Overload capability evaluation method of full-bridge and half-bridge hybrid MMC

Abstract

The invention discloses a full-bridge and half-bridge hybrid MMC overload capacity evaluation method, which comprises the following steps of: establishing an experimental platform, continuously changing the magnitude of test simulation current, and respectively obtaining a heat dissipation evaluation factor and a power factor angle evaluation factor of the full-bridge and half-bridge hybrid MMC working in an overload current state, so as to evaluate the overload capacity of the full-bridge and half-bridge hybrid MMC. And finally, determining an overload capacity evaluation factor of the full-bridge and half-bridge hybrid MMC, and verifying the overload capacity of the full-bridge and half-bridge hybrid MMC. According to the invention, the full-bridge and half-bridge hybrid MMC overload capacity evaluation factor is used to evaluate the overload capacity of the full-bridge and half-bridge hybrid MMC, the overload capacity of the full-bridge and half-bridge hybrid MMC can be evaluated accurately and quickly, and a basis is provided for the evaluation of the overload capacity of the full-bridge and half-bridge hybrid MMC.

Description

Technical Field

[0001] The invention belongs to the field of performance evaluation of high-voltage power electronic equipment, and in particular relates to an overload capacity evaluation method for a full-half-bridge hybrid MMC. Technical Background

[0002] With the continuous development of ultra-high voltage flexible direct current transmission technology in my country, the full half-bridge hybrid MMC is an extremely flexible and efficient power electronic device, which is mainly used in high voltage direct current transmission, flexible direct current transmission, ultra-high voltage flexible direct current transmission and renewable energy grid connection, etc. It can improve the stability of current transmission in the power grid, increase the distance of power transmission, and help unstable power sources to be smoothly integrated into the power grid. At the same time, when the power grid fails, it can provide important support for it, so that the fault can be quickly resolved. However, when the power grid is in certain emergency situations or special circumstances, such as serious or long-term failures in the power grid, peak power demand, natural disasters, etc., the system will become very unstable, which will cause the full half-bridge hybrid MMC to work in an overload situation. Long-term overload will cause the full half-bridge hybrid MMC to be damaged due to the high temperature of the internal structure, and the working efficiency will drop sharply, and the life will be greatly shortened. However, there are very few methods for evaluating the overload capacity of the full half-bridge hybrid MMC at present, so there is an urgent need for an overload capacity evaluation method for the full half-bridge hybrid MMC. Summary of the invention

[0003] In view of the above technical problems, the purpose of the present invention is to propose an overload capacity evaluation method for a full-half-bridge hybrid MMC, which can well evaluate the overload capacity of the full-half-bridge hybrid MMC under overload current, and is characterized by comprising the following steps:

[0004] Step 1: Build a full half-bridge hybrid MMC overload capacity test platform

[0005] An overload capacity test platform for a full-half-bridge hybrid MMC is constructed, comprising a test box (1), a full-half-bridge hybrid MMC (2), a heat sink performance test bench (3), a first temperature sensor (4), a second temperature sensor (5), a third temperature sensor (6), a fourth temperature sensor (7), a power analyzer (8), a test simulation power supply (9), a timing device (10), and a computer terminal (11), wherein:

[0006] The magnitude of the current of the test simulation power supply (9) is controlled by a computer terminal (11), and the test simulation power supply (9) supplies power to the full half-bridge hybrid MMC (2). The magnitude of the current is changed by the computer terminal (11) to simulate the overload condition of the full half-bridge hybrid MMC (2); the first temperature sensor (4) is placed below the full half-bridge hybrid MMC (2) to measure the temperature below, the second temperature sensor (5) is placed above the full half-bridge hybrid MMC (2) to measure the temperature above, the third temperature sensor (6) is placed on the right side of the full half-bridge hybrid MMC (2) to measure the temperature on the right side, and the fourth temperature sensor (7) is placed on the left side of the full half-bridge hybrid MMC (2) to measure the temperature on the left side. The temperature and heat sink performance test bench (3) are connected to four temperature sensors to obtain the heat dissipation evaluation factor of the full half-bridge hybrid MMC (2), and the heat dissipation evaluation factor is transmitted to the computer terminal (11); the power analyzer (8) is connected to the full half-bridge hybrid MMC (2) to measure the current, voltage and power of the full half-bridge hybrid MMC (2) under an overload state to obtain the power factor angle evaluation factor of the full half-bridge hybrid MMC (2), and the power factor angle evaluation factor is transmitted to the computer terminal (11); the timing device (10) is connected to the computer terminal (11) to record the operation time of the full half-bridge hybrid MMC (2) in the test box (1) under the overload condition;

[0007] Step 2: Calculate the heat dissipation evaluation factor of the full-half-bridge hybrid MMC under overload conditions

[0008] The current is increased through the computer terminal (11) so that the current in the full half-bridge hybrid MMC (2) reaches the rated current, which is recorded as I arm , in A, the running time of the full half-bridge hybrid MMC (2) is 1 min, at which time the temperature measured by the first temperature sensor (4) is recorded as T0, in °C, the temperature measured by the second temperature sensor (5) is recorded as T1, in °C, the temperature measured by the third temperature sensor (6) is recorded as T2, in °C, the temperature measured by the fourth temperature sensor (7) is recorded as T3, in °C, and the current of the computer terminal (11) is continuously increased to I arm To prevent the full half-bridge hybrid MMC (2) from being destroyed due to excessive current exceeding the rated current, the current is increased by 0.1 times I arm , the increase in current is 0.1I arm , 0.2I arm , 0.3I arm , 0.4I arm , 0.5I arm , the operation time of the full half-bridge hybrid MMC (2) at each current is still 1 minute, and the temperature measured by the first temperature sensor (4) is recorded as T aiThe temperature measured by the second temperature sensor (5) is denoted as T bi The temperature measured by the third temperature sensor (6) is denoted as T ci The temperature measured by the fourth temperature sensor (7) is denoted as T di , where i = 1, 2, 3, 4, 5, and the above temperature units are all in ° C. The heat sink performance test bench (3) analyzes and calculates the temperature values ​​measured by the four temperature sensors;

[0009] The heat dissipation evaluation factor α under overload can be obtained by formula (1): s :

[0010]

[0011] Step 3: Calculate the power factor angle evaluation factor of the full-half-bridge hybrid MMC under overload conditions

[0012] The current is increased through the computer terminal (11) so that the current in the full half-bridge hybrid MMC (2) reaches the rated current, which is recorded as I arm , in A, the running time of the full half-bridge hybrid MMC (2) is 1 min, at which time the current value measured by the power analyzer (8) is I arm , in A, the voltage value measured by the power analyzer (8) is U smN , in V, the power value measured by the power analyzer (8) is P m , in W, continue to increase the current of the computer terminal (11), with I arm To prevent the full half-bridge hybrid MMC (2) from being destroyed due to excessive current exceeding the rated current, the current is increased by 0.1 times I arm , the current is increased by 0.1I arm , 0.2I arm , 0.3I arm , 0.4I arm , 0.5I arm The operation time of the full half-bridge hybrid MMC (2) at each current is still 1 min, and the current value measured by the power analyzer (8) is recorded as I i , the unit is A, and the voltage value measured by the power analyzer (8) is recorded as U i , in V, the power value measured by the power analyzer (8) is recorded as P i , the unit is W, where i=1, 2, 3, 4, 5, the power analyzer (8) analyzes and calculates the measured current, voltage and power data;

[0013] The power factor angle evaluation factor β under overload can be obtained by formula (2): j :

[0014]

[0015] Wherein f is the frequency of the test simulation power supply (9) and is 50 Hz;

[0016] Step 4: Calculate the overload capacity evaluation factor of the full half-bridge hybrid MMC

[0017] The overload capacity evaluation factor σ of the full half-bridge hybrid MMC is obtained by formula (3): g :

[0018]

[0019] Step 5: Evaluate the overload capability of the full-half-bridge hybrid MMC

[0020] The overload capacity of the full half-bridge hybrid MMC is evaluated by formula (3). If 1<σ g ≤1.18 indicates good overload capacity; if 1.18<σ g ≤1.28 indicates that the overload capacity is average; if σ g >1.28 indicates that the overload capacity is very poor, and the current in the full-half-bridge hybrid MMC needs to be adjusted to prevent internal failure of the full-half-bridge hybrid MMC under overload conditions, causing damage to the internal devices of the full-half-bridge hybrid MMC and rendering the full-half-bridge hybrid MMC unable to work normally.

[0021] The beneficial effect of the present invention lies in that, by building a test platform, the influence of the combined influence of heat dissipation and power factor angle factors on the overload capacity of the full half-bridge hybrid MMC is comprehensively considered, and a calculation method is provided, which can accurately calculate the overload capacity evaluation factor of the full half-bridge hybrid MMC, thereby providing a way to evaluate the overload capacity performance of the full half-bridge hybrid MMC. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It represents the test platform that has been built.

[0023] Figure 2 It shows a flow chart of an overload capability evaluation method of a full half-bridge hybrid MMC. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific implementation processes. It should be emphasized that the specific implementation cases described herein are only used to explain the present invention and do not limit the scope of the present invention and its claims; for the convenience of description, some parts of the drawings may be omitted and the size may be changed, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures in the drawings and their descriptions are omitted.

[0025] Step 1: Build a full half-bridge hybrid MMC overload capacity test platform

[0026] An overload capacity test platform for a full-half-bridge hybrid MMC is constructed, comprising a test box (1), a full-half-bridge hybrid MMC (2), a heat sink performance test bench (3), a first temperature sensor (4), a second temperature sensor (5), a third temperature sensor (6), a fourth temperature sensor (7), a power analyzer (8), a test simulation power supply (9), a timing device (10), and a computer terminal (11), wherein:

[0027] The magnitude of the current of the test simulation power supply (9) is controlled by a computer terminal (11), and the test simulation power supply (9) supplies power to the full half-bridge hybrid MMC (2). The magnitude of the current is changed by the computer terminal (11) to simulate the overload condition of the full half-bridge hybrid MMC (2); the first temperature sensor (4) is placed below the full half-bridge hybrid MMC (2) to measure the temperature below, the second temperature sensor (5) is placed above the full half-bridge hybrid MMC (2) to measure the temperature above, the third temperature sensor (6) is placed on the right side of the full half-bridge hybrid MMC (2) to measure the temperature on the right side, and the fourth temperature sensor (7) is placed on the left side of the full half-bridge hybrid MMC (2) to measure the temperature on the left side. The temperature and heat sink performance test bench (3) are connected to four temperature sensors to obtain the heat dissipation evaluation factor of the full half-bridge hybrid MMC (2), and the heat dissipation evaluation factor is transmitted to the computer terminal (11); the power analyzer (8) is connected to the full half-bridge hybrid MMC (2) to measure the current, voltage and power of the full half-bridge hybrid MMC (2) under an overload state to obtain the power factor angle evaluation factor of the full half-bridge hybrid MMC (2), and the power factor angle evaluation factor is transmitted to the computer terminal (11); the timing device (10) is connected to the computer terminal (11) to record the operation time of the full half-bridge hybrid MMC (2) in the test box (1) under the overload condition;

[0028] Step 2: Calculate the heat dissipation evaluation factor of the full-half-bridge hybrid MMC under overload conditions

[0029] The current is increased through the computer terminal (11) so that the current in the full half-bridge hybrid MMC (2) reaches the rated current, which is recorded as I arm , in A, the running time of the full half-bridge hybrid MMC (2) is 1 min, at which time the temperature measured by the first temperature sensor (4) is recorded as T0, in °C, the temperature measured by the second temperature sensor (5) is recorded as T1, in °C, the temperature measured by the third temperature sensor (6) is recorded as T2, in °C, the temperature measured by the fourth temperature sensor (7) is recorded as T3, in °C, and the current of the computer terminal (11) is continuously increased to I armTo prevent the full half-bridge hybrid MMC (2) from being destroyed due to excessive current exceeding the rated current, the current is increased by 0.1 times I arm , the increase in current is 0.1I arm , 0.2I arm , 0.3I arm , 0.4I arm , 0.5I arm , the operation time of the full half-bridge hybrid MMC (2) at each current is still 1 minute, and the temperature measured by the first temperature sensor (4) is recorded as T ai The temperature measured by the second temperature sensor (5) is denoted as T bi The temperature measured by the third temperature sensor (6) is denoted as T ci The temperature measured by the fourth temperature sensor (7) is denoted as T di , where i = 1, 2, 3, 4, 5, and the above temperature units are all in ° C. The heat sink performance test bench (3) analyzes and calculates the temperature values ​​measured by the four temperature sensors;

[0030] The heat dissipation evaluation factor α under overload can be obtained by formula (1): s :

[0031]

[0032] Step 3: Calculate the power factor angle evaluation factor of the full-half-bridge hybrid MMC under overload conditions

[0033] The current is increased through the computer terminal (11) so that the current in the full half-bridge hybrid MMC (2) reaches the rated current, which is recorded as I arm , in A, the running time of the full half-bridge hybrid MMC (2) is 1 min, at which time the current value measured by the power analyzer (8) is I arm , in A, the voltage value measured by the power analyzer (8) is U smN , in V, the power value measured by the power analyzer (8) is P m , in W, continue to increase the current of the computer terminal (11), with I arm To prevent the full half-bridge hybrid MMC (2) from being destroyed due to excessive current exceeding the rated current, the current is increased by 0.1 times I arm , the increase in current is 0.1I arm , 0.2I arm , 0.3I arm , 0.4I arm , 0.5I armThe operation time of the full half-bridge hybrid MMC (2) at each current is still 1 min, and the current value measured by the power analyzer (8) is recorded as I i , the unit is A, and the voltage value measured by the power analyzer (8) is recorded as U i , in V, the power value measured by the power analyzer (8) is recorded as P i , the unit is W, where i=1, 2, 3, 4, 5, the power analyzer (8) analyzes and calculates the measured current, voltage and power data;

[0034] The power factor angle evaluation factor β under overload can be obtained by formula (2): j :

[0035]

[0036] Wherein f is the frequency of the test simulation power supply (9) and is 50 Hz;

[0037] Step 4: Calculate the overload capacity evaluation factor of the full half-bridge hybrid MMC

[0038] The overload capacity evaluation factor σ of the full half-bridge hybrid MMC is obtained by formula (3): g :

[0039]

[0040] Step 5: Evaluate the overload capability of the full-half-bridge hybrid MMC

[0041] The overload capacity of the full half-bridge hybrid MMC is evaluated by formula (3). If 1<σ g ≤1.18 indicates good overload capacity; if 1.18<σ g ≤1.28 indicates that the overload capacity is average; if σ g >1.28 indicates that the overload capacity is very poor, and the current in the full-half-bridge hybrid MMC needs to be adjusted to prevent internal failure of the full-half-bridge hybrid MMC under overload conditions, causing damage to the internal devices of the full-half-bridge hybrid MMC and rendering the full-half-bridge hybrid MMC unable to work normally.

Claims

1. A method for evaluating the overload capacity of a full-half-bridge hybrid MMC, characterized in that: The following steps are involved: Step 1: Build a full half-bridge hybrid MMC overload capacity test platform; Step 2: Calculate the heat dissipation evaluation factor of the full-half-bridge hybrid MMC under overload conditions; Step 3: Calculate the power factor angle evaluation factor of the full half-bridge hybrid MMC under overload condition; Step 4: Calculate the overload capacity evaluation factor of the full half-bridge hybrid MMC; Step 5: Evaluate the overload capability of the full-half-bridge hybrid MMC; The specific steps of the first step are as follows: An overload capacity test platform for a full-half-bridge hybrid MMC is constructed, comprising a test box (1), a full-half-bridge hybrid MMC (2), a heat sink performance test bench (3), a first temperature sensor (4), a second temperature sensor (5), a third temperature sensor (6), a fourth temperature sensor (7), a power analyzer (8), a test simulation power supply (9), a timing device (10), and a computer terminal (11), wherein: The magnitude of the current of the test simulation power supply (9) is controlled by a computer terminal (11), and the test simulation power supply (9) supplies power to the full half-bridge hybrid MMC (2). The magnitude of the current is changed by the computer terminal (11) to simulate the overload condition of the full half-bridge hybrid MMC (2); the first temperature sensor (4) is placed below the full half-bridge hybrid MMC (2) to measure the temperature below, the second temperature sensor (5) is placed above the full half-bridge hybrid MMC (2) to measure the temperature above, the third temperature sensor (6) is placed on the right side of the full half-bridge hybrid MMC (2) to measure the temperature on the right side, and the fourth temperature sensor (7) is placed on the left side of the full half-bridge hybrid MMC (2) to measure the temperature on the left side. The temperature and heat sink performance test bench (3) are connected to four temperature sensors to obtain the heat dissipation evaluation factor of the full half-bridge hybrid MMC (2), and the heat dissipation evaluation factor is transmitted to the computer terminal (11); the power analyzer (8) is connected to the full half-bridge hybrid MMC (2) to measure the current, voltage and power of the full half-bridge hybrid MMC (2) under an overload state to obtain the power factor angle evaluation factor of the full half-bridge hybrid MMC (2), and the power factor angle evaluation factor is transmitted to the computer terminal (11); the timing device (10) is connected to the computer terminal (11) to record the operation time of the full half-bridge hybrid MMC (2) in the test box (1) under the overload condition; The specific steps of the second step are as follows: The current is increased through the computer terminal (11) so that the current in the full half-bridge hybrid MMC (2) reaches the rated current, which is recorded as I arm , in A, the running time of the full half-bridge hybrid MMC (2) is 1 min, at which time the temperature measured by the first temperature sensor (4) is recorded as T0, in °C, the temperature measured by the second temperature sensor (5) is recorded as T1, in °C, the temperature measured by the third temperature sensor (6) is recorded as T2, in °C, the temperature measured by the fourth temperature sensor (7) is recorded as T3, in °C, and the current of the computer terminal (11) is continuously increased to I arm To prevent the full half-bridge hybrid MMC (2) from being destroyed due to excessive current exceeding the rated current, the current is increased by 0.1 times I arm , the increase in current is 0.1I arm , 0.2I arm , 0.3I arm , 0.4I arm , 0.5I arm , the operation time of the full half-bridge hybrid MMC (2) at each current is still 1 minute, and the temperature measured by the first temperature sensor (4) is recorded as T ai The temperature measured by the second temperature sensor (5) is denoted as T bi The temperature measured by the third temperature sensor (6) is denoted as T ci The temperature measured by the fourth temperature sensor (7) is denoted as T di , where i = 1, 2, 3, 4, 5, and the above temperature units are all in ° C. The heat sink performance test bench (3) analyzes and calculates the temperature values ​​measured by the four temperature sensors; The heat dissipation evaluation factor α under overload can be obtained by formula (1): s : The specific steps of the third step are as follows: The current is increased through the computer terminal (11) so that the current in the full half-bridge hybrid MMC (2) reaches the rated current, which is recorded as I arm , in A, the running time of the full half-bridge hybrid MMC (2) is 1 min, at which time the current value measured by the power analyzer (8) is I arm , in A, the voltage value measured by the power analyzer (8) is U smN , in V, the power value measured by the power analyzer (8) is P m , in W, continue to increase the current of the computer terminal (11), with I arm To prevent the full half-bridge hybrid MMC (2) from being destroyed due to excessive current exceeding the rated current, the current is increased by 0.1 times I arm , the increase in current is 0.1I arm , 0.2I arm , 0.3I arm , 0.4I arm , 0.5I arm The operation time of the full half-bridge hybrid MMC (2) at each current is still 1 min, and the current value measured by the power analyzer (8) is recorded as I i , the unit is A, and the voltage value measured by the power analyzer (8) is recorded as U i , in V, the power value measured by the power analyzer (8) is recorded as P i , the unit is W, where i=1, 2, 3, 4, 5, the power analyzer (8) analyzes and calculates the measured current, voltage and power data; The power factor angle evaluation factor β under overload can be obtained by formula (2): j : Wherein f is the frequency of the test simulation power supply (9) and is 50 Hz; The specific steps of the fourth step are as follows: The overload capacity evaluation factor σ of the full half-bridge hybrid MMC is obtained by formula (3): g : The specific steps of the fifth step are as follows: The overload capacity of the full half-bridge hybrid MMC is evaluated by formula (3). If 1<σ g ≤1.18 indicates good overload capacity; if 1.18<σ g ≤1.28 indicates that the overload capacity is average; if σ g >1.28 indicates that the overload capacity is very poor, and the current in the full-half-bridge hybrid MMC needs to be adjusted to prevent internal failure of the full-half-bridge hybrid MMC under overload conditions, causing damage to the internal devices of the full-half-bridge hybrid MMC and rendering the full-half-bridge hybrid MMC unable to work normally.

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