Study on AC voltage stabilization power supply loss and energy saving

　　1 Introduction

　　As an important part of AC power supply system, AC voltage stabilizer has been widely used. It can not only stabilize voltage and improve power supply quality, but also effectively protect load, prolong equipment life and help users manage power supply. However, the loss of voltage stabilizer itself has also attracted people's attention. How to combine voltage stabilization with energy saving is an important research topic for power supply workers.

　　2 Loss analysis of AC regulated power supply

　　As a power distribution device, AC regulated power supply has its own loss problem during operation. Due to different voltage stabilization principles and different quality of regulated power supplies from different manufacturers, this loss varies greatly, among which the loss of auto-coupling voltage-regulated regulated power supply is relatively small. This paper makes a preliminary analysis of the loss problem of auto-coupling voltage-regulated regulated power supply in actual work.

　　In many places where voltage stabilizers are installed, voltage stabilizers are often used as power supply equipment for local loads, making them work 24 hours a day. However, the average working time of most loads is about 5h to 8h a day, and the remaining 16h to 19h voltage stabilizers are in no-load state, so the power supply has a long no-load loss. On the other hand, in the process of voltage stabilizers working with loads, as the total load of the power grid changes, the grid voltage will also vary in different periods of time. There must be a period of time when the grid voltage meets the power requirements of the equipment (generally 220V ± 10%), and the voltage stabilizer is still working at this time. This is also an unnecessary loss, causing energy waste. This situation is reflected differently in different regions and at different times. It is assumed that half of the time during the 5h to 8h of load working is that the grid voltage meets the rated working voltage requirements of the load. Based on this assumption, combined with the rated performance data of the contact automatic voltage regulator of the mechanical industry standard ZBK42002-87, the loss of the auto-voltage stabilizer is estimated, as shown in Table 1 and Table 2.

　　Table 1 Loss estimation of auto-regulator (load works 5 hours per day)

　　Table 2 Estimated loss of auto-regulator (load works 8 hours a day)

　　The "Excess Loss" column in the power table is the sum of the power loss and no-load loss when the load is working and the city power is basically normal. The "Proportion" column is the percentage of excess loss in the total loss, and the "Annual Power Consumption" column is the power consumed by unnecessary excess loss in one year. It can be seen from the table that among the losses of various power auto-coupling voltage-stabilized power supplies, unnecessary "excess loss" accounts for more than 64% of the total energy consumption, while the annual excess power loss is from several hundred to thousands (kW·h), which shows that this unnecessary power loss is quite large. The above is still the power loss estimate of the high-efficiency auto-coupling voltage-regulated voltage-stabilized power supply. For other low-efficiency voltage-stabilized power supplies, their losses are several to dozens of times the above data, and the waste of power is quite amazing. Therefore, how to reduce "excess loss" is the key to energy saving of AC voltage-stabilized power supplies. For this reason, it is necessary to evaluate and improve the performance of the current voltage-stabilized power supply so as to minimize the loss of power in the voltage-stabilization process to achieve the purpose of saving resources and protecting the environment.

　　3 Research on energy saving of AC regulated power supply

　　AC regulated power supplies are favored by users for their characteristics of voltage stabilization and effective protection of electrical equipment. If the regulated power supply can automatically enter the "sleep" state to save energy when the load is not working and the AC power supply is normal, it will become a truly energy-saving AC regulated power supply.

　　3.1 Energy-saving principle of AC regulated power supply

　　According to the above concept, for the auto-coupling voltage-regulating regulated power supply, its voltage stabilization and energy-saving working principle is shown in Figure 1.

　　Figure 1 AC regulated power supply energy saving principle diagram

　　The solid line part in the figure is the principle block diagram of the common auto-coupling voltage-regulated power supply, and the dotted line part is the control circuit added to achieve energy saving. Under the action of the dotted line part in the block diagram, when the load is not working or the load is working and the main power supply is normal, the voltage-regulated power supply is in a "sleeping" energy-saving working state. At this time, the main voltage-regulated voltage-regulated channel consumes almost no power, thus achieving the purpose of energy saving and environmental protection. 　　3.2 Analysis of typical energy-saving circuits of AC voltage-regulated power supply

　　From the above analysis of the energy-saving principle of AC regulated power supply, it can be known that in order to achieve the purpose of energy saving, the easiest and most achievable method is to add a direct bypass channel to the regulated power supply, as shown in Figure 2. When the load of the regulated power supply is not working or the mains is normal, the energy-saving control circuit disconnects S1 and S2, connects S3, switches to the mains direct state, and makes the regulated main circuit consume no power. When the load is working and the grid voltage is abnormal (for example, greater than 242V or less than 198V), S3 is disconnected, S1 and S2 are connected, and the voltage is stabilized. This method is applicable to almost all regulated power supplies. But it has two obvious disadvantages:

　　(1) There is a momentary power outage during the conversion process between AC power direct connection and voltage regulation;

　　(2) When the load power is large, S1, S2 and S3 used for conversion require the use of large-current switches (such as AC contactors, etc.), which increases the cost of the entire machine.

　　Figure 2 Bypass circuit diagram

　　In order to overcome the shortcomings of the above scheme, there is a better solution for the auto-coupling voltage-regulated power supply, as shown in Figure 3. When voltage regulation is required, S is turned on and the circuit enters the normal voltage regulation state; when the load is not working or the mains is normal, the control circuit controls the carbon brush A to move to the fixed point B, and then disconnects S, and the mains is directly connected to the B-A point. At this time, the auto-coupling voltage regulator does not consume power, which can achieve the purpose of energy saving. Since the current flowing through S when no-load and load is much smaller than the rated current of the whole machine, S can use a very small current switch, and there will be no instantaneous power failure during the direct connection and voltage regulation conversion, which is a more ideal implementation method.

　　Figure 3 Auto-coupling voltage regulation improvement scheme

　　3.3 Application

　　Based on the experience of producing voltage stabilized power supplies for many years, the Electrical Equipment Factory of Zhongshan University has developed an energy-saving voltage stabilized power supply product with "empty loss" according to the above energy-saving principle. After replacing the ordinary voltage stabilized power supply with the energy-saving voltage stabilized power supply, the energy saving is more than 65%, and the effect is very significant. It is believed that after further improvement and promotion and application, it will achieve good social and economic benefits and contribute to my country's energy conservation and environmental protection cause.