Composite voltage sag detection method and system for energy storage ups system

Abstract

The application discloses a composite voltage sag detection method and system for an energy storage type UPS system, the composite voltage sag detection method comprising: obtaining a power grid voltage sag detection result Sag1 and a power grid voltage sag detection result Sag2 through a first voltage sag detection module and a second voltage sag detection module respectively, performing a logic OR operation on the power grid voltage sag detection result Sag1 and the power grid voltage sag detection result Sag2 to obtain a power grid voltage sag detection result, and determining whether a voltage sag state exists according to the power grid voltage sag detection result. The method adopts a composite detection technology combining the first voltage sag detection module and the second voltage sag detection module, and can effectively detect the power grid voltage sag under the conditions that a single-phase power grid voltage drops to 0.895 times of a rated power grid voltage, two-phase power grid voltages drop to 0.895 times of the rated power grid voltage, and three-phase power grid voltages drop to 0.895 times of the rated power grid voltage.

Description

Technical Field

[0001] This invention relates to the field of power grid voltage fluctuation detection technology, and specifically to a composite voltage sag detection method and system for energy storage UPS systems. Background Technology

[0002] As the core of the information technology industry, the semiconductor industry is a strategic, fundamental, and pioneering industry supporting national economic and social development and ensuring national security. The semiconductor industry belongs to the high-end manufacturing sector, using a large number of high-precision instruments and equipment, making it highly susceptible to power quality issues. Power quality problems leading to equipment downtime can cause direct and indirect economic losses of up to hundreds of millions of yuan. Furthermore, with the development of 5G and the Industrial Internet, the internet is further integrating with traditional industries, and data centers will become a fundamental and pioneering industry upon which various sectors rely for development. Data centers have extremely high requirements for power quality; power quality problems causing equipment downtime and business interruptions can result in huge losses for enterprises. The intelligent manufacturing industry involves continuous production processes, and production stoppages due to power quality problems incur enormous downtime costs. Therefore, voltage sags and voltage interruptions are the most significant power quality problems faced by industries such as semiconductors, data centers, and intelligent manufacturing. Energy storage UPS systems, while ensuring stable power supply to power facilities, can also participate in grid peak shaving and valley filling, reducing the cost of energy storage UPS systems and optimizing their configuration, giving them enormous market potential. The main technical challenge facing energy storage UPS systems is to quickly and accurately detect voltage dips under various operating conditions, thereby minimizing the economic losses caused by voltage dips.

[0003] Therefore, scholars at home and abroad have conducted a lot of research on voltage sag detection. For example, the Chinese invention patent application publication (CN 101793918 A) published on August 4, 2010, entitled "A Voltage Sag Detection Method", discloses a three-phase voltage sag detection method. This method uses an equivalent filtering network to filter the output of the conventional dq algorithm, avoiding harmonic amplification and realizing rapid tracking and detection of the grid voltage. For example, the 2012 IEEE paper "Y. Kumsuwan and Y. Sillapawicharn. A fast synchronously rotating reference frame-based voltagesag detection under practical grid voltages for voltage sag compensation systems, 6th IET International Conference on Power Electronics, Machines and Drives (PEMD 2012), 2012, pp. 1-5." proposes a voltage sag detection method based on a synchronously rotating coordinate system. This method cancels the second harmonic component generated by the synchronously rotating coordinate transformation under three-phase unbalanced voltage sag conditions by using differentiation, thereby realizing the detection of voltage drops in any phase. For example, the Chinese invention patent application publication (CN 107870285 A) published on April 3, 2018, entitled "Fast Detection Algorithm for Grid Voltage Drop Based on Phase Shift", discloses a fast detection method for grid voltage drop based on phase shift. This method constructs three new sets of symmetrical three-phase voltages by delaying the phase of an all-pass filter, and uses the conventional dq algorithm to quickly determine the asymmetrical voltage drop of the three phases of the grid.

[0004] However, the "A method for detecting voltage sags" published in Chinese invention patent application (CN 101793918 A) on August 4, 2010, is prone to deviation and inaccuracy when the grid voltage experiences phase shift or phase reversal. Furthermore, this method cannot effectively detect voltage sags under extreme conditions, i.e., when the grid voltage of any phase drops to 0.895 times the rated grid voltage. The 2012 IEEE paper "Y. Kumsuwan and Y. Sillapawicharn. A fast synchronously rotating reference frame-based voltagesag detection under practical grid voltages for voltage sag compensation systems, 6th IET International Conference on Power Electronics, Machines and Drives (PEMD2012), 2012, pp. 1-5" proposes a voltage sag detection method based on a synchronous rotating coordinate system. However, this method uses differential calculations, which makes it sensitive to voltage harmonics. When the three-phase grid voltage drops simultaneously or when the grid voltage experiences phase shift or phase reversal, the sag detection results are prone to deviation and inaccuracy. The Chinese invention patent application publication (CN 107870285 A) published on April 3, 2018, entitled "Fast Detection Algorithm for Grid Voltage Drop Based on Phase Shift," cannot effectively detect grid voltage drops or phase reversals.

[0005] Therefore, how to achieve rapid and accurate voltage detection is a technical problem that energy storage UPS systems urgently need to solve. Summary of the Invention

[0006] In view of the above problems, the present invention is proposed to provide a method and system for detecting composite voltage sags in energy storage UPS systems that overcomes or at least partially solves the above problems.

[0007] According to one aspect of the present invention, a composite voltage sag detection method for an energy storage UPS system is provided, comprising: obtaining grid voltage sag detection result Sag1 and grid voltage sag detection result Sag2 respectively through a first voltage sag detection module and a second voltage sag detection module; performing a logical OR operation on grid voltage sag detection result Sag1 and grid voltage sag detection result Sag2 to obtain grid voltage sag detection result Sag; and determining whether the system is in a voltage sag state based on grid voltage sag detection result Sag.

[0008] Optionally, the method by which the first voltage sag detection module obtains the grid voltage sag detection result Sag1 includes:

[0009] Sample the actual value of the three-phase grid voltage, and obtain the phase of the three-phase grid voltage after phase locking;

[0010] Based on the obtained three-phase grid voltage phases, the actual values ​​of the three-phase grid voltages are transformed into a two-phase rotating coordinate system (dq) to obtain the d-axis component U. gd and q-axis component U gq ;

[0011] The q-axis component U is filtered by an all-pass filter. gq The q-axis component U of the three-phase grid voltage is obtained by phase shifting by 90°. gq1 , will U gq1 With d-axis component U gd The three-phase power grid voltage amplitude U is obtained by superposition. gm ;

[0012] Filtering out three-phase power grid voltage amplitude U gm The harmonics in the three-phase grid voltage are then compared with the threshold for grid voltage sag. When the amplitude of the three-phase grid voltage after harmonic filtering is less than the threshold for grid voltage sag, Sag1 = 1, and a grid voltage sag occurs. When the amplitude of the three-phase grid voltage after harmonic filtering is greater than or equal to the threshold for grid voltage sag, Sag1 = 0, and no grid voltage sag occurs.

[0013] Optionally, the filtering of three-phase grid voltage amplitude U gm Methods for filtering out middle harmonics include sequentially using a band-stop filter and a low-pass filter to filter out the three-phase grid voltage amplitude U. gm Harmonics in the middle.

[0014] Optionally, the band-stop filter filters out the three-phase grid voltage amplitude U. gm The 6th harmonic.

[0015] Optionally, the method by which the second voltage sag detection module obtains the grid voltage sag detection result Sag2 includes:

[0016] S1. Sample the actual values ​​of the three-phase grid voltages. The voltages of phases A, B, and C are denoted as U. ga U gb U gc ;

[0017] S2. The actual grid voltage U of phase A is obtained by shifting the phase of the actual grid voltage by 90° using a full-pass filter. ga1 ;

[0018] S3, change the actual value of the A-phase grid voltage U ga The actual value of the A-phase grid voltage U after a 90° phase shift ga1 The amplitude U of the A-phase grid voltage was calculated. gam ;

[0019] S4. Filter out the voltage amplitude U of phase A of the power grid. gam The higher harmonics in the filter are then compared with the threshold of the grid voltage sag to obtain the A-phase grid voltage sag detection result Sag_a. The A-phase grid voltage amplitude U after filtering out the higher harmonics is then calculated. gam When the voltage is less than the threshold of grid voltage sag, Sag_a = 1, and a grid voltage sag occurs. When the amplitude of the A-phase grid voltage Ugam after filtering out higher harmonics is greater than or equal to the threshold of grid voltage sag, Sag_a = 0, and no grid voltage sag occurs.

[0020] S5. Repeat steps S2 to S4 above for the B-phase grid voltage and the C-phase grid voltage to obtain the B-phase grid voltage sag detection result Sag_b and the C-phase grid voltage sag detection result Sag_c respectively. Perform a logical OR operation on Sag_a, Sag_b, and Sag_c to obtain the grid voltage sag detection result Sag2.

[0021] Optionally, the actual value U of the A-phase grid voltage... ga The actual value of the A-phase grid voltage U after a 90° phase shift ga1 The voltage amplitude U of phase A of the power grid was calculated. gam The formula is

[0022] According to another aspect of the present invention, a composite voltage sag detection system is provided, comprising:

[0023] The first voltage sag detection module is used to obtain the grid voltage sag detection result Sag1.

[0024] The second voltage sag detection module is used to obtain the grid voltage sag detection result Sag2.

[0025] The logic unit performs a logical OR operation on the grid voltage sag detection results Sag1 and Sag2 to obtain the grid voltage sag detection result Sag, and determines whether the grid voltage sag is in a voltage sag state based on the grid voltage sag detection result Sag.

[0026] According to another aspect of the present invention, a composite voltage sag detection device for an energy storage UPS system is provided, comprising: a memory and a processor;

[0027] The memory is used to store program instructions;

[0028] The processor is used to call program instructions in the memory to execute any of the above-described composite voltage sag detection methods for energy storage UPS systems.

[0029] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein computer program instructions are stored therein, and when executed, the computer program instructions implement any of the above-described composite voltage sag detection methods for energy storage UPS systems.

[0030] According to another aspect of the present invention, a computer program product is provided, comprising a computer program that, when executed by a processor, implements any of the above-described composite voltage sag detection methods for energy storage UPS systems.

[0031] As described above, the technical solution of this invention provides a composite voltage sag detection method for energy storage UPS systems. This method employs a composite voltage sag detection technology combining a first voltage sag detection module and a second voltage sag detection module. The method includes: the first voltage sag detection module uses a full-pass filter for phase shifting, making it insensitive to voltage harmonics, and uses a combination of a band-stop filter and a low-pass filter for filtering. This results in more accurate voltage sag detection when the three-phase grid voltage drops simultaneously or when the grid voltage experiences phase shift or phase reversal. The second voltage sag detection module uses a full-pass filter to simulate virtual voltages orthogonal to the A, B, and C phase grid voltages, respectively. After corresponding mathematical operations and low-pass filtering, the voltage amplitudes of the A, B, and C phase grid voltages are obtained. Even under extreme conditions such as a single-phase grid voltage dropping to 0.895 times the rated grid voltage, a two-phase grid voltage dropping to 0.895 times the rated grid voltage, and a three-phase grid voltage dropping to 0.895 times the rated grid voltage, the method can still accurately and effectively detect grid voltage sags. Attached Figure Description

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0033] Figure 1 A block diagram of an energy storage UPS system is shown.

[0034] Figure 2 A block diagram illustrating the voltage sag detection principle is shown.

[0035] Figure 3a The three-phase grid voltage waveforms are shown when the A-phase grid voltage drops to 0.895 times the rated grid voltage using the detection method of this invention.

[0036] Figure 3b The waveform of the voltage sag detection result Sag when the A-phase grid voltage drops to 0.895 times the rated grid voltage using the detection method of the present invention is shown.

[0037] Figure 4a The three-phase grid voltage waveforms when the grid voltage of phases A and B drops to 0.895 times the rated grid voltage, using the detection method of this invention;

[0038] Figure 4b The waveform of the voltage sag detection result Sag when the grid voltage of phases A and B drops to 0.895 times the rated grid voltage using the detection method of this invention;

[0039] Figure 5a The three-phase grid voltage waveforms when the grid voltage of phases A, B, and C drops to 0.895 times the rated grid voltage, using the detection method of this invention;

[0040] Figure 5b The waveform of the voltage sag detection result Sag when the grid voltage of phases A, B, and C drops to 0.895 times the rated grid voltage using the detection method of this invention.

[0041] Figure 6a The waveform of the three-phase power grid voltage when the voltage of phase A drops to 0 under the condition that the detection method of the present invention is used.

[0042] Figure 6b The waveform of the voltage sag detection result Sag when the grid voltage of phase A drops to 0 under the condition that the detection method of the present invention is used;

[0043] Figure 7a The three-phase grid voltage waveforms when the A and B phase grid voltages drop to 0 under the condition that the detection method of this invention is used;

[0044] Figure 7b The waveform of the voltage sag detection result Sag when the grid voltage of phases A and B drops to 0 under the condition that the detection method of the present invention is used;

[0045] Figure 8a The three-phase grid voltage waveforms when the A, B, and C phase grid voltages drop to 0 under the condition that the detection method of this invention is used.

[0046] Figure 8b The waveform of the voltage sag detection result Sag when the grid voltage drops to 0 under the condition of grid voltage drop of phases A, B, and C using the detection method of the present invention;

[0047] Figure 9a The three-phase grid voltage waveform is shown when the detection method of this invention is used under the condition that the A-phase grid voltage deviates by 90°.

[0048] Figure 9b The waveform of the voltage sag detection result Sag when the detection method of the present invention is used under the condition of 90° voltage deviation of the A-phase power grid;

[0049] Figure 10a The three-phase grid voltage waveform is shown when the detection method of this invention is used under the condition that the A-phase grid voltage flips by 180°.

[0050] Figure 10b The waveform of the voltage sag detection result Sag when the detection method of the present invention is used under the condition of 180° voltage reversal in phase A of the power grid. Detailed Implementation

[0051] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0052] Figure 1 The diagram shows the principle block diagram of the energy storage UPS system. When the grid voltage drops or is interrupted, the system quickly identifies and controls the fast switch to disconnect the grid through the voltage drop detection algorithm. At the same time, it controls the energy storage UPS system to supply power to the load, so as to achieve high-quality, continuous and stable power supply under grid voltage drop mode.

[0053] Figure 2 A schematic block diagram of a composite voltage sag detection method for an energy storage UPS system according to an embodiment of the present invention is shown. Figure 2As shown, the method includes: obtaining grid voltage sag detection results Sag1 and Sag2 through a first voltage sag detection module and a second voltage sag detection module, respectively; performing a logical OR operation on the grid voltage sag detection results Sag1 and Sag2 to obtain the grid voltage sag detection result Sag; and determining whether the grid voltage sag is in a voltage sag state based on the grid voltage sag detection result Sag.

[0054] In one embodiment of the present invention, the method for the first voltage sag detection module to obtain the grid voltage sag detection result Sag1 includes:

[0055] Sample the actual value of the three-phase grid voltage, and obtain the phase of the three-phase grid voltage after phase locking;

[0056] Based on the obtained three-phase grid voltage phases, the actual values ​​of the three-phase grid voltages are transformed into a two-phase rotating coordinate system (dq) to obtain the d-axis component U. gd and q-axis component U gq ;

[0057] The q-axis component U is filtered by an all-pass filter. gq The q-axis component U of the three-phase grid voltage is obtained by phase shifting by 90°. gq1 , will U gq1 With d-axis component U gd The three-phase power grid voltage amplitude U is obtained by superposition. gm ;

[0058] Filtering out three-phase power grid voltage amplitude U gm The harmonics in the three-phase grid voltage are then compared with the threshold for grid voltage sag. When the amplitude of the three-phase grid voltage after harmonic filtering is less than the threshold for grid voltage sag, Sag1 = 1, and a grid voltage sag occurs. When the amplitude of the three-phase grid voltage after harmonic filtering is greater than or equal to the threshold for grid voltage sag, Sag1 = 0, and no grid voltage sag occurs.

[0059] In one embodiment of the present invention, in the above method, the filtering of the three-phase power grid voltage amplitude U gm Methods for filtering out middle harmonics include sequentially using a band-stop filter and a low-pass filter to filter out the three-phase grid voltage amplitude U. gm Harmonics in the system. In specific implementation, the band-stop filter filters out the three-phase grid voltage amplitude U. gm The 6th harmonic.

[0060] In one embodiment of the present invention, the method by which the second voltage sag detection module obtains the grid voltage sag detection result Sag2 includes:

[0061] S1. Sample the actual values ​​of the three-phase grid voltages. The voltages of phases A, B, and C are denoted as U.ga U gb U gc ;

[0062] S2. The actual grid voltage U of phase A is obtained by shifting the phase of the actual grid voltage by 90° using a full-pass filter. ga1 ;

[0063] S3, change the actual value of the A-phase grid voltage U ga The actual value of the A-phase grid voltage U after a 90° phase shift ga1 The amplitude U of the A-phase grid voltage was calculated. gam ;

[0064] S4. Filter out the voltage amplitude U of phase A of the power grid. gam The higher harmonics in the filter are then compared with the threshold of the grid voltage sag to obtain the A-phase grid voltage sag detection result Sag_a. The A-phase grid voltage amplitude U after filtering out the higher harmonics is then calculated. gam When the voltage is less than the threshold of grid voltage sag, Sag_a = 1, and a grid voltage sag occurs. When the amplitude of the A-phase grid voltage Ugam after filtering out higher harmonics is greater than or equal to the threshold of grid voltage sag, Sag_a = 0, and no grid voltage sag occurs.

[0065] S5. Repeat steps S2 to S4 above for the B-phase grid voltage and the C-phase grid voltage to obtain the B-phase grid voltage sag detection result Sag_b and the C-phase grid voltage sag detection result Sag_c respectively. Perform a logical OR operation on Sag_a, Sag_b, and Sag_c to obtain the grid voltage sag detection result Sag2.

[0066] Furthermore, the actual value U of the A-phase grid voltage... ga The actual value of the A-phase grid voltage U after a 90° phase shift ga1 The voltage amplitude U of phase A of the power grid was calculated. gam The formula is

[0067] According to another aspect of the present invention, a composite voltage sag detection system is provided, comprising:

[0068] The first voltage sag detection module is used to obtain the grid voltage sag detection result Sag1.

[0069] The second voltage sag detection module is used to obtain the grid voltage sag detection result Sag2.

[0070] The logic unit performs a logical OR operation on the grid voltage sag detection results Sag1 and Sag2 to obtain the grid voltage sag detection result Sag, and determines whether the grid voltage sag is in a voltage sag state based on the grid voltage sag detection result Sag.

[0071] According to another aspect of the present invention, a composite voltage sag detection device for an energy storage UPS system is provided, comprising: a memory and a processor;

[0072] The memory is used to store program instructions;

[0073] The processor is used to call program instructions in the memory to execute any of the above-described composite voltage sag detection methods for energy storage UPS systems.

[0074] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein computer program instructions are stored therein, and when executed, the computer program instructions implement any of the above-described composite voltage sag detection methods for energy storage UPS systems.

[0075] According to another aspect of the present invention, a computer program product is provided, comprising a computer program that, when executed by a processor, implements any of the above-described composite voltage sag detection methods for energy storage UPS systems.

[0076] The present invention will be described in detail below with reference to specific embodiments:

[0077] The method for the first voltage sag detection module to obtain the grid voltage sag detection result Sag1 includes:

[0078] Step 1: Sample the actual value of the three-phase grid voltage and record it as U. ga U gb U gc ;

[0079] Step 2, the actual value U of the three-phase grid voltage sampled in Step 1 ga U gb U gc To obtain the phase θ of the three-phase grid voltage through phase-locked loop, in order to minimize the delay caused by the filtering stage, the PLL phase-locked loop adopts a single synchronous coordinate system software phase-locked loop.

[0080] Step 3: Transform the actual three-phase grid voltage U sampled in Step 1 into synchronous rotating coordinates. ga U gb U gc Transformation of three-phase grid voltage d-axis component U in a rotating coordinate system gd and the q-axis component of the three-phase power grid voltage U gq The formula for its calculation is:

[0081]

[0082] Step 4: The q-axis component U of the three-phase grid voltage obtained in Step 3 is filtered through an all-pass filter. gq The q-axis component U of the three-phase grid voltage after a 90° phase shift is obtained. gq1 The purpose of using a phase-shifting all-pass filter is to avoid the influence of voltage harmonics on the sag detection results and ensure the accuracy of the sag detection results. The transfer function H of the all-pass filter used is... apf1 The expression for (s) is:

[0083]

[0084] Where ω apf1 =200π;

[0085] Step 5, convert the q-axis component U of the three-phase grid voltage obtained in Step 4 after a 90° phase shift. gq1 The d-axis component U of the three-phase grid voltage obtained in step 3 gd The three-phase power grid voltage amplitude U is obtained by superposition. gm ;

[0086] Step 6, convert the three-phase grid voltage amplitude U obtained in step 5 to... gm The third-phase grid voltage amplitude U is obtained by filtering out the 6th harmonic using a band-stop filter. gm1 The reason is that the actual power grid mainly contains 5th and 7th harmonics, which are transformed into 6th harmonics after synchronous rotating coordinate transformation. The purpose of using a band-stop filter is to filter them out as much as possible. The transfer function of the band-stop filter used is H. bsf1 The expression for (s) is:

[0087]

[0088] Where ω bsf1 =600π, B p1 =83π;

[0089] Step 7: Calculate the amplitude U of the three-phase grid voltage after band-stop filtering obtained in Step 6. gm1 The higher harmonics are further filtered out by a low-pass filter to obtain the three-phase grid voltage amplitude U after band-stop-low-pass filtering. gm2 The low-pass filter used is a Butterworth low-pass filter. To minimize filter delay, a first-order Butterworth low-pass filter is employed, and its transfer function Hlpf1(s) is expressed as follows:

[0090]

[0091] Where ω lpf1 =200π;

[0092] Step 8: Calculate the amplitude U of the three-phase grid voltage after band-stop-low-pass filtering obtained in Step 7. gm2 The voltage sag detection result Sag1 under voltage sag detection module 1 is obtained by comparing it with the threshold of the grid voltage sag. The threshold of the grid voltage sag is usually selected as 90% of the rated grid voltage amplitude. When U gm2 When the voltage is below the threshold of the mains voltage sag, Sag1 = 1, and a mains voltage sag occurs; when U gm2 When the voltage sag is greater than or equal to the threshold of the grid voltage sag, Sag1 = 0, indicating that no grid voltage sag has occurred.

[0093] The method for the second voltage sag detection module to obtain the grid voltage sag detection result Sag2 includes:

[0094] Step 1: Sample the actual value of the three-phase grid voltage and record it as U. ga U gb U gc ;

[0095] Step 2: The actual value U of the A-phase grid voltage sampled in Step 1 is filtered through an all-pass filter. ga The actual value U of the A-phase grid voltage after a 90° phase shift is obtained. ga1 The transfer function H of the all-pass filter used apf2 The expression for (s) is:

[0096]

[0097] Where ω apf2 =100π;

[0098] Step 3, based on the actual value U of the A-phase grid voltage sampled in Step 1. ga The actual value U of the A-phase grid voltage after a 90° phase shift obtained in step 2. ga1 The amplitude U of the A-phase grid voltage was calculated. gam The formula for its calculation is:

[0099]

[0100] Step 4, convert the amplitude U of the A-phase grid voltage obtained in Step 3. gam The high-order harmonics are filtered out by a low-pass filter to obtain the low-pass filtered A-phase grid voltage amplitude U. gam1 The low-pass filter used is a Butterworth low-pass filter. To minimize filter delay, a first-order Butterworth low-pass filter is employed, with a transfer function H. lpf2 The expression for (s) is:

[0101]

[0102] Where ω lpf2 =260π;

[0103] Step 5, convert the low-pass filtered A-phase grid voltage amplitude U obtained in Step 4. gam1 The voltage sag detection result Sag_a for phase A is obtained by comparing it with the threshold of the grid voltage sag. The threshold of the grid voltage sag is usually selected as 90% of the rated grid voltage amplitude. When U gam1 When the voltage is below the threshold for a grid voltage sag, Sag_a = 1, and a grid voltage sag occurs; when U gam1 When the voltage sag is greater than or equal to the threshold of the grid voltage sag, Sag_a = 0, and no grid voltage sag has occurred.

[0104] Step 6: Following the same steps as phase A (steps 2-5), the voltage sag detection results of phase B grid Sag_b and phase C grid Sag_c can be obtained. These results are then logically ORed with the voltage sag detection result of phase A grid Sag_a obtained in step 5 to obtain the voltage sag detection result of grid Sag2 under voltage sag detection module 2.

[0105] The voltage sag detection results output includes:

[0106] The grid voltage sag detection result Sag1 under voltage sag detection module 1 and the grid voltage sag detection result Sag2 under voltage sag detection module 2 are logically ORed to obtain the grid voltage sag detection result Sag under this method.

[0107] Example 1

[0108] Figure 3a The three-phase grid voltage U when the phase A voltage drops to 0.895 times the rated grid voltage is detected using the detection method of this invention. ga U gb U gc Waveform,

[0109] Figure 3b The waveform of the voltage sag detection result Sag when the phase A voltage drops to 0.895 times the rated grid voltage using the detection method of this invention.

[0110] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can effectively detect the grid voltage sag, and the detection time is 7.25ms.

[0111] Example 2

[0112] Figure 4aThe three-phase grid voltage U when the voltage of phases A and B drops to 0.895 times the rated grid voltage, as determined by the detection method of this invention. ga U gb U gc Waveform, Figure 4b The waveform of the voltage sag detection result Sag when the voltage of phases A and B drops to 0.895 times the rated grid voltage using the detection method of this invention.

[0113] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can effectively detect the grid voltage sag, and the detection time is 7.25ms.

[0114] Example 3

[0115] Figure 5a The three-phase grid voltage U when the voltages of phases A, B, and C drop to 0.895 times the rated grid voltage, as determined by the detection method of this invention. ga U gb U gc Waveform, Figure 5b The waveform of the voltage sag detection result Sag when the voltage of phases A, B, and C drops to 0.895 times the rated grid voltage using the detection method of this invention.

[0116] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can effectively detect the grid voltage sag, and the detection time is 4.125ms.

[0117] Example 4

[0118] Figure 6a The three-phase grid voltage U when the phase A voltage drops to 0 under the detection method of this invention. ga U gb U gc Waveform, Figure 6b The waveform of the grid voltage sag detection result Sag is given when the phase A voltage drops to 0 under the condition that the detection method of this invention is used.

[0119] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can quickly and effectively detect grid voltage sags with a detection time of 0.375ms.

[0120] Example 5

[0121] Figure 7aThe three-phase grid voltage U when the voltage of phases A and B drops to 0 under the condition that the voltage of phases B drops to 0 is the detection method of this invention. ga U gb U gc Waveform, Figure 7b The waveform of the grid voltage sag detection result Sag is given when the voltage of phases A and B drops to 0 under the condition that the detection method of this invention is used.

[0122] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can quickly and effectively detect grid voltage sags with a detection time of 0.375ms.

[0123] Example 6

[0124] Figure 8a The three-phase grid voltage U when the voltages of phases A, B, and C drop to 0 under the condition that the voltages of phases A, B, and C drop to 0 is the detection method of this invention. ga U gb U gc Waveform, Figure 8b The waveform of the grid voltage sag detection result Sag is given when the voltage of phases A, B, and C drops to 0 under the condition that the detection method of this invention is used.

[0125] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can quickly and effectively detect grid voltage sags with a detection time of 0.25ms.

[0126] Example 7

[0127] Figure 9a The three-phase grid voltage U when the detection method of this invention is used under the condition of a 90° voltage deviation in phase A. ga U gb U gc Waveform, Figure 9b The waveform of the grid voltage sag detection result Sag is shown when the detection method of this invention is used under the condition of 90° voltage deviation in phase A.

[0128] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can quickly and effectively detect grid voltage sags with a detection time of 0.375ms.

[0129] Example 8

[0130] Figure 10a The three-phase grid voltage U when the detection method of this invention is used under the condition of phase A voltage flipping 180°. ga U gbU gc Waveform, Figure 10b The waveform of the grid voltage sag detection result Sag is shown when the detection method of this invention is used under the condition of 180° voltage reversal in phase A.

[0131] In the simulation, the fundamental effective value of the three-phase grid line voltage is 400V, containing 2% of the 5th harmonic and 2% of the 7th harmonic. The sampling frequency of the three-phase grid voltage is 8kHz. This method can quickly and effectively detect grid voltage sags with a detection time of 0.25ms.

[0132] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0133] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim itself is a separate embodiment of the invention.

[0134] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0135] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0136] The various component embodiments of the present invention can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components in the composite voltage sag detection system for an energy storage UPS system according to embodiments of the present invention. The present invention can also be implemented as a device or apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such programs implementing the present invention can be stored on a computer-readable medium or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0137] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A method for detecting composite voltage sags in an energy storage UPS system, characterized in that, include: The grid voltage sag detection results Sag1 and Sag2 are obtained through the first voltage sag detection module and the second voltage sag detection module, respectively. The grid voltage sag detection results Sag1 and Sag2 are logically ORed to obtain the grid voltage sag detection result Sag. The grid voltage sag detection result Sag is determined based on the grid voltage sag detection result Sag. The method for the first voltage sag detection module to obtain the grid voltage sag detection result Sag1 includes: Sample the actual value of the three-phase grid voltage, and obtain the phase of the three-phase grid voltage after phase locking; Based on the obtained three-phase grid voltage phases, the actual values ​​of the three-phase grid voltages are transformed into a two-phase rotating coordinate system (dq) to obtain the d-axis component U. gd and q-axis component U gq ; The q-axis component U is filtered by an all-pass filter. gq The q-axis component U of the three-phase grid voltage is obtained by phase shifting by 90°. gq1 , will U gq1 With d-axis component U gd The three-phase power grid voltage amplitude U is obtained by superposition. gm ; Filtering out three-phase power grid voltage amplitude U gm The harmonics in the three-phase grid voltage are then compared with the grid voltage sag threshold. When the amplitude of the three-phase grid voltage after harmonic filtering is less than the grid voltage sag threshold, Sag1=1, and a grid voltage sag occurs. When the amplitude of the three-phase grid voltage after harmonic filtering is greater than or equal to the grid voltage sag threshold, Sag1=0, and no grid voltage sag occurs. The method for the second voltage sag detection module to obtain the grid voltage sag detection result Sag2 includes: S1. Sample the actual values ​​of the three-phase grid voltages. The voltages of phases A, B, and C are denoted as U. ga U gb U gc ; S2. The actual grid voltage U of phase A is obtained by shifting the phase of the actual grid voltage by 90° using a full-pass filter. ga1 ; S3, change the actual value of the A-phase grid voltage U ga The actual value of the A-phase grid voltage U after a 90° phase shift ga1 The amplitude U of the A-phase grid voltage was calculated. gam ; S4. Filter out the voltage amplitude U of phase A of the power grid. gam The higher harmonics in the filter are then compared with the threshold of the grid voltage sag to obtain the A-phase grid voltage sag detection result Sag_a. The A-phase grid voltage amplitude U after filtering out the higher harmonics is then calculated. gam When the voltage is less than the threshold for a grid voltage sag, Sag_a = 1, and a grid voltage sag occurs. The amplitude U of the A-phase grid voltage after filtering out higher harmonics... gam When the voltage sag is greater than or equal to the threshold of the grid voltage sag, Sag_a = 0, indicating that no grid voltage sag has occurred. S5. Repeat steps S2 to S4 above for the B-phase grid voltage and the C-phase grid voltage to obtain the B-phase grid voltage sag detection result Sag_b and the C-phase grid voltage sag detection result Sag_c respectively. Perform a logical OR operation on Sag_a, Sag_b, and Sag_c to obtain the grid voltage sag detection result Sag2.

2. The composite voltage sag detection method according to claim 1, characterized in that: The filtering of three-phase power grid voltage amplitude U gm Methods for filtering out middle harmonics include sequentially using a band-stop filter and a low-pass filter to filter out the three-phase grid voltage amplitude U. gm Harmonics in the middle.

3. The composite voltage sag detection method according to claim 2, characterized in that: The band-stop filter filters out the three-phase grid voltage amplitude U. gm The 6th harmonic in the middle.

4. The composite voltage sag detection method according to claim 1, characterized in that, The actual value of phase A grid voltage Uga and the actual value of phase A grid voltage U after 90° phase shift are... ga1 The voltage amplitude U of phase A of the power grid was calculated. gam The formula is .

5. A composite voltage sag detection system, characterized in that, include: The first voltage sag detection module is used to obtain the grid voltage sag detection result Sag1. The second voltage sag detection module is used to obtain the grid voltage sag detection result Sag2. The logic unit performs a logical OR operation on the grid voltage sag detection results Sag1 and Sag2 to obtain the grid voltage sag detection result Sag, and determines whether the grid voltage sag is in a voltage sag state based on the grid voltage sag detection result Sag. The first voltage sag detection module is used for: Sample the actual value of the three-phase grid voltage, and obtain the phase of the three-phase grid voltage after phase locking; Based on the obtained three-phase grid voltage phases, the actual values ​​of the three-phase grid voltages are transformed into a two-phase rotating coordinate system (dq) to obtain the d-axis component U. gd and q-axis component U gq ; The q-axis component U is filtered by an all-pass filter. gq The q-axis component U of the three-phase grid voltage is obtained by phase shifting by 90°. gq1 , will U gq1 With d-axis component U gd The three-phase power grid voltage amplitude U is obtained by superposition. gm ; Filtering out three-phase power grid voltage amplitude U gm The harmonics in the three-phase grid voltage are then compared with the grid voltage sag threshold. When the amplitude of the three-phase grid voltage after harmonic filtering is less than the grid voltage sag threshold, Sag1=1, and a grid voltage sag occurs. When the amplitude of the three-phase grid voltage after harmonic filtering is greater than or equal to the grid voltage sag threshold, Sag1=0, and no grid voltage sag occurs. The second voltage sag detection module is used for: S1. Sample the actual values ​​of the three-phase grid voltages. The voltages of phases A, B, and C are denoted as U. ga U gb U gc ; S2. The actual grid voltage U of phase A is obtained by shifting the phase of the actual grid voltage by 90° using a full-pass filter. ga1 ; S3, change the actual value of the A-phase grid voltage U ga The actual value of the A-phase grid voltage U after a 90° phase shift ga1 The amplitude U of the A-phase grid voltage was calculated. gam ; S4. Filter out the voltage amplitude U of phase A of the power grid. gam The higher harmonics in the filter are then compared with the threshold of the grid voltage sag to obtain the A-phase grid voltage sag detection result Sag_a. The A-phase grid voltage amplitude U after filtering out the higher harmonics is then calculated. gam When the voltage is less than the threshold for a grid voltage sag, Sag_a = 1, and a grid voltage sag occurs. The amplitude U of the A-phase grid voltage after filtering out higher harmonics... gam When the voltage sag is greater than or equal to the threshold of the grid voltage sag, Sag_a = 0, indicating that no grid voltage sag has occurred. S5. Repeat steps S2 to S4 above for the B-phase grid voltage and the C-phase grid voltage to obtain the B-phase grid voltage sag detection result Sag_b and the C-phase grid voltage sag detection result Sag_c respectively. Perform a logical OR operation on Sag_a, Sag_b, and Sag_c to obtain the grid voltage sag detection result Sag2.

6. A composite voltage sag detection device for energy storage UPS systems, characterized in that, include: Memory and processor; The memory is used to store program instructions; The processor is used to call program instructions in the memory to execute the composite voltage sag detection method for energy storage UPS systems as described in any one of claims 1-4.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions, which, when executed, implement the composite voltage sag detection method for an energy storage UPS system as described in any one of claims 1-4.

8. A computer program product, comprising a computer program, characterized in that: When executed by a processor, the computer program implements the composite voltage sag detection method for an energy storage UPS system as described in any one of claims 1-4.

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