## 4 Voltage Vector Distribution Method
### Voltage Vector Distribution Method Selection Strategy  
Each of these three voltage vector distribution methods introduced above has worked out a result to distribute voltage vectors generated by dual inverter to synthesize the desired stator voltage vector of OW-PMSM. The voltage vector distribution method selection strategy deals with the results from these voltage vector distribution methods by selecting the optimal one as the final result of voltage vector distribution.  
The general idea of this selection strategy is expounded as follow. We have three evaluation indexes, which are the accurate synthesizing of desired stator voltage vector, the following of inverter1's desired output power in acceptable accuracy, and the reduction of inverter switching frequency, ranked from highest priority to lowest. In other words, by priority, first we need to ensure the voltage vector distribution result can generate the desired stator voltage vector or as integrally as possible. Based on that, we try to make inverter1's output power follow the desired value in a specific tolerance range. After these two conditions are met, we can think about lowering the inverter switching frequency. The best situation is these three conditions are all satisfied. Otherwise, we discard the reduction of inverter switching frequency. Then we give up the accurate power following of inverter1. At least the synthesizing of desired voltage vector has to be ensured.  
For the second condition mentioned above, we need to define the inverter1's maximum power following deviation, denoted by \(D_{Pinv1\_\_\_\_\_}\). If inverter1's output power is within the range of \([P^{*}_{imv1\_\_\_}-D_{Pinv1\_\_\_},P^{*}_{imv1\_\_\_}+D_{Pinv1\_\_\_\_}]\), we consider inverter1's output power is following the desired  
Figure 8: Voltage vector distribution examples of linear partition method.  
value within tolerance range. \(D_{Pinv1\_\text{max}}\) can be adjusted according to the control requirements of the primary power source.  
The specific algorithm of this selection strategy will be introduced as follow. First, the flag of low switching frequency method \(F_{LF}\) is checked. If \(F_{LF}=1\), meaning the low switching frequency method is available, the selection will be made between the low switching frequency method and the accurate power following method. Then three conditions are checked, which are \(F_{AF}=0\), \(D_{Pinv1\_LF}\leq D_{Pinv1\_AF}\), and \(D_{Pinv1\_LF}\leq D_{Pinv1\_\text{max}}\). If anyone of these conditions is met, indicating the low switching frequency method meets inverter1's accurate power following condition or has a better performance in inverter1's power following, the low switching frequency method will be selected. If all these three conditions are not met, the accurate power following method will be selected. However, if \(F_{LF}=0\), meaning the low switching frequency method is invalid in current situation, the selection will have to be made between the accurate power following method and the linear partition method. When \(F_{AF}=1\) and \(D_{Pinv1\_AF}\leq D_{Pinv1\_LP}\) are both met, indicating the accurate power following method is available and performs better in inverter1's power following, the accurate power following method will be selected. Otherwise, the linear partition method will be selected to synthesize the desired stator voltage vector as integrally as possible. The flowchart of the voltage vector distribution method selection strategy is shown in Figure 9.