Electromagnet drive control method, device and hybrid automatic transfer switch

Abstract

The present invention discloses an electromagnet drive control method. Starting at time t0, when the electromagnet's DC drive power supply is turned on, the electromagnet's magnetic flux Ψ is observed in real time based on the DC drive power supply voltage. At any time t1 before reaching a preset time t2, the electromagnet's magnetic flux integral value from t0 to t1 is calculated in real time, and the magnetic flux integral value from t1 to t2 is predicted, thereby obtaining an estimated magnetic flux integral value from t0 to t2. If the estimated magnetic flux integral value is greater than or equal to a preset magnetic flux integral threshold, the electromagnet's DC drive power supply is immediately shut off. Otherwise, the electromagnet's DC drive power supply is shut off at time t2. The present invention also discloses an electromagnet drive control device and a hybrid automatic transfer switch. Compared to existing technologies, the present invention can effectively reduce the hardware circuit complexity, system cost, and volume while maintaining the performance of the hybrid automatic transfer switch.

Description

Technical Field

[0001] The invention relates to an electromagnet drive control method. Background Art

[0002] In some emergency power supply systems, continuous and reliable load operation must be ensured, and the interruption time requirement is relatively high, generally less than 10ms. However, the switching time of traditional mechanical automatic transfer switching equipment (ATSE) is usually designed to be 30ms or longer. When the working power supply is abnormal, the load will be interrupted during the switch to the backup power supply, which makes it difficult to meet application requirements.

[0003] To this end, solutions such as static transfer switches (STS) and hybrid automatic transfer switches have been proposed to achieve seamless switching between working and backup power sources, with load interruption times of ≤4ms, meeting the requirements of emergency power supply systems for critical loads such as those in healthcare, finance, communications, airports, banks, data centers, and military facilities. While STS products offer short switching times, they suffer from high conduction losses during normal operation. Hybrid automatic transfer switches (such as the dual power automatic transfer device disclosed in Chinese invention patent CN105024450B) conduct power through a mechanical transfer switch during normal operation, resulting in lower conduction losses. During the power conversion period, an auxiliary power supply circuit composed of power electronics provides short-term power to the load, compensating for the 30ms or longer interruption time of the mechanical switch. These switches combine the advantages of low conduction losses of traditional mechanical transfer switches with the short switching time of static transfer switches.

[0004] The mechanical transfer switch of the existing hybrid automatic transfer switch is usually driven by an electromagnet, which requires a rated power drive power supply to drive the electromagnet. This increases the complexity of the hardware circuit on the one hand and increases the system cost and product size on the other. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the existing technology and provide an electromagnet drive control method and device, which can effectively reduce the complexity of the hardware circuit and the system cost and volume while ensuring the performance of the hybrid automatic transfer switch.

[0006] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0007] A method for controlling an electromagnet drive comprises: starting from time t0 when a DC drive power supply of the electromagnet is turned on, observing the flux linkage Ψ of the electromagnet in real time according to the voltage of the DC drive power supply; at any time t1 before reaching a preset time t2, calculating in real time the flux linkage integral value of the electromagnet during the period t0 to t1 and predicting the flux linkage integral value during the period t1 to t2, thereby obtaining an estimated flux linkage integral value during the period t0 to t2; if the estimated flux linkage integral value is greater than or equal to a preset flux linkage integral threshold, immediately shutting off the DC drive power supply of the electromagnet; otherwise, shutting off the DC drive power supply of the electromagnet at time t2.

[0008] Preferably, the magnetic flux Ψ of the electromagnet is observed in real time according to the following formula:

[0009] Ψ(n)=Coef LR (U(n)Ts+Ψ(n-1))

[0010] Among them, Ψ(n) is the flux observation value at the current moment, Ψ(n-1) is the flux observation value at the last interruption moment, Ts is the interruption period, U(n) is the DC drive power supply voltage value sampled at the current moment, and the coefficient L and R are the equivalent inductance and equivalent internal resistance of the electromagnet coil respectively.

[0011] More preferably, the magnetic flux integral value of the electromagnet during t0 to t1 is calculated according to the following formula:

[0012]

[0013] is the integral value of the magnetic flux at the last interruption moment.

[0014] More preferably, the flux integral value during t1 to t2 is predicted according to the following formula:

[0015]

[0016] Where m = (t2-t1) / ΔT, ΔT is the length of the time slice divided during discrete calculation.

[0017] An electromagnet drive control device, comprising:

[0018] A switch module, used to switch on or off the DC drive power supply of the electromagnet;

[0019] a flux linkage observer for observing the flux linkage Ψ of the electromagnet in real time according to the voltage of the DC drive power supply, starting from time t0 when the DC drive power supply of the electromagnet is turned on;

[0020] The flux integral estimation module is used to calculate the flux integral value of the electromagnet during the period t0 to t1 in real time at any time t1 before reaching the preset time t2, and predict the flux integral value during the period t1 to t2, thereby obtaining the flux integral estimation value during the period t0 to t2;

[0021] The judgment module is used to judge whether the flux integral estimation value is greater than or equal to a preset flux integral threshold value. If so, the switch module is immediately controlled to be turned off; otherwise, the switch module is controlled to be turned off at time t2.

[0022] Preferably, the flux observer observes the flux Ψ of the electromagnet in real time according to the following formula:

[0023] Ψ(n)=Coef LR (U(n)Ts+Ψ(n-1))

[0024] Among them, Ψ(n) is the flux observation value at the current moment, Ψ(n-1) is the flux observation value at the last interruption moment, Ts is the interruption period, U(n) is the DC drive power supply voltage value sampled at the current moment, and the coefficient L and R are the equivalent inductance and equivalent internal resistance of the electromagnet coil respectively.

[0025] Further preferably, the flux integral estimation module calculates the flux integral value of the electromagnet during t0-t1 according to the following formula:

[0026]

[0027] is the integral value of the magnetic flux at the last interruption moment.

[0028] Further preferably, the flux integral estimation module predicts the flux integral value during t1 to t2 according to the following formula:

[0029]

[0030] Where m = (t2-t1) / ΔT, ΔT is the length of the time slice divided during discrete calculation.

[0031] Based on the above technical solution, we can also obtain:

[0032] A hybrid automatic transfer switch comprises a mechanical transfer switch driven by an electromagnet and an auxiliary power supply circuit composed of a power electronic device. The auxiliary power supply circuit is used to provide short-term power to a load during the transfer period of the mechanical transfer switch. The electromagnet uses the DC bus in the auxiliary power supply circuit as a DC drive power supply. The drive control device of the electromagnet is the electromagnet drive control device described in any of the above technical solutions.

[0033] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0034] The electromagnet drive control scheme proposed in this invention is based on the electromagnet flux linkage model. It controls the electromagnet drive according to the integral of the flux linkage with respect to time. Compared with the traditional fixed on-time control scheme, it can effectively solve the problem of large variations in driving effect caused by fluctuations in the driving power supply voltage.

[0035] The hybrid automatic transfer switch proposed in the present invention uses the DC bus in the auxiliary power supply circuit as the DC driving power supply for the mechanical transfer switch electromagnet, and adopts the above-mentioned electromagnet drive control scheme. While effectively reducing the complexity of the hardware circuit and the system cost and volume, it also solves the problem of load changes causing fluctuations in the driving power supply voltage, which in turn affects the power-off time of the load during the power conversion process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a control principle block diagram of the electromagnet drive control method of the present invention;

[0037] Figure 2 Schematic diagram of the relationship between electromagnet driving time and magnetic flux. DETAILED DESCRIPTION

[0038] In response to the hardware circuit complexity, system cost and volume problems caused by the need for a dedicated electromagnet control power supply in existing hybrid automatic transfer switches, the solution of the present invention is to eliminate the additional electromagnet drive power supply and directly use the DC bus in the auxiliary power supply circuit as the DC drive power supply for the mechanical transfer switch electromagnet, thereby reducing the hardware circuit complexity, system cost and volume.

[0039] However, in practice, it was found that adopting this solution caused the DC bus voltage in the auxiliary power supply circuit to vary with the load. If the traditional fixed-time electromagnet drive method were used, bus voltage fluctuations would cause significant variations in the electromagnet drive effect, and the separation time of the moving and static contacts of the mechanical transfer switch would fluctuate significantly. Because the load remains rigidly connected to the abnormal power source via the mechanical transfer switch during the pre-separation phase, the load voltage is clamped. Due to output capacity limitations, the auxiliary power supply circuit is unable to quickly extinguish the arc and provide short-term energy to the load to ensure the load voltage remains within the normal range. Therefore, the load power interruption time is limited by the separation time. When the bus voltage is too low, the separation time is prolonged, and the load power interruption time is also prolonged, making it difficult to meet the application requirements of emergency power supply systems.

[0040] To solve the above problems, the present invention proposes an electromagnet drive control method, which is as follows:

[0041] Starting from time t0 when the DC drive power supply of the electromagnet is turned on, the magnetic flux Ψ of the electromagnet is observed in real time based on the DC drive power supply voltage. At any time t1 before reaching a preset time t2, the magnetic flux integral value of the electromagnet during the period t0 to t1 is calculated in real time, and the magnetic flux integral value during the period t1 to t2 is predicted, thereby obtaining an estimated magnetic flux integral value during the period t0 to t2. If the estimated magnetic flux integral value is greater than or equal to a preset magnetic flux integral threshold, the DC drive power supply of the electromagnet is immediately turned off. Otherwise, the DC drive power supply of the electromagnet is turned off at time t2.

[0042] An electromagnet drive control device, comprising:

[0043] A switch module, used to switch on or off the DC drive power supply of the electromagnet;

[0044] a flux linkage observer for observing the flux linkage Ψ of the electromagnet in real time according to the voltage of the DC drive power supply, starting from time t0 when the DC drive power supply of the electromagnet is turned on;

[0045] The flux integral estimation module is used to calculate the flux integral value of the electromagnet during the period t0 to t1 in real time at any time t1 before reaching the preset time t2, and predict the flux integral value during the period t1 to t2, thereby obtaining the flux integral estimation value during the period t0 to t2;

[0046] The judgment module is used to judge whether the flux integral estimation value is greater than or equal to a preset flux integral threshold value. If so, the switch module is immediately controlled to be turned off; otherwise, the switch module is controlled to be turned off at time t2.

[0047] The above-mentioned electromagnet control scheme is suitable for applications where the voltage fluctuation of the DC driving power supply is large, and can maintain the basic stability of the driving effect under the condition of large fluctuation of the driving power supply voltage.

[0048] To facilitate public understanding, the following takes the electromagnet drive of the mechanical transfer switch in the hybrid automatic transfer switch as an example and describes the technical solution of the present invention in detail with reference to the accompanying drawings:

[0049] The hybrid automatic transfer switch of this embodiment includes a mechanical transfer switch driven by an electromagnet and an auxiliary power supply circuit composed of a power electronic device. The auxiliary power supply circuit is used to provide short-term power to the load during the transfer period of the mechanical transfer switch. The auxiliary power supply circuit extracts electrical energy from the main power supply and / or the backup power supply, converts it into direct current through a rectifier circuit, and then supplies power to the load through an inverter unit during the transfer period of the mechanical transfer switch.

[0050] like Figure 1As shown, the DC power supply of the electromagnet coil of the mechanical transfer switch is taken from the DC bus in the auxiliary power supply circuit, and its voltage sampling also uses the voltage sampling signal of the DC bus in the auxiliary power supply circuit; the drive switch S is a static switch with fast response.

[0051] When the working power supply for the load has an abnormality, the hybrid automatic transfer switch will immediately conduct the drive switch S, causing the mechanical transfer switch to switch to the standby power supply. At the same time, it supplies energy to the load through the auxiliary power supply circuit for a short time to ensure the continuous and reliable operation of the load during the conversion. The short-time energy supply method of the auxiliary power supply circuit is to rectify from the main and / or standby power supply to the DC bus, and then invert to supply energy to the load. Therefore, during the conduction of the electromagnet drive switch S, the DC bus of the auxiliary power supply circuit not only supplies energy to the load but also supplies energy to the electromagnet coil. The DC bus voltage is affected by the load weight. Under the traditional fixed-time drive scheme of the electromagnet, the bus voltage fluctuation will cause the fluctuation of the electromagnet drive effect, and may even cause abnormal problems such as the mechanical transfer switch not closing in place.

[0052] To solve this problem, the present invention proposes an electromagnet drive control scheme based on flux linkage observation, which can ensure that the opening times of the moving and static contacts of the mechanical transfer switch are basically the same. As Figure 1 shown, the drive control process is specifically as follows:

[0053] S1. When the drive signal is received at time t0, immediately conduct the electromagnet drive switch S;

[0054] S2. At the current time t1 (t1 < t2, t2 is the preset ideal separation time of the moving and static contacts of the mechanical transfer switch), by sampling the DC drive power supply voltage signal U, based on the electromagnet coil model, the real-time flux linkage Ψ is observed, and the flux linkage integral value during t0~t1 is calculated and assume that the electromagnet drive switch S is disconnected at time t1, and predict the flux linkage integral value during t1~t2 and then obtain the estimated value of the flux linkage integral during t0~t2

[0055] According to the real-time sampled U, discrete using the Euler method can obtain:

[0056] Ψ(n) = Coef LR (U(n)Ts + Ψ(n - 1))

[0057] where, Ψ(n) is the flux linkage observation value at the current time, Ψ(n - 1) is the flux linkage observation value at the previous interruption time, Ts is the interruption period, U(n) is the DC drive power supply voltage value sampled at the current time, and the coefficient L and R are the equivalent inductance and equivalent internal resistance of the electromagnet coil, respectively. In this case, even at the maximum drive current at time t1, it is still less than the saturation current of the electromagnet coil. The inductance is in the linear region throughout the entire period, so its inductance value L can be used as a constant. If the drive current exceeds the coil saturation current and enters the nonlinear region, it can be corrected using the nonlinear compensation coefficient to obtain a more accurate flux linkage observation value Ψ(n).

[0058] The integral value of magnetic flux during t0 to t1 It can be obtained according to the following formula:

[0059]

[0060] in is the integral value of the magnetic flux at the last interruption moment.

[0061] Assume that the electromagnetic drive switch S is disconnected at the current time t1, and predict the flux integral value during t1 to t2

[0062]

[0063] Where m = (t2-t1) / ΔT, ΔT is the length of the time slice divided during discrete calculation. To save chip resources while taking into account calculation accuracy, m = 2 and ΔT = (t2-t1) / 2 are preferably used in this case.

[0064] Based on this, we get Figure 2 The drive switch S is turned on before the current t1, and the drive switch S is disconnected after t1. The estimated value of the flux integral from the drive trigger t0 to the separation of the moving and static contacts of the mechanical transfer switch at t2 is shown.

[0065]

[0066] S3, the estimated value of the flux integral when the drive switch S is turned off at time t1 and the preset flux integration threshold Coef ΨT Comparison (Coef ΨT This value can be obtained by testing under no-load conditions and standard power supply conditions. Under this value, the switching characteristics of the mechanical switch are relatively ideal):

[0067] when When , it is considered that the drive is in place, and the drive switch S is turned off;

[0068] when When , it is considered that the drive has not yet reached the designated position, and the drive switch S is kept on.

[0069] If the bus voltage is too low and the drive is still not in place at time t2, it is considered an abnormal situation and the drive switch S is directly disconnected to stop the electromagnet drive.

[0070] In summary, the hybrid automatic transfer switch proposed in the present invention ensures the consistency of transfer characteristics while not requiring an additional electromagnet drive power supply with matching rated power, resulting in low hardware design cost and small system size.

Claims

1. A method for controlling an electromagnet drive, characterized in that: Starting from time t0 when the DC drive power supply of the electromagnet is turned on, the flux linkage Ψ of the electromagnet is observed in real time based on the voltage of the DC drive power supply. At any time t1 before reaching a preset time t2, the flux linkage integral value of the electromagnet during the period t0 to t1 is calculated in real time and the flux linkage integral value during the period t1 to t2 is predicted, thereby obtaining an estimated flux linkage integral value during the period t0 to t2. If the estimated flux linkage integral value is greater than or equal to a preset flux linkage integral threshold, the DC drive power supply of the electromagnet is immediately turned off. Otherwise, the DC drive power supply of the electromagnet is turned off at time t2. The flux linkage Ψ of the electromagnet is observed in real time based on the following formula: Ψ(n)=Coef LR (U(n)Ts+Ψ(n-1)) Among them, Ψ(n) is the flux observation value at the current moment, Ψ(n-1) is the flux observation value at the last interruption moment, Ts is the interruption period, U(n) is the DC drive power supply voltage value sampled at the current moment, and the coefficient L and R are the equivalent inductance and equivalent internal resistance of the electromagnet coil respectively; The flux integral value during t1 to t2 is predicted according to the following formula: Where m = (t2-t1) / ΔT, ΔT is the length of the time slice divided during discrete calculation.

2. The electromagnet drive control method according to claim 1, wherein: Calculate the integral value of the magnetic flux of the electromagnet during t0~t1 according to the following formula: is the integral value of the magnetic flux at the last interruption moment.

3. An electromagnet drive control device, characterized in that: include: A switch module, used to switch on or off the DC drive power supply of the electromagnet; The flux observer is used to observe the flux linkage Ψ of the electromagnet in real time according to the voltage of the DC drive power supply starting from the time t0 when the DC drive power supply of the electromagnet is turned on. The flux observer observes the flux linkage Ψ of the electromagnet in real time according to the following formula: Ψ(n)=Coef LR (U(n)Ts+Ψ(n-1)) Among them, Ψ(n) is the flux observation value at the current moment, Ψ(n-1) is the flux observation value at the last interruption moment, Ts is the interruption period, U(n) is the DC drive power supply voltage value sampled at the current moment, and the coefficient L and R are the equivalent inductance and equivalent internal resistance of the electromagnet coil respectively; The flux integral estimation module is used to calculate the flux integral value of the electromagnet during the period t0 to t1 in real time at any time t1 before the preset time t2 is reached, and predict the flux integral value during the period t1 to t2, thereby obtaining the flux integral estimation value during the period t0 to t2; the flux integral estimation module predicts the flux integral value during the period t1 to t2 according to the following formula Where m = (t2-t1) / ΔT, ΔT is the length of the time slice divided during discrete calculation; The judgment module is used to judge whether the flux integral estimation value is greater than or equal to a preset flux integral threshold value. If so, the switch module is immediately controlled to be turned off; otherwise, the switch module is controlled to be turned off at time t2.

4. The electromagnet drive control device according to claim 3, characterized in that: The flux integral estimation module calculates the flux integral value of the electromagnet during t0~t1 according to the following formula: is the integral value of the magnetic flux at the last interruption moment.

5. A hybrid automatic transfer switch comprising a mechanical transfer switch driven by an electromagnet and an auxiliary power supply circuit composed of a power electronic device, wherein the auxiliary power supply circuit is used to supply power to a load for a short period of time during the transfer period of the mechanical transfer switch, characterized in that: The electromagnet uses the DC bus in the auxiliary power supply circuit as a DC driving power supply; the driving control device of the electromagnet is the electromagnet driving control device according to claim 3 or 4.

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