electrical angle of Ua is the rotation angle, Ud is always equal to the amplitude of the three-phase voltage, which is the DC quantity, Uq=0, and U0=0. Because Ud, Uq, and U0 are DC quantities, they are convenient for adjustment and control. The present invention is applied to the single-phase area. As mentioned above, let VL = Uα, and let the signal lagging 90 degrees be Uβ, let U0 = 0, then the single-phase voltage signal can be equivalent to the three-phase voltage signal, and the three-phase voltage signal can be transformed into Ud, Uq, and U0 through coordinate transformation to the dq0 coordinate system. The goal of voltage regulation is to have an effective value of 220V on the load side, and its amplitude is 311V. Figure 1It can be seen that the d-axis voltage Ud and q-axis voltage Uq of the load voltage VL minus the reference voltage 311 and 0 of each axis are the d-axis voltage and q-axis voltage that the isolation transformer should output. For fast control, both are PID-adjusted to obtain the d-axis voltage Ud and q-axis voltage Uq, and U0=0. Using wt as the rotation angle, the voltage that the isolation transformer should output in the abc coordinate system can be obtained by transforming the dq coordinate system to the abc coordinate system. Because it is single-phase, the transformed a-phase voltage is the output voltage that the isolation transformer T should output. This voltage is the waveform that the inverter needs to modulate. It is subtracted from the triangular carrier. If the result of the subtraction is greater than or equal to 0, the upper bridge arm BD1 of the inverter is controlled to be turned on through PWM1, and the lower bridge arm BD2 of the inverter is controlled to be turned off through PWM2; if the result of the subtraction is less than 0, the opposite is true.

[0060] It should be noted that, through the above control, the difference between the isolation transformer output power supply voltage and the load side reference voltage can be made, so that the load side voltage reaches the reference value.

[0061] In a feasible implementation manner, the method for generating the control pulse of the switch tubes of the transformer load reactive power and harmonic compensation units BD3 and BD4 is as follows: Figure 3 As shown: Figure 1 The current signal I detected by the current transformer CM1 on the middle load side L After calculation, the active current part Ip is obtained, and then the load reactive power and harmonic current value I that needs to be compensated is obtained. L -I p ;

[0062] For the inverter, it is extremely important to maintain the stability of the voltage of the energy storage capacitor on the DC side. In order to increase its terminal voltage, the inverter needs to absorb active current, and to reduce its terminal voltage, it needs to release active current. The DC energy storage unit consists of two capacitors C1 and C2 connected in series. The rated terminal voltage is set to 500V in this example. It is assumed that the terminal voltages of C1 and C2 are equal. Therefore, 500V is subtracted from the actual terminal voltage detected by the voltage transformer at the terminal of any capacitor. In this example, the actual terminal voltage CV1 detected by the voltage transformer VM3 at the C1 terminal is selected. The difference is related to the active current that the inverter needs to absorb or release. Because the transformer load reactive power and harmonic compensation unit are connected in parallel with the load, their terminal voltages are equal. This part of the active current should be the same as I p The above difference is adjusted by PID and multiplied by I p The active current I required to maintain the capacitor terminal voltage is obtained p1 .

[0063] The actual terminal voltages of C1 and C2 cannot be exactly the same. By increasing the reactive power of the transformer load and the instantaneous value of the output current of the harmonic compensation unit, the energy consumed by the upper bridge arm capacitor C1 of the output instantaneous value inverter will increase, causing its voltage CV1 to drop and the lower bridge arm voltage CV2 to rise. Reducing the output instantaneous value will have the opposite effect. Therefore, the actual terminal voltage CV1 of the capacitor C1 connected to the upper bridge arm of the DC energy storage unit minus the actual terminal voltage CV2 of the capacitor C2 connected to the lower bridge arm, the difference obtained can be adjusted by PID to obtain the adjustment current I for adjusting the capacitor terminal voltage imbalance. bp .

[0064] I L -I p -I p1 +I bp The reference current output by the inverter of the reactive power and harmonic compensation unit is I L -I p -I p1 +I bp It is subtracted from the actual current detected by the output current transformer CM2 of the transformer load reactive and harmonic compensation unit, and the subtraction result is subtracted from the triangular carrier after PID adjustment. If the result is greater than or equal to 0, the upper bridge arm BD3 of the inverter is turned on through PWM3, and the lower bridge arm BD4 of the inverter is turned off through PWM4; when it is less than 0, the opposite is true.

[0065] It should be noted that, through the above control, the reactive current and reverse harmonic current required by the load output of the transformer load reactive and harmonic compensation unit can be made, so that the power supply side only provides the load active current, and the harmonics will not enter the power supply side. At the same time, by adjusting the active current flowing into this part and adjusting the instantaneous value of the output current, the voltage of the DC energy storage unit is stabilized and the voltages of the upper and lower bridge arm capacitors are equal, providing energy guarantee for the output regulation voltage of the transformer load reactive and harmonic compensation unit and the transformer output voltage regulation unit.

[0066] In a feasible implementation, the terminal voltage of a single-phase load is assumed to be Um*sin(wt), and its load current I can be written as:

[0067]

[0068] Among them, I pm is the fundamental active current amplitude, I qm is the fundamental reactive current amplitude, I nm is the nth harmonic current amplitude, is the initial phase angle of the nth harmonic. The “±” in the above formula is “+” when the reactive power of the load is capacitive, and “-” when it is inductive.

[0069] Multiplying both sides of the above equation by sin(wt) yields the following equation:

[0070]

[0071]

[0072] Among them, only the first item is a DC signal, and the others are sine and cosine signals. A low-pass filter can be used to filter out Ip / 2 in the above formula.

[0073] Specifically, the method for calculating Ip in the inverter control method of the transformer load reactive power and harmonic compensation unit is as follows: Figure 4 Shown: Using Figure 1 The actual load voltage VL detected by the load-side voltage transformer VM2 is the electrical angle wt obtained by the phase-locked loop PLL. The current signal detected by the load-side current transformer CM1 is I L , calculate 2*I L *sin(wt) is filtered by a low-pass filter LPF to obtain the DC part, which is the peak value of the active current I pm , calculate I pm *sin(wt) to get the instantaneous active current I p .

[0074] In one possible implementation, Figure 1 The mechanical switch SW1 connected in parallel with the isolation transformer T of the transformer output voltage regulating unit is controlled to be disconnected when the transformer output voltage regulating unit is put into use without affecting the operation of the transformer output voltage regulating unit. For example, the qualified range of the low-voltage circuit power supply side voltage VS output by the single-phase transformer station area is set to 220V±10V. When VS is in this range, the upper and lower bridge arms BD1 and BD2 of the inverter of the transformer output voltage regulating unit are first closed, and then SW1 is closed, so that the voltage on the power supply side of the low-voltage circuit directly supplies power to the load. No current passes through the transformer output voltage regulating unit, which can save energy loss. When VS is not in this range, SW1 is first disconnected, and then the transformer output voltage regulating unit starts voltage regulation according to the above control method. In the above process, the mechanical switch SW2 connected in series with the transformer output voltage regulating unit is in a closed state. After the current signal IL detected by the load-side current transformer CM1 is short-circuited, when SW1 is in a closed state, SW1 and SW2 are disconnected, and when SW1 is in an open state, SW2 is disconnected. Usually, the transformer has short-circuit tolerance. At this time, the secondary side of the isolation transformer is open due to the disconnection of SW2, and only the primary side winding is put into the circuit due to the disconnection of SW1. The primary winding has a large impedance as an excitation winding, which is equivalent to a reactor. Therefore, the low-voltage circuit connected in series with the output of the single-phase transformer station area limits the amplitude of the short-circuit current, thereby better protecting the line.

[0075] In order for the equipment to work properly, the voltage at the capacitor end of the DC energy storage unit of the device must be approximately equal to the rated terminal voltage. Therefore, the transformer load reactive power and harmonic compensation unit is first controlled according to the above method to compensate for the reactive power and harmonic current on the load side, and the actual terminal voltages VC1 and VC2 of the DC energy storage unit capacitors C1 and C2 are coordinated and controlled. When both are approximately equal to the rated terminal voltage, the transformer output voltage regulation unit begins to control according to the above method to ensure that the load terminal voltage meets the reference voltage requirements. In this process, power supply side voltage detection and load current short-circuit protection detection are always performed to control the mechanical switches SW1 and SW2.

[0076] It should be noted that the present invention provides a single-phase transformer substation power management control method, which realizes a series half-bridge inverter and a parallel half-bridge inverter by using a switch tube of four anti-parallel diodes, which is used for power supply side voltage regulation and load reactive and harmonic compensation functions, solves all common power quality problems in conventional single-phase transformer substations, and improves the cost performance of power management devices; the control method is used to adjust the voltage of the upper and lower bridge arm capacitors of the inverter, without adding hardware to increase costs, and the load active current can be directly obtained by trigonometric function calculation and low-pass filtering, compared with the traditional dq conversion instantaneous power detection, fewer multipliers are used and the amount of calculation is smaller; in addition, the present invention controls the mechanical switch of the device, and the transformer output voltage regulation unit can exit operation when the voltage quality on the power supply side is qualified, saving the loss of the equipment itself. In addition, the mechanical switch of the control device can be used to reduce the short-circuit current by transmitting the excitation winding of the isolation transformer when the load side is short-circuited.

[0077] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0079] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0080] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0081] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0082] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1The steps for the functions specified in one or more boxes.

[0083] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0084] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A single-phase transformer area power management device, characterized in that: It includes a transformer output voltage regulating unit, a transformer load reactive power and harmonic compensation unit, and a DC energy storage unit; The transformer output voltage regulating unit is composed of a mechanical switch, an isolation transformer, a switch tube of an anti-parallel diode, an LC filter composed of a reactor and a capacitor, and their connections; The transformer load reactive power and harmonic compensation unit is composed of a switch tube and a reactor of an anti-parallel diode, and their connection lines; The DC energy storage unit is composed of a capacitor connected in series with a portion shared by the transformer output voltage regulation unit and the transformer load reactive power and harmonic compensation unit.

2. The single-phase transformer area power management device according to claim 1, characterized in that: The device also includes a single-phase transformer station power supply side voltage transformer, a single-phase transformer station load side voltage transformer, the DC energy storage unit capacitor end voltage transformer, the DC energy storage unit load side current transformer, the transformer load reactive and harmonic compensation unit output current transformer and a device controller.

3. The single-phase transformer area power management device as claimed in claim 2, characterized in that: The connection method of the transformer output voltage regulating unit includes: After the primary winding of the isolation transformer is connected in parallel with the mechanical switch, it is connected in series to the live wire of the low-voltage circuit output by the single-phase transformer station area. The primary winding connected to the circuit incoming line side is defined as the incoming line end, and the secondary winding of the isolation transformer and the incoming line end are the secondary outgoing line ends of the same name; The secondary output line end is connected in series with the mechanical switch and then connected in series with the reactor in the LC filter and connected to one end of the capacitor in the LC filter at the series connection. The other end of the reactor is connected to the inverter AC output end composed of a switch tube of an anti-parallel diode. The other end of the capacitor in the LC filter and the other end of the secondary output line of the isolation transformer are both connected to the neutral line of the low-voltage circuit output by the single-phase transformer station area; the two DC ends of the inverter are connected to the two ends of the DC energy storage unit composed of capacitors in series, and the capacitor series connection point is also connected to the neutral line of the low-voltage circuit.

4. The single-phase transformer area power management device as claimed in claim 3, characterized in that: The connection method of the transformer load reactive power and harmonic compensation unit includes: The DC end of the inverter formed by the switch tube of the anti-parallel diode is connected to the two ends of the DC energy storage unit, and the AC end of the inverter is connected to the live wire of the low-voltage circuit output by the single-phase transformer station area through a current transformer after being connected in series with a reactor.

5. A control method for a single-phase transformer area power management device according to any one of claims 1 to 4, characterized in that: include: The transformer load reactive power and harmonic compensation unit is controlled according to the generation method of the switch tube control pulse to compensate for the reactive power and harmonics on the load side, and coordinates and controls the actual terminal voltage of the capacitor of the DC energy storage unit; When the actual terminal voltage of the capacitor is approximately equal to the rated terminal voltage, the transformer output voltage regulating unit is controlled according to the generation method of the switch tube control pulse to ensure that the load terminal voltage meets the reference requirement; In this process, power supply side voltage detection and short circuit protection detection are always performed according to the control method of the mechanical switch to control the mechanical switch.

6. The single-phase transformer area power management control method as claimed in claim 5, characterized in that: The transformer output voltage regulating unit is controlled according to the generation method of the switch tube control pulse, including: The voltage signal detected by the voltage transformer at the power supply side of the single-phase transformer station area is used as the electrical angle wt of the dq rotating coordinate system after the electrical angle is obtained through the phase-locked loop; The voltage signal detected by the voltage transformer on the load side of the single-phase transformer station and the voltage signal delayed by 90 electrical degrees are used as the voltages Uα and Uβ in the αβ coordinate system and U0=0; The electrical angle wt is transformed from the αβ coordinate system to the dq coordinate system to obtain the d-axis voltage and q-axis voltage of the load side voltage in the dq rotating coordinate system, and the difference between the d-axis voltage and the q-axis voltage minus the reference voltage of each axis is used as the d-axis voltage and the q-axis voltage of the output voltage of the isolation transformer after PID adjustment; The electrical angle wt is transformed from the dq coordinate system to the abc coordinate system, and the transformed a-phase voltage is subtracted from the triangular carrier. If the subtraction result is greater than or equal to 0, the upper bridge arm of the inverter is controlled to be turned on and the lower bridge arm is turned off; if the subtraction result is less than 0, the upper bridge arm of the inverter is controlled to be turned off and the lower bridge arm is turned on.

7. The single-phase transformer area power management control method as claimed in claim 5, characterized in that: The transformer load reactive power and harmonic compensation unit is controlled according to the generation method of the switch tube control pulse, including: The current signal I detected by the load side current transformer L Calculate the active current part I p , get the load reactive power and harmonic current value I that needs to be compensated L -I p ; The rated terminal voltage of the capacitor of the DC energy storage unit is subtracted from the actual terminal voltage detected by the capacitor terminal voltage transformer, and the difference is multiplied by the active current part I after PID adjustment. p Get the active current I required to maintain the capacitor terminal voltage p1 ; The difference between the actual terminal voltage of the capacitor connected to the upper bridge arm and the actual terminal voltage of the capacitor connected to the lower bridge arm of the DC energy storage unit is obtained by PID regulation to obtain the regulating current I for regulating the unbalanced voltage at the capacitor terminal. bp ; Will I L -I p -I p1 +I bp The actual current detected by the output current transformer of the transformer load reactive and harmonic compensation unit is subtracted from the actual current, and the subtraction result is subtracted from the triangular carrier after PID adjustment. If the result is greater than or equal to 0, the upper bridge arm of the inverter is controlled to be turned on and the lower bridge arm is turned off; if the result is less than 0, the upper bridge arm of the inverter is controlled to be turned off and the lower bridge arm is turned on.

8. The single-phase transformer area power management control method as claimed in claim 7, characterized in that: The calculation of the active current part Ip of the current signal IL detected by the load-side current transformer includes: The electrical angle wt obtained by the phase-locked loop through the actual load voltage detected by the load-side voltage transformer is used to calculate 2*I L *sin(wt) is filtered through a low-pass filter to obtain the DC part, which is the active current peak value I pm , and then calculate I pm *sin(wt) can get the instantaneous active current I p .

9. The single-phase transformer area power management control method as claimed in claim 5, characterized in that: The control method according to the mechanical switch includes: A mechanical switch connected in parallel with the isolation transformer of the transformer output voltage regulating unit is controlled to be disconnected when the transformer output voltage regulating unit is put into use, and when the voltage on the power supply side of the low-voltage circuit output by the single-phase transformer station is within a qualified range, the upper and lower bridge arms of the inverter of the transformer output voltage regulating unit are closed, and the mechanical switch is controlled to be closed at the same time.

10. The single-phase transformer area power management control method according to claim 9, characterized in that: The control method according to the mechanical switch also includes: The mechanical switch connected in series with the secondary output terminal of the transformer is controlled to be closed when the transformer output voltage regulating unit is put into use. When the current signal detected by the load-side current transformer is short-circuited, the switch is disconnected, so that only the primary side of the isolation transformer is connected in series as the excitation winding in the low-voltage circuit output by the single-phase transformer station area, thereby limiting the short-circuit current.

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